New Kapton PCB design (2x 0.45m + inter-connecting PCB, no ground plane layers) under test with small system in T9.
3 cables modified to remove ground connection.
When just connected to system and BB18 2998-20, with no additional grounding or shielding of the cables
and bias of +200V (leakage current +6.2uA, ambient temp +27 deg C) to nnaida14, we observed average pulser peak widths
of ~250ch FWHM
Waveforms were just noise.
Added heavy duty copper braid between adapter PCBs, the small metal box for the detector and Cu tape and drain wire to the kapton connected to nnaida14.
This reduced the peak widths to ~160ch FWHM
Adding grounding between the adapter PCBs and the NIM bin chasis increased the peak widths.
Waveforms for nnaida11-13 remained unchanged, but expected (albeit noisy) traces could be seen for nnaida14).
------> Patrick: with ASIC1 waveforms for all nnaida turned on, we found they would occasionally stall for some. e.g. of 4 being observed, upon update, only 1 or 2 actually would. Stop-Go did not resolve this. Load/check ASIC resolved issue.
nnaida14 developed double peaking of pulser peak.
Note waveforms exhibit significantly faster risetime than previous Kapton PCB variants => lower C, as expected |