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

Presence:

• 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