[en] We searched for a temperature dependence of the half-life (T_1/2) of ⁶⁴Cu embedded in natural copper. We did not observe any change in T_1/2 between room temperature and 12 K on the level of 0.25%. Some earlier studies had suggested an increased T_1/2 (by a few percent) for electron-capture and β^- decay dominated radioactive decays in a metallic environment at low temperature compared to measurements at room temperature. Our result is in excellent agreement with the recommended T_1/2 value for ⁶⁴Cu and with very recent studies on ¹⁹⁸Au

[en] The "4"0Ar(n, γ)"4"1Ar neutron capture cross section has been measured between 0.4 and 14.8 MeV neutron energy using the activation technique. The data are important for estimating backgrounds in argon-based neutrino and dark-matter detectors and in the neutrino-less double-beta decay search GERDA, which uses liquid argon as cooling and shielding medium. For the first time the "4"0Ar(n, γ)"4"1Ar cross section has been measured for neutron energies above 1 MeV. Our results are compared to the evaluation ENDF/B-VII.1 and the calculated prediction TENDL-2013. The latter agrees very well with the present results

[en] Partial cross section measurements were carried out on ¹³⁶Xe at Triangle Universities Nuclear Laboratory (TUNL) using 5 MeV monoenergetic neutrons. These results are important for estimating potential neutron-induced backgrounds in the nEXO and KamLAND2-Zen neutrinoless double-β decay searches that use highly enriched ¹³⁶Xe. Pulsed neutron beams were produced via the ²H(d, n)³He reaction and the deexcitation γ-rays from ¹³⁶Xe were observed with two 60% relative efficiency HPGe detectors. (paper)

[en] We report on a set of neutron-induced reaction measurements on ²⁴¹Am which are important for nuclear forensics and advanced nuclear reactor design. Neutron capture measurements have been performed on the DANCE detector array at the Los Alamos Neutron Scattering CEnter (LANSCE). In general, good agreement is found with the most recent data evaluations up to an incident neutron energy of ∼ 300 keV where background limits the measurement. Using mono-energetic neutrons produced in the ²H(d,n)³He reaction at Triangle University Nuclear Laboratory (TUNL), we have measured the ²⁴¹Am(n,2n) excitation function from threshold (6.7 MeV) to 14.5 MeV using the activation method. Good agreement is found with previous measurements, with the exception of the three data points reported by Perdikakis et al. around 11 MeV, where we obtain a much lower cross section that is more consistent with theoretical estimates

[en] Cross section measurements for the neutron induced reactions on GaAs have been carried out at ten different neutron energies from 7.5 to 15 MeV, using the activation technique. The monoenergetic neutron beams were produced via the ²H(d,n)³He reaction, known for it's high neutron yield in the chosen energy regime. GaAs samples were activated along with the Au and Al monitor foils, for estimating the incident neutron flux. The induced activity was measured using high resolution γ-ray spectroscopy. Five reaction channels viz., ⁶⁹Ga(n, 2n) Ga, ⁶⁹Ga(n,p)^69mZn, ⁷¹Ga(n,p)^71mZn, ⁷⁵As(n, 2n)⁷⁴As and ⁷⁵As(n,p)⁷⁵Ge, have been reported for the comprehensive cross section measurements. The results are compared with the existing literature data and the available evaluations. Statistical model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS and EMPIRE codes and are compared with the experimental values.

[en] We report on a set of neutron-induced reaction measurements on ²⁴¹Am which are important for nuclear forensics and advanced nuclear reactor design. Neutron capture measurements have been performed on the DANCE detector array at the Los Alamos Neutron Scattering Center (LANSCE). In general, good agreement is found with the most recent data evaluations up to an incident neutron energy of about 300 keV where background limits the measurement. Using mono-energetic neutrons produced in the ²H(d,n)³He reaction at the Triangle Universities Nuclear Laboratory (TUNL), we have measured the ²⁴¹Am(n,2n) excitation function from 7.6 to 14.5 MeV using the activation method. Good agreement is found with previous measurements, with the exception of the three data points reported by Perdikakis et al. around 11 MeV, where we obtain a much lower cross section that is more consistent with theoretical estimates. (authors)

[en] Cross-section measurements for neutron-induced reactions on GaAs have been carried out at twelve different neutron energies from 7.5 to 15 MeV using the activation technique. The monoenergetic neutron beams were produced via the ²H(d,n)³He reaction. GaAs samples were activated along with Au and Al monitor foils to determine the incident neutron flux. The activities induced by the reaction products were measured using high-resolution γ-ray spectroscopy. Cross sections for five reaction channels, viz., ⁶⁹Ga(n,2n)⁶⁸Ga, ⁶⁹Ga(n,p)⁶⁹Zn^m, ⁷¹Ga(n,p)⁷¹Zn^m, ⁷⁵As(n,2n)⁷⁴As, and ⁷⁵As(n,p)⁷⁵Ge, are reported. The results are compared with the previous measurements and available data evaluations. Statistical-model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS and the COH3 codes and are compared with the experimental results.

[en] The (n,2n) cross section of the radioactive isotope ²⁴¹Am (T_1/2=432.6 y) has been measured in the incident neutron energy range from 7.6 to 14.5 MeV in steps of a few MeV using the activation technique. Monoenergetic neutron beams were produced via the ²H(d,n)³He reaction by bombarding a pressurized deuterium gas cell with an energetic deuteron beam at the TUNL 10-MV Van de Graaff accelerator facility. The induced γ-ray activity of ²⁴⁰Am was measured with high-resolution HPGe detectors. The cross section was determined relative to Al, Ni, and Au neutron activation monitor foils, measured in the same geometry. Good agreement is obtained with previous measurements at around 9 and 14 MeV, whereas for a large discrepancy is observed when our data are compared to those reported by Perdikakis et al. near 11 MeV. Very good agreement is found with the END-B/VII evaluation, whereas the JENDL-3.3 evaluation is in fair agreement with our data

[en] Neutron elastic-scattering angular distributions were measured at beam energies of 11.9 and 16.9 MeV on ^40,48Ca targets. These data plus other elastic-scattering measurements, total and reaction cross-sections measurements, (e,e^'p) data, and single-particle energies for magic and doubly magic nuclei have been analyzed in the dispersive optical-model (DOM), generating nucleon self-energies (optical-model potentials) that can be related, via the many-body Dyson equation, to spectroscopic factors and occupation probabilities. It is found that, for stable nuclei with N≥Z, the imaginary surface potential for protons exhibits a strong dependence on the neutron-proton asymmetry. This result leads to a more modest dependence of the spectroscopic factors on asymmetry. The measured data and the DOM analysis of all considered nuclei clearly demonstrate that the neutron imaginary surface potential displays very little dependence on the neutron-proton asymmetry for nuclei near stability (N≥Z).

[en] The low-lying structure of ₄₀⁹⁴Zr was studied with the (n,n^'γ) reaction, and a level scheme was established based on excitation function and γγ coincidence measurements. Branching ratios, multipole mixing ratios, and spin assignments were determined from angular distribution measurements. Lifetimes of levels up to 3.4 MeV were measured by the Doppler-shift attenuation method, and for many transitions the reduced transition probabilities were determined. In addition to the anomalous 2₂⁺ state, which has a larger B(E2;2₂⁺→0₁⁺) value than the B(E2;2₁⁺→0₁⁺), the experimental results revealed interesting and unusual properties of the low-lying states in ⁹⁴Zr. In a simple interpretation, the excited states are classified in two distinct categories, i.e., those populating the 2₂⁺ state and those decaying to the 2₁⁺ state