Plasma physics comes under scrutiny in new breed of tokamak.
The world's first fully superconducting tokamak is soon to produce a discharge of ionized gas or plasma.
If all goes as planned, China's Experimental Advanced Superconducting Tokamak (EAST) project will make its first plasma in the next few weeks.
EAST uses superconducting coils to create a magnetic field that confines plasma inside a doughnut-shaped vessel known as a tokamak. The behaviour of the plasma should shed light on the potential of nuclear fusion as an energy source.
Conventional experimental fusion machines use copper coils, or a combination of copper and superconducting coils, to trap the hot plasma. But copper coils heat up and need to be cooled down regularly, thus limiting operating time. EAST has only superconducting coils so it can be operated continuously.
The US$25-million machine sets the stage for the multibillion-dollar ITER fusion experiment that is to be built in France; ITER, due to start operations in 2016, is similarly designed to be all-superconducting.
“We'll need new energy resources for a long-term period, and fusion will be one of them,” says Peide Weng, deputy manager and chief engineer of the EAST project at the Institute of Plasma Physics of the Chinese Academy of Sciences. “For commercial use, it should be superconducting because it will need continuous operation.”
China approved the machine in 1998, as part of a push towards new energy sources. Construction then began in 2000 in Hefei, in southern China. The 150-member EAST team imported some material and components, but designed and fabricated the bulk of the equipment on its own.
EAST is only one-tenth the volume of Japan's JT-60 tokamak, and one-hundredth the expected volume of ITER. It won't produce fusion power, and is designed to study advanced tokamak physics. The first plasma, created from heated hydrogen gas, will probably last for only a few seconds. Still, “it will be a very important step forward,” says Toshihide Tsunematsu, director-general of the Naka Fusion Institute of the Japan Atomic Energy Agency, who visited EAST a few weeks ago. The agency owns the JT-60 tokamak.
Eventually, the EAST team aims to hold a plasma for study for as long as 1,000 seconds. In other tokamaks plasmas last for only a few tens of seconds.
South Korea is currently developing a tokamak similar to EAST, called the Korean Superconducting Tokamak Reactor (KSTAR), whose construction is expected to be completed at the end of 2007. Japan also plans to upgrade its JT-60 machine to make it fully superconducting in a few years.
International physicists praise what China has accomplished so far. In 2003, 25 physicists visited EAST as part of its international advisory committee.
“Everybody came away very impressed,” says Dale Meade, a physicist with the Princeton Plasma Physics Laboratory in Princeton, New Jersey, and a member of the group. The committee plans to hold another meeting in October, when China hosts a conference of the International Atomic Energy Agency.
In the meantime, the EAST researchers have plenty to work on, says Tsunematsu. They will have to improve key technologies, such as a device to heat the plasma, and be able to effectively control high-temperature plasma for a long period of time. “China will face a real challenge,” he says.
With additional reporting by Geoff Brumfiel
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Academia Sinica, Institute of Plasma Physics
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Fuyuno, I. China set to make fusion history. Nature 442, 853 (2006). https://doi.org/10.1038/442853a
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