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The ring imaging Cherenkov (RICH) detector at LHCb is now read out by hybrid photon detectors. In view of its upgrade, a possible option is the adoption of the flat-panel photon multiplier tube (PMT). An important issue for good reconstruction of the Cherenkov rings is a negligible level of crosstalk. We have experimentally studied the crosstalk from the 16 × 16-pixels Hamamatsu H9500 PMT. Results have shown that, for the single-photon response, the statistics tied to the small number of electrons generated at the first dynode of the PMT chain (a few units) leads to a number of crosstalk signals that are a small fraction of the fired pixel. With the H9500, in a Cherenkov ring, only one or two pixels are expected to generate crosstalk. As a consequence, crosstalk cannot be considered a limit in the use of the H9500 for the upgrade of the RICH at LHCb. © 2010 IEEE.

We present the protection system for the monitoring circuitry of the 20 kV high-voltage bias for the Hybrid Photon Detectors of the Ring Imaging Cherenkov detectors of the LHCb experiment. The protection system buffers the voltage lines, attenuated by about 12700 V/V in normal operating conditions, and limits the output voltage excursion to the ADCs of the monitoring system to a safe range (between -2.5 V and +5 V) in case of discharge. The circuit has been designed and tested to be radiation tolerant under the expected working conditions of LHCb. Results show that the protection boards are fully adequate for the whole LHCb lifetime.

We present our circuit solution for the second stage of the front-end readout of an array of mu-bolometers, cryogenic detectors having Si or Ge thermistor as sensing element. The front-end consists in a cold unity gain buffer stage (with single sided input connection) followed by a room temperature second differential amplifying stage. The optimization of the input transistor of the set-up has been determined by comparing the performances obtained applying a low pass filter or the optimum filter at output of the front-end. To minimize EMI interference the output of the cold buffer stage and its ground reference signal, taken close to the buffer itself, are readout in differential way from the second stage. To minimize noise, in our circuit solution the differential amplifier has an input stage with a noise that is 1.6 times smaller (1.27 times smaller if we consider the Square Root noise, SRn) than in a standard differential solution. Since the series noise is inversely proportional to the Gate area, to further reduce the noise the input JFET of the second stage has a large Gate area, of about 1 nF, and a very small feedback resistance. The performances of the presented second differential stage amplifier are about 0.194 (nV)2/Hz (440pV/radicHz for the SRn), and a figure of less than 1.21 (nV)2 /Hz (or 1100 pV/radicHz SRn) at 1 Hz. Parallel noise is completely negligible over the ranges of the expected output impedances of the cold stage. Dynamic input impedance is a few tens of pF. The voltage gain is 500 V/V, AC coupled down to 80 mHz

We present our circuit solution for the implementation of a very simple temperature stabilization system of an array of 62 large mass bolometric detectors, CUORICI The implemented instrument exploits one of the front-end channels to close the feedback loop between a thermistor and a heather, both of them located on the detector holder in the refrigerating system. Avery compact layout was developed that avoids any possible presence of EMI interference, which would otherwise be introduced if a commercial instrument were adopted. The stabilized temperature is obtained exploiting the offset correcting circuit of the remotely programmable front-end channel to autogenerate the reference operating point for the feedback loop. Thanks to the adopted configuration, the instability of the cryogenic apparatus, which induced a drift corresponding to about 50 keV/day, was reduced to less than about 0.5 keV/day. To model the system behavior, we have reformulated the bolometer theory of operation using the concept of a feedback network. The obtained results will be shown. © 2005 IEEE.

We present the characterization of the static and low-frequency noise performances of some commercial Si-Ge heterojunction bipolar transistors from 4.2 K to room temperature. The low injection region of operation was considered in view of their possible applications for the readout of array of cryogenic detectors.

We present a very precise and stable pulse generator which serve to calibrate an array of large mass bolometric detectors for a very long time data taking. The realized instrument is characterized by the presence of multi-outputs and is completely programmable in pulse width and amplitude. Triggering is allowed with a dedicated line. Although featuring ppm//spl deg/C stability, it was realized exploiting commercial devices, obtaining a very cheaper solution.