TA11-367: Beam Monitoring at High Dose-Rate with Silicon Sensors (BeaMHiSi)

https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 DOI: 10.5281/zenodo.17287982 RADNEXT Transnational Access Summary Report Project title Beam Monitoring at High Dose-Rate with Silicon Sensors (BeaMHiSi) Project TA identifier TA11-367 General application High-energy accelerators, Medical applications, FLASH and minibeam radiotherapy Type of test Radiation monitor calibration, Beam diagnostics Group leader, Institute Anna Vignati, University of Turin and National Institute for Nuclear Physics (INFN) Torino Co-authors, Institutes Roberto Sacchi, University of Torino and INFN Torino, Italy Simona Giordanengo, INFN Torino, Italy Umberto Deut, University of Torino and INFN Torino, Italy Arianna Ferro, University of Torino and INFN Torino, Italy Felix Mas Milian, INFN Torino, Italy, and Universidade Estadual de Santa Cruz, Bahia, Brazil Diango Montalvan Olivares, University of Torino and INFN Torino, Italy Date(s) of the experiment 08/04/25 – 06/05/25 Facility HollandPTC, Delft Amount of access granted 8h Objectives of the experiments The main goal was to characterize the response of thin silicon sensors, readout with a multi-channel front-end chip (TERA09), under ultra-high dose rate (UHDR) proton beams. This includes studying the linearity of the sensors’ response, charge recombination effects, beam perturbation, and spatial resolution, with the final goal of demonstrating the feasibility of using this technology for beam monitoring and quality assurance in UHDR radiotherapy. The choice of proton beams at the Holland Proton Therapy Center is motivated by the need to test the sensors under clinically relevant energies (70-250 MeV) and dose rates, especially UHDR regimes (> 40 Gy/s average dose rate). Two types of prototype sensors were used: 1. Multi-pad silicon sensors (various thicknesses and areas), for studying fundamental charge collection and recombination mechanisms. 2. A 2.6 x 2.6 cm² strip sensor (146 strips), to evaluate performance in spatially resolved beam monitoring. EDMS 3328315 v.1 status In Work access Restricted PDF from TA11-367-Zenodo.doc modified 2025-10-07 16:00 https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 These tests aim at addressing the known limitations of silicon detectors and readout electronics (e.g., non-linearity of the response at high charge densities) and assess their potential as an alternative to ionization chambers for real-time monitoring in advanced radiotherapy modalities. Experiment test report This experiment was aimed at evaluating the response linearity and performance of thin silicon PiN detectors—both pad and strip architectures—when exposed to ultra-high dose rate (UHDR) proton beams. The experiment was conducted under the RADNEXT open data framework to assess sensor linearity, spatial resolution, saturation thresholds, and signal readout strategies across different beam modalities. A key objective was to validate the robustness of thin silicon detectors and readout electronics under UHDR irradiation conditions. Detector information • Technology: PiN silicon multi-pad sensors • Beakdown Voltage: > 500 V • Depletion Voltage: ~10 V • Pre-Irradiation Testing: I-V curves confirmed full functionality Pad sensors: • Active Thickness (μm): 45, 15 • Tested area (mm²): 0.25, 2 • Wafer Lot: produced by Fondazione Bruno Kessler (Trento) within the EXFLU1 project Strip sensors: • Active Area: 2.6 × 2.6 cm² • Strip Pitch: 180 μm • Active Thickness (μm): 45, 60 • Wafer Lot: produced by Fondazione Bruno Kessler (Trento) within the MoveIT project Read out System: Parameter Pad Sensors Strip Sensors Chip TERA09 (64-channel) TERA09 (2 × 64-channel) DAQ Platform NI sbRIO-9606 NI sbRIO-9606 Charge Quantum 600 fC 600 fC DAQ sampling 80 MHz 2 kHz Bias Voltage 200 V 150–290 V Experimental Conditions: • Energy: 250 MeV • Beam-on time run: 100 ms • Dose rate range: up to 1480 Gy/s (corresponding to a beam current of 800 nA at the exit window) https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 Dosimetry and Monitoring Reference in-situ: • Beam monitor: BMI07 UHDR ionization chamber (DE.TEC.TOR) • Dosimeter: Advanced Markus Chamber (PTW) • Beam profile: Lynx detector (IBA) Results and Preliminary Analysis: Pad Detectors linearity: The following plots show the correlation between measured current and dose rate for 45 μm (in red) and 15 μm thick pad sensors (in blue) both for 2 and 0.25 mm². https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 Strip Detectors: Beam Profiling and Saturation Behavior: Three configurations were explored to assess saturation thresholds. Configuration Sensor Thickness Readout Scheme Max Dose Rate A 45 μm 2 TERA09 chips used (64 ch each), 128 strip sensor; each strip is readout by a separate TERA09 channel ~565 Gy/s B 45 μm The signal of 1 strip over four is readout by 4 channels of TERA09 chip, so that the strip current is split into 4 channels. Only 32-strip out of the 128 available are readout. ~1210 Gy/s C 60 μm One strip out of the 128 available is readout through a passive current divider ~1480 Gy/s A. The results show saturation of the electronics (central strip current plateau at ~3 mA) at ~600 Gy/s, which corresponds at a beam current of ~300 nA at the exit window. a) b) (a) Beam profiles projected along the vertical axis for four different dose rates. The response of strip no. 56 is highlighted in violet. (b) Saturation behaviour of the readout electronics observed in strip 56, which becomes evident at dose rates exceeding 600 Gy/s https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 B. This configuration preserves linearity < 2.5% deviation despite reduced spatial resolution. a) b) a) Beam profile projection acquiring 32 out 128 strips of the silicon strip detector. b) Linearity response of the central strip as a function of the delivered dose rate. C. This configuration demonstrates that a resistive divider effectively extends linearity up to 1480 Gy/s, which corresponds to the maximum value of beam current that can be reached at the exit window (800 nA). a) b) a) Beam profile measured with the silicon strip detector. The positions of the two analyzed strips are indicated: the strip connected without a current divider (in red) and the strip connected with a current divider (in black); b) Current response of the same two strips as a function of the average dose rate. https://radnext.web.cern.ch/ https://www.linkedin.com/company/radnext EDMS NO. 3328315 VALIDITY Released REV. 1.0 All the objectives of the experiment were successfully achieved, demonstrating the linearity, reliability, and robustness of the ultra-thin silicon PiN sensors and the TERA09 readout system under ultra-high dose rate proton irradiation, in conditions relevant to UHDR radiotherapy. Outcome of the experiments Please indicate what the experiment is likely to lead to by putting an ‘X’ next to one or more of the possible outcomes below. Journal publication X Data for Thesis X Follow-up experiment at same facility X Follow-up experiment at another facility X Other As a RADNEXT user, we encourage you to submit the scientific results of your experiments to journals as well as to the NSREC and RADECS data workshops. Please remember to include the RADNEXT acknowledgment into your publications! RADNEXT acknowledgment: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 101008126.