Silicon PhotoMultipliers (SiPM) are a type of solid-state detectors and they are installed at the end of every fibre mat. When an ionising particle excites the fibres, light is emitted and propagates through the fibres. The goal of the SiPM detectors is then to convert the light signal into an electronic signal.
The SiPMs are segmented into miniature channels that can be read out individually. The total number of channels of the whole SciFi detector is about half a million. SiPMs have a fast signal, an extremely good sensitivity to a low light signal and provide a high photon detection efficiency over a large wavelength range that matches the fibres emission spectrum. They are produced by the company Hamamatsu in Japan.

The LPHE is strongly involved in the R&D development, qualification and quality assurance of the SiPM detectors.