Download - Scintillator/WLS Fiber Readout with PSiPs
Scintillator/WLS Fiber Readout Scintillator/WLS Fiber Readout with PSiPswith PSiPs
Pablo Bauleo, Yvan Caffari,Eric Martin, David Warner,
Robert J. Wilson Department of Physics
Colorado State University
International Workshop on new Photon-Detectors (PD07)Kobe, Japan.
June 27nd 2007
R.J.Wilson
OverviewOverview
Pixelated Silicon Photosensors (PSiPs)
Motivation: T2K/ND280 + ILC Detector
Bench Tests – aPeak GPDs
FNAL Beam Test – HPK MPPC & CPTA MRS
Summary
R.J.Wilson
MotivationMotivation
Linear Collider Detector– Muon, calorimeter systems
– MINOS scintillator bar w/ Y-11 WLS fiber muon system candidate T2K Near Detector at 280 m (ND280)
– Beam Monitor (NGRID), Fine-Grained Detector (FGD), Sideways-Muon Ranging Detector (SMRD), Pi-zero Detector (P0D)
– P0D : 98% interactions <19 MeV/bar; 30% <1MeV/bar Historically CSU also motivated by Ring Imaging Cerenkov Detectors
– BaBar DIRC with array of ~11,000 1” pmts and large water tank outside magnetic field
– R&D on Focusing DIRC with small arrays of single UV photon sensitive solid state pixels in the magnetic field
– Led to association with US developer of PSiPs (aPeak Inc.)
R.J.Wilson
PMT Cosmic Ray/LED charge distributionsPMT Cosmic Ray/LED charge distributions
PMT (EMI 911B) response to ~ vertical cosmics rays (VCR) as a reference
Simulate with 550 nm LED (matched to peak of Y11 WLS fiber output peak)
Allows for rapid data collection LED distribution lacks high tail of cosmic
ray sample LED settings adjusted to shift peak for
range 0.2-13 VCR; shape and spectrum of true multiple VCRs unknown
~2 MeV deposited/VCR No absolute calibration
1 VCR 200 “photons” out of Y11 WLS
0 20 40 60 80 100 120 140 160 180 200 220 2400
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420 Gaussian amplitude : 290.11 mean : 89.234 sigma : 12.570
Gaussian amplitude : 43.945 mean : 113.50 sigma : 45.078
Gaussian+Gaussian Gaussian: amplitude : 290.11±6.24 Gaussian: mean : 89.234±0.26 Gaussian: sigma : 12.570±0.301 Gaussian: amplitude : 290.11±6.24 Gaussian: mean : 89.234±0.26 Gaussian: sigma : 12.570±0.301 χ² : 1.8647
Data - 1vcr_15inchhodoscope_datacut - ADC0
1 ADC ct. = 0.125 pc
Charge (ADC bins)
Cosmics
g180-s145-250V - ADC0
LED
Mean charge ~11 pC in 300 ns gate defines unit of 1 VCR;
Same PMT fitted with a mask with 1 mm diameter circular hole; placed 80 cm from 550 nm LED
LED voltage (2.5 V) and pulse width (14.5 ns) adjusted to ~ replicate charge spectrum of 1 VCR (180 ns gate)
MINOS/ILC-Muon bar
1 “VCR”
R.J.Wilson
aPeak Inc. 64-fiber Readout (16-GPD/pixel)aPeak Inc. 64-fiber Readout (16-GPD/pixel)
aPeak goal - high efficiency, high-density, compact, low-cost WLS/fiber readout primarily for non-calorimetric use
64 x 1 mm2 fiber readout on one chip Each pixel is a cluster of sixteen
160x160 m2 GPDs on 240 m centers Geometrical efficiency for 1.2 mm
diameter fiber ~ 0.36 (0.45 for 1 mm) Signal out proportional to number of hit
GPDs; allows hit threshold tuning (not optimized for calorimetry)
Very low operating bias: ~14 V
1.2 mm
10 mm
2006
R.J.Wilson
GPD SignalGPD Signal
GPD bias -14.2 V 550 nm LED illumination 10x linear amplifier Setup not optimized for fast
signals – intrinsic device speed much faster (aPeak)
DC offset – origin unclear, depends on bias
Single shot Average many triggers
500 ns 500 ns
R.J.Wilson
Detection Efficiency/Dark Count RateDetection Efficiency/Dark Count Rate
Dark Count Rate (DCR) from scaler of discriminated signal
Product of signal width (w) and dark count rate (DCR) reduces effective detection efficiency by factor ~ (1-w*DCR)
