A Reluctant Division Leader
Robert R. Wilson, P-Division Leader (1944-1945)
No! No! I won’t do it!” I shouted at Oppenheimer, who had
just offered me the job of heading the new Research (R) Division at
The year was 1944, and the Laboratory was being reorganized because
of the discovery of the high rate of spontaneous fission in plutonium.
Bob Bacher headed the old Experimental Physics Division, which had been
split into two new divisions in August of that year. One part became
Gadget (G) Division, which was to develop a plutonium bomb based on
Seth Neddermyer’s implosion ideas. The other part became R Division,
which would consist of the remaining four groups from the Experimental
Physics Division: the Cyclotron Group (R-1), headed by me; the Electrostatic
Group (R-2), headed by John Williams; the D-D (Deuterium-Deuterium)
Group (R-3), headed by John Manley; and the Radioactivity Group (R-4),
headed by Emilo Segré.
“Look, Oppie. Just pick one of the other three Group Leaders.
They’re all much more senior than I am, and each would hate working
for a young fella like me,” I explained.
“Not as easy as you think,” responded Oppie. “I have
already tried to pick, in turn, each one of them, but in each case,
the other two threatened to quit. So you, Bob, are elected, faute de
“No, not me! I did not come here to be an administrator. Why
don’t you just bite-the-bullet, chose one, and let the chips fall
where they may,” I responded.
“I thought I had done just that in selecting you,” Oppie
“Well, bite a different bullet then, because I came here to do
physics and not to become and administrator,” I replied, looking
him straight in the eye at the implied criticism of him.
“Maybe we ought to think about it,” Oppie sighed as he
ambled away as only Oppie could in his crazy, but characteristic, gait.
The next day, Enrico Fermi asked me to accompany him on a walk. He
had been sent by Oppie to talk me into the R-Division job.
“You’re a fine friend,” I said after hearing him out,
“for I have been following your example in turning it down. You
would never do that sort of thing.”
Fermi’s eyes sparkled. “It’s something you have to
earn, and you’re not Fermi yet!”
He then went on to instruct me on how to avoid administrative duties.
Essentially, it came down to just saying no.
“Yeah, but how about all the technical work of the other groups.
Wouldn’t I need to know about it in detail?” I asked.
I was, up to this point, doing a pretty good job of saying no to Fermi
when suddenly he volunteered to help me with the technical work. I was
astounded. I could hardly believe my ears. The idea of working with
Fermi made it a whole new ball game. I had worked with him on the reactor
project at Columbia University, so I knew what a valuable experience
working and learning from Fermi could be—never mind all the delightful
fun of just being with him.
Fermi promised that he would be available whenever a problem came up.
To clinch our bargain, we agreed to meet together every Friday after
lunch to discuss the physics being done in the Division and also the
physics that should be done. I was ready at that point to sell my soul
for this chance, but I still had a few conditions for Oppenheimer. One
was that I could continue as Group Leader of the Cyclotron Group; another
was that I not have a special office with a secretary. Finally, I insisted
that each of the other Group Leaders ask me personally to take the job.
Sure, I sold out—but then everyone has his price, and mine was
a few moments each week with Fermi.
In any event, my life was little changed except for the delightful
weekly meetings with Fermi. Usually in our discussions, a student-teacher
relationship prevailed in which Fermi clarified the physics by simplifying
it to a level I could understand—he was a master at that. Nor
was it that I was completely unintelligent, for perhaps I knew more
about accelerators and particle detectors than he did. We made a pretty
As Division Head, I gave the Group Leaders essentially free reign.
Happily, I had never heard about people staying in channels because
Oppie would usually go directly to the person concerned. On the other
hand, I would get several calls every week from him about the practicality
of experiments being considered for our Division, as well as an ordering
of the priorities for the whole project. I always had the feeling of
knowing too much rather than too little about what was going on at Los
One of my duties as a Division Head was to attend the weekly meetings
of the Administrative Board. We usually considered serious matters involving
the project. But on the light side, I recall that Joe Kennedy and I
had dedicated ourselves to making the life of the G-2 army security
officer miserable. We would hit him both coming and going. His security
measures either grossly interfered with the work of the project, or
they seemed to us to be totally inadequate.
Once, I remember Kennedy giving this particular officer a hard time
about not providing enough surveillance. The officer remarked, “Joe,
how do you know that the little kid who followed you over here was not
one of my agents?”
Kennedy looked at him coldly for a few moments and responded, “Yeah,
if he’s your agent, he’s your best agent.”
Actually, the meetings were exciting for we were kept abreast of all
sorts of important information about the project, such as when and how
much 235U and plutonium would be made available to us.
Sometime in March 1945, the nature of R Division changed dramatically.
We were given, in addition to what we were then doing, the responsibility
for measuring the nuclear phenomena resulting from the test explosion
of the first atomic bomb. This test was to be made in the Jornado del
Muerto desert near Soccoro, New Mexico. Philip Moon of the British Mission
had already done some preliminary design and construction. But time
was running short and not much was getting done, so Oppie asked us to
reconsider the whole problem about what experiments should be conducted
for the Trinity Test. We pitched in with gusto to do what could be done
in the three or four months remaining before the expected time of the
Fermi was particularly interested in this phase of the project. He
and I used our regular discussions as one way of satisfying his interest.
