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Interview of Lawrence Hafstad by Angelo Baracca and Michelangelo De Maria on 1984 June 4,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/31618
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Topics discussed include: his time at the Carnegie Institute of Technology in Washington, Department of Terrestrial Magnetism, high voltage techniques, his work in nuclear physics and the first fission of uranium with Merle Tuve, Richard Roberts, Gregory Breit, Werner Heisenberg, and his time at Johns Hopkins University.
[Please tell us] something about your recollections of the role of Tuve with Fleming and Merriam in order to establish the politics of the Carnegie institution toward research associates like Millikan, Compton and Johnson.
Yes. Well this was one of his major contributions, of course, because he had to be a salesman for our projects; and it was a big break with terrestrial magnetism, but the argument was made that we have to understand these fundamentals in order really to understand magnetism.
Was this a trick in some way?
It was part of the technique of selling. I think there is another angle, and that is, that Tuve and E. O. Lawrence grew up together. He used to come and visit often, and Charlie Lauritsen of Cal Tech, he came to visit him.
Lauritsen came to visit the department?
Yes. He worked in much the same direction. And so I think that the fact that there was so much interest in this helped to sell the Carnegie Institution on working in this area, instead of concentrating on terrestrial magnetism.
You mean nuclear physics, modern physics?
Both nuclear physics and this little cosmic ray physics, were directed under your group?
Modern physics, yes.
This is true, it was very modern, the emerging sectors of physics were those two.
And there’s another angle there we must mention, and that is, Lewis Strauss was one of our wealthy men at the time, but his family had a family [history] of cancer.
So the biological application…
Yes, so he was very much interested in Lawrence’s work with high voltage energy particles, the cyclotron and so on; and he was also interested around the country and made contributions to high voltage X-rays, as high voltage X-rays were also used in the treatment of cancer. And so, when Tuve and the rest of us got into high voltage work with terrestrial magnetism, very early he learned about this project.
But was he [Strauss] a representative of some industry? Did he have money himself?
And did he give money to Carnegie?
Yes, he gave a lot to Carnegie, as being rich, but I think he, the fact that he was interested helped to impress Merriam and Fleming.
About the importance of doing basic research and the theory [because of] the medical applications?
But also this one was sold as a way of showing the potentiality of the discoveries in the physics? There was a real interest and appreciation in the physics?
Well, both. In the academic community, it was understanding. In the physicists who needed money, they became interested in applications.
Another person doing historic type of thing asked how I ended up working in the reactor game, and working particularly with Rickover. Rickover, you know his name. He was the man, he’s called “Father of the Nuclear Navy,” the nuclear-powered submarine.
And I wrote this which I think you will find interesting — maybe you should just go ahead and read it.
But this is [about] some work you did after the war?
No, I wrote it up after the war.
This was the pre-history.
May we keep this copy? Thank you very much.
Thank you very much.
I think many of the questions that you ask are there.
But this is connected with your [work], for the war?
Yes. But the first part of it will indicate the origins and the directions of our interests.
So could we come back to the origins, the first developments, and then go back? When you started to develop these high voltage techniques and to search for generating in high voltage had you already in mind that the objective was to do nuclear physics very specifically? Because there was also some interest in high voltages independent from that — some industries — you didn’t have pressures from nobody from developing the…?
The advantage we had, being financed by Andrew Carnegie, we were independent. And I like to cite the 30 million dollars that he gave to the Carnegie Institution was for the production and advancement of knowledge, period.
So you always worked only with Carnegie funds?
There have never been any kind of secondary financing from other industries or philanthropies? So the Department of Terrestrial Magnetism was entirely a department of the Carnegie Institution?
Yes, just like — we were a sister laboratory to Mt. Wilson.
There were other people around who received money from the Carnegie, or through the Carnegie Corporation; so in this sense you know that there are all these people that were in Cal Tech, the Millikan group and Anderson and then, (Compton?) comes from Chicago, or Johnson from the Bartol Foundation Street, I think too received some money — they received money from the Carnegie.
It was one of the philanthropic foundations who gave money to other groups.
The exciting thing was that we kept closing in on the interior of the atom. And then, when the neutron was finally discovered, we thought we had things really simplified. All it was was protons and neutrons and electrons. And that was a very exciting stage we were in, and then, beta particles got into the way, and this nice simplicity disappeared. But at that time, it was to understand those things, and this is why, as soon as we could, Tuve and Breit pushed us into carrying out the proton scattering, and that was pure understanding; and in common language, I say that what we did was to measure considerably accurately for the first time the diameter of a proton, and that’s pure?
Could you tell us more about the early relationship between Breit and Tuve, because we found traces of tension between them. They were friends and adversaries at the same time. We had a second hand description of Breit as a very abrasive person, very hard to get along well with. And so, what is the history of this? What was the influence of Breit on the decision of the experiments you were doing, and what was the initial choice?
— The proton scattering is a typical example.
But it began much before.
Yes, it began much earlier, but you see, Breit being a theoretical physicist, was able to say, “If you can make such and such angular measurements, I can make the calculation to change this into the potential diagram around the nucleus.”
Now, I couldn’t do that, but I could make the measurements of various things. And I think both Breit and Tuve were intrigued by that possibility, so I don’t think there was much — yes, there was friction even then, because as soon as we made the measurements, or as we were making the measurements, there were physicists, theoretical physicists, all around the country who wanted to get their hands on those measurements(?), and Breit wanted to keep them for himself, because he started all of this and he thought —
— the data, you mean.
— yes — that he was entitled to have first use of this material. And Tuve was more relaxed about this and said, “Well, let’s have all of these people try and see what they come up with.”
Now, that’s the kind of thing which created friction.
But also before, we found traces of an early collaboration. Breit went to Europe in 1928, and we found some letters of Breit to Tuve, in which Breit informed Tuve of what is going on in Europe. He was working with Pauli. He met Heisenberg. So he had a sort of, in our opinion, but we want it confirmed by you, a sort of important role in order to communicate the real physics in Germany centers and to give to Tuve direct indication on the creative life of research. No question, so this was Breit, the connection man between the old physics that was done and the new good physics that was done in Germany and the new physics that was just (???) early —
— I think part of that was what I’d call the natural competition between theoretical physicists and experimental physicists, because, let me give you an example.
