DIVERTOR PUMPING AND OTHER REACTOR APPLICATION ISSUES FOR H-MODE

We summarize results from DIII-D in regard to issues for reactor appli cation of H-mode. Recently, DIII-D has begun to operate a cryopump (D2 pumping speed = 31,000 l/s at a pressure of 2 mTorr). Initial results are very favorable for density control in H-mode. The plasma density could be reduced by 50%. Energy confinement is unchanged so the temper ature rises in proportion to the density drop. Ability to access these less collisional plasmas in H-mode is favorable to current drive appl ication. With the all-graphite wall, impurity accumulation has been el iminated. The exceedingly good confinement of VH-mode offers the possi bility of retaining good confinement while radiating copious power fro m the plasma edge using injected noble gas impurities.