Two dimensional array of multi-pixel photon counter and cesium iodide crystal (Thallium Activator) for radiation monitoring prototype

Abstract

An efficient radiation and position monitoring system is useful for preliminary security inspection as well as for radiation emergency preparedness and response. For these applications, a high sensitivity and efficient monitoring system is required. Two position-sensitive prototypes were proposed using solid state detector (multipixel photon counters, MPPC) and inorganic scintillator (cesium iodide with thallium activator, CsI(Tl)). This inorganic scintillator was chosen for its output wavelength compatibility with MPPC, slightly hygroscopic, high photon transmission, and input energy. For both prototypes, eight MPPCs with different configurations were used to obtain active areas of 2.0 x 2.4 cm2 and 2.5 x 4.5 cm2. These prototypes were read out using EASIROC-NIM module and tested with beta (Tl-204; 763.76 keV) and gamma (Co-60; 1.1732 keV) radioactive sources at different positions. The experiments showed that both prototypes were sensitive to both beta and gamma radiation and was able to determine the positions of the sources accurately. The prototype 2 was found to have a better resolution in terms of pixel that is only limited by resolution of the calculation, which is 250 steps in this setup whereas prototype 1 only have 8 pixels. In addition, the experimental efficiency for both prototypes were calculated and compared. The prototype 1 has better efficiency (with beta, 8.86 % and gamma, 18.15 %) than the prototype 2 (with beta, 1.65 % and gamma, 2.07 %). The setup in this study can be further enlarged to be adapted in industries such as security and medical sectors.