Thin LGADs and thin silicon diodes for applications in radiotherapy

F Mas Milian^1*E M Data¹Anna Vignati^1,2Marco Donetti³Matteo Centis Vignali⁴Marco Ferrero¹V Ferrero^1,2Elisa Fiorina¹V Monaco^1,2D Montalvan Olivares^1,2Francesco Pennazio¹Marco Giuseppe Pullia³Valentina Sola^1,2Roberto Sacchi^1,2Simona Giordanengo^1*

• ¹National Institute of Nuclear Physics of Turin, Torino, Italy
• ²Universita degli Studi di Torino Dipartimento di Fisica, Turin, Italy
• ³Fondazione Centro Nazionale di Adroterapia Oncologica, Pavia, Italy
• ⁴Fondazione Bruno Kessler, Trento, Italy

Low-Gain Avalanche Diodes (LGADs) and thin n-on-p silicon diodes, when read out by fast and custom electronics, exhibit characteristics that make them promising candidates for the development of new detectors to be used for clinical applications as beam commissioning, diagnostics and monitoring, for dosimetry and online treatment delivery verification. Compared to gas ionization chambers, these detectors offer significantly higher sensitivity, enabling the detection of single particles at fluxes up to 108 particles/cm²s sufficient to cover the entire clinical intensity range of carbon ion therapy and about one order of magnitude lower for proton therapy. Various front-end electronics have been developed and characterized for readout configurations ranging from single channels (pads or strips) to arrays of up to 144 strips. These systems have been applied to single-particle identification for beam monitors in particle therapy, as well as to two-dimensional beam monitoring and dosimetry in Ultra-High Dose Rate and Spatially Fractionated Radiotherapy. This review summarizes the detectors based on LGADs and thin n-on-p silicon diodes developed within the INFN-CSN5 projects MoVeIT, SIG, and FRIDA. Specifically, we present a 2.7 × 2.7 cm² particle counter for measuring beam fluence and position, a beam energy detector based on primary particle's time-of-flight, a setup for studying beam time structure at the nanosecond scale, and a system for range verification via prompt gamma timing. Current advancements in various technologies are reviewed, together with challenges and future perspectives on the application of LGADs and thin silicon diodes in radiotherapy.