Minutes of the forward endcap EMC eZuce SRN meeting, 10th of October 2016, 14:00-15:05


  • Basel: Werner
  • Bochum: Cathrina, Claudius, Malte, Miriam, Patrick, Tobias H., Tom
  • Bonn: Christoph, Matthias, Merlin
  • Groningen: Myroslav
  • Stockholm: -
  • Uppsala: Pawel
  • GSI: Holger


  • Crystal with 2-APD-readout and test glueing using special Dow Corning primer fluid is still running temperature cycles (30 something) since weeks and still seems to be firmly coupled (read out ratio 1:1)
  • What is missing is a test of the primer concerning optical transparacy and radiation hardness
  • Test pieces (radiation hard glasses) are prepared and are still curing in Giessen where the missing measurements will be carried out
  • Further tests of different glueing techniques (e.g. pressure application) ongoing (time consuming because of curing), comparison of necessary torques to remove couplings after several temperature cycles

Forward endcap assembly frame:

  • This is the massive steel frame supporting the full forward endcap (including its instrumented aluminum frame) during assembly and COSY data taking in Juelich as well as on the final transport to Darmstadt
  • There was a meeting Monday morning at a mechanical engineering company in Herne with the Juelich engineers involved
  • After detailed discussion about the construction and a survey of the workshops we are convinced the company is well suited to do the job
  • The company assured us to be able to finish the work within this year

Cosmics measurements at Bonn:

  • Matthias presented results of the measurement of the test subunit equipped with the latest ringing-free APD-preamps and glued using Dow Corning primer
  • There are two crystals in this subunit read out by two APDs each
  • Crystal 1 behaves as expected: very similar preamp output signals with the correct gain-200 bias voltages applied
  • Crystal 2 shows a read out ratio of about 4 between its two APD read out channels
  • Matthias will dissassemble the subunit to look for the cause of the problem
  • Malte will compare the resulting output signal heights of the read out of crystal 1 to the ones derived from latest Bonn beam time data
  • Once we get consistent results (output signal height vs. deposited energy, concerning preamp gain) we will be able to definitely tell the APD preamp gain needed for mass production

Positioning of VPTTs in forward endcap:

  • Merlin gave a talk about the distribution of VPTTs in the forward endcap with respect to B-field gain loss data measured in Bonn
  • B-field at VPTT electrodes position varies between 0.95 T and 1.05 T (mean value 1.009 T)
  • Angles between tube axis and B-field lines less than 4 degrees for all positions -> only look to magnitudes of gain loss, no angle dependence loss to be considered
  • Sorting for equal response considering gain, B-field gain-loss, SKB (Hamamatuss blue sensitivity index) using a Hungarian algorithm results in a distribution clearly smaller than the one derived by Tobias H. by 'hand sorting' earlier
  • Still need some time to investigate the broad disribution base below the needle-like peak
  • A further step would be the inclusion of light yield values of the 800 most radiation hard crystals that will go to the VPTT equipped subunits (Claudius and Tobias H. will provide a list of crystals and its respective values)

Serial adapter slow control chip:

  • Holger attended the meeting intending to update his work on studies of the concept of a 'serial adapter chip' for the EMC
  • Work is originated by Barrel needs: unification of slow control of APFEL asic and HV trimming circuitry
  • It is still to be discussed whether the forward endcap will benifit from the use of this chip (time, money, fail safety, cabling amount) as we do not have to communicate to read out front-end
  • Due to absense of Hans, Matthias, Fritz-Herbert we postponed Holgers update to a later date, probably the next Barrel eZuce meeting Monday, 17th, 3:30 pm

ADC boards:

  • Malte reported to have measured the high/low gain ratios to be okay (factor of 16)
  • However, the different shaping time channels show different input voltage ranges - the higher the shaping times the earlier the channels clip
  • Pawel will provide information needed to modify the differently shaping channels to equal input range
  • Myroslav still waits for waveform samples of the different shaping time channels from Bochum which will be provided once the board has been modified accordingly

-- ThomasHeld - 12 Oct 2016
Topic revision: r2 - 2016-10-13, ThomasHeld
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