J.W. Verba

Differential cross sections and polarizations in elastic p-d scattering at medium energies

Abstract Differential cross sections for p-d elastic scattering have been measured at 22.0, 35.0 and 46.3 MeV using the energy-analysed external proton beam of the UCLA sector-focussed cyclotron. The angular distributions cover centre-of-mass angles between 9° and 168°. At forward angles both protons and deuterons were observed using a d E /d x - E telescope counter consisting of a fully depleted surface-barrier detector ( ΔE ) and a NaI(Tl) scintillation detector. ( E ). At larger angles, protons were observed using an array of four NaI(Tl) scintillation detectors. The differential cross sections have in general a relative uncertainty less than 2%, while the absolute scale of the measurements has an uncertainty of 1.7%. The proton polarization angular distributions at 35.0 and 40.0 MeV were also measured. In this part of the experiment, the polarized proton beam facility was used. The polarized proton beam was obtained by scattering the internal beam of the cyclotron from a carbon scatterer. At 35.0 MeV, the polarization angular distribution covers centre-of-mass angles between 20° and 164°. At 40.0 MeV, measurements were made for centre-of-mass angles greater than 130° only. Scattered particles were observed using six NaI(Tl) scintillation detectors placed in groups of three on either side of the incident beam. The target used when detecting elastically scattered protons was deuterium gas. The backward part of the angular distribution was measured by detecting recoil deuterons from a deuterated polythylene target. The available proton polarization data for p-d elastic scattering have been used to construct a polarization contour diagram for the energy range of 10–400 MeV.

Measurement of the angular distribution of 4He(p, d)3He, 4He(p, 3He)pn and 4He(p, t)pp reactions

Abstract We have measured the angular distribution of the reaction 4 He(p, d) 3 He at 47 MeV over the center-of-mass angular range of 12–166°. We have also measured the angular distributions of the reactions 4 He(p, 3 He)pn and 4 He(p, t)pp in the region of the nucleon-nucleon final state interaction at the same bombarding energy over an angular range of 7.5° to 50.0° in the laboratory. The 3 He and triton energy spectra are also presented and Watson-Migdal fits to these data in the region of the nucleon-nucleon final state interaction are shown.

Inelastic scattering of 46 MeV protons from 12C

Abstract The differential cross sections for the excitation of nine levels of carbon have been measured each at 35 angles from 15° to 150°. The cross sections for the 4.4 and 9.6 MeV levels have a typical relative accuracy of 3%, while the measurements for the 7.7, 10.8, 11.8, 12.7, 14.1, 15.1 and 16.1 MeV levels have a typical accuracy of 10%. The cross sections decrease by from one to three orders of magnitude through the measured angular range. Levels at 13.3 and 16.6 MeV were not observed. The angular distributions have been compared with distorted wave calculations using both macroscopic and microscopic approaches.

A technique for measuring proton total reaction cross sections at medium energies

Abstract Total proton reaction cross sections between 20 and 50 MeV have been measured at the UCLA 50 MeV Cyclotron Laboratory. Our method, a variation of the attenuation technique first proposed by Gooding and Eisberg, is described. Features include a tightly collimated and well defined beam, the ability to use either solid or gaseous targets, and rapid accumulation of the data.

The effects of the neutron pickup process on 3He (p, pd)p quasi-free scattering

Abstract Anomalies in the QFS enhancement in the 3 He(p, pd)p reaction have been observed. The effects of the coherent addition of the 3 He(p, d) pp l = 0 neutron pickup mechanism to the QFS amplitude have been investigated and this calculation qualitatively reproduces the basic features of the data.

A study of the 9Be(p, pα)5He reaction at 26.0, 35.0 and 46.8 MeV

Abstract The cross sections for the reaction 9 Be(p, pα) 5 5 He were measured at 26.0, 35.0 and 46.8 MeV incident energies. The resulting data were analyzed in the plane-wave impulse approximation and compared to the results of existing data taken at 55.0, 57.0, 155.0 and 160 MeV. These data appear to be consistent with an S-state of relative motion of the α-cluster.

Some evidence on the electric dissociation of the negative hydrogen ion near 2.4 MeV/cm☆

Abstract The dissociation of the negative hydrogen ion (H−) by electric ν × B stripping in a magnetic field has been measured for electric fields near 2.4 MeV/cm. The ions were obtained from the UCLA sector-focussed cyclotron and were stripped by the 24.86 kG hill field at energies up to 48 MeV. The experimental results are compared with the predictions of Khuri, Khoe, Darewych and Neamtam, Hiskes and are found to favor strongly the values predicted by Hiskes. Other observations of ν × B stripping are compared with the present data.

Limitations and improvements of trace element analysis with proton-induced X-rays

The technique of trace element analysis by the detection of characteristic X-rays induced by high energy proton bombardment is critically examined. A discussion of the restrictions imposed by detector resolution is made, the behavior of the cross-section for X-ray production as a function of energy and atomic number is discussed. The effect of this behavior upon analysis time is demonstrated. Background is discussed in terms of its effect on the total counting rate. The use of a silicon solid state detector to determine the overlappingK-lines of light elements andL-lines of heavy elements is shown to have severe limitations. A combination of crystal monochromators and solid state detectors is suggested as a means to circumvent some of the fundamental limitations encountered with a single detector. An experimental arrangement for the use of twenty-four crystal monochromators and two solid state detectors is shown.

A search for T = 12 resonances in p+4He elastic scattering

Abstract The excitation function of the differential cross section of the 4 He(p, p) 4 He reaction has been measured for the four laboratory angles 82.3°, 92.3°, 102.3°, and 112.3° at incident proton energies between 22 and 46 MeV. A complete angular distribution for the 4 He(p, p) 4 He reaction has been measured at 47 MeV incident energy. In addition excitation functions at laboratory angles of 23.5°and 70.0° were measured for the 4 He(p, d) 3 He reaction between bombarding energies of 38.5 to 44.6 MeV. The investigation was undertaken to see if any T = 1 2 resonance effects exist in the p+ 4 He compound system from possible “states” in 5 Li around 20, 22 and 25 MeV. No departure from a monotomic energy dependence can be discerned to within the accuracy of the individual experimental points.

A new technique for obtaining (p,n) angular distributions☆☆☆

Abstract A somewhat novel technique has been developed to obtain angular distributions for (p,n) reactions populating isobaric analog states (IAS) when they decay by proton emission (p). It entails obtaining neutron time-of-flight spectra measured relative to p events rather than to the periodic structure of the beam. This technique is found to significantly simplify experimental arrangements for time-of-flight measurements.