A.R. Johnston

An analysis of polarization and cross-section data for the p-3He system at 30 and 50 MeV

Abstract Differential cross-section and polarization measurements on the p- 3 He system at 30 and 50 MeV have been analysed in terms of real phase shifts. It is shown that there is not sufficient data at either energy to define a unique solution.

Elastic and inelastic scattering of 3He particles from 10B at 32 MeV

Abstract The differential cross sections for the elastic and inelastic scattering of 32.46 MeV 3 He particles from 10 B have been measured. The elastic differential cross section has been analysed in terms of the optical model. The angular distributions for inelastic scattering to the 0.717, 1.74, 2.15, 3.585, 4.77 and 6.03 MeV levels of 10 B were compared with the predictions of the collective model using DWBA analysis.

POLARIZATION IN THE ELASTIC SCATTERING OF 50-Mev PROTONS BY DEUTERONS AT BACKWARD ANGLES

Abstract The polarization in p(d,d)p scattering of 50 MeV protons has been measured in the angular range 120° to 175° c.m. The polarization changes rapidly to positive values at 135° and has a maximum of +0.185 ±0.015 at 145°.

Nucleon-nucleon final-state interactions in the reactions 3He(p, d)2p, 4He(p, t)2p and 4He(p, 3He)pn

Abstract The energy spectra of deuterons, tritons and 3 He particles from the reactions 3 He(p, d)2p, 4 He(p, t)2p and 4 He(p, 3 He)pn have been measured at angles between 6° and 60° lab. The 3 He(p, d)2p reaction was studied at both 30.5 and 49.5 MeV incident proton energies, while the other two reactions were studied at 49.5 MeV only. The energy spectra are compared with calculations based on the Watson-Migdal model of final-state interactions.

The T = 2 isobaric multiplet at mass 24

Abstract The reaction 26 Mg(p, 3 He) 24 Na has been investigated at E p = 50 MeV. Isobaric analogue states with T = 2 have been identified and angular distributions identify the L = 0 character of the interactions. The mass 24, T = 2 quintet is considered in the context of the charge idependence of nuclear forces.

Estimation of organ depth by gamma ray spectral comparison

In order to measure the amount of radioactive tracker taken up by an organ in the human body, it is necessary to determine the depth of the organ in the body. A procedure is presented which is similar to the valley-to-peak method of Mohindra and McNeill (1965) but involves analysis of the entire pulse-height spectrum. Measurements are made on 131I with a water phantom and a single collimated detector in a fixed position. A set of calibration spectra are taken for a source at depths ranging from 2 to 15 cm in 1 cm increments. Then test spectra are taken for fixed times with sources placed at various depths. By comparing a test spectrum with the calibration spectra, it is possible to calculate the source depth. The method is checked for dependence of calculated depth on source thickness and on background concentration.

Polarization in the elastic scattering of 30 MeV protons by 3He

Abstract The polarization in p-3He elastic scattering at 30 MeV in the angular range 33° to 160° c.m. has been measured. The magnitude of the polarization is very much greater than that predicted from an optical-model analysis of cross section data, but is consistent with the values found at lower energies.

Polarization in the elastic scattering of 9.5 MeV and 21.6 MeV protons by deuterons

Abstract Polarization in the elastic scattering of protons by deuterons has been measured at 21.6 MeV in the angular range 93°–160° c.m. and at 9.5 MeV in the range 20°–160° c.m. The polarized proton beam of the RHEL linear accelerator was used in conjunction with deuterated polyethylene targets and a double-focussing magnetic spectrometer. The 21.6 MeV results extend earlier measurements at 22 MeV to larger angles but indicate a higher angle of cross-over from positive to negative polarization and a smaller maximum value of negative polarization than before. The backward positive maximum is in good agreement with the n-d data. At 9.5 MeV, the present results are in good agreement with a previous measurement at 10.0 MeV and extend the angular range to 20° c.m. Although a dip to negative polarization in this region has been reported at 11.0 MeV, no evidence for this is found at 9.5 MeV.

The occurrence and measurement of accidental coincidences in experiments using pulsed accelerators

Abstract The calculation and measurement of accidental coincidence rates in detector systems using pulsed accelerators is considered in detail. Accidental counting rates are expressed as a function of the coincidence resolution of the detector system, the pulse structure of the beam intensity and of the delay in the coincidence unit inputs.

Cross-section measurements for the reaction 10B(p, 3He)8Be

Abstract Cross sections have been measured for the transitions to the ground state and first excited state of 8Be and to the two 2+ levels at 16.63 MeV and 16.93 MeV excitation in the reaction 10B(p, 3He) at Ep = 49.5 MeV. The angular distributions of the cross section were compared with DWBA predictions.