DEmeas = 95% for 1 VCR has 0.6 MHz DCR so 300ns gate => DEeff ~ 78%
Improve by lowering temperature– Developed computer controlled
system with Peltier refrigerator
Detection Efficiency & Dark Count Rate
0
0.2
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-1000-800-600-400-2000
Vth ( mV )
DE
& D
CR
(M
Hz)
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DCR
Note: GPD signal with 10x amplifier
GPD bias -14.2 V
95% DE
0.9 VCR2.6 VCR
5.2 VCRAt low Vth rate
too high leadssignal overlap
DE = measured rate – dark rate LED rate
LEDIntensity
DCR
R.J.Wilson
Detection Efficiency: Charge DistributionDetection Efficiency: Charge Distribution
-10°C -10°C At low temp./low bias
begin to see “features”
-19°C
Range bias voltage: 13.1-14.1 V
- 1 “VCR” LED intensity ()
- Dark ()
DE = # triggers with charge above “threshold” # triggers
R.J.Wilson
Single Photoelectron PeaksSingle Photoelectron Peaks
First time individual peaks resolved in aPeak device
Absolute gain from pe peaks ~2.5 x 106
Dark spectrum -> crosstalk low
-19°C-13.3V
-19°C-13.3V
1 pe 2 pe 3 pe 4 pe
R.J.Wilson
Pixel Charge vs. IntensityPixel Charge vs. Intensity
Mean measured GPD charge linear for 0-1.3 VCR; 1VCR~10pe Plateau corresponds ~ to all 16 GPDs in the cluster registering a hit; shape consistent
with a model based on earlier single GPD DE measurements; Large “dark” charge => high rate of thermal electrons initiated signals
GPD pixel 4-3 amplifier output, 500 ns gate
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0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
VCR equivalent LED output
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arg
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pC
)
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VCR equivalent LED output
char
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GPD bias -14.2 VRoom temp. ( ~23°C)
corr
ect
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r -2
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ato
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aPeak GPDs SummaryaPeak GPDs Summary
New aPeak high density readout (64 fibers/chip)– Modest “calorimetric” response demonstrated; useful for threshold tuning– High efficiency for relatively high light levels at
room temperature due to high dark count rate/long pulses– Low temp. demonstrated single p.e. for first time
aPeak plans– “Can reduce DCR 50-70% in medium volume run (planned for next run)” – “This will allow us to provide both verified-reliability, highly-manufacturable
devices and customized devices for low-noise needs” – “Cost/die should be similar for both technologies, however the medium volume
approach would require large orders for new layouts or if stock is depleted”
– “Both technologies should provide reliable devices but only the high-volume process and layout have been (extensively) verified at aPeak for reliability and radiation damage”
Single fiber readout 129-pixel devices in-hand– Uses high volume process– Calorimetric behavior demonstrated at room temp
R.J.Wilson
FNAL Beam Test – Experiment T695FNAL Beam Test – Experiment T695
Cosmics give MIP response and energy scale but low rate makes it difficult to test many devices
LED flasher is fast but not the same spectrum as Y11 output and doesn’t map position response (especially in triangular P0D bars)
Beam test at new Fermi National Accelerator Lab Test Beam Facility (FTBF) – Experiment T695
First FTBF beams delivered February 2007 and we were there just one month later – a few “hiccups” but went reasonably well.
