THE LAWRENCE YEARS -I-
(Photo From Ernest Orlando Lawrence Berkeley
Posing with the newly completed
60-inch cyclotron in the Crocker Laboratory are (left to right) Donald
Cooksey, D. Corson, Ernest O. Lawrence, R. Thornton, J. Backus and W.
Salisbury and (on top) L. Alvarez and E. McMillan
I will always remember vividly my first real meeting
with Ernest O. Lawrence. I had met him casually at a physics seminar
several years before, but carried essentially zero impression from that
Professor Porter of the Berkeley U.C.
Chemistry Department arranged our real meeting. I
was trying to get back into the University where I felt my real future
lay. My position as Job Analyst for the Department of Labor had ended
suddenly and, since
I had been working evenings on ultrasonic effects in
chemistry with Professor Porter, I naturally suggested to him that I would
like to continue on an enlarged basis. This seemed natural because we had
published together and were having some success.
Porter explained sadly, I thought, that he had no
possible source of funds to support me because of the great depression. He
suggested, however, that I might find a place with Professor E. O.
Lawrence in Physics, as he seemed to be the only one in the university
supporting a large laboratory. Porter asked if I knew Lawrence, and I
replied that I had casually met him once and I was sure he would not
recognize me. Porter said, "All right I'll make a date for you and
leave it up to you."
The date to see Lawrence in his office was for 9:00
A.M. Saturday morning, March (
? ) 1937. I had heard of Lawrence's Cyclotron Atom
Smasher, as it was frequently referred to in the daily news. I, therefore,
thought it desirable to see his lab. I
state of some excitement that I presented myself at
Lawrence's office at the appointed time on Saturday morning.
His secretary announced me and Lawrence came rapidly
from his inner office to greet me! "So you're Salisbury," he
said, "Professor Porter tells me you want a job! "Well, in the
first place, I have no jobs for anybody and in the second place you are
the last man on earth that I would hire if I had a
job.* I have heard of your reputation around the
I replied, "Well, since that is
settled, would you be willing to talk for a few minutes
about your Cyclotron?"
"Well, yes," he said, "come in. Have you
looked around the lab?"
"Yes," I replied.
"What is your impression, what would you do to
improve it?" "The main thing wrong," I said, "
i s the resonating inductance for the 'Dee'," I
"How could that be improved and what results could
"You are using all your radio frequency energy
heating cooling water for a small-tubing inductance. The best inductance
would be a large coaxial line, but any way to make the inductance
conductors larger and of lower resistance would increase your 'Dee'
voltage with the same power input you now have."
"We made a model
of a coaxial
inductance, but it did not increase the 'Q' (resonance factor) of the
system as we expected. Did you see the model?"
"Yes, I saw the model, but it was all wrong.
Whoever made it
could not calculate the 'Q' of the resonant frequency
correctly and so the design of the model which I saw is a failure."
"Can you calculate the 'Q' and the resonance
"Yes," I replied, " I can, and I can
'Dee' voltage without requiring
any increase in power. It is true is it not that your beam of accelerated
ions increases in current very rapidly with increasing 'Dee'
"Yes, we can only get 40 kilovolts on the 'Dees'
with 100 kilowatts input. Some very good people have
worked hard on this. We need 50 kilovolts. Can you really increase that
"Yes," I said, "I can."
Lawrence said, "I've changed my mind. Come to work
Monday and I'll give you a two week trial at $100 per month."
So that Monday I appeared at 8:00 A.M.
at the Lawrence
Laboratory to begin one of the most exciting and
rewarding experiences of my life.
When I returned home from my interview I was pale and
shaking. Elma said, "What's wrong? You look like a ghost."
"I got the job," I stuttered.
"Then what's wrong?"
"Don't you see, this is what I've always wanted,
and now I have to produce among the best scientific colleagues in the
world. There is no possible excuse for failure!"
During the next three weeks I worked at learning to run
the 37" cyclotron as a crew member and designing a crystal controlled
amplifier to drive the main cyclotron oscillator. At that time Lawrence
believed that frequency stability would improve the radio frequency driver
for the cyclotron accelerating electrodes. ('Dees') Also, I worked on
vacuum tube flip-flop circuits for
particle counters. I believe I was being tested for
compatibility with the graduate students and post-doctoral fellows who
made up Lawrence's prestigious group of nuclear physics researchers. I
must have passed that test, because at the end of my trial period all I
heard was a suggestion from Lawrence that I should move from San Francisco
to Berkeley so as to be near the lab, so I could put in more hours.
