Design and implementation of a low cost, high performance ionizing radiation source detection and source direction finding system

Abstract

This study shows the design, implementation, and test results of a low-cost portable radiation-detector system relies on a directionally designed multi detector probe that works in Geiger-Müller counting mode with a single chip solution. The proposed system can perform the functions of detecting the ionizing radiation source, counting gamma and showing the direction and angle of the gamma source relative to the position of the device. The radiation direction finding (RDF) system consists of a radiation probe and electronic sections that are mounted in a metal box. The probe has a has a cast housing made of lead material and it has 8 directional slots for placing the optically isolated PIN diode arrays where each array consists of 4 parallelly connected BPW 34 PIN model diode. The lead housing also blocks incident rays from unintended directions and provides a directional sensing for PIN diodes. The metal box contains 8 low noise amplifiers and pulse shaping detector boards that are assigned to each channel of PIN diode arrays, a signal inverter board, a step-up high voltage board, a 12 V battery and a parallel processing FPGA board with an embedded VHDL software that can process all 8 channels simultaneously and execute the direction estimation algorithm. The system also has an adjustable detector bias voltage and the applied voltage can be displayed on a seven-segment display located in front of the unit so that different models of PIN diodes can be used and tested with different bias voltage levels. It also has a HMI touch screen unit and user interface for displaying the Cpm or Cps values of each channel; a 360-degree scale showing the direction of the source with its pointer and an indicator showing the direction of the source numerically in degrees. The system works as a gamma detector and the source direction can also be detected within ±45° interval. The success of system within this interval is 99.22%. The detector was tested with low to high energy gamma sources (241Am, 9.761 μCi, 59.54 keV, 137Cs 661, 3.7 MBq, keV and 60Co, μCi, 1173 and 1332 keV) and showed good sensitivity performance level in gamma ray detection. The major outcome of this study and the major contribution of this work to the literature is therefore is the design and production details of a hand-held detector and source direction locator prototype; which is a light, portable and compact system.