Tsuneo Ito (no relationship to Yoji Ito) at
Tokoku University developed an 8-split-anode magnetron that produced about 10 W at 10 cm (3 GHz). Based on its appearance, it was named
Tachibana (or Mandarin, an orange citrus fruit). Tsuneo Ito joined the NTRI and continued his research on magnetrons in association with Yoji Ito. In 1937, they developed the technique of coupling adjacent segments (calling it push-pull), resulting in frequency stability, an extremely important magnetron breakthrough.
[2][3]
Shigeru Nakajima,
[4] a younger brother of Yoji Ito and a scientist at the
Japan Radio Company (JRC), was also investigating magnetrons, primarily for the medical
dielectric heating (diathermy) market. An alliance was made between NTRI and JRC for further magnetron development.
In early 1939, led by Yoji Ito they built a 10-cm (3-GHz), stable-frequency Mandarin-type magnetron (No. M3) that, with water cooling, could produce 500-W power.[2]
Development at the NTRI continued on magnetrons, resulting in higher and higher power. Yoji Ito and others eventually came to believe that this device might be used as a weapon, encouraged by an earlier newspaper article telling of Nikola Tesla inventing a beam that would “bring down squadrons of aircraft 250 miles away.”
[7] In 1943, work began in highest secrecy on a
Ku-go (Death Ray) device.
A special laboratory was set up near
Shimada, in the
Shizuoka Prefecture, for developing a high-power magnetron that, if not as powerful as Tesla had boasted, might at least incapacitate an aircraft. A number of Japan’s leading physicists were involved. A 20 cm magnetron producing 100 kW was achieved, and by the end of the war a 1000 kW (1 MW) unit was undergoing preliminary testing.
[6] At that time, the development was terminated and the hardware as well as all documentation was destroyed.
[8]