Stray radiation produced in FLASH electron beams characterized by the MiniPIX Timepix3 Flex detector

Abstract

This work aims to characterize ultra-high dose rate pulses (UHDpulse) electron beams using the hybrid semiconductor pixel detector. The Timepix3 (TPX3) ASIC chip was used to measure the composition, spatial, time, and spectral characteristics of the secondary radiation fields from pulsed 15–23 MeV electron beams. The challenge is to develop a single compact detector that could extract spectrometric and dosimetric information on such high flux short-pulsed fields. For secondary beam measurements, PMMA plates of 1 and 8 cm thickness were placed in front of the electron beam, with a pulse duration of 3.5 µs. Timepix3 detectors with silicon sensors of 100 and 500 µm thickness were placed on a shifting stage allowing for data acquisition at various lateral positions to the beam axis. The use of the detector in FLEXI configuration enables suitable measurements in-situ and minimal self-shielding. Preliminary results highlight both the technique and the detector’s ability to measure individual UHDpulses of electron beams delivered in short pulses. In addition, the use of the two signal chains per-pixel enables the estimation of particle flux and the scattered dose rates (DRs) at various distances from the beam core, in mixed radiation fields.

A 2D strip ionization chamber array with high spatiotemporal resolution for proton pencil beam scanning FLASH radiotherapy

“…The newly developed semiconductor pixel detector demonstrated a robust response under UHDR conditions from individual detector elements. Challenges still exist in managing a large data set with a high acquiring rate sampled with thousands of detectors 42 . Scintillation‐based detectors usually provide high spatiotemporal resolution for the spot size and position measurement 43–45 .…”

“…31,34,[43][44][45] 2D pixel detector array is widely used for patient-specific QA measurements, but saturation to UHDR invalidated most commercial detector arrays for FLASH-RT Challenges still exist in managing a large data set with a high acquiring rate sampled with thousands of detectors. 42 Scintillation-based detectors usually provide high spatiotemporal resolution for the spot size and position measurement. [43][44][45] A recent study reported great results on a new scintillation detector with a fast, intensified CMOS camera for PBS dose rate measurement.…”

Monte Carlo modelling of pixel clusters in Timepix detectors using the MCNP code

“…The readout chip contains a matrix of 256 × 256 pixels (total 65 536 independent channels, pixel size 55 µm) and an active sensor area of 14 mm × 14 mm for a total sensitive area of 1.98 cm 2 [6]. This detector has the readout electronics detached from the Timepix3 ASIC and a sensor assembly to minimize scattering and self-shielding by using a 5-cm-long flexible printed circuit board [7]. Thanks to the timestamp of each hit with the precision of 1.5 ns and the energy absorbed in each individual pixel, the pixelized structure of the sensor allows recording of particle tracks.…”

Thermal neutron detection and track recognition method in reference and out-of-field radiotherapy FLASH electron fields using Timepix3 detectors

“…In that aim, customised detectors, based on the Timepix3 chip, were equipped with thermal neutron converters made out of a 6 LiF compound (Šolc et al 2022) to allow for measurements of thermal neutron flux in real time. To achieve the goal of this investigation, an enhanced method for particle field characterization with emphasis on thermal neutron imaging and detection using the highly-integrated miniaturized MiniPIX Timepix3 module in miniaturized customised architecture (Oancea et al 2022 was developed. In this investigation, a calibration of individual converters was performed in a reference field and the corresponding thermal neutron detection efficiency was determined.…”