I remember when, I think it was Condon, came out with the theory that with enough particles you can penetrate the potential barrier —
— yes, so a sort of panel effect?
Yes, you see, and I read that and we talked about it, — it didn’t occur to me at that time that my God, instead of fighting so hard for high voltage, why don’t we just go for high current? It was obvious. But it didn’t register with me. It probably did with Breit. And as a result of that, we kept fighting for higher and higher voltages with micro amperes, and the Cambridge boys were smarter, and they took low voltage and high current.
And that’s the sort of thing. Breit would probably have argued that we should drop our high voltage, and switch to high current, and Tuve would probably —?
— but why did he not communicate with you at that moment?
Because it would probably have taken us a year or two to convert our equipments –
— to lower voltage and higher —?
So you think you did not perceive this theoretical importance?
Not fully, because in a sense, we had an anchor in all of this equipment, which we would have to throw out.
Do you think there was some more strict collaboration among the experimentalists and physicists than among theoreticians?
— let me give you the other side of this story. We rigged up this Van de Graaff machine with beautiful narrow parallel beam, and we started working on the light elements, and Breit being a theoretical physicist said, “Why don’t you start here and go right through the periodic table?”
You can’t do that, because some of the targets would melt, and some we couldn’t handle, some we couldn’t get pure. To a theoretical man, he said, “Why don’t you be logical?” — neglecting completely the fact that you’d have to have entirely different equipment to handle gases and solids.
I want to go back to the question of high energy, higher voltages — I would like [to ask] two questions. One is, what is the difference of style between the high energy physics you were doing here in the Department of Terrestrial Magnetism, and [the work being done by] the Lawrence group, Ernest Lawrence group at Berkeley? And then, if there is, in your opinion, a difference of style, of approach, of curiosity of instruments, between you and the other –
— For example, Lawrence was not developing the detection of apparatus initially.
— not as much as we were.
You were much in the forefront. But I want you to tell us something of your impression, your impression in those days, of Lawrence.
— I think it was the influence of Breit. I think I have enough, without being a theoretical physicist, appreciation of the problems of calculating precision things like the diameter of a proton, if you had a nice parallel beam of homogeneous velocity. That calls for precision. Lawrence, in his approach, was, you have the cyclotron and you have a whole assortment of energies, and you can throw away everything except this much space, but there’s an enormous difference in velocities here. You see. So he could get effects, but not precision that you needed for Breit’s type of calculation.
So it was Breit.
To me, it was.
And probably it was to Tuve too. The experimentalist people of the — and don’t you think Oppenheimer was the theoretician of the Western Coast? Why did not Oppenheimer play a similar role for both Lawrence and Lauritsen?
Well, again, I’d say E. O. Lawrence was a wonderful salesman, and he could go out and get big money easily, and he could get dramatic effects and get a bigger machine, and he lived in an atmosphere where it was easy, relatively easy for him to get bigger and bigger machines. That was not true for us. So we had to be content with smaller machines with greater precision.
So it’s another style of research.
Yes, it’s a different approach to the problem. And there was plenty of work for us to do.
And this problem, at this point, will you tell us some details on the famous interpretative mistake that Lawrence made, I think the disintegration of deuterons, you re-did the measurements, what was the story?
I don't remember the details of this, but I remember talking it over this time with Merle, and we knew exactly what our beam was, and again, what the target was. In many cases with the cyclotron beam, it was hard to know what the effects were and where they were coming from. In the cyclotron, you have a dispersed target, and you’re trying to make detailed measurements on individual events, when you have a whole assortment, and this is why I think they moved into the direction of the cloud chamber, because you could throw away all of the things that were not important, and we stayed with the colummating beam?
Do you remember, did you have the impression at this time that the way of working of being — of Lawrence — is somewhat approximately or not so rigorous as it could have been?
We have the impression of reading some appreciation, not very —?
Tuve was not very enthusiastic of the style of research of the Lawrence people.
No, I think — for the reasons that I mentioned —
— the lack of precision?
Yes. Lack of control.
But because, as you see the further developments of high energy physics, bigger and bigger machines, I do think that after the war, — this is a problem for us — after the war, the Lawrence way of doing high energy physics won the game, not the Tuve mode.
— which was much more, was not big science, was intermediate science, less money but very accurate physics with very precise measurements and theoretical interpretation of the measurements. Lawrence was the good salesman who found money, who talked about the applications, and who constructed bigger and bigger — so this spiral, the high energy physics, after the war, was much more conditioned by the Lawrence model than by the Tuve, Hafstad and — but why? Why did his model of doing research win?
I think, the technical reason, it was easier to get really high voltages in a magnetic field than stretched out.
Yes, but I would say, in your opinion there are external elements, like the role of the philanthropic foundations, the role of the state, the National Science Foundation. I know that Tuve would never allow other people to accept money from the National Science Foundation, so he had, an Italian would say, a very Franciscan style of life.
And those are still, if you go to the department, you, a climate that is not present…? — that is not present even in the Italian universities.
So he characterized the second style of doing research, and Lawrence was the prototype of another kind of —
Yes, one that is capital expense, capital intensive, I would say. But why did he win? I understand that the machinery…
— yes, I think, the technical reason.
But besides the technical reason, there is no other reason why Lawrence model won the game, not the Tuve model?
Well, I think it’s almost, would have been impossible to carry the Tuve model, as you call it, to the kind of energies that are relatively easy with the cyclotron.
Yes, but why do you go to higher and higher energies, why? Do you think there is really a theoretical reason to go?
You were doing wonderful physics.
I would say, that’s your fault, because you discovered cosmic rays and we have to explain them.
Because cosmic rays have very high energies.
So, if you approach the problem by saying, what we learned about cosmic rays indicated that there is a big hole in our knowledge between what our group considered high voltage, and cosmic rays, and E. O. Lawrence said, (filled the gap)
Yes, but it was a lot of wonderful physics which could have been made following your route. And on the contrary, you felt — if you, understood where, answer to answer… after the war, you retired from (crosstalk)
I would say Willie Fowler at Cal Tech followed the Tuve approach and got a Nobel Prize with it.
