TOKAMAK FUSION TEST REACTOR D-T RESULTS

Temperatures, densities and confinement of deuterium plasmas confined in tokamaks have been achieved within the last decade that are approac hing those required for a D-T reactor. As a result, the unique phenome na present in a D-T reactor plasma (D-T plasma confinement, a confinem ent, a heating and possible alpha-driven instabilities) can now be stu died in the laboratory. Recent experiments on the Tokamak Fusion Test Reactor (TFTR) have been the first magnetic fusion experiments to stud y plasmas with reactor fuel concentrations of tritium. The injection o f about 20 MW of tritium and 14 MW of deuterium neutral beams into the TFTR produced a plasma with a T-to-D density ratio of about 1 and yie lding a maximum fusion power of about 9.2 MW. The fusion power density in the core of the plasma was about 1.8 MW m(-3), approximating that expected in a D-T fusion reactor. A TFTR plasma with a T-to-D density ratio of about 1 was found to have about 20% higher energy confinement time than a comparable D plasma, indicating a confinement scaling wit h average ion mass A tau(E) proportional to A(0.6). The core ion tempe rature increased from 30 to 37 keV owing to a 35% improvement of ion t hermal conductivity. Using the electron thermal conductivity from a co mparable deuterium plasma, about 50% of the electron temperature incre ase from 9 to 10.6 keV can be attributed to electron heating by the al pha particles. The approximately 5% loss of alpha particles, as observ ed on detectors near the bottom edge of the plasma, was consistent wit h classical first orbit loss without anomalous effects. Initial measur ements have been made of the confined high energy alpha particles and the resultant alpha ash density. At fusion power levels of 7.5 MW, flu ctuations at the toroidal Alfven eigen-mode frequency were observed by the fluctuation diagnostics. However, no additional a loss due to the fluctuations was observed. These D-T experiments will continue over a broader range of parameters and higher power levels.