Bunsaku Arakatsu

Bunsaku Arakatsu (荒勝文策) 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.

Career
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 Taihoku, Formosa (now Taipei, Taiwan), and performed the first atomic nucleus collision experiment in Asia there, 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).

In 1943, during World War II, he ran the Japanese Naval research program into nuclear technology, known as the F-Go Project. Next to Yoshio Nishina, Arakatsu was the most notable nuclear physicist in Japan. His team included Hideki Yukawa, who would become in 1949 the first Japanese physicist to receive a Nobel Prize.

Early on in the war Commander Kitagawa, head of the Navy Research Institute's Chemical Section, had requested Arakatsu to carry out work on the separation of Uranium-235. The work went slowly, but shortly before the end of the war he had designed an ultracentrifuge (to spin at 60,000 rpm) which he was hopeful would achieve the required results. Only the design of the machinery was completed before the Japanese surrender.

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.

Honors

 * 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)