And why did you retire from nuclear physics after the war?
Why did I?
Your group, and do other kind of research after the war.
Well, I can only give you, in my own case, this was, I’d say, a casualty of the war. I enjoyed research, especially experimental research, and I still like to work with my hands, and at the end of the war, we moved from the proximity fuse to guided missiles, and it happens that I was the chairman of the first Pentagon committee on guided missiles, and was very active in this, because some of the Navy admirals wanted us to put proximity fuses in 12 inch shells, and a guided missile is much more flexible than a gun, so, we started pushing hard for guided missiles, and I think that got me in contact with the Pentagon, which is a much broader field, and Vannevar Bush was the chairman of the Research and Development Committee for all military research and development.
Between when and when? After the war?
Just after the war. And he knew me, and he invited me to come in and be the executive director.
…because we were working at the Department of Terrestrial Magnetism. I was a nuclear physicist and a radio expert at that time, and enjoyed it very much. But just before the war started, Vannevar Bush, who was the president of the Carnegie Institution, had been through World War I, and he had worked on essentially a bigger anti-submarine problem.
With Millikan and the NRC people.
Yes, and so, he saw that the war was coming, and well before Pearl Harbor, he started to get a group of physicists, especially his own. He took us off the basic science, and urged us to get into military development, and —
This was when, 1939?
From this point of view there is a strange episode that we did not understand. In January 1939 there was the 5th Theoretical Conference, and I think that you and Roberts and another one of the — as I remember, the first fission of uranium was there.
One of the first.
One of the first, simultaneously with some people in Columbia a few weeks before, but you did not know anything about that. And so that was, and Fermi was there at the conference and I think also Bohr was there. So you did represent a group of people who knew what was the fission, the problem of fission. One question we want to ask you, is why you did not finish directly in the Manhattan Project, when you worked on proximity fuses, because you were among the few people who really knew nuclear physics (crosstalk ) — so that was something I do not understand. Then I found that declassified document (declassified in the ‘60s) sent to Tuve from some one of the other research laboratories, in which it appeared that you did for a few months some work on the nuclear submarines, trying to do some research to see if it was possible to produce nuclear power for a submarine. So tell us if you can something more. How did you pass from the fission to the proximity fuse?
I’ll have to make a narrative, because a number of things happened at the same time. You see, because we were working in nuclear physics, we had close contact with the British at Cambridge, Rutherford, so we knew Cockcroft and all those people. And when the war came along, they got into weapons work before we did. And since we were friends, at one time, they sent an expedition over here to visit and bring our people up to date on weapons work.
On what they were doing in Cambridge, in England.
And of course anti-aircraft was one of the main problems we had, so we talked, argued a lot, about what can you do to shoot down airplanes. They had been thinking of it longer than we had. So they came up with various kinds of proximity fuses. You see, if you could make the shell explode as it was passing an enemy airplane, you could knock it down. Otherwise, with what I call alarm clocks in the shell, it goes off either too early or too late. You have to fire many projectiles in order to hit a plane. And they brought this to our attention.
When you say “they” who were the English scientists?
Cockcroft was one of them. I’ve forgotten the names. It was an official delegation.
And Cockcroft was your friend.
Yes. The best. Well, the one they had thought of was a photoelectric effect, possibly a kinetic effect, and most importantly, a radio set which would transmit and receive. That was the beginning of the proximity fuse.
So we picked up that idea very early and were thinking about it, and the question was, can you make vacuum tubes that will stand 20,000 feet (the acceleration of the gun)? And so that was a big order. So these ideas were floating around.
Then came the fission process, and of course we started talking about the possibility of explosives; and there was a German who wrote an article about that and published.
A German(?), not Hahn, I think.
No, this was —
— after, this was already after — first time you talked —
No, this is the first time in print that anything was mentioned about an explosive weapon.
I don’t know but we can check in the journals of that period. Lise Meitner and Otto Hahn were the fission, but he is saying someone who wrote an article particularly on the potential, fission — of a chain reaction for an explosion. And that appeared in the German Naturwissenschaften.
Yes, that’s important. And I mention this because those of us who were aware of the possibilities of a chain reaction took the opposite side, that we mustn’t talk about this, and we must keep quiet, without any talk about an explosive. And yet that appeared in the newspaper. Not a newspaper, but in the literature.
Citing in front of the public or also in front of the authorities?
Both, because shortly after they had demonstrated the fission, the top theoretical people and Gregory Breit was one of them who could think through the mathematics of this began to say that we’d better keep this quiet. Not published. But we all worked together, with Breit. Breit persuaded the Physical Society to stop publication of any of this. So that’s why there’s this hiatus in publication.
At the same time, it was extremely important to learn all we could about nuclear processes, and so, we began quietly, especially Dick Roberts continued his work on nuclear cross-sections, and I was more —
— producing of different energies on uranium.
Yes. And as part of this work, we happened to hit upon the delayed neutron effect, which is very important, as far as chain reactions were concerned. So we did continue work in this area. At the same time, we were thinking about the anti-aircraft work.
Can we interrupt you just to check on one point? We do not understand if this politics of being quiet and keeping a low profile and not being able to publish anything was something that Breit did or suggested to the PHYSICAL REVIEW inside the physical community, or it was also a political decision in which — so it was something…
— no, we decided to keep the politicians out.
— the politicians out, because you (crosstalk) — an explosion, a bomb, weapons —
Yes, they didn’t want to get talking about this.
— in front of the politicians. But a few months later in October, ‘39, there was that famous letter signed by Einstein, Szilard and another one who, to Roosevelt, so at that time, that was usually considered the starting point of the Manhattan Project. These months you took an independent decision. The physicists decided to keep —
Those of us who were making the measurements decided we shouldn’t talk about it, except among ourselves. And the other thing was started entirely separately.
Was Heisenberg also working on this?
— measurements, so it was after Hafstad, Roberts, Heisenberg, And Tuve –
— Tuve, right —
— in the Department of Terrestrial Magnetism.
And I would add, some of the other people in the Washington area.
