Raemer Schreiber: I think the only point that is of any interest in this regard to pick up is perhaps the fact that the group of us who came here to work on the so-called water boil reactor had been working together at Purdue University on the very first measurements of the so-called deuterium tritium cross sections, which has to do with the fusion reaction. This eventually was used in bombs, but not for many years, and it is, of course, the basis for present attempts to create energy by controlled thermonuclear reactions or fusion reactions. At any rate, we were invited to come to the laboratory. The invitation was actually made in the spring of ’43, but we did not finish the job there until the fall.
Stephane Groueff: Where did you work before you came?
Schreiber: When we came?
Schreiber: We came into the so called water boiler group. The water boiler was the first measurements of the enriched U-235 in a water solution, which is not exactly related to the eventual bomb physics, but these same types of calculations, which go into the bomb physics, go into this. There was not enough material to do a real mock up so the various people concerned got interested in how can one at least do a secondary check by saying, well, “the calculational methods, the numbers, the constants that are used will apply someplace else, and we only have to start with a few grams of this material and eventually will never have enough to do the complete mock up. But can’t we get some handle on this?”
So that was the basis for the so called water boiler experiment in which by putting the available separated U-235 into a water solution you made it more effective in producing a reaction, so this was the job that we had.
Groueff: You came from where?
Schreiber: From Purdue University.
Groueff: The whole group was there?
Schreiber: There were four of us there; Dr. [Marshall G.] Holloway, [L.D.P.] King, Dr. Charles P. Baker (who is now at Brookhaven), and myself. We then joined up with Donald Kerst, who was the inventor of the Betatron earlier and had come here earlier. The five of us then constituted this small group with lots of help from so-called Special Engineering Detachment (SED), which were technically—they were essentially GI technicians and then a few other more junior scientists.
We built this and we started out with just an open spot down the bottom of the canyon here and working with the Army Engineers drawing pictures on the snow we got a building built and we got this reactor put together. It was brought up to its first operation in March of ’44. [Enrico] Fermi was at the controls in this particular occasion as he had been on—I guess this was perhaps the third reactor he helped create and build.
Groueff: He came to see it?
Schreiber: He visited here all during the war. The interesting situation there was that we were attempting to build a reactor at a rate which kept up with the product of U-235 at that time as it was separated and so we would get another fifteen grams, the chemists would put it in solution, stir it up overnight and then the next morning we would do another measurement on the reactor to see how far we had to go. A number of us had different experiments there to try to guess—the scientific word is to extrapolate—from our measurements, to predict the critical conditions. So there was quite a competition.
Groueff: This material was coming from Oak Ridge? In what form did it arrive?
Schreiber: I suspect it came in a—I don’t know if it was an oxide or a chloride.
Groueff: In a box or in a bottle?
Schreiber: It was no doubt in a bottle. It was brought by carrier and there would be a shipment about once a week. Regardless when this came in, if it were on a Saturday night, it was put in that night and we made our measurements on Sunday. At any rate, we did succeed in this and the measurements, as it turned out by a happy combination of two mistakes, exactly checked, but nothing was really off badly. But it wasn’t as good really as the prediction.
Groueff: You made two mistakes?
Schreiber: There were two mistakes in the basic calculations which compensated each other. That is what you might call happy intuition.
Groueff: Did Fermi watch it very closely?
Schreiber: He was here quite intermittently at this time. This was when the Hanford plants were also being built so he would only come at intervals. I really don’t know but I suspect he was in pretty close touch by way of telephone or telegraph. He was actually here during the last crucial weeks when we had enough material to predict that it would indeed go critical and become a self-sustaining reaction.
We coached him a little bit at a very primitive console and he took charge at a time he thought it was ready to go and indeed it did come up and you could take away the neutron source and the reaction continued. It leveled off and everybody felt very gratified because that was one of the things. None of us had ever heard of it. We had heard vaguely about the chain reaction but you hadn’t experienced it. To see the thing really sitting there living under its own power was really quite a sight.
Groueff: That was after the Chicago one?
Schreiber: I believe the Oak Ridge.
Now, I don’t know what state of affairs was going on in the production reactors at Hanford. They must have been going at this time. I perhaps shouldn’t say it was the third one. It was one of the earlier ones. There was the very first one which was so tiny—it was only a 30 cm diameter sphere, you see.
