Minutes of the forward endcap EMC eZuce SRN meeting, 24th of April 2017, 14:00-15:00

Presence:

• Basel: Werner
• Bochum: Claudius, Fritz-Herbert, Matthias, Tobias T., Tobias H., Tom
• Bonn: Christoph, Ulrike
• Groningen: -
• Stockholm: -
• Uppsala: -
• Giessen: Hans, Markus
• GSI: -

Subunits

• Minor design change concerning fibre plug securing: Change from machined 'half-washers' secured by cylinder head screws to certain size standard washers secured by counter sunk screws
• The washers have enough play on the screw shaft to allow for an easy insertion of the fibre plug and guarantee a secure stop once the screws are tightened and thereby centering the washers:

• So there is no need for machining anymore as we can use readily available standard parts

Recovery LED cabling:

• For finishing the VPTT subunits currently under production we need a concept of connecting the recovery LEDs
• The LEDs need to be connected in series within a subunit, however a xtal-to-xtal connection within the subunit is very hard to realize mechanically as the cable chain would need to pass the single holes in the inserts and mountplates and soldering or plugging during xtal-insertion into the alveoles would be necessary.
• Like in case of the (parallel) HV and LV connections we would like to go for a connection of the single LEDs of the series chain on the Schmidt-board - Christoph sees good chances for finding suitable connectors and space on the boards. He will look for suitable cables, connectors.
• The VPTTs showed no increase of noise background operating close to the recovery LEDs, so the supply would need not necessarily be as refined as is the case for the APD subunits (capacitively blocking LED electrodes to ground), however a 16-LED-series chain has not yet been tested neither with VPTTs nor with APDs (all tests so far done with somewhat idealized setup of single LEDs supplied by ground referenced power supply): Such tests will be done as soon as possible.
• Hans suggested a much higher capacity ceramic capacitor (47 uF) to be used as RF/LF-shunt than what we used for our tests: Giessen tests show that at least the Barrel electronics (Apfel ASIC etc.) is more susceptible to LF-noise as from switching power supplies (some 10 to 100 kHz) than to RF-frequencies (e.g. digital bus traffic) which we see as the main noise contribution. High quality, low temperature suited capcitor material as x7r was suggested.
• Hans is somewhat concerned about the concept of capacitively shunting to a wire or screen connecting to ground potential on the Schmidt board. He fears to build up an antenna with this construction rather than shunting noise.

I2C bus cabling:

• From the 5 km of Bedea cable 3,5 (+) km are needed for the barrel slice, 200 m will go to the backward endcap and about 800-1000 m are left for the forward endcap I2C -cabling.
• Christoph expects this length to be sufficient for us (will check).

Xtal data base:

• Tobias T. gave an overview of the Bochum crystal data base, more input concerning the location of crystals is welcome.
• Crytur crystal numbering should not just start with 'no 1' but should at least contain some identifier as 'C' (respective data type is string...).

APD preamps:

• Some delay in APD preamp delivery due to wrong manufacturing of PCB boards (1,6 mm thickness instead of 0.8 mm).
• Delivery expected to start in June rather than April. This is fine with us and will not affect any subunit production schedule.