After about five or six weeks I received word from
"Buddie" Toles, for whom I had built a broadcast transmitter
then operating in Roseburg, Oregon, that he had an engineering job there
for me. The pay was to be more than double the pay in Lawrence's lab. I
used this as an excuse to ask Lawrence if I really had a place in the lab.
His reply (was) that I could be there as long as I lived was a bit
startling, since I had not yet been allowed to make any of the changes I
My wife, Elma, and I agreed that my future would be
-page 7 -
better in a lab
in the University, in spite of
the pay, so I turned down the offer to be a radio-engineer-operator in
I kept telling Lawrence that the high resonance factor (
--) necessary for his ' Dee' accelerator electrodes
would vary its frequency with temperature and ion load so that a
crystal controlled driver would not synchronize with
the 'Dee' system or help to produce more accelerating voltage. I proposed
that changing the resonant inductance of the system to one of less
resistance would increase the 'Q' of the system and thus give more
accelerating voltage for the same 100 kilowatt oscillator input then in
use. Lawrence replied that if I could get the 'Dee' voltage up from 40 KV
to 50 KV it would be a miracle as he had tried the suggestion of the best
engineers, including Charley Litton, at great expense with no appreciable
I insisted that the suggestions tested were incorrect. I
said, "If you will let me change the system my
way, I will get 100 KV on the 'Dee's' without any increase in power."
Lawrence replied that I must be crazy as no such thing
However, I kept persisting and finally at the end of a
period of thesis work Lawrence finally said, "All right, if you can
persuade any of the Doctorate crew to approve and help you, you can have
one week of cyclotron shutdown to make your changes."
I already had Dr. John Livingood on my side so we were
allowed to proceed.
We worked, starting early Sunday morning, 16 to 18
hours per day through to the next Sunday. We had not only to replace the
small coil of 1/4" tubing of the original inductance with 3"
copper pipe with water cooling tubing soldered on to it, but
also to build a copper shielding house and a turning vane with mechanical
control from the control table. The 3" tubing had to be supported
because the glass insulators and seals supporting the
'Dee's' and sealing the vacuum of the acceleration chambers were not
considered strong enough to hold the weight of the new single turn of heavy
tubing which formed the new inductance of the resonant 'Dee' circuit.
We also had to bring on the oscillator power slowly and
calibrate the 'Dee' voltage with a capacitance multiplier against a
General Radio radio frequency voltmeter.
When all this was done we came up to full power with
the ion source on, since we correctly believed that this would now be an
appreciable part of the electrical resistance load determining the 'Q' of
the system and hence the 'Dee' voltage.
We were elated to find that under full ion load we had
110 KV on the 'Dee's' at the same power that previously produced 40 KV and
that the external deflected beam of 8 Mev
deturiums to the target was
now 150 M
amperes, rather than the 8 m amperes
To say that Lawrence and all of the lab members were
elated is a mild expression of the celebration that followed.
About Wednesday after this event, Lawrence asked me to
come to his office and there he told me he was making me Crew Chief for
all the cyclotron operating crews and he expected me to be present at at
least two of the three daily operating crews necessary for the
round-the-clock operation that Lawrence insisted on. Maximum results were
expected and we were soon producing and discovering a new radio-active
isotope essentially each day.
Soon after this Lawrence asked me to see what I could
do to improve the system of heating the ion source filament. A heavy
filament was needed to produce electrons for ionizing the deturium in the
center of the cyclotron where the particle beam originated. This was
because this filament operating in a plasma of Deuturium ions was rapidly
eroded away. Such a heavy filament of tungsten
will require a large current to heat it to emission
temperature (40 to 100 amperes). The magnetic forces in a 15 Kilogauss
field produced troublesome forces. D.C. current could not be used because
a tungsten will at emission temperature has about the same
strength as a lead
wire of the same
size has at
When 60 cycle current was tried
the filament was rapidly vibrated to destruction. So, Dr. Van
Voorhies had constructed a heating current supply
out of audio amplifiers and transformers operating at 15
kilocycles/sec. This allowed the filament to last for
one to two days of operation
between replacements. I calculated that a filament
could last as long mechanically
as it would based on arc
evaporation rate if that frequency was increased to 200
K.C. This was a difficult step because no core material existed at that
time to make a suitable transformer to step the voltage down and the
current up to about 100 amps at seven volts for ideal operation of the
I devised a resonant "T" matching net
consisting of a coil of 1/4 inch copper tubing about 6" in diameter
and 10 inches long so it could be varied for tuning by moving the turns
closer together or farther apart, and a large capacitance mica condenser.
