Effective Cadmium Cutoff Energies for Non-1/VDetectors

Abstract

Effective cadmium cutoff energies were calculated for 239Pu, 235U, 115In, Au, 119Ir and 176Lu as a function of the cadmium filter thickness, the mast probable energy of the Maxwellian flux and the epi-thermal index. An infinite slab geometry and isotropic flux were assumed in the calculations. The calculated values of the cutoff energies are compared with those for 1/V detector, and are related to the resonance energies near the cutoff energy. If the resonance energy is lower than that of the 1/V detector, and the neutron spectrum and filter are same, the cutoff energy is lower than that of the 1/V detector. Such cases include 235U and 176Lu with thin filter, 191Ir with thick filter, and 239Pu with either thin or thick filter. If the resonance energy is higher than the E c of the 1/V detector, the cutoff energy is higher, such cases being 191Ir with thin filter, 176Lu with thick filter and 115In with either thin or thick filter. And if the resonance energy is very much higher than the E c of the 1/V detec...