Tihiro Ohkawa

Tihiro Ohkawa died in La Jolla, California, on 27 September 2014, age 86, after a brilliantly innovative career spanning more than six decades. Tihiro’s scientific ingenuity was wide-ranging, but he is best known as a longtime champion and pioneer of magnetic fusion energy research.

Born to an academic family in Kanazawa, Japan, in 1928, Tihiro was just sixteen when he started out in science. He matriculated at the University of Tokyo in 1950, studying nuclear physics. His first scientific publication, in 1953, described a new kind of particle accelerator. This led to an invitation to join physicist Donald Kerst in the U.S. for a year at the University of Illinois and another at the University of Wisconsin, where he improved the design of his fixed-field alternating-gradient accelerator. He then returned to the University of Tokyo. Meanwhile, Kerst joined General Atomics (GA), a spinoff of General Dynamics trying to develop peaceful atomic energy.

After a year at CERN in 1959, Ohkawa joined Kerst in San Diego and changed his focus to fusion energy research. Thus began what was to be a highly successful forty years spent seeking to bring fusion energy to realization.

Hydrogen nuclei fusing in the sun and other stars are confined by gravity. Tihiro was particularly intrigued by the prospect that magnetic confinement fusion on Earth could give humanity an endless supply of energy. Early Kerst/Ohkawa experiments in small toroidal machines were designed to demonstrate that fusion reactions might occur in scaled-up devices.

Kerst returned to Wisconsin after a funding cut in 1967, but Tihiro was ultimately able to obtain government funding to expand the research effort. Confinement research was key because it was widely believed (from several primitive experiments) that magnetic confinement in toroidal plasmas could be maintained no longer than the “Bohm time.” The Ohkawa group’s first major triumph was the demonstration, in their three-meter-high dc-Octopole, that the Bohm time was not an upper limit to confinement.

Tihiro saw insightfully that stably confining sufficient plasma pressure demanded highly shaped, vertically elongated plasma cross sections. He designed an elongated tokamak with a peanut-shaped cross section that he called a doublet, which he tried first in a tabletop version before building a larger Doublet II. Early results from these tokamaks were so encouraging that the group won a contract in 1973 to build a nine-meter-tall experiment, Doublet III.

By the end of the 1970s, Doublet III was a major national experiment, employing more than 200 experimentalists, theoreticians, engineers, and technicians. To extend the program and obtain major additional funding, Tihiro secured participation from the Japanese Atomic Energy Research Institute, forming the first of the many international collaborations that now characterize the GA fusion energy effort. In 1979, Tihiro won the James Clerk Maxwell Prize of the APS Division of Plasma Physics.

Doublet III was later upgraded to DIII-D, which continues as a leading facility in international fusion research. Modern tokamaks are highly shaped and vertically elongated.

In 1980, Tihiro tried another configuration, similar to a reversed-field pinch (RFP), which he called OHTE (the Japanese word for “check” in chess), with funding from GA and the Phillips Petroleum Corporation. The OHTE machine ran for eight years, producing good results and advancing the RFP concept.

While retaining his interest in fusion energy, in 1986 Tihiro began a new research endeavor at GA, which he called an “institute for the development of advanced technology,” exploring many disciplines including biotechnology, high-T superconductivity, and low-frequency communications. He left GA in 1994 to spend the next 20 years developing innovative solutions to many problems. He formed three companies, notably the Archimedes Technology Group, which focused on a new method of remediating nuclear waste. This was in some ways his most productive period. In all, he was the primary author of more than 170 scientific publications and held over 80 patents.

We and his other close associates will always cherish our memories of him—his deep intellect, his originality, his contests to spur creativity in others, and his vast interest in all forms of innovation. Physics was clearly his passion, but he participated in a range of other activities. He followed local professional sports teams and played golf, tennis, and soccer. He enjoyed annual family skiing and Las Vegas trips. His broad intellectual reach and his internationalism made him truly a citizen of the world, a consummate scientist who excelled at transcending boundaries!

John R. Gilleland
Richard Freeman
Robert L. Miller
Teruo Tamano