Improvement of the performance of a Compton-suppression spectrometer by minimizing the dead layer of the central Ge detector

Abstract

The performance of a Compton-suppression spectrometer is investigated for two different Ge crystals as central detector; a 126 cm3 Ge(Li) with a dead layer of 1.0 mm and a 90 cm3 HPGe with a dead layer of 0.22 mm. The thin dead layer HPGe gives a 32% improvement in the overall Compton suppression. Predictions of the influence of the dead-layer thickness by means of Monte Carlo calculations are in good agreement. The spectrometer is further tested with radioactive sources of **Y and t szEu and the in-beam reaction 24Mg + (45 MeV)160.

A Compton-suppression spectrometer for γ-γ coincidence measurements: Large solid angle and excellent suppression

“…5 of ref. [5] where the solid angle is a factor of 16 smaller. Ey (keY) The areas of the 1173 and 1332 keV peaks taken together amount to 60% of the total number of Results for 6°Co…”

“…A larger HPGe (or preferably a Gamma-X crystal, see ref. [5]) would allow an even bigger solid angle, also with'good Compton suppression. A further decrease of the tinckness of the NaI at the front side, another possIbthty in order to increase the solid angle, is not recommended as it quickly leads to a detenoration of the Compton suppression as the Monte Carlo calculation m fig.…”

“…Such a crystal unproves the Compton suppressaon m the region of the Compton edge, as escape photons of low energy can easily reach the surrounding slueld to produce a veto signal, see ref. [5]. The width of 600 ns for the veto signal is based on the time jitter of the HPGe signal and ts chosen to guarantee a good overlap between the veto signal and the HPGe tune pulse.…”

“…Two different configurations of the shield have been reported [1][2][3][4][5]. The symmetncal Compton-suppression spectrometer [4] consists of a coaxial shield with a hollow core of the central detector.…”

“…The dimensions of the NaI antlcomcidence shield are optlmxzed by means of Monte Carlo calculations, which are described m ref. [5].…”