Groueff: How big?
Schreiber: A foot in diameter.
Groueff: I imagined it was something in the building of—
Schreiber: Oh no. It sat on a little table. We had to put reflectors around it.
Groueff: It was small because it already was enriched?
Schreiber: It was enriched material and it had the water. The hydrogen and the water slows down the neutrons and makes their effective cross section bigger.
Groueff: What did it look like physically? On a table?
Schreiber: It looked like a horrible mess of dirty, black bricks about three feet across and with all sorts of stainless steel pipes going in the top and bottom and so on. Buried in this, the bricks were actually beryllium oxide, which is one of the best reflectors of neutrons. Inside this was a stainless steel vessel, which held the solution.
Then we had all sorts of devices for pushing the liquid up into this reflective region or safety devices, that if you push the button or if a radiation monitor says it is too high—the reaction rate was too high—it would open a valve and then the solution would all flow down into a big shallow pan so that a reaction would stop.
Groueff: Why was it called water boiler?
Schreiber: Well, it had water and if it got too hot it would boil and you were looking of course—
Groueff: The water was around it?
Schreiber: The uranium was in solution. It was uranium. I don’t know if we were using sulfate or nitrate, but it was so you dissolve up any—
Groueff: You couldn’t see from outside the water?
Schreiber: It was all contained. You couldn’t see because you—
Groueff: I imagine something like an aquarium, something plunged into water.
Schreiber: Oh no. This was just a big, yellowish vat of solution which contained the uranium in its chemical form.
Groueff: Do you use it here to understand the nature of the heavier uranium-235?
Groueff: Not directly involved with the production of the bomb?
Schreiber: That’s correct. It was more to get the physical constants which had to go into the calculation of the bomb.
Groueff: Was that part of the theoretical?
Schreiber: It was the experimental physics part of the business.
Groueff: Under [Robert] Bacher?
Schreiber: I think this was under Bacher, yes.
Groueff: I’ll find it in the books.
Schreiber: I’m not sure if it was under Bacher or under John Williams now, come to think of it. We didn’t worry much about the organization. We had that job to do and proceeded to do it. The water boiler then went on to a more elaborate device. This could only run at a very few watts of power because we had no shielding. We did stand behind a five feet concrete wall when we were running it but that was about the extent of it.
Then we later took the same basic idea and put it in a great big cube of concrete so that we could run it up to powers of a number of kilowatts of energy, which doesn’t sound like very much in terms of energy, but it is an enormous amount of radiation. So I wanted to have three and four feet of concrete around it.
Then we used it really as we used research reactors. We got the neutrons from this and then one could do more realistic experiments. By that time one actually had little sections of metallic U-235 in the form of foils or plates and you could expose these to the neutron beam and count the secondary neutrons which came off. In fact, later on, we did a multiplication measurement with metallic spheres which then began to approximate more closely the behavior of the bomb itself. One could get so-called multiplication measurements, how many neutrons appeared as a result of the collisions and the fissions inside the core for each neutron which impinged from the water boiler Quite a number of experiments of that sort were gotten.
Then, as far as if they are tracing my personal involvement, by the fall of ’44, we had the improved water boiler done and were using these measurements. In the spring of ’45, I left that group to join up with the group which was then under the— Bacher had shifted over to the practical question of, “Alright, we have now all of the pieces of the implosion bomb. How does one now really assemble this and make it work? How can you assemble it without destroying all the symmetries and fine points using real materials and not something which the theorists has thought of?”
So he [Bacher] had formed a small group there to look into the practical aspects of combining the high explosive and the nuclear core and doing this in a fashion which you could do out in the field, first down at the Alamogordo test.
Groueff: That was about the plutonium bomb?
Schreiber: Yes, I switched signals here. The U-235 was used in the dunk tank assembly and this, while not terribly efficient, you could check it quite well. There was very little doubt that it would work as performed. On the other hand, it was felt that the plutonium assembly which had use of this implosion system was at some doubt and it would be essential that one have a test before attempting to use it in the war.
