— Sir Humphry Davy (1778 – 1829), Thomas Hager, Force of Nature, Simon and Schuster, New York, 1995, p 86.
It’s nothing systematic, I’ve just the feeling that someone
who invents a cloud chamber or a Geiger counter does more than someone doing an
experiment.
— Otto Robert Frisch (1904 – 1979).
[Of the Wilson cloud chamber] In a recent communication, I
described a method of making visible the tracks of ionising particles through a
moist gas by condensing water upon the ions immediately after their liberation.
At that time I had only succeeded in taking photographs of the clouds condensed
on the ions produced along the tracks of alpha-particles and of the corpuscles
set free by the passage of X-rays through the gas. The interpretation of the
photographs was complicated to a certain extent by distortion arising from the
position which the camera occupied.
The expansion apparatus and the method of illuminating the
clouds have both been improved in detail, and it has now been found possible to
photograph the tracks of even the fastest beta-particles, the individual ions
being rendered visible. In the photographs of the X-ray clouds the drops in
many of the tracks are also individually visible; the clouds found in the
alpha-ray tracks are generally too dense to be resolved into drops. The
photographs are now free from distortion. The cloud chamber has been greatly
increased in size; it is now wide enough to give ample room for the longest
alpha-ray, and high enough to admit of a horizontal beam of X-rays being sent
through it without any risk of complications due to the proximity of the roof
and floor.
— Charles Thomson Rees Wilson (1869 – 1959), Proceedings of the Royal Society, 1912, A, 87, 277.
The older Wilson cloud chamber had two difficulties that
rendered it unsuitable for the job: if used at atmospheric pressure, its
cycling period was measured in minutes, and if one increased its pressure to
compensate for the long mean free path of nuclear interactions, its cycling
period increased at least as fast as the pressure was increased. Therefore the
number of observed reactions per day started at an almost impossibly low value,
and dropped as ‘corrective action’ was taken. The diffusion cloud chamber was
plagued by ‘background problems’, and had an additional disadvantage — its
sensitive volume was confined in the vertical direction to a height of only a
few centimetres. What we concluded from all this was simply that particle
physicists needed a track-recording device with solid or liquid density … with
uniform sensitivity … and with fast cycling time … And of course, any cycling
detector would permit the association of charged tracks joined by neutral
tracks, which was denied to the user of nuclear emulsion.
[In 1953, in a hotel garden in during a conference] … A
young chap … was seated at my left, and we were soon talking of our interests
in physics. He expressed concern that no one would hear his 10-minute
contributed paper, because it was scheduled as the final paper of the Saturday
afternoon session … I admitted that I wouldn’t be there and asked him to tell
me what he would be reporting. And that is how I heard first hand from Donald
Glaser how he had invented the bubble chamber … I was greatly impressed by his
work, and it immediately occurred to me that this could be the ‘big idea’ I
felt was needed in particle physics.
— Luis W Alvarez (1911 – 1988), Nobel Lecture in physics, 1968.
One evening early in 1929 as I was glancing over current
periodicals in the University library, I came across an article in a German
electrical engineering journal by Wideroe on the multiple acceleration of
positive ions. Not being able to read German easily, I merely looked at the
diagrams and photographs of Wideroe’s apparatus and from the various figures in
the article was able to determine his general approach to the problem i. e. the
multiple acceleration of the positive ions by appropriate application of radio
frequency oscillating voltages to a series of cylindrical electrodes in line.
This new idea immediately impressed me as the real answer which I had been
looking for to the technical problem of accelerating ions, and without looking
at the article further I then and there made estimates of the general features
of a linear accelerator for protons in the energy range above one million volt
electrons. Simple calculations showed that the accelerator tube would be some
metres in length which at that time seemed rather awkwardly long for laboratory
purposes. And accordingly, I asked myself the question, instead of using a
large number of cylindrical electrodes in line, might it not be possible to use
two electrodes over and over again by bending the positive ions back and forth
through the electrodes by some sort of appropriate magnetic field arrangement.
Again a little analysis of the problem showed that a uniform magnetic field had
just the right properties that the angular velocity of the ions circulating in
the field would be independent of their energy so that they would circulate
back and forth between suitable hollow electrodes in resonance with an
oscillating electrical field of a certain frequency which has now become known
as the ‘cyclotron frequency’.
— Ernest Orlando Lawrence (1901 – 1958), Nobel lecture, 1939.
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