Spectrum of 198Au Beta Rays in Gold

Abstract

The Keplertron, a spherical electrostatic electron spectrometer, was used to obtain he slowing-down spectrum of beta rays and their secondary electrons in gold. Two gold discs 0.82 cm in diameter and 0.025 cm thick were irradiated in the LITR at ORNL to about 25 c. One disc was placed tangent to the inner Keplertron sphere and the other parallel and coaxial at a distance of 0.24 cm. The cylindrical cavity thus formed approximated a “black body” source with the electrons emerging from the open cylindrical sides being representative of flux in an infinite, isotropic, uniformly irradiated medium. Electron flux measurements were made from 1 eV to 63 keV. The spectrum,. corrected for surface barrier transmission and spurious spectrometer response due to scattering, was compared on an absolute basis with the simplified continuous slowing-down model of SPENCER and ATTIX. Flux varies from 2.9 × 10−8 electrons cm−2 eV−1 per primary beta ray cm−3 at 63 keV to 1.2 × 10−4 at 11 eV above the bottom of the conduction band.