R.O. Bondelid

Quasifree processes in the 2H + 3He interaction

Abstract Quasifree scattering and quasifree reaction processes have been examined in the 3 He+ 2 H → p+d+d, 3 He + 2 H → n+p+ 3 He and 3 He+ 2 H → p+p+t reactions. Beam energies of E d = 22.3 and 35 MeV and of E 3He = 30, 33.5, and 52.5 MeV were used. The experimental results are compared with PWIA calculations and Fourier transforms of the wave functions are extracted. The quasifree processes are described qualitatively by the PWIA, but some features cannot be described by either PWIA or DWIA.

Quasi-free scattering in the D(p, pn)p reaction from 15 to 50 MeV

Abstract The D(p, pn)p reaction was studied in a kinematically complete experiment. Comparison with the kinematically equivalent D(p, pp)n reaction shows the surprising result that the measured cross section for the (p, pn) reaction is a factor of seven larger than that of the (p, pp) reaction at the lower energies. The impulse approximation describes the shape of the observed energy spectra, but does not predict the measured magnitude.

Three absolute energy calibration points for protons below 3 MeV

Abstract An electrostatic beam-energy analyser has been used to make absolute energy measurements of the following resonances and threshold: Be9(p, γ)B10, 1083.2±0.4 keV; N15(p, αγ)C12, 897.37±0.29 keV; and O18(p, n)F18, 2576.72±0.77 keV. The widths of the two resonances were measured to be 3.25±0.33 keV and 1.5±0.3 keV, respectively. For calibration purposes, the peak of a thin-target resonance yield curve, the midpoint of the rise of a thick-target resonance yield curve, and the intercept of the extrapolated threshold yield curve do not correspond precisely to the above values, but corrections are given to enable such yield curves to be used directly for energy calibration of proton beam-energy analysers.

Two-spectator quasifree processes

Abstract Two-spectator quasifree processes (graphs with two spectator particles) for the 3 He( 3 He, dd)pp reaction at the symmetric angle pairs θ = 30.1° at E 3 He = 50 MeV and θ = 37° at E 3 He = 78 MeV are investigated. The theoretical cross sections are calculated with the PWIA model. The measured cross sections are smaller but have shapes which are in good agreement with the calculation. The ratio N = experiment/theory is approximately 0.05 at 50 MeV and 0.1 at 78 MeV. The reaction 2 H(d, pp)nn also was studied at the symmetric angle pair θ = 34.8° and E 2 H = 34.7 MeV and the ratio is about 0.14.

Study of the (p, pn) reaction in light nuclei

Abstract The (p, pn) reaction on 2H, 6Li, 7Li, 9Be has been studied at 47 MeV bombarding energy. Excitation energy spectra and energy sharing spectra are presented. Fragmentary information on 10B, 11B and 12C was also obtained. Sequential decay contributions to the 6Li(p, pn)5Li∗ reaction suggest an admixture of parentage (α)π( p 1 2 )π( d 5 2 ) for the (3−), 23 MeV excited state of 6Be. A possible 15.5 MeV excited state in 6Be is reported. An extensive study of the 9Be (p, pn)8Be reaction for 45 MeV protons was made. Results for θp = θn = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θn = 40°, θp = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θp/θn = 40°/45°, 38.5° are reported and compared to DWIA calculations. Agreement is good when the lower momentum components of the wave function are sampled, and deteriorates as higher momenta are required. Results are in agreement with the Cohen and Kurath spectroscopic factors for 9Be.

Direct interaction effects in the fission of 238U with 63.5 MeV 4He ions

Abstract Position-sensitive semiconductor detectors have been used to measure both in-plane and out-of-plane angular correlations for binary fission events from 63.5 MeV 4 He ion-induced fission of 238 U. From these data a value of 7.5±1.0% has been derived for the contribution of direct interaction mechanisms to the total fission cross section at 63.5 MeV. When this result is included with recent theoretical expressions, the interpretation of fission fragment angular distribution data is found to be consistent with both theory and low-energy results up to this energy. The most probable total kinetic energy release was found to be 173.3±5.4 MeV for the compound nucleus 242 Pu. The measured variations in the average fission fragment kinetic energies and the widths of the fragment spectra as a function of correlation angle are interpreted in terms of effects arising from direct interactions, neutron evaporation and the reaction kinematics.

