Oral History Transcript — Dr. Wolfgang Gentner
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Wolfgang Gentner; November 15, 1971
ABSTRACT: Early education; studies biophysics at Universitat Frankfurt and Kaiser-Wilhelm Institut (Fredrich Dessauer, Rievsky); physics training (Erwin Madelung, Meissner); Dessauer’s political troubles. Fellowship to Institut Radium (Marie Curie), 1933; building geiger counters (Frederic Joliot-Curie); life and staff at Institut (Irene Joliot-Curie, Jean Perrin, Hans von Halban, Peter Preiswerk, Lew Kowarski, Rosenblum); Institut’s role in development of nuclear physics conference in Zurich (Paul Scherrer), 1933; London Conference of 1934 (Max Born, Maurice Goldhaber); F. Joliot-Curie thinking about accelerators and about building a cyclotron (Pierre Weiss); Gentner continues gamma ray work (Lise Meitner). Gentner leaves Institut after Curie’s death; fellowship at Institute for Medical Research, Kaiser-Wilhelm Institut, Heidelberg (Walther Bothe), 1935-1938; also lectures at Frankfurt on radioactivity, gamma rays, x-rays, and cosmic rays; builds the first Van de Graaff machine in Germany, 1936; first to use gamma rays to look for nuclear photo effect (Fowler, Lauritsen). Travels to United States to study cyclotrons (James Fisk), 1938; spends several months at University of California, Berkeley (E. O. Lawrence, Donald Cooksey); the fission story (Niels Bohr, J. R. Oppenheimer); calibrating ionization chamber and experimental work in fission; life and pre-war politics at Berkeley and Stanford University (Felix Bloch); visits California Institute of Technology (Fowler, Lauritsen, Max Delbruck); travels to Washington D.C. (George Gamow, Edward Teller, Fleming, Merle Tuve); and ends tour in New York City (John R. Dunning, Lawrence, Bohr). Returns to Europe; visits John Cockcroft at University of Cambridge. Returns with wife to Germany in April, 1938; plans for Siemens to build cyclotron in Heidelberg cancelled. Sent to Paris to interview F. Joliot-Curie on whereabouts of heavy water, July 1940; private meeting afterwards; works in Paris with F. Joliot-Curie on cyclotron, 1940-1942; returns to Heidelberg to build own cyclotron, 1942-1944. Difficulties of re-establishing nuclear physics in Germany after World War II (Cockcroft, Konrad Adenauer); building up new laboratories; CERN, DESY.
Weiner:The only information I know of which takes you back to a much earlier period is that you got your PhD at the University of Frankfurt in 1930.
Gentner:‘30, yes, end of ‘30, I think in November, ‘30.
Weiner:I wanted to ask if you could give me a brief background description of how you got to that point, — that’s always of interest to me, to know something of a person’s family life and background and how you ended up in physics with a PhD, how you first became interested in science, how you settled on physics, that kind of background I think is of interest.
Gentner:I think I was educated in Frankfurt in what you call in Germany the Gymnasium, which means I was in the Gymnasium to learn Latin and Greek, so usually these kind of people do other things than study physics, but we had a very good teacher in physics in this school. I was especially interested in physics and chemistry always and had a little lab at home, things like this that I could have at home, so I was always doing in the school already little experiments. I went over to the school — there were I think only 12 in the class — so we had a very good contact with our teachers, and especially good contact with the teacher in physics and chemistry. I went to him often in the afternoon. So when I went to the university I thought I should do the same as he did, almost the same, and there was some from industry, an engineer. He more directed me to go into engineering and things like this.
Weiner:By director, I don’t know exactly the term, the owner?
Gentner:No, not owner, what you call this here —
Weiner:Kind of a corporation?
Gentner:Corporation, yes. There’s no owner. Like here, a big chemical industry — the big industry in Germany is always old I don’t know the term to translate it.
Weiner:Some kind of holding company. I don’t know the exact word, but I know what you mean. He was in charge of one department of this?
Weiner:And he was a trained engineer?
Gentner:Yes. So I started physics, and after some time, I was a little changing, physics, then physical chemistry, chemistry and all this field. Finally I was, there was a new office at [?] by my father. My father was a new professor there, so one day I went to him and I asked him if I could perhaps do my studying at his institute, and he accepted me as a PhD thesis. He worked in biophysics. A man in biophysics. So I went — was interested more in biology and biophysics, and did my doctorate. My first publication is I think was radiation effects on … and the radiation on skin and chemical substances and so on. So I worked in the biological field in this time, radiation or cathode rays. I built an instrument for cathode rays, going out in the air to irradiate things, what you do today and so forth, in this field of radiation chemistry. But I did this with biological substances, and I worked for a few years in biology with Rievsky in this field of effect of X-rays mainly. And ultraviolet. The later, this was two years after my doctor’s degree, I worked here in the institute with Professor Dessauer and Rievsky who became quite well known later as a biophysicist.
Weiner:What was the title of the dissertation?
Gentner:It was on the effects of cathode rays on biological substances, something like this.
Weiner:Direct and to the point. How much physics was involved in it, in terms of the building of the instrument?
Gentner:Physics, yes. You see, the whole — I measured the angle of the cathode rays at this time, and then used this, also, I used special lenses, magnetic lenses to concentrate the cathode rays at one point, and I think I did in this time the first lens, I used the first magnetic lens to focus cathode rays outside the tube for biological purposes, and produced an ion field around, to concentrate the magnetic field, you get a quick focus and things like that. This was not true physics. In this institute, there was a mixture of physicists — I guess I was a physicist — but half the people working here were medical, in biology. So it was a mixture of those and chemists also. It was already a mixture of different people at the Institute.
Weiner:What about, during this period, training in physics itself, in the main body of physics knowledge? Did that continue or had you already gone through all that prior to?
Gentner:It had to do, the main things, before, but still I went to lessons.
Weiner:You were talking about the lectures, the courses that you continued to take. Did you get theory as well as experimental physics?
Gentner:Yes. You see, I did my doctor’s degree in physics, and if you do the doctor’s degree in physics, you have to pass an examination in experimental physics, theoretical physics, and something else, what you like — you can take some chemistry or physical chemistry or something like this. So altogether you have to give four, in this time, you have to give four fields, and two were experimental physics and theoretical physics always; Mathematics, chemistry, physical chemistry.
Weiner:On theoretical, what kinds of lectures did you attend and what was the subject matter? Was it quantum mechanics, for example?
Gentner:Yes, at this time it was certainly starting, but — yes, certainly earlier, but still in this time there was not too much examination in this field. You had lectures, but mainly on classical mechanics, and then —
Weiner:We were talking about theoretical courses and you said they were more on the classical —
Weiner:Who were the main stars in the field of theory?
Gentner:Madelung. He was my teacher in theoretical physics in Frankfurt. He was a very good man in theory. He still is living.
Gentner:Yes. He’s over 80 years, nearly 90.
Weiner:Where does he live?
Gentner:Frankfurt. Still there. He’s professor in —
Weiner:And the experimental work?
Gentner:Experimental physics was Meissner, who left Germany for the United States. He did my examination in experimental physics.
Weiner:Madelung in theory, Meissner in experimental — what other fields did you take?
Gentner:And physical chemistry.
Weiner:Who was that?
Gentner:In this time was, before was Lohen, but another — Lawrence, I think. Much later there at Frankfurt. He was there later in Gottingen.
Weiner:And then your fourth field was what?
Gentner:Yes, it is perhaps, I was in this time interested in philosophy and psychology, and so just because I did some courses in this field, I took as a fourth field philosophy and psychology. I was always interested in those things.
Weiner:Was that unusual?
Gentner:It was a little unusual, but it was allowed, because you could, in rural sciences you could always take philosophy and psychology as a fourth.
Weiner:Who was the examiner in that field?
Gentner:This was also somebody who had to leave Germany. It will come later, the name.
Weiner:Then after these examinations were done, you were working full time on your research?
Weiner:Did you have any duties at all, any assistant duties for which you were given some kind of stipend, while you were doing your own research?
Gentner:No, in this time until the end of my examinations, I didn’t get any money from the Institute, and I could only get money after my doctor’s degree. I was happy in the Institute. It was a private foundation, and they hadn’t much money. The university Institute, but at the same time a private foundation behind them, and they had always to pry out money and look about for money, and so they looked about, patents and things like this, X-ray field, and assistants had always to help to earn money for the Institute doing also work for industry, and working on things for X-rays, had all this connection with the X-ray industries. I remember also ultraviolet and so on, to build for the medical purposes, for using X-rays and ultraviolet rays, and in this field I worked also.
Weiner:To build the actual instruments that they would use, or to do some developmental work?
Gentner:The developmental and the work, and to try out the instruments. They’d send us the instrument — what you call this? You have, in the instrument you have the scale, you have to —
Weiner:— calibrate it.
Gentner:Calibrate the instrument. So the normal thing was to calibrate instruments coming from industry, and they got a certificate that this instrument has 1 or 2 on this and so on. We were also building instruments in our own workshop, in our own workshop we built instruments to measure X-rays for medical purposes. I think they didn’t get so much money — but so much money that we could pay the workshop partly with this.
Weiner:this on a contract basis?
Weiner:It wasn’t a question of someone making a donation and therefore you give thorn labor, but it was specific?
Gentner:No, a regular contract.
Weiner:What was the official title of Dessauer’s Institute?
Gentner:Institute for Physical Medicine. It was later changed the name, under Rievsky, the Institute was changed to Kaiser-Wilhelm Institute for Biophysik, and later to Biophysik.
Weiner:It still exists?
Gentner:Yes, it still exists in Frankfurt. But it was changed again after Rievsky retired, and they have now so changed the Institute very much and are doing molecular biology and things like that. So all this field of radiation effects is not so interesting. Molecular biology is now the thing. You have to do always molecular biology, otherwise you are not important, by definition.
Weiner:The period after your PhD was given was one in which you did a specific task for which you received money. What was that task? What was the official designation of your position?
In this time in Germany, when you got a fellowship you were called a [?]. Then I was interested to do some more exact work. I found out that biophysics was very interesting, but I had the feeling that you are just between biology, chemistry and everything, and you are not a real expert in one point. You are swimming around a little in this field, and it was not very satisfactory for me. So I tried to do some real physics, and I thought it’s better to start to do some real physics and come back later in this field, because all sorts of fields, between two or three others, are dangerous for young men. So I felt, if I couldn’t go away and didn’t have an interest to go into another country to see a little more — at this time it was very difficult to go out — and therefore he said to me, “This fellowship you have from the University of Frankfurt, I can ask if you can leave Germany with this fellowship. Perhaps it isn’t written down that you have to work at the University of Frankfurt.” Then he came back and told me, “Yes, I found out that there is nothing written that you have to spend your time in Frankfurt with this fellowship.” So I asked him if I could go, if he would write to somebody, because he knew Madame Curie in Paris and he knew also some people in England.
He wrote a letter asking if I could come for a year, and some time they wrote back that I could come if I would be interested in working with gamma rays, and I had already written that I’d worked with X-rays, and so she offered me a place in the Institute of Radium. I left Germany just the l5th of January in 1933, a fortnight before — yes. In the meantime, I had married a Swiss girl, and she was the daughter of a friend of Dessauer in Switzerland. He was a doctor who treated Dessauer. He was very badly burned, by his face, Dessauer, very badly, because in the beginning of his situation he worked to build X-ray tubes and things like that, so he was burned, his whole face and the fingers, and my father-in-law was a surgeon in Switzerland and he treated him always. So I met the daughter of this Swiss surgeon who became my father-in-law. Yes, it was partly also that I had a very high fellowship, and my father had already died just at the moment that I left school to go to the university, so I had not much money left, and had only the money just to finish my university studies. Then I had to find some work to find money. And so we left together, and I was married just before, and we left together in January for Paris, and just arrived, and a fortnight afterwards, Hitler became here vice chancellor. And Dessauer went, after some time — he was for a certain time in prison. Them my father-in—law came to Frankfurt and told the people that they should leave him out because he was in real danger, for he wasn’t in very good shape, and because it was nothing real against him, they left him out and he went later to Turkey, to Constantinople, where he was professor, and later then in Switzerland.
Weiner:The reason for his arrest was political?
Gentner:Yes. He was a very good friend of and he was a member of the Centrum party. Also, all the people from — and he was I think in this time he was against this famous law, which the Reichstag had given full power to Hitler. So he was a member of parliament many years. Dessauer was a member of parliament.
Weiner:Oh, is that so? That puts him in a different perspective.
Gentner:He was a member of parliament and he didn’t come too much to the Institute. He came usually only one or two days a week. We were more or less left alone, for three years before — he was always very busy at the parliament.
Weiner:This was a public position he had taken.
Weiner:When did he leave? He was released you say?
Weiner:How long was that before he was released? Did all of this occur in the first few months of ‘33?
Gentner:No, I would say no — they tried to at this time, they first accused him for some business things, but he was released from that, and then again they put him in prison the second time. They thought, I would say they thought he was a Jew, hut this was already two generations, and then it wasn’t difficult to prove something. But it’s more or less for his political position in the parliament. And so —
Weiner:Did he lose his position at the university?
Gentner:He lost his position at the university, yes. They had a law just to put these people out of the university.
Weiner:On the so-called racial grounds, was one law.
Gentner:No, they couldn’t. They couldn’t. So they had a special law, which means it was a special law, to the Jews, as officers. It was this law that — they released him — it was not easy, but they did it. So he had to leave Germany, and he’d better because he was in real danger, and he went then to Constantinople, to Istanbul, and became a professor with some other German professors together. A lot went to Istanbul together, and he gave lectures in Istanbul for two years, and I saw him always. A position was opened in Fleetbrook [?] which was a Catholic university, and he was a Catholic, too, so — and I was in this time still — no, I was already back. This must be in ‘35, and I asked Joliot and Madame Curie died in ‘34, yes, and I went ‘35 here. I asked him to write a letter to the university in Fleetbrook to say that also he knows the work of Dessauer all the time, and they would also say that this would be a good professor, and so he got the professorship in Fleetbrook in Switzerland. And he was living in Switzerland the whole time of the war, and after the war he came back here to Germany and was in Frankfurt and he died. But he was very ill a long time before he could die. But I was a little mixed up with the family.
Weiner:Yes, I can see that. When you went to Paris in ‘33 you went with the fellowship that you had here. What was the source of those funds? What fellowship was it?
Gentner:This was a private foundation that was called Fellowship of the Friends of the University.
Weiner:So this was through the university. It wasn’t any outside foundation, but it was through — private funds channeled through the university.
Gentner:Yes, private funds given to the university. But this was a mixture. The committee was a mixture of professors and outside people.
Weiner:But that was intended, I guess, to keep people at the university in what we could call now post-doctoral fellowships.
Gentner:Yes, something like this.
Weiner:But you were able to use it in this other way.
Gentner:Yes. But this was only for one year. And now, after half a year or so, I had to ask Mme Curie — I told her that this is only for one year, and it was very difficult to get money out of Germany to France. And then she told me, “Yes, if you like, I can look to get a fellowship for you,” and I told her I would be interested. She arranged — she died in July, 34, and I got in ‘33 already, in France you call it [?]fellowship, from Foundation Carnegie, and then just before she died, she arranged everything in the Institute before she left the Institute for the sanitarium in [?]. She arranged many things in the Institute, and so I got a letter later confirmation of my fellowship from the Carnegie Foundation. So this was the committee of the Sorbonne was dealing with the distribution of these fellowships. So I got my money from the committee of the Sorbonne and it was called a Fellowship of the Carnegie.
