Spectral perturbations from silicon diode detector encapsulation and shielding in photon fields

Abstract

Spectra calculated for photon fields in water can be directly used for modeling the response of unshielded silicon diodes with plastic encapsulations. Unshielded diodes used together with appropriate corrections can replace shielded diodes in photon dose measurements.

Evaluation of the IAEA‐TRS 483 protocol for the dosimetry of small fields (square and stereotactic cones) using multiple detectors

“…Shielded diodes are known to overestimate dose relative to water, and exhibit greater perturbations in small field measurements due to the additional metallic layer present around the active volume. Higher uncertainties in the correction factor are caused by the attenuation of low‐energy photons, and simultaneous increase in contributions from electron scatter . These effects contribute to make larger and more uncertain correction factors.…”

Energy response corrections for profile measurements using a combination of different detector types

“…Further evidence for the likelihood of perturbations at extracameral parts causing the response differences between the SFD and other diodes is the amount of details needed in Monte Carlo simulations to obtain correction factors for output in small fields: While the SFD can be approximated as simply the silicon chip in water, the successor model 60017 of the diode 60012 used in this study needs to be modeled with the additional filter plate above the chip to reproduce experimental observations . Eklund and Ahnesjö observed only slight spectral changes for scattered photons and primary electrons caused by the encapsulation of an unshielded diode comparable to the SFD set in a larger field, while the presence of a shielding caused a larger effect …”

Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields

“…2(b), was modeled with similar dimensionality and materials as other Monte Carlo work with the IBA PFD diode detector. 23 The active volume (silicone) was a disc 0.5 mm thick and 2.5 mm in diameter, set 0.3 mm below the surface of the detector. The 2.5 mm diameter region behind the active volume was modeled as epoxy through the remainder of the 17 mm length of the detector.…”