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Oral History Transcript — Dr. Robley D. Evans

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Interview with Dr. Robley D. Evans
By Charles Weiner
At MIT, Cambridge, Massachusetts
June 14, 1978

open tab View abstract

Dr. Robley D. Evans; June 14, 1978

ABSTRACT: Family background; grows up in California; early interest in electronics. Undergraduate and graduate studies at Cal Tech. Strong interest in history of science as undergraduate. Ph.D. in Physics 1932. Berkeley 1932-34. MIT from 1934; founder of the Radioactivity Center. Starts first course designated Nuclear Physics (January 1935). Strong interest in study of radium poisoning. Radium tolerance in humans, cancer research. World War II work, postwar work; establishment of Laboratory for Nuclear Science and Engineering. The Markle Foundation funds for the Radioactivity Centers Cyclotron.

Transcript

Session I | Session II | Session III

Weiner:

This is Charles Weiner talking with Robley Evans, again. When was the last time we were together?

Evans:

1974.

Weiner:

Unbelievable. Probably a world's record for return of transcripts: one from 1972, one from 1974, were returned today. When we left off in 1974, we'd gotten up to the Conference on Applied Nuclear Physics which was shaping up under your leadership at MIT. And it might be good to talk about that. It represented a lot of the work going on, and also provided a transition, a new departure. That may not have been true in actuality, but at least it's a convenient place to start talking.

Evans:

All right.

Weiner:

It was in October 1940, and it was jointly sponsored by the American Institute of Physics and MIT. When did the thinking on it start? How did you get involved, at what point? I want to talk about the concept of the conference and the planning of it.

Evans:

Well, by that time, by around 1939, there was a good deal of applied nuclear physics, particularly in the sense of the use of radioactive tracers in a large number of fields  metallurgy, medicine, geology, and so on. And we were doing a good many different kinds of projects in our own laboratory at MIT. I had summarized this in an article in the ATLANTIC MONTHLY. I've forgotten the date of that.

Weiner:

The article was April 1946.

Evans:

In any case, there was enough widespread interest in what we called the applications of nuclear physics to justify a get-together for comparison of results, of methods, and of techniques. It was probably about a year before the actual conference that I proposed it, probably to Harry Barton at the American Institute of Physics, and it was considered and approved. Also, of course, to Karl Compton and others, probably Slater, I don't remember any of those details. I undertook to chair it, and we gathered a committee. I believe we met once or twice in the American Institute of Physics headquarters in New York, and various people agreed to take charge of various sections of the work and to chair various sessions. These would include people like Jim Conant of Harvard and Lee DuBridge, and several others whom I don't recall at this instant, but all of whom will be well recorded both in the program, which you have, and in the full issue of the JOURNAL OF APPLIED PHYSICS.

Weiner:

And wasn't Elmer?

Evans:

Elmer Hutchinson was strongly involved, yes. Clark Goodman, as I recall it, helped me a good deal. And I remember that I did practically nothing else for three or four months, in the spring and summer, getting the final arrangements made and the speakers invited. There were, as I recall it, over a hundred invited speakers who presented papers. Of course abstracts had to be received from all of these. It was full week, either five or six days, I guess five, and with overlapping sessions. A very large affair. There was a group photograph taken of a good many of the people, and I think that you have that.

Weiner:

Well, we have a file that shows some of the correspondence.

Evans:

The file of invitees and acceptances and of those present was, I think, disposed of ten or twenty years ago, so we don't have that any more. But the authorship of the papers will show the international character of the meeting. Of course, at that time, in late 1939 and early 1940, World War II was actually under way in Europe, though not with the involvement of the United States. I recall that some of the foreign invitees wrote me wellcoded messages, "You know how much I would love to be there, but you know I can't come." Things of that sort.

Weiner:

According to the breakdown, three people from Japan were there. Do you recall who they were, or do you think maybe in fact that file would show?

Evans:

No I don't recall. We'd have to look and see.

Weiner:

There were three from Japan and two from Canada. I wanted to go back for a minute to the idea for the conference. What did you expect to accomplish by it; what was your motive?

Evans:

An exchange of information. Getting people who were working in these areas together, so that they could hear both each other’s results and the methods being used, which might overlap as useful methods in their own field. For example, something being used in geophysical research might easily overlap in medical research or in metallurgy, as a technique. There was a group of people, of the order of magnitude of probably 150 or 200 in the entire world, who were actively working in this field, and it seemed appropriate to get them together to exchange information. In those days, scientific groups were small. The American Physical Society met very comfortably in the Bureau of Standards in just a couple of lecture halls, and most of the product of the meetings was in bull sessions out on the lawn. Things were smaller in those days, and people with some thread of common interest liked to get together and exchange information. This was the real reason for it. There were a number of people there who were very much enthused by it, by their experience at the conference, and who got an inspiration out of it which directed, so they've told me later, their entire scientific career. They were young people who were just starting out. This has been particularly true in nuclear medicine and related fields. Joe Hamilton from Berkeley, who was present, felt very strongly that this should be an annual event, and that we should plan immediately to have it every year. But then of course World War II broke on the United States, as well as the other countries, and there were no more such conferences. By the end of the war, the field of applied nuclear physics was so big that a given section of it might involve thousands of people.

Weiner:

Also there was a good deal of secrecy imposed, not necessarily for any good reason, but it tended to keep people further from communicating, even in fields where there was no need to. 

Evans:

During World War II, you mean?

Weiner:

Yes. Wasn't there a carryover, though, after the war?

Evans:

After the war? That's right. There had to be a lot of declassification, until we could all get caught up on what the other fellows had been doing.

Weiner:

About the people who were there, according to my notes, which I dug up from four years ago, the total registration was 590 people, and about 100 institutions were represented.

Evans:

Well, then, you see how grossly wrong I was in my memory a moment ago, thinking about 200 people. It was over 500.

Weiner:

Yes, 590 were registered. My assumption is that a good many of them were people from MIT. Well, the specific registration breakdown gives 116.

Evans:

From MIT?

Weiner:

From MIT. That's a very large number, you see.

Evans:

It certainly is.

Weiner:

Your group was not that large.

Evans:

No.

Weiner:

Harvard had 59, Mass. General [Hospital] 18, Rochester 23, Brown 17, Yale 16, Columbia 14, Huntington Hospital 14, Amherst 11, and Princeton 10. Those are the ones that were over 10. The others were lower, I didn't calculate that. I don't know if I got this directly off the table from the file or if I calculated this. Seventy-three speakers were present, 100 papers were given. I was surprised at the large number of people and the large representation from MIT alone. That raises a question about who these people were. Some of them, in various fields, were just trying to learn or beginning to use the techniques of radioactivity?

Evans:

Yes. And some were deep in it. All of them, I would think had some connection with the Radioactivity Center, either in terms of actually a joint program, or of having heard about the work or wanting to apply it to their work. Because here was a tremendously powerful new analytical tool in radioactive tracers, which at that time was being described (in the U.K. particularly) as being the equivalent of the invention of the microscope. It would have just as big an impact on science in a broad way as the microscope had had. I think we were all feeling that that was true, because new things kept developing all the time. I may have told you how the metallurgical studies, friction studies, friction transfer, began with the casual wiping by Jack Irvine of a block of electrolytically deposited copper that was on his windowsill and had Cambridge dust on it. He wiped it with a kleenex, and then just put the kleenex in front of a GM counter for no particular reason, and the counter clicked away like crazy. So he called up his friends in mechanical engineering who were interested in friction and said, "Hey, look what we got, a method of measuring metal transfer in friction." So they started studies immediately, joint studies of this, and rolling friction, sliding friction  learned quite a deal in a very short time.

Weiner:

And basically, the technology involved was a good counter and a lot of understanding.

Evans:

Yes.

Weiner:

Not much else.

Evans:

That's right. Sandy Brown, Jack Irvine and I, at the Radioactivity Center, spent a significant fraction of our time consulting with people who brought in problems and said, "Can we solve our problem with radioactive tracers?" These people came from within MIT, and many of them from outside came to visit. We would always take the general position that if they had some other method that would solve their problem, they should use it. We were not trying to spread a doctrine of radioactive tracers as the only way to solve problems, but rather, if a problem couldn't be solved by some other method but could be solved by radioactive tracers, then, do it.

