Bruce Sween Liley, one of the pioneer physicists in the UK’s fusion research program, died on 19 May 2001 in Hamilton, New Zealand, after a long and stoic battle with a debilitating respiratory illness. During the 15 or so years of his career when he was closely involved in experimental fusion research, Liley played an important and highly original role in the long and continuing quest for nuclear fusion power.

Liley was born on 7 September 1928 in Havelock North, New Zealand. He obtained an MSc in mathematics in 1951 from Otago University College, University of New Zealand, and a master’s degree in physics in 1955 from Auckland University College (now the University of Auckland).

Liley worked on a team that was developing George Thomson’s ideas for building a thermonuclear reactor to produce power from the fusion reactions of hydrogen discovered in the 1930s by Mark Oliphant and Ernest Rutherford. Thomson received a patent in 1948 to produce useful power from these reactions and started a group, led by one of us (Ware), at Imperial College London to work on this idea. When the UK fusion program was classified in 1951 because of fears that the research could lead to a source of neutrons for breeding plutonium, the group moved to the Associated Electrical Industries (AEI) Research Laboratory at Aldermaston. Another fusion research group, this one at Oxford University, later moved to the Atomic Energy Research Establishment at Harwell and became the forerunners of the present Culham Laboratory.

Liley joined the team at AEI shortly after its start and quickly became the leading theoretician supporting the experimental program. While at AEI, he enrolled as a graduate student at the nearby Reading University and did theoretical research for his PhD, which he earned in 1963. His research involved adapting Harold Grad’s 13-moment approximation to obtain transport equations for a fully ionized plasma, and his findings were published in Reviews ofModern Physics in 1960. Those equations are still being used in present research.

Thomson’s patent evolved into the Sceptre series of devices—which, like the Harwell machine Zeta, would nowadays be called reversed field pinches—ending with Sceptre IV in 1959–60. Although a theoretician by training, Liley was at the heart of this work. He proposed and helped design an alternative to the Sceptre–Zeta approach: a levitron, which was essentially a current-carrying ring suspended in a vacuum chamber. But, before Liley’s apparatus could be properly exploited, AEI decided to close the laboratory in 1963 because of funding problems. The entire team was dispersed, many to fusion laboratories around the world.

That same year, Liley joined the Australian National University (ANU) in Canberra to work in the Research School of Physical Sciences that had been formed by Oliphant after World War II. Liley’s team built a device similar to that at AEI but with much stronger toroidal magnetic fields. Liley called his new device a “slow toroidal theta-z pinch.” In modern terminology, the slow theta-pinch aspects would be referred to as adiabatic compression of the toroidal field. The experiment LT-1—which, on acquiring upgrades of its power supplies also upgraded its name to LT-2 and LT-3—was a pilot for what Liley later hoped would be a much larger experiment along these lines.

That larger experiment was not to be built during his residence in Canberra, but the pilot experiment was interesting in its own right. Having a strong toroidal field, the device Liley’s team built operated in much the same way as the early Russian tokamaks. Deleterious periodic “disruptive instabilities” plagued both sorts of device. Eventually, extensive Russian efforts were devoted to successfully avoiding these instabilities and producing a hot, well-confined plasma. Liley’s group decided to study the instabilities in detail; they produced important insights into the phenomenon, for example, that a disruption rapidly redistributed the current throughout the plasma column (see the article by David Bowers and others in Plasma Physics , vol. 13, 1971, page 1201). That phenomenon is still the most serious limitation to tokamak operation. Their work also stimulated development of the Ware pinch effect theory.

The LT-1 experiment, which became operational around 1965, can justifiably be considered the first tokamak outside Russia. When the high temperatures and excellent confinement of the Russian T-3 experiment were confirmed in 1968, interest in the tokamak configuration swept the world, and Liley’s group found themselves with what was then a hot research commodity: a tokamak. Two PhD students, David Bowers and Evan Bydder, worked with Liley on LT-1, and LT-3 was the machine on which three now senior physicists in US fusion research, James Strachan, Michael Bell, and one of us (Hutchinson), learned “to drive” a tokamak.

In 1969, Liley moved to Hamilton, where he became the Foundation Professor of Physics at the new University of Waikato. Although he continued theoretical work in fusion and continued to visit the group he had started at ANU, this move marked the start of a second career. Liley built a very successful physics department, struggling hard to encourage and provide excellence, success, integrity, and growth. He was instrumental in promoting various community activities, particularly in astronomy and local industry. He was an ardent supporter of the BSc (technology) program and other industry collaboration programs that were introduced to New Zealand by the Waikato University physics department. He also was a member of the Royal Commission on Nuclear Power Generation in New Zealand (1978).

Liley will be remembered internationally as a true research physicist who was determined to tackle important problems with original ideas and a lot of hard work.

Bruce Sween Liley