Dependence of the photoelectron collection efficiency in noble gases on the incident VUV photon energy

A detailed Monte Carlo simulation is used to investigate the backscattering of the photoelectrons emitted from a CsI photocathode into Xe, Ar, and Ne. The transmission efficiencies for the case of a 11 nm thick reflective CsI photocathode are presented, for incident photon energies E_ph in the range 6.7 to 9.8 eV (185-127 nm) and density-reduced applied electric fields E/N<40 Td. In addition to the collection effect of increasing E/N, and to a dependence on the gas nature, a significant dependence on incident photon energy is also found, showing that in the ranges investigated for E/N and E_ph the probability of transmission is reduced with increasing E_ph.