Minutes of the forward endcap EMC eZuce SRN meeting, 19th of December 2016, 14:00-15:30

Presence:

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

Shaping/Filtering:

• Malte reported about the strategy of having different filtering for triggering and signal treatment
• 5th order filtering might be enough for triggering (guess from Matthias)
• S/N numbers not yet available, will be retrieved later on and shown in a future meeting

ADC Papers:

• There are currently two papers in the pipeline:

1. A hardware related one (Pawel), focused on ADC and communication
2. An irradiation effects related one (Stockholm), focused on FPGA performance

APDs:

• Hans presented raw data vs. fit data APD characteristic curves derived from GSI PSL data
• The precision of the fits is unknown, no errors are given by PSL
• A 0.1 V precision is needed for matching, the deviation however seems to be rather in the order of 1 V
• Suggestion/question: why not just interpolate linearly to needed gain from measured data? (That is exactly what we do in BO...)

Capsules:

• For the start of the VPTT subunit production the only open questions concern the recovery LED mounting
• Is it electrically feasible to place the LED besides the photo detector in terms of noise introduction? (Measurements done, analysis ongoing)
• Results of the measurements:
  • Results of the measurements:
  • We placed a calorimeter subunit equipped with 2 VPTT units and 2 APD units in a colling chamber. One VPTT is equipped with a blue flat-head LED (diameter: 2mm). The LED is placed in the direct vicinity of the VPTT and facing the PWO crystal, as it is foreseen for the annealing of radiation damages.
  • To estimate the severity of possible pick-up noise due to the LED cabling, different scenarios were tested, e.g. open wires at the LED, wires connected to a lab power supply, and so on.
  • Below you can find noise histograms of the VPTT with the LED (VPTT1), the neighboring VPTT (VPTT0) and a neighboring APD.
  • All measurements were done using a high gain channel of the most recent PANDA EMC digitizer (ADC_64k), which is equipped with four different shaping options. Here, the option with the shortest shaping time has been chosen for comparison, since the effect of pick-up noise should be most severe in this case.
  • Conclusion:
  • The RMS of the noise is 15+-1 channels for both VPTT units (uncertainty caused by reproducability of the measurements in a period of several days) for all scenarios. No significant increase of the noise or additional pick-up noise due to the additional LED were observed.
  • For the neighboring APD unit, no change in the noise figure was observed (RMS: 23+-0.5 channels)
  • -- MalteAlbrecht - 10 Jan 2017
  • 
• Do we manually modify the existing capsules to allow the LED mounting? Christoph guessed the price of all capsules (incl. APD ones) to 5000 EUR (which was confirmed later on), so we will just modify the existing VPTT capsules