Minimizing Surface Plasmas in High Power Microwave Sources.

摘要

This final technical report reviews the research activities during the period of this grant, emphasizing the final year. The effects of surface roughness on secondary electron emission were investigated for copper. The surface of copper samples were modified using a high-power Nd-YAG laser, where the degree of surface modification depended on the duration and intensity of the laser exposure. Four different levels of modification were tested, in addition to the unmodified sample. Minor modification resulted in the biggest effect, significantly reducing the secondary electron emission. However, this effect only holds true for very low electron dose, where dose is the incident charge per unit area. For higher dose levels those commensurate with technical materials in applied situations there was negligible effect of surface roughness on secondary electron emission. The data set presented here seeks to quantify the effect of surface roughness with further gradations than is accounted for in the semi-empirical formulae in the literature.