Bunsaku Arakatsu

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Bunsaku Arakatsu
Bunsaku Arakatsu.png
Born 1890 (1890)
Himeji, Hyōgo, Japan
Died 1973 (1974) (aged 83)
Kobe, Hyōgo, Japan
Other names 荒勝文策, あらかつ ぶんさく
Institutions Taihoku Imperial University
Kyoto Imperial University
Konan University
Academic advisors Albert Einstein, Paul Scherrer

Bunsaku Arakatsu (荒勝文策, あらかつ ぶんさく, 25 March 1890 – 25 June 1973) was a Japanese physics professor, in the World War II Japanese Atomic Energy Research Program of the Imperial Japanese Navy. Arakatsu was a former student of Albert Einstein.


Arakatsu and his accelerator at Kyoto Imperial University.
Arakatsu's accelerator demolishing by GHQ.

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 Asia there,[1][2] 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.[3] 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.


The following are books or papers published by refereed scientific journals:[4]

  • The continuous spectrum of Hydrogen associated with each of the lines in the Balmer series, 1932, 1 edition published in English and held by 8 libraries worldwide
  • The principle of the conservation of angular momentum or the principle of the conservation of the symmetry or antisymmetry of the total wave function (Bose or Fermi Statistics) in molecules, 1932, 1 edition in English and held by 7 libraries worldwide
  • On some peculiar phenomena of the electrodeless ring discharge through Hydrogen in a long tube, 1932, 1 edition published in 1932 in English and held by 7 libraries worldwide
  • Notes on the validity of the principle of the conservation of spin angular momentum in the process of the artificial disintegration of lithium atoms, 1934, 1 edition published in English and held by 6 libraries worldwide
  • Experimental studies on the artificial transmutation of certain light elements bombarded by ions of hydrogen and heavy hydrogen" in English and held by 6 libraries worldwide
  • On the anomalous absorption of [gamma]-rays. (The possibility of the quantum jump of the rest-mass of an electron.) 1932, 1 edition in English and held by 5 libraries worldwide
  • The electrodeless ring discharge through potassium vapour 1932, 1 edition published in English and held by 5 libraries worldwide
  • The activation of air by the electrodeless ring discharge, 1932, 1 edition published in English and held by 5 libraries worldwide
  • On the anomalous absorption of -rays, 1932, 1 edition published in English and held by 3 libraries worldwide
  • Hiroshima atomic bomb, August 1945 and super-hydrogen bomb test at Bikini Atoll in the mid-Pacific, March 1954, 1995, 1 edition published in English and held by 2 libraries worldwide


Order of precedence[edit]

  • Third rank (1973; posthumous)

See also[edit]


  1. ^ 張幸真 (31 July 2003). "台灣知識社群的轉變-以台北帝國大學物理講座到台灣大學物理系為例" (in Chinese): 20. Retrieved 2012-06-11. 
  2. ^ 鄭伯昆 (February 1993). "民國40年前後在台大二號館的原子核實驗室-述許雲基先生早期的工作及其貢獻". 物理雙月刊. Taipei: 中華民國物理學會. 15 (1): 141–144. Retrieved 2012-06-01. 
  3. ^ "The Last voyage of U-234...". eb.archive.org. Archived from the original on 2013-12-17. Retrieved 2014-01-27. 
  4. ^ "近代物理学". worldcat.org. Retrieved 2014-01-27. 


  • Rainer Karlsch - Zbynek Zeman, uranium secrets, 2003 - ISBN 3-86153-276-X
  • Excerpt from Keiko Nagase-Reimer: Research on the use of nuclear energy in Japan, 1938–1945. Marburg: Marburg Friends of Japan Series c / o Japan Center, Philipps-University, 2002. ISBN 3-927607-53-3