Evening star., 1939-12-02
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
By Thomas r. Henry.

By Thomas r. Henry.
The Bureau of Standards Is soon to
have the highest voltage X-ray tube in
the world, built to operate at 1,40O 900
volts.
At the same time one of the most
powerful constant voltage, direct cur
rent generators ever made will be put
into service.
Both are now being constructed by the
General Electric Co. at its Schenectady
plant
The new equipment will be used for
research work in the high-voltage field
especially in the measurement Of x
ray voltage. This will be Of value to the
medical profession, which for several
years has been using 2ooo0o-volt x-rays
in the treatment Of cancer and has re-
Gently been extending this to higher and
higher voltages.
The same high-voltage generator,
with another multisection tube dupli-
eating the X-ray tube in many respects,
can be used for production of neutrons
and artificial radioactivity. This tube
is composed of 10 sections of 100000
volts each. 1t is mounted vertically and
the envelope, consisting of 10 glass cyl
inders placed end to end, will be me-
chanically shielded against breakage
for its entire length with string en-
velope of insulating material. The cleo
tron beam which will travel "a feet from
the cathode at the top of the tube to
the target at the bottom must be accu-
rately aimed to strike the target and
must be of the proper size.
For the satisfactory operation Of the
X-ray tube it is essential that all the
electrons leaving the cathode should
reach the anode-that none of them
should strike either the glass walls of the
tube or the various metal electrodes. This
necessitates not only starting out all the
electrons In the right direction, but
guarding them from the DETECTING action
of magnetic fields. 1t also necessitates
the attainment throughout the length
of the tube of high degree of symmetry
about its axis.
The construction of the tube, accord
ing to the General Electric Co. an
nouncement, permits unique method
of applying energy to the electron beam
after it leaves it's anode. Starting at
zero velocity, the beam is accelerated
through the first section of the tube to
100000 electron volts velocity. AS it
enters the second section it receives an
additional voltage kick Of 100000. This
process is repeated through each section
of the tube so that when the electron
beam finally reaches its target its speed
is about 10000 miles second, very
nearly the velocity of light The tube,
however, may be operated at any lower
voltage down to 100000.
The high-voltage generator furnishing
power to the tube is also an unusual
step-up transformers capacitors and
rectifier tubes. There are 10 sections,
each rated at 100000 volts, connected
individually to the 10 sections Of the tube
and producing total Of 100000 volts.
The generator forms stack 80 feet high
and feet in diameter. 1t provides
very constant potential supply to the
x-ray tube.
The equipment will be housed in spe-
cial building now being constructed.
4x ~
Silicosis, lung malady aping tubercu-
losis, which is suffered by miners, stone
workers and others exposed to dusty
atmospheres, may be prevented by max
ing the air they breath still more dusty,
1t is revealed by experiments conducted
by Drs. L. H. Germer and K. H. Storks
of the Bell Telephone Laboratories.
These have just been reported to the
American Chemical Society. The expert
menters found that they could cause sill
COSTS rapidly in rabbits by exposing them
to air containing moderate concentrations
of quartz dust, in the form of particles
finer than a tWo-t -thousandth Of cent?
meter in diameter.
The animals did not develop the mall
ady, however, if there was also present
in the air they breathed aluminium pow
der to the extent of l per cent of the
silica particles. When both are breathed
into the lungs together, the two chemists
found, the aluminium forms protective
film on the surface Of the silica particles
which prevents them from dissolving,
and this prevents the toxic effect.
The protective film is hydrated oxide
of aluminium, so thin that no way exists
of making it visible. Its identity was
discovered by electron diffraction analy-
sis, in which beam of electrons was
passed through the film specimen and
the resulting diffraction pattern record
ed on Photographic plate.
1.-THE seriousness of silicosis in the
mining and foundry industries indicates
the Importance of Identification of this
finn they say in their report THE
smallness of the silica particles and the
very small amount of aluminium which
is sufficient to cover them with protec-
tive film make it evident that this film
is extremely thin. 1t is estimated that
film of one-forty- ty-thousandth of a milli-
meter thick will certainly prevent solu-
ton of the silica and its toxic effects.
The minimum thickness of film which
will prevent solution is probably many
times less than this figure.
There are reasons for believing that
the film is probably highly hydrated
gelatinous oxide which becomes crys-
talline only upon drying. These expert
ments have shown that the aluminium