The use of position-sensitive semiconductor detectors in the study of heavy element nuclear reactions☆

Abstract The application of position-sensitive semiconductor detectors to the study of heavy element nuclear reactions at intermediate energies is described. Experimental procedures and results are presented for the use of these devices in the following types of measurements: (1) binary fission fragment angular correlations; (2) fission fragment angular distributions; (3) kinetic energy release in fission, and (4) spallation recoil product angular distributions. The position-sensitive detectors are found to provide much improved experimental efficiency over normal semiconductor detectors in experiments where the angular dependence of the products is quite strong; e.g. fission fragment angular correlations and spallation recoil angular distributions. For experiments in which the product counting rates vary slowly with angle, such as fission fragment angular distributions, the position detector is much less useful. Although the energy resolution of these devices is poorer than normal detectors, they are advantageous in experiments designed to study fission energetics as a function of reaction kinematics.

Quasifree processes in the3He+3Hand3He+3He interactions

Abstract Quasifree scattering and quasifree reaction processes have been examined in ten 3 H + 3 He and 3 He + 3 He reactions with at least two of the three or more final state particles being charged. Beam energies of 50, 65 and 78 MeV were used. The experimental results are compared with PWIA predictions and Fourier transforms of the wave functions are extracted. The quasifree processes are described in a consistent, but qualitative, manner by the PWIA; distortion in the intial state appears to be the cause of the consistent deviation of the data from the PWIA predictions. Extracted values for the 3 H(d, 3 He)2n cross section are given.

QUASIFREE PROCESSES IN THE REACTION 3He + 3He FOR E3He = 50, 65 and 78 MeV

This chapter discusses quasi-free processes in the reaction 3 He + 3 He for E 3He = 50, 65 and 78 MeV. There are several three-particle breakup combinations that can occur when 3 He bombards 3 He. Measurements for a number of quasifree scattering (QFS) and quasifree reactions (QFR) interactions for 3 He + 3 He have been obtained in kinematically complete experiments. Charged particle pairs are detected and conditions are chosen favoring the observation of quasifree processes. The data are analyzed in terms of the plane-wave-impulse-approximation with the Hulthen wave function. In a study described in the chapter, gas cell target and fixed detector-aperture geometry was used. The effective target thickness and detector solid angles were calculated. The calculations were compared to measurements of the product of these parameters from 2 H(p,p) 2 H and 2 H(p,pp)n two- and three-body reactions for E =22 MeV where the d 2 σ and d 3 σ are well known.

QUASIFREE PROCESSES IN THE 2H + 3He REACTIONS

This chapter discusses quasi-free processes in the 2 H+ 3 He reactions. In the interaction between 3 He and 2 H, there are several three-particle breakup combinations possible. Kinematically, complete measurements were obtained with 2 H beam energies of 22.3 and 35 MeV and 3 He beam energies of 30.0, 33·4, and 52.5 MeV. Charged particle pairs were detected with conditions favoring the observation of quasi-free processes, both quasi-free scattering (QFS) and quasi-free reactions (QFR). The d + d, p + d, and 3 He + p QFS interactions and the 3 He + n→ p + t, d + d → p + t, and 3 He + n → d + d QFR interactions were observed. The chapter presents the analysis of data for a given interaction and comparison of a plane-wave-impulse-approximation prediction. The momentum wave function is extracted for small values of spectator momentum. Data were acquired primarily with a gas cell target having either 2 H or 3 He gas and fixed detector-aperture geometry. The results indicate that there is little difference in d 3 σ (exper)/d 3 σ (PWIA) as a function of beam energy (incoming channel CM energy), and this ratio does not depend on whether the spectator is in the projectile or in the target.