Secondary electron emission properties of conducting surfaces for use in multistage depressed collectors

The efficiency of depressed collectors can be enhanced by the use of low secondary yield electrodes. An investigation of a number of materials, considered likely prospects to accomplish this objective, was initiated. The materials studied were beryllium, soot, pyrolytic graphite, copper, titanium carbide and tantalum. Secondary electron emission measurements were made using an Auger spectrometer so that the chemical constituents on the surface could be determined in conjunction with the secondary measurements. The results showed that pyrolytic graphite, roughened by sputter etching, has the best potential for use as an electrode surface in depressed collectors.