uw engineering dom studies kael hanson university of wisconsin – madison lbnl dom workshop 23 july...
TRANSCRIPT
UW Engineering DOM Studies
Kael HansonUniversity of Wisconsin – Madison
LBNL DOM Workshop 23 July 2003
23 July 2003 LBNL DOM Workshop 2
What Testing was Done?
• Guiding principle“Attempt to carry out measurements and see how DOM behaves as a data acquisition platform then follow our noses.”
• Initial measurements desired:– Phototube gain– Peak-to-valley– Phototube noise (not yet /w/ DOM)
• These measurements implied a priori characterization of DOM analog F.E.
• Summary of measurements captured in Engineering DOM Tests document.
23 July 2003 LBNL DOM Workshop 3
DOMs Under Test (DUTs)
• UW now has 12 DOM-MBs:– 5 in ‘active’ DOMs (XE3P0001-0005)– 6 in DOMs awaiting testing– 1 DOMMB in use by NK for HV base tests
• 2 DOMMBs returned to LBNL because of hardware problems:– 1 flash RAM failure– 1 CPLD failure (could not program)
23 July 2003 LBNL DOM Workshop 4
DUT Configurations
Recording Date
DOM ID DOM MB ID BASE PMT SPHERE
7/9/2003 XE3P0001 0001-3c62-7f13 EMCO AA0036 683815/29/2003 XE3P0002 0001-3c62-718f ISEG AA0038 683777/16/2003 XE3P0004 0001-3c62-7dac ISEG AA0032 683627/16/2003 XE3P0005 0001-3c62-71db EMCO AA0037 68356
• Currently all 4 above DOMs running in chest freezer at PSL
• XE3P0003 is in freezer at Chamberlin undergoing analog tests
• Full DOM Work-in-Progress table maintained by Jim Hoffman
23 July 2003 LBNL DOM Workshop 5
ATWD Pedestal Study
• Purpose– Monitor system electronic noise– ATWD gain calibration
• Procedure– Set ambient temperature to -20 ºC, …– Set FE bias to various levels– Acquire CPU-triggered ATWD shots
23 July 2003 LBNL DOM Workshop 6
FE Gain – ATWD Channel 0
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ATWD Sample
ATWD Counts
ATWD Channel 0 (718F)
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Bias Voltage (Volts)
<ATWD>
ATWD Channel 0 (5th bin) Gain Curve (718F)
Clamping amplifier in ATWD ch0 introduces nonlinearity in analog FE!
23 July 2003 LBNL DOM Workshop 7
FE Gain – ATWD Channel 1
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ATWD Sample
Pedestal
ATWD Channel 1 Pedestal vs Bias Voltage
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Bias Voltage (Volts)
<ATWD>
ATWD Channel 1 (5th bin) Gain Curve (718F)
No clamping amp – linear but ATWD overflows around 1 V – incorrect ATWD tuning parameters here or intentional behavior?
23 July 2003 LBNL DOM Workshop 8
FE Pedestal/Gain Calibration Proposal
• If you take delta between 5th and 1st curves on previous plot, you would naively expect a flat line.
• Resulting line is not flat – features persist – do we need separate gain calibration for each ATWD bin? 20 40 60 80 100 120
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Pedestal at 1.1 V - Pedestal at 2.3 V
ATWD Channel 1 (718F) Pedestal Delta
][iATWDgPV iii ×+=
IIs this subscript necessary?
23 July 2003 LBNL DOM Workshop 9
Pedestal Noise – ISEG DOM 718F
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Noise peak amplitude (ATWD counts)
ATWD-A Ch0 Noise p-p Distribution (HV Off - DOM 718F)
PMT HV turned off!
max(abs(wfd-ped))
23 July 2003 LBNL DOM Workshop 10
ATWD Pedestal Noise (2)
• HV base turned off but ISEG base (718F) just disables HV – power not turned off to base. Disconnecting HV ribbon lowers noise somewhat.
• Oddly enough, Ch1 shows about same level of noise – would expect 4x less scaling with op-amp gain.
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Noise peak amplitude (ATWD counts)
ATWD-A Ch1 Noise p-p Dist (HV Ribbon Disconnected - 718F)
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450ATWD-A Ch1 Noise p-p Dist (HV Off - 718F)
Noise peak amplitude (ATWD counts)
23 July 2003 LBNL DOM Workshop 11
Pedestal Noise – ISEG DOM 7DAC (ISEG base /w/ no ground wire)
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Noise peak amplitude (ATWD counts)
ATWD-A Ch0 Noise p-p Dist (7DAC)
23 July 2003 LBNL DOM Workshop 12
Pedestal Noise – EMCO DOM 71DB
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Noise peak amplitude (ATWD counts)
ATWD-A Ch0 Noise p-p Dist (71DB)
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23 July 2003 LBNL DOM Workshop 13
Floating Baseline?
