Minutes of the forward endcap EMC Vibe/eZuce meeting, 26th of August 2019, 14:00-14:50
Bochum: Matthias, Thorsten, Tom
Bonn: Christoph, Christian
Cosmics measurment results of the first 16-crystal APD submodule:
The 12 GeV Panda FWEC EMC single crystal energy maximum is probably detetcable with all channels (detailed analysis follows)
The spread of channel responses (inter crystal and between APDs on one crystal) is as expected and acceptable
Second APD submodule is going to cosmics test stand soon
Noise figures of both submodules comparable in terms of sigma, but a closer look to the shape (non gaussian contribution) is needed as this indicates the occurance of pickup noise
Annealing LED cabling appears to be short (probably not too short but close to limit) - does this come from cable routing through the aluminum tube (as tested for one of the two submodules built)? Checked: no!
The signal labeling/color coding should be improved: ideal would be an omission of the shrinking tube as it hinders cabling to the PCB and preferred is a labeling that does not move along the signal cable
We therefore will change to the newly tested paper cable labels that we print on our own and that include the color coding by colored prints
Christian presented measurements of the outer dimensions made on 13 VPTT submodules
He presented results of scans of the alveole surface
All submodules turn out to be between 1.6 and 2.2 mm longer than expected from an existing CAD model
These numbers agree with the caliper measurements made on the submodules after finishing in Bochum
It is not yet clear whether the CAD model is outdated (maybe does not contain the capsules?)
Is the spread of elongation (1.6 - 2.2 mm) compatible with the thickness variation of the VPTT capsules?
Christian also presented x-ray images of a submodule showing about 0.4 (0.6) mm free space between crystal front faces and carbon inner (outer) fibre front
Does the difference of (1.6/2.2 - 0.6) mm = (1 - 1.6) mm correspond to the VPTT capsule thicknesses?
We therefore need to measure the resulting maximum distances of submodules (corners) to the backplate (minimum free space to the front lid)
Has there been a redesign (decrease of height) in the interface pieces in order to account for the elongation of the submodules by the introduction of the capsules?