Weiner:What would you be called, research fellow?
Weiner:That has a nice sound to it. Now I’m curious about the Paris story. You went there with your wife, and you were newly married, I gather.
Weiner:This was your first visit to a laboratory outside Germany?
Weiner:Of curie it’s quite a different culture.
Gentner:Yes. It was in this time quite completely different from today. I was the first German who worked there. No Germans were before at the Institute. This was ‘32, ‘33 — about 10 or 15 years after the war. There’d been no relations between Germany and France, much scientific relation, much more with England than with France, I would say.
Weiner:With people like Meissner and Hahn who were in the same field, you’d imagine that there’d be —
Gentner:Hahn, yes, because he was working in England for quite a long time and he was working with Rutherford, so he had all these relations with England after the war.
Weiner:But you’re saying that there was a real barrier.
Gentner:Oh yes. Oh yes
Weiner:Then, at a time when there’s a chance for relations with Germany to deteriorate once again in the period you’re talking about, yet you were able to come. It’s an interesting phenomenon, that at a period when you would think of relationships getting worse between the two countries, you managed to come and break through.
Gentner:Yes, but I was already directed to go out and to see something from outside.
Weiner:Oh, from your point of view, sure, but from theirs —
Gentner:It was not so difficult. Dessauer had a very good name, and through the letter from — I could also go to England. I was not decided to go to Paris. I got also a letter from Cambridge, that I could go there, but I had not much money, and it was really a decision about the fellowship. I found out that Cambridge was much more expensive — I had to make some payments —
Weiner:A research fee.
A research fee, and in Paris I didn’t. And I found out that they have quite good sources of radium in Paris in the Institute, and I knew that they were getting quite active in the last years, so I thought, why shouldn’t I go to Paris? It’s cheaper to live in Paris than Cambridge. So it was reasoning in this way, why I went to Paris, and I think I was very happy to. It was a good idea to go to Paris at this time. I got a very nice relation to Mme Curie. She was very open. She was very interested. Also, in this changing in Germany came and Hitler went to power, and she was very interested to ask me what is the reason for this and what is going on in Germany, and you knew, in Paris, at l2 o’clock everybody is leaving, except at 12 o’clock everybody is leaving to run to get their lunch, and then they come back at 1 or half past 1. And I was not used to this, and was later, and she was — summertime, I remember, she was sitting in the garden and I met her. She was waiting for the car. I was sitting together with her some time, and she asked me, “Could you explain what is really going on? What is this?” From the beginning she told me that I should work together with Joliot and if I had something I should ask him. He was the top assistant in the Institute. And he was also interested, and I must say, being here from Germany, I knew quite well how to build geiger counters, and I had to work with geiger counters here and in Frankfurt.
In Paris nobody knew really how to build geiger counters. And then I discussed with Mme Curie my work. She told me that I had to do this with ionization chamber, had to measure the X-ray, as gamma rays with ionization chambers and with Hoffman electrometer and things like this. I knew these things, but I thought that it was much easier to do it with a Geiger counter. And she said, “No, with a Geiger counter you don’t know really what you are measuring, and I would prefer you to work with ionization chambers.” I had a long discussion with her about this, finally compromising, and she decided that I could perhaps do both, compare Geiger counter measurements with ionization chamber. So I stopped with the Geiger counter. Joliot was very interested in Geiger counters and he was interested to learn, so after a short time I was the specialist on Geiger counters at the Institute, and at the moment the Geiger counter began to work and I built a Geiger counter — outside the Institute, because the Institute itself was completely full of activity, very difficult Institute. They worked with huge amounts of radium at this Institute. They had 2 grams of radium, quite a lot at this time, and working on big — Joliot was very good at building big polonium sources. So he had already the thing full of polonium and things like this. I remember he had a special finger here he used later on to try out the Geiger counter.
Weiner:A radioactive finger?
Gentner:Yes. So I found I had to make my workshop outside the Institute. So I built it, with Geiger counters, and I tried them out in a special part of the building when the chemists and Mme Curie were not allowed to go, because they all worked in the chemistry, and had a special pavilion beside, and they were not allowed to go in the upper floor of the next building. So I could room then.
Weiner:They weren’t allowed to go because of possible contamination?
Gentner:For contamination reasons, yes. So it was decided the chemists were not to go on the upper floor of this building, all chemists, and this was including Mme Curie. So Mme Curie never came to my lab, never, because she was always working in the chemistry. So I had always to go down to see her to discuss my work. Joliot, he came, because he was only on polonium sources, and polonium sources were not so dangerous because the half life is not so long, and so they we dying out.
Weiner:Let me ask about building the Geiger counter and the mechanical shop. Was that shop part of the university?
Gentner:No, private. Joliot told me to go. It was a small private workshop, and here I built these Geiger counters. I remember Joliot told us also later, after the war, told me always that I had these funny ideas about the wire [?] and the Geiger counters, and how they had to look, and how this had to be — it was kind of Iko-physics, or what you call it, to build Geiger counters.
Weiner:Was it a tinkering tradition in a sense?
Gentner:How to — yes, get the surface of the wire on the inside, you had to tweak the wire in a certain way , to get the surface — clean surface — but on the other side also, electrical resistance, and how to build a high electrical resistance and amplifiers and things like this.
Weiner:How did you learn that?
Gentner:I learned it in Frankfurt already.
Weiner:Yes, but from whom? Someone you served as an apprentice?
Gentner:Yes, I worked with Rievsky in this time, and we were just sort of starting to use Geiger counters for our work, and also Geiger counters not only for X-ray but also for ultraviolet machines. At this time it was quite — there was some funny work about it, I remember some funny work about ultraviolet radiation from biological substances. There’s a special name of light that came out of —
Yes, some special light, and we tried to find this, and for this reason we built special Geiger counters with a cross window, and inside the surface sensitive to ultraviolet light, and used it. I was quite well acquainted with Geiger counters. I would say perhaps through this — because I knew how to build Geiger counters and how to build amplifiers to Geiger counters, I became in very close relation to Joliot, I would say. I saw him every day and he was very interested, and I built all the Geiger counters for him too. If something didn’t work, he went always to call me, I should look what was happening. Also for instance the story I told already before at the house, that when he discovered artificial radioactivity, I worked with him in the same room, and because he called me, “The counters are not working all right” — because at this time he irradiated with polonium, I think it was aluminum, something like this, and then you get reactions and you get out protons and neutrons, and electrons and positrons, and this was very strange at this time. You couldn’t understand how to get positrons out of a reaction. And he saw this, but it was in the cloud chamber. He was very good in cloud chambers. And when he tried out to find out if this, the relation between the energy of the alpha rays, and then he found that the Geiger counter is always giving higher number of counts, after we stopped the alpha rays.
For a certain time, for 10, 20 minutes, we had higher kicks, and then the number of kicks went down. He said, “The counter is not all right, there’s something with the counter wrong,” so he called me. I went down, and then I told him — I got a small gamma ray source and I tried out with gamma rays, and I tried this out and I found with these gamma rays that the counter is really working all right, and it must be something else. But in the night he had to leave. He was invited for dinner or something with Mme Joliot together, and he told me. I said, “I have time, I can stay a little longer,” and I wrote him a paper that this is all right. Well, he went back and he saw this, and then he said — “Oh, I think I know what it is, it’s perhaps some kind of radioactive isotope, and perhaps this is the reason that this takes also all this while longer.” In the morning Mme Joliot came in my room and told me that I should not talk to anyone about this, what we have done in the evening. She was not in the lab at this time, tonight. So after a few days, we worked on it, the effect, and in another few days they knew what was happening. So after a week, they sent the publication out.
Weiner:During those few days did they discuss it with anyone else in the laboratory?
Weiner:You knew about it because you were involved in the checking out of the counters, but this wasn’t the kind of thing that they shared or involved other people with.
Gentner:No — it was for me a little strange you see at the Radium Institute in Paris. Everybody worked for himself. Everybody closed the door, and it was not very well known what is going on in the Institute. After a few weeks, I asked Joliot one day, “Don’t you have a common seminar here, where the people are talking together?” and he said, “Yes, yes, but we have also this kind of work. You could start to tell what you are doing.” So after sometime I gave a seminar on my work, what I am doing, but after that nobody else did it. So there was really no information about what was going on in the Institute. And only, because I was used to going in the room of other people to look what they are doing, so I looked a little around and I got some information, what other people are doing. Also I went down to see Joliot, and he asked me about Geiger counters and things like this, so I got some relations with other people. And I had also some — the one important thing was also, in my room, of course Mme Curie was not allowed to come in my room — you could smoke cigarettes. Because she didn’t like people to smoke at the Institute. Joliot came to see me — he liked very much to smoke a cigarette, so he’d come to see me for a cigarette. In the workshop you could smoke also because she never was strong enough against people in the workshop. It’s difficult. So what? I mean, later, I got after some time in very good relation to Joliot.
Weiner:Were there research groups as such? You say people worked by themselves. They didn’t work in solitary confinement. Sometimes there were two, three, four together?
Weiner:Joliot and his wife?
Gentner:Yes, they worked together.
Weiner:Anyone else with them at the time?
Weiner:Assistants of some kind?
Gentner:Yes, but they worked more or less alone. They did everything. He was a very good experimentalist, Joliot, and he liked very much to work with his own bands, and he prepared the sources, and he was always talking in the workshop about what I should do in the workshop, what kind, what I should build the instruments out of. He was a very good expert in the cloud chamber. He built it more or less all his things himself. He was really very very good. He had training also from some kind of engineer’s school, just starting with physics. He was really an extremely good experimentalist, I would say.
Weiner:During this period, were there any teaching functions at the Institute, any students or any people —?
Gentner:Mme Curie gave always the lectures in radioactivity. This was I think once or twice a week in the afternoon for two years, that’s all. And there was in Paris in this time one bigger, one seminar, I would say. This seminar was in the collation of force, given by Lengevin. And then in the other building was Jean Perrin. He was professor of physical chemistry. And he, after some time Joliot told me I could come one Monday afternoon to have tea in the Institute of Perrin, — there was special club for some people who had tea Monday afternoon together, and this was a special way to get relations, and only some people were allowed to come. So I knew Francis Perrin and Pierre R. Auger. They were brought in, physical chemists. With Francis Perrin I am still in very good relation, because I see him always.
Weiner:At those teas of this more private group, would outside speakers occasionally come in?
Gentner:Yes, also guests were invited to come, and then — there you had really the opportunity to talk a little with other people. I talked with for instance Auger on cosmic rays. He was at this time working on cosmic rays. And there were some people from outside also, Hulaby from Romania — he’s very famous, later became president of the academy in Rumania. There were many people from Romania in the Institute.
Weiner:In Perrin’s Institute?
Gentner:Also in Mme Curie’s Institute, yes.
Weiner:That’s one of the questions I had, how the proportions were there in terms of French workers and others?
Gentner:I would say there were quite a lot, I was astonished to see mainly people from I would say Spain, Portugal, Rumania, Yugoslavia, of this kind of people there were quite a number I would say about 30 people all together, and there were perhaps 10 who came certainly from outside France. The Institute was small in this time.
Weiner:That’s still an interesting proportion, and you say that of those ten, you had that kind of a distribution. You said you were the first from Germany. You were the only one from Germany during that whole period?
Gentner:Yes. Only Preiswerk came later from Switzerland. He’s now in Cerne.
Weiner:When did Halban come?
Gentner:Halban at the same time, yes, and I knew Halban already very well from Frankfurt. We were together in the school, because his father was in this time the leader of a lab at the industry in Frankfurt. He became later professor in Zurich, Halban, but at this time he was in what we call today the (?). He was also a leader of the chemical labs of industry.
Weiner:Halban was in Paris at the same time you were?
Gentner:Yes, but later. He came later. I remember very vividly, because it was in this time, and we worked together on these neutrons. They worked more with Mme Joliot later, Preiswerk, Halban, they worked with Mme Joliot and I was always more acquainted with M. Joliot. So she was also more interested later in neutrons. It’s this famous explosion, one day — and heavens, explosion — to cool down. After the experiment of Fermi. Fermi found out that you can slow down neutrons by this paraffin, yes, and then they tried to do the same, and they cooled down the paraffin with liquid air, and if you know, liquid air with paraffin is extremely strong method to get wonderful explosion. And they did this, and outside — we had in the Radium Institute, as you have in the older institutes, you have these kinds of balconies to work outside, yes? And they did this outside. So the whole radioactivity was in the Rue Pierre Curie — was in the street outside — a big explosion, and it was very bad, because they used a special source that was a very special source at the Radium institute, and everything was lost. So we went out with portable Geiger counters to find out in the street where the radioactivity is.
Weiner:The purpose of finding out where the radioactivity was, was not so much for safety, but to recover the source?
Gentner:To recover the source, certainly. (laughter)
Weiner:When was that, was that in your last year there?
Gentner:Yes, that was in my last year, in ‘35, probably.
Weiner:Because the slow neutron work wasn’t going in ‘34.
Gentner:Yes, It must be ‘35, in the beginning of ‘35.
Weiner:You mentioned that Preiswerk and Halban would work with Mme Joliot, yet when we were talking about groups before, you said people tended to work by themselves.
Gentner:But they worked together, Preiswerk and Halban worked quite good together, with Mme Joliot, yes.
Weiner:what about Placzek? Had he arrived yet or was that later?
Gentner:Placzek arrived in this time, but I remember that I saw the people, all the other people — met the refugees that came at this time, and you saw them, and they came out to the tea of Perrin, and Joliot asked me also sometimes as an interpreter because he didn’t speak English or other languages, so if they knew only German or English, I went there for interpretation, and in this way — we were also quite often invited to Joliot’s in the evening as guests. Normally in France at this time you were never invited by people to their homes. They invited you to a restaurant perhaps but not to their home. In this time it was not usual in France. But the Joliots were different in this way. They invited sometimes — they liked also very much my wife, and my wife spoke French much better than I did because she is from a Swiss family, a mixture of French and German speaking family, so she spoke always at home French with her mother, and she was very good. So Joliots liked her very much so we went quite often to Joliots in the evening.
Weiner:During this time there was a great deal of political ferment, naturally. Was there discussion on this?
Gentner:Quite a lot of discussion, because the Jews came, and some people knew also that I am in Paris, and they arrived in Paris and they came to see me and to ask me what they should do, and this and that, because they knew that I’m acquainted with Morgesa (?) or the university. Quite often we had people at home to discuss what they could do and what they should do. It was quite an important discussion at this time, the whole time, and we were – it was not so easy for me, because I could go back otherwise, and they knew also that I had no difficulties in principle to go back. And for me it was certainly the same for all Germans, if you went out it wasn’t so easy. You had always to deal with discussions.
Weiner:They couldn’t be avoided.
Gentner:They couldn’t be avoided, no.
Weiner:Did many of the people who had left because they had to, did many of them have ideas that they’d soon be going back? Or was it pretty clear, from what you remember?
