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Preliminary Results of thePreliminary Results of theBeetle Readout for the MaPMTsBeetle Readout for the MaPMTs
Part 1: as presented on 17.06. Achievements since last LHCb week Common Mode correction Light scan High Voltage scan Conclusion
Part 2: new results Calibration Measured all connected MaPMT pixels Preliminary analysis of spectra Conclusions
MaPMT workshop, IC, 26.06.2003MaPMT workshop, IC, 26.06.2003 Stephan EisenhardtStephan EisenhardtUniversity of EdinburghUniversity of Edinburgh
J. Bibby, S. Eisenhardt, F. Muheim, N. Smale
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 2
Achievements since last LHCb Achievements since last LHCb weekweek New Beetle chip
visible noise factor 2-3 lower compared to the old chip which had died
(another sign that the old chip was dodgy…) Tuning of existing setup:
noise reduction of factor ~2 Noise reduction session: (2 1/2 days together with John and Nigel)
– rerouting of power supplies !!
– shielding of LED pulser !
– new coax cables between MaPMT and HD board !!!!
– new GND routing layout for unused channels at PMT base !!!!
– new star point for GND at front-end !!!!
– massive (1/2 inch) Al GND plate below HD mother board !!! all-in-all a noise reduction of factor ~5
Common mode reduction:– problem: 12 connected channels move more than the others
– solution: split into different groups and treat independently noise reduction of factor ~3
– problem: individual channels have ~10% weight
artificial dip at cut position in corrected spectrum
– solution: iterative CM reduction
dip reduced and moved to pedestal, CM reduction stays efficient
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 3
Data Frame from NtupleData Frame from Ntuple FED takes
160 samples / event header samples:
– show double peak
– also visible on oscilloscope
structure comes from the front-end of the system
12 channels bonded– 1 analog TestOut
– 1 outside the sampled frame due to mismatch in timing
10 channels visible bent base line
– Beetle1.2 ‘feature’
– signal inverted for better match to FED
gives positive charge signals
128 1 data frame
header bits: 200mV
bonded channel
w/o CM correction
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 4
Signal w/o CM correctionSignal w/o CM correction
Uncorrected pedestal width: ~ 4.5 ADC
Double peak structure variable with runs
(two peaks, shoulder or broader flank)
~ 2
pedestal run
signal run
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 5
Signal with CM correctionSignal with CM correction
Uncorrected pedestal width: ~ 4.5 ADC
Corrected pedestal width: ~ 1.4 ADC
artificial dip in spectrum from CM correction on few channels
~ 2
w/o CM correction
with CM correction
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 6
w/o CM correctionwith CM correction
LED Light scanLED Light scan
Varied amount of light to determine a working point with: ~ 1
80% signal 65%
20%38%
~ 2 ~ 1.5
< 1 ~ 1
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 7
w/o CM correctionwith CM correction
HV scan I - corner pixelHV scan I - corner pixel HV: -750…-825V
Uncorrected pedestal width: ~ 4.5 ADC
Corrected pedestal width:
~ 1.4 ADC
clear single photon signal
750V 775V
825V800V
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 8
w/o CM correctionwith CM correction
HV scan II - corner pixelHV scan II - corner pixel HV: -850…-925V
Uncorrected pedestal width: ~ 4.5 ADC
Corrected pedestal width:
~ 1.4 ADC
clear single photon signal
850V 875V
925V900V
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 9
w/o CM correctionwith CM correction
HV scan - center pixelHV scan - center pixel HV: -750…-900V
this pixel has a significantly higher gain
750V 800V
900V850V
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 10
Things to do:Things to do:
calibration of signal done proper S/N calculation done straighten out shifts in timing done check LED pulse width with analog TestOut channel not done
get proper BoardBeetle due to be submitted
the whole issue about digital readout is not yet touched... still
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 11
Part 1: ConclusionsPart 1: Conclusions
Great progress since last LHCb week– level of noise using the HD board is down by 2 orders of magnitude
– setup much better understood
– this knowledge is put into the design of the BoardBeetle
– analog readout of 8-stage MaPMT with Beetle1.2 is possible
– proper S/N figure still to be determined Binary readout option (no CM correction) still to be evaluated with
BoardBeetle Readout of 12-stage MaPMT with Beetle1.2MA0 (Nigel) looks very
promising as well report at MaPMT workshop
a great ‘Thank you!’ to John and Nigel!
