 A recording
equipment for high speed particles has been built and installed in
the research department for use with the betatron. It consists of
ionization tubes known as.Geiger counters, which produce a minute
electrical impulse every time a subatomic particle passes through
them; the number of impulses is accurately recorded no matter how
often they occur, which may vary from once a week to several times
in a millisecond. The equipment can deal with any high speed particles,
whether alpha, beta, gamma, or cosmic radiation, encountered in nuclear
physics.
Early
in 1944 the Company was asked by the Ministry of Supply to make
mass spectrometers, an instrument invented for the precise measurement
of the abundance ratios of isotopes in the naturally occurring elements.
A recording spectrometer suitable for general purposes was developed
under R. W. Sillars and J. Blears, and the first has just been installed
in the physical chemistry laboratory at Oxford; it can measure ions
whose mass and electron charge are in any ratio from 1 to 200. Subsequently
a much smaller machine was designed, covering ratios from 1 to 20.
The
mass spectrometer has some essential and many useful applications
in atomic energy work, biology, medicine and engineering. It is
indispensable for studying the success of the process of separating
the 235 and 238 isotopes of uranium in the manufacture of fissile
material. It can trace the movement of stable isotopes of carbon,
nitrogen, oxygen, sulphur and so on in living organisms, giving
a valuable method of studying the mechanism of plant and animal
life, and can be used to study gas reactions (as in arc welding),
the fuel present in exhaust gases, the thermal stability of organic
fluids, and the characteristics of insulating gases.
HIGH VOLTAGE WORK
High voltage equipments have been made and installed at industrial
and university laboratories. They include impulse generators,
high voltage transformers, Schering bridges, conditioning ovens,
cathode ray oscillographs, and measuring apparatus. Work on the
standardization of impulse testing^ undertaken in cooperation
with the B.S.I, and now generally adopted, has been an important
activity of the Company's high voltage laboratory, which is probably
the most extensive and complete in the country.
The
development of the electron microscope and associated apparatus
was resumed under F. R. Perry before the end of the war, and an
improved type was soon made available. This was a two-stage 50-kV
instrument and gave direct magnifications from 10,000 to 20,000.
The high tension supply set was a 50-c/s half-wave rectifier unit,
and the microscope controls and stabilizing amplifiers were mounted
in a separate cubicle.
In
1947 an entirely new design was brought out, a 100-kV model. The
higher intensity of the electron gun enabled the maximum direct
magnification to be raised to 100,000, and by means of the double
projector lens the magnification can be varied continuously and
widely without altering the focal length of the objective.
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