Dosimetry with a phoswich detector

A phoswich detector concept based on the combination of a high-Z element and a plastic element with a free running analogue-to-digital converter is presented in this work for the simultaneous measurement of operational dosimetric quantities H ∗ (10) and H ′ (0.07) in photon radiation fields. By means of a Pulse Shape Discrimination method and down to an energy of 60 keV ( 241 Am) in continuous photon radiation fields, the signal arriving at the common light sensor was separated into components coming from each element of the detector. In this context, crosstalk between the sensitive volumes represented an obstacle and was solved with a proper covering over one of the elements. Additionally, an algorithm for the calculation of the intended quantities based on the measured deposited doses was developed and tested using Monte Carlo methods with monoenergetic and X-ray radiation fields. Simulations set a validity region for the algorithm to the energy range between 20 keV and 3 MeV in the case of monoenergetic radiation and a lower energy cut of 15 keV in the case of X-ray fields. Furthermore, the algorithm was tested experimentally using 241 Am (60 keV) and 137 Cs (662 keV) sources against reference values from an OD-01 ionization chamber. Results showed a good sensitivity to the incoming photon energy, reflected in the variation of the ratio between the measured doses with the considered energies. At the same time, discrepancies between the measured and reference values of the operational quantities highlighted the need for a better calibration of the algorithm.