Preliminary Results of the Beetle Readout for the MaPMTs Part 1: as presented on 17.06. ...

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


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


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


Signal with CM correctionSignal with CM correction


Corrected pedestal width: ~ 1.4 ADC

artificial dip in spectrum from CM correction on few channels

~ 2

w/o CM correction

with CM correction


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



HV scan I - corner pixelHV scan I - corner pixel HV: -750…-825V


Corrected pedestal width:

~ 1.4 ADC

clear single photon signal

750V 775V

825V800V



HV scan II - corner pixelHV scan II - corner pixel HV: -850…-925V


Corrected pedestal width:

~ 1.4 ADC

clear single photon signal

850V 875V

925V900V



HV scan - center pixelHV scan - center pixel HV: -750…-900V

this pixel has a significantly higher gain

750V 800V

900V850V


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


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!


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!


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%)


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%)


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


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


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


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?

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Preliminary Results of the Beetle Readout for the MaPMTs Part 1: as presented on 17.06. ...

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