Thick target photon yields and angular distributions for the 19F(p,αγ) 16O source reaction at incident proton energies between 1.5 and 4.0 MeV

Abstract

The absolute thick target yield of 6.129, 6.917 and 7.116 MeV γ-rays produced from the 19F(p,αγ) 16O source reaction has been measured for incident proton energies between 1.5 and 4.0 MeV. The angular distributions of the respective γ-lines have been determined for incident proton energies of 2.0 and 3.0 MeV. The experiments were performed at the 4.5 MV Tandem Van der Graaff accelerator at the Ohio University Edwards Accelerator Laboratory in Athens, Ohio, using a thick CaF 2 target and a 7.62 cm×7.62 cm Na(I) scintillation detector. The Monte Carlo code MCNP was used to calculate detector response functions for the three individual γ-rays. A least-squares fit of these functions to a selected region in the pulse height spectrum was carried out to determine the relative intensities of these γ-rays. The uncertainty in the fluence determination is based on the χ 2 of the fit, the uncertainty in the response functions, the statistics of the data, and the uncertainty in the recording of the proton charge. A maximum photon yield of 1.316×10 7 γ/μC/sr (at 90°) was determined for the sum of these three γ-rays at the highest incident proton energy of 4.0 MeV. The contribution of the individual lines to the total photon yield depends strongly on the incident proton energy. The angular distributions are isotropic to within 15%.