Photon Detection Efficiency Measurements of the VERITAS Cherenkov Telescope Photomultipliers after four Years of Operation

Abstract

The photon detection efficiency of two sets of R10560-100-20 superbialkali photomultiplier tubes from Hamamatsu were measured between 200 nm and 750 nm to quantify a possible degradation of the photocathode sensitivity after four years of operation in the cameras of the VERITAS Cherenkov telescopes. A sample of 20 photomultiplier tubes, which was removed from the telescopes was compared with a sample of 20 spare photomultiplier tubes, which had been kept in storage. It is found that the average photocathode sensitivity marginally increased below 300 nm and dropped by 10% to 30% above 500 nm. The average photocathode sensitivity folded with the Cherenkov spectrum emitted by particles in air showers, however, reveals a consistent detection yield of 18.9+/-0.2% and 19.1+/-0.2% for the sample removed from the telescope and the spare sample, respectively.

5 pages, 9 figures, submitted to JINST

Cited by in corpus (5)

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• The throughput calibration of the VERITAS telescopes
• Direct measurement of stellar angular diameters by the VERITAS Cherenkov Telescopes
• The Camera and Readout for the Trinity Demonstrator and the EUSO-SPB2 Cherenkov Telescope
• Studies of VERITAS Photomultipliers After Eight Years of Use