Bunsaku Arakatsu (荒胜文策?, 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.
In 1934 Arakatsu built a particle accelerator. He discovered that each nuclear fission of a U-235 atom yields, on average, 2.6 neutrons. He published his results on October 6, 1939, in the Physical Review. In the following years he led other physicists at the University of Kyoto 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, 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.
The following are books or papers published by refereed scientific journals:
- 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
- Medal with Purple Ribbon (1961)
- Order of the Rising Sun, 3rd class (1965)
- Order of the Rising Sun, 2nd class (1973; posthumous)
Order of precedence
- Third rank (1973; posthumous)