Speaker
Description
Many technologies initially developed for particle physics are now employed in medical particle beam therapy. One area where technology transfer is more challenging is particle sensing, as requirements differ substantially. While particle physics requires detecting and characterizing every particle hitting the detector, only the beam's statistical properties are important in ion beam therapy. However, the particle rates are substantially larger, reaching $10^{11}$ $\mathrm{cm^{-2} s^{-1}}$. We are working on a primary beam monitor to bridge the gap between these requirements. We have developed a detector system capable of detecting single particles at fluxes of up to around $10^5$ $\mathrm{cm^{-2} s^{-1}}$ while also being capable of characterizing the beam at clinical particle rates.
We will present the concepts employed in the particle detector and measurement results from prototype testing. The particle detector employs an array of low-noise integrators with variable gain, initially intended for use in X-ray TFT panels. In the highest gain mode, the integrators showed a noise of 600 to 1000 $e$, enabling the discrimination of single particles when paired with suitable particle sensors. In the lower gain modes of the integrators, beams at clinical rates can be characterized. When needed, configurable attenuators can further extend the dynamic range. Tests were carried out using both silicon and silicon carbide (SiC) particle sensors. SiC sensors proved ideal for our detector due to their negligible dark current, enabling lifetimes up to $5 \cdot 10^{15} $ $\mathrm{n_{eq}/(cm^2 s)}$. SiC Strip sensors were optimized for high-voltage operation using TCAD simulations to extend the lifetime of radiation damage sensors further. A tiled sensor layout was adopted for sufficient production yield.
