Particle and energy transport in the plasma scrape-off zone and its impact on limiter design

The design of limiters for fusion devices depends critically on the transport properties of the plasma edge. Recent data from Langmuir Probe experiments and calorimeter probe experiments on the Poloidal Divertor Experiment (PDX) have provided information about the transport of particles and energy in the edge region of a plasma. These data have been used as input to a simple one-dimensional model in which the particle and thermal diffusion coefficients are permitted to be functions of the density and temperature. The transport coefficients deduced from the data are then applied to the cases of the TFTR device and a device like FED/INTOR to predict the optimum design for limiters or pump limiters. The results indicate the optimum limiter should have a concave shape when viewed from the plasma. The effect of the uncertainties in the deduced coefficients on the optimum design performance are also discussed