Measurement of the Se80(γ,n) reaction with linearly polarized γ rays

Abstract

This paper reports the results of the first measurements of the differential cross section of the 80 Se(γ, n) 79 Se reaction with a linearly polarized gamma-ray (γ-ray) beam. The cross section was measured at three incident γ-ray beam energies: 15.6, 15.8, and 16.0 MeV, with a beam energy spread of 3.0% full width at half maximum (FWHM). The differential cross section for the excitation spectrum in 79 Se was measured at two scattering angles in the plane of the beam polarization: θ = 90 • and 135 • , and at one angle in the plane perpendicular to the plane of polarization: θ = 90 • . The total photoneutron cross sections determined from these data are between 0.8 and 1.3 standard deviations smaller than previously published results. The excitation spectra measured in this work were fit with a Hauser-Feshbach model. Better fits to the data were obtained with a constanttemperature formulation of the nuclear level density (NLD) than with a Fermi-gas NLD model. The parameters for the constant-temperature NLD model obtained in this work are consistent with those obtained for medium-mass nuclei in previous studies. 0 © ¦ ¦ © 0 © ¦ ¦ © dσ/dΩ/dE (µb/sr/keV) FIG. 12. (Color online) Measured angle-correlated differential cross sections and asymmetries for the 80 Se(γ,n) reaction at incident γ-ray beam energy Eγ = 15.8 MeV. The data and curves are as described in Fig. 11.

Photonuclear reactions on stable isotopes of selenium at bremsstrahlung end-point energies of 10−23 MeV

“…In [6], the same method was used to measure the cross sections for the reactions 78 Se(γ, n) 77m Se, 80 Se(γ, n) 79m Se and 82 Se(γ, n) 81m Se. In [16,17,18,19,20], on a beam of quasimonoenergetic photons obtained as a result of Compton backscattering, the cross sections for reactions σ(γ, n) were measured in the energy range from threshold to 14.6 MeV on 76,77,78,80 Se isotopes. In [15] on a beam of quasi-monoenergetic photons, the reaction cross section σ(γ, 2n) and the sum of the reaction cross sections σ(γ, n) + σ(γ, 1n1p) were measured in the energy range from threshold to 30 MeV on 76,78,80,82 Se isotopes.…”

“…The development of both nuclear physics research and applications based on photonuclear reactions is closely related to the development of attendant photon sources and measuring instruments. Photoneutron reactions on isotopes of natural mixture of selenium have been well studied using bremsstrahlung γ-radiation [5][6][7][8][9][10][11][12][13][14], positron annihilation in flight [15] and Compton backscattering of laser beam photons [16][17][18][19][20]. Cross sections of photonuclear reactions at selenium isotopes in the region of energy giant dipole resonance were measured in several works.…”