Observation and measurement of temperature rise and distribution on GaAs photo-cathode wafer with a 532 nm drive laser and a thermal imaging camera

Significant temperature rise and gradient are observed from a GaAs photo-cathode wafer irradiated at various power density levels with over 20W laser power at 532 nm wavelength. The laser power absorption and dissipated thermal distribution are measured. The result shows a clear indication that proper removal of laser induced heat from the cathode needs to be considered seriously when designing a high average current or low quantum efficiency photo-cathode electron gun. The measurement method presented here provides a useful way to obtain information about both temperature and thermal profiles and also applies to cathode heating study with other heating devices such as electrical heaters. (C) 2010 Elsevier B.V. All rights reserved.