Emission of Photoneutrons form ²⁹Si at Photon Energies up to 13 MeV

Abstract

The photoneutron cross section of ²⁹Si has been studied by irradiating silicic anhydride, enriched in ²⁹Si, in the X-ray beam of a 15 MeV linear electron accelerator. The photoneutron cross-section shows maxima at about 10.6 and 12.2 MeV. The integrated cross-section form the threshold to 13.0 MeV is 11 MeV·mb. The angular distribution of photoneutrons has also been measured to fit with a curve of the form a+bsin²θ. The values for b⁄a are found to be 2.1±1.0 and 3.9±0.8 for measurements with bremsstrahlung having maximum energies of 11.7 and 12.9 MeV, respectively. The significant features of the photoneutron cross-section and the angular distribution are discussed and compared with theoretical calculations for the E 1 transition of a valence neutron.