That was the basis for the so called Trinity Test operation which was done in central New Mexico. It was in preparation for this and in support of the Japanese combat use that I was asked to join this group with the specific task of determining what tools, what equipment, what support things would be required in order to carry out these operations. I was given a blank check to get any tools from the stockrooms or order them if I couldn’t find them there or to have instrumentation build.
We also had to have ways of monitoring this to feel we knew what was going on. Particularly, in the case of the implosion device, it was rather ticklish business because the size of the bang—the yield which one gets— depends upon how highly super critical one can get this assembly finally. The closer you start to a complete reaction with the inert assembly, the higher the yield would be. Nobody was quite sure just exactly that everything would work out as planned.
Groueff: You knew the inert assembly needed a mechanical—
Schreiber: Before the implosion. You would like to have it sitting there almost ready to start reacting but not quite.
Groueff: If it exploded, it would be a kind of bomb, no?
Schreiber: If you make a mistake and it is—
Schreiber: More than critical. When you are loading up, well, that’s that. It was quite important that you do the experiments to first determine as positively as possible that everything was exactly according to the calculations. Then we actually did some mock up assemblies to verify that the cores that we were using were hot enough to—
Groueff: Nearly critical?
Schreiber: Nearly critical but not super critical and then, furthermore, to make the people in the field feel a little better, we had to develop equipment which we could take along and monitor the assembly, which was then made very slowly and say…It’s alright. You’re 95% of the way there and that is where you are supposed to be. This was my job.
Groueff: Where was that done? In a building?
Schreiber: This was done over in the so called Ice House, which was our first critical assembly area which was right in the heart of the Tech Area. It was called the Ice House because it—
Groueff: At Los Alamos?
Schreiber: Yes, it is over here where the pond is now. It was called the Ice House because the old Ranch School used that as their ice house. They would cut ice in the winter and put it in this stone building.
Groueff: What did the room look like? Was it just a laboratory?
Schreiber: It was made of field stone. What we had done is to install heating and some florescent lighting and lots of electrical outlets and move in.
Groueff: And the metal was there, physically in a room that you were touching with what? With gloves?
Schreiber: Yes, we were—
Groueff: Did you touch—it’s not radioactive or dangerous to your life?
Schreiber: Well, if the plutonium, you never handle it bare because it is quite toxic because of the strong Alpha activity. But this was protected by being put in shells—inert metal.
Groueff: This part wasn’t your job. You received this already assembled?
Schreiber: We received this already assembled.
Groueff: Assembled with a damper and—
Schreiber: We received the individual parts.
Groueff: And the explosives?
Schreiber: The explosives were another group but they made a hole in them and we put the nuclear material in this. This part, this final assembly, was never done here in a populated area.
Groueff: Explosives and not the initiator? Just the metallic core of the—?
Schreiber: The core—let me go back here. In the Ice House what we did was assemble the core, get the techniques for making sure it was as perfect as possible, and that it met all the specifications. Then we packed it up.
We also then at one of the outlying sites made up a mockup of the high explosive. A mockup, if you look at it from a neutron point of view, it had the right kind of elements in it. It was not an explosive. We checked our calculations, which had been made. The first time that the high explosive and the nuclear core got together was actually down at Alamogordo and we did this out in an old ranch house there, at the so-called McDonald Ranch, which was an abandoned—
Groueff: Down in Alamogordo?
Schreiber: Yes. It was an abandoned homestead. We had moved down everything, diesel generators for electric power, all of the tools and so on. We did the assembly of the nuclear components there, moved them over to the zero point tower and gently lowered the assembly into the hole in the explosives.
Groueff: You were in this group assembling Trinity?
Schreiber: Yes. This was a case, which I think has been written up but, this capsule which we lowered in got about half way in and stuck about halfway into the assembly. Everybody said…Uh oh, we’ve had it. Until they realized that plutonium—being alpha active, radioactive—generates heat and is in fact quite warm. You can burn your fingers on a bare piece of plutonium if it is not cooled a little bit. The rest of the assembly had been sitting out there overnight and was quite cold so you waited just a minute or two for the equilibrium—
Groueff: It expanded?.
Schreiber: It all went together alright.
Groueff: In other words, you worked for this assembly for the Trinity and the bomb in Nagasaki?
Groueff: That is where you sent some of the components overseas and you kept others for Trinity?