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 12
Beetle Readout CalibrationBeetle Readout Calibration Voltage step: 0.0V,0.5V,
…5.0V,5.5 Error: 0.025V… 0.2V Rise time: <10ns Ringing: within 25ns
Attenuation: 400 10
Ceff: 3.0 0.1pC
1V: Q = CV = 472.3 ke-
= ~150mV 1 photoelectron
Linear description up to 2.5V (2.5 photons)
Quadratic description beyond Polynom fit to peak positions
12 runs with varied voltage step
individual
Gauss fits
no CM correction!
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 13
Signal in Low Gain PixelSignal in Low Gain Pixel Poisson fit: No photo conversion at 1st
dynode included Shoulder not described Gain underestimated
= 0.6
@ 800V (850V): Gain = 26 (37) Noise = 1.2 (1.2) S/N = 22 (31)
K1 = 3.5 (3.4)
Signal loss: ~13% (~10%)
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 14
Signal in High Gain PixelSignal in High Gain Pixel Poisson fit: No photo conversion at 1st
dynode included Shoulder not described Gain underestimated
= 0.6
@ 800V (850V): Gain = 51 (78) Noise = 1.6 (1.6) S/N = 33 (50)
K1 = 3.5 (4.6)
Signal loss: ~9% (~7%)
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 15
Noise StatusNoise Status where are we:
– CM correction gives factor of ~3 reduction– then we get a pedestal width of 1…1.5ADC channels– calibration gives a noise level of 2000…3000 e-
that is a factor 2…3 larger than what we expect for a channel with 10pF
where can we get with BoardBeetle:– track lengths 25…75mm (instead of ~175mm + two connectors)– all channels connected (no bricolage to care about unused channels)– less antennas– low impedance ground– lower capacity– great care taken to avoid noise brought in from the outside
(e.g. via supplies, grounds or fast control) with that there is reasonable hope to get a
noise level of O(1000 e-) without CM correction
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 16
Room for ImprovementRoom for Improvement with the HD system:
– Improve fits
– Try to understand shoulder (real photo conversion at dynode??)
– Comparison with Beetle1.2MA0 and 12-stage MaPMT
– Trial run of Binary operation (noise still a factor of 3…6 too high)
with the BoardBeetle:– Improved noise situation
– Full MaPMT readout
– Serious evaluation of binary readout
– Test beam
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 17
Things to do:Things to do:
study LED pulse behaviour through analog TestOut channel
get proper BoardBeetle, cabeling and jigs and get it operational
compare results from HD board to BoardBeetle to see what we gained
compare Beetle1.2(8-dyn) and Beetle1.2(12-dyn)
get through the learning curve of the digital readout
MaPMT workshop, IC, 26.06.2003 Stephan Eisenhardt 18
Part 2: ConclusionsPart 2: Conclusions Calibration: linear up to 2.5 photons, quadratic behaviour beyond
150mV/47ke- or 26ADC/47ke-
Noise level: 2000…3000 e-
Still room for improvement and reason to get it with BoardBeetle Present Poisson fit underestimates gain:
but we already get:– @800V:
• Gain: 26…51ADC
• S/N: 22…33
• Signal loss: 13…9%
– @850V: • Gain: 37…78ADC
• S/N: 31…50
• Signal loss: 10…7%
That already looks very nice! This promises to get an exciting test beam! Do I have to mention that there still is lots of work to be done?