  Photoelectron emission measurements have been performed using a
room-temperature 14 GHz ECR ion source. It is shown that the photoelectron
emission from Al, Cu, and stainless steel (SAE 304) surfaces, which are common
plasma chamber materials, is predominantly caused by radiation emitted from
plasma with energies between 8 eV and 1 keV. Characteristic X-ray emission and
bremsstrahlung from plasma have a negligible contribution to the photoelectron
emission. It is estimated from the measured data that the maximum conceivable
photoelectron flux from plasma chamber walls is on the order of 10 % of the
estimated total electron losses from the plasma.