Schreiber: Right. The first core that was made was used for Trinity. In the meantime, the second one was being assembled and then this was flown over on July 25th. I was a technical courier for that. This was the case for one small box, a larger box of documents, a security guard and technical courier, namely myself had not only one C-54, but a spare C-54 flying along behind us.
Groueff: Where did you fly?
Schreiber: We took off from Albuquerque, having gone down by car in the middle of the night. We flew to Travis which is a military airport near San Francisco and took off twice actually. We lost an engine the first time and we used that spare airplane.
Groueff: You did use it?! Lucky you had it.
Schreiber: We got into Hawaii sometime early in the morning, got another plane almost immediately and went on and that same evening. Except I’ve probably got confused on datelines—we landed at Tinian.
Groueff: Carrying all the documents?
Schreiber: The box of documents, I think, was a blind largely. It had a few precious pieces of paper no doubt, but the important thing was to get this little yellow box out there which had the plutonium core.
Groueff: How big was it? In a suitcase?
Schreiber: I carried it around. The box itself I guess was about a foot on each side and the core was much smaller.
Groueff: Rather heavy probably?
Schreiber: Rather heavy.
Groueff: When was that? What date?
Schreiber: We left on the morning of July 25th. I was down at Trinity and the rest of the assembly crew involved for the combat operation had left earlier to go out and set up the laboratory, which had been shipped out. I was then the person who had to transmit the information from what we learned down there at Trinity out there.
Groueff: Who was your counterpart there? Baker?
Schreiber: Charlie Baker was in charge of the Tinian assembly.
Groueff: So what you were doing here, he was doing there?
Schreiber: He was getting ready to do it.
Groueff: He had all of the bombs except for the plutonium and you brought the plutonium and the information about your experience and gave him a few—
Schreiber: I should make clear that he only had the responsibility of the same job of inserting the nuclear material and verifying that everything was alright. There was a whole separate assembly crew for the HE, for the ordnance, the arming, the fusing and so on. There was an enormous cadre of people out there.
Groueff: Your and his part was just inserting the metal though? The plutonium?
Schreiber: Yes. There was another assembly crew who assembled the gun device, which was used in Hiroshima.
Groueff: But they had already—you didn’t carry with you the other components like the explosives?
Schreiber: No, they had been shipped out, some by ship and some by air freight. They were all there.
Groueff: What did Dr. Baker say about four kits sent and two kits were kept here?
Schreiber: These were the assembly kits of all the tools and the radiation instruments.
Groueff: The kits were not to work with the real bomb?
Schreiber: These were just the supplies. The tool kits.
Groueff: He said they were sent there without being tried here.
Schreiber: Right. There wasn’t time. They had to go by ship and they had to leave a couple of months earlier. What you did was to put in everything you could possibly think of [laughter].
Groueff: In your particular work on the assembly, what were the most difficult, critical problems? If I understand it correctly, you didn’t work on the shaping of the metallurgic part, whether how to work this plutonium or what shape to give it. You were more in the theoretical and also the measurements?
Schreiber: Yes. I think the most difficult problems probably were, technically, to make sure that these various pieces, all of which have been made in an enormous hurry and in different places, would indeed fit together. If you change something here, everybody else that had anything connected with that would know.
From the mechanical standpoint, the other problem was, “what is good enough?” None of these things came out perfectly. As you said earlier, the making of plutonium is a horrible thing to do because it is such a difficult metal to work with and to maintain close tolerances is very difficult so one had to put in little shins here and there. You could, of course, work to any sort of precision you would like and the question was, when did you know enough to stop? If you squeeze things up too much maybe you crush something and that wouldn’t be good either. There was an awful lot of uneasiness about how far you should push.
Groueff: And also the time element.
Schreiber: There wasn’t much time to stop and think about this either. The other thing, of course, was the somewhat mental hazard of knowing that you were dealing with a potentially hazardous assembly. It was interesting that all of the high explosive experts were the ones who got shaky when the nuclear people were doing something and us nuclear people always got a little shaky when the high explosive people started moving things around but it came out.
Groueff: In what outfit did you work with this? Were you protected by some mask?
Schreiber: No. We wore protective coveralls and gloves in case the plutonium coating should have a leak in it.
