This is the birthplace of radioisotopes in Japan.

Japan's first cyclotron was constructed and started to produce radioisotopes at the site where the Japan Radioisotope Association is now located. When the hot laboratory in which we currently handle high-activity radioactive sources was constructed, a monument was erected commemorating the electromagnet used to produce radioisotopes at this important facility and explaining its significance.

The first Japanese cyclotron was constructed in 1937 at the Nishina Laboratory of the Physical and Chemical Research Institute (RIKEN foundation) to conduct basic research in the field of nuclear physics. This first cyclotron was equipped with a 26-inch diameter magnetic pole. A second cyclotron was constructed in 1944 with a 60-inch diameter pole.

In November 1945, these two cyclotrons were removed and disposed of by the Allied Forces.

In 1951, a private company known as Kagaku Kenkyusho (KAKEN), or the Scientific Research Institute Ltd., took over the Physical and Chemical Research Institute and rebuilt the 26-inch cyclotron when Professor E. O. Lawrence, the originator of the cyclotron, visited Japan. This cyclotron was then used to produce radioisotopes for about a decade.

In 1972, the Japan Radioisotope Association constructed its second hot laboratory for handling gamma ray sources at the same site where the 60-inch cyclotron had originally been installed.
This electromagnet is the same one that was used in the small-scale, rebuilt cyclotron and has been preserved to commemorate the history and achievements of the scientists involved.

Fumio Yamazaki, Former Executive Director
(Built in June 1982)