Minutes of the forward endcap EMC SeeVogh meeting, 9th of May 2016, 14:00-14:45

Presence:

• Basel: Werner
• Bochum: Fritz-Herbert, Malte, Matthias, Tom
• Bonn: Christoph
• Groningen: -
• Stockholm: Karoly, Markus
• Uppsala: Pawel
• GSI: -

APD preamp:

• Recent calculations based on beam time data and comparison with VPTT readout led to the unpleasant result of needing a preamp gain about three times lower than the latest test preamps
• This intensifies the ringing/oscillation problems with the APD preamps - is it possible to stay with the current preamp design and further reduce gain while getting the amps stable?

Read out electronics:

• Malte reported about the problem of not having the possibility to pre-trigger in the low gain branch, so one cannot determine a baseline there
• Double peaks occur in the high gain branch when for example charge injection is used -> biasing even if we record waveforms. The cause is an oscillation ('hum') in the high gain branch modulating the waveform.
• Pawel: original Uppsala firmware had all those feature necessary to efficiently set thresholds etc.
• Obviously the KVI firmware/feature extraction does not
• Markus/Pawel measured linearity of the ADCs: "okay"

HV regulation:

• Current measurement capability can be realized using four transistors and some resistors which is quite space consuming
• After some discussion we decided to skip the current measurement capability and only go for an HV regulation (setting and measuring)
• Christoph will prepare a modified patch panel board with attached piggy-back HV regulation board to test mounting on the backplane in Bochum