Cryopumping for fusion reactors

Abstract

Fusion reactors will exhaust large volumes of hydrogen species and helium, and cryopumps can satisfy the pumping needs. Two programs described here were undertaken to develop the high performance, continuous operation required. The capability of charcoal as a cryogenic sorbent was optimized and improved by use of specific charcoal types and grades, and by use of thermally conductive bonds for attaching the charcoal to the cryogenically cooled substrate. A 30% demonstrated pumping speed improvement is significant for a system in which the pump dimensions are measured in tens of square meters. An automatically controlled continuous duty cryopump system was developed, fabricated and demonstrated. The system pumps deuterium, and can be readily modified to pump helium by addition of a sorbent such as charcoal. This two-unit system has one unit being regenerated while the other unit is pumping. It is prototypical of a fusion reactor pump in which five units would be pumping for each unit that is being regenerated. Low tritium holdup is projected for an operational installation.