A kinetic model of diode detector response to pulsed radiation beams

Abstract

Diodes dosimeters present a complex response to pulsed beams, with diode sensitivity varying with dose-per-pulse, monitor unit rate (time between pulses) or number of integrated pulses. Such a response is caused by the complex kinetics of the interplay among charge carriers, recombination-generation centers, which capture excess minority charge carriers and facilitate recombination with a majority charge carrier, and traps with energy levels close to the conduction/valence band, which can trap and release charge carriers. This behavior has been well characterized experimentally, and modeled with phenomenological models. In this work we present a kinetic multi-compartment model of the response of diode detectors, which includes the interplay among charge carriers, recombination-generation centers, and traps. The model can qualitatively fit experimental data extracted from the literature on diode response versus dose-per-pulse, monitor unit rate (time between pulses), or number of integrated pulses. In this regard, our work provides further insight on the response of diode detectors, and a theoretical framework for the development of simple phenomenological models.

Commercial photodiodes and phototransistors as dosimeters of photon beams for radiotherapy

“…This behavior has been extensively observed and modeled for the response of this kind of devices to both instantaneous 32–34 and average dose rate 35 . Recently, a kinetic model of diode detector response to pulsed radiation beams has been reported, claiming that this behavior can be properly modeled whatever the method to generate dose rate variations 36 . In few words, the sensitivity increase has been explained for the decrease in recombination rate of radiation‐induced minority charge due to the saturation of the recombination center at higher‐dose rates 32 .…”

“…35 Recently, a kinetic model of diode detector response to pulsed radiation beams has been reported, claiming that this behavior can be properly modeled whatever the method to generate dose rate variations. 36 In few words, the sensitivity increase has been explained for the decrease in recombination rate of radiation-induced minority charge due to the saturation of the recombination center at higher-dose rates. 32 According to our results, the comparative experimental data of Fig.…”

Dosimetry for FLASH Radiotherapy: A Review of Tools and the Role of Radioluminescence and Cherenkov Emission

“…The sensitivity of the aforementioned diamond detector is shown in Figure 5. Recombination in diodes is also a complex physical process; whereas sensitivity of IC decreases with increasing dose per pulse, diodes are known to over respond at high dose per pulse [53][54][55]. The physical basis of this dependence is due to insufficient number of RG centers available for the excess minority carriers to recombine at high dose-rates and doses per pulse.…”

“…To the best of our knowledge, no FLASH study has used diodes for dosimetric verification. Kinetic modeling of the recombination process in solid-state detectors has been carried out by multiple groups and we point the reader toward those references for a deeper understanding [49,[54][55][56].…”

Semiconductor dosimetry in modern external-beam radiation therapy

“…On the practical level, it was recommended to calibrate clinical devices at the expected average accelerator repetition rate (Kozelka et al 2011), with some newer devices offering a built-in software correction (Ahmed et al 2019). Neira et al (2019) provided a theoretical framework, based on a kinetic multi-compartment model, to describe the dependence of diode sensitivity on instantaneous dose rate and on average dose rate. The kinetic depends on the minority carriers, and on the nature of G-R centres in silicon (figure 4).…”