D.M. Sheppard

The elastic scattering of intermediate energy protons from 40Ca and 208Pb

Abstract Elastic scattering of protons from 40 Ca and 208 Pb has been studied using the MRS facility at TRIUMF. Cross section and analyzing power ( A y ) angular distributions to 50° in the center of mass have been measured for incident proton energies of 200, 300, 400 and 500 MeV. Comparisons of the experimental results are made with calculations based on relativistic and non-relativistic phenomenological models, and with relativistic and non-relativistic microscopic models. The differences between the results of the non-relativistic and relativistic models manifest themselves in the spin observables. They are found to be smaller in the phenomenological approach than in the microscopic one and they depend on energy.

Measurements of vector and tensor analysing powers for 191 and 395 MeV deuteron scattering

Abstract Vector ( iT 11 ) and tensor ( T 20 and T 22 ) analysing powers for 191 and 395 MeV deuterons are reported for dp and dd elastic scattering and d-nucleus (Li, C, Ni, Pb) inclusive scattering with a rough selection on the outgoing deuteron energy. Applications to and the feasibility of intermediate energy deuteron polarimeters are discussed.

Polarization and angular correlation measurements following the 40Ar(p, nγ)40K reaction

Abstract Gamma-ray angular distributions and polarization correlations have been measured using the reaction 40Ar(p, nγ)40K. All the experiments were carried out with bombarding energies close to threshold for the states under investigation. Comparison with compound nuclear predictions has yielded the following spin assignments to states in 40K; 1.959(2+), 2.047(2−), 2.070(3−), 2.103(1−), 2.261(3+), 2.290(1+), 2.291(4, (3)), 2.419(2,3), 2.575(2,4) and 2.625(0−). Multiple mixing ratios together with the gamma-ray branching ratios have been determined for all these levels. A short theoretical treatment of the polarization of gamma rays from aligned nuclei using the phase-consistent formalism of Brink and Rose is included.

Investigation of high spin states in 55Fe from the 55Mn(p, nγ) reaction

Abstract Electromagnetic decay properties of the low-lying states in 55 Fe were studied using the 55 Mn(p, nγ) 55 Fe reaction. The measurement of γ-ray angular distributions together with predictions based on the compound nuclear statistical model has permitted unique spin assignments to be made to the following excited states in 55 Fe: 1.316 MeV ( 7 2 ), 1.408 MeV ( 7 2 ), 2.144 MeV ( 5 2 ), 2.211 MeV ( 9 2 ), 2.301 MeV ( 9 2 ) and 2.470 MeV ( 3 2 ). Some multipole mixing ratios were also determined. Comparison is made with the shell-model calculations of Ohnuma and Vervier.

A study of the excited states of 53Cr via the 52Cr(d, pγ)53Cr reaction

The decay modes of many of the excited states of 53Cr below 4.25 MeV excitation energy have been determined by means of the 52Cr(d, pγ)53Cr reaction. Previous tentative spin assignments of 52−, 32− and 92+ to the 1.006 MeV, 2.324 MeV and 3.715 MeV levels respectively have been confirmed. New spin assignments are the following: 52 or 92 to the 2.227 MeV level, 32− to the 3.190 MeV level, 52 to the 3.271 MeV level and 12 or 32 to the 3.971 MeV level. Multipole mixing ratios are given for many of the observed transitions. Comparison is made with available theoretical calculations based on both the unified and shell models.

Elastic scattering of polarised deuterons from 16O at 200, 400 and 700 MeV☆

Abstract Angular distributions of cross section, and A y and A yy analysing powers were measured for polarised deuteron elastic scattering from 16 O at 200, 400 and 700 MeV. The data at 200 MeV bear evidence of the nuclear rainbow phenomenon while those at 400 and 700 MeV are reminiscent of the proton scattering results at equivalent energies. The data were analysed in terms of the optical model. The real central potential shape changes from an attractive Woods-Saxon form at 200 MeV to a wine-bottle-bottom form with a repulsive interior at 700 MeV. The total reaction cross sections deduced display a clear nuclear transparency effect in the present energy domain in agreement with predictions from the Glauber theory optical limit. Comparison with previous results for 40 Ca and 58 Ni targets is made.

A study of levels of 27Mg by the 27Mg(d, pγ)27Mg reaction

Abstract Spins of levels in 27 Mg below 5 MeV and the branching ratios and multipole mixing parameters of their gamma decays have been investigated using the 26 Mg(d, pγ) 27 Mg reaction and method II of Litherland and Ferguson. The present results combined with previous work lead to an assignment of J π = 3 2 + for the 3.782 MeV level and J = 7 2 for the 3.757 MeV level. The spins of the 3.109 and 4.394 MeV levels have been limited to J = 3 2 or 7 2 and J = 3 2 , 5 2 or 9 2 , respectively. Several previously known spins have been confirmed. The decay modes of most of the levels up to E x ≈ 5 MeV have been determined. The experimental data are compared with the predictions of the Nilsson model and shell model.

Gamma-ray angular correlation studies of low-lying levels in 23Na

Gamma-gamma correlations following the bombardment of 23Na with 4.71 and 5.12 MeV protons have been measured using method I of Litherland and Ferguson. Experiments have been carried out on gamma rays cascading from the 2.08, 2.39, 2.71 and 2.98 MeV levels in 23Na. The deduced spins of the 2.08 and 2.71 MeV levels are 72 and 92, respectively. The mixing ratios of the 0.44 → 0, 2.08 → 0.44 and 2.71 → 2.08 MeV gamma rays are −0.06 ± 0.04, −0.24 ± 0.07 and −0.02 ±0.09, respectively. Evidence consistent with a spin assignment of 12 to the 2.39 MeV level is presented.

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.

Energy levels of 31S

Abstract The level structure of 31S was investigated using the reactions 29Si(3He, n)31S, 29Si(3He, nγ)31S, and 29Si(3He, nγγ)31S at 6.5 MeV. Previously unreported 31S levels were identified in neutron time-of-flight spectra at 6277, 6796, 6921, 7112, 7445, 7850, 7985, 8183, 8362 and 8453 keV excitation (all ± 25 keV). Angular distribution measurements confirm J π = 1 2 + assignments for the ground state and for states at 3079, 5151 and 7006 keV. The second T = 3 2 state in 31S was identified at 7006 ± 25 keV excitation. The ground state mass of 31C1 was calculated from the isobaric multiplet mass equation to be M − A = −6935 ± 45 keV. In γ-ray coincidence measurements, precise values of excitation energy were determined for 31S levels at 1248.9 ± 0.2, 2235.6 ± 0.4, 3079.0 ± 1.1, 3285.5 ± 0.5, and 3351.1 ± 0.6 keV.