• Tried to test noise with HV on/off but run into problem of wobbling ATWD baseline and odd undershoot at pulse beginning (RHS).
• (See next page) overall stability of pedestal on 2 hr timescale OK /w/ HV off but HV on causes large rms and drift.
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23 July 2003 LBNL DOM Workshop 14
ATWD Drift vs. Time
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Average PS ATWD
ATWD Pedestal Drift ATWD Channel 0 718F
Approx 2 hr. run time
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<ATWD>
Pedestal mean drift versus time
NO HV HV ON
23 July 2003 LBNL DOM Workshop 15
Summary on Pedestal Testing
• Significant noise in FE seems due to HV base (no noise seen in DOMMB tests?). Of options EMCO/ISEG, latter produces clearly visible hash in FE while former is clean.
• Clamping amp nonlinearity significant. Can we tune this away or are we stuck with it? Do we really want to put a clamping amp on any more channels?
• ATWD channel 1 overflows at about 1 V input (50 pe) – again, is this a tuning problem?
• Is ATWD FE characterization simply a pedestal fingerprint or do we need more calibration knobs such as individual ATWD bin pedestals and gains.
23 July 2003 LBNL DOM Workshop 16
Pulser Tests
• Purpose– Calibrate op-amp gains– SPE/MPE discriminator studies
• Procedure– Disable HV– Set internal pulser amp to 1/3 pe, 1 pe, …– Do discriminator sweep (FSCAN)– Acquire pulser waveforms
23 July 2003 LBNL DOM Workshop 17
Pulser Discriminator
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DAC 9
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Discriminator Sweep Pulser = 0 (71DB)
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Discriminator Sweep Pulser = 10 (71DB)
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Discriminator Sweep Pulser = 30 (71DB)
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Discriminator Sweep Pulser = 30 (71DB)
23 July 2003 LBNL DOM Workshop 18
Pulser Waveforms
• Unable to acquire pulser waveforms with synchronous pulser trigger – advertised in FPGA register level docs but either I called incorrectly or problem at FPGA
• This type of trigger – synch with FE pulser, LED pulser, LED flasherboard required for some tests.
23 July 2003 LBNL DOM Workshop 19
SPE Discriminator Scan – PMT Pulses Input (71DB)
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23 July 2003 LBNL DOM Workshop 20
SPE Waveforms
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ATWD Sample
ATWD Counts
ATWD-Ch1 at 1500V spe trigger
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ATWD-Ch0 at 1500V spe trigger
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23 July 2003 LBNL DOM Workshop 21
SPE Waveforms (2)
• Presence of HV again causes drift of front-end baseline.
• This may be due to ATWD overvoltage– ATWD channel 1 can saturate– ATWD channel 2 seems OK – small drift but probably
functional– Why is ATWD channel 0, protected by clamping
amplifier, having problems?• Current situation with drifting baselines makes
analysis of ch0/ch1 waveforms very tricky – hope we can alter the clamping voltage to workaround – need information on this system.
23 July 2003 LBNL DOM Workshop 22
Gain and P/V Measurement – DOM 0001-3C62-71BD
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23 July 2003 LBNL DOM Workshop 23
Cheap P/V & Gain Analysis
• Used ATWD ch2 because of baseline wobble – gain of this channel is 2/3× so had to crank HV up to 1600, 1800, 2000 V.
• Clear P/V appears at 2000 V (apx. 2.2:1)
• Assuming ATWD gain is 1 mV/count, FE gain is 2/3×, the peak occurs around 40 mV – resulting in gain of about 5 × 107 – this just makes target!
23 July 2003 LBNL DOM Workshop 24
Signal Frequency Analysis
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Frequency (MHz)
Power Spectral Density (dB)
23 July 2003 LBNL DOM Workshop 25
Conclusions
• Noise on ISEG HV base is potential trouble – analog tests indicate that level is less than 1 mV p-p but really need to understand characteristics after FE op-amps.
• Several issues with ATWD-captured waveforms:– ‘startup’ bug: 1st sample after several seconds idle is corrupted –
this is more annoying than problematic– Crosstalk from clock when mux’ed into channel 3 – OK once AG
explained the problem and the fix. However, crosstalk from ch0 to ch1, ch2 potential problem. Do we test?
– Clamping amplifier causes log rolloff of channel 0– Saturated ATWD inputs cause sizable baseline drift
• ATWD channel 0 gain seems a bit high – 16x implies approx 100 mV spe, about 100 ATWD counts. Could probably reduce gain by factor of 2, perhaps up to 4.