Performance study of new pixel hybrid photon detector prototypes for the LHCb RICH counters

A pixel hybrid photon detector (HPD) has been developed according to the specific requirements of the LHCb ring imaging Cherenkov counters. This detector comprises a silicon pixel detector bump-bonded to a binary readout chip to achieve a fast 25-ns readout and a high signal-to-noise ratio (SNR). The detector performance was characterized by varying the pixel threshold, the tube high voltage, the silicon bias voltage, and the determination of the photoelectron detection efficiency. Furthermore, accelerated ageing and high pixel occupancy tests were performed to verify the long-term stability. The results were obtained using Cherenkov light and a fast pulsed light emitting diode. The results of all measurements agree with the expectations and fulfill the design goals.