Suppression of electron emission from large surface area stainless steel electrodes

Surface treatment processes for 304L and 316L stainless steel have been tested for the electron emission suppression over large area planar surfaces. Testing was performed on 17-cm-diameter electrodes with 3 to 4 mm gaps. The treatment processes for the electrodes were solvent cleaned 16 micro-inch rms surface machining, chemical polishing, hydrogen vacuum furnace firing, and gold coating. Tests were made with a 60 to 160 kV, 200 ns flat topped voltage pulse and 150 to 260 kV, 160-ns-FWHM, waveform with 1-cos(ωt) shape. Gap closure and cathode plasma area expansion rates are determined from a Child-Langmuir model. It was noted that the initial 1-μm-roughness 304L SS gave similar or perhaps slightly better results than the other preparations. Results from each of the treatment processes are discussed.