The spherical condenser as a high transmission particle spectrometer

Abstract

Abstract A spectrometer embodying the design features described in parts I and II of this paper has been constructed with an angle χ of one radian. The inverse square electric field between the plates of a spherical condenser focuses charged particles leaving a point (part I) or disk (part II) source located on the inner sphere. Particles leave the region of electric field through an annular slit at the focal position and are detected with a Faraday cup and vibrating reed electrometer. Energy resolution and transmission have been tested with an isotropic electron gun and with Auger electrons and are 6.25% and 25%, respectively, between 50 eV and 32 keV in good agreement with theoretical expectations. The spectrometer is useful down to 0.5 eV although calibration has not been made as precisely. A beta ray and secondary electron spectrum of Cu64 negatrons and positrons has been obtained from a cavity source of copper which approximates an infinite, isotropic, homogeneous, radioactive medium. Multicurie sources were used and observed currents were of the order of 10−13 ampere over an energy range from 0.5 eV to 40 keV.