HA: Well, at the end of the War, in nineteen, I guess it was early '46, I decided to go back to school and finish my education and I was fortunate in that Fermi, I had worked with Fermi early on at the very beginning of the project in Chicago and at Columbia and he agreed that I should come back to University of Chicago. He arranged for me to get a fellowship and so in what was early '46 I returned to the University of Chicagand stayed there and got my doctorate and left there in '49 and caback to Los Alamos.

HA: (Interrupts) In '49, I came back and worked in a group under a man named Toshak, working on a machine called a Vandergraph, which is a type of an accelerator and we were measuring cross-sections of various elements and we did the first work in accelerating tritium to measure the so-called DT cross-section at relatively high energies, which was important in the development subsequently of what's called the hydrogen bomb.

HA: Oh, I think the people that I associated with primarily felt it was a very serious responsibility and at that time, we had very few bombs, including the military wanted as many bombs as they could have at the highest yields possible. And so there was a great deal of work going on trying to match the quantities of plutonium and uranium, enriched uranium, to maximize the number of bombs to maximum yields that the military wanted and of course, at that time the military had an insatiable desire for numbers of bombs, because they had an infinite number of targets essentially and a very large number of airplanes and at that time it was strictly bombs and then subsequently we got involved in the missile business because of the so-called missile gap or whatever turned out not to be true subsequently.

HA: Well, you know in the '45 period, after Nagasaki, we didn't have another bomb till about a month later and it built up very gradually. But we were in the tens, essentially until '47, '48 period and then it got to be, I guess, in the fifties or the hundreds. I don't recall the exact numbers, [clears throat] but it was, compared with today, it was a relatively small number and they were very crude type of devices which essentially had to be assembled by hand in those early days. So the so-called response time was very long, but at that time there were no missiles, so there was no need for a rapid response. With the advent of Sputnik clearly the time required to deliver bombs was shortened and that's when, of course, subsequently in late, I guess it was in the early fifties, we started the quick reaction alert in Europe, moved things first to England, with the B47 squadron just because of the time required to get bombs on target was greatly shortened with what we thought was going to happen as a result of Sputnik.

HA: I don't think there was any additional pressure. The pressure right in the early fifties was the development of the hydrogen bomb. There had been a great deal of controversy at some levels, never among the workers at Los Alamos or those involved in the program that we should go full speed ahead. But there had been a little bit of a hiatus before we really went full time, when Truman finally made the decision that we should develop the hydrogen bomb as soon as possible. we went on a six day work week at Los Alamos, which was really six and a half, because people usually came in on Sundays anyway, and there was a tremendous urgency then to develop that particular type of device.

HA: I don't know why we had such an urgency then to develop it, probably because when it was realized it could be done, it was clearly obvious that if we could do it, the Soviet Union could do it too and it really made quite a difference in the so-called deterrent posture, because whereas we had been limited... well we did have one particular device carried by a bomber that was a half a megaton, but to be able to do many megatons compared with kilotons was just quite different. Being able to put hundreds of kilotons or more on a missile compared with the big... at the time our regular bombs were maybe five thousand pound, ten thousand pounds, which is out of the question for any of the missile technology that was available then. So there was real military requirement as well as, you might call it, an intellectual challenge to try to develop these much higher yield weapons. Now whether they were really needed in the sense of war fighting or devastation, isn't clear, but it was clearly needed in order to make high yield small devices, small in the context they could be easily carried either by fighter aircraft or by missiles.

HA: There was a little bit in late '49, early '50 at Los Alamos, but it was pretty much... The people who were against it, were very closely allied with Oppenheimer, they had worked with him and they were very close to Oppie and Oppie, of course, had left Los Alamos, so I don't know personally what his opinion was, but from what one reads, he was not very much in favor of it and his, let me call, colleagues or disciples - and they were very few, maybe five, that's all - but they were high in the hierarchy of the laboratory at the time they were pretty much of Oppie's opinion. Whereas the rest of us - most of us being much younger - were gung-ho for the development and sometimes the arguments got rather bitter, rather personal. eventually Truman made the decision and that was that, there was no more argument and actually couple of the people who opposed it actually left the laboratory and went into academe.

HA: The difference between hydrogen bombs and fission bombs, primarily rests in that there is a finite size in yield that you can get with a fission bomb, because you start with fissionable material and once you have a critical mass that's pretty much determines the yield. Whereas in the term of a hydrogen bomb, you start with a fission bomb, which is called a trigger, but then you add on to that some thermo-nuclear fuel and if you want to add more weight, fuel being not fissionable by itself, it can be as large as you want, depending on how much you want to carry. Now, actually the Soviets have built the largest hydrogen bomb ever and they also detonated in the air, which impressed me. In fact, their first deliverable hydrogen bomb was the very first, although we may have conducted experiments, the Mike Experiment which showed that you could do this, it was a monster that, I don't know how many, eighty tons or something like that, there's no way you could ever deliver it, but the first deliverable hydrogen bomb was developed by the Soviet Union.

HA: Well, when we went out to Mike, I forget, was it in '52? I can't remember the year, it was a monstrous thing, it was a liquid device, liquid deuterium, all the cryogenics involved. I was involved with a group of people, Frank Dunn, John Mosely, Bob Potter and we had the job of putting tritium in the device. At the stage we didn't know the work, so anything that we could do to help the yield and I remember one particular incident was for us very frightening. We were putting this tritium into the device and we were going to do a dry run the night before. We decided we would use deuterium, which was a hydrogen isotope and the device was warm, it had not been cooled down, it was to be a cryogenic device, liquid deuterium which of course is very low temperature and it was warm, but we were just testing for leaks. We put in the required amount of deuterium and looked at our gauges and very slowly the gauges started to go down, which initially meant to us we had a leak. Well, since what we were filling was way inside the device,there's no way we could fix the leak and there was real panic. And then one of the individuals said, well, maybe what's happening is the deuterium is hydrising, reacting with the warm uranium and that probably won't hurt anything, but in order to check that, let's use an inert gas, such as argon. So then we pumped the system down again, the vacuum looked good, put in argon and lo and behold, we did not have a leak. And then subsequently, the next morning, we put in our tritium. The thing that impressed me... I'd seen lots of fission bombs go off, but the thing that impressed me about the hydrogen bomb - I know Phil Morrison has spoken about the Trinity Shot and the thing that impressed him was the heat, well I told Phil, you don't know what heat is until you've seen the heat from a ten megaton, fifteen megaton hydrogen bomb. The most impressive thing about the heat is it doesn't stop, it just gets hotter and hotter and you start to really worry even thought you're twenty some miles away what's happening. Another phenomena is the cloud goes up so high, that you feel it's on top of you. I don't know whether you ever watched con trails from airplanes, but you swear they're overhead, but they're not overhead, they're quite a ways off, but you have the feeling that the cloud is on top of you and this heat just doesn't turn off. It's very frightening and, of course, the whole island disappeared too, which was subsequently very impressive and the whole lagoon was just sort of a milky white. And then we were asked to go collect samples, so we got in a little motor boat with buckets and went charging into the crater, scooping up the radioactive material and taking it back for the chemists to analyze so we could determine the yield. But we were young and it was a lot of fun.