4H-silicon carbide as particle detector for high-intensity ion beams

Abstract

In ion cancer therapy, high-intensity ion beams are used to treat tumors by taking advantage of the Bragg-peak. Typical ion therapy centers use particle rates up to 1010 ions/second for treatment. On the other hand, such intensities are often too high when using these beamlines for particle physics experiments or as a test-beam environment in general. The project presented here aims to develop a beam position and intensity monitor, to cover a wide intensity range from a few Hz up to GHz rates, as used in clinical settings. Silicon carbide (SiC) is an attractive detector material for this application because it combines potential high radiation hardness with high thermal conductivity to avoid cooling. Moreover, its high electron saturation velocity allows very fast signals to mitigate pile-ups. However, some special properties of the material like different crystal polytypes have to be considered. In this paper, measurements on both a pad and a micro-strip SiC sensor prototype of 4H lattice geometry are shown. The sensors were tested in the laboratory using radioactive sources and with a proton beam in a wide intensity range (kHz–GHz) and with different energies (60–800 MeV) available at MedAustron, an ion cancer therapy center located in Austria. The measurements show that MIP particles cannot be detected reliably with the used discrete electronics setup in combination with the single-channel sensor. However, the strip sensor combined with an ASIC-based readout electronics from the CMS/Belle-II experiments allows to recover a certain part of the signal. This makes it possible to determine the ionization energy and average number of electron/hole pairs generated in the studied sensor samples.