D. Škrk

The HERA-B RICH

Abstract The design issues and tests carried out with the ring imaging Cherenkov detector for the HERA-B experiment are reviewed. Results of on-the-bench tests of the employed photomultiplier tubes are reported together with the early commissioning measurements with the HERA proton beam.

Multianode photomultipliers as position-sensitive detectors of single photons

Tests of 2300 Hamamatsu multianode photomultipliers (1543 pieces of R5900-M16 and 762 pieces of R5900-M4) have been tested on the bench in order to evaluate their performance for use as position-sensitive photon detectors in the ring imaging Cherenkov counter of the HERA-B experiment.1 A weak and stable source of photons has been obtained by Cherenkov radiation of electrons from a 90Sr source in a quartz radiator. From measurements of the count rate versus high voltage, optimal high-voltage values have been obtained as well as a parameter (RQE) corresponding to the relative quantum e

PHOTON DETECTORS FOR THE HERA-B RICH

ciency. Distributions of the number of photomultipliers as a function of the optimal high voltage and as a function of the relative quantum e

Tests of a large area MWPC with a CsI photocathode

ciency are presented. The measured parameters are in good correlation with those provided by the manufacturer. The stability of the photomultipliers has also been followed over two years. The observed count rate decrease is consistent with the radioactive decay of 90Sr. ( 2000 Elsevier Science B.V. All rights reserved.

Aging and rejuvenation of a TMAE+methane multiwire photon detector

Abstract Results of tests of different position-sensitive photon detectors for the HERA-B RICH are given. It is observed, that the CsI-MWPC cannot be routinely produced and maintained with sufficiently high quantum efficiency and that the TMAE detector loses anode wire gain too quickly. The third candidate, the H-6568 Hamamatsu multianode PMT, seems to meet all the requirements necessary for photon detection in the HERA-B RICH.

Tests of photocathode quantum efficiencies using Cherenkov radiation of electrons from 90Sr

Abstract The relative quantum efficiency of several CsI photocathodes in an asymmetric multiwire proportional chamber has been measured. The photocathode surface of 24 × 24 cm 2 is divided into 7.5 × 7.5 mm 2 pads and the chamber is operated with methane at normal temperature and pressure and a gas gain of about 10 5 . During tests of the high rate performance (∼2 MHz/cm 2 ) of a smaller chamber (5 × 5 cm 2 ), an interesting time variation of the count rate has been observed when illuminating the chamber with constant UV light.

The performance of the HERA-B RICH at high track densities

A UV sensitive multiwire photon detector has been tested as a possible candidate for the HERA-B RICH detector. The main obstacle to using such a TMAE+Methane filled gas detector in a high rate experiment appears to be rapid aging in the form of prohibitive loss of chamber gas gain. A special circuit has been designed for heating the anode wires in-situ with elevated currents, thus evaporating the polymer deposits. Heating almost completely recovers the initial gain, but this rejuvenation is unfortunately of short duration. Nevertheless, the cells exposed to periodic heat treatments have an average gain considerably higher than the non-heated cells.

The physics potential of the HERA-B RICH

Abstract Cherenkov photons emitted by electrons from a 90 Sr source in NaF and quartz radiators, have been measured with Philips photomultipliers XP2020 and XP2020Q. On a logarithmic scale the pulse height distribution is linear, with the slope sensitive to the absolute value of the photocathode quantum efficiency integrated over wavelength. The agreement between measured and simulated pulse height distributions confirms the validity of the simulation procedure as well as the input data taken from the literature. For the XP2020Q photomultiplier our results support the data of Dorenbos and de Haas, who found that the quantum efficiency below 250 nm is higher than stated by the manufacturer.

THE RICH DETECTOR FOR HERA-B

Abstract The performance of the ring imaging Cherenkov counter (RICH) for the HERA-B experiment has been evaluated. The measured values of the basic parameters such as the number of detected photons per ring and Cherenkov angle resolution are found to agree with a priori estimates. Also at higher track densities, the detector is capable of identifying individual rings. Particle identification has been achieved by determining the momentum from tracks in the vertex detector and main tracking system, hits in the electromagnetic calorimeter and track directions as measured by the RICH.

Tests of photon detectors for the HERA-B RICH

Abstract The physics potential of the RICH counter of the HERA-B experiment is illustrated in several MC simulated examples. In particular, we discuss its performance as an auxiliary tracking device.