抄録
Since tokamak fusion experimental reactors try to sustain 100-200 second D-T burning, helium exhaust from plasma core is one of the major issues of the tokamak reactors. There have been proposed two major concepts about helium exhaust from plasma. They are concepts of magnetic divertor and pumped limiter. In both cases, a very large pumping system is required for the helium and fuel pumping.
The cryosorption pump with 4.2K panels is considered to be a prime candidate for these applications. When molecular sieves are used as the adsorbent, it has been recognized that the pump may not be able to accommodate helium-hydrogen isotopes mixtures, because condensed deuterium and tritium will block the adsorbent surface and prevent helium pumping. This means that the cryosorption panels (4.2K) for helium will be surrounded by two chevrons, one at 77K and the other at 4.2K. Recently, cryopumping has intensively studied in the TSTA project in the United States. It has been shown that cryosorption by charcoal and cryotrapping by argon condensed layers will appear to work successfully with tokamak reactors.
In the cryopumps, it is necessary to recover the pumped gases as quickly as possible in order to achieve low inventories of tritium. The regencration cycle will be determined by considering several items which include tritium inventory and safety problems.
