The construction and spectral properties of a windowed helium microwave discharge lamp for application to studies in photoelectron spectroscopy are presented. The 584-A light flux passing a 1500-A thick aluminum window from a 10-mm i.d. discharge is in excess of 1 X 1013 photons/sec. These intensities permit fluxes of lO^-lO12 photons/sec in a PES source and are sufficient to produce photoelectron spectra of high resolution without spectral interference from impurity lines.