| This experiment measured the polarization and quantum efficiency as a function of wavelength for the chalcopyrite semiconductor Zn(Ge{dollar}rmsb{lcub}0.7{rcub}Sisb{lcub}0.3{rcub})Assb2.{dollar} Also, the onset of space charge growth of a 100 keV electron beam passing through the Illinois/CEBAF polarized electron injection system was studied by measuring the beam emittance as a function of current. Finally, the thermal properties of GaAs were investigated by measuring the beam emittance as functions of the excitation laser wavelength and the laser spot size.; The experiments were performed at the University of Illinois Nuclear Physics Laboratory using a 100 keV photoemission polarized electron gun, a electron spin manipulation system of a novel design, a Mott polarimeter, and an emittance measuring system. The design and performance of the entire system is described.; The maximum polarization of Zn(Ge{dollar}rm sb{lcub}0.7{rcub}Sisb{lcub}0.3{rcub})Assb2{dollar} was measured to be {dollar}sim{dollar}19%, much lower than the expected 100%. Also, the expected transition of the polarization through zero was not observed. The beam emittance as a function of current was measured and the onset of space charge effects was found to be {dollar}sim{dollar}0.5 mA, much lower than predicted by the electron gun design program scEGUN. Finally, the effective transverse thermal energy of the electrons emitted from GaAs at 100 keV as a function of excitation wavelength was measured by a new method for low beam currents. The electron thermal energy for wavelengths between 840 and 633 nm was found to be {dollar}sim{dollar}33 meV, a factor of 3 lower than for a thermionic electron gun. It was also found to increase sharply for photon wavelengths less than 633 nm. |
