Ion Energy Measurements in a Direct Wave-Drive Thruster
An experiment designed to demonstrate ion acceleration in a Direct Wave-Drive Thruster (DWDT) was constructed. A DWDT is a new propulsion concept that relies on waves to transfer momentum directly to a plasma without electrodes. In order to demonstrate the existence of accelerated ions, the ion energy distribution function in the plume was measured with a retarding potential analyzer (RPA) for varying powers delivered to the wave launching antenna. For antenna powers up to 700 W, the number of higher energy ions in the distribution function increases, which is consistent with ion acceleration. In order to rule out any spurious effects from the RPA, an insulating plate was placed in front of the RPA, which reduced the number high energy ions in the measured distribution functions. The measured increase in the high energy tail of the ion energy distribution function provides evidence for part of a proof-of-concept experiment of the DWDT.