08/02/16
Spoke to PJC-S -> Ethernet cables from FEEs to switch are all 4m Cat6.
System powered on with bias to detector of +200V and leakage current of 6.4uA at room temp 19.0oC.
Double peaking present again in nnaida11/12 -> individual peaks @ ~100ch FWHM with separation ~150ch @ 2us shaping time.
Double peaking also present in nnaida13/14 -> indiv peaks ~100ch FWHM and separation ~90ch.
Changing grounding had no effect.
Made ribbon cable with 2 separately shielded halves plus connecting Cu tape strip at FEE and + drain wire in contact with both halves - single peaks - widths of ~110-160ch.
09/02/16
Added conductive gasket to Cu mount blocks
- resistance between Cu and gasket ~0.2 Ohms (probe-to-probe = 0.16 Ohms)
- LEMO connector to Cu mount block ~0.35 Ohms
- LEMO to LEMO (between adapter PCBs) ~0.55 Ohms (connected by heavy duty Cu braid)
Powered system on. Bias of +200V and leakage current = 5.5uA @ room temp 19.5oC.
With gasket added and heavy duty Cu braid between mount blocks, pulser FWHM in nnaida11 ~ 62ch and in nnaida13 ~72ch at shaping time of 8us.
Investigated effect of shaping time on peak FWHM (avg width found from average of 1.(6,8,10,12).L for each FEE. (see attachments)
Shaping time (us) | nnaida11 | nnaida12 | nnaida13 | nnaida14
0.5 | 95* | 108* | 126* | 99*
1.0 | 82 | 116** | 130^ | 110**
2.0 | 68 | 83^ | 110^ | 92^
4.0 | 60 | 77 | 85' | 90
8.0 | 56 | 63 | 77 | 64
* = all peaks single and Gaussian looking
** = not all peaks Gaussian, some flat or sloped top
^ = double peaks, widths estimated from tallest peak
' = flat topped |