![]() (Fig.1b) 1b) (Department of Chemistry, the University of Tokyo), and obtained several remarkable results, including the discovery of a new radioactive isotope of uranium, 237U, the discovery of symmetric nuclear fission and a trial to discover the missing element of atomic number 93. In the physical and chemical fields, he carried out fast-neutron bombardment experiments on thorium or uranium in cooperation with Kenjiro Kimura (Fig. He also started studies on the biological effects of radiations produced by the cyclotron. Nishina prepared such radioisotopes as 11C, 13N, 24Na and 32P with his cyclotron, and applied them to biological tracer studies, obtaining many interesting results. Nishina’s 27 inch cyclotron constructed on the campus of the Institute of Physical and Chemical Research, Tokyo in 1937. Thus, Japan became the second cyclotron-possessing country in the world after the United States. The construction of the cyclotron started in 1935 and was completed in 1937 (Fig. ![]() He intended to construct a 27 inch cyclotron on the campus of the Institute of Physical and Chemical Research (RIKEN) in Tokyo. (Fig.1a) 1a) had the opinion that a cyclotron is essentially necessary for Japan to develop experimental nuclear physics as well as to promote the production and application of radioisotopes. These important inventions and discoveries led to the rapid development of a new field of nuclear physical and radiochemical studies on artificial nuclear transformation.Īt that time, Yoshio Nishina (Fig. Joliot-Curie (1934) 4) were successively reported. Urey (1932) 3) and the discovery of artificial radioisotopes by J.F. Chadwick (1932), 2) the discovery of deuterium by H.C. Lawrence (1931), 1) the discovery of neutron by J. At the beginning of the 1930’s, epoch-making inventions or discoveries including the invention of the cyclotron by E.O. ![]()
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