Forward and Backward Photoemission Yields from Metals at Various X-Ray Angles of Incidence.
Abstract
X-ray generated photoemission from thin metal foils backed by graphite was measured with radiation incident from the front and back sides at several angles. Irradiation was provided by a 100-kV x-ray tube with three different filters to harden the spectrum. The total 2 pi photoelectron emission current from a surface was measured. A biased grid retarded the low-energy secondary electrons that added only 10 to 30% to the current at zero grid bias. Investigated metals were: Mg, Al, Ti, Fe, Cu, Ag, Ta, Au, and Pb. The total emission from the graphite support only was measured. It was determined that the front-to-back ratio of emission currents at normal incidence ranged from about 1.9 for Al and Mg down to about 1.1 for Ta. The photoelectron yield was found to be G sub e micron(a) S sub e electrons/photon, where micron(a) and S sub e are the energy-dependent photon absorption cross section and computed electron mean path length in the emitter and G sub E is a constant that is assumed to be independent of photon energy in the range studied but which depends on the radiation angle of incidence. For the photon energy range of 20 to 70 keV, the measured emission current densities corresponded to the following average values for G sub E: 0.37 + or - 0.06 for C, 0.30 + or - 0.03 for Al, 0.21 + or - 0.02 for Cu and Ag, and 0.18 + or - 0.02 for Ta. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 16, 1975
- Accession Number
- ADA019135
Entities
People
- Kenneth W. Paschen
- Melvin J. Bernstein
Organizations
- The Aerospace Corporation