Experimental determination of effective resonance energies for the (n,γ) reactions of 71Ga, 75As, 164Dy, 170Er by the cadmium ratio method

Abstract

The effective resonance energy E ¯ r -values for the (n, γ) reactions of 71Ga, 75As, 164Dy, 170Er were determined by the cadmium ratio method using dual monitor ( 55Mn– 98Mo) having favorable resonance properties. The powder samples with and without a 1 mm thick Cd cylindrical box were irradiated in an isotropic neutron field obtained from three 241Am–Be neutron sources. The induced activities were measured with a 120.8% relative efficient p-type Ge detector. The necessary correction factors for thermal neutron self-shielding ( G th) and resonance neutron self-shielding ( G epi) effects were taken into account. Thus, the experimentally determined E ¯ r -values were 174 ± 36 eV for 71Ga, 112 ± 23 eV for 75As, 225 ± 47 eV for 164Dy and 129 ± 27 eV for 170Er, respectively. The present experimental results for the E ¯ r -values were also theoretically calculated from the newest resonance data. Since the experimentally determined E ¯ r -values for the 71Ga, 75As, 164Dy and 170Er isotopes are not available in literature, the present experimental results are compared only with the present and earlier calculated ones. It is found that there are still large discrepancies (within range of 3–15%) between the experimentally determined E ¯ r -values and the calculated ones obtained by recent resonance data for the above isotopes. A wide variation of the available E ¯ r -values implies the need for the new experimental determinations of E ¯ r -values for other isotopes, especially used in k 0 standardization studies.