R. Roy

A high efficiency proton polarimeter with silicon detector analyser

Abstract A description of the polarimeter and its performance is given. It surpasses all other polarimeters in efficiency at comparable energy resolutions for protons of energies larger than 20 MeV. The scattering yield Y is 3 × 10−3 at 29 MeV with an anlysing power P of −0.3, giving a figure of merit 〈PY 1 2 〉 of 1.6 × 10−2.

Origins of intermediate velocity particle production in heavy ion reactions

In this paper, we report for the first time clear distinctions between these prompt processes and an alternative phenomenon of delayed aligned asymmetric breakup that populates the intermediate-velocity zone by a deformation rupture of mainly the heavier of the colliding partners in mass asymmetric collisions. These distinctions were observed experimentally with intermediate-velocity particle correlation analysis of Ni+C and Ni+Au reac

Facility for the measurement of proton polarization in nuclear reactions

Abstract A polarimetry facility based on high resolution and high efficiency silicon polarimeters with on-line particle identification is described. It has proven its capability to measure polarizations in ( 3 He , p ) reaction with cross section levels of 40 μb/sr.

Final state interaction and direct features of the 9Be(τ, α)αα and 10B(d, α)αα reactions

Abstract Alpha-particle spectra and α-α correlations have been measured from the 9 Be(τ, α)αα and 10 B(d, α)αα reactions at several energies between 2.9 and 10.0 MeV. Significant difierences in the spectra from the reactions were observed at equal c.m. energies and momentum transfer values. However the continuous energy spectra have been successfully analyzed with two-body interactions as obtained from elastic α-α scattering, within a formalism adequate for a three-body state. DWBA fits have also been obtained for both reactions but they are satisfactory only for the 9 Be(τ, α) 8 Be reaction.

The width of the 2.9 MeV state in 8Be from the 7Li(d,n)8Be reaction☆

Abstract Experimental results on the 7 Li(d,n) 8 Be reaction at 3.72 and 4.76 MeV bombarding energy reported here, and previous results at lower energies are successfully interpreted in terms of a two-body final-state interaction in a three-body system, resolving an existing discrepancy between two-body phase shifts (or parameters) and the width of the neutron peak.

Isospin effects and symmetry energy studies with INDRA

Abstract.The equation of state of asymmetric nuclear matter is still controversial, as predictions at subsaturation as well as above normal density widely diverge. We discuss several experimental results measured in heavy-ion collisions with the INDRA array in the incident energy range 5-80A MeV. In particular an estimate of the density dependence of the symmetry energy is derived from isospin diffusion results compared with a transport code: the potential part of the symmetry energy linearly increases with the density. We demonstrate that isospin equilibrium is reached in mid-central collisions for the two reactions Ni+Au at 52A MeV and Xe + Sn at 32A MeV. New possible variables and an improved modelization to investigate symmetry energy are discussed.

Diffusion des protons polarisés sur 24Mg, 27Al et 32S et anomalies dans la région des résonances géantes de l'25Al, du 28Si et du 33C1

Abstract Differential cross-section and analyzing power angular distributions have been measured for the elastic scattering of polarized protons on 24 Mg, 27 Al and 32 S between 13 and 27 MeV. An optical model analysis has been performed and the spin-orbit potentials display significant variations in the giant resonance region of 25 Al, 28 Si and 33 C1. The 24 Mg and 32 S data have been examined in a phase-shift analysis.

ANALOG-DIGITAL FAST TIMING WITH LOW ENERGY PARTICLES.

Abstract A simple technique has been used to improve timing resolution and noise rejection in coincidence experiments obtainable with time pick-off and solid state detectors. Walk has been reduced typically from 50 ns to less than 1 ns for α particles of energies between 0.5 to 10 MeV. The technique is of special interest to increase the true to random coincidence ratio between two detectors.

Bremsstrahlung in the proton-proton interaction at 6.92 MeV

Abstract Measurements of p-p bremsstrahlung cross sections have been performed by detecting the two final-state protons in coincidence at 37°–37° and 38°–38° in the laboratory system, yielding respectively the following values corrected for noncoplanarity 1.2 ± 0.5 and 1.7 ± 0.7 μb sr −2 in fair agreement with theoretical values. This appears to resolve a discrepancy existing at low energies between theory and experiment, within the quoted errors.

BREMSSTRAHLUNG IN THE 3He-α INTERACTION

Publisher Summary This chapter discusses bremsstrahlung in the He–α interaction. It presents a study on the first BS measurement in the He–α system performed at the van de Graaff laboratory of Universite Laval. The measurement was performed with the Harvard geometry at 37°–37° and an incident energy of 7.4 MeV. A theoretical value was calculated for the He–α BS with expression based on the Feshbach–Yennie model corresponding to the dipole transition. A Fortran IV program was written to calculate the BS cross-section averaged over the kinematic region accepted by the finite apertures of the gas geometry collimators. The experimental result being slightly smaller than the theoretical value, there is no evidence whatsoever of enhancement because of the re-scattering effects. This would be consistent with p–d results where, in the absence of a resonant state in the compound nucleus, no appreciable contribution of the re-scattering effect was observed.