Modeling an array of encapsulated germanium detectors

TL;DR

This paper develops a probability model to analyze the operation and performance of an array of encapsulated germanium detectors, including cluster, miniball, and SPI spectrometers, with results matching experimental data.

Contribution

The paper introduces a formalism that describes complex germanium detector arrays using only six probability amplitudes, enabling accurate predictions of their performance.

Findings

Model accurately predicts peak-to-total and peak-to-background ratios.

Results show remarkable agreement with experimental data for the SPI spectrometer.

Formalism simplifies analysis of detector arrays with minimal parameters.

Abstract

A probability model has been presented for understanding the operation of an array of encapsulated germanium detectors generally known as composite detector. The addback mode of operation of a composite detector has been described considering the absorption and scattering of gamma-rays. Considering up to triple detector hit events, we have obtained expressions for peak-to-total and peak-to-background ratios of the cluster detector, which consists of seven hexagonal closely packed encapsulated HPGe detectors. Results have been obtained for the miniball detectors comprising of three and four seven hexagonal closely packed encapsulated HPGe detectors. The formalism has been extended to the SPI spectrometer which is a telescope of the INTEGRAL satellite and consists of nineteen hexagonal closely packed encapsulated HPGe detectors. This spectrometer comprises of twelve detector modules surrounding the cluster detector. For comparison, we have considered a spectrometer comprising of nine detector modules surrounding the three detector configuration of miniball detector. In the present formalism, the operation of these sophisticated detectors could be described in terms of six probability amplitudes only. Using experimental data on relative efficiency and fold distribution of cluster detector as input, the fold distribution and the peak-to-total, peak-to-background ratios have been calculated for the SPI spectrometer and other composite detectors at 1332 keV. Remarkable agreement between experimental data and results from the present formalism has been observed for the SPI spectrometer.