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Silicon photomultipliers are commonly used to detect the passage of radiation in matter via the collection of photons produced by the ionizing radiation in converting materials. We investigated the possibility of direct detection of high-intensity X-ray fluxes using the measurement of the current produced by silicon photomultipliers directly exposed to the X-ray beam, in absence of any converter material. We have analyzed the response of different devices directly exposed to the radiation produced by an X-ray tube. The signal-to-noise ratio of the response confirms that the current produced during the irradiation provides information on the X-ray flux intensity. We parametrize the current response of SiPM devices as function of the X-ray flux intensity. We verify that the parametrization is accurate down to the % level and we study the linearity of the response to investigate the prospects for possible applications in real-time X-ray beam monitoring and beam spatial profiling.

The third generation of Near Ultraviolet High Density (NUV-HD3) Silicon Photomultipliers (SiPMs) produced by Fondazione Bruno Kessler in collaboration with Istituto Nazionale di Fisica Nucleare (INFN) have been tested and characterized in INFN laboratories. Arrays of 16 pixels have been assembled to equip the focal plane of the prototype Schwarzschild-Couder Medium Size Telescope (pSCT) proposed for the Cherenkov Telescope Array Observatory. Each camera module is composed by 4 matrices of 16-pixel optical units coupled with TARGET-7 ASIC front-end electronics for signal amplification and digitization. A total of 9 modules have been successfully integrated on the pSCT camera and are currently taking data. In this contribution we provide a summary of the performances of the HD3 technology as measured in the INFN laboratories. We also report on the laboratory tests performed on the assembled optical units, showing their performances and homogeneity in terms of gain, signal-to-noise ratio and dark count rate.