Abstract
The LHCb Ring Imaging Cherenkov (RICH) counters use the pixel Hybrid Photon Detector (HPD) as a photo-sensitive device. Photo-electrons are produced in a semi-transparent multi-alkali photo-cathode (S20) and are accelerated by a voltage of 20 kV onto a pixelated silicon anode. The anode is bump-bonded to the LHCBPIX1 pixel readout chip which amplifies and digitises the anode signals at the LHC speed of 40 MHz. Using a demagnification of five, the effective pixel size at the HPD window is 2.5 × 2.5 mm 2 . Over the course of 18 months, 550 HPDs will undergo a quality-assurance programme to verify the specifications and to characterise the tubes. The tested parameters include the threshold and noise behaviour of the chip, the response to light emitting diode (LED) light, the demagnification of the electron optics, the leakage current and the depletion of the silicon sensor, the quality of the vacuum, the signal efficiency and the dark count rate. Results of tests of the first nine HPDs of the final design are presented and compared to the specifications.
Highlights
The LHCb experiment [1,2] is a single-arm spectrometer for precision measurements of CP-violation in the decay of B-mesons produced in 14 TeV pp-collisions at the LHC collider
The Ring Imaging Cherenkov (RICH) detectors will be equipped with 484 Hybrid Photon Detector (HPD) in total
Apart from a few exceptions the performance matches or exceeds the design specifications. Even in those cases where the specifications are missed, the HPDs are still suitable for use in the LHCb RICH detectors
Summary
The LHCb experiment [1,2] is a single-arm spectrometer for precision measurements of CP-violation in the decay of B-mesons produced in 14 TeV pp-collisions at the LHC collider This requires an excellent separation of p- and Kmesons over the momentum range of 2–100 GeV. RICH 1 covers the phase space of lower momenta and larger scattering angles ranging from 2 to 60 GeV and 25 to 250(300) mrad in the non-bending (bending) plane, respectively. It operates in the fringe field of the bending magnet. Eisenhardt / Nuclear Instruments and Methods in Physics Research A 565 (2006) 234–240
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