Who are they? Curtis?
Ross Gunn, and the people at the Bureau of Standards. The Bureau of Standards even set up a committee under the director.
— doing measurement on fission of uranium?
To essentially collect information, and be in the position of having solid facts to push through, rather than an emotional approach, and I think that was the difference. One was a political approach.
And this happened in 1939. And why did you interrupt work on the problem of fission, and did not go to Manhattan Project and went to the proximity fuse? You already told us a bit of information, that all of the English scientists and Cockroft’s people — but why did you decide to work with the military, the navy?
Our group made the assessment that a nuclear explosion was conceivable, as far as physics was concerned, but it was, in our opinion, very unlikely that it could be got into production and used in this war. And since we were already, our little group, deeply involved in the anti-aircraft work, and the Navy, which had just lost, the British had lost two big battleships to the Japanese, the Navy was really frightened by the idea that airplanes could shoot them down, so they put pressure on us, and we agreed that if we could solve this problem, of the proximity fuse, we could solve the Navy’s problem, and in my mind at the time, if we could make the proximity fuse work, we would change an air attack into a turkey shoot.
But did it not only save the Navy, as the study has demonstrated, because during the period of the kamikaze Japanese pilots, the Navy saved — but also. London was saved. It was important in there, then —
Yes, and the possibilities were so great and so obvious —
— and so near to realization.
And except for the one problem of making a rugged vacuum tube, rugged and strong -~
— a strong vacuum tube that could bear the 20,000 —
And we started, Heisenberg and Roberts and I, bought up all the little radio tubes —
— and Tuve, too, was in —
He was our leader, and handling politics, and that’s (crosstalk) — but we were the technicians.
The real work was done by you, Roberts and Heisenberg.
And what we did was to buy up all of these small tubes called miniature at that time, that we could buy at the store, and then we dropped them from the second story window onto the concrete below.
To see if they broke.
To see if they’d break. Practical research. Most of them broke, but some, the envelope held up and only the filament broke. And that was the secret.
The envelope? …broke?
The glass part — the glass didn’t break, but the filament inside broke. The structure inside.
So you had to resolve the problem of the internal structure of the vacuum tube.
Yes. And we were relatively satisfied that with cushioning and so on we could keep the glass from breaking. But we had to redesign the inside, and that’s when we brought in, started bringing in outsiders.
I think the man who solved the filament problem for us — I forget names, but — was the man who was expert on big steel bridges.
Big steel bridges, like the bridge we had to pass through to here?
Suspended bridges with iron —
— they have vibrations, and one of our big bridges failed, because of the vibrations, and that’s essentially what goes on inside of our tubes. So this mechanical engineer type was brought in and started working on the inside of the vacuum tube, and we made enough progress so that we pushed it through.
Many people, I think I would agree, that we would have won the war with the proximity fuse, even without the bomb.
But if we hadn’t been able to handle aircraft attacks on the ships, we probably would have lost the war without the proximity fuse.
Certainly the Midway battle.
Yes, this was critical.
Can we got back to a question? This was the technical aspect, but I think that your group did profit very much of the almost 15 year experience on radiofrequency work, the thesis(?) of Tuve and Breit and (crosstalk) — because, miniscope(?), if I am — the Heavyside layer.
It was a work which went on parallel to this work.
— it was the official work (crosstalk)
Nuclear physicists, who were also knowledgeable in this radiation area, —
— this work never stopped during the 15 years.
That was continued. But here I have to make the point that the proximity fuse could not have been a success without the work on high frequency fire control.
Fire control? What is a high frequency for fire control?
Let’s go back to World War I type. The airplane comes in here, and some people track it with a big bunch of machinery, looking through this and turning cranks; and then, based on that, they predict where this plane is going to be at some future time. Then they tell the guy setting the alarm clock, and he sets the alarm clock; and they hope to meet up with it. Now, with radar, you can follow that plane and get all of the measurements that you need. Quickly. So, radar tells you how far away it is. But you add to that the possibility of predicting the question of motion, the trajectory — the future trajectory, you predict the future, correctly. So this was done at the Radiation Lab at MIT, and they developed the fire control radar, which had needed —
— oh “fire” in the sense of “to fire?”
Yes, fire control.
To regulate the fire of a gun? Up to the future trajectory of the —? I understand. This was at MIT.
Yes. We called it a gun made radar, because, as the plane moved along, the gun moved along too, see. To get in the right position at the right time.
I understand, to make a target.
But you were right, it just happened that we were a group of people who knew our way around in radar, at the same time we were working on this.
Your research on radio frequency was indirectly very important for the radar work in general.
True. So Appleton used a varying frequency to establish the existence of the (???) there. Breit and Tuve were the first ones who used a pulse, a short pulse.
So the work they did in the late twenties was used afterwards to solve the problem of the proximity fuse. And I want to ask you, then we go back because we started from the end, we go to the real physics, but on this point I understood that the English were the ones, the scientists, the colleagues were the ones who convinced you to work on this problem, and there was exchange of information, that you as a group thought it was too expensive and too long to realize a nuclear weapon.
And you thought it was important. Did you receive any direct invitation to join the Manhattan Project? Because what — this is the —
— again, this was done quietly, and it happens that, let’s see, at that time, I had a world monopoly on plutonium.
World monopoly on plutonium? I thought Fermi had some —
Oh, no, polonium.
I’m sorry, polonium.
As a scientist, now, before the war, we were interested in the fact that you could produce transmutations with alpha particles, that was 1919, and that was very exciting to all of us. And the argument was, if we could only get something like five million volt particles out of a vacuum tube and have them in a nice parallel beam, then we could start transmutation on a large scale. And so this was a dream, and we approached it in two ways. One, we worked on accelerators.
High voltage. And pushed high voltage as hard as we could. And as you know, I was involved in that. But I think it was Tuve’s suggestion that we must learn how to detect these particles. We have to work with them in order to understand what’s happening. So I was essentially assigned the job of repeating Rutherford’s experiments, and to do that, I had to get a source of alpha particles, and so Tuve arranged that we could collect the spent radon bombs from the big hospitals all over the country, and they were shipped in to us. I went to the Bureau of Standards and got instruction from the man in charge of radioactivity there, and worked in his attic laboratory, and crushed all of these radon bombs by hand.
