ELOG DESPEC

AIDA GELINA BRIKEN nToF CRIB ISOLDE CIRCE nTOFCapture DESPEC DTAS EDI_PSA 179Ta CARME StellarModelling DCF K40

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Fri Aug 20 14:33:24 2021

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> 
> 11:30 BNC PB-5 pulser polarity chnaged from positive to negative (using LOCAL control)
>       Swap BNC cables (top + bottom & left + right) from BNC PB-5 and Cooknell SA1 Sum Amp outputs
>       Switch Cooknell SA1 Sum Amp output from negative to positive
> 
>       Observe pulser peak of c. 15 ch FWHM for aida08 and c. 35 ch FWHM for aida14
> 
>       This probably indicates
>       - noisy Cooknell SA1
>       - problem with T and/or Lemo-00 cable between BNC PB-5 and Cooknell SA1
> 
> > Investigate noise situation of AIDA (no DSSSDs connected)
> > 
> > Figs 1-6: Waves, Pulser Peaks + Widths *before* any changes
> > - aida16 very noisy ASICS 1&2, normal ASICS 3&4
> > - back-side aidas (02,04,06,08) worse resolution than front-side
> > - high-frequency noise still noticeable in waveforms
> > 
> > Figs 7-8: Remove pulser in (from NIM rack) only
> > - no noticable change
> > 
> > Figs 9-10: Remove all pulser cables from adapter boards
> > - looks improved
> > 
> > Figs 11-12: HV Braid->GND Jumpers removed
> > 
> > Fig 13-14: All HV cables removed
> > - aida06, aida14 isn't updating
> > - very noticable improvement
> > 
> > Fig 15-16: Intermediate HV cables re-added
> > - signal worse in FEE64s with HV cables
> > - aida09, aida01, aida10, aida13, aida05, aida14 don't have HV interconnect cables, look good
> > 
> > Conclusion: We see noticeable improvements removing the interconnect cables between FEE64s.
> > 
> > Pulser widths now:
> > - aida14 (-ve amplitude) = 13.5 channels
> > - aida08 (+ve amplitude) = 40 channels (?)

Removed the T-piece between pulser and summing amplifier
pulser FWHM still ~30 channels - not the T-piece, probably summing amp

Checked the noise of HV and LV on battery DSO
- LV - no noticeable noise on any channel (< 5 mV rms)
- HV - noticable periodic signal (~100 kHz, 100 mV Vpp) on both core and braid channels, common to both
       independent of bias voltage 
       See figs 1-6 : 0V, 10V, 20V, 50V, 100V, 0V (high photo resolution) of bias voltage
                      AC coupled 1MOhm Ch1 = HV Core, Ch2= HV Braid, Math=Ch1-Ch2

Filtering on AIDA front end ~ 10 nF (gnd), 3 kOhm  (series) - low pass ~ 33kHz rolloff
100 kHz would be attenuated factor of 5 maybe - 20 mV signal - still quite high for ASICs
Try introducing additional inline filtering of maybe 3 kHz (1 nF gnd, 3 kOhm series) 
 Check on one DSSSD, if see improvement can migrate to adapter boards in new revision

Things to do:
TD:
 Inline filters
NH:
 Check same behaviour other N1419ET HV supplies
 Check line voltages from CAEN NIM bin

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