Gentner:From what I remember, and I myself also, I was convinced that this is going on for a shorter time. We were more or less convinced that this could not go on for longer. This was perhaps also, I was a little influenced by Dessauer, because when I left and I saw him, also, of course it was over Switzerland first by my father-in-law –- they told us, Dessauer left, but he said to us, “This cannot go for long. I’ll just go to Istanbul for a year, two years, till I come back.” This was the general idea, I’d say, in these days. Nobody –- also, in ‘38, when I came to the United States for a visit to go to Berkeley, I went to Boston, and because I knew a friends very well, Fiske… (off tape)
Weiner:He had an appointment?
Gentner:Yes, and he was a very good friend of mine. He was working here in Heidenberg, ‘36, I would say. He was married and he came, he did that trip with his wife to Europe, and he was staying here in Heidelberg working at the Institute, and we worked together a few months. And we were together also on holidays in Switzerland, mountain climbing together, and so when I went to the United States I wrote him a letter and he got to the ship in New York and took me to Boston. His father-in-law was living in Concord near Boston, you know the place, nice place, and I was there for Christmas, living together with Fiske in his home. Then I told him, “I know Pawling is living here,” and he said, “Yes, I know him, so if you’d like to see him, I could ask him. It’s perhaps better you do not introduce yourself, otherwise —” It was very dangerous. You were always observed — had the feeling you were looked at by German people, what you were doing.
Weiner:German government people, you mean?
Gentner:Yes, from the consulate and the embassy.
Weiner:Which might make it difficult —
Gentner:For me. Not for him. No, he was for free. No, not for him, it’s only that for me it would be difficult, that if I would go back to Germany that I would have difficulties. So he arranged this and I saw Pawling in the evening because I knew him also from Dessauer, who was driving him as a student sometimes as a driver. And he did some private visits at the chancellor here. He came to Frankfurt and then he was interested to have a private car with a private driver, and because I was known in the Institute as a good driver, so I took him to some people he’d like to see without much noise. So I had a long discussion with him in the evening, and I remember very well in the winter in ‘38, ‘39, Pawling told me, “You see, I am convinced that Hitler would never never start a war, and I am convinced that the Germans are not starting a war.” He was convinced of this. I was not so optimistic in this time, any more. I was very much more pessimistic. In the beginning I thought it would only go on for a certain time, but in ‘38, ‘39 — and also this was what I told Niels Bohr when he came to the United States. I was very pessimistic. And after the war when I wrote to Niels Bohr to invite him to come here or to send somebody here, it was in ‘50, he wrote me a very nice letter back and said he remembered always the last dinner with me in April in New York, and with Alice Lawrence, and — because he was so impressed by a German who was so pessimistic about the future. Of course, people in Germany didn’t know. They didn’t see the danger. I went back, and then I remember very well, people told me, “Oh, there will be no war. Hitler would never start a war, we are convinced of this.” I came back from the States, and then I was with Cockcroft and people in Cambridge, and they were all extremely pessimistic, extremely pessimistic at this time.
Weiner:More so there, then, than in the United States?
Gentner:More pessimistic, much more, because in the United States, they were pessimistic in New York but not in San Francisco. Berkeley was very different, I would say, from Columbia in this way. At Columbia they were very pessimistic, and at Berkeley they were not so pessimistic, no.
Weiner:Lawrence — the same was true of Lawrence.
Gentner:They were much more also looking on Japan — their fear of war with Japan at this time. I would say they were also looking more in this direction perhaps.
Gentner:Yes. At this time there was not so — Berkeley and Lawrence was always different in this way. He was more, he was a very good American, but more conservative on this. Probably you know him.
Weiner:Yes. I know he thought stability had been achieved in Europe, at least that a war would be prevented. A lot of people believed that too. For a moment, this is off the track I think we’ll pick this up in a minute, Berkeley and the US. In the discovery of artificial radioactivity which you described, these two ways of activity, of work on your part, it wasn’t until they were preparing the publication for mailing off that other people were brought into the discussion?
Weiner:And then was there any sense of excitement, a sense of understanding of the significance of this?
Gentner:Oh yes. At once, yes. You see, in Paris you had always to prepare the publications for Monday, because Monday afternoon is always a session of the Academy. Then you had to give your paper to Jean Perrin. Of course, Mme Curie was not a member of the Academy, you know. But Jean Perrin was a member. So you had to go Monday morning with your paper to give him, see. Then he brought it to the Academy. On Wednesday you could go with the printing, the Comptes Rendus. You could go read the corrections, to make corrections. Next Monday it came out. So in a week’s time the publication was done. It was very fast. So they had to finish the work Sunday evening, we had to finish our work, if we wanted to have it in the Comptes Rendus, in the date of the Monday.
Weiner:This had the actual discovery, or the point where you were called in was about a week prior to that Monday?
Gentner:Yes, I think so, something like this. Yes. I remember it must be for about a week’s time to do the first publication. Then they did a lot of others, to prove — mainly they were interested to prove chemical work to take really the special radioactive element out.
Weiner:What was the nature of their collaboration between them? Was it mostly one, and then the other took over at a certain stage?
Gentner:I would say he was very good as an experimentalist. She was very interested in chemistry also. She was trained by him in chemistry. And so — and all the others felt she was as little more trained in theoretical things perhaps then he did. Than he was. So they worked quite well, very well together. It’s very difficult to say. I’m perhaps a little influenced because I spoke much more to him. She was not so easy to talk to, and she had — so what do you call — to talk. It was really not easy to talk to her, to have real relations to her. Perhaps in the wartime more, when I went back to Paris in the wartime she was — yes, she was, because she saw that I was looking after him and so on, so that I was looking that there would be no danger for him, and so she was sometimes very nice to me, to talk to me, and then to help to go to Switzerland. Because there were no post relations between Switzerland and France at this time, so she wrote a letter to my wife, to have it back, and I sent the letter to me, to Paris, and I give the letter again to Joliot. In this way we had more relations. But at the time I had much more relation to him. He was very open and he had a big influence on the people at the Institute also, people at the workshop and all the technical people had extremely good relations with him. He got everything that he could. Also Mme Curie was very proud of him, and if you didn’t get something at the Institute you went to him and then he arranged things and you got it. Also you could get priorities in the workshop on all these important things, and the lab. But she was always, to everybody, she had no — she had difficulties to talk to the people, always, to everybody she had difficulty.
Weiner:Because she was reserved and shy?
Gentner:She was reserved and shy, yes.
Weiner:A nervous kind of person as well?
Gentner:I don’t know. Probably perhaps it came also by this education, and I don’t know, it was certainly very different from her sister Eve. I saw her only twice. I don’t know her very well. But I always had the impression that she was different. She was certainly very shy and reserved and so on.
Weiner:Did the situation in the laboratory and the atmosphere change after the artificial radioactivity was discovered, since this is absolutely something that the world —
Gentner:— yes, it did change, in this way. This was in January, I think, was it, ‘34? It must be. January or February of ‘34, July, Mme Curie died — only a few months later Mme Curie died. She was still in the laboratory, I remember, at this time, for she was very proud about the discovery. But later it was changed and the directorship — Dublan became director, was the successor of Mme Curie. Dublan became successor, and in ‘35, Joliot became professor at the College de France. All this was the reason that I then looked to go back to Germany, because the French Radium Institute, there was a new director, Dublan, who was a strange man. He went in his lab and closed the door behind him and it was very difficult to talk to him. There was a change, and Joliot was more and more going over to the College de France and so it changed a little.
Weiner:Mme Joliot was still there though?
Gentner:She was still there. She was still there, but the collaboration between the two broke also at this time.
Weiner:Because he then also had his own —
Gentner:He had his own laboratory. Yes.
Weiner:What role did Kowarski play in this period? He was certainly there.
Gentner:Yes, I know him from this time. I had not so much relation with him. I know at this time he was working on proportionate(?) amplifiers and then proportionate counter amplifiers mainly. But I must confess, I had not very much relation in this time, more relation to Rosenblum. Rosenblum was there and I very often went down to Rosenblum. He was downstairs working with — he did his famous work on alpha rays, the spectra of alpha rays, and it was with him I had perhaps the best relations in the Institute, Rosenblum, much less with Kowarski. Kowarski was always a little strange man. Some other people had more relation, from Romania, and also some French people. I was at this time interested to learn French and to have talks with French people to learn more French. There was also, for one reason, to go to other people, because I thought I had to learn French and quickly, and you learn best in talking.
Weiner:What better place? In a minute I want to ask about the development of your own work there, your own research, but before that, perhaps another general question. Did you get during that period any feeling that they had an idea of the role of their laboratory in terms of the world, the development of nuclear physics? Were they thinking of carving out an area, or were they thinking that they were the center of a certain kind of research? In other words, I don’t know how one gets at this, but did you ever get through conversation with them or through the things that they said to others a feeling of how they regarded their own work in relation to the rest of the field, how they perceived themselves?
Gentner:They had good relations –- I remember Blackett came sometimes, and also there were visits -– Joliot, he published one strange paper, writing down that he had some, what was this, taking this -– electrons going to the source. This famous paper from Joliot. And he was a little astonished that so many electrons went back to the source, and he wrote this up in a paper at this time, about it. Then Blackett came one day, after they took the pictures, Occhialini, and he came back to do some statistics with him, what’s this strange effect, and to prove that these were positrons going out of the source and coming back, not electrons coming back but positrons going out.
Weiner:That implies that perhaps he wasn’t keeping up with work elsewhere, is that it?
Gentner:No, at this time the positron was not discovered. The positron was not discovered. The positron was discovered by Anderson –-
Weiner:‘38, and the first photographs were Occhialini’s and Blackett’s photography.
Gentner:Yes, it was written in —? Yes. It was like this probably. Blackett came later, after the discovery of the positron. Blackett came to talk with him about his photos. This is what it is.
Weiner:Yes, because Anderson’s discovery was ‘32, but the first photos were ‘33.
Gentner:‘33, yes, and I went in ‘33, and I remember Blackett came one day to look with Joliot through the cloud chamber pictures he took, and to make statistics, and to tell him that he’d discovered the positron but he was too late. So Joliot told me — after they discovered the radioactivity, I remember very well he said to me, “With the neutron we were too late, with the positron we were too late — now we are in time.”
Weiner:He fully enjoyed the success.
Gentner:Oh yes. Yes. Certainly, yes. No, it was a very good competition in this time between the few institutes, Cambridge and this, and Bothe. There was then in Germany more or less Bothe, and in Rome Fermi and the people. That was nearly all. There weren’t so many. Very small group. And we met for the first time, I think it was in July ‘33, I went with Joliot together, and Mme Curie said to me, “Yes, you can go with Joliot together to Zurich.” Scherrer did in this time always — this nuclear physics week in July in Zurich. And I went there ‘33 together with Joliot, his first trip to Zurich and my first trip to Zurich. We went together to Zurich.
Weiner:Did you present a paper on the program?
Gentner:I think so, yes, because I worked in this time on the absorption of gamma rays, and we had just found out that probably this strange behavior of absorption counts was a — for positron pair production.
Weiner:I think I’ve found some of the programs of those meetings. I can reconstruct what the program was each year.
Gentner:It was a good meeting. (crosstalk)
Weiner:…printed program but the papers didn’t necessary get printed, unless they were submitted to some regular journal.
Gentner:Yes, yes. I published at this time…
Weiner:I know the one in 1935 on absorption of gamma rays in heavy elements.
Gentner:Yes, but I published already before in ‘33, with Stockridge together, in the JOURNAL OF PHYSICS probably.
Weiner:What is RAD, radium, in this case? I have it here. It’s this one. The first one that’s —
Gentner:Absorption of Gamma Rays, yes, Journal de Physique Radium. This is called. But this is a later paper.
Weiner:This is not complete, this is part of —
Gentner:Yes, on the gamma radiation. This is later, yes, much later. I think my first paper was in ‘33, and then in Paris, some —
Weiner:— sometimes, I see. So it was quite clear that from the time you arrived there, that your line of work was going to be in gamma rays, and you set up to do it on your own, except that you discussed, with Mme Curie.
Weiner:Did you then after a while have other people coming to work with you?
Gentner:Yes, one day I found a letter on my desk from Mme Curie and she told me that in the — that a Polish physicist was arriving the next day and that she would propose that he worked with me. This was Starkovitch. I published with him also a paper. And he was a long time working with me, Starkovitch, and Mme Curie was very amused because he knew about the same amount of French words that I knew, and we always tried to talk in French. We both didn’t know it. This was the only language we could talk together in, French. He didn’t know German and I didn’t know Polish, and English at this time was not so well known, so we tried to talk in French together, but we were not very good in French, both. Starkovitch was less. He only knew French, not very good, certainly, so I had to give him a few lessons in French and Mme Curie was very amused that I — He was later in the wartime In England, I think. He never went back to Poland.
Weiner:Did he have any knowledge of counters and techniques?
Gentner:No. He learned, yes. He was mainly learning from me. He was very nice, a very nice man. He wrote me always letters later and said he did learn a lot in this time.
Weiner:He already did have a doctorate?
Weiner:So he worked with you. Anyone else as time went on?
Gentner:No. I think I worked only with Starkovitch in this time. No. More or less alone. I published only papers alone or with Starkovitch at the time I was in Paris. I never published with other people any work, no.
Weiner:Getting back to a question I asked before about the awareness of people in Paris of work going on elsewhere, if there were no regular seminars and colloquia there, and if there was a tendency to work in sort of isolated groups — were they out of touch really? In other words, were they well informed or were they suffering somewhat from relative isolation? I’m not loading the question, I just —
Gentner:They had some relations, but in this time, first, you could read nearly all journals, because there were not so many, and in the journals you could just look through what was interesting to you. Today you have not the time to look through all the papers, but in this time you could do it. So I know that there was some correspondence going on also later, ‘38 and so, between Hahn and Mme Joliot, but very few letters, I would say. Hahn always — people in Berlin had much more relations to Cambridge, no relations to France. You had not — there was only this — this was a very important thing, I would say, the July meeting in Zurich at this time was very important, almost also for the experimentalists it was important. I later also had always with Scherrer very good relations, and I went to him also after the war to work a certain time. He was the first man to, I would say, to do something for European meetings in nuclear physics. There were no meetings before.
Weiner:Yet it would be an invited group, wouldn’t it, or would it be open to the public?
Gentner:No, only invited people. In Zurich.
Weiner:Yes, the papers I know would be invited, but what about the participants?
Gentner:There weren’t so many people interested in these meetings.
Weiner:So for example from Paris, just you and Joliot went?
Gentner:Yes. Nobody else.
Weiner:You went first in ‘33. Did you go again the next year?
Gentner:Yes, the next year, again. In ‘35, every year — also later from Heidelberg I went.
Weiner:What was the atmosphere there? Was it formal papers?
Gentner:No, very informal.
Weiner:I’ve seen the program, with a name attached to a topic at least and that kind of thing.
Gentner:In one evening, we were at the home of Scherrer, another evening with Pauli. There was always a boat trip to the Lake of Zurich for one day to talk together.
Weiner:I have a photograph from the lake which shows a number of people.
