J. Birchall

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.

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.

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.

Two counter geometry factor for bremsstrahlung experiments

Abstract A technique is presented for the calculation of the efficiency of detection of two coincident particles. The technique has been applied to the interpretation of the results of bremsstrahlung experiments, but is sufficiently flexible to be easily applied to other cases. Various detection geometries are considered. The dependence of the bremsstrahlung cross-section on the noncoplanarity of the detected particles is included explicitly in the efficiency calculation.

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.

New method for the measurement of angular distributions of cross sections and polarizations

Abstract A method for the simultaneous measurement of angular distributions of scattering cross sections and polarizations with gaseous targets and steep kinematic curves is described. More precise and faster data acquisition is possible than with conventional methods.

RELATIVE CROSS SECTION IN p-p SCATTERING AT 4.21 MeV OBTAINED WITH A NEW METHOD

Publisher Summary This chapter illustrates the relative cross-section in p–p scattering at 4.21 MeV obtained with a new method. It discusses an experiment performed with the van de Graaff of Universite Laval using a new method for the simultaneous measurement of an angular distribution. It is well known that when the masses of a projectile and a target are comparable, there is a strong kinematic effect and a sizable change of energy with scattering angle. If the target is gaseous, a single detector viewing the beam line receives particles from a continuum of scattering angles. The kinematic energy variation permits the determination of the angular interval from an energy interval of the measured spectrum. The chapter also describes an experiment in which there are two types of background: a target empty background and a background from gas impurity. Moreover, a geometrical correction is also necessary to take into account the variable beam length and solid angle of detection.

DIFFERENCES IN THE THREE-BODY FINAL STATES OF 10B(d,α)αα AND 9Be(3He,α)αα AT LOW ENERGIES

Publisher Summary This chapter discusses the differences in the three-body final states of 10B(d,α)αα and 9Be(3He,α)αα at low energies. The α-8Be final state is suitable for a study of the final-state interaction (FSI) problem. By reaching the same final state through different entrance channels, it becomes possible to evaluate the importance of production process effects in final-state spectra. Particle detection and identification are carried out with three silicon surface barrier detectors and an electronic circuit; it is used without significant changes. Dominant two-body interactions reproduce the present three-body final-state spectra obtained from two different entrance channels and therefore, possible off-the-energy-shell transitions, higher order processes, and other dynamical effects are very weak.

α-α BREMSSTRAHLUNG AT 9.35 MeV

Publisher Summary Bremsstrahlung in the α–α system is of interest because of the considerable role of the α–α interaction in problems of nuclear structure. This chapter discusses α–α bremsstrahlung at 9.35 MeV. The α particle has no excited states below 20 MeV and the α–α system has a high threshold for particle emission. This has two important consequences. First, at energies below the threshold, the internal structure of the α particle can be neglected that enables important theoretical simplifications in a wide energy interval. Second, bremsstrahlung experiments can be made at energies low enough to neglect effects of the threshold and then, the behavior of the cross-section can be investigated as a function of energy up to and in the continuum. The experiment discussed in the chapter was performed at the van de Graaff laboratory of Universite Laval. Significant improvements were done in the technique by the addition of a thin Ni foil in front of the silicon detectors. This resulted in a considerable reduction of detector noise and thus, the time pick-off units (TPO) could be placed between the detectors and the preamplifiers.