 First
a 250-kV medical tube was developed in the high voltage laboratory,
and by 1934 two had been put into operation in the Sheffield Infirmary;
these were so successful that further equipments were made, including
four for the Christie Hospital in Manchester and four for the Middlesex.
Later several tubes of similar design but operating at 500 kV were
put into service. Early in 1936 an equipment working at a million
volts was attempted, and in November of that year it was installed
in St. Bartholomew's Hospital; it has been in service for many years
operating at 1,100,000 volts.
On
the crystallographic side the first continuously evacuated x-ray
tube was produced by C. Sykes, whose main object was to be able
to change the target fairly easily. It was provided with interchangeable
water-cooled targets, and its success led to the design of commercial
models, which soon became a standard product— the well-known
Raymax equipment. Later developments included powder cameras, x-ray
spectrometers, and crystallographic equipment having the extremely
fine focal spot of about 0-4x0-04 mm, which permits the study of
single crystal and crystal boundary conditions.
These were the foundations of the Company's x-ray business, now
handled through Newton Victor Limited.
The
electron microscope arose from the necessity to transcend the resolving
limit imposed on the optical microscope by the physical nature of
light. The substitution of a beam of electrons for a beam of light
was suggested, and by 1930 work had started in the research department.
The first British instrument was designed in cooperation with Professor
L. C. Martin of the Imperial College of Science and Technology,
where it was installed in 1936. Further development was held up
until after the war, when, much improved instruments were designed
and built.
RADIO VALVES
Continuously evacuated radio valves of high power had been investigated
by C. R. Burch's colleagues, who built by 1930 a triode of demountable
construction for an input power of 25 kW. So satisfactory was it
that the G.P.O. asked for a 500-kW valve to replace an existing
bank of fifty-four sealed-off valves in the Rugby wireless station:
with an overall weight of 33 cwt, this valve was easily the largest
in the world.
Following
further work by F. P. Burch (a brother of C. R.) and later J. M.
Dodds, other continuously evacuated valves were introduced for G.P.O.
service, and a short wave tetrode was added to the range. Sealed-off
valves for short wave operation were also made, and four were used
in power stages of the Baird transmitter, one of the two original
television transmitters installed at Alexandra Palace in 1936; this
apparatus was operated at wavelengths down to 6 metres in the world's
first regular television programme.
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