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Albert W. Hull (1880-
1966)
Albert Wallace Hull
was born on a farm in Southington, Connecticut, on
April 19, 1880. He was the
second oldest of eight boys, five of whom chose technical careers:
physics,
bacteriology, metallurgy, forestry, and engineering. All five went to
Yale,
where Albert majored in Greek and took one undergraduate course in
physics. He
taught languages at Albany
Academy
for a time before
deciding to return to Yale, where he earned a Ph.D. in physics in 1909.
He then
taught physics for five years at the Worcester Polytechnic Institute
while
doing research on photoelectricity. The excellence of his work became
known to Irving Langmuir and William Coolidge who invited him to the GE
Research Laboratory in Schenectady
for the
summer of 1913. After finishing a year of teaching, he returned to Schenectady,
never to
leave. In 1928, he became assistant director of the Laboratory.
Hull was the
creator of a greater number of new types of electron tubes than
any other man, and made important contributions to the fundamentals of
physical
science as well. His first work at the laboratory was on electron
tubes, X-ray
crystallography, and piezoelectricity. After World War I, he published
a
classic paper on the effect of uniform magnetic fields on the motion
of
electrons between coaxial cylinders. During the 1920s, he studied noise
in
diodes and triodes, which led to the development of the tetrode, or
screen grid
tube. During this same period, he invented the thyratron, a gas-filled
electron
tube that found application in the control of medium powered devices
and led
the way to a new branch of technology, industrial electronics.
During the 1930s, he
directed his research to metallurgy and glass
science, which led to the development of new alloys such as Fernico.
Albert Hull's
industrial scientific work with GE has had tremendous scientific and
practical
consequences. Together with Coolidge's work on tungsten and Langmuir's
work on
high vacuum electronic phenomena, he was one of the pioneers who
provided the
foundation for the electronics businesses of General Electric. He
retired from
GE in 1950 but remained professionally active for many years after. His
last
publication, in 1966, came fifty-seven years after the first of many
honors
came to Hull: the Howard N. Potts Medal of the Franklin Institute,
given in
1923 for work on X-ray crystal analysis; the Morris Liebmann prize of
the
Institute of Radio Engineers in 1930 for his work on vacuum tubes;
membership
in the National Academy of Sciences; and president of the American
Physical
Society.
During 1916, Hull began
experiments on the use of magnetic
control of vacuum tubes as an alternative to grid or electrostatic
control as suggested to him by Dr. Ernst
Alexanderson, who wanted to make a switching device. In the
1918 issue of the Proceedings of the IRE
he
published a paper on a vacuum tube which he had invented called the
dynatron.
The dynatron had three electrodes: a thermionic cathode, a perforated
anode,
and a supplementary anode or plate. In normal operation the plate was
maintained at a lower positive potential than the perforated anode. Hull explained
that
secondary emission of electrons from the plate caused the dynatron to
behave as
a "true negative resistance." Thus the tube could be used as an
amplifier or could generate oscillations over a wide range of
frequencies. If a
control grid were added between the cathode and the perforated anode,
the
device became what Hull
called a "pliodynatron." In addition to grid control, he had tested
successfully magnetic control by applying a magnetic field parallel to
the axis
of the tube.
By
1920 this research led to his invention of the magnetron, which took
the form of a coaxial cylindrical anode and cathode with an axial
magnetic field produced by an external coil. The Hull magnetron was
tested as an amplifier in radio receivers and also as a low-frequency
oscillator. By 1925, a magnetron made at the GE Research
Laboratory could
generate a power of 15 kW at a frequency of 20 kHz. At the time, Hull
anticipated that the magnetron would find greater use as a power
converter than in communication applications.
After retirement 1n 1950, Hull
did consulting work
and served on an advisory committee of the Army Ballistics Research
Laboratories. He died on 22 January 1966 at the age of 85.
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