Minutes of the forward endcap EMC SeeVogh meeting, 28th of September 2015, 14:00-15:00


  • Basel: excused
  • Bochum: Cathrina, Claudius, Fritz-Herbert, Malte, Mario, Matthias, Miriam, Patrick, Tobias H., Tobias T., Tom
  • Bonn: Matthias
  • Groningen: Myroslav
  • Uppsala: Pawel
  • GSI: -

Crystal cover foil: Light yield vs. subunit orientation

  • As presented on the September Collaboration Meeting the single crystal light yield can be drastically reduced by touching to crystal cover foil (locally disturbing light transport by total reflection)
  • Recent measurements show and quantify this problem for the crystals in a subunit: Different orientation of the subunit results in single crystal light yield changes in the order of +-10%
  • Especially low light yield is observed for a vertical suspension of the subunit. Therefore the cosmics data point in the latest estimation of necessary preamp gain, which has been taken in this orientation, actually needs to be corrected to perfectly match the Bonn 2015 beam time data.
  • However, the precision is sufficient for the preamp gain determination and the preamps (three gain ranges for VPTTs) are ordered now
  • In order to prevent the narrow light yield distribution of carefully selected crystal-detector-preamp combinations from being spread we need to stabilize the crystal covering
  • Differing cover material is no option as this foil has by far the highest reflectivity and we need as much light as possible to be detected with respect to the low light yield of lead tungstate
  • Giessen reported form experience with shrinking tube fixing the cover foil
  • We will check if there is a shrinking foil available thin enough (in the order of 50 micrometers thickness) to just fill the remaining gaps around the crystals actually forseen for temperature sensors (the majority of crystals will not be equipped with sensors)


ADC boards:

  • There will be a workshop about handling the readout with the latest ADC boards prior to the next Proto120 Mami-beam time in December
  • The topic will be of interest for all subsystems (barrel, forward and backward endcap) and held in Giessen
  • The date for the workshop will be in the 2nd half of October, depending on availability of ADC boards (Pawel: 2 boards already available and shipped from Uppsala to KVI)
  • Stockholm will do tests of ADC/shaper boards on crystals with similar pulse shape but higher light yield than lead tungstate (presumably LaBr)
  • The higher light yield of LaBr offers the use of radioactive sources ('invisible' to lead tungstate)
  • Stockholm will also do tests using pulse generators, but measurements including photo detectors and preamps (noise) are preferred (Myroslav)
  • Concerning noise and s/n one has to carefully calculate the light equivalent (LaBr, radioactive source vs. lead tungstate, Panda-energies, crystal dimensions...)
  • Myroslav presented a revised, light weighter structure of the ADC crates and discussed cooling and mounting issues: Do we use a leakless underpressure system or use one solid pipe with 'arbitrary' pressure running through all crates and be connected outside only?

- ThomasHeld - 30 Sep 2015
Topic revision: r1 - 30 Sep 2015, ThomasHeld
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