Groueff: But you could touch the plutonium and be in the same room?
Schreiber: Oh yes, you handled it with a glove on because the alpha particles don’t penetrate but it will be stopped by a piece of paper.
Groueff: What about your face?
Schreiber: You wipe it off, if you get some on your hands and then wipe it on your face or if some comes out in the air—
Groueff: So not very dangerous. But what about your face? If you have it on the table would it be dangerous for your face?
Schreiber: No. As long as it is protective film, metal coating or nickel or something. As long as that is intact then there is only a very mild radiation but if that coating is scratched then the plutonium will migrate because it is very radioactive and it is like popcorn.
Groueff: Then it’s dangerous?
Schreiber: Then you want to have protective clothing on and in fact, you want to go away from there for a while.
Groueff: This assembly thing, what color is this metal?
Schreiber: It was shiny.
Groueff: A steel color?
Schreiber: I think the coating was actually nickel so it had a typical nickel appearance. Plutonium itself, if you view it in the dry box, is also metallic. It looks like lead. Very characteristic of lead except it oxidizes and turns sort of gray.
Groueff: In the final stage of this work, when you worked on the critical assembly, was Dr. Oppenheimer working with you or around you?
Schreiber: Yes, he was pacing around, watching the operation.
Groueff: What was his manner of working? Nervous?
Schreiber: He was pacing up and down. He was quite careful not to bother anybody. He was very good in this regard. He assumed everybody knew what they were doing and if there was anything he should know, somebody would come and tell him about it. He stayed pretty much in the background.
Groueff: Not at all bossy?
Schreiber: Oh no, no.
Groueff: Was he friendly also with the younger scientists?
Schreiber: He was very nice to the younger scientists.
Groueff: It wasn’t the relationship of the big boss and the subordinates?
Schreiber: Not at all. He was very humble himself. He never presumed on his rank and he was quite upset because this was under Army jurisdiction that there was a feeling that somehow he ought to be put up on a pedestal and ordinary people shouldn’t touch him. He was very much the common man.
Groueff: How did he follow your progress? By you giving reports and conferences or he would come to your lab and watch what you were doing?
Schreiber: He normally did not have time to come to the laboratory. He would, on important occasions, but he relied very heavily on frequent primarily verbal reports. Whoever was in charge of the work would see him, perhaps, every day or two.
Groueff: You would?
Schreiber: In this case, I did not particularly because I was reporting though [Marshall] Holloway and he would keep Bacher advised and then periodically, sometimes we would have a meeting of everybody.
Groueff: So Bacher had the responsibility of this?
Schreiber: Yes and he kept in quite close touch and he would be around.
Groueff: Was General [Leslie R.] Groves around?
Groueff: Never around you in the labs?
Schreiber: I think he was present for the startup of the water boiler and that is about the only time I saw him in the laboratory.
Groueff: And you said Fermi was present?
Schreiber: Fermi was present, Oppenheimer was there, Bacher and two or three other dignitaries.
Groueff: Was it a kind of solemn occasion?
Schreiber: It could have been. No, everybody was quite confident. Those of us who had been watching this thing for weeks and living with it drew a sigh of relief when the pen rose and leveled off and everyone was quite exuberant after that.
Groueff: That was in the building of the water boiler, which is far away?
Schreiber: It is two miles away.
Groueff: Not in Los Alamos, I mean. Not around the pond?
Schreiber: No, it was far enough away that it was reasonable protection.
Groueff: Tell me on the Trinity operation, where did you watch it from? You personally.
Schreiber: I was sitting down by the water tank at base camp. There was a windmill and an elevated wooden water tank there. In fact, we were sitting underneath it until somebody said, “Well now, maybe this will shake things up”.
So, we moved out of the way. At that stage of the game we were purely observers. We had done our job the day before.
Groueff: You didn’t do the assembly for the test?
Schreiber: All of this work was done the previous day and was done before the test device was raised up into the tower. It was raised up live.
Groueff: What was done from the tower was just—?
Schreiber: It was monitored and then the electrical circuits were completed and it was triggered.
Groueff: That happened several hours later?
Schreiber: There was a whole sequence. We hadn’t invented the word but now you would say it was a countdown, which started actually about two days before. We had a certain time during which we were to—
Groueff: And you slept out there in the desert?