Weiner:

If you had newcomers coming into a field, working with radioactive materials, which is not just kid stuff, was there a problem of their awareness of proper protection procedures, in light of what was known at the time?

Evans:

Protection procedures were really in their infancy then. There was no fear of radioactivity. Radioactivity was a glorious and wonderful thing, and the radioactive iodine patients received what was recorded earlier, a radioactive cocktail, a glass of water with radioactive iodine  and this was just great. The media loved it. The public loved it. I think we discussed together, in an earlier meeting, the influence of the Baruch Plan, and the deliberate effort by American scientists to frighten the public into joining a treaty with the Soviets, for them not to build bombs and for us to destroy our nuclear bombs, which failed of acceptance by the Soviets. And so our country was left with a frightened electorate and no treaty. This has carried over. Now we have the added influence of the environmentalists and the interveners, all the rest, who've added to the party.

Weiner:

And you feel that the origin of this was the overselling of this treaty?

Evans:

Yes.

Weiner:

Do you think it was misinformation, or do you think it was emphasizing certain aspects of it?

Evans:

It was an overemphasis. Because safety procedures had been worked out very vigorously during World War II. This was the birth, too, of the whole profession of health physics and radiation safety. There had to be protection against plutonium, which was based directly on the MIT work with radium  giving permissible values, and giving a warning that chemists mustn't get even microgram amounts of substances like these in their body, or they might be in trouble. And then, the very large amounts of radioactivity which are produced by nuclear reactors. Of course, prewar and prenuclear reactor, we'd been dealing with microcurie amounts of activity, or at most millicuries; the largest amounts of things that were around in the curie quantity, like a gram of radium, which is approximately a curie of radium. And then, when nuclear reactors began to produce things in the thousands and millions of curies, this was a whole new ball game and required a whole new profession, because it moved up by many orders of magnitude, six or nine orders of magnitude in the strength of radiation sources. Therefore they would have biological effects and you had to protect from them.

Weiner:

It would be something we should get to in time, about how you see the development of the socalled health physics specialty or profession. The reason we got into this now is the conference itself. Is there any breakdown anywhere showing who these people really were? We know where they came from, and we know what they're interested in by the way the papers are distributed. But were they geologists, chemists, physicists, medical people, and so forth?

Evans:

Yes. I don't know how to get at that information anymore. It was all in a 3 x 5 card file that was, as I say, disposed of a long time ago. I'm not even clear how you got the number of people who were in attendance and where they came from. This is magnificent news to me. How did you grope that out?

Weiner:

It's in one of those files [at AIP]. I don't know, directly or not, there may have been a table.

Evans:

Something I had and gave you?

Weiner:

I know I didn't get all those 116 people from MIT by counting names. There was a list somewhere. One of the papers listed in the program, and in the preliminary materials, as of at least April, late April, 1940, [said] special evening talks were to be given. There were five of them. And one of them was to be by Enrico Fermi on nuclear fission and atomic power; it was shown in the program too. He was to be the banquet speaker, in fact. Now, there was no subsequent record of it in the JOURNAL OF APPLIED PHYSICS, and I don't know whether the talk was ever given.

Evans:

Yes, it was given.

Weiner:

Is there any record of it? It would be fascinating to find out what he said to that group, in about the first year after the discovery of fission. It would be very interesting.

Evans:

Yes, it would.

Weiner:

You don't have it?

Evans:

No. It was not recorded. He turned in no manuscript. It was just straight from memory. And my personal recollection of the talk was one of admiration for the extremely simple treatment which he had given to a complex topic  taking out of it just a few simple ideas, presenting those with great clarity, and not giving any overall comprehensive description of the field at all.

Weiner:

What did he emphasize, do you remember? He said nuclear fission and atomic power?

Evans:

I recall now nothing about nuclear power. He may have made a few observations, a few sentences, but my present personal recollection of what he said was that it had to do with other things, such as nuclear barrier penetration and the process and possible nuclear mechanism of fission itself  how it would go on as a physical process  rather than its engineering applications, in terms of a reactor.

Weiner:

What interests me is: it's a conference on applied nuclear physics, and he has in the title "Nuclear Fission and Atomic Power," and for this particular audience (as a matter of fact, I would think for most audiences) the only interesting thing about nuclear fission is its power. What else is there? Power in one way or another, whether explosively used or otherwise.

Evans:

Well, in 1940, that was just something on the remote horizon. Nuclear power plants were something that we all liked to talk about, but nobody designed one for the purpose of producing electric power.

Weiner:

I'd be curious to know what he said nevertheless.

Evans:

Yes. But I have no recollection of his giving anything more than a few sentences, if that, on his view of the future.

Weiner:

Do you have a recollection of how long he spoke?

Evans:

Probably 30 minutes, 40, something of that sort. That would be my guess.

Weiner:

Well, it's one of those things.

Evans:

One of those things, lost, yes.

Weiner:

It would be interesting to see what some of these people did subsequently too. They were representing a pretty good proportion of the population concerned with those issues.

Evans:

Right.

Weiner:

Was there any effect of the conference on MIT, or was this just a consequence of the Radioactivity Center being just that, a center for some of these issues.

Evans:

That's all, I think. There was no other intent, and I don't remember any other consequence.

Weiner:

Well, there's a JOURNAL OF APPLIED PHYSICS article in April, 1941, written by you. You talked of the coming new profession of analytical physicists. You talked of cooperative research teams, and the need for a number of truly hybrid Ph.D.'s who can bridge the gap between physics and other scientific fields. But there's no mention of fission there; you emphasized isotopes and so forth.

Evans:

Well, that would be a prediction, perhaps, of people like Dr. Costa Maletskos who has a triple Ph.D. from MIT, triple major, physics, chemistry, and biology.

Weiner:

When did that happen?

Evans:

He took it in the Radioactivity Center. He would have finished it up postwar, because pre-World War II he was a joint Master's candidate student of Frank Schmidt in biology and of me in the Radioactivity Center, studying nerve impulses and the migration of phosphorus in an isolated nerve, by use of radioactive phosphorus tracing. Then, as he was a member of the active Reserve, he became a radar officer in wartime. Then he came back and took his broadbased Ph.D.

Weiner:

The radar leads me to the next question I wanted to ask. The occasion of the conference was used by Lee DuBridge and others to discuss plans for the establishment of a U.S. Laboratory to develop radar and to further what the British had done.

Evans:

Right.

Weiner:

Were you conscious that that was going on?

Evans:

Oh, very much. Yes.

Weiner:

What's your recollection of this?

Evans:

My major recollection is of the rather large amount of activity going on, in terms of drawing people out of the audience at a session. Someone would come in the door, look around, pass a note along down an aisle, and the individual who received the note would look at it, get up, walk out of the room, and go someplace for some kind of recruiting session. And then as you know, some people didn't leave Cambridge. They just stayed right here. There were no offices, nor any space available, so one or more of the corridors was blocked off and desks were placed in the corridor. This became the very beginnings of the Radiation Laboratory. It got the name Radiation Laboratory as a cover, because Radiation Laboratory sounded just like Berkeley and cyclotrons  MIT, Radioactivity Center  all that sort of thing. That's how it got its name. As I recall, WatsonWatt was here at that time.

Weiner:

At the meeting?

Evans:

On campus. That's my recollection. Really firing people up. Decisions were being made.

Weiner:

When you noticed the people being called out, were you on the platform or just in the audience?

Evans:

In the audience.

Weiner:

Were you aware of why they were being called out?

Evans:

I think so. Yes.

Weiner:

How long did the meeting last anyway, just one day or --?

Evans:

Oh, it was at least five or six. It was a full week.

Weiner:

That's right. All those papers, of course.

Evans:

And it overlapped Election Day, so that those who wanted to vote put in absentee ballots, because it lasted into early November.

Weiner:

So this activity, with people visibly being pulled out of the meeting, this continued throughout the week?

Evans:

Yes.

Weiner:

And you say you were aware of what was going on. You weren't involved in that?

Evans:

No. I wasn't involved in it at the conference. No.

