Evaluation of rad-hard epitaxial silicon diode in radiotherapy electron beam dosimetry

The dosimetric response of an epitaxial (EPI) silicon diode for clinical electron beams was investigated using Siemens KD2 and Primus Linear Accelerators. All measurements were performed with the diode unbiased and operating in the short-circuit current mode using a PMMA phantom. Within the energy range of 6 MeV–21 MeV, the output current signals exhibited good instantaneous repeatability (CV≤2.4%), measured through switching on/off the electron beams. Furthermore, the diode showed a quite linear response, given by the charge versus absorbed dose, with charge sensitivities higher than 0.86 μC/Gy. The percentage depth dose profile (PDD) and transversal dose profile (TDP) were also measured in PMMA. The PDD and TDP results were in excellent agreement with those calculated with Monte Carlo code using the OncentraMasterPlan® Treatment Planning System (TPS). However, despite of showing energy dependence effects, neither dark currents increase nor memory effects were observed in the device response.