W.K. Dawson

Nuclear structure studies of phosphorous isotopes: (II). The 28Si(d, n)29P reaction

Abstract Angular distributions of the neutrons leading to states of 29P up to an excitation of 3.5 MeV were obtained using the 28Si(d, n)29P reaction for deuteron energies of 4 and 5 MeV. The angular distributions for the ground, first and second excited states of 29P were analysed using the distorted wave Born approximation. The experimental spectroscopic factors favour a Nilsson model description for the 29P nucleus. Evidence for spin dependent structure was seen in the angular distributions of neutrons leading to the 1.38 MeV ( J π = 3 2 + ) and 1.96 ( J π = 5 2 + ) MeV states of 29P.

The excited states of 10B

Abstract The reaction 9 Be(d, n) 10 B has been studied by time-of-flight techniques at bombarding energies of 3.0, 3.5 and 5.5 MeV. A total of 16 levels of 10 B was identified up to 7.5 MeV excitation, but no significant evidence was found for reported states at 5.18, 5.58, 6.40 and 6.77 MeV. The DWBA theory was used to interpret the angular distributions for l -values and spectroscopic factors, and plane wave theory was used in cases where the 10 B levels become unbound. The spectroscopic factors were found to depend sensitivity on optical parameter uncertainties and also on whether or not finite-range and non-local effects were included.

The 40Ca(d,n)41Sc reaction; neutron polarization and angular distribution measurements

Abstract The angular distributions and neutron polarizations have been measured for the reaction 40 Ca(d,n) 41 Sc at a deuteron bombarding energy of 6 MeV. The polarization measurements, from 0° to 120°, were made for neutron groups corresponding to the ground, 1.718 MeV and 2.415 MeV states in 41 Sc. Additional angular distribution measurements were made for neutron groups corresponding to the 2.096, 2.719 and 3.463 MeV states in 41 Sc. Good agreement is found between the observed and DWBA predicted neutron angular distributions. No satisfactory agreement between the experimental and calculated neutron polarizations is found for any reasonable choice of optical parameters.

The efficiency of a pilot U scintillator for neutrons in the energy range 55-225 MeV

Abstract The absolute efficiency for detection of neutrons in a Pilot U scintillator 76 mm long and 114 mm diameter has been measured at E n = 55, 71, 107, 110, 162 and 225 MeV. The results are in good agreement with the predictions of a Monte Carlo simulation of the detection process provided that the detection threshold is chosen appropriately.

The energy level structure of 154Sm from the (n, n′γ) reaction

Abstract Gamma rays from levels in 154 Sm between 921 and 1817 keV excitation were observed following neutron inelastic scattering at neutron energies ranging from 1.1 to 2.3 MeV. Level positions and decay mode information were obtained. Gamma-ray production cross sections were determined and then used to deduce neutron inelastic cross sections. The results were compared with the predictions of the compound nuclear statistical theory to establish level spins and parities.

A small sample method for investigation of the (n, n′γ) reaction☆

Abstract A technique has been developed which makes it possible to study (n, n′ γ ) experiments using very small scattering samples in a close geometry. Data are presented for a 3.147 g natural Fe target and a 6.960 g Sm 2 O 3 target enriched to 99.54% in 154 Sm. The results indicate that the method can yield useful results for samples of this size. To show that reliable yield curves can be obtained with the present technique, the excitation curve for the 847 keV γ ray from 56 Fe has been measured. Because of the close geometry, an unfolding routine was employed to account for the angular distribution and energy variation of the neutrons as well as the attenuation of γ rays in the scatterer. The resulting yield curve is in good agreement with previous measurements.

The 48Ca(d,n)49Sc reaction at Ed = 5.5 and 6.0 MeV

Abstract Transitions to states in 49Sc have been studied with the 48Ca(d,n)49Sc reaction at Ed = 5.5 and 6.0 MeV. At Ed = 5.5 MeV, angular distributions have been measured for a number of states up to 7 MeV excitation energy. The isobaric analog of the 49Ca ground state was identified at an excitation energy of 11.571 ± 0.009 MeV. Excitation energies for levels in 49Sc have been found to be somewhat lower than those found in previous measurements. However, l-values and spectroscopic factors are shown to be in good aggrement with previously measured values from the 48Ca(3He,d)49Sc reaction.

A six-foot long detector for neutron time-of-flight experiments

Abstract A six-foot detector, covering an angular range of 17° at a distance of 6 m, has been developed. It has a time resolution in the range of 1 of 2 ns for an electronic threshold equivalent to 1.2 MeV neutrons. The angular resolution, obtained by determining the location of the source of scintillation in the detector by time-of-flight techniques, is approximately 3°.

Energy levels, decay scheme, γ-ray branching ratios and lifetimes in 55Fe from the 55Mn(p, nγ)55Fe reaction

Abstract The reaction 55 Mn(p, nγ) 55 Fe has been studied at E p = 4.0 and 6.0 MeV using a pulsed beam. From the experiments at 6.0 MeV, the energy levels of 55 Fe up to an excitation of 3810 keV, their decay scheme and the γ-ray branching ratios have been determined. Levels have been identified for the first time in the (p, nγ) reaction. The results have been compared with those available from the literature. From the 4.0 MeV experiment, the mean lifetime of the 1408 keV level has been determined to be 142.7 ± 6.6 ps by direct timing techniques.

114, 116Cd level structure from the (n, n′γ) reaction

Abstract The 114Cd and 116Cd nuclei have been studied using the (n, n′γ) reaction. Levels and their spins have been confirmed at 558 (2+), 1134 (0+), 1210 (2+), 1284 (4+), 1365 (2+) and 1733 (4+) for 114Cd and at 513 (2+), 1213 (2+), 1220 (4+), and 1381 (0+) for 116Cd. Spin assignments have been made for some previously observed levels and for some new levels at 1843 (1), 1861 (0), 1865 (1), 1959 (1) and 2040 (4) for 114Cd and at 1283 (0), 1644 (2, 3), 1917 (0), 1953 (0), 2120 (0, 1) and 2243 for 116Cd.