Minutes of the forward endcap EMC SeeVogh meeting, 23rd of May 2016, 14:00-15:00


  • Basel: Werner
  • Bochum: Claudius, Fritz-Herbert, Malte, Matthias, Miriam, Tobias, Tom,
  • Bonn: Christoph, Matthias, Merlin
  • Giessen: Hans-Georg
  • Groningen: Myroslav
  • Stockholm: -
  • Uppsala: -
  • GSI: -

APD preamps:

  • The test setup with a free running cosmics measurement on a vertically suspeded crystals with APD readout gives hard to interprete results due to the absence of a clear visible peak in the resultung cosmics spectrum
  • We agreed to bring the crystal - mounted to a subunit - to Bonn as there is the setup specifically designed for these measurements with the ability of triggering cosmics fully passing the crystal length, resulting in a more prominent peak
  • We will try to prepare the subunit and bring it on Friday or Monday to Bonn
  • For the time being we expect the necessary preamp gain for APD readout to be about three times lower than tested so far (~0.1 V/pC), estimated from beam data and comparison to VPTT readout
  • Werner will prepare four preamps with this extremely low gain and send it to Bochum for testing - he already tested this version in Basel and achieved stable performance
  • We try to test this preamps before the June-Meeting at GSI
  • Malte suspects the general ringing/oscillation problem of the APD preamps being influenced by the grounding scheme
  • In this context there was some confusion about the grounding layout of the different ISEG HV power suppliy versions: the 16 channel units are not channel wise floating as the 8 channel and VPTT units but have a floating ground common to all 16 channels!
  • Delivery of the VPTT preamps is delayed by about four weeks. They are expected to arrive end of June.

Read out electronics:

  • There was some discussion about the definition of thresholds:
    • Malte and Matthias remarked that the effective threshold is not the stated threshold as there are additional requirements to be fulfilled, i.e. a time over threshold constraint, before accepting a signal, effectively increasing threshold
    • Myroslav explained that the difference in thresholds is not that dramatic
    • He will report on the triggering mechanism in the KVI-firmware in detail on the upcoming GSI-Meeting in June
  • The four shaper versions have been tested:
    • There is a ringing in the high gain branches causing double peaking spectra
    • The factor between high and low gain branch is clearly lower than 16
    • The absolute gains of the branches are not properly adopted to our needs (2 V preamp output to 1 V (?) ADC input)
    • Linearity test with six different amplitudes done (okay)
  • Malte will prepare a brief report on this measurements and send it around

HV regulation:

  • Christoph presented some slides showing the integration of the HV regulation board to the patch panel board (sitting on top as piggy back board)
  • The HV regulation boards also acts as security lock for the signal U.FL connectors
  • A mock-up for installation feasibility test may be available the week after next week
  • A real version of the fully equipped HV regulation board will arrive at Bonn soon, tested there and then go to irradiation tests to Giessen

-- ThomasHeld - 24 May 2016
Topic revision: r2 - 2016-05-24, ThomasHeld
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