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In His Own Words
Dr. L. Worth Seagondollar
In His Own Words
Worth Seagondollar gave several invited talks about his experiences at the Manhattan Project, which he joined in the spring of 1944. Portions of a 2007 presentation are excerpted here (edited for length).
On Seagondollar’s role at Los Alamos National Laboratory where he was recruited while still a graduate student at the University of Wisconsin:
The thing that we wanted to calculate was the critical mass of uranium-235 and plutonium-239. Why did we want to calculate this? Richard Feynman put it very nicely. . . . He said, “What happens if we actually get the critical mass together unintentionally? What are we going to lose? We’re going to lose a beaker? We’re going to lose a laboratory room? We’re going to lose the eastern half of New Mexico.” That actually was the knowledge of the situation at that time.
The calculation of the critical mass, if you’re going to really do it precisely, involves the probability of the fission process and other nuclear processes that can occur. . . . I was one of a three-man team that measured the critical mass—or very, very close to the critical mass, 98% of the critical mass—of plutonium-239 . . . I think my importance in the team is well qualified by the hours I had to work. The group leader works from 8:00 a.m. till 4:00 p.m. A more senior graduate student worked from 8:00 p.m. till midnight, and I worked from midnight till 8:00 a.m. And this kind of defines where you are in this organization. . . .
We had two of these big, long counters. . . . In between them, we had a place where we could put a neutron source . . . It was a source made up of various radioactive materials which gave off neutrons for approximately the energy that comes out from the plutonium fission reaction. We had put this source in the middle and we had these two big detectors here, and we had measured the number of neutrons coming out per second from that source. . . .
We finally ended up with two hemispherical shells which fit around this one-inch-diameter source. The first one was an eighth of an inch thick.
What we wanted to do with these neutron counters was measure the number of neutrons per second that came out with these two shells around. If you were getting a significant number of fission processes, then you would get a larger number of neutrons coming out. We were measuring what we called the multiplication ratio. The multiplication ratio with an eighth of an inch–thick shell of plutonium was 1.0, as far as we could tell. There just wasn’t enough fissions occurring in that eighth of an inch to be significant. . . .
We made this measurement with a multiplication ratio of 1.0. . . . We’d repeat the measurement [with thicker shells], and we got a multiplication of 1.1 . . . This procedure was duplicated over and over and over again. The final measurement we did with a chunk of plutonium which fit around this one-inch-diameter core, which is about this big, about the size of a softball. We were making plots of the multiplication ratio as the radius of the shell. We got up to a multiplication ratio of 18. . . .
Our laboratory had been duplicated in a deep canyon nearby. The idea was that our laboratory was up on the main plateau of the town of Los Alamos. If there was a nuclear explosion, the town would go. So the 100% measurement was made down inside this deep canyon where they had duplicated our equipment.
When we finished that factor of 18 experiment, I was temporarily out of work . . . I had come back from lunch and one of my friends said, “Fermi wants you to call him.” Fermi was known as the Pope at Los Alamos. I remember making the remark, “I presume God is after me too.” “No, the man wants you to call him.” So I called him and he asked me to come up to his office. The point was, he wanted some more detailed information about the fission experiments we had done. The other two guys were already down at a place in southern New Mexico where the first nuclear explosion was to occur. I was the best he could get a hold of. I still remember going into that office. I was absolutely terrified. I realized after about five minutes that he was asking me questions that any beginning nuclear physics student could answer. He was doing it to put me at ease. I had a high opinion of Fermi before that, and at that phase it just skyrocketed.
We were still talking when suddenly at the doorway was Louis [Slotin]. He was the man who was in charge of the 100% measurement. He didn’t say a word. He went over to the blackboard and wrote a number, six-point and two other digits at the end of it. There wasn’t a question what he was talking about. This was the mass of plutonium-239 in a spherical geometry; that was 100% critical mass. Unfortunately, several months later, repeating this experiment, he was killed.
On working under high security:
When you do experiments like this, you have a guard watching you. Sometimes it’s a civilian, sometimes it’s a man in military dress. You can tell these people always if you know what to look for. What to look for is a .38 revolver in their hand. They don’t have a holster. Their job is to make sure that that plutonium stays where it’s supposed to be. They don’t care what happens to you, but that plutonium, they keep their eye on it.
The first one I ran into was the first day that we started doing this experiment. I walked over to the equipment. I was the first person there in the morning. There was this deep voice behind me, “Will you please stand still.” I don’t know what your reaction is, but I turned around to look, and there’s this guy with a big, funnel-shaped .38 pointing at me. He wasn’t joking one bit. That was my first introduction to one of the security guards there.
