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Description
Recently, the ASTRI project has placed a contract with Hamamatsu Photonics to acquire hundreds of SiPM tiles to build 10 cameras with 37 tiles each for the mini array of 9 Cherenkov telescopes of the ASTRI Project. Each tile is constituted by 8x8 pixels of 7x7 mm2 with micro-cell of 75 µm. To check the quality of the delivered tiles a complex and fine test plan has been studied. The possibility to analyse simultaneously as many pixels as possible becomes of crucial importance.
Dark Count Rate (DCR) versus overvoltage and versus temperature and Optical Cross Talk (OCT) versus overvoltage can be easily measured simultaneously for all pixels because are carried out in dark conditions. On the contrary, simultaneous PDE measurement of all pixels of a tile is not easily achievable and needs an appropriate optical set-up. Simultaneous measurements have the advantage of speed-up the entire procedure and enable quick PDE comparison of all pixels’ tile.
The paper describes the preliminary steps to guarantee an accurate absolute PDE measurement, the investigation on the capability of the electronics to obtain simultaneous PDE measurements, the possibility to use a calibrated SiPM as reference detector instead of a calibrated photodiode and finally, the method to achieve accurate absolute PDE of four central pixels of a tile.
