Reduction of neutral particles refluxing into a plasma by use of a honeycomb wall

Abstract
The feasibility of honeycombing the first wall of a fusion reactor was investigated with regard to refluxing of neutral particles back into the plasma. The effect of the length-to-diameter ratio (L/D) of the honeycomb cell on the energy and angular distribution of refluxed particles was studied as well as the ratio of the refluxing from honeycomb and smooth walls. Honeycombing the wall with an L/D = 1.5 cell was found to typically reduce the number of refluxed particles by a factor of 10 compared to a smooth wall. In addition, the total energy refluxing was reduced to approximately 6 percent of the comparable smooth wall value. The effect of the honeycomb on the emerging angular distribution of refluxed particles was minimal in the optimum honeycomb configuration (L/D from 1.0 to 2.0). (auth)