Gentner:Sommerfeld was also coming. I remember Sommerfeld very well. He gave us a lecture on Raposweil(?). We went always to Raposweil. This is on the end of the Lake of Zurich. I don’t know if you know it — Raposweil, famous (?), because some Polish people of the last century were living in Switzerland and Poland was divided between Russia, Austria and Prussia, and they went as refugees there. There were always a lot of Polish refugees, and there was also some Polish king, and Sommerfeld gave a -– he was always teaching, so he gave also –- had a lesson to us about the history of this place, in relation to the Polish history. Then we came to a little island also in the lake, and also there Sommerfeld gave a lecture on the history from –- it was at the time of the Reformation an important place. It was very nice. Oh, on the (?) people perhaps it was much more.
Weiner:When you say that people in Paris for example would check what their interest was in the journals, was their interest in nuclear physics and its spreading, or was it more now on radioactivity?
Gentner:Oh no, there were not so many papers in that time.
Weiner:Oh no, I don’t mean that way. I’m talking about the interest of the people in Paris, whether they saw themselves as radioactivity experts or were concerned with nuclear structure?
Gentner:Much more they were very good specialists in radioactivity. They were also interested in nuclei, in radioactivity, in old classical radioactivity. When I went there also Mme Curie was mainly interested to find out if everything was true in uranium, radium, lead radioactivity, and mainly on planchis(?). They were working on this planchis, beta, alpha, planchis, and things like this. No, I would say the whole Institute was more or less directed, and Joliot was the man who did other things. He was much more open to the new work of –- with neutrons and other things. He was much more open to the new work of –- with neutrons and other things, than the other people, who were working mainly on what we call today classical problems.
Weiner:Did his interest in these things extend to accelerators? Do you recall any discussions on it while you were there?
Gentner:Yes, he started in this time. We were discussing quite a lot about accelerators, and we went also together to Zurich to see there — he had already at this time the idea to build a cyclotron, and we went together in Zurich to the Olican(?) factory, and Scherrer was interested too. No, the Olican factory was a factory because Weiss — you know the name of Weiss, who was the man of …
Gentner:Yes, Pierre Weiss. He was later in Strasbourg. And he was I think in the beginning in Switzerland at the Olican factory, to build magnets. And they had a certain tradition, at this time, talking also about magnets for (?) and things like this, for cloud chamber work, and Scherrer got also later his mainly from Olican, and Joliot too, the first magnet in Paris was also built in the Olican machine factory.
Weiner:While you were still there, he took that trip, and he had in mind —
Gentner:He had in mind also to build a — and he was building also outside Paris. Yes, he was interested to get high tension, and I remember when Mme Curie, this was in ‘34, she died July ‘34, and she left behind a letter, and in this letter many things were arranged. For instance, prolongation of fellowships. And also she looked that Joliot got a certain amount of money from the foundation to build a high tension, I remember. And then he was outside Paris. There was a lab in a place, what is the name of the place. We went together there many times, and then he was –- his was high tension, for the factory to try out some, so big isolators.
Weiner:Did he get a Van de Graaff?
Gentner:No, no, a Max. You get only one pulse. I don’t know how you call this. You use many different capacities, and you can charge the capacities in parallel, and then you discharge the capacities in series, so you get high tension. The shock. And he was building a big tube, to get high tension to a million, but this was very difficult. We worked together on this problem, to build tubes, and they were always cracking because of this high tension shock. It’s very difficult to build some things. I lost quite a lot of time with this. It was when I was going with Joliot together in a lot of things. And we built –- he wanted to build a cyclotron, and we were talking to the Olican factory about the possibility, the price of magnets and so on. I think it was in ‘34, ‘35 probably when we went together to Zurich.
Weiner:What had he in mind to use the cyclotron for? Some people wanted sources and they came to it just from that point of view. In his case he had more than he needed, in a sense. There was more radium for classical kinds of work in Paris than –-
Gentner:Yes, certainly, but he still wanted to have sources of radioactive isotopes. I think he was also interested really in the kinds of nuclear reactions, to find out by chemical methods, to find out and to have different isotopes, what is the reaction, what kind of product you get out.
Weiner:Did he seem to be interested in biological work at all?
Gentner:Not so, no. Not so, no. No. There was a special department of the, what they called the Foundation Curie, that was just in the neighborhood, and they were working on these problems. They had relations certainly, but Joliot himself, he was much more interested in building instruments to do physics, and later in beta radioactivity. He was also very interested in beta radioactivity. He did also some strange publications in this field too. (laughter) I’ll tell you something else about the publications.
Weiner:In this period, getting back to your work, you followed consistently the gamma ray work.
Weiner:Was there anyone else who was keeping up with you on that, whom you were in close touch with, whom you would regard as a critic or even a long distance colleague?
Gentner:Oh yes. That was the reason I went here to Heidelberg, because Bothe did some publication in this work. His doctor’s thesis was published here by Bothe and Horn, I think, and Lise Meitner was working on the same problem. And so I went, I would say, three times from Paris to see Lise Meitner to talk about it. In France, nobody did work on this problem. I was alone. So I went to, many times to Lise Meitner, and Hoffman, who was later in Leipsig, the man of the Hoffman electrometer. I don’t know if you know this. There is the famous Hoffman electrometer. There is also the famous picture of Joliot’s, from where I have this picture, but perhaps I have the picture at home. It is a picture of Mme Joliot and M. Joliot sitting in the lab, I think it was in the time of perhaps the discovery of the neutron, and they were working always with the ionization chamber and Hoffman electrometers. They bought these instruments in Germany. But it was a nasty instrument, really very difficult to arrange. Joliot was very good with this. I try to find out where I could —
Weiner:Would it be in the biography of Joliot? Piccard’s biography?
Gentner:Yes, probably in Piccard, because he had long talks with me about this time. It is not so very long ago, I saw this picture.
Weiner:The point about it is that the electrometer of this same Hoffman is the one in the photograph?
Gentner:You see it in the photograph. Later he gave up more or less and he worked on these counters, but when, as I said to you, when I went to Paris they were only working with Hoffman electrometers. They did the whole neutron work with Hoffman electrometers.
Weiner:Now, in terms of your own work, you mentioned people in Germany, nobody in France?
Gentner:Nobody in France. It was only Lise Meitner, and coworkers, but Hoffman was working on the problem and Bothe, he had started, and he published something about this, the diffusion of gamma rays. I did not believe this. I knew that this could not be true, and so I went to see him, and at the same time I was looking for another place, and then Bothe asked me, he said to me, “Yes, if you like to come, you could repeat here this, if you don’t believe it, you can repeat it here.” And I said yes I would do this. In this way I started here with the same work that he had done, and I could prove to him that he was wrong. And in this way I got the permission hare.
Weiner:You came without a position though?
Gentner:No, I came from Paris, to find something.
Weiner:And you worked here for a while without a position?
Gentner:No. I had only a fellowship for a short time.
Weiner:From the university?
Gentner:No, from Max Planck here. In this time it was Kaiser Wilhelm Institute.
Weiner:What was Bothe’s position? Was he in a position so that he could accommodate you and help you? What was his status within the institute?
Gentner:He was the director of the Institute. You see, he went to Heidelberg. He was first the (?), and later he went to Geissen as a professor. Then he became the successor of Lennard here in Heidelberg in ‘32, and in ‘33 he became ill, and he was a certain time in Switzerland in a sanatorium. Then he went back there. In the meantime, they had announced another professor here, and then he had to battle with the people, and he, at this time the position at the Institute became free and they asked him to go there. Somebody from the party was here and became professor at the time Bothe was ill. This was the — a pupil of Lennard in the Institute. So he retired from the university and took over the directorship of the Kaiser Wilhelm Institute, in the Institute for Medical Research. It was called the Institute Physik, also Institute for Medical Research.
Weiner:Yes, I wondered about that. Now I remember about that and I wondered why that arrangement. It didn’t reflect his own research interests.
Gentner:No, but you were completely free to do what you like.
Weiner:But why would the medical research institute be the parent organization for a physics institute?
Gentner:This was the idea of the founder of the institute. He was a medical doctor. He was a professor at the university and he had the idea to have in one house together with this chemists, physiologists, and medical doctors. This was his own idea, and he thought this would be a good idea to cooperate. But still everybody was free to do what he liked. But they had common seminars, and everybody could go to the man and ask him about a question in physics, or a question in –- quite a modern way.
Weiner:Did it work?
Gentner:More or less, in the beginning. Later it didn’t. The reason later was more or less political reasons. Bothe didn’t like Richard Kuhn, and they didn’t talk together, and there became these political reasons, and you were always related to a certain group of people, and people didn’t talk to other people. This was more or less in Germany the way, strong, this political separation. You knew always very well whom you could talk to, and you could not talk about political things.
Weiner:Yes. By the way, did you sense that at all in France? I understand in France there were in general political divisions between laboratories.
Gentner:Yes. Very strong ones. That’s true.
Weiner:That was conscious. You knew that.
Gentner:Oh yes, I knew that very well, yes. For instance, there was the one club, this was Joliot, and there was Perrin’s, Pierre Auger, and this was one club, and the other club was the people of De Broglie. De Broglie’s was the other club, completely different. I remember very well, it was the beginning of ‘33, I was completely now, I didn’t know anything. One day I said to Joliot, “I’d like to go see also the laboratories of De Broglie. I’ve never met the man, couldn’t you introduce me?” And he said, “Yes, if you’d like to go, go.” But he didn’t telephone. Nothing. He did not introduce me. So I found out that there were not good relations. And later it was clear to me. After half a year, I knew very well who was more in this club -– a little left or Socialist and so on. In the other people were very conservative Catholics. Very different people. Also in this time, — later, Milliot(?) and perhaps Heitz with Joliot, about the beta decay also, famous story. For the moment I can’t -– Anyway, when I came back, Joliot asked me one day, “You have been in the Institute of De Broglie?” I said, “Yes,” and he said to me, “Didn’t you find also that they have already done everything?” Those people also did not come to the Monday tea of Perrin. They did not meet. I did not meet those people there.
Weiner:And you were a foreigner; it’s difficult for a foreigner coming into that situation.
Gentner:Difficult, yes, but later you were used in Germany to the same. Very difficult, yes. Yes, it was exactly the same in Germany. Later, in the wartime, I went back to Paris -– still it was a certain type of people were very friendly to me as a German, others didn’t talk to me. And those, as Joliot, they talked to me only because they knew me. Ellen, the daughter of Joliot, she came here, perhaps on my 60th birthday, which is not five years ago, she gave a lecture here, and in the evening we had dinner together. And she said to me, “I have to tell you this story.” See in the wartime, she was a girl, and I went one Sunday afternoon, I went out to say something to Joliot which I couldn’t say on the telephone, so I went to see him in his house, and he was sitting in the garden, and I just came in, you know, went up, and he saw me, and then went to see me. We went into the house to talk together and I left again. And his daughter Ellen told me, “You see, I remember always, I was interested, I asked my father, ‘Who was this? Who came in? I never saw him before,’ and my father said, ‘Oh, this was a German.’ And I said to him, ‘Oh, but you spoke –- why were you so friendly to this man?’” She remembered this as a girl. Of course, normally they were not friendly with Germans at Joliot’s. She could not understand this answer of her father.
Weiner:How old was she?
Gentner:She was at this time –- how old is she now? –- she was perhaps ten or something like this.
Weiner:When you came to Heidelberg, as you explained the circumstances, because the situation in Paris was changing anyway and the line of work which you had started was being pursued at Heidelberg, so it was quite natural. When was it, it was ‘35, what month was that?
Gentner:I went here in end of July, ‘35, yes.
Weiner:How soon after that did you get a position here?
Gentner:I don’t know. I think he told me that the official position was not free until I had to accept a fellowship, and I think the next year, ‘36, I got a position here of assistant to the Institute, ‘36, yes.
Weiner:Wasn’t it about ‘37 that you had some relationship with Frankfurt as well, became a lecturer there?
Gentner:Yes. I became a lecturer here, because you see I could not — I became a lecturer here because the university was occupied by people of Lennard, and in Frankfurt, I got my doctor’s degree in Frankfurt and I knew Rievsky still, and because I was interested to give lectures, I asked him if I could give lectures and he arranged this in Frankfurt. I was not there, and this time for me was very important. I had not yet — he did not ask me, because I was in Heidelberg, living in Heidelberg, and did not ask me if I am a member of the party or something, organization, he didn’t ever ask me. It was very important at this time not to be in one place too fixed.
Weiner:You mean, the advantage of being mobile and flexible?
Gentner:Yes. You see, I was here in the Institute and the Institute was completely separate from the university, had nothing to do with the university, private organization, no state organization. So the influence of the party was very small. And in Frankfurt the influence on me was also small because they knew that I was in Heidelberg, and gamma rays, and then just a very short time, Bothe was interested at this time to build accelerators, and then this was also the reason that I went here to stay here, so I started to build here a Van de Graaff machine.
Weiner:How soon after you arrived was that?
Gentner:Oh, very soon. Very soon. I arrived in ‘35. I would say in ‘36 I had the first Van de Graaff machine here.
Weiner:Was there any other one in Germany at the time?
Gentner:No, this was the first one, the first Van de Graaff machine here in Heidelberg.
Weiner:Wan there a need for special sources of support for that?
Gentner:No, this was a very cheap machine. We could build this machine with our own resources, in our own workshop. I had still the people here in the workshop and they worked with me on this, in this time, to build the first Van de Graaff machine. I did it in a very cheap way. I don’t know, you have seen the pictures? I can give you the pictures of the Van de Graaff machine. If you see the pictures you will see that this is a very cheap machine. We got about — the first machines about for 600 thousand volts, and the second was about for one million.
Weiner:But you’d never had any experience building it?
Gentner:No, but you see, I had in Frankfurt for my doctor’s thesis, I took up high tension for my cathode rays, so I had to build up 130 thousand volts, with transformers in this time, transformers and rectifiers. So I was trained in this. This was also the reason Bothe was interested, and I told him I worked with this and I had to build in this time my own high tension. You could not buy this — old transformers and some rectifiers and so on. I built the first Van de Graaff machine and the second Van de Graaff machine, and this I did more or less alone in the factory, the workshop.
Weiner:When did you start using it for experimental work?
Gentner:First publication? I would say the first publication on this in ‘36 or something like this. Here are all the publications of the Institute, and —
Weiner:— oh, that would be nice to have a copy of that, you know. (off tape)
Gentner:Bothe and –- so this is my — … yes, this was published in ’37, but it was experiments were published in ‘37, I see, yes. …
Weiner:Is that the first protons papers you’re talking about?
Gentner:No, about the first publication I see here was in ‘37. It must be in January ‘37… Then it said, “Bothe and Gentner… The new high tension institute,” and then it says here, “This will be published soon.”
Weiner:And the date on this one is?
Weiner:I see. So it’s already in use by then, but the first publication on the technical aspects of it?
Gentner:No, this was later, much later published, and of course later published here, we published this much later because in the meantime, it says work on photo effect, nuclear photo effect. I started with this in Paris already, and my first publication on nuclear photo effect was in Paris, with the radium gamma rays on beryllium, and the thorium gamma rays on beryllium. Then I did with Bothe together this nuclear photo effect with the lithium gamma rays, when you bombard lithium with protons you get the gamma rays of 17 million volts, and with this –- these very powerful gamma rays -– you could get all elements, photo effect in all elements, and with thorium you could do only with deuterium and beryllium. So this was published here. Yes, this was the first. Here you see the picture here. This was a very cheap machine. Later I got as a gift, from industry, I got all those things — you see here, the Van de Graaff machine.