Of course, he had many other channels open to him, and I am sure he
used them too.
As I recall, the members of our Division decided who would do what,
not by general meetings, but by meetings between me and the individual
Group Leaders. My procedure was simply to inform them of what had to
be done and to ask them what they wanted to do. After they had discussions
within their groups, they came back to me with a list of who would do
what. I suppose there was a bit of pushing and pulling, but somehow
we easily came up with plans that covered all the measurements that
needed to be done, and then we made the equipment and installed it in
the desert. Writing this now, it sounds authoritarian and perhaps it
was. But I think not, for we were such a small Division (perhaps about
40 physicists) that we all interacted frequently enough so that no formality
was necessary—or so I thought.
My continued meetings with Fermi were pure pleasure—well, with
one exception. My usual function seemed to be to bring up problems that,
to my great satisfaction and admiration, Fermi elegantly solved without
much participation on my part. Only occasionally, would I argue with
Fermi’s physics, and then with great trepidation—he was
just terribly good. I did learn a lot because he worked out what he
was doing in a very clear manner that I could easily follow. Yet being
human, I wanted to participate more in the physics process.
I do remember once, though, when, to my great satisfaction, I caught
him in an egregious error. Then without remorse, I made him suffer for
being right so much of the time. This joyous occasion occurred when
I had invented a device for measuring the rate of increase of neutrons
(the e-folding time) during the explosion of the bomb. An electron-multiplier
tube was to be used to measure the radiation as it emerged from the
detonation of the bomb. Fermi thought about this for a few seconds,
went through his calculations, and then informed me that it would not
“Too slow,” he said with his usual confidence, “by
a factor of hundreds compared with the 10-8 second resolution you expect.”
I informed him that that must be wrong. Again Fermi went through his
calculations, this time out loud and slowly for my benefit. “My
dear Enrico, you are losing your grip. Perhaps its too elementary,”
I said with an assurance that worried Fermi slightly. He made more calculations,
this time on a piece of paper, again with the wrong result. He had made
an error that I knew he was not likely to find. That put me for once
in the “catbird seat.”
Fermi’s error was due to our custom at Los Alamos of finding
a particle’s speed at some energy by simply scaling up that of
a thermal neutron. Fermi had been doing this automatically over the
past years, and he was not likely to break out of this ingrained habit.
I let him wallow in his misconception while I privately delighted at
his discomfort. Eventually, I asked him, to his embarrassment, if he
had ever heard that electrons were 1,800 times less massive than neutrons.
We tended at first to be somewhat casual about the Trinity Test. One
day, John Dewire and I were discussing possible electrical pick-up signals
in the various detectors being built. We knew that the next day there
would be a test explosion of 100 tons of TNT at the site of the future
test. We asked ourselves whether or not we could find out anything from
the explosion. Well, no, we decided. But just seeing it might be a valuable
experience for us—or at least some fun. So on a whim, we called
Oppie’s office to tell the guards at Trinity site that we were
on our way. Then we put a portable electrical generator, a long coil
of electric cable, and an oscilloscope into a pick-up truck; stopped
to tell our wives (we did not have telephones in our private homes);
and headed for Trinity Site some 200 miles to the south. It was dark
when we got there, and we had to talk our way into the site past the
guards. We were able to spend the night in the crude barracks at the
base camp. The next morning, we drove over to where about a dozen people
were stacking a huge pile of boxes of TNT. We joined in and helped stack
boxes for awhile—strangely, no one else seemed worried about dropping
a box because, I gathered, a detonator was required to start an explosion.
But I was worried!
Soon, I had an idea for our experiment—simply to put the shorted
end of our cable deep into the pile and then run the cable several hundred
feet away from the pile to our oscilloscope and gasoline-powered generator.
Not much of an experiment, I must say, but it was better than stacking
boxes of TNT! Of course we expected no signal. That night, we found
the explosion impressive. It even had a quality of beauty. The next
morning, we developed the photograph, which had automatically been made
of the scope trace. To our surprise, there were huge signals. We had
to understand the source of those signals, how much worse they would
be in the ambiance of an exploding atomic bomb a hundred times more
powerful, and how we should shield against them. This unexpected finding
was a good example of the value of laziness and fear.
Back at Los Alamos, significantly large amounts of separated 235U began
to arrive from Tennessee. One experiment that I can recall was to measure
the multiplication of neutrons in a sphere of this material about 1
in. in diameter. Oppie insisted that the material be guarded all the
time. For some reason, Fermi’s personal guard, John Baudino, was
assigned to us. In fact, there were two identical spheres, one of 235U
and the other of normal uranium. We were to make a comparison of the
two. I liked to amuse myself by switching the spheres around rapidly
and then asking Baudino which sphere was the one he was guarding. He
would confess that he did not know and would ask which one should he
be guarding. I could tell because the 235U was warmer because of its
We wanted the measurements to go on all night, but we had to stop
so that Baudino could sleep. I had the idea that were I to be issued
a pistol, then I could do all the guarding myself—after all, I
came from Wyoming where every red-blooded boy learned to shoot before
he could walk. Oppie agreed and asked security to issue a pistol to
me. My friend, Pier de Silva, agreed to do so, but he reasonably insisted
that I be checked out first on whether in fact I could safely use a
pistol. This he did by taking me to the firing range, pulling out a
.38 Colt police revolver, and giving me a lecture on its use.
