Speaker
Description
According to the recent developments in fundamental and applied physics (i.e. calorimetry for high energy experiments and PET scanners in medical physics), Silicon Photomultipliers (SiPMs) are the state-of-the-art sensors for light detection, sensitive to the single photons together with unprecedented counting capability. In addition, SiPMs provide significant advantages in terms of:
- cost and compactness, crucial when large number of channels have to be operated
- magnetic field immunity, important for detectors used in accelerator physics and for future medical systems as MR-PET scanners.
- low operating voltage and power consumption, essential for the qualification within medical appliances
- flexibility in the design, due to the silicon technology and the variety of vendors.
Since the early days of the SiPMs development, the focus shifted towards systems made of a large number of sensors, necessarily requiring front-end electronics integrated into Application Specific Integrated Circuits (ASIC). In the talk, we will report the qualification of the Citiroc 1A ASIC, designed by WEEROC.
The ASIC in use integrates the front-end for 32 SiPMs with tunable bias for each individual channel 0-4.5 V. Each channel has two independent branches with different amplification allowing to characterize the multiphoton spectrum (important for the detector calibration) and to exploit a large dynamic range (up to ~2500 photoelectrons with a typical gain ~10$^6$) at the same time. The signals from both branches are processed through a peak detection and track & hold circuit and the output is externally digitised. In addition, one of the two branches for each channel can be used for trigging and timing. The signal feeds a fast shaper amplifier before going into the fast comparator which allows to obtain time stamp with time resolution up to 100 ps. The initial ASIC qualification was performed using a general-purpose board DT5702 (produced by CAEN S.p.A) which provides the common bias to all the SiPMs together with the access to the basic functionalities of the Citiroc 1A and a data acquisition. A comprehensive analysis was performed using the new DT5550W board, featuring the full control of the ASIC functionality.
The features of the ASIC were investigated interfacing it to arrays of crystals in a module developed for a table-top PET system by the University of Aveiro. Moreover, particle imaging was performed by the reconstruction of the impact point of a particle through the center of gravity of the light emitted by a monolithic scintillator sensed by an array of SiPMs.