Weiner:When you say from industry, what was their particular interest? Did they think that there might be some application for them?
Gentner:No, at this time they did not, they had no use anymore for this…I knew quite a lot of people in the industry personally. I asked them. I asked them, and so I had a very good relationship with the factory, and so I told him that I would need something, and you certainly have old things standing around.
Gentner:Old things standing around, and I’m looking what I could get, and he gave it to me. In these times, they were very nice to help. No, it was nothing behind it.
Weiner:You first built one Van de Graaff, then right away you started one for higher energy. Was that the sequence? What was the reason then for getting a bigger one?
Gentner:A bigger one, the reason was, you see, the resonance for the lithium gamma rays is in the 440 kilowatts, and with the first machine we could go to 600 but not higher, and then we knew that with boron there was another resonance at 800 and we could get another energy of gamma rays in this way, and we were interested to try out what would be the effect of the two different energies, to see what is it, how it is depending on the energy, the gamma rays. So we were interested to have other sources of gamma rays, because you could not produce in other ways gamma rays in this time.
Weiner:These were really motivated by a category of experiments.
Gentner:Yes. You see, here, it is written here also, at the end of this first work I have written here on the other side, there is a publication of Crane, … Cal Tech, and they say that they produced gamma rays of 15 million volts, bombarding boron with fast protons, and we were interested to get also these gamma rays of 15 million volts for our research. And I here in the end have written a correction. In the meantime I found out that we are in accordance with this work of Crane and Fowler and Lauritsen. I think this is going on in another way. So this was the reason that I changed it later, was just this point, that we got another energy of gamma rays, of this higher energy, with boron.
Weiner:When was the second one? When was it completed?
Gentner:The second machine? It must be, I don’t know if I have published this second. This is publication of the Institute from ‘36, ‘37. All this for me, for — the Institute publish (crosstalk).
Weiner:If it’s possible, if I could somehow get a Xerox copy of these publications, it would really be a good chronicle of the development of the nuclear physics work. It would be nice to have, I think.
Gentner:Yes because there are all these publications of, ‘38, let’s see, perhaps it is in this paper. I don’t know exactly if I, if there’s a picture in another publication.
Weiner:It’s quite clear that it wasn’t long after the first one was completed and working that you began to start on the second one.
Gentner:Oh yes, soon afterwards.
Weiner:Were any more resources required for that than you need for the first?
Gentner:No, it was about the same. There is the second one. Here is published the second one. You see, I put only in the old, in the later the new one, the higher one, so I got a longer tube and I increased the starmeter here and then I got another, this was the second one. I don’t know if I have a real publication. I found out later when I gave a lecture, I found out that one paper was left out of my own paper, so I put this in here. This was when I, this was written after my visit in the United States.
Weiner:Oh, that was later on.
Gentner:Yes. But it’s very possible that here in this time we have still a publication. I think I published this with Bothe. It must be in this.
Weiner:Meanwhile, you had done the work on the two machines. Was there any other activity of this type at any other institutes or universities in Germany? Was anyone else getting on the accelerator bandwagon?
Gentner:Not much activity, I would say. Debye was starting something in Berlin, but they ordered the high tension with Siemens at this time, and — most of this here, in this paper This paper is from January, ‘39. And I left, I was already away, and we published, we wrote this paper before I left for the United States.
Weiner:So it’s likely the machine was built in ’38.
Gentner:Yes, because there are already the results with the new machine, and you see here what I said, the two energies, one with the lithium gamma rays and one with the boron gamma rays. We are comparing the two radiations in the cross-section for these two energies, to see if the cross-section is going up or down.
Weiner:When you were doing this, the people who were most closely working on it were the people in Pasadena, Lauritsen and —
Gentner:— but they did not work on the photo effect. I remember, when I went to Berkeley, and I went first to Rochester, then Berkeley, then Pasadena, and looked for the photo effect, the people said, “Oh, that’s a very difficult thing, to use gamma rays,” because Fowler and Lauritsen, Lauritsen and Fowler were young men my age at this time, they were more interested to measure the energies of these gamma rays, and they were more interested to find out the type of reaction. And we used the gamma rays for nuclear photo effect. So nobody did in this time. We were the first to use gamma rays.
Weiner:In the areas where your interests did overlap, did you correspond? Did you exchange letters with the people in Pasadena before your visit?
Gentner:No. They knew our publications when I came here, but we had no correspondence, no.
Weiner:Would it have been difficult politically to correspond?
Gentner:No. Oh, no, this was not difficult. But I must say there was no — everybody published very soon and quickly all the research, so you could get all information from the publications.
Weiner:In this cane you had the instruments you needed anyway. It wasn’t a question of technical information.
Gentner:No. No. You got some information — also with Van de Graaff, I saw him when I went over to Harvard, to Cambridge MIT, at this time and saw him the first time. He knew about my publications, that we had a machine like this, and I talked with him. But he — it was already published, the machine, and it was not so difficult. His technology was not so difficult, to have this idea, to use, well, electricity. It was very important, and then you had to think why this Van de Graaff machine is better than these machines with transformers. Once you found out that this is the reason, that you have much less capacity and less big sparks, this is Van de Graaff machine, so the tubes are not destroyed. I knew very well that you can destroy all tubes with big transformers and capacities, they discharge, bang. With the Van de Graaff machine you get only small sparks, and the tension is just going down. The first spark and the tension goes down, so there’s no damage. It’s very important, this effect, awfully important, and I understood, this is the reason I gave up all ideas about transformers. For instance, Debye, who was working in Berlin, worked for many many years, and in Cambridge too many years with Phillips together on transformers and rectifiers, and their difficulties with these machines — they get perhaps better beams, but normally for a very short time only, because they crash down and the whole thing, these big sparks. So, because I had my experience on my doctor’s thesis, how difficult it is to use these transformers and rectifiers, and so I always used only Van de Graaff machines.
Weiner:And yet at a certain point you began to get interested in cyclotrons.
Gentner:Yes, for higher energies. I think we talked first, with Bothe together here, we talked and then started in ‘35, ‘36, I think ‘36 perhaps. Bothe wrote the first official letter asking for money for a cyclotron. Then it was decided, I remember in ‘36 he came and said to me their answer. It was, here is money for the (gemensachaft?)… at this time. They asked money, and they said, “There are so many cyclotrons already in the United States, why do you need another one?” So after some time Hoffman in Leipzig, he was also helping to get the people interested, and then it was decided in ‘37, I would say, it was decided that they should build one or two cyclotrons in Germany.
Weiner:What accounted for the change in thinking on that?
Gentner:I would say it came mainly from the industry. Siemens in this time said they would build this instrument. They were interested also to build cyclotrons. And so in ‘36, they were more or less ready to do something, and then in ‘27 — really, there was — I was waiting more, between one and two years, to get permission to go to Berkeley. I said, it would be very good if I could go to the United States and learn the techniques first. Then I had difficulties to get permission. Also my personal status was not so easy here, and I have still letters that they wrote, “No, this is not possible to give you the permission to go outside Germany.” Then finally with the help of the industry, again, the industry had all this influence, and this was mainly one man in the industry who had influence and he one day told me, “Now I got in Berlin the permission that you could go to the States.” I left. After some time I got official permission and then got the visa and I left by ship, with ten marks.
Weiner:Was that all you could take?
Gentner:That was all that I could take, and from the man in the industry, he gave me a letter to some representative in New York from his factory. It was a factory for steel here and they had a representative in New York, what they called (?) in America, steel factory. They had a representative in New York and I had a letter only to him, and he was at the harbor waiting for me, and he gave me the money.
Weiner:It’s easy when you know how.
Gentner:Yes, you have to know how. Because I could not take out money.
Weiner:What role did the Notgeneinschaft play? They didn’t apparently pay for the trip.
Gentner:No, this was paid by Herr (?), and this was also the foundation of the industry for industrial research.
Weiner:You mentioned that you did get support from Notgeneinschaft, that they said maybe they should have two cyclotrons.
Gentner:Yes. They built the cyclotrons — paid for the cyclotrons. But the trip was paid for by Herr (?)from the industry, because they thought it would be good to have an expert before, who gets information, that really we are losing time. So Bothe I think wrote a letter to Lawrence to ask him if I could come and he answered yes, certainly I could come. So I wrote a letter again to James Fiske, that I would arrive in New York, and he looked for me.
Weiner:Prior to this trip to the US, how had relationships been between scientists in Germany and people in other countries?
Gentner:Bothe in this time was very well known, you see. He was very well known and he knew all the people from meetings, and I think there was — so for him it was easy to write a letter to Lawrence or somebody else.
Weiner:But I mean, I wasn’t thinking just of preparing for the trip, but what was the normal exchange?
Gentner:There were very few exchanges. I remember it was very very seldom that an American came here. Very few. I remember there were perhaps three or four Americans came here to Heidelberg, and we were certainly — yes, in ‘38, there was this congress in Paris. And we saw some people in Zurich. But I would say, Niels Bohr was very interested in our work on nuclear photo effect, and so this was the reason I knew Niels Bohr quite well. And I don’t know whether –- it was twice I discussed with him, and of course he was interested in the nuclear photo effect. He was very interested.
Weiner:Did you go to any of the Copenhagen meetings?
Gentner:No. Only later.
Weiner:Later, after the war?
Gentner:After the war, yes. Before the war, I had never been there. But I met Niels Bohr, because when I saw him in the United States I knew him quite well and — ah, it was in Paris also. It was in ‘38 in Paris. Yes, I have still a picture of sitting, me down and then he sits a little higher. I don’t know if you know this picture from Paris.
Weiner:I might know it. You weren’t at the Galvani meeting in Italy in ‘37, were you?
Weiner:He was there at that one too.
Gentner:‘38 I was at Paris at the meeting.
Weiner:That’s when your work was coming out a lot too.
Gentner:Yes. Because we had a famous dinner, and then Bohr, Pauli, I remember.
Weiner:But what you’re saying is that there were very few visits of foreign scientists to Germany, and very few visits of yours outside, although you did go to Paris and Zurich.
Gentner:Yes. But you had to get always a special permission. And mainly it was difficult also for money reasons.
Weiner:What about the overall development of nuclear physics in Germany in that period, ‘35 to ‘39? Did you get a feeling that there were things developing elsewhere?
Gentner:In Germany? Yes, there was certainly Harmon Beite in Berlin, and Debye in Berlin, and there was some work going on with Hoffman in Leipzig, not very important work, I would say. Not — it is not too much yet, a little. We did a little work, but only one man. I mean, the group of people working on nuclear physics was I would say nearly only with Bothe here in Heidelberg, and Maier-Leibniz, and I was together with Maier-Leibniz and Fleischmann and we were here all together. In theory — yes but not experimental physics.
Weiner:I meant experimental. Then the decision was that perhaps Germany should have a couple of cyclotrons. Did anyone have in mind where they would be? It was pretty obvious that one would be here.
Gentner:Yes, and the other one would be in Leipzig. This was the idea.
Weiner:Was Heisenberg in favor of it?
Gentner:No, Hoffman. Completely separate.
Weiner:There was a man Grossman.
Weiner:He seemed to have an interest in a cyclotron. In May of ‘39 he writes to Cambridge saying he’s interested and he mentions a Dr. Fritz Petrzilka in Prague was also apparently interested. Do you know if anything happened?
Gentner:No, apparently it didn’t. Grassman —
Weiner:— he was an engineer.
Gentner:He was an engineer, yes, I remember. I remember him. But Petrzilka I think he was in the German university in Prague?
Weiner:I think he ended up for a while in Cambridge because I remember seeing his name on a —
Gentner:— yes, I remember his name also.
Weiner:But as far as you know nothing came of that.
Gentner:Nothing happened, no. There were a few small instruments and some very few ones, but certainly not important things in Germany in this field.
Weiner:Do you remember what arguments Bothe used, or any others who had any influence, regarding the need to build a cyclotron? In some places it was argued, medical uses, because you could use isotopes and so forth. In other cases it was the simple energy argument. Those are the only two arguments I know of that were made anywhere, and I was curious, you know, what argument you made.
Gentner:I could perhaps find out, the letters from Bothe to the Notgemeinschaft asking for the money. Perhaps you have it still. It is possible. I don’t know, but I could ask here downstairs, the man there, because he was still here and Bothe was here and he knows about the letters. I think, because I gave a lecture, you mentioned this lecture, in Bonn, about the history of cyclotrons, and I mentioned in this time also some things about our, Germany’s cyclotrons, and I think he told me, his part of the correspondence with the Notgemeinschaft.
Weiner:Fascinating, because I have seen it in other countries, you know, the letters applying for money.
Gentner:Applying for money.
Weiner:And it is interesting to make a comparison. I’ve studied Lawrence’s and Bohr’s letters. I know the story a little bit in Italy and in other places in the US. So it would be very interesting.
Gentner:The reasoning for applying for money, yes.
Weiner:Well, let’s leave it as something to do. I’ll make a note to remind you.
Gentner:I could find out later, to find copies for you. I could just write it down over there.
Weiner:You say you wrote to Fiske. What was the month you went to the US/ ‘38?
Weiner:How long did you intend to stay?
Gentner:As long as I had money. It was never easy for me. I did not get the permission to stay longer, because my wife was in Switzerland at this time, and she went to Switzerland in the meantime. She was fearing that there would be a war, and I could not get back, and we would be separated by the war. So I went back and met her in England. She came from Switzerland to England and I met her in England, on the way back in England. So I arrived in the middle of December in New York, and then Jim Fiske took me to, first to Boston, then to Concord. I was living — his father-in-law was in Concord, had a big house in Concord, and I was very nicely accepted there and it was very happy, because this way I got trained in American language. I didn’t understand anybody then I arrived. When I arrived in New York I remember only that I couldn’t understand. You see, I learned English from an Englishman, only as the English teacher, and when you just arrive — and at this time, you never saw Americans before, and you never heard American. It’s completely different. The first few days I didn’t understand a word.
Weiner:Especially New York.
Gentner:So I was very happy to stay for a week with the family of Mr. Fiske, and so got trained. At this time I saw also and I met Van de Graaff in Cambridge. Fiske arranged all these things.
Weiner:By this time they were building a cyclotron at Harvard.
Gentner:Yes. I saw in Cambridge, in Harvard, the cyclotron, and this was all very nicely arranged by Jim Fiske. He was very nice to arrange all these things. Because you see, at this time, I had the idea not to go back to Germany. And Jim Fiske had got a position as professor in North Carolina, as —
Gentner:Durham is one, and then there is this other place, smaller university –-
Gentner:Chapel Hill, yes. And he just became professor in Chapel Hill at this time, Jim Fiske. On my way back from Berkeley I went to Chapel Hill to give a lecture there, and he told me that in the meantime he had difficulties with the head of the department and there would be no position for me in Chapel Hill. So finally, there were so many refugees at this time coming over, and people were feeling they should do something to help. It was all so difficult for the refugees in this time, very difficult. Very difficult. It was still the time when there was the feeling of crisis in the United States, and they were all thinking of the time when they had no position, two years before, talking about these difficulties, to get positions, and so I had the feeling that it would be not easy to stay. And so I went back finally, and my wife was in Europe, and so I went back to England, and wrote Cockcroft a letter. I went to meet my wife in England. We had friends of my father-in-law in England.