This reminds me of the history of Amaldi likes to say, how they were handling radioactive things in (???) in Rome.
Then I had to learn the chemistry, because I had to extract polonium from this mess of glass, and Dr. Zies at the Geophysics Laboratory —
Zies, Dr. Zies, he was interested in geophysics and earthquakes and so on, but was a real good chemist, and he taught me what I needed to learn, to essentially first concentrate polonium, and then plate it out on a platinum, little plates.
This was much before, it was in the early experiments you did in nuclear physics?
This was parallel to the work on the high voltage techniques.
Entirely, because we foresaw that we’d have to have the techniques for measuring these particles, and the result of this was that I started working with electrometers, Hoffman electrometers, and you could just barely get a signal for a single alpha particle in a few centimeters. But I amplified this and I got swings of a whole meter; and so that was my thesis for the PhD.
The detection. But you also worked from the very beginning in the Department of Terrestrial Magnetism on Geiger-Mueller counters — sir (?) and then with some, Chambers(?), with the fine tracks of most —
Yes. We felt we had to know all of these things.
That’s why, when the cosmic ray experiments began, when the (???) and (???) experiments coincidence in Geiger counters were done, Tuve was ready to work on that.
Did you work on some of the very early experiments in cosmic rays with Tuve?
No, I’d have to say no on the cosmic rays, but yes, on the techniques.
The coincidence Geiger-Mueller?
Tuve, from what I read, was one of the first to suggest the track(?) of coincidences.
And a sort of telescope —
Yes, that defines — those were exciting days. So much I
Cosmic rays were not your principal interest.
But also Tuve worked on that topic for a very short period.
That was one of the paradoxes — why, there was Tuve here, I mean Tuve wanted to do high voltage physics, but he had good ideas on cosmic rays. He gave these ideas, some to Curtis, some to Mott-Smith, and then he was sort of advisor of the king in order to share the money between Millikan and… (off tape)
I wanted to say, you raised the question that there’s a gap here between the time when we were in Carnegie and then we went off to Johns Hopkins University as a group to work on the proximity fuse. And then, at the end of the war, Johns Hopkins decided to drop it; and the question was, do we all go back where we came from? Or do we go elsewhere?
And at that time Tuve decided that he wanted out of military research, and he went back to Terrestrial Magnetism.
Why in your opinion did he decide to —
To do that?
Yes. Did he consider a scientist could be involved in military stuff only in the American system?
— yes, that’s right, essentially.
And he wanted to go back to —
But it is right also that the larger scale of research —
— I think this is true.
He thought that big science could be better for the creativity of the science.
I think it is.
So you agree. What was your relationship with the other people, the friends, the people of your group, your personal relations?
But I would like to know the dynamics, not the photograph not the static. Because you were here in ‘28 I think here.
Yes, in ‘28.
And what did you find, what was the —?
Well, I think seriously Merle Tuve and I were sort of complementary, because he was the idea man, and I was the technician.
But that’s not true, you were more than a technician.
But since he was an idea man, we could argue and I could talk back to him, see. He accepted it. And so in that sense, I think we were complementary, and we both happen to be of Norwegian descent, but Tuve has been described as a Norwegian with a Latin personality.
…while you were a Norwegian-Norwegian? 100%. And there was also another Norwegian, that was physics done by Norwegians, there were others.
At least Scandinavians. But to go back to your question, at the end of the war, then, there was uncertainty as to what would happen to Johns Hopkins. Tuve was in favor of closing it up, and the Carnegie Institution said, “Close it up.” Under their contract they couldn’t do military research, and Johns Hopkins University had only done it under crisis conditions. So I had a decision to make, I was the assistant director, and in this article that I gave you, there was quite a tension among the scientists, at the end of the war, those who wanted to forget the war and go back to the universities, and those who said, “Well, this conflict is going to continue.” Luis Alvarez, one of E. O. Lawrence’s strong supporters, a very good man, came around to visit our laboratory, and urge us to stay in the military field. I mention that in this article. And to me, that was the turning point for me, because normally I would have gone back with Tuve to Terrestrial Magnetism.
Did Edward Teller play a similar role with Alvarez and Lawrence?
Probably. At any rate, I was instrumental in keeping the laboratory going, at Johns Hopkins. And then Van Bush picked on me to move into a more responsible position, and that put me in the administrator category as a scientist.
Why don’t we got back to the thirties? And you ask your question.
Yes, I have something to ask you, another question about your development. Initially, if I have understood it, you had mainly three kinds of problems generating high voltages, having an accelerating tube which was a different task, and having a detecting —
— technology. Those were three things that we had to do.
And meanwhile the radiofrequency research was going on. Always, more or less. How did you organize this work? There was some division of tasks.
The way the Carnegie operation went, each individual would make his own decisions. It’s an exaggerated academic atmosphere.
Freedom of the single scientist — but from this point of view, I’m sorry if I interrupted, I would like to understand better, you told us before, that Tuve was the salesman, he wanted to, thought it was important to do nuclear physics, because it would result in more fundamental problems at the Department of Terrestrial Magnetism. But there are two different people, one is Fleming, who was your boss, and one was Merriam. From what I understood, Fleming was, I mean, not a strong, not a big personality. Can you tell us more about the relation between the active scientists, Tuve, you and Fleming, and then between the department and Merriam. Could you go directly to Merriam, or Fleming was — because I thought Fleming was not a particularly brilliant scientist.
He was not a scientist.
He was not a scientist at all? What was his role in the development of your laboratory?
I would say, administrator, and I think Tuve and Breit would go to Merriam over his head, which he didn’t like, but that was only on big issues, and most of the time, he handled the money end. Only money.
We found letters of Tuve to Fleming in which you say — complain about the fact that if you want to do research, you must have the right instrument at the right time. For instance, he asks for big magnet. It’s many many years before having sufficiently large magnet. Or asks for a big Wilson chamber in the early thirties and it takes years to get this chamber and you have to work with this chamber that Curtis and have to give you. He has a sort of negative role?
