A preliminary engineering design of a “Venetian blind” direct energy converter for fusion reactors

This is a very preliminary engineering design of a new direct energy conversion device for use in conjunction with a mirror fusion reactor. The device described reclaims the energy lost by the reactor through leakage of charged particles. Energy selection is accomplished through the angular dependence of transmisssion through a system of ribbon grids resembling a Venetian blind. In contrast to previously described converters in which the beam of ions from the reactor is expanded in a flat fan-like expander, the beam in this device is expanded in two directions in a conical expander. Problems of grid construction, radiation damage, grid heating, and vacuum pumping are discussed. A preliminary cost estimate shows that for a power handled of 1000 MW, the cost for the direct converter is $110 Million or $110 per kW of power into the direct converter. The efficiency is estimated to be 59% for a two-state collector and 65% for a four-stage collector. Further development of the basic concept could possibly raise the efficiency to as high as 75%. Optimized designs might increase the power handled by a factor of several without significantly increasing the unit cost, thus greatly lowering the cost/kW.