Weiner:

Well, I think there's some good documentation of the Radar Laboratory. There's a study actually going on, on this. Sometimes the story is told  you may be surprised at this  that the Conference on Applied Nuclear Physics was really a front. It was really meant to be the initiation of the Radar Laboratory. (Evans laughs) I really laughed at that, it shows ignorance of that event, of the whole history of nuclear physics.

Evans:

Yes, that's right. It was totally unrelated, except that there were a lot of physicists here.

Weiner:

Well, the various groups of scientists went into various war activities. The Radar Laboratory was one. When was the first involvement of the Radioactivity Center in war work?

Evans:

It was well before Pearl Harbor, if that's close enough for you. 1940 and early 1941, we were certainly working on things which were related to the war effort. For one thing, protection of workers on selfluminous radium activated dials. We were obliged to give permissible levels, for radium body burden, by Captain Charles Stevenson, a medical officer of the Navy. He explained to me, I would either give him the number, or he would draft me and I would have to do nothing else but that. It was from that threat that in May 1941, the levels for safe body burden of radium and safe concentrations of radon for inhalation were set. The body burden for radium became the basis for permissible body burden for plutonium, shortly after, as soon as plutonium became an element of interest. I think we were already beginning to work on surgical shock. These 3 x 5 cards that we had this morning 

Weiner:

The first one shows a NDRC grant in April of 1941.

Evans:

Yes, on radon apparatus. But here the second one on Committee on Medical Research starts November, 1940 and November, 1941. Something's hard to read on the xerox, in terms of the amount of money available for it, for that first year. Now, that's one of the major war problems, surgical shock, both among civilians and among combat troops. Because, for example, in the bombing of London, a typical medical case would be that of a structure which had been bombed, and of an individual who was pinned beneath a wooden beam which was across his arm, let's say, and had been across his arm impairing the circulation in the arm for a period of time. He would be in perfectly good shape when the rescue crews arrived, feeling fine and talking with them and all that. They lift the beam off his arm, and start him toward a medical station; to be sure everything else is all right. He'll go into surgical shock and die. This is an illustration of what a mysterious thing it is. By surgical shock is meant, the blood pressure just drops down practically to zero, there's no circulation and the person dies. It's irreversible. Blood transfusions, things of that sort, do nothing for it.

Weiner:

What causes that?

Evans:

Well, that was our problem. It had been studied in World War I by Walter Cannon and by Joe Aub. Joe Aub was involved again in its study in World War II. Soma Weiss of Peter Bent Brigham Hospital was at first the responsible investigator. He died just a few weeks before Pearl Harbor, and Joe Aub took charge of the program from there on. What we finally found was the cause, was the blocking of the circulation, for example, in an arm removed from oxygenation. There were organisms which could not grow in the presence of oxygen but which could grow in the absence of oxygen, which were present in all tissues; and these little rascals, when the oxygen was removed, would grow and produce toxin at a very rapid rate. Then when this blood was allowed to circulate again, it would diffuse this toxin through the entire body, and there was no way you could correct it. The person would die. Joe finally had that idea, which occurred to him while shaving one morning, as so many of our ideas do. We immediately went to work to test it out with animals and with studies of the organisms in normal tissues of animals and of humans that had [undergone] surgical procedures, to see whether these critters were really there. They weren't universally present, as I recall, but they were very commonly present. So this was viewed as the probable cause. Then, having that pretty well solved  at least, there was not much of anything you could do about it, unless you could develop antitoxin that could somehow be given in time to do some good  the need for whole blood was seen. The maximum time for blood banking at that time was five days. This meant, the blood that was needed by combat troops had to be blood from soldiers in the rear. And this is a difficulty. It would have been far better to be able to get blood donations from the citizens at home and ship it to the battle front. So our task turned then to blood preservation. We developed a new tracer technique, using double tracers of radioactive iron, two different isotopes of radioactive iron, and some very ingenious instrumentation that several of our people in the Radioactivity Center developed, so that these two isotopes could be determined separately in one and the same sample  without any treatment of the sample, just two different detectors. We studied various preservative solutions, and finally found one called ACD1, acid citrate dextrose1. Actually we found it in some British communications or even British literature by John Loutit and R. L. Mollison in England, which they had found by much cruder and poorer methods. It seemed to be a promising blood preservative, but they could not quantify it, as we were able to do with radioactive tracers. It turns out, it was a technician's error in their laboratory, put the wrong stuff in, but John Loutit said, "Well, go ahead and test it anyhow," and it seemed to be the best that they had had. We were trying all sorts of solutions, so we tried theirs. We were cooperating with a large number of medical centers in this country on blood preservation. It was quite an important thing and many methods were being used for studying it. So finally, we found that under the proper conditions and proper concentrations of the constituents, this solution would preserve human whole blood for at least 30 days, with only a loss of about 5 percent  that would be right? It must be more than 5 percent, maybe 10 percent loss of viability of the transfused red cells, and could be transported under ice refrigeration to the battlefront. And so this became the new method of drawing blood from the civilian population in the United States, and shipping it to the active theater. It was used in the Mediterranean campaign and entirely through the whole Pacific campaign. We developed an iced refrigerator made of plywood, approximately two feet cube roughly, that could be dropped by parachute on the beachhead or forest or what have you, with whole blood. Western Airlines, a year or two ago, was celebrating their 50th, I think they called it, anniversary of flying under various names. In their monthly journal that they leave in the seat pocket for Western Airline passengers to read, they had a story about their importance in transporting blood to the battlefront, and they had some pictures of what turned out to be our blood. They had loaded it on their airplanes to be transported with their airline by way of Alaska to the Pacific Theater. It's very interesting.

Weiner:

I'm not sure about the mechanism of this, how this was achieved, how the isotopes were really effective in --

Evans:

Well, they amounted to a tag, you see. What you're doing is tagging hemoglobin, and making hemoglobin in which one of the iron molecules, which carry the central molecules in hemoglobin, is radioactive. You'd not ask an organic chemist to synthesize hemoglobin because he can't do it, but any truck driver can do it for you. You simply give him an intravenous injection of sterile, nonpyrogenic, ferric ammonium citrate in which some of the iron atoms are the radioactive 45day betaray emitting iron59. His body goes right to work, and the new red cells that he is creating are… (off tape) …very nice tagged red cells, tagged with iron59. Then you draw a blood donation from him, an ordinary Red Cross sized blood donation, put it in a preservative solution to be tested, refrigerate it at whatever temperature is appropriate for that particular storage test. You have another man, whom you've also given radioactive iron intravenously, but there you've given him a different isotope. You've given him iron55, which is an electron capture isotope, and doesn't have beta rays or gamma rays mixed with its low energy Xrays. Therefore it's distinguishable with instruments. He prepares his red cells with this other tracer. Then you draw off some of his red cells, say 10 or 20 milliliters, and inject them into a third person, who is to be the recipient of the stored blood. The dilution factor of the first fresh nonstored red cells tells you what the recipient's total blood volume is. Then he becomes his own control. Now you give him the transfusion of the stored blood tagged with iron59. Since you know his blood volume and know the volume of the blood you've given him, you know its specific activity per milliliter of red cells. Then you give him that transfusion, and you wait a few hours and draw off a sample of blood, and see how many of the transfused red cells have remained alive in his circulation. And it's complete; the single individual with the single stored sample is his own control. There's no question about the percent of viable red cells in the stored whole blood. It's a beautiful technique.

Weiner:

This is the kind of thing done here, in the development

Evans:

It was totally developed here at MIT.

Weiner:

But that's not what happens when the transfusion is given in the field.

Evans:

Oh, no, this is a way of testing the solution. Out of all of this you find that out of 20 or 30 or 50 things you've tested, acid citrate dextrose1 is the ideal preservative. You then approve this as a chemical solution, and the Red Cross starts collecting blood in it. All of the blood banks in the United States for many decades, after World War II, used ACD1. If any of us, or if MIT, had one penny of profit per transfusion or per unit of stored blood in the United States, we would indeed be very rich. That came right out of MIT. That blood was supposed to be used within 30 days, but if there was a medical need for it and the blood was older than that and it was in a combat theater, they would use it. It was used successfully in the Pacific Theater at 105 days storage.

