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Low-level light sensors

Our are core activities in this field are Silicon Photomultipliers (SiPMs) and Single Photon Avalanche Diodes (SPADs), which are among the most interesting and innovative technologies for the detection of extremely weak light.

Silicon Photomultipliers (SiPM) are low-light detectors, capable of photon counting down to the single photon, with excellent timing measurement capability. They are considered the most promising detector for the replacement of the traditional Photomultiplier Tube (PMT) in a number of applications, including high energy physics, nuclear medicine and scanning electron microscopy.

The typical application of the SiPM is the readout of the light produced by a scintillator crystal, for the detection of gamma and x photons and the measurement of their energy and time of arrival. In particular, the SiPM features a very good timing resolution in the scintillator light readout, of the order few hundreds of picoseconds, and a negligible sensitivity to the magnetic fields. For these characteristics, there is currently a great interest in using the SiPM for next-generation Time of Flight PET machines, integrated with the magnetic resonance (ToF-PET/MR). Different, publicly-funded projects have been approved, including the FP7 Hyperimage and Sublima projects, which SRS is part of.

We starded working on this subject in 2006 in the framework of a collaboration with the Italian Institute for Nuclear Physics (INFN). While the collaboration with INFN is continuing, we expanded the activity to new projects in the field of nuclear medicine, material analysis and biology.

Main activities

SiPM technology evolution

The SRS activity on Silicon Photomultipliers leads to the development of new SiPM technologies, aimed the the optimization of different detector parameters, such as the Dark Count Rate, the Breakdown Voltage uniformity, the Photo Detection Efficiency, the Excess Noise Factor and the Dynamic Range.

Amplitude vs. Time-distance Scatter Plot

We develop automated programs for the advanced characterization of the Silicon Photomultipliers, for extracting precisely their most important parameters, such as Gain, Primary and Correlated noise and Photo Detection Efficiency.

ToF-PET principle

We perform timing resolution measurments with our SiPMs coupled to scintillators, aiming at the characterization and the improvement of their performance for Time-of-Flight PET (ToF PET).

iSiPM principle - 3D

SRS is actively involved in the design of different types of position-sensitive SiPMs, which allow to build ultra-high spatial resolution PET modules with a reduced complexity of the readout electronics.


SiQuro (On silicon chip quantum optics for quantum computing and secure communications) is a project funded by the Autonomous Province of Trento aiming at building a silicon platform for secure quantum computing and communications.

The HYPERImage project drives the development of a brand new system for simultaneous whole-body PET-MR imaging for humans. The goal is not only to improve the existing diagnostic applications, but also to open up new fields in therapy guidance and therapy response monitoring.

The aim of the Sublima project is to further develop the base technologies underlying PET and optimize them for ToF-PET/MR systems. The partners competencies span over the many different fields involved in shuch complex systems. The role of SRS unit is the optimization of the SiPM technology.


Single-channel SiPM preamplifier

We are experienced in the design and characterization of custom front-end electronics for Silicon Photomultipliers, which we adapt to the different needs of the experimental characterization of the detectors.


Large-area SiPM Tile

In the context of the Hyperimage project, a large area SiPM tile was developed, in collaboration with Philips Healthcare.

Tools and facilities

Coincidence Timing Measurement Set-up

The SRS laboratory is equipped for the caharacterization of SiPMs in the readout of the scintillation light for the detection of gamma photons, which is one of the main applications of these detectors.

The laboratoy is equipped with state-of-the-art instrumentation for the electro-optical characterization of the Silicon Photomultipliers produced by SRS.