Schreiber: Yes, we slept out in the base camp which was quite primitive.
Groueff: With tents?
Schreiber: No, there were wooden barracks.
Groueff: Could you sleep?
Schreiber: About an hour and a half, I think.
Groueff: Were you very nervous?
Schreiber: It was a feeling of quite extreme tension. It was compounded by the fact that the weather was terrible. There were a couple lightning storms that night and there was a reasonable chance that it would be called off or postponed for a day, in which case nobody was quite sure of what the durability of all of the components were.
It was not only the big event but a question of, “is it really going to happen?” Every time there would be a bulletin or the least bit of gossip everyone woke up and said, “Huh? What? What did they say now?”
They wanted to do it in dark, you see, in order to do a lot of the diagnostic work, high speed camera photographs of it and so on. It had to go in the dark and it was also supposed to be clear enough so that the diagnostic aircraft who were sensing the instruments could sense blast gages and so on and could orbit on the tower, which had a bright light on it.
All in all, the weather didn’t help matters at all. We were instructed and we were given welding glasses to hold up to our eyes. In fact, we were all instructed to turn our backs on zero point until the all clear. Of course, when it got to zero and here went this enormous flash of light—
Groueff: You saw it through the welding glasses?
Schreiber: Yes, you were almost blinded there. It was pitch darkness and so it really flared up. I swung around and saw the ball of fire through the welding glass and it was getting pretty dim in that but it was enormously dense glass. I took the glass away and then I was slightly blinded all over again, just momentarily. Then we saw really how big the fireball was. It was the first time I really appreciated what in the world this thing was.
Groueff: It looked like the daytime?
Schreiber: Oh yes. It was very bright.
Groueff: All the sky to the horizon was—?
Schreiber: It is hard to say. It is a white hot object out there and out of the corner of your eye you saw the silhouettes of the mountain and you looked around and could see people lit up but you were so busy watching to see what this really was.
Groueff: So bright light lasted a split of a second?
Schreiber: It lasted for several seconds actually. The first flash, of course, is the brightest one. It is small and very concentrated and very intense light source. Then, as the fireball emerges—
Groueff: What color fireball? Red like fire?
Schreiber: It turns red. You get mostly the impression of a cooling sphere of molten material, which is really what it is. It swirls and then a typical mushroom is formed as the heated air rushes up.
Groueff: What about the noise?
Schreiber: We were 11 miles away so it took nearly a minute for the sound to get there and the BOOM was an anti-climax. It was a boom, but it was sort of the boom we are used to here when we set off high explosives. Compared with the light—
Groueff: The light happened in complete silence?
Schreiber: Sure. There was a loudspeaker which was calling the countdown.
Groueff: Were you lying on the ground with your face down?
Schreiber: No, I think we were sitting on the ground with our backs towards the blast.
Groueff: And then you turned around?
Schreiber: We turned around. Nobody waited for the all clear. As soon as we saw it we all did whatever we wanted to.
Groueff: Was there some fear that maybe you calculated it wrong and the whole stable would go up?
Schreiber: No, I don’t think so. That was a joke that went around that maybe somebody made a mistake and you can ignite nitrogen or something like this. But it was really a joke.
Groueff: You didn’t believe that?
Groueff: So there was no much fear or concern for your personal security?
Schreiber: No, it was mostly—
Groueff: You knew that nothing would happen to the atmosphere?
Schreiber: This is true. There wasn’t any feeling of personal jeopardy at that stage of the game. It was rather a feeling of first, is it going to work at all? Is it going to be a poof and there is all the work down the drain?
When you saw how big it was it was, the first recognition that there really is something which, using the old expression is, “Out of this world.”
Groueff: What did you do when it was over? You jumped in the car?
Schreiber: No, we all milled around and tried to find out what exactly went on, how big it was, did the instrumentation work and there were, I guess, there was an hour or more of let’s say, pretty unorganized running around and congratulating each other.
Groueff: Were you all in a place where Oppenheimer and Bush and Conant were?
Schreiber: No, I don’t know anything about the official reaction of what I will call “the brass.” I was one of the working people down there.
Groueff: It was a different area?
