Minutes of the forward endcap EMC eZuce SRN meeting, 18th of July 2016, 14:00-15:10


  • Basel: Werner
  • Bochum: Cathrina, Claudius, Fritz-Herbert, Malte, Matthias, Miriam, Patrick, Stephan, Tobias H., Tobias T., Tom
  • Bonn: Christoph
  • Giessen: Hans-Georg
  • Groningen: Myroslav
  • Stockholm: -
  • Uppsala: Pawel
  • GSI: -

APD subunits:

  • Summary of new insights into the '1:2 problem' (preamp output ratio of 2 of the two APDs of one crystal, seen on half of the crystals)
    • The unit showing both ratios of 1:1 and 1:2 in one cosmics run was found to be completely decoupled from the crystal
    • Looking at the event numer (aka time) one sees that the ratio started to be 1:2 at the beginning and soon turned to 1:1
    • A 'pressed coupling' of the APD unit against the crystal with the remaining silicon pad still attached to the APDs gives a read out ration of 1:1
  • It seems that the 1:2 ratio problem is a coupling problem even though we are far from fully understanding what is going on
    • Does a perfect adhesive coupling give twice the light output of a coupling with the silicon just pressed to the crystal? (Measurements explicitly adressing this question are going on)
    • Why do we see ratios of 1:2 directly after a fresh glueing?
    • Why does it seem there are only tight coupled or totally decoupled APDs (no ratios in betwwen 1:1 and 1:2)? (There seem to be no 'partly' (de)coupled APDs)

APD preamps:

  • There are about 170 VPTT preamps of one gain ready and tested that will be sent this week or next week
  • There are also 32 APD preamps of the latest version ready to be sent

Radiation map:

  • There was some discussion on how to proceed with getting detailed, realistic radiation maps
  • It was agreed that Karoly, who started working on this, should go on with work on this topic
  • Pawel has been in contact with Karoly as he needs information for further tests, awaits approximate values this week

ADC boards:

  • Pawel needs information about the measured ratio between high and low gain in order to modify for a ratio of 1:16 (Malte will provide the Bochum results)
  • We decided to leave all four different shaping constants implemented to the boards for the time being as we need to closer look at pulse shape stability
    • Myroslav pointed out that pulse shape stability is an important issue in the deconvolution of pile up events as the algorithms rely on stable shapes

HV adjustment boards:

  • Christoph showed pictures of the latest PCB layouts
  • There are mock-ups in the works to mechanically test for connectability, mounting sequence etc.
  • For I2C cabling the barrel 'Bedea' cable seems to be probably not suitable (too tiny), Christoph will ask for a suitable cable w/ two differential lines plus one power line in a 3...4 mm overall diameter cable

HV module repair:

  • We will send three broken HV modules to ISEG and await offers for repair.
  • We will continue testing until all HV modules currently in Bochum have been screened

Irradiation of 'inner endcap wall' material candidates:

  • Hans reported of 'plastic smell' at the end of an exposure to 1000 Gy of four different foam test pieces
  • It is unclear what piece caused the smell
  • He will send back the pieces to Bochum for evaluation of material deterioration
  • Once we decided for a material we will need to test it at twice the dose as 1000 Gy may be a too short estimate for the inner walls
-- ThomasHeld - 21 Jul 2016

Added details regarding HV module repair -- TobiasTriffterer - 21 Jul 2016
Topic revision: r2 - 2016-07-21, TobiasTriffterer
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