ELOG DESPEC

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

DESPEC

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Entry time:	Sat Mar 29 11:28:37 2025
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> Investigating AIDA noise with a TA041 differential probe and oscilloscope > > AC Mains (DESPEC platform AC, L-N) > Probe attentuation = 1:100 > > Fig 1: Main AC waveform [X: 5ms/div, Y: 100 V/div] > Fig 2: Zoomed in at peak (20 V FSR, any less and the waveform clipped) [X: 10us/div, Y: 20V/div] > Fig 3: Longer time base and FFT of 0-5 MHz. No significant frequency harmonics noticed [X: 5ms/div, Y:20 V, FFT X: 500 kHz/div, Y: 10 dBm/div] > > No significant noise or distortion present, fully within any AC specification. > Note that at the moment there is almost no load on AC > Equipment on on DESPEC rack: AIDA NIM, AIDA Raspberry Pis, bPlas PC (+ WR) + 2x DESPEC NIM crates > No autofill, VME crate or detectors > All big machines at GSI (SIS, FRS) off (suspect pumps are on) > > Ion catcher not on (I think under repair) > > - > > FEE PSU studies > Probe connected to 5V exposed power pin on FEE64 (+v) and to grounding crimp on FEE64 (-v) > No adapter board connected > Attentuation = 1:10 > > > Fig 4: FFT when FEEs are off - essentially probe+scope noise [X: 5ms/div, Y: 100 mV/div, FFT: X: 500 kHz/div, Y: 10 dBm/div] > Fig 5: FFT when FEEs are on - notice 1.4 MHz peak in FFT, also seen on ADC waveform readout before (fig 6) [X: 5ms/div, Y: 100 mV/div, FFT: X: 500 kHz/div, Y: 10 dBm/div] > > Fig 7: 500 ns/div 5V output on FEE, single FEE on the PSU [X: 500 ns/div, Y: 100 mV/div] > > Note average max voltage is 5.31 V (power on) and ~ 70 mV "peak to peak" -might be from probe/scope? > > Also see voltage changes with FEE power draw: > > Power on : 5.45 V (different scale to above) > SETUP ran : 5.51 V > FADCs off : 5.86 V > ACQ Go: : Unchanged; ASIC threshold 0xa: Unchanged > > Also check situation on a fully loaded PSU (8 fees connected and powered on) > > Power on: 5.29 V (fig 8) > SETUP ran: 5.36 V (fig 9) > FADCs off: 5.64 V (fig 10) > > All X: 500 ns/div, Y: 100 mV/div > > Both cases observe voltage rises as current draw drops (as expected for voltage drop along a cable) > > Noise on 'scope seems to get slightly worse with reduced current (and higher voltage) > > No sign of strong 100 kHz noise as seen in ADC traces beforehand > > Todo: > > - Check -6V and 7V rails > - Check 5V and noise when front-end card is added and pulser/HV connected > - Check between two FEE64 grounds > - Check direct out of PSU vs ground to see if 1.4 MHz appears on PSU side or FEE64 side > > - > 11.10.22 Updates > > Attachement 11 - 5V PSU on upper PSU with no FEEs attached whatsoever. No 1.4 MHz (on FFT) but clear low frequency beats from switching - presumably low/no load behaviour > > Attachement 12 - 5V PSU on aida12 with 8 FEEs on PSU. Longer time base to allow lower frequencies in FFT. 1.4 MHz switching spikes visible but nothing around 100 kHz region > > Attachments 13-16: 5V PSU on aida12 at 20 mV/div vertical and 1, 0.5, 2, 5 us/div horizontal respectively > > 12.10.22 Updates > > Attachment 17: -6V PSU on aida12 with 8 FEEs on PSU. 2 us/div timebase. 20 mV/div amplitude > Attachment 18: 10 ms timebase and FFT > Average voltage: -6.21 V > > Attachment 19: 7V PSU on aida12 with 8 FEEs on PSU. 2 us/div timebase. 20 mV/div amplitude > Attachment 18: 10 ms timebase and FFT > Average voltage: 7.46V > > Measurement between AIDA12 ground and Reference ground/copper bar > +ve (red probe) attached to copper bar at ground point (not strong connection at present) > -ve (black probe) attached to ground crimp on aida12 (connected to cooling plate) > aida12 no adapter board connected: connections are PSU, Ethernet, HDMI and TTY only > > Attachment 21: 5 us/div 100 mv/div waveform, big oscillations present. Not seen before FEEs turned on (8 FEES, 1-7+12) > Attachment 22: 10 ms/div for FFT, sharp peak at exactly 100 kHz observed... > > > Attachment 23: Between 5V PSU (+ve) and 19" rack (-ve) with no FEEs connected to PSU > See strong 100 kHz oscillations too, note that voltage isn't 5V as PSU is floating w.r.t. ground > Looks to be common mode noise (on both 5V and Return of PSU) > > Attachment 24: Same as 21 but using thick crocodile clips on probe to ground and aida12. Noise is attenuated but still present Encoding: HTML ELCode plain Suppress Email notification

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