Shoroku Ohnuma, who made significant contributions to accelerator physics in the US and Japan, passed away on 4 February 2024, at the age of 95.
Born on 19 April 1928, in Akita Prefecture, Japan, Ohnuma graduated from the University of Tokyo’s Physics Department in 1950. After studying with Yoichiro Nambu at Osaka University, he came to the US as a Fulbright scholar in 1953, obtaining his doctorate from the University of Rochester in 1956. He maintained a lifelong friendship with neutrino astrophysicist Masatoshi Koshiba, who received his degree from Rochester in the same period. A photo published in the Japanese national newspaper Asahi Shimbun shows him with Koshiba, Richard Feynman and Nambu when the latter won the Nobel Prize in Physics – Ohnuma would often joke that he was the only one pictured who did not win a Nobel.
Ohnuma spent three years doing research at Yale University before returning to Japan to teach at Waseda University. In 1962 he returned to the US with his wife and infant daughter Keiko to work on linear accelerators at Yale. In 1970 he joined the Fermi National Accelerator Laboratory (FNAL), where he contributed significantly to the completion of the Tevatron before moving to the University of Houston in 1986, where he worked on the Superconducting Super Collider (SSC). While he claimed to have moved to Texas because his work at FNAL was done, he must have had high hopes for the SSC, which the first Bush administration slated to be built in Dallas in 1989. Young researchers who worked with him, including me, made up an energetic but inexperienced working team of accelerator researchers. With many FNAL-linked people such as Helen Edwards in the leadership of SSC, we frequently invited professor Ohnuma to Dallas to review the overall design. He was a mentor to me for more than 35 years after our work together at the Texas Accelerator Center in 1988.
Ohnuma reviewed accelerator designs and educated students and young researchers in the US and Japan
After Congress cancelled the SSC in 1993, Ohnuma continued his research at the University of Houston until 1999. Starting in the late 1990s, he visited the JHF, later J-PARC, accelerator group led by Yoshiharu Mori at the University of Tokyo’s Institute for Nuclear Study almost every year. As a member of JHF’s first International Advisory Committee, he reviewed the accelerator design and educated students and young researchers, whom he considered his grandchildren. Indeed, his guidance had grown gentler and more grandfatherly.
In 2000, in semi-retirement, Ohnuma settled at the University of Hawaii, where he continued to frequent the campus most weekdays until his death. Even after the loss of his wife in 2021, he continued walking every day, taking a bus to the university, doing volunteer work at a senior facility, and visiting the Buddhist temple every Sunday. His interest in Zen Buddhism had grown after retirement, and he resolved to copy the Heart Sutra a thousand times on rice paper, with the sumi brush and ink prepared from scratch. We were entertained by his panic at having nearly achieved his goal too soon before his death. The Heart Sutra is a foundational text in Zen Buddhism, chanted on every formal occasion. Undertaking to copy it 1000 times exemplified his considerable tenacity and dedication. Whatever he undertook in the way of study, he was unhurried and unworried, optimistic and cheerful, and persistent.
