For longer operations with Doublet devices, the copper conducting shell had to be replaced by field-shaping coils surrounding the plasma chamber to control the plasma shape externally. In 1974, the Doublet II was converted into Doublet IIA (DIIA) with shaping coils. With successful operation of Doublet II and IIA, Ohkawa started planning the design of an even larger follow-on machine, the Doublet III (DIII).
During these years of developing and operating the Octopole and Doublet programs under the support of AEC, ERDA, and the Electric Power Research Institute (EPRI), Ohkawa added new scientists to his staff. Among them were Masaji Yoshikawa and Teruo Tamano, who, like Ohkawa, had studied at the University of Tokyo. They were joined by John Gilleland from the University of Michigan and Charlie Baker from the University of Wisconsin. They assisted Ohkawa in the early days of GA programs and helped the later expansion. Ming Chu was a key theorist during the expansion of the Doublet program. Baker recalled that in the lean early days of the GA fusion program, staff meetings could fit into Ohkawa's small office, but within two years, Ohkawa's leadership grew the fusion program to over 200 professionals.
Baker worked on the conceptual design and preliminary work for DIII, the critical test of Ohkawa's Doublet concept. "Its aim was to substantially improve the performance of the tokamak magnetic plasma confinement approach to fusion energy," he recalled. "It’s remarkable that Ohkawa was able to convince the U.S. government and many in the U.S. fusion community to undertake such an ambitious project."
It was here that another facet of Ohkawa’s genius began to show itself. He had learned the importance of attention to political and economic elements of big science projects through his experiences with MURA and the early debates over the Japanese fusion program. Despite his many responsibilities, Ohkawa kept a close eye on other global issues, such as international tensions during the Cold War, the oil shortage and ensuing energy crisis, and the economic growth of Asian countries. So when opportunities arrived, Ohkawa was ready. [AIP Ohkawa interview; Mori Interview; Teruo Tamano; Masana Nishikawa]
"The 1970s were heady times for U.S. fusion,” recalled Steve Dean (Fusion Power Associates and a former associate director of the U.S. fusion program). “The world was in the thralls of an oil shortage and energy crisis. The U.S. fusion budget grew tenfold during the 1970s and Tihiro was one of the national program leaders,"
A mockup one-turn coil of Doublet III displayed at the ground-breaking ceremony site in 1975. Front row: Tihiro Ohkawa (director, Fusion program, GA), Anne Davies and Steve Dean, (monitor of GA program and director of confinement system, DOE, respectively). Back row: Bob Hirsch (associate director of DOE Fusion Program), John Gilleland (DIII construction), Teruo Tamano (DIII physics), Corwin Rickard (VP, GA Fusion program) and Charlie Baker (Fusion technology, GA)