AbstractThe International Thermonuclear Experimental Reactor (ITER) will use an advanced, high-velocity pellet injection system to achieve and maintain ignited plasmas. Three pellet injectors are proposed. For ramp-up to ignition, a highly reliable, moderate-velocity (1- to 1.5-km/s) single-stage pneumatic injector and a high-velocity (1.5- to 5-km/s) two-stage pneumatic pellet injector that uses frozen hydrogenic pellets encased in sabots will be used. For the steady-state burn phase, a continuous, single-stage pneumatic injector is proposed; this injector will provide a flexible fueling source beyond the edge region to aid in decoupling the edge region (whose parameters are constrained by divertor requirements) from the high-temperature burning plasma. Because pellet fueling is more efficient than gas injection, it may be possible to use pellet fueling to provide all of the tritium and a portion of the deuterium needed to sustain the fusion reaction and to use deuterium gas injection to provide the required edge densities for optimum divertor conditions. In addition to decreasing the tritium throughput and raising the tritium burn fraction, this mode of operation allows a deuterium-rich boundary layer gas at the edge, which could significantly lower tritium inventories in plasma-facing components. All three pellet injectors are designed for operation with tritium feed gas. Issues such as performance, neutron activation of injector components, maintenance, design of the pellet injection vacuum line, gas loads to the reprocessing system, and equipment layout are discussed. Results and plans for supporting research and development in the areas of tritium pellet fabrication, continuous extruders, and high-velocity, repetitive two-stage pneumatic injectors are presented.
Particle fueling experiments with a series of pellets in LHD