Weiner:

Probably not under the best storage conditions either.

Evans:

No. Not with the total preservation of the red cells either. But it did give the recipient the new building blocks for hemoglobin, so that the recipient got some benefit out of even those red cells which didn't survive when transfused. So this became the whole basis of blood banking.

Weiner:

And then, once that was done, I have the impression that it was a continuing operation at MIT, something to do with hemoglobin, that there was almost a production operation. Where do I get that impression?

Evans:

I don't know. It was a long procedure to determine which was the best solution, and which of many variables, not only the chemical constituents themselves, after the three principal chemical constituents had been chosen, but what was their proper relative concentration or total concentration, and percentage volume in the stored blood sample. Then, at what temperature should it best be stored? And could it withstand transportation? We did dummy runs to the Pacific Theater, for example. Army Air Force would fly the blood out and turn right around and fly it back. Then we would transfuse it here. And all of the individuals involved in this  perhaps too jokingly, I mentioned truck drivers as being the proper chemists to make the hemoglobin  these were all military personnel being trained at the Harvard Medical School. They were all medical students in the military service. And they each received a navigator's wrist watch as a reward, because we couldn't pay them any money, they were in the military service.

Weiner:

I'm looking at some excerpts from Livingston's interview, about the cyclotron. The cyclotron ran around the clock during most of the war years, mostly making radioactive phosphorus and radioactive iron isotopes for use as tracers for studies of preservation of whole blood, and the blood fractionation.

Evans:

Yes. You would probably be thinking of Edwin Cohn's blood fractionation studies, but these were almost completely unrelated. Fractionation, no, we weren't involved in that. If he's talking about plasma fractionation, the answer is no. We were only peripherally involved with Cohn's fractionation work.

Weiner:

This is a question about the cyclotron. The isotopes that you used in the preservation studies were developed by the cyclotron?

Evans:

Oh yes, all the activities were made on the cyclotron. As I recall it, we built and installed a new set of dees at Christmas time, one year. Stan [Livingston] may have mentioned that. The purpose of [the dees] was to boost the energy, and the current, and produce more  have a higher yield of these particular radionuclides.

Weiner:

That would mean that the cyclotron, if the dees were changed and if it was focused on a very specific task, became a single purpose machine.

Evans:

Only that it would do that particular task better, and would do all other tasks better, and that it was necessary to do that particular task better.

Weiner:

I see.

Evans:

So everything benefitted.

Weiner:

I see. So it didn't limit its usefulness on other things.

Evans:

Not at all. It enhanced its usefulness for everything. Including its usefulness for pure physics after the war, when it did do some pure physics. Of course, the Markle cyclotron was promised to be 100 percent for medical and biological investigations, when Karl Compton and I got the grant from the Markle Foundation. But it was always, in using our radioactive material, essential to know all of its nuclear properties. And so the study of its nuclear properties, for such Ph.D. students as Martin Deutsch, and others, many others, was pure nuclear spectroscopy, pure nuclear physics, totally eligible for the Ph.D. thesis in pure physics  but at the same time, it was legitimately a part of the usefulness of that isotope for medical research.

Weiner:

I understand.

Evans:

(laughter) Yes. But Stan Livingston and others planned that switchover very beautifully, because we couldn't spare much down time. My recollection is that it was less than two weeks, order of magnitude of ten days, from shutdown with the old dees to installation of the new ones. The new ones were sitting right there on the cyclotron floor, ready to shove in. [There are] photographs of them that I took at the time, and I think one of those is in one of Stan's articles on cyclotrons in the JOURNAL OF APPLIED PHYSICS  several of his photographs are shots that I took.

Weiner:

I think I have a copy right here.

Evans:

It was well planned, so that each step was laid out sequentially. We got lots of extra hands in. Sandy Brown's father was on home leave from American University in Beirut. He joined the group, rolled up his sleeves and worked. Everybody got right in there and got those new dees in, got everything tuned up, and got the beam back on.

Weiner:

Was there ever any pressure to move the cyclotron to Los Alamos?

Evans:

Never.

Weiner:

It was the Harvard machine?

Evans:

The Harvard machine was moved.

Weiner:

And this cyclotron was active throughout the war? Stan's comment was that it was operating 24 hours a day, but that may be an exaggeration?

Evans:

No, that's not an exaggeration. We have good records of operation at 150, 154 beam hours per week. That's on target and doesn't include the changeover time. How many hours are there in a week? 168. So, 150 to 154 beam hours a week is mighty good. And, of course, as always in wartime, the military is overstaffed because they're staffed for peak emergency need, whereas the civilians are understaffed at all times, so that our night shift was a psychiatric reject from the Navy. But the cyclotron was tuned up with automatic selfcorrecting controls, so that it took care of itself. If the beam wandered, there were sensors which would detect this and correct the adjustments and bring it back on beam. There was a strip recorder that was recording the performance all night long. This night man had the privilege of sleeping on a cot, and if the beam somehow was not self-corrected, there was a big fire gong right over his cot which would ring. We have records of his sleeping something like two hours through that fire gong, not waking up to make the correction! (laughter) But we got through. I recall vividly having wondered about our Saturday afternoon and Sunday production of radioactive phosphorus, which was turned over primarily to Shields Warren and to six or eight or more other hospitals, for treatment of leukemia or polycythemia vera. I said, "Shields, it's wartime and we're all working 100 percent on war things. Is it proper for us to be making this radioactive phosphorus for hospitalized or ambulatory patients?" He said, "Yes, it is, Bob, because you don't know who the patients are. I do." (laughter) Later I found out who they were, and they were very important people, including the head of the VA [Veterans Administration].

Weiner:

...That's right. So that was just one of the uses, one of the competing uses. So it wasn't just on a single product. It would work on the blood project for a while, to produce... 

Evans:

 Every week, it would be on quite a wide variety of radio isotopes, all sorts of things.

Weiner:

Was the Berkeley cyclotron producing isotopes during the war, or was it converted to other uses?

Evans:

My understanding was that it was not. Wasn't the big cyclotron on the hill converted right away to the first calutron?

Weiner:

Well, that was the one  was it the one that was under construction?

Evans:

The 184 inch.

Weiner:

Yes, but I was thinking about the 60 and the 37 inch.

Evans:

I'm trying to remember.

Weiner:

The reason I asked was because, throughout much of the thirties, from say 1935 on, the Berkeley cyclotron was a principal supplier to people who needed radiosodium, radioiodine, radiophosphorus, whatever. I just wondered about MIT's role, what the relative position was.

Evans:

We pretty much took that over in 1940. On the blood preservation alone, there were 36 collaborating groups. Not all of them were working on the problem with radioactive iron. But it's an indication of the magnitude of the collaborations. No, I'm wrong. It's not 36 groups on blood preservation alone. It's 36 collaborating groups during World War II, receiving their isotopes for whatever purpose it might be, from the MIT cyclotron. Now, this would involve radioactive sulphur, for example, which obviously would be studied in terms of chemical warfare, and radioactive chlorine, radioactive manganese, radioactive iodine and other things. We studied the distribution of chemical warfare agents of the aqueous type, that is, biological warfare. We were in that, both in the detection of leaks of biological agents in the manufacturing process, (one has to minimize injury to the workers in the plant manufacturing the stuff) and in the design of the artillery shells which would disperse it. We successfully shipped isotopes with a halfperiod of 35 minutes from the MIT cyclotron to Johns Hopkins University, and they could still use it.

Weiner:

How did that work out?

Evans:

We just started off with a lot of activity. We shipped curie amounts of radioactive sodium to the University of Rochester, for their wartime projects, which were heavily involved with the Manhattan Project.

Weiner:

You were in on the ground floor of setting standards for shipping of radioactive materials.

Evans:

Yes.

Weiner:

How did that affect the shipping work that you were doing? It seems to me that those were unprecedented situations that you were involved with during the war, that no one had ever shipped that much at one time, and in fact, some of the activities were really extraordinary, in order to have something left later.

Evans:

Yes.

Weiner:

And it's a crisis atmosphere. The important thing is the use of it. So what governed the standards, regarding the safety and the shipment?

