S. T. Thornton

Measurements and calculations of neutron detector efficiencies

Abstract Neutron detector absolute efficiencies measured in our laboratory for several organic scintillators are reported. A substantially revised version of Kurzs neutron detector efficiency computer program has been used to calculate efficiencies for new and previous measurements. Good agreement has been obtained for various scintillators.

7Li(p, n)7Be neutron polarization measurements for Ep = 3.0 to 5.5 MeV

Abstract Angular distributions of neutron polarization have been measured for 7 Li(p, n 0 ) 7 Be and 7 Li(p, n 1 ) 7 Be∗ at proton energies 3.0, 3.5, 4.0,4.5, 5.0 and 5.5 MeV. From Legendre polynomial fits of σ(θ) and associated Legendre polynomial fits of P (θ)σ(θ), contour maps of P ( θ ) and P 2 ( θ ) σ ( θ ) were produced. Levels in the compound nucleus 8 Be and the reaction mechanism are discussed.

High momentum transfer RT,L inclusive response functions for 3,4He.

Inclusive electron scattering cross sections for {sup 3,4}He have been measured in the quasielastic region at electron energies between 0.9 and 4.3 GeV, and scattering angles of 15{degree} and 85{degree}. Longitudinal ({ital R}{sub {ital L}}) and transverse ({ital R}{sub {ital T}}) response functions have been extracted using a Rosenbluth separation at constant {vert bar}{bold q}{vert bar} of 1.050 GeV/{ital c}. The ratio of the longitudinal to the transverse reduced response functions in the negative {ital y} region reaches unity.

Spectroscopic investigation of the 144Sm(3He, α)143Sm reaction

Abstract The 144 Sm( 3 He, α) 143 Sm reaction has been investigated with high resolution at 30 MeV bombarding energy with the Heidelberg Q3D magnetic spectrograph. Over 30 levels in 143 Sm were identified, and spectroscopic factors were obtained for 21 levels by comparing DWBA calculations with the measured differential cross sections. Good agreement with unified model calculations was obtained for the l = 0,2 and 5 transitions, but not for the l = 4 transitions for which several angular distributions were measured.

States in 24Mg populated by the 10B(16O, d)24Mg and 12C(16O, α)24Mg reactions☆

Abstract States in 24 Mg were populated by the 10 B( 16 O, d) and 12 C( 16 O, α) reactions. Excitation functions at 7° for many of the levels were measured for bombarding energies between 40 and 46 MeV for the 16 O + 12 C reaction, and from 44 to 46 MeV for the 16 O + 10 B reaction. The reactions appear to be predominantly due to compound nucleus formation, and general agreement was found comparing the measured cross sections with Hauser-Feshbach calculations. The experimental cross sections for the members of the K π = 0 + and 2 + rotational bands are particularly well reproduced by the calculations up through the 8 + states.

Measurements of 3H(d, n)4He neutron polarizations for Ed = 1.0 to 5.0 MeV

Neutron time-of-flight techniques and a liquid-helium polarized-neutron analyser were used to measure seven neutron polarization angular distributions for the 3H(d, n)4He reaction at deuteron energies from 1.0 to 5.0 MeV. Using Legendre polynomial expansions of σ(θ) and P(θ)σ(θ), values of P(θ) and P2(θ)σ(θ) were calculated, and a contour map of P(θ) was produced for the energy range 1.0 to 5.0 MeV. Various techniques used to measure the 3H(d, n)4He polarizations are discussed, and previous and present results are compared.

The HHIRF supersonic gas jet target facility

Abstract We describe a supersonic gas jet target built for studying reactions induced by heavy ions with high energy resolution. The device produces very localized high density gas jets in a near vacuum environment and is presently installed in the scattering chamber of a magnetic spectrograph at the ORNL HHIRF. With a 100 MeV 16 O beam collimated to a size of approximately 1 mm 2 at the target, image sizes of 0.42 mm have been obtained at the focal plane of the spectrograph with a solid angle of 2.4 msr and target densities of 15–30 μg/cm 2 .

FIRST MEASUREMENT OF THE REACTION 3HE(GAMMA ,P)X WITH POLARIZED PHOTONS

The first measurement of the reaction He-3(gamma over arrow pointing right, p)X using linearly polarized photons is reported. Cross sections and beam-polarization asymmetries for theta(p)lab = 60-degrees - 100-degrees and E(gamma) - 195-304 MeV are compared with a microscopic calculation which includes one-, two-, and three-nucleon absorption mechanisms. One- and two-nucleon absorption alone fails to describe the data at low proton momenta. The inclusion of three-nucleon absorption significantly improves the comparison with the measured cross sections. However, some features of the asymmetry distributions are not explained.

Neutron and proton components of nuclear transitions in pion inelastic scattering on 26Mg

Abstract The elastic and inelastic scattering of 180 MeV positive and negative pions from 26 Mg has been measured. From these data the ratios of neutron and proton nuclear transition matrix elements have been determined for the first and second excited states. These ratios are compared with those obtained from electromagnetic transitions in mirror nuclei and with shell model predictions.

The reaction: High-spin states, resonances and coherence widths

Abstract Excitation functions were measured for states of 21 Ne populated by the 12 C ( 13 C , α) reaction over the bombarding energy range E lab = 18.2–32.0 MeV (18.4–27.0 MeV) at θ lab = 7°(25°) in in 200 keV steps, and average coherence widths of states and the moment of inertia of the compound nucleus 25 Mg were obtained from these excitation functions. A statistical analysis of these data was performed. Angular distributions for states in 21 Ne to 10 MeV in excitation energy were measured at θ lab = 7°, 18°, 28° and 43° at bombarding energies from 29.0 to 31.0 MeV in 400 keV steps. These data along with Hauser-Feshbach predictions allow us to suggest spins for some states as well as to suggest possible candidates for rotational bands in 21 Ne.