Weiner:Just for the dates, I want to get back to Berkeley but just for the dates, you say you returned to Germany April 8 from New York — I think you leave April 8 from New York and visit the Cavendish on the 16th of April.
Weiner:Well, let’s take your itinerary in the US. The first stop was the Cambridge area and you looked at the cyclotron work there, but that wasn’t really deeply looking, was it? Can you learn very much by a very brief visit of that nature?
Gentner:Oh yea, because Lawrence was —
Weiner:No, I wasn’t talking about Berkeley. I was talking first about Harvard, the Harvard cyclotron, that very brief visit.
Gentner:Ah yes, the brief visits. But all the people, I must confess, in the United States were very open to give me copies of the designs. Of the magnet, of the chamber, of the oscillator. I came back with a thick packet of copies of Harvard cyclotron and Berkeley cyclotron, the chamber and the dees, and where the difficulties were at this time, how to hold dees, the insulator of the dees, and different philosophy, how to connect the high frequency to the dees, and all this — today, you would say small technological questions. At this time they were quite very important. And they were very open, I must say. I was astonished at how they were open at this time. When you came over, it was a time of (?), and yes, they had seen a lot of Germans, but this was still a time of — an important thing when a German arrived, or an American arrived here in Heidelberg, not so often. Then I remember well, when I arrived in Berkeley to see Lawrence in the morning, and he said to me, “Oh, this is nice, I’m pleased to meet you here but before you take a seat, you have to see the head of the department, because we go later for lunch to the faculty club, and if he sees somebody he doesn’t know, this is impossible for me. We have to go at once to see him.” Today it would never happen, things like this. Birge at this time was head of the department. I mean, it was certainly something special, specially to see a German who was not a refugee. They were used to seeing some Germans who were refugees, but they were not used to Germans going back to Germany, just as a German. It was difficult because after a short time, you had always to have political discussions.
Weiner:Did you find curiosity or animosity?
Gentner:Sometimes also animosity. Quite important animosity, I remember very well. But because I had some friends in Harvard and MIT, it was easy because Jim Fiske introduced me there, so I found everywhere open doors, and he sent letters to Rochester. To Chicago I had very good letters to Compton and to also people in — I had some personal letters from Germany to people in the States, so I used all the time, these letters in the pocket.
Weiner:Just to reconstruct your itinerary, you went to Cambridge, Mass., then you went next to Rochester.
Gentner:Rochester, yes, also I went to Albany to see the people in the laboratories of General Electric. Then to Ann Arbor.
Weiner:Rochester first before Ann Arbor?
Weiner:Rochester, Ann Arbor, Chicago.
Gentner:Yes, because I was in by train. This Jim Fiske, I bought a ticket, and I remember it was a ticket like this size, and a round trip ticket through the States, going through Chicago — there was just a new train from Chicago to Berkeley. I went to Portland, Oregon, because there were some relations, not many, I saw some people. Then from there I went down to Berkeley.
Weiner:Did you go to Wisconsin? You didn’t go to Wisconsin?
Weiner:To see what Raymond Herb was doing?
Gentner:Yes. Wisconsin, they invited me from Chicago. This was not foreseen, but when I came to Chicago, and I was with Compton, I think not Herb but a theoretician, also a refugee no, he was longer already in the States, but not an American —
Weiner:Gregory Breit was there.
Gentner:Breit, that’s right, Breit. Breit was there, and I met him in the house of Compton. I had a letter to Compton and he invited me for the evening. And then Breit was there just by chance, and he told me to come to Wisconsin. So I went to Wisconsin and saw Herb give a lecture, always the same lecture on nuclear photo effect.
Weiner:That seems to be of interest.
Gentner:He was interested to hear about this nuclear photo effect work. And then I went back to Chicago. Then I got this train. This time the train was starting, this fast train to Berkeley and Oregon.
Weiner:When did you get to Berkeley?
Weiner:How long total time did you have in Berkeley?
Gentner:Oh, January, February, March, three months, something like this.
Weiner:Were you at Berkeley when the fission business occurred?
Weiner:That must have been exciting.
Gentner:Wonderful story. It was a story I told some people at the Bunda. They were very amused. I was standing on the desk of the cyclotron when Lawrence came — this was a telegram. He got a telegram from Washington. I think it was from Tuve. Tuve sent him a telegram saying that Bohr arrived and told something about fission of uranium by neutrons, and that they’d tried out this, and they’d found also some big kicks in the amplifier. And then I was staying there, and then Oppenheimer was reading with me the telegram. He said to me again, “Do you believe this story? I cannot believe it.” And he went out. This was a Monday. Monday afternoon they had all the seminars, and all the machine time distribution for the week. Then also some seminar about new things, you could tell what you saw. Things like this were discussed. And Robert Oppenheimer came and said, “I will tell you something. I thought a little about it.” In the meantime, yes, in the afternoon I was sitting with Green — he’s now in Brookhaven, yes, one of the important people. Quite an important man. Building apparatus. He had an amplifier, and by sitting down together at the cyclotron to look with uranium oxide, and in the ionization chamber to get big kicks. And we saw the big kicks. And Lawrence came in and we told him, “You see the big kicks,” also the telegram. And then he said to me, “Yes, you see, Gentner, we can repeat all important experiments half an hour later here in Berkeley.” (laughter) — this artificial radioactivity. I could not — because everything was radioactive already.
Weiner:Lawrence, that’s very interesting.
Gentner:And Oppenheimer — five hours after the telegram — he was in the meantime walking around in the campus, and gave a seminar, and he understood what was happening. This fission is certainly a product of course, of any neutrons, and (?) come a neutron out of the end of — He said, “There could be that there is a chain reaction because there are too many neutrons, if you get fission there must be some neutrons left, and these neutrons would certainly go out from there, and then you could perhaps, if you have a certain amount of uranium you get a chain reaction.” Just walking and thinking. He was always very good at this.
Weiner:That seminar was the large group?
Weiner:The normal Berkeley people plus the visitors. Was there much discussion?
Gentner:Yes, certainly. I worked in Berkeley mainly with Segre at this time…
Weiner:You told him something about the ionization —
Gentner:Yes, because I found out that they had no calibrated ionization chamber in Berkeley, and this was also one reason why they could not discover things, because they never knew if this is a big effect or a small effect because they had no calibration.
Weiner:They just had a whole lot of detectors?
Gentner:Yes, you had a certain room, some ionization chambers, and you did chemical work, look what products you got out of cyclotron, but you never knew really if this is 1 Curie or a milli-Curie. So I found out — I talked with Segre about this end I told him, for the short time, I could like to do something, so I told him I could perhaps calibrate your ionization chambers, do something for you.
Weiner:Which of course was extra, this wasn’t what you were trying to do —
Gentner:Yes, certainly, but you learn only in working. You cannot stay around the whole day.
Weiner:In working on the cyclotron itself, who did you associate with mostly? Green you said?
Gentner:Yes, Green, and then the people at this time, you know the picture, Cooksey. I went out with poor Cooksey many times. Cooksey was in this time building his 37 inch cyclotron.
Weiner:The 60, I think.
Gentner:The 60 inch cyclotron. And I went usually with Cooksey around to visit the factories, because he was really nearly every day he went around to San Francisco or somewhere else, small places, different places where they built parts of the new cyclotron. Every week certainly he looked what they were doing, how far they are and he knew I am interested and so I was very pleased to see something of the country, to see also these factories and see what he did. So he was very nice and I learned a lot from Cooksey. He took me around and was very nice. I look through the papers now for this speech in Bonn and I found some funny pictures of Cooksey he gave to me, and one evening we were in with Lawrence and Cooksey in San Francisco. He gave me a special dinner. It was just the World’s Fair in San Francisco at this time, a special park.
Weiner:Well, it had been the World’s Fair the year before. 1937 I think they had it, and the park remained.
Gentner:The park remained, and in this park —
Weiner:I’m not sure what the year was but I know the park remained.
Gentner:In this park, we did some pictures, and when I looked through this I found the strange pictures from this time. Here is the famous picture of the Berkeley people. You remember, this is very famous.
Weiner:Are you on this one?
Gentner:No, it was just taken before I came. You see this —
Weiner:“Believe it or not, to my friend Gentner, Ernest Lawrence.” Now what is the picture?
Gentner:This was one of these new photomatic. This was just new. This was left from the World’s Fair.
Weiner:Yes, the machine where you put in your coin —
Gentner:— your coin, and then you are sitting there, and you got just the picture out. It was completely new in this time. This is Cooksey also in one picture.
Weiner:“Souvenir of an evening away from the lab.” “With best regard to our German visitor and friend Dr. Gentner from Donald Cooksey.” Golden Gate International Exposition. It’s Golden Gate Park now.
Gentner:Golden Gate Park now, yes. This was very nice, I got all these pictures at this time from American pictures, pictures from the instruments in the different places I’ve been.
Weiner:You mean technical photographs and things.
Gentner:Yes, technical photographs, very technical photographs. I have also this picture from Berkeley. I used it. Here we are. Some people — lots of people also from the time there. This is not so interesting for you.
Weiner:Perhaps if I have time later I’ll take a look at them. Let me ask more about Berkeley. After this very interesting event with the fission, this was all in one day?
Gentner:This was a paper I had. Thornton was there in this time also. He is sitting here at the pump, here.
Weiner:About a year ago I was in Berkeley, and (?) is very interested in Lawrence. Those were particularly interesting. I’ve never seen those. Are these ones that you took?
Gentner:I do not remember. I found these pictures — you see what I do, I’m not a very efficient man. I put all the photographs I get in one box, and have an extremely big box, all photographs, and now when I had to give this lecture, I looked through to find them and found these pictures here from Berkeley.
Weiner:We’ll put them back in the box.
Gentner:You see, there’s a certain start of a new order here.
Weiner:Was there subsequent discussion and work while you were in Berkeley on fission, on the follow-up?
Gentner:Oh yes, we worked on quite a lot of fission with McMillan.
Weiner:Did you do some too?
Gentner:A little. I helped the man to build this foil, and he, we were interested to have a lot of foils of thin uranium foils to put together and to look how far these products are going through, or to have one uranium plate and then foils, to find in the foils radioactive products and measure the radioactivity of the foils, to see about the range and what kinds of products you get with different ranges and what chemical products there are and so on, and the chemist in this time was Seabrook.
Weiner:Abelson was doing some work too, wasn’t he?
Gentner:Abelson was also doing work, yes. Because there was danger all the time, from morning to evening in the lab, and then McMillan and then — otherwise I think they were not, McMillan was certainly not married, because he came always in the evening. We were sitting, and Cook went back to the lab also.
Weiner:So during these several months, you were using the cyclotron to become acquainted with general techniques. You were calibrating the ionization chamber which was something new. You were involved in experimental work in the fission thing. What else? Was there anything else you had time for? Did you do any of your own older gamma ray work?
Gentner:No. No, I was just — I was interested to — I was interested also from my older time in biophysics, when I went with John Lawrence also to this hospital in San Francisco and looked on the insulation he hid, and in this time he used already phosphor and iodine for medical purposes, and then with Sloan, Sloan was there and he had built an X-ray instrument in the John Lawrence Hospital for one million volts, something like this, quite amusing instrument.
Weiner:This was already old by this time.
Gentner:Oh yes. Very interesting. And so I can remember I can — I did also I think a week or so skiing with some people in the mountains. We sent skiing in the park. Segre I worked with mainly in this time, with Segre and — I was with McMillan in this time — you see, I know, I remember very well, Madame Woo. She did her doctor’s thesis in this time, on internal (?) . And because I was interested in gamma rays and things like this, I know her from this time, because I talked quite a lot with her about her work on internal (?) . She used I think first four targets, the first four, to measure the internal (?) for her doctor’s thesis. Also she was a charming girl, at this time. So I know her quite well from this time, helping her and discussing with her. I wasn’t too interested to publish things, so I never was perhaps — not so very much interested in publishing. I was always well pleased to do something.
Weiner:Other than these seminars when the theorists would come together with the experimentalists, did you have any contact with them, with Oppenheimer and so on?
Gentner:Oh yes. Quite often, yes, with Oppenheimer, and he remembered also me very well after the war. He was the first man to invite me after the war to Princeton. I think ‘49 or something like this. (off tape)
Weiner:I have lots more questions. I don’t know how much endurance or time you have.
Gentner:I usually go home some time. It’s quite amusing for me to remember myself, things I did not talk about.
Weiner:We’re taking so many years to put this small amount… Let’s say that we’re resuming now after a very pleasant interval for good food, and now we’re sitting at your home by a warm fire instead of the cold (?). We were talking about Berkeley, and you had made the point that in addition to learning about cyclotrons by actually working with it during the actual routine of the day, you were taking on other responsibilities voluntarily, calibrating an ionization chamber, working with the early fission experiments, going with Cooksey to factories and shops where cyclotron parts were being made, seeing some of the scenery, working with other people there on some of the work, on internal and so forth. And then you mentioned that you did have contact with theorists as well. I wanted to get into something of what you observed of the life at Berkeley, in terms of relationships of people, how they worked in the lab. Of course, you mentioned on Monday there would be a seminar and assignment of machine time.
Gentner:Yea, a meeting. Yes, a distribution of machine time, yes, over the week, yes.
Weiner:Let’s talk about that. Who would make the decisions? What would the input be to this process?
Gentner:It is not so very different from today, I would say. It was just all the people asking for radiation. For instance there were places, several special places around the cyclotron where you got more neutrons or less neutrons and so on. There were some important places where you could put some (?) with the neutrons, and then it was asked, who likes to have the radiation, so he could put his chemical products or something like this. There were good places. And then there was the point of, who gets the beam and what should be put? There was much irradiation inside the cyclotron. In these days you were interested to find new isotypes. It was like the chemists like to discover elements. At this time everybody was interested to be somebody who was the first to discover iron, I don’t know, 56, or something like this, and the other one, everybody had his specialty, and so he tried to get irradiation. Also, the other people were interested to measure the beta spectrum. I would say less. It was more or less, in Berkeley, I had the feeling that the people looked about to big — they were looking at big effects, and mainly discovering new elements. But Segre for instance he was interested in this time in techniques, and so these few elements which were not discovered in earth, and in the open places in the periodic system, so he was interested to find elements and isotopes of this, or something was going to do the chemistry. Segre was a very broad physicist here and chemist and everything he likes to do, so I was very pleased to work with him because I like also to do this, that and the other, different things, and not to stick always to the same problem.
Weiner:All these things were centered around the cyclotron as the main source of — (crosstalk)
Gentner:— yes, yes, very —
Weiner:— materials, if you didn’t do direct experiments with it, it made other experiments possible, a central process.
Gentner:Yes. It was a little also, Brode was there. He was there. I was interested in cosmic rays, so I remember very well the discussion I had with him on cosmic rays. He was always interested in cosmic rays. And there was also somebody who did classical spectroscopy.
