Design of a Compton-suppression spectrometer and its application to the study of high-spin yrast states

Gamma ray spectroscopy of high-spin states is hampered by transitions with low intensity on a high gamma ray background. An approach to enhance weak peaks in a spectrum in the reduction of the Compton background by means of a Compton-suppression spectrometer (CSS). Optimization of a CSS by means of Monte Carlo calculations is described. The investigation of high-spin states in the sd-shell nucleus Ar-38 with a Compton-suppression spectrometer is reported. With previously described techniques, in combination with p-gamma coincidence measurements to establish an unambiguous level scheme, states up to Jsup(pi) = 11- could be identified and investigated. A gamma-gamma coincidence experiment on the nuclei Hf-167 and 168 is described with two Compton-suppression spectrometers. Yrast bands are followed, beyond the region of the first backbending, up to spin J = 37/2 and J = 28 for Hf-167 and Hf-168, respectively.