Yes. That’s always so with a money man.
But notwithstanding Fleming you were able to do very good physics. So the role of Fleming was, “slow down,” because — Tuve had many ideas before the real experiments were done in other places. For instance, Bruno Rossi was one of the first to do cosmic ray research, but I saw that Tuve had exactly the same ideas at least six months before Bruno Rossi.
This was true. Tuve’s genius was to keep up with his friends, particularly in the theoretical area, and then come up with interesting experiments which ought to be done, but he was not in a position where he could tell some technicians to do it. So his ideas were good, but he couldn’t carry them out, because he was impulsive, and he would jump from one idea to another, and they were all good, but those of us who worked getting apparatus built, and were ready to take measurements, couldn’t jump from this to the other one.
Tuve — was very (???) but he could not, it was understood he could not, the organization of labor and the dimension of scale of the department — so he worked to spread ideas to others active physicists in the United States. He had this role of suggesting experiments to other people.
This was my impression. And Breit too still had the same role, from the theoretical point of view.
The same role with respect to the cosmic role research, was longer, the active interest in this field.
Yes, you didn’t feel any competition, any, in what respect, the money which Carnegie gave to cosmic ray physics, with respect to your research.
This is, how you say, (???), this came from the Carnegie Corporation through the Carnegie Institution, but it was not that if they gave more money to the cosmic ray people they gave less to Tuve.
No, it wasn’t that way. What you find in —
Yes, Tuve said, “Why do you give so much money to other people external to this institution on cosmic rays and you don’t give us the big magnet for research?” This is something. But — because the letter of complaint to Fleming — but I do think that the financing of the two fields were completely —
— independent. To defend Fleming, the Carnegie Institution as a whole had the income from a certain sum of money which could be spent with extreme freedom, but the president, Merriam in this case, had to give so much to Mt. Wilson and so much to the Geophysics Laboratory and so much to Terrestrial Magnetism, and it’s all committed.
What do you mean, it’s all committed? The money was already divided?
The money was divided, to run those laboratories, at the level at which they existed, and if they’re going to change their plans significantly, as long as they worked within the money allocated, they had freedom. But if somebody’s going to hire another person, they’ve got to go back upstairs to get the money.
And so Fleming’s responsibility was to keep his department living within the laboratory budget.
I understand. So there was no problem of expansion.
No. No provisions.
The boundary conditions were rather rigid. There were not possibilities — that is probably why they could not follow the model of Lawrence in their activities, because you were inside an institution with —
— lots of freedom.
That was the positive side, lots of freedom. One question we wanted to ask is, what was the early relation between the Department of Terrestrial Magnetism and Europe?
— I have to ask about your travels in Europe in the 1930’s. You were two months in Europe. Were you there to work with explicit contacts with people and to others, let’s say, a view, panoramic view of what was going on and you had the choices to make?
For me that was a very valuable and inspiring trip, because I met so many of the people — you know, it’s one thing to read, but to talk to them makes all the difference in the world.
To see how they actually work.
Yes, and under what conditions they work. Cambridge —
Did you meet Rutherford?
Yes, and it was a privilege. But (crosstalk)
— the (???) people because I was born during the war, just a few months before the liberation, the Americans came to liberate Italy.
He quizzed me. We started talking and then he wanted to know what we were doing at Carnegie with experiments, and the message he left with me that I remember is that, he said he always had trouble getting his graduate students to get on with their work.
To get on with their work, what did that mean?
To start doing something seriously, because his trouble with graduate students was that they would keep thinking about the problem and all of the ramifications, and never start putting anything together, and he complimented us on, when we decided to do something, we built the apparatus.
Rutherford admired your efficiency, your working capability.
— But from what we knew, there is a strange relation of good friendship with the English experimentalists at Cambridge, but also competition. I would like to clarify — you worked in the same field and Cockcroft’s work; and then, —? Newton?
I think in general it was friendly competition, like a tennis game. But the one place where I think there was friction was that, in the Heavyside(?) work, Appleton used frequency modulation to get the evidence, and Tuve and Breit used pulse, and they got the Nobel Prize, and we didn’t, and that doesn’t worry me because I think they were ahead of us in time, but we were ahead in precision.
I’m very interested in this. What are the people who won the Nobel Prize?
Because he was doing this kind of measurement, you were doing this radio pulse measurement —
That’s right. With the pulses. And he did it by, as I say, a variation of skip distance, does that mean anything to you? In the early days of radio, those of us who were plagued with weak transmitters would find that from Minneapolis, I could reach Chicago, say. And then some days, I couldn’t reach Chicago, but I could get Washington, DC. Which is kind of silly, and this was due to skip distance, when signals went up to a mirror up there and then back down, skipping, and so, in between, you had poor reception, but at this distance you had good reception. That’s called the skip distance, and it was essentially explained by the (???) Heavyside layer up there acting as the mirror.
So by reflection instead of by direct transmission.
Yes, that’s all right.
So you were in contact with various laboratories, that could send and detect signals, a lot of —?
And I just remembered that Merle and Breit were very unhappy that Appleton got ahead of them.
Merle Tuve and Breit. But this was a competition on gradual, let’s say — transmission — but in nuclear physics, what were your relations with the other laboratories?
I would say they were our mentors, our teachers.
They were the leaders, the British people? They were your teachers? But I wonder, during the thirties, it seems to us that the main discoveries came from the American laboratories and then European laboratories, so they began — but your techniques, your methods, your approach became better than —
— so there was a shift generally in research. In your opinion, is there a shift of scientific (???) from Europe toward the new continent in the thirties?
I think that’s true. That’s right. As far as I’m concerned, thanks to my trip around Europe, I felt confident that I knew what they were doing, and if we were doing something as well or better.
That’s when it pushed into your consciousness, in the early thirties, that you are doing some things better?
Also the high voltage techniques and apparatus, the device of measurements, began — and the sources also changed. Did you have any relation with the French, Joliot-Curie and these people?
Not much. I visited their laboratory, and I have to say, I wasn’t nearly as impressed with them as I was with Cambridge and Vienna.
