S. Salvatori1,2; S. Pettinato1,2; M. Girolami2; D.M. Trucchi and M.C. Rossi3
- Department of Engineering, University “Niccolò Cusano”, 00166 Rome, Italy
- Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), 00016 Rome, Italy
- Department of Industrial, Electronic, and Mechanical Engineering, Roma Tre University, 00146 Rome, Italy
A single-crystal diamond sample grown by high-pressure high-temperature (HPHT) technique was used for the fabrication of a metal–semiconductor–metal (MSM) photoconductor. The sample quality was evaluated by means of spectral photocurrent measurements highlighting the presence of a significant density of defect states within the diamond bandgap, responsible for trap-mediated conduction mechanisms. The photoconductor was fully characterized under 6 MeV pulsed X-rays, sourced by a medical linear accelerator (LINAC), in the 0.05–20 Gy and 0.017–0.100 Gy/s dose (D) and dose-rate (DR) ranges, respectively. Photocurrent measurements performed with a conventional precision electrometer showed that the detector performance is strongly affected by charge-trapping phenomena, resulting in a sublinear dependence with the DR (power-law dependence with an exponent of 0.86). Measurements were repeated in the same experimental conditions by coupling the detector to a specifically developed gated integrator, allowing for a synchronous integration of photocurrent pulses (limited to 40 μs). It is demonstrated how a type IIa HPHT diamond detector, combined with a synchronous detection technique, achieves excellent linearity in dose and dose rate under pulsed X-rays at 6 MeV from a medical LINAC. This method mitigates the effects of charge de-trapping, a long-standing limitation for HPHT diamond detectors in radiation dosimetry.