Evans:

We figured out how, in our opinion, it could be done safely, and would not overradiate any passenger or crew member or freight handler. Then I would arrange personally with the manager at Logan Airport; in particular, the American Airlines' manager was extremely helpful. He was an MIT man and a personal friend, and that didn't hurt things any at all. So we would arrange personally between ourselves, that on such and such a date, there would be a parcel, and that should go in the tail bin of such and such an airplane on such and such a flight, to Baltimore or Rochester or what not. Occasionally there were hitches in this, because the employees would not always follow the directions that they were given. But all employees along the line of flight, in case it had some stops in between, as it did in the case of the radiosodium to Rochester, would be instructed from Logan Airport on how to handle that piece of cargo, and where to keep it. The five or so curies of radiosodium that went to Rochester went in the tail bin. And it was supposed to stay there until it got to Rochester. When the pilot landed at Rochester and taxied in, he was met on the apron by a truck from the University of Rochester, loaded with bricks with a cavity in it. One of the people with the truck came out and asked if they had such and such a parcel addressed to such and such a doctor? He said yes. The parcel was given to him, and he handled it with long tongs, and dropped it in the hole in this load, and put a cover on it, staying away from it as though it was deadly poison. The pilot of the plane was watching out his window at all of this, and wiggled his finger and told the fellow to come over and talk to him. Planes were smaller in those days. He asked the Rochester man whether he knew what was in the package. He said, "Yes, I do." "Well, why are you handling it so carefully?" He gave him some gobbledegook answer. The pilot said, "You know, I've been sitting on that all the way since Buffalo." And what had happened was that the ground crew had not followed orders, and had moved it from the tail bin up to the front bin, and indeed he had been sitting on it. It had been right under him. So all hell broke loose on that one, and we went to work with the chief physician of the airline, had all kinds of blood studies done on the guy and all the rest. It certainly did impair the private arrangements for shipping materials for quite a while.

Weiner:

I can imagine.

Evans:

We talked about wings, hollow bins on the wings, and all that sort of thing. But we managed.

Weiner:

This was the extraordinary circumstances in shipping during war, because the general standards that had been established started a bit earlier?

Evans:

Yes.

Weiner:

These were extraordinary circumstances.

Evans:

That's right. After the war, new regulations for shipment of radioactive materials had to be developed. I was chairman of the Interstate Commerce Commission's committee that developed those regulations. They lasted for I guess 20, 25 years, before there was any important modification. They were adopted internationally, and applied to rail transport or air transport or postage. The postal regulations, like so many regulations, are absolutely ridiculous, because they say "no radioactivity may be put in the mails." This prevents your using the mail for anything at all, because with sufficiently sensitive instruments, we can detect the radium content of an envelope, of ordinary stationery. There's nothing that is free from radium. It's everywhere. Gibb's Phase Rule  once two components are admixed, it takes an infinite amount of energy to separate them and get the last molecule out. You can't do it. The radioactivity may be small, but it's not zero.

Weiner:

It's a long shot from Lawrence shipping radio phosphorus in an ordinary envelope from Berkeley to Copenhagen.

Evans:

Oh yes. When L. H. Gray, Harold Gray, visited us here, one of the things Hal wanted to take back to his wife Frey was suet. The British were very fond of fat. They still may be. Suet from the butcher was the important thing. My wife Gwen got hold of several pounds of suet, and then we inserted into the suet some plain sealed glass ampules of radio phosphorus and radio this and that, and sent him back with quite a nice bunch of isotopes, along with his suet.

Weiner:

Radioactive suet. Where was he, at the Cavendish?

Evans:

He was at the Cavendish for a while. He was with Rutherford. He was Cambridge all the way. Then he was the principal hospital physicist, one of the world's leaders in hospital physics, and in the British Hospital Physicists Association, and 

Weiner:

Was he at Hammersmith?

Evans:

At Hammersmith, that's right.

Weiner:

This is another issue that relates to something else I'm doing, but was there a Gray in cosmic rays? This Gray, L.H., is a radioactivity man?

Evans:

Yes, L. H. is a radioactivity man.

Weiner:

And he's the one who did the work with Tarrant?

Evans:

Yes, that's right.

Weiner:

What was Tarrant's first name? This is irrelevant to what we're talking about, but 

Evans:

I didn't know him personally, and I don't remember his initials or first name. I would simply go to the PROCEEDINGS of the Royal Society.

Weiner:

We're looking for some biographical information and we can't seem to get at it. [re Tarrant, see e.g.: L.H. Gray and G.T.P. Tarrant "Phenomena associated with the absorption of high energy gamma radiation," PROC. ROY. SOC. (London) 143A, 681724 (1932)].

Evans:

Yes, that would be hard to find, now. If anybody would know, it would be Jack Boag, in the U.K. Jack is at one of the principal hospitals in the London environs, and is one of the leading hospital physicists in England, and president of their Radiation Protection Society, few years ago. Superb, very high ranking scientist. You'll have no trouble finding Jack Boag. Long time personal friend of Hal Gray's, and he would have known Tarrant personally, I'm sure.

Weiner:

Well, it's just a little reference.

Evans:

It may help. The other Gray that I think of is Canadian. He was doing Xray scattering. There was a longstanding question as to whether the Compton Effect was discovered by A.H. Compton or by Gray. It was by A. H. Compton as we know; among others, the Nobel Committee settled that.

Weiner:

Well, let me talk about other aspects of the war work that did not involve the cyclotrons. One record of that work is cards from the card file of the Radioactivity Center, and I don't think we're really going to talk about all of them, but the ones that you would say were the main ones. You mentioned the breath studies 

Evans:

Oh, the safety work for radium dial painters?

Weiner:

Yes.

Evans:

No one was injured in World War II, although there were at least two thousand people painting instrument dials.

Weiner:

This was dials for aircraft generally?

Evans:

Yes. Dials for aircraft, submarines, all the rest, as well as timepieces, navigators' wristwatches, things of that sort. And none was injured  with protection procedures we had learned from World War I experience with radium dial painters. The permissible value that we set in May of 1941 has held up. It's good.

Weiner:

That's the permissible value for the activity of the radium amount to be used 

Evans:

No  contained in the body.

Weiner:

No, that's after the fact.

Evans:

Oh, I see. Yes, the procedures to be used, you mean. No tipping of the painting brush by the lips. No swallowing of radium paint. Things of that sort. Power ventilation to reduce the radon concentration in the room, keep that rolling.

Weiner:

Then the breath tests were for the workers who were doing this?

Evans:

Yes, that's right.

Weiner:

In case they in fact violated these safety guidelines?

Evans:

Well, they would inevitably get a little bit in their bodies, actually, we've decided, by inhalation of dust  that is, of the dry radium paint in the form of dust fragments. There would always be a little of that in their dial painting cubicle, which is power ventilated. We would test each girl's exhaled breath periodically. Liberty Mutual Insurance Co. was the carrier for the principal dial painting companies around here. And Dr. Williams, Chuck Williams, was vice president of Liberty Mutual, and professor of industrial hygiene at Harvard School of Public Health, and head of the loss prevention department for Liberty Mutual. He and I worked very closely on the safety of the radium dial painters, particularly in the Boston area, which was a rather large enterprise. Chuck would go around to the studio, where there might be 50, 75 girls, each with their individual cubicle, power ventilated, glass enclosed. He'd watch them work, and pick out which he thought would be the ones with the lowest intake of radium, as shown by their breath radon tests. To our amazement, the ones he picked as having the lowest intake of radium were the ones whose breath test showed they were the highest. He was exactly 180 degrees out. That made us wonder why. And the reason was very clear. Chuck had judged them in part on the neatness of their work area and its cleanliness. He found that what they were using was a camel's hair brush, brushing up and keeping their glass covered painting surface nice and tidy and clean. At the same time, they were getting radioactive paint dust airborne, and inhaling it.

Weiner:

Through the very process of cleaning it up, they stirred it up?

Evans:

Stirred it up, yes, resuspended it in the air. That was very easy to rectify. We just put in orders that all cleanup must be wet. They had to use a damp rag. The problem disappeared.