Weiner:Harvey White and Jenkins.
Gentner:Jenkins, yes, Jenkins I remember, we also had a wonderful trip around the Bay and San Francisco. Lawrence said, “Spring is coming and we have to get on the Bay, have a wonderful motor boat,” and the people told me the motor boat doesn’t run always. So it was on Sunday morning, and then we went down to the Bay with a new acoos(?), to start the motor of this very heavy work in turning this machine. We got it to working, and then we went out to the Bay, drinking, so the children were drinking with us, and then in the middle of the Bay the motor stopped, and we couldn’t get the motor running again. The waves were quite high and so the boat was — the children were afraid, and — Finally we got a sailor to bring us home. I was with Lawrence and Jenkins. I had the feeling then, in Berkeley it was not as so — because in these days you had really relations with all the people from the faculty, with nuclear physics and cosmic rays and spectroscopy and chemistry.
Weiner:How about people from the chemistry department itself? Did you have much to do with them?
Gentner:Seabrook. He was always interested and came often to the — he was also interested in irradiations and so on.
Weiner:You spent most of your time physically at the radiation lab, distinct from the rest of the campus.
Gentner:Yes. It wasn’t so far away.
Weiner:No, but it was separate quarters.
Gentner:Yes, certainly, but you went to Faculty Club. It was not so busy and it was not so big, so at the Faculty Club I met also the other people, all the other faculties. I had also some discussion I remember with refugees and people from other faculties, asking me about the German association, and then I had to have in the evening because I went also in the evening to the Faculty Club. I was living in the International House. So in the evening I was also staying at the Faculty Club. I remember it was always — at this time it was not so easy, because I had to answer questions about Germany which were not always easy to answer. Not so easy to answer, how the situation came and what it means and so. I had also relations, I had to go once to the German consulate in San Francisco, because I had to go there to tell what in Berkeley and so. But this was a very nice man and he said to me, “I will arrange everything. I will tell you, better to go to Washington to your embassy to see” I don’t know, Mr. so and so, “because he writes a report about you, and better before you are leaving you go to tell him what he should write, this report.” You can realize, in these days, it was a special person. It was not the time of the tourist as today.
Weiner:Within the discussions at Berkeley, did you find that there was any special point of view there that was different from other places?
Gentner:Oh yes. It was different. It was different in this way. First, what made a big impression on me was this, as I told you, some people there were always talking about Japan as a danger from Japan. I remember that they told me, all this water coming under us in San Francisco comes from the mountains, and if you just have a nice bomb you can make all this water perhaps exploding and then because the Japanese could always come and get explosions in these water pipes, you would be without any water. This made a big impression to me, because I saw that they were talking about this, perhaps what we called later the —
Gentner:Fifth column, that might do this kind of thing, completely different from New York and Boston. They were only talking about Europe.
Weiner:But the political points of view?
Gentner:They were also different, I would say. It was — I had the feeling almost a few people, different people also, very different people, but with some people they were not so much against the Fascists and so on, and other people they were completely against. Other groups people had different opinions about the situation. They said, “Italy and Mussolini are not so bad, anyway he makes order, does quite a good work in Italy.” I remember very well, also at the Faculty Club there were some different groups and then different feelings about this political situation in Europe.
Weiner:These may have existed other places in the US where you visited but you weren’t there long enough. Gentner It’s possible. So I had better, I had more discussions, and there were also some I don’t remember the name, but I think it was somebody from, some professor of Germany, and he was always interested, in the evening, when he got me to talk to me and ask questions about the situation. He was very much against all this Fascism and things like this, but he was very interested to get really information why this happened in Europe, in Italy and Germany, and what would be the future of all this.
Weiner:It seems to me it would have been very interesting, having you there at that time. It presented a real opportunity for this kind of questioning and probing and discussing, which ordinarily wasn’t available.
Gentner:Yes, because I was in a certain way, I had the feeling at this time, also in Berkeley, I was treated differently from the refugees. They came also at this time. But because the refugees were looking about the place, and were interested in looking around where they could find the work to do, and how to save the situation. They knew from me that I was just there as a normal guest. This way I would say I was probably better treated and they were more interested to discuss with me in a certain way.
Weiner:Also you had fresh information.
Gentner:I had fresh information. I just came from Germany. Certainly that was also an important point.
Weiner:You know, that’s quite different. It would be a unique point of view that they would never otherwise have an opportunity to get.
Weiner:Did you visit Cal Tech as part of your work there or was it after you left Berkeley?
Gentner:After I left Berkeley, I went. I know I went only to Stanford from Berkeley. Felix Bloch was not married in this time and he came once to Berkeley and invited me to come to Stanford. I was in his home in this time. I remember he was not married, and he had a big bottle of California red wine and we were drinking.
Weiner:People do that even when they’re married you know.
Gentner:Drinking red California wine, and talking and asking questions, because Felix Bloch was also interested to get news from Europe. He asked me about people. In this time you were asked also, “How is Heisenberg, would you say? Mr. X is he a Nazi or is he not a Nazi? How he comes along with political situation?” It was not only physics. It was quite a lot of this kind of question. It was always discussing to what group he belongs and things like this, quite important; mainly for those people they were ones related to the Copenhagen circle. Of course they were acquainted and were interested to hear what others were doing.
Weiner:You mean like for example Heisenberg and Schrodinger.
Gentner:Schrodinger and all these people. I met Weisskopf. I had a talk with him also. He took me to the lakes. Oh, he was very interested to hear about different people. But I had also a very different people — I met James Frank in Chicago. I knew him only from just from seeing. I never spoke to him. So I just saw him going to the institute, and I asked him if I could talk to him a moment, and he said, “No, I’m not interested to talk to you.”
Weiner:Who is this?
Gentner:James Frank. I said to him, “But I have some people, they give me regards to you, and I thought you were perhaps interested to hear about them.” “If you like, you could come up to my office,” he was extremely official and full of problems. Many people were just accusing me, accusations and accusing me about the situation in Germany and telling me. ‘You are responsible for the situation in Germany.’ You didn’t do anything against this. This is why we have the situation, in Germany now. You of the young generation, you didn’t do anything against it. You didn’t fight against it.” So you had some people — so it was sometimes a little difficult situation. There was quite a lot of discussion at this time. Very much discussion.
Weiner:Yet there were at the same time people who had a need for information.
Gentner:Yes. They were interested to hear about friends, what they were doing, how they were living, how you can live in Germany in this time. So it was a strange combination of interest in information, and the other side of the — yes.
Weiner:Let me ask about Stanford. When you went there, there was the cyclotron project under way. Did you talk about that?
Weiner:Before the war with Hanson I think.
Gentner:Oh yes, possible, but I was mainly together with Lauritsen and Fowler.
Weiner:That’s Cal Tech. I’m talking about Stanford.
Gentner:Stanford, yes, sorry. No, I was not very long at Stanford, and I gave my usual seminar on nuclear photo effect, and I was talking I remember mainly with Felix Bloch. Felix Bloch — no, I don’t remember. I remember something about the relations between Stanford and Berkeley. I remember I had the feeling that they were not the best relations. I remember that some strange feelings were between those two, but I can’t remember exactly what it was. It was perhaps nuclear physics.
Weiner:I know two positive things. One is that there was a joint colloquium or seminar between Bloch’s people and Oppenheimer’s people.
Gentner:Yes. This is — like this, that’s the reason he came over and he saw me and he liked me to come to Stanford. Usually, I don’t know, a fortnight or something like this, he came to Berkeley to have seminar with Oppenheimer together. This worked very well.
Weiner:The other is that he collaborated on experimental work with Alvarez(?) on the magnetic moment of the neutron. That was before, ‘38. Anyway, so Bloch himself –-
Gentner:— no, no, Felix Bloch, he came always to Berkeley. Yes, he had very good relation to Berkeley. But I don’t remember exactly. I had only a feeling that in some experimental groups there were but perhaps it’s not so important. I don’t remember.
Weiner:On the Cal Tech visit you say you also saw Lauritsen and Fowler. Fowler would have been young and Lauritsen would have been a very senior man then.
Weiner:They had a high tension setup.
Gentner:Two or three high tension setups in the hall.
Weiner:Is that mostly what you went to see?
Gentner:Yes, because I knew very well, the work, and this was the main reason I wrote them a letter and they invited me to come, and then it was very nice. Lauritsen’s home was a very nice home. They were very hospitable. They took me also around to the desert and things like this, trips. I met at this time, I had this relation to Delbruck was there. A long hiking some day with Delbruck and some people, and a long discussion, if you should go back to Germany or not if you should stay in this United States, and Delbruck had, at this time he was also not so sure about all this situation. I saw him later and then we talked about this. And this was still discussing, if you should just if everybody should leave Germany, or if you should go back and discuss with the people and work against this situation, or if you should just leave and say they should do what they like in Germany, or leave? Because Delbruck was also not so sure at this time if he shouldn’t go back.
Weiner:Well, he left late.
Gentner:Yes, he left late. It was not so long that he was in — he’d just stated the biological work. I knew him from that time because he was once working on the scattering of gamma rays. And this special work he did, about the special kind of scattering of gamma rays of the nucleus, which was very difficult to prove because it was a very small effect, and much later it was really found that there is something of this kind, of Delbruck’s scattering. It was a very small effect. And he worked on this quite early in Berlin, when he was in the house of Lise Meitner.
Weiner:So the contact with him was because of similarities in background. There was nothing scientific at the moment when you saw him.
Gentner:No, because he was just started already in biology and then he was no more interested in physics. No, it was a more — physics I discussed with Fowler mainly. He was about my age. Fowler’s about my age. And he was (crosstalk)
Weiner:Lauritsen... Copenhagen then?
Gentner:No, he was in Cal Tech then.
Weiner:But he must have just returned, or hadn’t gone yet?
Gentner:I think he was working on his thesis.
Weiner:Could be. He was in Copenhagen when the war started.
Gentner:Oh yes, so he was still there, I remember. Of course he I remember was also a — I came to —
Weiner:How long were you there?
Weiner:You went back to Berkeley?
Gentner:No. Then I went on my trip with the train to the South and to New Orleans by train, —
Weiner:— sightseeing —
Gentner:— very nice train, and then I went up to Chapel Hill, from New Orleans, to see Jim Fiske in Chapel Hill.
Weiner:There was no physics in New Orleans that you looked into?
Gentner:No. I was only on the famous Mississippi steam boat with this behind — the Mississippi — (stern wheeler?)
Weiner:I think they’re still trying to keep one there.
Gentner:They had one of these boats, yes.
Weiner:Then the next real scientific expedition was in Washington, on nuclear fission?
Gentner:In Washington I saw Gamow and Teller, yes. And the German embassy. (laughter)
Weiner:What about Tuve and his setup?
Gentner:Tuve, yes. It was a strange institute in this time. I don’t know who was the director.
Gentner:Yes. When I tried to enter this institute, I was asked first to see the director. When I had to have an interview with the director, and he asked me about my political intentions and things like this. It’s very strange. This was the first time in the States somebody asked me about my political meanings and things like this. Later I learned that he’s reading all letters arriving at the institute toward me. When he gets a private letter, then Fleming opens the letter. He opens all letters in the morning and reads all letters. Then he distributes open letters to his co-workers. Other people had to first get a permission from the director to enter the institute. This was the first time, the only such institute I saw in the United States.
Weiner:Anything that went out, he’d insist it went out over his name or with a covering letter. “Mr. Tuve wants to know so and so.”
Gentner:I remember that very well, because that happened with Tuve. There were some strange things in Washington. Also one day I got a taxi, and opened the door of the taxi, and I heard the voice of Hitler speaking. In the taxi, yes, on the radio, yes. I think I was just leaving, before — Tuve was there, and so –-
Gentner:Hofstad was there, yes, Tuve and Hofstad. I don’t know, Odd Dahl left perhaps already. I knew him later.
Weiner:The experimental setup there was something you wanted to see.
Gentner:Yes, my main interest was — because they had about the same insulation I had here in Heidelberg. It was very similar. And they were also working on similar problems about, I was mainly interested in this, reactions of, P gamma reactions, and they were working on this problem, and I had some measurements done. They were not completely the same results as they had — but I think I was right and told them. We had very nice discussions, also with Gamow and Teller.
Weiner:At this time they were at George Washington.
Gentner:Yea, they were there together in Washington, yes.
Weiner:By that time Gamow’s interests were shifting to astrophysics and cosmological questions.
Weiner:Let’s see, from there, was it then that you visited Columbia, on your way out of New York?
Gentner:Yes, it was the final stop.
Weiner:Dunning by that time —
Gentner:— Dunning, yes, Dunning, he was one of the few Americans who visited here, Heidelberg. Dunning came here to Heidelberg —
Weiner:— 1935, I think.
Gentner:Yes, ‘35 he came here, and I knew him from this visit here in Heidelberg, so I went to Dunning.
Weiner:I think that’s where, I’ve seen letters he wrote to Pegram — you must have met Pegram?
Gentner:Yes, yea, right, Pegram.
Weiner:He described his visit, and I think he mentioned that there was interest in the cyclotron, in Heidelberg, I’m not sure.
Gentner:Oh yes, it’s possible. It’s possible. I know that he came, it was I think ‘35 he was here, in ‘35, and he was (crosstalk) — Pegram, I don’t know from where perhaps, but I had certainly a letter from Pegram and some regards to give him, so I saw Pegram and mainly Dunning I think at Columbia. Because he was back, and it was just by chance in the hotel, I don’t know, I was staying, I came to, I was staying at the Commodore I think and I was in the hall of the hotel. I remember I saw Ellis Lawrence. He just came to New York, I don’t know, he told me that he had to do something. And then he said to me, “You know, there is Niels Bohr, and I have dinner with Niels Bohr, wouldn’t you come with me?” And in this way I had, before I left New York by boat, I had this dinner with Ellis Lawrence and with Bohr in some restaurant, I don’t remember where, and I had a long talk with Niels Bohr about the political situation in Europe and Germany. He was very interested and we had a long talk about this. Also I knew him from the tine before, from Paris, and I saw him also I think at Cambridge or at Zurich also. I think I saw him twice or three times, discussing with him the nuclear photo effect.
Weiner:His attitude was somewhat pessimistic?
Gentner:Yes. More pessimistic —
Weiner:Lawrence, on the other hand —
Gentner:Yes, he was always more optimistic. Voice: He had an optimistic temperament.
Gentner:Yes. This wasn’t on my trip when I arrived. This was on my trip back. We talked about this already, when I arrived, and Jim Fiske arranged this. But on the way back, before I left by boat, it was this last dinner with Lawrence and Bohr in New York here.
Weiner:By that time Lawrence must have been in New York negotiating for the big cyclotron.
Gentner:Yes. I don’t know exactly. He was very busy at that time, I remember only, he was always talking about the new cyclotron before that, before it was running. For the 60, the magnet was built. He was talking already about the next on, long before this one was running.
Weiner:They’d already built the great telescopes, the 60 inch and the 100 inch. Before the 100 inch was working he was talking to the Rockefeller Foundation about a 200 inch. That must have been on the tail end of Bohr’s trip too because he had been in the US since about January and he must have been returning.
Weiner:After the fission thing, was there any discussion about that? Because by that time Bohr had brought the news.
