ELOG AIDA

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

AIDA

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Wed Nov 25 19:24:39 2015

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Powered system on and biased to +200V at room temp of 22.4oC. Leakage current of 3.37uA.
Waveforms very noisy and spectra dominated by low E noise. Upon taking a close look at front end found one of the kaptons to have broken a connection. Swapped it out for a spare.
Returned to same situation as last week. Peaks all have a shoulder at t_shape of 8us, but main peak has width ~80ch. Shorter shaping times lead to double peaking.
Removed FEEs from crate and properly seated adapter PCBs on Cu mounting block, with washers between plated part of PCB and allen screw.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; - &lt;0.4 ohm impedance betwee Cu mount block and washer/screw but ~20 ohms between screw and LEMO connector =&gt; 20 ohms between Cu mounting block and LEMO connectors
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; - plating around screw holes doesn't go anywhere.
Confirmed LEMOs are connected to ASIC ground (as they should be) on the Cu mezzanine block with &lt;0.2 ohm impedance between mezzanine Cu and LEMO connectors.
With adapter PCBs removed, Cu mezzanine blocks of separate modules still have impedance &lt; 0.3 ohm between them. How/why?
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; - found out MACB cables, power cables and network cables all connect the grounds of each FEE card/module. Was this expected? Does this cause us problems?
Swapped non-functioning nnaida12 for the former nnaida11 from the module featuring the other broken nnaida12 - all seems to work, although no waveforms are produced.
Very low impedance between ASIC grounds of FEE cards in same module.
To obtain a better ground connection between the ASIC grounds of separate modules, connected a thick braid to Cu mezzanine block of each. Operating at limit of multimeter so no noticeable difference in impedance. But...
With mezzanines connected and thick braid connecting HV and pulser at LEMO connectors, see the best waveforms so far; very little noise, some transients (attachments 1+2).
However, in nnaida14 waveform does not get back to baseline properly after a pulser event (attachments 2+3).
Despite very clean waveforms, still see double-peaking in spectra, although peak widths are fairly low (attachment 6).
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