Schreiber: It was in a different area. I think they were actually—I don’t know if Oppenheimer was up at the firing point or not, which was about six miles away. That is all written down. The only people that I really contacted in that level were Bacher. We were traveling in the same car. He immediately was quite concerned. He stopped to think about the real impact of this thing. We had been so busy with the technical details at least at our working level. After I got over the shock and got some breakfast, my next thing was to pack up and get ready for this other trip. I was busy on that and didn’t have much time to philosophize.
Groueff: Where do you come from? Where were you educated? What degree and at which university?
Schreiber: I’m a native of Oregon. I did my undergraduate work there at Linfield College. Master’s degree from the University of Oregon and then I got a fellowship back at Purdue University and got my Doctor of Philosophy in physics there. That’s it.
Groueff: Were you specializing in nuclear physics?
Schreiber: Nuclear physics. I actually did my thesis work on a Van de Graff accelerator and cyclotron bombardment.
Groueff: That was a very new field?
Schreiber: It was relatively new. The cyclotron, it was in 1937 that Fermi got out his series of definitive papers about neutron activations and this sort of started me off on the nuclear physics side of the picture. Fission had been discovered in ’39 and there was great activity in a purely scientific sense.
Groueff: You were all excited about it.
Schreiber: We were all excited about radioactivity, the induced reduction of fission. Not many people there had thought about the possibility of converting this for power or for explosive use. In fact, the activity at the Argonne Laboratory, the MET Lab then, in Chicago was the first thing where we really recognized there was something beyond ordinary scientific curiosity.
I’d say the transition over to that sort of thing was a fairly natural one. It was a fairly strong nuclear physics group there at Purdue. When the war started, they of course all wondered, what we should be doing? A number of people left to go into other areas—radar work, although it was top secret at the time at MIT. Several people went there.
A number of us talked in the defense training programs and took on additional teaching loads because they were then starting to pour in people to get the minimum basic training in physics and electrical engineering and so on to supply the requirements to support the war. This came along. The work on nuclear physics came along just at an opportune time because we were beginning to wonder if we were properly spending our time and that sort of thing. We did have this one little project there, which was in the Office of Scientific Research and Development to start with, which we didn’t know why we were doing this but—
Groueff: At that time you didn’t know?
Schreiber: No, we were cleared but everything was pretty well compartmentalized.
Groueff: You had no idea that some other people were working on the bomb and the separation of uranium?
Schreiber: We didn’t know the ultimate objective of this. We were told that, “This is important. This is something [Hans] Bethe came and talked to us about it and said, we want you to do this and so on”.
Groueff: You didn’t ask many questions?
Schreiber: No, we were told don’t ask any questions. Just take our word for it, it is important to learn this. [L.P.D] King and I were the two in Purdue originally starting this and [Marshall G.] Holloway and Baker came from Cornell University. They both worked with Bethe and [Robert] Bacher there.
Holloway was assigned as project leader for this nation of the cross section of determinant tritium. About midway through that he was called out here. This was in the early spring of ’43. He was then told about what the project was about and when he got back he was authorized to tell us what this generally was about and did we want to go and we accepted.
Groueff: How old were you when you came here?
Groueff: A pretty young team?
Schreiber: Yes. I was older than some were.
Groueff: How old were Baker and King?
Schreiber: They were roughly the same age. There were people like [Richard] Feynmam who was, I think, reasonably young. There were quite a few people—
Groueff: Feynmann was twenty-seven, he told me.
Schreiber: The average age in the laboratory was very low. I think it was well below thirty.
Groueff: And people in very responsible positions.
Schreiber: Oh yes. They got pushed into these positions very rapidly.
Groueff: What is the story of the implosion? From the way I read it in this book, implosion was suggested by [Seth] Neddermeyer at the beginning without success. People didn’t pay much attention and the effort was concentrated on the gun method until you realized that the gun method couldn’t be used with plutonium.
Schreiber: I am not an authority on that. I know that the two techniques were proposed in the so-called Los Alamos Primer. It was the first document, which was subbed into your hands when you got here.
Groueff: What was it called?
Schreiber: The Los Alamos Primer also known as LA-1—the first document ever issued.
Groueff: It was a secret?
