A fast calibration system for SiPM-based scintillator HCAL detector

We report on latest version of the calibration and monitoring system developed for the scintillator tile hadron calorimeter (AHCAL) for the ILC. System is based on original fast (3 ns pulsewidth) and precise LED driver called QMB. One UV-LED can illuminates 72 scintillating tiles with SiPM. Distribution of the light pulses uses notched fibres, developed at our laboratory. All parts of the system are continually upgraded to get better results. The system is flexible to all necessary task monitoring and calibration of SiPM detector. It has high dynamic range of precise a few nanosecond pulses. Low intensity LED pulses are needed to obtain nice SiPM single photoelectron spectra. A routine monitoring of all SiPMs during test beam operations is achieved with mid-range a fixed-intensity light pulse. The full SiPM response function is cross-checked by varying the light intensity from zero to the saturation level. In calibration systems we developed, we concentrate especially on the aspect a high dynamic range of precise a few nanosecond pulses. Calibration system has been tested with 2.2m long slab of engineering AHCAL prototype uses 864 SiPM embedded in 3 by 3cm scintillator tiles and represents a part of the biggest planned detector using SiPMs.