Status of TFTR with Ohmic heating and neutral beam injection

Abstract

The main body of the paper addresses the current status of the Tokamak Fusion Test Reactor (TFTR) as of December 1984, with emphasis on the vacuum and surface physics aspects of its operation. A brief review is given of the first paper on the vacuum aspects of controlled fusion research to be presented to a Symposium of the American Vacuum Society. This was given at the Fifth Symposium in October 1958 by the author of this paper. A comparison is made of the devices of that time with TFTR. The vacuum vessel diameter has gone from 2 in. to 7 ft., the plasma durations from 2 ms to many seconds, and the energy confinement time has increased by a factor of 1000 to 0.4 s. TFTR plasmas have reached densities of 4×1013 cm−3 with electron and ion temperatures of 3 keV. Very preliminary results, with the injection of only 2 MW of 50–70 keV neutral hydrogen into deuterium plasma, show the expected ion heating and increase in neutron flux. These experiments also show roughly a 30% reduction in the energy confinement time from that of plasmas with only Ohmic heating, as has been noted in other tokamaks. Attention is called to the continuing importance of impurity control in fusion devices.