Gentner:Yes. It was after he sent the telegram to Berkeley. This was in January.
Weiner:Right. That was as a result of Bohr. By this time the Hahn-Strassman paper must have been published and the Frisch-Meitner paper as well, also all of these other experiments, Tuve did it and (crosstalk) Dunning and (crosstalk) —
Gentner:…yes, all published, all published.
Weiner:Was there any discussion of that, in terms of whether this was still occupying people as an important scientific problem?
Gentner:I can’t remember what we were discussing. I remember from this evening only the political discussion we had, not too much science.
Weiner:I think Bohr had been working with Wheeler on the mechanism of fission, theoretical.
Gentner:Yes, the famous paper, Bohr and Wheeler.
Weiner:It was just about that time.
Gentner:But Bohr’s real paper came out a little later.
Weiner:Yes, that’s when the correspondence with Bohr — things take a while. Well, then, I saw your letter from Berkeley which was written the 28th of February to Cockcroft.
Gentner:Ahah, yes, I remember, I wrote a letter to Cockcroft to see Cockcroft.
Weiner:He was the one. You were saying you were traveling through the US to see some work with the cyclotron and high tension setups, and you returned to Germany, I guess you meant leaving April 8th from New York. Then from New York you did go to England.
Gentner:Yes, I met my wife in England, yes.
Weiner:Did you go directly to Cambridge?
Gentner:No. We came to the — she came to the boat, and had some difficulty to find me on the boat. A lot of people on the boat.
Mrs. Gentner:Yes, because the boat didn’t go to Cherbourg. It was already ... (inaudible) and so the boat didn’t go to Cherbourg. We had a tender from Cherbourg to the boat.
Gentner:Cherbourg, yes. Only very few people. We were on this big boat, and a group of friends — there were two big boats from Germany going over, and I think on the boat was place for two and a half thousand people.
Mrs. Gentner:We were going to Cambridge.
Gentner:And we were only 200 people on the boat.
Weiner:Coming back — deserted.
Gentner:We went to friends.
Mrs. Gentner:We went to friends, Gamlins.
Gentner:Gamlin, Dr. Gamlin’s, yes, and from there we went to Cambridge to see Cockcroft.
Weiner:By that time, was their cyclotron running? Yes, I imagine it was by that time. No?
Gentner:Oh yes it was, yes it was. But it was not in very good shape. And the high tension was working all right.
Weiner:They had two setups.
Gentner:Yes, but the one million was working all right, the two million was not working all right.
Weiner:There I guess you saw Feather, and Bretscher was there.
Gentner:Yes, Bretscher from Zurich. I knew him quite well because he was with Scherrer.
Weiner:Dee would have still been there.
Gentner:Dee was there, yes. I saw Dee. And Dee, Bretscher, yes.
Weiner:There was an Indian there at that time. I forget his name.
Weiner:No, someone less well known. Oh, that reminds ne, Bothe apparently was in touch with Cockcroft in September of ‘38 because at that time he thanked him for leaving the scheme of our cyclotron oscillator, for the kind hospitality of his laboratory and home, so Bothe apparently had already visited Cambridge, and — in September of ‘38 regarding specifically bringing back information on the cyclotron.
Weiner:Yes. He writes 9 September ‘38 so I assume he was there earlier.
Gentner:I can’t remember that. He read in the paper, in the letters in Berkeley, in Cambridge — yes, in September. … in December, you see, and he was, I think he was in this time, didn’t he go to India? He was invited to a congress in India, Bothe, I remember. And I have still a big picture of this size with a lot of Indian people, there somewhere Bothe somewhere and also some English people.
Weiner:That was the meeting that Rutherford was to go to but he died before. He was planning to go some time in ‘38.
Gentner:It could be that he was in connection with this Indian trip.
Weiner:I don’t know when it was. The letter is 9 September, perhaps it was August or something. The point is, so there had been some prior contact, so when you went —
Gentner:— he knew Cockcroft very well. And Cockcroft, yes, I knew him, certainly from the, also from Paris, Congress in ‘38, he was there, and I went once with Joliot to England in, you remember, I went to —
Weiner:Did you go to the London Conference?
Gentner:The London conference of ‘33 or ‘34.
Weiner:‘34. You went to that?
Gentner:Yes. (crosstalk) Because we were living –- ‘34.
Weiner:‘34, the conference was in October ‘34.
Gentner:In this time I went with Joliot to Cambridge. This was my first visit to England.
Weiner:Getting back to that, as long as you mentioned it, do you remember anything about that conference? There were a lot of people on the program. Max Born gave a paper which was not really nuclear physics, was more quantum mechanics, and Rutherford gave the opening address.
Gentner:This I remember very well, the program, because it was for me as a young physicist, it was the biggest impression to see Rutherford for the first time.
Weiner:I’m sure he made a dramatic impression. But did you think of the conferences as being especially significant in any way?
Gentner:I think so, yes. Just try to remember. I met a lot of people the first time I knew already from the literature, and so, I think it was also Goldhaber I met for the first time.
Weiner:He was at Cambridge?
Gentner:He was at Cambridge in this time.
Weiner:He worked on photo disintegration.
Gentner:Yes, photo disintegration. I had a long discussion with Goldhaber, and –- I remember very well.
Weiner:But the meeting itself, you didn’t present anything at the meeting?
Gentner:No. No, I don’t remember, no, no.
Weiner:Then on the return to Cambridge in April of 1939, first of all, how long did you stay there?
Gentner:Not very long, I think, one day, Monday or Sunday.
Weiner:Oh, I see. But you had a chance to look at the cyclotron.
Gentner:Oh yes, I looked at the cyclotron and the high tension and so on. I went through and Cockcroft was interested to hear what was going on in the States, because in these days, when you came from these places, everybody was interested to hear what they are doing.
Weiner:Cockcroft himself was here in ‘33 and ‘37 for that same purpose. On the cyclotron — for the same reason. Then it was quite clear that it was, back to Germany.
Gentner:We had to go to Germany, back to Germany, yes. We went back by boat to Hamburg. And then Bothe left. Then he was invited to the United States, and he left, after arrival. He left for Chicago. He was in the United States just before the war, after I came back.
Weiner:Was it to speak somewhere?
Gentner:I would say it was some, I don’t know what meeting, to a meeting he was invited, a special meeting.
Mrs. Gentner:He wasn’t there for very long.
Gentner:No, not very long. A very short time. Because it was the story about the (?), you remember this story with Bothe, when he came back and he told me that there is a possibility to go to Columbia University. He mixed up the different lines, the metro, and then finally he arrived in a completely different place, where he didn’t like to go. And I told him, “Yes, but in New York you have to look about the lights, different color. You have to follow different colors of so small lamps, then you get to the right line.” He said to me, “But I had not the time to look about for different colors.” (laughter) He just went up the wrong color I don’t know, Negro — yes, it was not very far from Columbia, if you come —
Weiner:Columbia’s in Harlem.
Gentner:In Harlem, so if you go too far —
Weiner:— you’re in the heart of Harlem.
Gentner:Yes. Something like this happened to him.
Weiner:So anyway, after your tour, where you had deliberately gone with the idea of carrying through the building of the cyclotron, then you came back with this good experience. What happened?
Gentner:Nothing. The war happened. The war happened.
Weiner:You came back in April.
Gentner:April, yes, it’s true, but Bothe left —
Mrs. Gentner:We went to Switzerland in August.
Gentner:In August, but before we had still, May, June, July here in Heidelberg. But Bothe was —
Mrs. Gentner:We came back, you came from America, and we knew there was going to be a war. We came back to Germany. Nobody believed us.
Gentner:Yes, it was very strange.
Mrs. Gentner:Everybody told us, what are you speaking about? Our Fuehrer wants peace. We were really badly looked at —
Gentner:— because all the people here (crosstalk)
Mrs. Gentner:— it was not being talked of, war, impossible that there might be a war.
Gentner:So in this time, I wrote this article which I showed you today about accelerators and high tension, summary.
Weiner:Would that include cyclotrons?
Gentner:Yes, also it included cyclotrons. There was also on Lawrence and his group, for learning about cyclotrons.
Weiner:When you send me that list I’ll be able to find it.
Gentner:Yes. So I think in this time, I wrote this article, after coming back from the States. We didn’t get any cyclotron. But then we went for the holidays in Switzerland in August, and when we came back the war started.
Weiner:How far had the cyclotron business gone? You mentioned that after at first disapproval, Notgeneinschaft, they said OK. Then industrial sources helped pay for your trip to learn about it. Then what would have been the next step necessary in order to actually start building one?
Gentner:We’d have to get some money to order the magnet and the building.
Weiner:Had they only approved in principle?
Gentner:In principle, yes. And I think it was in principle because the trip, my trip to the States, was paid by another source, you see. So they just gave some money to push this idea to build cyclotrons. But it was not really — the money for the cyclotron was not given.
Weiner:Was it possible to deal in a normal way with the Notgeneinschaft in those days, or was this also affected by politics?
Gentner:Yes, it was also influence in certain ways because there were certain, some people sitting there. It was, you see, also mainly this thing that fundamental research was not so recognized at this time and it was more applied physics. More money was given to applied physics and technological things than to fundamental research, and I have to look about these papers. Bothe was not very good in getting money. Bothe was not a man who he usually wrote really things, how they are and what he had thought about it, and he could not write a letter that he would like to have a cyclotron for medical purposes, if he liked to do some nuclear reactions. This was not possible for him. So he wrote always the truth, and this is also the reason why he never got money. I would say it was like this. You always had the feeling, he was not very good at these things, to write diplomatic letters.
Weiner:In the meantime no one else at any of the other institutes or universities in Germany pushed for money for a cyclotron? Of course you had no way of knowing at the time.
Gentner:Only Hoffman in Leipzig.
Weiner:He didn’t get it?
Gentner:He was not very strong.
Weiner:And this Grassman I mentioned –-
Gentner:— yes, but he was an engineer, and I can’t remember, he was related to the industry some way.
Weiner:The only thing I know is he writes with the title of engineer and from Nuremberg. The letter doesn’t indicate whether —
Gentner:Yes, I remember his name and that he tried also to push, but I don’t know exactly why he did this. Finally, it was — we went to the war and then, and then — we got this pilot(?) cyclotron.
Weiner:Yes. So there was not a single even construction start of the cyclotron in Germany before the war?
Gentner:No. Certainly not.
Weiner:That’s what I’d understood.
Gentner:It was a — ...was this in? We started work with Siemens on the cyclotron, and there was the idea that Siemens should build two cyclotrons, one for labs and the other for Heidelberg. And we had a fight with Siemens about this cyclotron because they, yes, they told me that they would not be interested to hear about my experience from the United States and all this, laboratories I saw, because they had their own ideas, and they would be more interested to get patents on the ideas, and if they were talking with me there would be later difficulties about patents. Very strange ideas. So I came back to Bothe. I discussed it in Berlin and I told him this story. I told him, I have the feeling if we really build our cyclotron with Siemens we never get a real good cyclotron and we never get the cyclotron as we like it. I would propose that our building ourselves the cyclotron, ask for the magnet, but not for the chamber and not for the high frequency. So we –- but this was an idea in war time. So we got only the magnet from Siemens. I was working on the chamber and the dees and all these things here in Heidelberg, and we got the high frequency from a factory in Munich, and we were putting all things together ourselves and we did not work with Siemens because I did not believe in those people.
Weiner:Were they going ahead on their own?
Gentner:Yes, but they never finished. Never finished.
Weiner:How far did the Heidelberg —?
Gentner:The Heidelberg was I think about one year, about half a year before the Americans arrived here. Because I was first in Paris, in ‘40, when the war started in September. In the winter there was no war. In the springtime, the real war started. In June it was finished, and I was sent with Schumann as an interpreter to Paris, to interview Joliot, and I think it was in July, ‘40. They asked him about heavy waters and about the uranium, and he should tell exactly where the heavy water is, because they found in the meantime in Norway all the bills from France about the heavy water they bought in Norway. They knew he had this, he got this new heavy water. And he told the truth. This was the strange thing. He told them he brought the heavy water to Bordeaux and that probably the water was on the boat to Great Britain. But they didn’t believe him. So when I saw him the evening, when we went out, he was very distressed to see me, and I was also a little, difficult situation, and when we went out, I let the people go out first, and then stayed a little back and I said to Joliot, “I have to see you alone. I have the evenings free. Couldn’t we meet somewhere?” (off tape)
Weiner:We haven’t been talking very long.
Gentner:Not talking very long?
Weiner:No, I’d say we have not been considering how much time we’ve covered. You say you suggested to Joliot that you meet.
To meet him, in a cafe on the Boulevard St. Michel. So I went back to the hotel, and I said, “I have to see some friends, to see the night life of Paris.” So I went to see Joliot in the cafe and told him that the reason why I just came to Paris, and that they told me that they were interested in the cyclotron and we could use the cyclotron perhaps for nuclear research work, and I asked him what he would say if I should come to Paris, and that if he would like to I would come, that I would tell the people that I was not interested, that I had some very good ideas but that these ideas could only be followed in Heidelberg, and then I could work in Heidelberg, on some nuclear research work. Then Joliot told me that he would be interested that I would come, because he decided to stay and not to leave, and would be interested to have some friend, that he could discuss with me about the situation, and “We’ll try to come back to Paris. I will do my best if you, the Curie, are also trying to convince the people it is best to leave the cyclotron here in Paris and do the measurements in Paris, about cross-sections and things like this.” This was the idea, to measure cross-sections of uranium for neutrons and things like this. And other, carbon, all these cross sections were very important in this time. Then we had a discussion with our military people from the (?) and because we were just in the first days of the war, here in Heidelberg all the people in the lab were called in from the (?), this was the main military research office. Then we had to work on this uranium affair.
We soon convinced the people that we should leave the cyclotron in Paris because the war would be over very soon, and then we would not have the time to bring the cyclotron to Heidelberg. This would lose a lot of time, this transfer. It would be much easier to do the measurements in Paris, just to get the cyclotron running. It was not in very good shape. It did not work at a high pace. The cyclotron was not in a stage to work. So we changed some things, mainly on the high frequency, and we got some pieces from Germany, tubes and things like this. Then after, I don’t remember, half a year or so, perhaps, the cyclotron was running for a few moments almost, until Joliot and I destroyed the cyclotron together, completely. It was a very strange thing. We were very — I told Joliot that the cyclotron is running. I told him that you can see through the windows, the vacuum was not so very good — even this turning, you could see the turning particles by color, by a certain color in the middle of the chamber. And something happened, and Joliot said to the main technician, “Shut down,” and this man went to the main interrupter between the machine and the magnet, you see. And this was a tremendous effect, incredible. I can’t remember to have a just — out of the magnet, the whole energy — you see, there’s a lot of energy in this magnet, and if you cut the electrical power, then all the energy comes out, and fire came out, copper and water later. It was completely destroyed. (laughter) So we had to get this repaired, because it was copper and — it’s a very big effect. I always told this in the lectures, if you calculate the energy in the magnet, it’s quite an important energy, and if you just break this down, you get a very high tension, and then you get fire out, and the copper is molten, and the cooling water comes out of the tubes and everything you like, a tremendous mess. So we had to run another time to repair the cyclotron, and we got it running.