ChangXuan Yu

ChangXuan Yu, a leading scientist in plasma physics and controlled fusion in China and a prominent member of the international community, died of liver cancer at the age of 76 on 23 May 2017 in Hefei, Anhui Province of China. Yu was born in Indonesia on 7 July 1941. His family returned to China in 1948. After graduation from the Department of Modern Physics at University of Science and Technology of China (USTC) in 1965, Yu worked there on the faculty for the rest of his life.

Yu was a key figure in the Chinese fusion program since its early beginnings. In 1970 he and his colleagues established the Division of Plasma Physics at USTC, which was the first such division in Chinese universities. In the 1980s and 1990s, despite difficulties with limited funding and relevant expertise in China, he made a tremendous effort to develop advanced diagnostic systems and plasma devices. Together with his colleagues, a far-IR laser scattering diagnostic for turbulence investigation, a double plasma device for nonlinear plasma dynamics study, and a Thomson scattering system for laser plasma research were among the first experimental setups in China. The textbook, Techniques in High Temperature Plasmas Diagnostics, that he and Zhi-Lin Xiang published in 1982 has been one of the most classic reference books that educated and inspired generations of Chinese plasma physicists. Yu personally supervised close to 100 PhD and master’s students and co-supervised many others. Many of them have enjoyed successful professional careers in well-known research institutes and universities around the world, while many others are leading scientists in magnetic fusion and plasma physics in China.

Yu played a key role in drawing up the strategy for China’s fusion energy development, and he made strong efforts to establish and to lead the China Tokamak Physics Activity (CTPA) to carry on the domestic magnetic confinement fusion research program. In recent years, he devoted himself to the China Fusion Engineering Test Reactor (CFETR) project and spent considerable time carrying out his own calculations and estimates on the tritium self-sustainment issue, in spite of his illness, to ensure the success of the CFETR.

After the end of the Cultural Revolution, Yu was among the first Chinese scientists who went abroad to perform research in plasma physics. He was a visiting scientist at UCLA during the periods of 1980–1983, 1989–1991, and 2000–2001, collaborating with world experts at UCLA and UT-Austin as well as other institutions. He advocated the CTPA so that domestic tokamak physics activity can connect with international tokamak physics activity to support ITER. Yu had a rich career spanning topics including “Comparison of the density fluctuation spectrum and amplitude in TEXT with expectations for electron drift waves” to experimentally demonstrating control of undriven chaos in a DC discharge plasma system in the first time. In the Hefei Tokamak-6M, he provided the first experimental evidence of the correlation between the enhanced Reynolds stress gradient and the poloidal flow acceleration in the edge plasma, which may play a key role in the triggering of the L-H transition, which is of critical importance for the success of fusion energy. The signature of all of his work is the careful basic understanding of physics via the comparison between theory and experiment. In recognition of his fundamental plasma physics achievements, together with his contributions to both the Chinese and International fusion programs, he was elected as an Academician of the Chinese Academy of Sciences in 2007.

As a true scientist, Yu possessed rare qualities. A man with great moral integrity, he considered honesty to be the essential requirement for a scientist. He was especially low key and modest and was considered a quiet man of few words, who eschewed any behavior remotely resembling self-promotion. He had an extremely strong willpower and persistence when encountering difficulties. He was also a perfectionist, and some thought of him as being too critical. However, in the eyes of his students, he was kind and generous, as well as strict. No matter how busy he was, he was always willing to spend his time with students as well as visitors, no matter whether they were senior scientists or novices.

Professor Yu will be missed dearly by all of us. His impact on the fields of turbulence and transport in magnetically confined plasmas, nonlinear dynamics of laboratory plasmas, and high-temperature plasma diagnostics will continue to be felt for many years.