Production and Effects of Low-Energy Electrons in Helium

Three low-energy electron guns have been constructed and tested, using the elastic scattering resonance in helium to determine the energy resolution of the electron beam. Additional threshold excitation measurements have been made in an attempt to produce, in one laboratory, a comprehensive study involving the effectiveness of microampere-level, low-energy beams for producing metastable atoms and optically observable allowed transitions. The resulting data are presented. In addition, a second elastic resonance in helium has been observed, and the two resonances have been determined to be at 19.52±{}0.1 and 20.30±{}0.1 V.