Experimental Studies of the Characteristics of Photocatodes of the Ultraviolet Range of the Spectrum

Abstract

Photoemission cells with high sensitivity to photons in the ultraviolet (UV) range of the spectrum have a wide range of practical applications in accelerator technology and generators of ultrashort electromagnetic pulses in the microwave range. The potential benefits of using UV photocathodes in these areas of technology are determined by such a combination of their properties as high electrical strength and high quantum efficiency. The report presents the results of experimental studies of the characteristics of photocathodes based on magnesium-barium (Mg-Ba) alloys and cesium iodide (CsJ). Photocathodes were fabricated by thermal vacuum sputtering on polished stainless steel substrates. It is shown that the dielectric strength of vacuum gaps with UV cathodes is significantly higher than with antimony-cesium cathodes in the visible range of the spectrum (for CsJ cathodes – 2.5 times, for Mg-Ba cathodes – more than three times). The quantum efficiency of Mg-Ba cathodes is ~1% at a wavelength of 247 nm, and that of CsJ cathodes is 7.5% at a wavelength of 196 nm. The results of studies of the dynamics of a decrease in the quantum efficiency of photocathodes under repetitively pulsed irradiation with laser pulses with a fluence 6 μJ/cm2. The characteristics of photocathodes are compared from the point of view of their practical applications.