Weiner:

Pretty basic, if you think about it in terms of the effect on the workers' health. If you'd approached it another way, you might not have come up with a solution.

Evans:

That's right. The fascinating thing about it was that the grain size of the radioactive material was substantially uniform at 10 microns india meter, which is thought to be nonrespirable. That is, it won't stay in the lung, but will be brought up by the mucousal escalator in the lung and swallowed. We think this is exactly what did happen. They swallowed it and then it was absorbed through the gut, which in separate studies we know is about 20 percent, even for radium sulfate and dial paint. So we think we know the mechanism as well.

Weiner:

You're saying that the techniques, the study of the actual work procedures, as well as the techniques of detection, resulted in a safe war record?

Evans:

Absolutely. The order of magnitude of 800 or 1000 World War II dial painters have probably been measured at MIT and at the Argonne Laboratory, in the last few years, and they show no residual body burdens and no health effects whatsoever. So the values which we picked in May of 1941 were safe and have held up. All of the techniques and information about it, and typical exhaled breath radon concentration results over a period of months for particular individuals in the industry, were published in one of my papers, I think 1943, in JOURNAL OF INDUSTRIAL HYGIENE AND TOXICOLOGY, I think was the place. It was called something like "Protection of Radium Dial Workers and Radiologists from Radiation Injury."

Weiner:

I see.

Evans:

That did it.

Weiner:

That stems from the earlier work that you had done on 

Evans:

Oh, yes.

Weiner:

The case from Connecticut.

Evans:

By May of 1941 we had 27 cases, I think, that's in an earlier study. We picked it from that, and from the observation that we had not seen anybody injured who had less than, oh, order as I remember, 1 1/2 microcuries maybe, certainly higher than 0.5 microcuries. We gathered for a one day meeting at the National Bureau of Standards. That included really everyone in the United States who had had an active participating role or interest in the safe handling of radioactive compounds. Failla from New York, and Leon Curtiss from the Bureau of Standards, myself, and Harrison Martland from New Jersey. The decision was made on the basis of the 27 cases that had been studied here at MIT. These had come from all over the United States, because physicians had found that we had this facility for making quantitative measurements, and comparing radium body burdens with health effects. We had also been doing  as I think we went over earlier  rat experiments, in which we found you've got to study humans if you want to get results that are valuable and applicable to humans. The decision was made finally, by my presenting all of the data to the group and then, saying, "I feel that the number that we picked has to be a crystal ball number, but it should be a value of radioactive content which we as individuals who know the field would feel perfectly comfortable about if our wife or daughter had this amount of radium in them. And for me, it's a tenth of a microcurie. How do you feel, Martland?" He said, "OK with me, how do you feel Failla?" "OK with me." And on around the table, and we fixed the permissible body burden at 0.1 microcuries of radium.

Weiner:

Do you think that would be the approach you'd take today?

Evans:

It's been praised particularly by people in the U.K., who have been bombarded by their interveners, who get up and make big speeches about scientists or bureaucrats making decisions on permissible levels from a desk top and not thinking about people. Robin Mole, a British scientist of high level, has taken this episode as a beautiful example of scientists thinking about people, in setting permissible levels. He regards it as one of the finest things that has happened, and that, with the small amount of evidence at hand, and the decision to be made, how was the decision made? It was made on the basis of your wife or your daughter.

Weiner:

What I'm getting at, I guess, is the problem in the small amount of evidence, that --

Evans:

-- Yes, that's true. But that's all we had. And there was a war going on, and we had to do it. Then this radium paper of mine that I mentioned, was read by Seaborg, who then suddenly said, "My gosh, if a microgram of radium is a hazardous amount, even a tenth of a microgram, and here we are fooling around with a new substance called plutonium, we'd better look at this. Maybe we chemists mustn't get gram amounts of it spread around the yard." He wrote to Bob Stone, head of the medical effects and protection in the Manhattan Project, and that's how the protection began for plutonium. And the socalled dry box, which was used at Hanford and now everywhere for handling plutonium, was a direct adaptation of the dial painting booths that we developed for the Boston radium dial painters at Luminous Engineering Co., pictures of which are in this 1943 paper. We simply close in the front and put in two gloves. You've got it.

Weiner:

That's interesting. That raises a question about the relation of the work of the Radioactivity Center at MIT to the Manhattan Engineering Project, wherever it was located. That seemed to be a rather indirect application of a study that you did that was seen by one of them to be relevant. Did they turn to you at any time for information about safety procedures in handling radioactive materials? That's question one and two, for the probable effects of a certain kind of radiation released in a certain way, I mean, as anticipated in the bomb?

Evans:

Yes, they did. They had to be quite careful about giving any details. In the design of the Hanford plant, I was consulted by J. J. Nixon and others, who came to visit and to talk about protection from radiation and from ingestion and inhalation of small amounts of highly toxic radioactive materials, such as radium. Without ever the mention of a word like plutonium  which just didn't exist; you didn't say it out loud even if you knew the word. So the Boston experience was transferred directly to the design of the Hanford plant. They came here and asked how to do it.

Weiner:

Did you know what was going on?

Evans:

Not really. I didn't know the details of what it was. I had a pretty good idea of what it was. But I was not directly involved, and so always with a principle of "need to know," we were always very careful in talking with each other and always understood, that's the way we had to be. We gave the other fellow enough information so that intelligent responses could be given, and that was it. Really, the less we knew, the better, provided we could cooperate and help. But my Presidential citation, postwar, reads something like this: "For all radioactivity work done outside the Manhattan Project during World War II." But I also received an A bomb tie tack, for my work inside  I also have the "A", I don't know whether you've seen those? Those who were involved in the Manhattan Project and in the A bomb have either a bronze pin or tie tack, about a half inch in diameter, with the big letter A in the middle of it, and I think in small letters, "Manhattan Project" or something, around the border. I have one of those too. So I was both in it and outside it. From the MIT cyclotron we sent radioactive materials into the Manhattan Project, through the screen.

Weiner:

That was for very specific things, because you were developing instruments and counters of various kinds, and very ingenious devices. What about the bigger problem I mentioned, of the probable effects of radiation on living things? Since you were a pioneer in that, and in fact, a good deal of the studies that have been done at the Radioactivity Center related to that, did they consult you, either in general or on specific aspects of that?

Evans:

Yes. In general terms, without being highly specific about what the particular radioactive substances or types of radiations were, we were all interested and could have a mutual interest without discussing the source. We could have a mutual interest in neutron toxicity, for example, because we had neutrons coming out of the MIT cyclotron all the time and we had to protect our workers from neutron irradiation. So, we were interested and active in that field. The same problem arose, of course, in the Manhattan Project, neutron toxicity, and the same would be true for any kind of whole body gamma radiation. We'd have the same problem that you had on the other side of the screen, of whole body gamma radiation and of internal radiation. We had the long term interest in radium, and its shortlived isotope mesothorium. We didn't need to know during the war that their interest was primarily in another nuclide, plutonium. By 1943, this little chart shows that the radium work was being used as basic reference, particularly by Wright Langham at Los Alamos. He and I were in touch. The rest of the work, the few dogs that were done for the initial toxicity ratio in an animal, were done primarily by Austin Brues, a former M.D. colleague of Joe Aub's and a longtime friend of mine here in the Boston area. So Austin Brues was doing the dogs, and Wright Langham down at Los Alamos and Herb Parker at Hanford were involved in converting those into numbers which would tend to be applicable to humans. This is where the .04 microcuries of plutonium as a permissible body burden came from. That was published by Wright Langham and his colleagues in HEALTH PHYSICS in 1962, after everything could be declassified. But the Manhattan Project, of course, was divided into a number of watertight cells, and Leslie Groves never permitted any multiple site persons, except for a very few, himself and Arthur Compton, a very small number of people. It was only after VJ Day that we could get clearances to visit more than one site. So you were only a one site person. If you knew anything about the inner workings or were involved in Chicago, you could not go to Los Alamos, you could not go to Oak Ridge, and you could not go to Hanford. There were a lot of places at Berkeley where you couldn't go. But as soon as there was VJ Day, then very shortly after that, I remember, I took a circular tour of the whole crowd.

