Gas-Filled Gamma-Radiation Detector Based on High-Purity Xenon

Abstract

This paper reports on the development, manufacturing and testing of proportional γ-ray detectors filled with gas mixtures based on high-purity xenon. To let the gas mixtures into the detector, a special installation was developed and manufactured, consisting of components designed to work with high-purity gases. The influence of the gas pressure, its composition (pure Xe or its mixture with H₂, CH₄), and the voltage at the anode on the spectrometric resolution and gas gain of the detectors was studied. The addition of H₂ or CH₄ to xenon is used to increase the charge carrier drift velocity. These additives also stabilize the gas mixture, i. e. decrease the probability of gas breakdown at high voltage between the detector electrodes. Gas xenon, as well as its mixtures, of research purity grade (99.9999%) have been used. Proportional γ-ray detectors based on xenon gas can operate in both counting and spectrometric modes. To study the characteristics of the detectors, we used standard sources of γ-radiation ²⁴¹Am, ¹³⁷Cs, ¹⁵²Eu, ¹³³Ba. The best energy resolution values to date were obtained for a detector filled with a gas mixture of Xe + 2.1% CH₄ at a pressure of 2.5 bar and an anode voltage of 2500 V; they were ~ 9.5% for an energy of 40 keV and ~ 5% for 120 keV. In the manufacturing of detectors intended for radiation monitoring and identification of radioactive materials, in particular in nuclear power, complex materials science problems have been solved. To increase the thermal and radiation resistance, all elements of the detector construction are made of materials that are weakly activated by ionizing radiation. In addition, the design of the detectors is completely free of glass elements and organic components. The detectors are designed to monitor technological processes and to work as part of radiation monitoring systems, including those at nuclear power plants.