An ultra fast, low power readout chain for single photon sensitivity with multi-anode photomultiplier tubes for the RICH upgrade at LHCb

An upgrade proposal for the LHCb RICH detectors at the Large Hadron Collider at CERN is being developed at the INFN section of Milano Bicocca, based on multi-anode photomultiplier tubes. The application requires the fast readout of Cherenkov rings of photons, with single photon sensitivity, at an event rate up to 40 MHz. The proposed readout chain is tailored for the R7600 multi-anode photomultiplier tubes from Hamamatsu, which proved to fit the single photon sensitivity requirement. The readout electronics for each pixel will be composed of an analog pulse shaper, a binary discriminator and additional digital circuitry to count the pulses. A prototype of the analog shaper was built with commercial discrete transistors in Silicon–Germanium (SiGe) Heterojunction technology. The tradeoff between response speed and power dissipation was investigated; and power as low as a few mW per channel could be achieved with response times of the order of one nanosecond. Furthermore, noise and jitter were evaluated, showing very good performances of the prototype.