Albert W. Hull (nonfiction)
Albert Wallace Hull (19 April 1880 – 22 January 1966) is an American physicist and electrical engineer who made contributions to the development of vacuum tubes, and invented the magnetron.
In 1914 Hull joined the General Electric Research Laboratory (GERL) in Schenectady, New York and remained there until his retirement in 1949.
During 1916, Hull began investigation into the use of magnetic control of thermionic valves (vacuum tubes) as an alternative to grid or electrostatic control and he had tested successfully magnetic control by applying a magnetic field parallel to the axis of the tube. He invented the dynatron vacuum tube, which had three electrodes: a thermionic cathode, a perforated anode, and a supplementary anode or plate. In normal operation the supplementary anode was maintained at a lower positive voltage than the perforated anode. The secondary emission of electrons from the plate made the dynatron behave as a true negative resistance and so the tube could generate oscillations over a wide range of frequencies or be used as an amplifier. When a control grid was added between the cathode and the perforated anode, the device was called a "pliodynatron."
Initially, Hull's work on these novel electron tubes was part of an effort at General Electric to develop amplifiers and oscillators that might be used to circumvent the vacuum-tube triode patents of Lee de Forest and Edwin Armstrong.
By 1920 his research led to his invention of the magnetron. This took the form of a central cathode and a coaxial cylindrical anode split into two halves, 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. It was reported in 1925 that a magnetron made at GERL 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. Hull's split-anode magnetron did not prove to be capable of high frequency or high power output and was little used. However, during World War 2 John Randall and Harry Boot built on Hull's concept to develop the modern cavity magnetron, the first device which could produce high power at microwave frequencies, and the resulting centimeter-band radar proved a crucial advantage for the Allies in aerial warfare.
Hull was promoted to assistant director of the GERL in 1928. He served as president of the American Physical Society in 1942. He retired from General Electric Research Laboratory (GERL) in 1949.
He did consulting work and served on an advisory committee of the Army Ballistics Research Laboratories after retirement from General Electric.
He was a member of the National Academy of Sciences.
He died on 22 January 1966 at the age of 85 in Schenectady, New York.
In the News
Fiction cross-reference
Nonfiction cross-reference
- Edwin Armstrong (nonfiction)
- Harry Boot (nonfiction)
- John Randall (nonfiction)
- Lee de Forest (nonfiction)
- Physicist (nonfiction)
External links:
- Albert W. Hull @ Wikipedia