On dropping plutonium:
I had the midnight till 8 a.m. shift. Basically what you had were these two hemispheres [of plutonium] . . . with a one-inch spherical hole in the middle for the [neutron] source in there. I do not know what happened, but I bumped it and knocked it over. One piece fell about six inches onto a steel table, and the other piece I caught like this. I don’t know what you do when you are really scared, and I mean really scared. I want to throw up. The piece I caught was not damaged in the slightest. The piece that fell over onto the steel table had a dent in the side, and the two pieces would not go back together. You couldn’t continue the experiment. This was coated with, I think, silver. The question was, with this dent, had the silver been broken? Because if it was, I was in severe danger because the stuff would oxidize and go into the air. We had an ionization chamber there for this kind of purpose. I checked very quickly. . . .
Looking back, what I did, I’m not sure if it was the most intelligent thing in the world. But at Wisconsin when you had problems, you were told to solve them yourself. So I went and told the guard to stay there, which he obviously was going to do. And I went to the big maintenance building next door, to which we had a key for emergencies. I got a gas mask and a new ball peen hammer. I went back to the ball, put the gas mask on, put the guard out in the hall, and gently tapped this thing. I took my time with it, until it was back into a shape where it would fit back together, and went ahead with the experiment. I told Al Hanson, who was the number one man—he was the 8 a.m. to 4 p.m. guy—what had happened. I don’t remember him making any derogatory comments about it. I went home and went to bed.
The next night there I was midnight till 8 a.m., about 2:30 in walks Oppenheimer. He introduced himself, and that wasn’t necessary. . . . I had a very uncomfortable feeling he had heard my name and the reason why. After talking for a bit in a very polite manner, he said, and I can remember the words, “We are all exceedingly fortunate that you were so successful.” And he left, and that was it. That’s one of the two times at Los Alamos that I really, seriously thought about the possibility of death, though I didn’t know it.
On watching the first atomic bomb test at the Trinity Site:
[Colonel Stafford Warren] strongly recommended that you have some kind of eye protection. We thought of this, and brought back a whole case of welder’s goggles of the type that were used for acetylene torch welding.
That afternoon, I’d seen that there was a welding shop there. I went over and I traded the whole case of goggles for five pieces of blue glass that they put in an electric arc welder’s hood. We got some 18-inch square pieces of cardboard and cut a little rectangle in them and scotch taped this blue glass over it. This is what we were going to look through. I tried it out that night on a 100-Watt bare light bulb that was there, and all I could see was the blue glow where the filament was, nothing else. It was really dark.
The morning [of the test]. . . I’m looking in the opposite direction and he’s counting down—seven, six, five, four. When he gets down to zero, I’m looking in the opposite direction. The amount of light that I saw there was the most intense light I have ever seen in my life, and I hope to God I never see another thing like that. There were mountains in the distance, and they actually seemed to mechanically jump forward. Like looking into a photographer’s light bulb, except this is absolutely everywhere. I counted 1001, 1002, to 1015 and turned around and looked, and my first reaction was, “You forgot the blue glass.” But I hadn’t. I was looking through it, and what I was seeing out there was a ball of fire. When I saw it, it was about a [foot] diameter above the valley floor, and it simply went up through the clouds. I do not know how long we watched that thing. I know it was full daylight before we gave up watching it.
This is what I saw down there on this first explosion. I sincerely hope I never see anything similar to it again.
On the use of the atomic bomb during the war:
I’ve often been asked, “Do you regret your participation in this?” Well, first of all, I was a rather low man on the totem pole. But on the other hand, I was involved. It’s not pleasant to think that you . . . were involved in the killing of 100,000 people—men, women, and children. On the other hand, the United States and its Allies were ready to invade Japan . . . I have no regrets for my participation. People would come up to me and say that they strongly agree. They were on one of the ships that were ready to go into Japan. As I recall, Churchill made a statement that if the Allies had invaded Japan, there probably would have been 250,000 deaths of Allied troops, and over a million deaths of Japanese people, defenders and civilians. So from that point of view, maybe we saved some Japanese lives in cutting off the war when we did. That’s my position on it.
I was made particularly uncomfortable one time when I gave this talk. . . .
Afterwards, I see a man that I know is a Japanese professor in the mathematics department coming up to me. I was a little uncomfortable. When he got up to me, he rapped his leg with a cane, and it was obviously a wooden leg. He said, “I got this at Hiroshima.” He said, “I agree with your feelings about you’ve probably saved more Japanese lives than you’ve taken.” It was a real feeling of relief.
To read the full transcript of Dr. Seagondollar’s talk.