“This little lever is the trigger. These little gadgets are cartridges
and should be put in these holes that spin around here. You line up
the front of the gun with this v-shaped hickey in back and with what
you are shooting at. Here, I’ll show you,” de Silva said.
With that, he carefully fired six shots at a target.
“Now you do it,” he said, loading the gun. I had learned
in Wyoming to “roll” a pistol in order to get a lot of shots
off accurately and rapidly. That’s just what I did. Most of my
shots were closer to the bull’s eye than were his.
None of this fazed de Silva in the slightest. He repeated his earlier
lecture in its entirety, together with his demonstration. He finally
wrote out a beginner’s certification and issued the revolver to
me for the duration of the experiment. He had put on a terrific show;
not once did he crack a smile!
I took full advantage of the pistol to impress my friends with what
a macho type I was. I carried it, ostentatiously tucked into my belt,
everywhere in the technical area and spent no little time at all explaining
to the military police why I had the gun; eventually I had to show them
de Silva’s authorization. When the experiment was completed a
week or so later, I was most reluctant to give it back. I am proud to
this day that the uranium spheres had not been stolen on my watch!
I became involved in a dispute with G Division that did not end well.
As more and more 235U and plutonium was delivered to us toward the end
of 1944, measurements of assemblies close to criticality were started
by the Critical Assemblies Group of G Division. At first, these measurements
involved small cubes of uranium hydrides (such as UH10), which were
stacked up into larger cubes until criticality was approached. Later,
less hydrogen was used, and the procedure became more serious—more
dangerous. The Critical Assemblies Group decided not to have the elaborate
safety devices that were used, for example, with cyclotrons. Instead,
they decided to depend on their wits alone. These physicists were the
best and the brightest of the project. So although I did not like their
arguments, I could see that there were good reasons for going ahead
as they had decided. For instance, each assembly might be quite different.
After expressing my views forcibly, I subsided. After all, they were
not in my Division, and indeed it was none of my business—well,
in a fashion.
A few months later, I became more involved because they wanted to use
the fast modulation of the cyclotron (neutron pulses of less than a
tenth of a microsecond), which was okay of course. I was the crew member
whose turn it was to help the single physicist who showed up. His equipment
consisted of a small wooden table, a single neutron counter, and boxes
containing the small cubes of enriched uranium hydride. I was impressed
by the simplicity of the equipment, as advertised, “So simple
nothing could go wrong.” Not quite. The physicist began stacking
the uranium cubes as I stood next to him and watched with considerable
interest. It was my first experience with a prompt neutron reactor approaching
criticality, and I was thrilled in expectation.
After a while, as the stack got quite large, I asked why the neutron
counter was not counting. I was assured that this was regular and that
it would not start counting until we were closer to the critical point.
Uncomfortably, I gave the neutron counter a hard going over and asked
if the signal light on the high-voltage supply was operative or it if
was burned out—as was often the case. The voltage was indeed turned
off, so the neutron counter was not working. When the voltage was turned
on, the counter to my horror started blazing away. A few more cubes,
and the stack would have exceeded criticality and could well have become
I was outraged. This incident was my closest brush with death. The
reason given was that a wooden table instead of a metal table was being
used for the first time, so thermal neutrons were reducing the critical
point. After chewing out the physicist for his carelessness, I went
to his Group Leader. Not satisfied, I complained to the Division Leader.
Still not satisfied, I flew into a fit of anger over the incident with
Oppenheimer. At the time, we were all hysterically busy. I was due back
at Trinity the next day. And I went there. Of course, I should have
stayed at Los Alamos to pursue the incident further—for if I had,
I might have saved the lives of two people. To this day, the incident
is on my conscience.
The Trinity Test was soon upon us. R Division had occupied the North
Bunker at 10,000 yards from the bomb locality and had acquitted themselves
well, not that any credit was due to me, but I still take great pride
in them—however, Trinity is a separate story.
Once we had seen the explosion in all its grandeur and implied horror,
we did not need any of our measurements to know it was a success—they
would have been more meaningful had it failed. I exulted with my colleagues
in the gratification we felt in a job that had taken five long years
of dedicated hard work. It was an epiphany for all of us. For what had
been theoretical before had now become all too real—but in a different
way for each one of us.
For me, the project was over. I could hardly wait for John Manley to
take over the Division and to reorganize it into the Physics Division
that now bears little resemblance to the tiny group we were then.
Do I regret my fall from grace—from being a pure physicist to
becoming an administrator of sorts? No. If Paris were worth a mass as
Henry IV had said, then surely Fermi was worth my fall from grace.
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