The mica capacitor was made by connecting in parallel a
number of the series elements from World War I
surplus spark transmitter capacitors from our basement stock of junk. This
capacitor had to be placed in a circle since "skin effect" would
prevent current from flowing in the inner ones if they were stacked
sandwich style. Turning this to give optimum filament heat from a 1
kilowatt 100 K.C. oscillator was a tedious process, since
the filament had to be observed through a 3" glass window in the wall
of the cyclotron chamber.
In operation the filament was at 1000 volts D.C. above
ground with a 1 ampere supply to form a deturium arc
for the ion supply
to the center of the cyclotron.
I asked my lead crew member of the morning shift to
guard the controls so that I could tune up by shaping the matching coil
bare handed without the 1000 volt 1 ampere supply being turned on.
The tuning took longer than we expected and my control
guard became impatient and turned on the arc voltage while I was still in
I remember falling over from my squatting position and
thinking, "What a big earthquake to move the 70 ton magnet so
rapidly." Of course,
I was falling over as a result of the shock and
fortunately fell free of my contact. I must have yelled, because I came to
to find myself being brought to an upright stance by Robert Cornog and Dr.
Louis Alvarez. I took a deep breath and realized that my heart was shaking
in a violent spasm rather than beating. My early
experience as a Junior in college with Biofeedback came to mind
-- page 14-
and I exerted
mental control and stopped the fibulation and started a good solid beat.
The results of this experience were: first my personal
discomfort due to internal electrical burn, which caused my sweat to be
very stinky for at least six weeks and, a period of recovery from general
shakiness and weakness. The external burns at contact points on hands and
elbows were nominal. The other result was to make the whole lab conscious
of the necessity of safety interlocks and their intelligent use.
There followed a period of examining and rebuilding all
the safety features of our system. We already had interlocks on all
water cooling systems, but had perhaps not given sufficient attention to
problems of personal safety.
My solution to the filament problem: worked filaments
now lasted a week to ten days of approximately continuous operation.
helped the rapid conclusion of many a Doctoral Thesis.*
However, at this time we had other lessons to learn.
With the new 'Dee' voltage
available someone forgot to have the ion
source on when the '
Dee' voltage was turned
on and the unloaded
'Dee' voltage rose to over 150 kilovolts at which
point the external glass
insulators, where the ' Dee' stems
entered the vacuum chamber, arced over in the
outside air and the arcs quickly broke the glass on
both insulators. This required more than a day
of shutdown to fix.
New insulators were available,
but needed annealing to remove
However, Lawrence was so
pleased with the demonstration
of high voltage ability that he made
no adverse comment, only urging us
to fix the new insulators in place as rapidly as possible.
The climax of the experience
came several weeks
later when Dr.
Cocroft came from England to visit the lab.
Cocroft had been a severe critic
of the cyclotron saying that we really didn't have
energy we claimed
and were being
misled by radio
frequency arc phenomena
we did not
understand. So with great
pride Lawrence had me put on a target with a 1/2 inch
aluminum foil window (microphone diaphragm stock)
which with outside air cooling would let
a considerable beam of 8 M.E.V. Deuterons out in
(the) air so that the range and
ionization of the particles in ambient
air could be easily seen. The swell
of ozone was very strong.
After looking at
this display, Cocroft
agreed that the
observed range showed we had real energetic particles as
I was overseeing
the control station
with a young graduate
student from India,
whose name I
no longer remember,
at the controls.
Lawrence proudly pointed out to Cocroft the Dee voltage
indicated on the meters and explained the calibration
Suddenly he said to Cocroft, "Would
you like to see what is inside the cyclotron?"
"I would be most interested, " replied
Then with no hesitation, Lawrence reached over the
operator's shoulder and pushed the off button for
the ton (ion?) source arc voltage.
The 'Dee' voltage
rose instantly and with a great crash destroyed the
"Now boys," said
Lawrence, "Take it apart and
show Dr. Cocroft and put in new
insulators." (At least a two shift job.)
I was dismayed only
for an instant for
I understood at
once such bold showmanship.
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