Evaluation of scintillation materials and silicon photomultiplier for dosimetry Master of Science Thesis in the Master Degree Programme Biomedical Engineering

Scintillators have been widely used in radiation detection for almost one century. It has traditionally been used together with a photomultiplier tube (PMT) but in recent years silicon photomultipliers (SPM) has begun to compete with the PMT. This opens opportunities for new applications like pocket size dosimeters. The purpose of this thesis is to investigate the use of different scintillator materials combined with a SPM to make dosimetry on a wide energy spectrum and to do sensitive detection of low dose rate. Four different scintillators were investigated whereof one plastic and the others inorganic, the scintillators were BC-428, BGO, LYSO(Ce) and CsI(TI). The SPMs used were from Sensl and contained two different variations, both with the area of 2.85x2.85 mm but with 20x20 μm respectively 35x35 μm microcell size, called SPM 3020 and SPM 3035. The best combinations for dosimetry in the diagnostic energy range is CsI(TI) with SPM 3035 and SPM 3020, resulting in a dose rate approximation within 6 percent (compared to the PTB calibrated Xi survey probe used for reference) for energies between 32and 96 keV. Clear spectrums for energies down to 17 keV were obtained with the SPM 3035 combination. The other detection solutions are not applicable for the used energies. The capability to detect low dose rates was found to be exceptional since background radiation (0.1μGy/h) could be measured with one count per second (CPS).