Weiner:

That must have been quite interesting.

Evans:

Yes, it was. I started at Oak Ridge, then Los Alamos, then Berkeley, then Hanford, then Chicago and back home to Boston. Great trip.

Weiner:

Yes. I'd like to get on to that a little bit more, but, the studies you did talk about, even though compartmentalized, were mostly related to the safety of the people building the bomb, is that true? Compared to the kind of thing I was trying to determine, whether there was a way of knowing what the biological effects would be in an explosive release?

Evans:

No. That was certainly not known to me, and I don't know who would have had any information, or any preinformation. It would be my belief that the major thinking, in terms of weapon effects from the nuclear weapons, would be in terms of blast and of thermal injury, burns. Radiation injury, delayed effect, would be one of the last things to be considered. One was interested in stopping a war.

Weiner:

Well, it's true  in fact; something in Groves' file indicates that he was really unaware of what the effects would be. Would there have been a way, if it was determined for one reason or other that you had to know this, would there have been a way to extrapolate from what was known?

Evans:

Yes, there would have been, because that sort of thing became a homework problem in my graduate course in nuclear physics when the war was over  in terms of such matters as the radiation inside the cloud of an air burst, and whether an American aviator who had dropped a weapon over the Soviet Union and who was pursued by MiGs in a clear sky could or could not dive through his own cloud as an evasive maneuver. This involves considerable calculation, but it can be done by capable graduate students in 8.411. At first, that was a calculation with a secret classification on it, which I put through, when asked for it. My conclusion was he could dive diametrically through the cloud. So that prompted a drone experiment at the Nevada Weapons Test Site, and an airburst was made and drone aircraft were flown through it, with mice on board. The mice were tested for change in spleen weight and testicular weight, which are very good indicators of total biological injury. And the answer was yes, the calculations were right, you could. Then it became a homework problem, after it was suitably declassified and the cold war cooled down or wasn't quite so cold a war. And the adjoining problem in that same Chapter 25 of THE ATOMIC NUCLEUS relates to the same question in a submarine. If you have an underwater burst, can you drive your submarine diametrically across the contaminated water? The answer is, yes indeed, no problem in water.

Weiner:

That would be easier to do, in the postwar period, because you know the yield of these weapons 

Evans:

That's right; you'd have to have known or made an estimate of the yield. But of course the yield was estimated, or else the equivalent TNT value could not have been estimated.

Weiner:

That's true, right.

Evans:

This is why I say, it could have been done. But to my knowledge nobody did it.

Weiner:

Even with the secrecy, they could have asked people like you for the techniques, where the values could be plugged in yield A, yield B, yield C, something like that.

Evans:

Yes. That could have been done. But it's my belief; it was blast and thermal type that was being looked at.

Weiner:

The immediate effect, in terms of the military advantage.

Evans:

Yes. Well, see how the bombs were classified. They're not classified in terms of curie gram equivalents of radium, as a radiator, but they were classified in terms of 20,000 tons of TNT, which shows where our thinking was. It was in terms of blast. Indeed, the thermal effects themselves were rather dramatic and surprising. The first medical teams that went in, (and Shields Warren was among the first, he was a Navy commander) found the thermal injuries were very interesting. The Japanese developed keloids from the thermal radiation. Very dramatic effects. I was very heavily involved in another aspect of the Manhattan Project, and that was in the procurement of the uranium for the reactors, the socalled Contract eng13. I gave Helen Slotkin [Evans means MIT archivist Helen Samuels] all the material on it yesterday afternoon. This involved my being the assay laboratory for the purchaser, for the United States, of the Belgian Congo ores, and of the radium separated from the ores. The uranium that we had purchased was separated, like at the Mallinckrodt Laboratory in St. Louis, where they made the uranium oxide, the socalled yellow cake, and then had to save all of the radium. We had to assay that, and make sure exactly how much radium had been saved. Then the United States government had not only to pay for the uranium, but to pay for any lost radium, over and above a given amount, as determined by a secret classified contract called TAB2, which allowed something like 2 percent. It depended on the grade of ore, what percent your uranium ore had. I had that task during World War II and for a number of years afterwards when we were still purchasing Belgian ore.

Weiner:

Let's talk for a minute about  I don't believe we've done this before  your first awareness of nuclear fission. When and how did you hear about it?

Evans:

It seems to me it came through the NEW YORK TIMES. By way of Niels Bohr?

Weiner:

Oh yes, there was an article published. Did you see it through that?

Evans:

Yes. I think that's my first awareness. By what other route might I have heard about it? What are you reaching for?

Weiner:

No, a lot of people learned about it that way, some in the general literature, some spoke with people who had been at this meeting in Washington where Bohr did discuss it. But I was just curious, not only about how you first learned it but about what your response was to it and what happened if anything at MIT?

Evans:

Well, I thought it was great. Because I had a very capable chemist graduate student, Jack Irvine, who was bombarding uranium with the small neutron source that we had  which was just a radiumberyllium source, as he took his degree before we had our cyclotron running. There had been so many papers by Fermi and many others, as well as the French and the Germans, on the socalled transuranium elements. These as we know were wrong, and Fermi's Nobel Prize was wrong, because they gave it to him for the transuranium elements. Pity, because he did so many other things that were right. Incidentally, of course, the Nobel Prize for Fermi occurs in three languages, and the citations are not equivalent. There's an Italian one, and English one and a Swedish one. As I recall it, two of them are based on transuranium elements and the other was not. So depending on which one you read, he's OK. The committee didn't make a mistake. But Jack Irvine was working on his doctor's thesis in the Radioactivity Center on the products of the bombardment of uranium by neutrons. His chemistry was extremely clean and good, and he could not observe these strange nuclides that were being described from Italy, from France, and from Germany. He got only the uranium239, 23 minute, if I recall correctly, isotope, just as clean as could be. He did not find the other isotopes, because his source wasn't strong enough. We'd had many bombardments for radioiodine and things, targets irradiated at Berkeley, prior to 1940 when our own cyclotron began to run. We would make tellurium targets, for example, send them out there, they'd bombard them, or we'd send them to Rochester and they'd bombard them, and we'd get our strong radioiodine sources for the radioactive iodine studies in humans. And one of the parcels I send out was not a target to be put inside the cyclotron, for the internal beam; it was just to be bathed in neutrons for a few weeks, sitting somewhere near the cyclotron at Berkeley. It was several vials of uranium salt. It was packaged and sealed and readdressed to me and had the right amount of postage on it, with their return on it. And we never got it back. On inquiry they said, well, they couldn't find it. Must have been lost. So Jack Irvine came up for his doctor's oral [examination], as I recall it, on a Thursday, his thesis being already written. The only product of bombardment of uranium by neutrons that he could detect was this particular one. The day before his doctor's oral, the news came of fission, and how one might learn what these substances really were. And everything that Jack had done was right. Close, but no cigar.

Weiner:

Well, he's part of a club. What do you think happened to that sample?

Evans:

I'd rather not put it on the tape. (laughs)

Weiner:

Tell me about it sometime.

Evans:

Yes. You can well imagine. (laughter)

Weiner:

Well, let us change the subject. Did you see or were there any discussions here about fission, its implications? You were nuclear physics at MIT, you were the basic group.

Evans:

Yes.

Weiner:

So this would affect you mostly. Was there any discussion or was it pretty early and not really closely related to the things that you were doing?

Evans:

No, we were very much interested, instantly, in terms of the nuclear physics involved and the things that might come from it, both the radioactive nuclides and the physical process itself. Only there was some delay time of course in the discovery that there were more than two neutrons emitted in fission. This came out at the following American Physical Society meeting in Washington, when Fermi did a paper and described it. He made some very cryptic remarks about the possibility of utilizing the neutrons, and said, "I think this is a very interesting subject and I intend to study it." And sat down. I never before heard any speaker in any Physical Society meeting get up and say what he thought he was going to do next, and come and tell the boys about it next year. He did. That's all he said.

Weiner:

This was early in 1939 and 1940; you spoke on the subject there.

Evans:

Yes.

Weiner:

Had there been any, despite this problem with the thesis, were there any immediate efforts to confirm fission by using the cyclotron here? It would have been possible?

