photomultiplier signal processing Characterisation of the...
Transcript of photomultiplier signal processing Characterisation of the...
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Multi-time-over-threshold technique for photomultiplier signal processing
Characterisation of the SCOTT ASIC
S. Ferry1, F. Guilloux2
CEA Saclay, Irfu
and E. Delagnes2, F. Louis2, E. Monmarthe2, J-P. Schuller1, Th.Stolarczyk1, B. Vallage1, on behalf of the KM3NeT consortium3
1IRFU/SPP, 91191 Gif/Yvette, France2 IRFU/SEDI, 91191 Gif/Yvette, France3 Supported by the European Commission through FP6 and FP7
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KM3NeT
• Now in preparatory phase (FP7)
• A European deep-sea research infrastructure for a neutrino telescope – Mediterranean Sea– Instrumented volume
5 km3
– 300 detection units– 12000 photo-detectors
• Cherenkov light detection– Upward – Downward cosmic – Optical background (100 Hz / cm-2)
40K decay in water
Bioluminescence
Mainly single photon signals
• All data to shore– On shore computer farm
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Front end requirements (from CDR)
• Time resolution (PMT+FE) < 2 ns at 1 pe (RMS)
• Charge dynamic range : 100 pe / 25 ns– Charge estimation
• Two-hit time separation < 25ns
SCOTT ASIC
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SCOTT concept
• Time and Amplitude Sampling– “wave-form”-like image of
the pulse
• Master Clock 50 MHz– 16 bit Time stamp
• 1.25 ns sampling
• 16 independent channels– Dynamic range : 0- 3V– 10 bit adjustable thresholds
• Auto-triggered– Each threshold can be a
trigger– Handling several PMTs e.g.:
2 PMTs x 8 thresholds
16 PMTs x 1 threshold
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Analogue input
Analogue switchesInternal sharing of
signals
10 bit DACAMS BiCMos
0.35mProgrammable
thresholds LSB<3mV
DiscriminatorAnalogue to digital
convertor
SCOTT architecture
Sophie Ferry - NDIP11 - Characterisation of SCOTT
5x16 channels
SOC
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Circular sampling memory
Delay locked loop (DLL)
All channels are synchronous
Circular digital memory
2 memory banks (MB)1MB = 1 time slice =20 ns
No dead time
16 bit coarse time counter
LSB = 20 ns
Time step TCK
/16
Ts
= 1.25ns (~ 800MHz)
SCOTT architecture
Sophie Ferry - NDIP11 - Characterisation of SCOTT
6x16 channels
SOC
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SCOTT architecture
Sophie Ferry - NDIP11 - Characterisation of SCOTT
7x16 channels
SOC
FIFOAuto-triggered
Logical or channel triggered
Size32 time slices
640 ns continuous wave-
form
Data loss <1‰ for 200 kHits/s
Double portFck
sample ≠Fck
readoutReadout driven by System-on-Chip
Selective readoutData reduction
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Scott output example
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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11280
0000000000000111000000000000001100000000000000010000000000000001
11281
11111111000000001111111000000000111111100000000011111100000000001111110000000000111111000000000011111000000000000111000000000000
Am
plitu
de
Time
20 ns
1.25 ns
Coarse Time stamp11283
0100000001111100
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The SCOTT Opera
•
Act I : Determination of thresholds– Which values for how many thresholds ?
•
Act II : Charge
•
Act III: Timing– Correction of the walk effect– SCOTT Intrinsic timing accuracy
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ACT I THRESHOLD DETERMINATION
ActorsPMT : Antares 10’’ Gain=3·107
1 pe
50mV 5pC
LED : flashes at 1pe up to 70peOscilloscope : F=2.5GHz Bandwidth=500MHz
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11
Tpeak
Sophie Ferry - NDIP11 - Characterisation of SCOTT
Performances verified with SCOTT
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ACT II CHARGE RESOLUTION
ActorsPMT : Antares 10’’ gain=3.107
1pe
50mV 5pC
LED : flashes at 1pe and 11peSCOTT : 5 thresholds
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• Integration of FRED : needs CPU time• Alternative based on Time-Over-Thresholds (TOT)
– Upper (Q+ ) and lower(Q- ) area under the thresholds
• Q
(Q+ + Q- ) / FQ– FQ depends on
the last threshold reached
the threshold values
requires calibration
Q+ Q-
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Charge resolution from TOTs
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Charge 1pe
Mean=5pCRMS =2pC = 40%(PMT charge resolution
35%)
SCOTT + TOT enable charge reconstruction with good accuracy
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ACT III TIMING RESOLUTION Scene 1 : Pulse time resolution
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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ActorsPMT : Antares 10’’ gain=3.107
1pe
50mV 5pC
LED : flashes at 1pe and 11peSCOTT : PMT 5 thresholds
LED trigger 1 threshold
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Pulse time reconstruction
Walk effect- Threshold crossing time
depends on the charge- Peak time Tpeak unchanged
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residuals
1st
thres.
