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P

Photo Multiplier Tube

    A photomultiplier is a device which detects single photons by producing a cascade of photoelectrons resulting in an electrical signal. Detailed information can be found in the Wikipedia article.

    In the student and Cosmic@Web experiments different PMT types are used which have been employed before in experiments at CERN and DESY:
    • Kamiokannen detector: 1 PMT type S.R.C. Laboratories inc. Nr.: S75B01 with 10 dynodes.
    • LIDO detector: 1 PMT type Philips XP2020 with 12 dynodes.
    • Muon detectors on the “Polarstern” and on the Neumayer III station: 4 channel PMT type Hamamatsu R5900U. 4 channel means that one tube (30mm x 30mm) contains 4 independent PMTs, 15mm x 15mm sensitive surface each.
      the old detector (2012-2016) has one PMT, where only 2 channels are used. 4 fibers of the scintillator are connected to channel 1, the other 4 to channel 3. The coincidence requirement reduces wrong signals due to electronics noise and other influences.
      The new muon detector (since 2017) contains 4 scintillator plates and two 4 channel PMTs. One half of the fibers of the 4 scintillators go to one PMT, the other half goes to the second PMT. Also here the coincidence condition is required for a signal of every scintillator.
    • Trigger Hodoscope: One detector plane contains 4 scintillator segments. Also here the fibers of one segment are divided into two groups (8 fiber groups in total). Every detector plane has one 16 channel PMT, where only 8 channels are used.