Evans:

Not in 1939. We couldn't have, because we didn't have a beam, you see, until October, 1940.

Weiner:

OK. So you really weren't 

Evans:

We were in full production on the last day of October and the first of November, 1940, at the Conference on Applied Nuclear Physics.

Weiner:

But you don't need a cyclotron to first do the confirming --

Evans:

No, but it's a big help, believe me. Small sources are  you can produce microcurie quantities if you're lucky. But radiumberyllium neutron sources --

Weiner:

At this time, what was happening with Van de Graaff's generator?

Evans:

My recollection is that Van didn't yet have a suitable beam. You recall from our earlier conversations that when I'd asked him earlier on whether he could produce radioactive materials for us, he had suggested that no, he couldn't and that we build our own electrostatic generator. I had had a short discussion with Karl Compton, who said he was the "yes man" and he would say yes, but Van Bush was the "no man,” and I'd have to see Van and see whether it got by that. I spent an afternoon with him [Van Bush], during which we got in a few sentences in between his telephone calls, and explained to him that many nuclear reactions have high energy thresholds which can't be reached by a Van de Graaff machine, and that it's not just watts on the target but it's volts as well, and more volts and fewer watts is perfectly acceptable. In fact you get (an area) there where you get zero yield with the Van de Graaff machine, and for that reason, even though this was the center of the development of electrostatic machinery, I wanted a cyclotron. And he agreed. That's when Karland I went to the Markle Foundation. You found some other information, reported in a transcript, that there had been other explorations that I really was not a party to. Hadn't even known about them. Van was having troubles with the ion source. That was the big problem. And Eddie LaMar and the rest, the Van Atta brothers, were hard at work on the ion sources.

Weiner:

I'm a little concerned about time. We've covered a good deal of the war. Do you think there's anything more in the war period that's major?

Evans:

That's super-duper, well, let's see  These cards, of which you have xeroxes here, have some interesting things on them that I don't recall whether we've ever discussed. We might spend a moment or so.

Weiner:

It depends on how much time you have.

Evans:

We have another few minutes, or I can phone the office and see whether Dr. Chalfen has come yet. Indeed I could have them phone us the moment he does get there, unless I'm needed before that for preparation for him. Things, for example, having to do with land mines, a considerable amount of that. Pretty well coded. Things like MAMI  marked mines, MA for marked, MI for mines. MAMI. This was the Army that gave us that code name for them, for marking of friendly mines, laying booby traps. We had been receiving from time to time at the Radioactivity Center a number of captured objects, both through military sources and through intelligence sources, which we have always been coupled into. One of these was a German land mine captured in Italy and sent to us. It was a wooden box, about 15 inches square and three or four inches thick. We opened it with care, and it contained blocks of dynamite, one of which was hollow, but thank goodness it didn't have a detonator in it. We Xrayed it before we opened it, and we had been concerned somewhat even about Xraying it, not knowing the influence of radiation on dynamite. So we did it with very great care, down in the basement of Building 4, as I remember it. In it was a little packed of powder, or sand, and we took this out. This mine was totally nonmetallic, so you couldn't pick it up with metallic mine sweeping equipment, no brass or anything. We took this in and measured it, and indeed it was radioactive. It had radium in it, a good amount of radium. And from its character and the specific activity, I guessed that it was simply uranium ore, crushed uranium ore, used as a quick and easy source of radiation and as a radioactive marker of the mine. We were already thinking in terms of radioactive markers, and of other kinds of methods of detecting a change in density with depth, by using reflected gamma radiation, or other applications of the Compton Effect, with sweeping  trick instruments that would be radiation dependent, and you'd sweep the ground with them. Well, an interesting thing about that material was that I turned it over, I guess it was to Tony Gaudin  I'm not exactly sure  for uranium assay. And lo and behold, it had almost no uranium in it at all. It was a uranium ore residue, after removal of uranium. This was one of the first indications in this country that they had a uranium program going in Germany  the war was still on.

Weiner:

Goodness, what year was that?

Evans:

This was long before the Alsos Mission.

Weiner:

Do you recall a record that would show when that was? That would be really interesting.

Evans:

It wasn't a project, you see, had no DIC number. If MAMI has a card here (and it should have a card…)

Weiner:

You showed me one before, there it is. 

Evans:

Here's MAMI. MAMI began in November of 1942. So at least our activities in radioactive marking had begun by November of 1942, and had of course been discussed for some time before that. It was in NDRC Section 17.1. I see you remember that we have discussed this, in the previous interview, including the fact that Van Bush wrote about it in SCIENTISTS IN WAR TIME, and declassified it by writing about it. In any case, the Engineer Corps of the Army had developed plastic and ceramic mines, which were totally nonmetallic. And the land mine being a defensive weapon, which you leave behind as you retreat and which you want to recover when you again advance, you want to be able to dig it up without blowing yourself up in order to find it. What we developed was a marker which looked like a pebble  what it actually was, was a ceramic casting of a pebble, several pebbles in fact of different shapes, from the North Shore, picked up by Professor Norton and made by the thousands in ceramic molds. Then we would add five microcuries of cobalt60 to that, and sinter it so that it was turned into the oxide (which was insoluble in rainwater and acid). Then you dig the hole for the mine, you put the mine in, and you drop.

Weiner:

You don't have to do anything on the mine itself?

Evans:

No, nothing on the mine, and if the enemy captures the mine, they probably aren't going to find the marker. It will just be part of the dirt.

Weiner:

Right.

Evans:

They'll take it back to the laboratory, and to our opposite number on their side, and say, "How do these guys detect these things?" And there won't be any radioactivity in the American mine. We made thousands and thousands of those markers for land mines.

Weiner:

It was very much an engineering and a production operation in some of these things 

Evans:

That one was. That was just cranking out cobalt from the cyclotron as a production item, and cranking out pebbles, in ceramic.

Weiner:

But you had the use of the shops, you could 

Evans:

 oh yes, sure. We had the cooperation of everybody we needed around the Institute. We always believed in cooperative work.

Weiner:

But a good deal of the work, from flipping through the cards on instrument development in that period, was for those specialized operations.

Evans:

Yes. Among other things, we were very closely associated with what MAMI is, the development of the instrument whereby you find your own mine  which is a highly sensitive GeigerMueller counter on the end of a probe. And then a fancy circuit, so that the Army GI who is using it, sweeping an area, doesn't have to be trained in GeigerMueller counter clicks in an earphone, but has instead a thousand cycle note in his earphones which gets louder as he gets nearer the nearest source. So we had to develop a circuit, which we did  a balanced circuit somewhat analogous to a Wheatstone bridge, which regulated the intensity of a thousand cycle note, based on the counting rate that was coming in the other end of the circuit.

Weiner:

And you had to package it so it was small enough and durable enough for military purposes.

Evans:

That's right.

Weiner:

Well, it's getting to be that time. That doesn't give us a complete picture but it certainly gives us the flavor of what was going on, and how the war affected you.

Evans:

Yes.

Weiner:

You've already stated, in the earlier interview, about the postwar transition, and how essentially things took a different turning the Laboratory for Nuclear Science. The records of that are preserved. You were involved in the early stages of that.

Evans:

Right. And I think I turned in to you a complete set of minutes of the Advisory Committee from Day 1.

Weiner:

Right. The thing to do perhaps at another time is to take a look at the professional cluster of specialties in health physics and nuclear medicine, radiation protection, things of this type, as it developed and blossomed in the postwar period. That's another career for you, essentially.

Evans:

Yes.

Weiner:

Something in which you've been a central figure.

Evans:

Yes.

Weiner:

That may require a different kind of preparation for me to read a different kind of literature. So I'm ready to keep another session in mind for the future.

Evans:

Fine.

Weiner:

And meanwhile, I'll have this transcribed and get it back to you.

Evans:

And I will read it in less than four years.

Weiner:

Nowadays we send out letters which specify a date, and if it is not returned by that date, we assume that you are authorizing us to deposit it in the archives as is.

Evans:

That's good. Fine.

Weiner:

So, thank you.

Evans:

Give it more than two weeks, though, won't you?

Weiner:

Yes.

Session I | Session II |Session III