Schreiber: It was a secret— I guess at that time it was a top-secret description which stated the purposes of the project. It discussed, in very general terms, the principle of the atomic bomb, the nuclear bomb. We never called it an atomic bomb until the newspapers hit the streets after the war.
It discussed the various methods of assembly. The obvious simple thing to do is make this two parts of a gun and assemble it and maybe this could be expanded by making a cartwheel and firing several in except this would lead to problems with simultaneity and so on.
Groueff: And all of this was discussed in detail in the document?
Schreiber: No. The whole thing was only twelve or fifteen pages long.
Schreiber: Printed, yes.
Groueff: Who wrote it?
Schreiber: I imagine it was a joint affair. I don’t think there were any authors. This is a matter of record and you can find out.
Groueff: Do you think it is declassified now?
Schreiber: I don’t know. You might be able to find out.
Groueff: The first thing a scientist who came here would be given is the classified information and you learned a lot of the details from this document?
Schreiber: You didn’t learn details. You learned the basic objectives of what you were trying to do and something about the approaches which could be taken. The gun type was described there. The multiple gun was described. The concept of implosion was described and it was pointed to as a problem of simultaneity and avoiding jetting.
The general problems were discussed but it did not say that the velocities have to be thus and so or that the requirements, you didn’t know it. This was the object of the whole game was to start exploring these. The two approaches, implosion and gun technique, probably went up and down in favor as you saw successes or problems.
Groueff: What I’m trying to find is whether the implosion was a discovery of one man at one shop event that somebody—
Schreiber: I can’t answer that. I don’t know.
Groueff: Anyhow, it wasn’t applied before. It was known as a principle but I don’t think—
Schreiber: They didn’t know how to do it. This calls for a degree of simultaneity, of smoothness of achieving this, which ordnance practice never worried about. Normally, if a fuse goes off within a tenth of a second of when you want it to, that is just fine. Now, here you are talking about microseconds and fractions of microseconds so a whole new technology had to be developed before you could talk about implosion sensibly.
Groueff: The high-speed camera was one of the tools that were necessary?
Schreiber: This was a diagnostic tool. You want to know how much two detonators differ in their characteristics so you set them up and fire them.
Groueff: It actually defies the imagination. A camera to photograph things which happen in a millionth of a second.
Schreiber: There had been street cameras developed for other things. This was about the time the ultra-high speed centrifuges, which make use of the little air motors, were available, I think the first ones were built around 1932 or 1933 and they were little tiny things.
The principle of a street camera, of sweeping an image, has been known for many, many years. But to combine this with the high speed centrifuge principle or the high speed air rotor principle, and then get your lenses proper, and you only want this to go through one revolution, so you have to have fast shutters. Even if you are going to take 100 pictures during this time, you have to have fast shutters to open and close it. There is a whole sequence of developments that are needed there.
Groueff: I wanted to ask you one thing in the reading of [Rex] Hawkins book, one thing I didn’t understand: what is a target case? He says that the most amazing development was the first case ever to be tried proved to be the best case ever made. This case was used four times in the range and subsequently fitted to the bomb dropped on Hiroshima. Something about the uranium.
Schreiber: Oh, this has to do with the gun. What he is talking about there is the case which contained the reflector, contained the rings of the U-235, which the rest of the–
Groueff: By case you mean the gun?
Schreiber: Yes. You see, your gun is a double-ended device. You have a conventional gun but then at the open end of the muzzle instead of it being open it goes into this chamber and that is the target. I don’t know the details of it, but it was no doubt a very high strength steel, which had to take the shock of this thing coming in.
Groueff: So actually you shoot with your target on the end of the muzzle?
Schreiber: And it stops with enormous shock. You didn’t dare let it go on through because the reaction might not start. That was one of the problems.
Groueff: Why didn’t you use that for plutonium?
Schreiber: You can’t do it fast enough because of the spontaneous fission and the alpha reactions which produce more neutrons. It starts reacting before they get together so it will fizzle and only come up to a very small part.
Groueff: And the uranium 235 allows that?
Schreiber: The uranium 235 does not. There aren’t many neutrons—a few per second let’s say compared to the millions per second of plutonium. You have time on these time scales. The gun assembly is very, very slow. It takes forever. There is time with uranium but not with plutonium.