Vienna, who was in Vienna? Do you remember, scientifically? I think we do have some indication of some of the people that — Vienna (crosstalk) —
… familiar names. They were publishing at the time.
Did you receive other visits of nuclear physicists here? For instance, Fowler came here?
We had —
— Lawrence came often.
And then van de Graaff?
Van de Graaff.
He was a good friend of yours. Of your group.
Yes. And Charlie Lauritsen from Cal Tech.
A couple of things about the main experiments you made in the thirties. I get this from the published papers. One of the fundamental experiments was about resonances. You were the first in the world to measure the width of a neutron resonance, and I think that Breit had a special role in this. He had the concept, the theory, Breit and Wigner formula so he suggested to measure the width of nuclear resonance.
He was on the theoretical side.
I don’t remember any specific event, where he came and said, “You ought to do this,” because the way we worked would be, to talk freely as a group, and then he would bring up his new ideas. Continuous.
Breit was an associate of your laboratory.
We had lunch together, went down to the Bureau of Standards and talked to the people down there, and so, out of these discussions, these ideas would emerge, and then be picked up.
…brainstorming, how do you say?
Yes, brainstorming. And again I’d say, as I mentioned before, the theoretical men would suggest something that would be very well worth doing, but then we had to say, “What would we have to change, and how long would it take to get the apparatus and the money to do this experiment?”
Now, I think the prize example of that was the fission process, because we all went down to the big meeting.
The theoretical conference.
Yes. And then the theoretical people got into an argument, as I recall, about the interpretation, and I was sitting in the back of the room with my associates, and what I recall is, I said, “Hell, we can settle this argument, let’s go back to the laboratory and do it.”
We had a beautiful neutron source with a concentrated target. We could measure all of these things, and it was either true or false.
So there’s one where nobody suggested it, it was just —
Do you remember who were these theoretical people at the conference that gave you the hint at these experiments? I know that Fermi was there and probably Bohr.
I think some of the lesser physicists were arguing with the tops, and to me, that got tiresome.
You went back to your work — and Roberts also. There were three people, Hafstad, Roberts, and ?
I saw the article recently, but I am forgetting the names here. It’s a short letter to PHYSICAL REVIEW, in February, signed by three people, Hafstad and —
I think you might be interested in this angle, and that is, the way we were operating at that time, I was pretty much responsible for keeping the beam going, because I’d built the apparatus and knew how to change elements or anything.
The apparatus in this case is the van de Graaff, the big one, that’s still there.
Yes. And so my responsibility is to get the beam on the target and produce the neutrons, and Dick Roberts had had special responsibility of keeping his detecting apparatus working, and so as soon as the beam was going, it was just routine to —
Another specific question that I asked before that we did not discuss, you and me, was when Amaldi came. Amaldi was a Fermi man, he came here and he did some research with you. We saw the whole (???) full of water in the basement, it was necessary to go down with the — (crosstalk)
Yes — of all the experiments —
What was your memory of this, your collaboration with Amaldi? This group of crazy Italian people with these Norwegians?
As I recall, he was at that time interested in the (???) effect. Does that ring a bell with you? Again, the exciting thing was that we had essentially a point source at our disposal.
A point source, a very specific mono (???) beam.
Yes. And that’s what he needed, and that’s what we had.
We had the big pot of water, and it would have been nice if we’d had a high neutron source, of particles, right in the middle of it, and then you could study the diffusion and attenuation and so on. And this is what we provided. All we had to do was put a tube down here and put the target down here, and just took this out a little bit, (???) but not enough to destroy the beam. And he was such a pleasant person to work with.
Amaldi. Amaldi was a terrific fellow. He’s still in very good shape. He was emeritus professor up to last November. But he’s still in the institute, where he’s a sort of father of the Italian physical community.
Give him my regards.
When you performed the (???) experiment, did you have already some idea that the neutron sources should be a chargeable (???)? I mean, have you got some idea of the confirmation and quantification, or did you expect that in principle the kind of things —?
I’m not sure I understand — the basis of your question. Because my approach to it was that, we know and trust the electromagnetic forces, and it was clear that they broke down at some point close to the neutrons, and so, our job was to get scattering particles closer and closer to that center, in order to find out the exact point at which this broke down, and some other kind of force came in. Without worrying at that time about the nature of that force. Does that answer your question?
Yes, in part. The experiment in (crosstalk) — also to see that the most important force is equal to the neutron force.
That was important, very important, first time that it was tried, and I asked if you expected in some way these results, from prior considerations?
It was not discussed in those terms.
You just wanted to know at what energy did the breakdown of electromagnetic — (crosstalk)
And I think, I would have turned this problem over to Breit.
The theoretical — I agree. So it was in direct consequence of the experiment, in some way.
Probably Breit was right, since he wanted to have the excuse(?) of your data, it was after the theoretical elaboration.
So the numbers they wrote in their notebooks were not yet the —
They were not interpreted.
They were not interpreted, so there was this important —
— a big step.
— a little of interaction between role the experimentalists and (crosstalk)
— yes, but, I was asking if Hafstad could remember that there was some expectation about the independence of nuclear forces?
I would say, no.
Don’t you think in the course of this, these 40 years, the role of the tradition has changed in this sense, that in the early heroic period, theoreticians like Breit and von Neumann had a very active role in suggesting the experiments and development of —
Also, the complementarity between you, arguing and maintaining, the table was not so obvious, from the light elements to the — (???) uranium… it was a —
But now, I think, from when I was a theoretician, it is to me that often the role of the theoretician is sort of a servant of the machinery. Yes, the machinery is good, and the theoretician has a much more passive role, as to say, they make counts afterwards, they don’t suggest, they don’t have the same —
I think this is true.
A change in the role of the —
Yes, theoretical people react instead of initiate.
Now, the Washington Conference on Theoretical Physics played an important role.
A very big one.
For a certain time. Many people from Europe also came.
And Breit and Tuve should get a lot of credit for that, because they are the ones, maybe you don’t realize this, who persuaded George Washington University to hire really outstanding young Europeans. Gamow was the first of these, Teller was the second, and then that enabled our little group of physicists to get acquainted with these geniuses.
