Performance tests of the B-RAD radiation survey meter

Abstract

This article discusses performance tests of the B-RAD by ELSE NUCLEAR. The B-RAD is a portable survey meter for γ-ray spectrometry and γ-ray dose rate measurements able to operate in the presence of a strong magnetic field. The detector uses a 15 mm right cylinder LaBr 3 crystal coupled with a 16-pixel Silicon Photomultiplier array. The crystal, the photodetector and the front-end electronics (the probe) are enclosed in a case connected with a cable to a control unit. The latter includes the main electronics, a customised battery pack, two displays and a Faraday cage.More in detail, this paper investigates the instrument performance inside magnetic field, including linearity of its response and its angular response. An operational test is also reported to demonstrate a practical application. The performed tests show that the B-RAD can operate inside magnetic fields up to 2.5 T. Two small shortcomings were observed: a pulling force is felt especially on the control unit, which becomes rather intense for values of the magnetic fields above 1 T, and a slight reduction of the signal gain with increasing magnetic field intensity when the control unit is inside the field. The latter causes a variation of the measured dose rate of less than 10% at 1.5 T. The response of the B-RAD with dose rate is linear up to 20 mSv/h with discrepancies between the reference and the measured dose rate within 10%. The response is isotropic from −120° to ＋120°; beyond this limit the measured dose rate drops by 66% probably because of the scattering of the source photons with the case and some shielding effects.