H. Olliver

A high-efficiency NaI(Tl) detector array with position sensitivity for experiments with fast exotic beams

The twenty-four trapezoidal NaI(Tl) detectors previously used as part of the trigger detector for the APEX experiment at Argonne National Laboratory have been adapted for use in experiments with beams of fast exotic isotopes at the National Superconducting Cyclotron Laboratory at Michigan State University. A high-efficiency position-sensitive detector is ideal for inelastic scattering studies with exotic beams produced at projectilefragmentation facilities. The g rays emitted from fast-moving projectiles ðv=c ¼ 0:320:5Þ are Doppler-shifted considerably. The energy in the projectile frame can be reconstructed by simultaneously measuring the emission angle and energy ofthe lab f rame photon. Position sensitivity (3 cm FWHM) is achieved by reading out photomultiplier tubes at both ends ofeach detector in coincidence. The large solid-angle coverage (75% of4 p) and high intrinsic efficiency result in a total photopeak detection probability of 17% at 1332 keV with an energy resolution of about 13%. r 2003 Elsevier Science B.V. All rights reserved.

Trends In Collectivity Approaching N = 28

To address the question of collectivity in neutron‐rich nuclei near N=28, an inverse kinematics inelastic proton scattering experiment has been performed. Confirmation of excited states in 36,38Si has been made. The path from excitation cross‐section to deformation parameter is outlined.

Recent Experimental Results from the NSCL on the Structure of Exotic Nuclei

The Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory at Michigan State University provides a large variety of new isotopes previously inaccessible and others at rates sufficienct for in‐beam spectroscopy. This talk presents some of our recent results elucidating the structure of exotic nuclei.After a general overview of scientific highlights from the first two years of operation particular results from several in‐beam gamma‐ray spectroscopy experiments in the vicinities of neutron numbers N=16, N=20, N=28 in the π(sd) shell around 56Ni will be discussed. Inelastic scattering experiments with gamma‐ray detection on light and heavy targets have determined specific transition matrix elements and excited state energies. One‐ and two‐particle nucleon knockout reactions were used to investigate the wave functions of specific states and to deduce corresponding spectroscopic factors.

Measuring angular distributions of gamma‐rays emitted from fast exotic beams

We propose to apply the techniques of γ‐γ angular correlations and angular distributions for in‐beam gamma‐ray spectroscopy with fast exotic beams. Presented are angular distribution plots which include Doppler shifts and different degrees of alignment of the m‐substates. The plots indicate that angular distribution measurements of gamma rays produced by nuclear fragmentation reactions at relativistic velocities are feasible.