Gamma-Rays from Light Elements Due to Proton Bombardment

Abstract

With the high potential electrostatic generator recently constructed at this laboratory a survey of a number of elements has been made in a search for gamma-ray emission due to proton bombardment. Six of the elements examined gave gamma-rays of sufficient intensity to permit accurate measurement. These six elements are Li, Be, B, F, Na and Al. Their gamma-ray yield was studied as a function of proton energy, or generator voltage, starting with the minimum potential at which the yield was easily measurable. In the region of fairly low potentials the six elements studied gave evidence for resonance excitation of gamma-radiation and at high potentials each of the six elements gave a gamma-ray intensity which increased nearly exponentially with voltage up to the maximum voltage obtainable from the generator (approximately 2 Mev). The measurements were made using a Lauritsen electroscope, and therefore they give the intensity in arbitrary units which depend on the hardness of the radiation and the geometry of the apparatus. The other elements which were bombarded are C, O, Si, K, Ca, Ni, Cu, Zn, Mo, Pt, Pb. Gamma-radiation from these elements was weak and the observed intensities may have been largely due to contaminants.