Detection of Environment Ionization Radiation with GM Tube

Abstract

For environmental ionizing radiation hazard monitoring applications, very sensitive detector electronics has been developed. Experiments were performed using International Standard beta and gamma sensitive Mica window type GM Tube LND-712 from LND Inc. USA and Russian fast GM Tube with Aluminium energy compensated shield. Both tubes were operated with regulated DC high voltage power supply in the range of 300V to 500V range using Matsusada Japan make 1kV 5W programmable regulated high voltage power supply. LND-712 GM Tube has operating range from 450V to 650V. LND-712 was operated at 500V which is the mid-range of the plateau response for this tube. It has a dead time of about 100us. Russian Tubes is low diameter and has lower operating voltage of 320V to 400V and also has less dead time of 50us. Peak pulse charge current for each event detected was 15uA for which pulse voltage of about 15V was formed across 1M load resistor. Pulse shape was found to be very stable and natural cosmic ray background event rate detected by the GM Tube in Gwalior was in the range of 50 to 120 counts per minute in about 5uR/hour cosmic ray background. GM Tubes were also tested with 660keV Gamma Cs-137 low activity Gamma radiation source. Radiation interaction with matter and energy transfer by the ionizing radiation within GM Tube, charge multiplication and charge collection leading to pulse shape formation will be discussed. Results obtained with the tested GM Tube, the designed circuit scheme and its performance on the test bench system will be presented.