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Bunsaku Arakatsu Edit Profile

physics professor

Bunsaku Arakatsu was a Japanese physics professor, in the World War II Japanese Atomic Energy Research Program of the Imperial Japanese Navy.


Bunsaku Arakatsu was born in 1890.


In 1928, Arakatsu became a professor in Taihoku Imperial University (now called National Taiwan University). In 1934 Arakatsu built a particle accelerator at Taihoku Imperial University in Taipei, Taiwan, and performed the first atomic nucleus collision experiment in Asiathere, right after the experiment performed in Cavendish Laboratory of University of Cambridge. He discovered that each nuclear fission of a U-235 atom yields, on average, 2.6 neutrons. In 1936, he became a professor in Kyoto Imperial University (now called University of Kyoto). He published his results on October 6, 1939, in the Physical Review. In the following years he led other physicists at the Kyoto Imperial University in discussions on the uses of nuclear energy and the possibility of the development of a nuclear bomb. For this purpose, he assembled a research and development team, which included physicists Sakae Shimizu and Hideki Yukawa, who later became a Nobel physics laureate. The Institute for Chemical and Physical Research and an affiliate in Hŭngnam (now in North Korea) supported these efforts. In 1942, the project started under the code name F-Go and was primarily intended to replace oil by nuclear power. Oil had become a precious commodity and petroleum had become scarcer, undermining the war effort. In this respect it differed little from a tarnished Germany's nuclear program. The more the tide turned against the Japanese, the more intense was the research to build a nuclear bomb.

After the Americans atom bombed Hiroshima, he was transferred to Navy Minister Mitsumasa Yonai to form an investigative commission. This commission inspected the affected area to determine the effects of the bomb.

After the war, his reports and artifacts were largely destroyed or confiscated by the occupying GHQ, which brought much protest from Arakatsu and the international community. Whatever documents that had survived the purge are now kept in the Yamato Museum in Kure.