Wang Ganchang

Wang Ganchang a Chinese nuclear physicist of the twentieth century (1907-1998) who was a pioneer of experimental nuclear physics in China, discovered the anti-sigma minus particle and made fundamental contributions to the country's nuclear weapons programme.

Early Life and Education

Wang Ganchang was born on 28 May 1907 in Changshu, in Jiangsu province. He grew up in a scholarly family and was educated in the modern schools that were spreading through the country, showing an early gift for mathematics and the physical sciences. He entered Tsinghua University, where he studied physics under Ye Qisun and became part of the first generation trained in the subject in China.

He graduated in 1929 and remained at Tsinghua as a teaching assistant, working on the photoelectric effect and on the properties of matter. His ability came to the attention of his teachers, who arranged for him to continue his studies abroad. In 1930 he travelled to Germany to work at the University of Berlin.

In Berlin he studied under Lise Meitner, one of the leading nuclear physicists of the day, and worked in a laboratory at the frontier of the new field of nuclear physics. He completed his doctorate in 1934 with research on the beta decay of radioactive substances and on the interaction of radiation with matter.

Discovery of the Anti-Sigma Minus Particle

Wang Ganchang's most celebrated discovery came in 1959, when he led a team at the Joint Institute for Nuclear Research at Dubna in the Soviet Union. Using a liquid hydrogen bubble chamber exposed to a beam of high-energy particles, the group identified a new particle, the anti-sigma-minus hyperon, an antiparticle partner to a particle already known.

The finding was significant for the understanding of the symmetry between matter and antimatter and for the classification of the strongly interacting particles. It supplied evidence for the emerging schemes that ordered the hadrons and strengthened the case for the deeper theory that would eventually be formulated as the quark model.

The discovery was widely reported and brought Wang international recognition. It demonstrated that Chinese physicists could compete at the highest level in experimental particle physics, and it was based on the analysis of thousands of bubble-chamber photographs, a task that required systematic care as much as theoretical insight.

Foundations of Chinese Nuclear Research

After returning to China before the Second World War, Wang Ganchang taught and carried out research at several universities and helped to establish the study of nuclear physics despite the poverty of the equipment available. He worked on cosmic rays, on the detection of particles and on the measurement of nuclear quantities, and he trained students who became leaders in the field.

He was one of the founders of the modern discipline in China, arguing for the construction of accelerators and the creation of research institutes. He took part in the planning of the country's scientific development and in the early investigations that preceded the nuclear weapons programme, and he helped to design and construct the detection instruments that the work required.

His breadth, from the design of experiments to the interpretation of data, made him a central figure in the transition from a small academic community to a national research enterprise. He was respected for his judgement and for his willingness to work on practical problems when the country needed them solved.

The Weapons Programme and Later Work

In the 1960s Wang Ganchang was drawn into the nuclear weapons programme, where he contributed to the design and testing of the first Chinese atomic bomb. He took part in the preparations for the test at Lop Nur in October 1964 and in the measurement and analysis of its results, work that consolidated the success of the first device.

He helped to organise the diagnostics of nuclear explosions, devising methods to measure the yield and the behaviour of the detonation, and he contributed to the effort that led to the hydrogen bomb test of 1967. His knowledge of nuclear instrumentation was indispensable to a programme that had to build its measurement techniques from scratch.

In later years he supported the development of nuclear energy and of lasers, and he took part in the formulation of the national high-technology programme of 1986, lending his authority to the case for investment in advanced research. He continued to write and to advise until late in life.

Influence and Legacy

Wang Ganchang was elected to the Chinese Academy of Sciences and received the two bombs and one satellite meritorious medal for his contributions to national defence. He was honoured as one of the key figures in the establishment of experimental nuclear physics in China and as the discoverer of a fundamental particle.

His career bridged two worlds, the international science of the 1930s and the national effort of the postwar decades, and in both he worked at the highest level. The students and institutions he supported carried his methods into later generations, and the particle he helped to discover remains part of the standard picture of the subatomic world.

He died on 12 December 1998 in Beijing at the age of ninety-one. He is remembered as a scientist of wide interests and great technical skill, whose discoveries advanced the understanding of matter and whose service helped to give his country a place in modern physics.

See also

• Zhu Guangya
• Anti-sigma minus particle
• Joint Institute for Nuclear Research
• Two bombs and one satellite