Search for noise sources � Nuno Barros FNAL, Feb 24, 2016 1
Notes • FEMB8-11 has not been extensively tested as 2 ASICs show to be current limited (drawing 1.5 A / max) � • I’m writing a small report on all tests performed over the last 2 weeks (~2k runs taken) 2
Reproducible noise situation • Turn on the ASICs with ~30 s interval � • Spikes in power observed each time • FEMB15 and FEMB12 often induce an unrecoverable spike (run with noise) 3
Reproducible noise situation • Turn on the ASICs with ~30 s interval � • Spikes in power observed each time • FEMB15 and FEMB12 often induce an unrecoverable spike (run with noise) • If ASICs are powered “quickly” one after the other, the noise situation occurs less often • Seems to suggest some capacitance in the system 4
Related observations • Once noise is induced by FEMB12-15 it spreads over the whole detector • Tests tried: • Induce noise in FEMB12-15, take a run and then turn on FEMB0-3 • Repeated with FEMB4-7 and FEMB12-15 • Only FEMB12-15 seems to be induced into noise by the “spaced” powering up • Tried FEMB0-3 and FEMB4-7 5
Other tests • Take data with different ASIC configurations (gain and shaping time) • Sometimes when changing the configuration the runs would become noisy. • No particular pattern observed • Most likely related to the auto configuration of the ASICs every time the DAQ is initialized (and the related spike in the power that is observed) • Take data with only drift voltage for long period (about 8h) • No problems • Take data with only bias voltage for long period (about 4h) • No problems • But detector became noisy when ramping up the drift voltage 6
Changes in power during normal operation Initialize Start run 7
Curious observation • Managed to recover from a noise condition twice • Powering off FEMB14 8
Next steps • Keep testing how to induce the noise • Look for other noise sources • This does not explain everything • Try to understand whats going on with FEMB12-15 • Tests done so far show this is consistently the source of noise. 9
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