You think that Teller and Gamow were geniuses. I don’t have a very good definition of genius but I would suggest that Tuve and you are at least, from the point of view of research, as high ranking physicists as Gamow or Teller.
Well, let me say, in the theoretical areas, —
But don’t you wonder about the fact that nobody in your group has won the Nobel Prize, Lawrence took the Nobel Prize, and so don’t you think that your group has made contributions at the level of other Nobel Prize winners?
I would say the proton scattering experiments were up there at the Nobel Prize level. But it happened at the time when there so many Nobel Prizes coming up all over, so that it was just lost in the competition.
But do you not have direct evidence that someone suggested your group because Tuve and you and — they could have proposed your names, because the Nobel Prize is based on the suggestion of other people.
I don’t know this for a fact. But does the name Foster Lord mean anything to you? He wrote a book. A good physicist. He was much impressed by our work. I don’t know if he ever wrote to the Nobel Prize people, but I know he later proposed it for various awards in Washington. But nothing ever came of it. To me, not surprising, because other things were happening and it was just overwhelmed by these other things.
Yes, but for example, the Nobel Prize to Lawrence in ‘39, yet, beefed up the cyclotron, but a more important result had already come out from the cyclotron.
But Lawrence was a very good salesman, of himself. He was very well known, he was a monk in a —
— that’s a good example, he was a monk and we all worked in this (crosstalk)
…any San Franciscan that was here, we had lunch there, and they were very excited to know, (???) because and Louis Brown told me, “This is still the era of the Tuve period.” That was a different small science research — it’s not big science, Lawrence got the Nobel Prize because he was the initiator of Big Science. You can say, he was incredibly capable of beginning, surmounting, getting the publicity concerned. He was much more, how you say, he made a lot of mistakes, because he went to the conferences to say that the deuteron should be split and this was a mistake and Tuve found that he was wrong, but he won the Nobel Prize. This is life.
I want to ask, can I go back to cosmic rays? I want to ask you a question that is relevant to my research. In the early thirties, from ‘31 to ‘32, in America, there was the usual migration. First, cosmic rays were born in Europe, then Millikan put his big fist in the plate and the plate changed, so Millikan was the important man for cosmic rays in the sciences, but he had the crazy idea and theory of birth cries of atoms. He thought that the primaries were protons. Then Compton came in the game, and he organized in ‘31, ‘32 and ‘33 a way in order to measure the so called latitude effect, and there was a big flight in Atlantic City, December ‘32, between the two prima donnas, the American Nobels, Millikan on one side and Compton on the other side, and Johnson was in favor of the particle interpretation of primary cosmic rays. So both, these three men took money from the Carnegie Institute, and Tuve had a role, he wrote memoranda, he said, “This is meaningful, this is nonsense,” and so on. Do you have any direct remembrance of this confrontation between these two important physicists?
Nothing direct, except we were aware of it, and I think my reaction was — well, to go back to the old statement, when two politicians have a difference of opinion, you pass it off, because they’re both opinions. When two scientists have a difference, one of them is wrong.
In this case Millikan was wrong. That is very surprising to me.
If there should be a period of ambiguity, when information is not available to make definitely incontrovertibly clear which is right, then you can argue. But as soon as the evidence is in, you stop arguing. I’d like to cite the precision value of the constant E. You remember?
The electron. Millikan measured this, and it was confirmed by a long series of graduate students, because they kept observing and observing until they came up with that answer. That was confirmed. But with (???) at Johns Hopkins, who approached it through X-rays, it came out a different value.
When was it?
In the late thirties.
And that was a shock to me. It was just proven constantly, you know, and it took courage to come out with something different.
But it was probably a slight modification of the value of —
Yes, it was — 4.774 to 4.80.
That’s a small — You vaguely remembered there was competition in this period of time.
I wouldn’t cite it was anything.
But Tuve has a very strange — because this is the period of big expeditions, Johnson and Alvarez went to Mexico City to find the so-called East-West effect, and the Carnegie gave the money to Johnson, who was working at the Bartol Foundation.
I think that was — I don’t know who made the decision, but it was a good one, because all of these people are good, but you have to have some guy at least nearly as good who is neutral.
But from what I knew of the role of Tuve in cosmic rays, he was taken for a very short period then he was taken by, his real interest was in nuclear physics and hydro physics.
But he still had a sort of role of, I already asked you this question, but I would like to put it in another way, of being the advisor of the prince. In this case the prince was Merriam and he was not so concerned with going up in the airplane to measure on the top of the mountain using sounding balloons. He was in favor of doing experiments in laboratories with magnets and so on. So he said(?) — OK, I do think Millikan is wrong and probably Compton is right, but they are going to spend a lot of money to measure small effects on a big, small effects, and he thought it was not so relevant. Why? He thought it was important to do laboratory experiments on these things.
Under controlled conditions.
Under very controlled conditions, and I think that this attitude is the same attitude that you were saying before about nuclear physics.
Yes. Because unless you can control your variables, it’s awfully hard to get good end results, and that’s the trouble with going in airplanes. Lots of things are changing.
So he preferred nuclear physics instead of cosmic ray physics also for this reason.
Probably for this reason.
But he also — the kind of experiment à la Anderson, like Anderson found the (???) in cosmic rays first in the cloud chamber.
And that’s evident, when he puts a lead plate, and he could measure, because you can, an upward electron and a downward positron would look the same —
So the first reaction of Anderson was that, “Who did change the polarities of the magnets?” because he considered that it was an inversion of the magnetic field. Then he put a (???) in a layer of lead, and he could see that the (???) changed so he would say, he could fix the direction of motion.
And this is the kind of thing that Tuve was thinking even before, to couple a Geiger-Mueller counter with cloud chamber technique, of course good physics but Fleming did not give him the magnet, and he needed a strong magnet, you know, because of the energy to (???) of this —
Yes. I think we were all aware of this, but we were having so much fun with what we were doing, and the privilege of having the freedom to work our own hours, for example, and have no administrative problems. It was ideal conditions for a scientist. You probably sensed that when you visited. These are people who are really dedicated, and live for their work. And there’s room for someone like that.
Well, have we answered your questions?
Yes. We are really grateful to you.