TOT[i] (ns)
Tpea
k-T 0
[i]
All thresholds
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Tpeak and Walk correction with SCOTT
• T1/3 -TLEDT1/3 =crossing time of the 1st
threshold
• Tpeak - TLED
Sophie Ferry - NDIP11 - Characterisation of SCOTT 17
(11+1)pe Nentr 1852RMS 1.5
1pe11pe
11+1pe
(11+1)pe Nentr 1852RMS 2.5
1pe11pe
11+1pe
TTSPMT
1.3 ns
Time resolution = 1.5 nsNo charge estimate needed
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ACT III TIMING RESOLUTION Scene 2 : SCOTT Intrinsic timing accuracy
ActorsGenerator: HP 81110A 330MHz
SCOTT
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SCOTT intrinsic timing
• Generated Pulse– 120mV height– 1kHz
• SCOTT: 6 thresholds15% 35% 50% 70% 85% 90%
Sophie Ferry - NDIP11 - Characterisation of SCOTT 19
00000000111111110000000000000111
11111111111111111111111111111111000111111111111100000000111111110000000000000001
111111111111111111111111111111111111111111111111111111111111111111111111111111110111111111111111
• Consider all possible time between crossing times for every couple of thresholds
(ns)
SCOTT intrinsic time resolution 0.8ns
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Conclusion
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The End
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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PM
T
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SCOTT architecture
• Analogue input
Analogue switchesInternal sharing of signals
10 bit DACAMS BiCMos 0.35m
Programmable thresholds LSB<3mV
DiscriminatorAnalogue to digital
convertor
• FIFO and zero suppressAuto-triggeredLogical or channel
triggered
Size32 time slices
640 ns continuous wave- form
Data loss <1‰ for 200 kHits/s
Double portFck sample ≠Fck readout
Readout driven by System-on-Chip
Selective readoutData reductionSophie Ferry - NDIP11 - Characterisation of SCOTT 22
• Fast memory samplingDelay locked loop
(DLL)All channels are synchronous
Circular digital memory2 memory banks (MB)
1MB = 1 time slice =20 nsNo dead time
16 bit coarse time counter
LSB = 20 ns
Time step TCK /16
Ts = 1.25ns (~ 800MHz)
1channel
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FRED
23
Apeak
Tpeak
tR
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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Tpeak residuals
Sophie Ferry - NDIP11 - Characterisation 24
Apeak
Tpeak
tR
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Test bench
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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PMT
HTAnode
Diff
LED
Black Box
PMT
HTAnode
oscilloscope
Diff
LED
Black Box
SCOTT
Generator
PMT
HTAnode
Diff
LED
Black Box
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Generated pulse viewed with SCOTT
Sophie Ferry - NDIP11 - Characterisation of SCOTT
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30164
00000000111111110000000000000111
30165
11111111111111111111111111111111000111111111111100000000111111110000000000000001
30166
111111111111111111111111111111111111111111111111111111111111111111111111111111110111111111111111
30167
111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111000
30168
11111111111111111111111111111111111111111111100011111110000000001000000000000000
30169
1111111110000011100000000000
Am
plitude
Time
20 ns
1.25 ns
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PMT characterisation
• PMT + Oscilloscope
Sophie Ferry - NDIP11 - Characterisation 27
PMT
HTAnode
oscilloscope
Diff
Black Box
Define the 1PE 50 mV 5.4 pC
Amplitude max.
Charge
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Amplitude with FRED & SCOTT
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T1/3 versus charge
• T1/3PE versus charge
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1PE and 11PE
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Tpeak versus charge
• Tpeak versus charge
30Sophie Ferry - NDIP11 - Characterisation of SCOTT
1PE and 11PE
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Sophie Ferry - NDIP11 - Characterisation of SCOTT31
Charge 11peCharge 1pe
Charge resolution with FRED + SCOTT
Mean=70pC RMS=22pC: 32%
Mean=5pC RMS=2pC: 37%
SCOTT + Pulse fit enable charge reconstruction without introducing further error
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SCOTT data set
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• 1 + 11 pe data sets
0 1/3 2/3 1 4/3 5/3 2 3 8 pe
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Analogue to digital@ SCOTT
Sophie Ferry - NDIP11 - Characterisation 33
Front End
Asic
System on
Chip
Analogue
Signal
Digital
data
Ethernet TCP/IP
data link
Shore