R.J.Wilson
Beam ParametersBeam Parameters
120 GeV protons (MIPs) Timing structure
– Bunch train: 84 x 18.87ns buckets in 1.58 s
– 1 train every ~12 s (if 1 main injector bunch)
– 4 sec “spill” 3.33 x 105 trains/spill
– ~60,000 protons/spill
– Estimate single proton per trigger ~85% of time Beam size:
– 3-4 mm RMS horizontal (along bars)
– 5-6 mm RMS vertical (across the bars) Trigger
– Scintillator hodoscopes up/downstream of test box
– No precision tracking in the analysis
R.J.Wilson
CSU Beam Test TeamCSU Beam Test Team
Pablo Bauleo– DAQ/online s/w
Eric Martin– Electronics
David Warner– Design/fabricationDesign/fabrication
Yvan Caffari– Offline analysis
Robert J. Wilson– PI
R.J.Wilson
Test StructureTest Structure
3 MINERVA/P0D + 2 MINOS/ILC scintillator + Y11 WLS fiber
CSU PSiP housing; optical grease used for coupling;PMTs at far end (expect low reflection)
R.J.Wilson
Test StructureTest Structure
“Beam Box” checkout at CSUA calibrated PMT can be mountedin the same location as each PSiP
R.J.Wilson
FNAL Beam TestFNAL Beam Test
Remote controllable vertical/horizontal table
R.J.Wilson
Devices TestedDevices Tested
5 HPK MPPC-11-T2K-5808: 400 pixel– Vop ~70 V
4 CPTA MRS 1710: 556 pixel– 2 with Vop~44V
– 2 with Vop~48V
5 aPeak Inc. GPD 100 pixel– Vop~14 V
– Not reported here
4 7 k o h m 4 7 k o h m
1 0 0 n F 1 0 0 n F
B ia s
1
S ig n a l
1
S iP D
1 0 k o h m
1 0 k o h m1 0 0 n F
1 0 0 n F
B ia s
1
S ig n a l
1
S iP D
R.J.Wilson
Calibration/Monitoring/ConfigurationsCalibration/Monitoring/Configurations
Monitoring pmts at opposite fiber end from PSiPs (except one)
– Hamamatsu R268, Vop=1300V Initial run through all planned beam positions with pmt replacing PSiP
– Electron Tubes 9111A, Vop = -950V, gain 1.03 x 107
“Beam Off” data (100 Hz pulser) taken interspersed with “Beam On”
“Long cables” configuration ~11ft/3.3 m cables , temp 23°C– MPPC 50Gv x 6dB attenuator; 400 ns gate
– MRS 50Gv, no attenuator; 400 ns gate “Short cables” configuration ~3ft/1 m; temp. 17°C
– MPPC 50Gv, no attenuator; 200 ns gate
– MRS 50Gv, no attenuator; 400 ns gate
R.J.Wilson
FNAL Beam TestFNAL Beam Test
PSiPor
Calibration PMT
Monitoring PMT
near end center far end
x
y4in/10cm 35in/89cm
69in/175cm
3 horizontal positions3-5 vertical positions
y
x
120 GeV/c protons
40.8
mm
66 m
m
1
4
2
3 5
2 MINOS/ILC bars3 MINERVA/P0D bars
Not to scale
To scale
R.J.Wilson
Beam – HodoscopeBeam – Hodoscope
Beam Off
1 proton
2 protons
All plots following are “1 proton” or “Beam Off” (for pedestal/DCR)
R.J.Wilson
Calibration PMT - PSiP ComparisonCalibration PMT - PSiP Comparison
Calibration PMTMonitoring PMT
2 independent runs :• 1 run with a calibration PMT at the near end with 1 monitoring PMT at the far • 1 run with 1 MPPC at the near end and the same monitoring PMT.
Beam on the center of aMINERVA bar.
• The monitoring PMT has the same behavior for both runs.• So can directly compare the PSiP response to the calibration PMT
MPPC Vbias = -70.0V
Monitoring PMT
R.J.Wilson
MPPC Charge Spectrum – 1 runMPPC Charge Spectrum – 1 run
1
4
2
3 5
PSiPs
Not to scale
R.J.Wilson
MRS Charge SpectrumMRS Charge Spectrum
Near-end
Far-end
R.J.Wilson
Calibration – Dark + Signal SpectrumCalibration – Dark + Signal Spectrum
Beam Off (pulser) and Beam On data• MPPC: use p.e. in low intensity signal and use of the p.e. in the dark spectrum (self-calibration)• MRS: use p.e. in low intensity signal; no distinct p.e. peaks in dark spectrum• Calibration PMT: known characteristics and beam data
0 p.e.
1 p.e.
2 p.e.
3 p.e.4 p.e.
0 p.e.
1 p.e.
2 p.e.3 p.e.
4 p.e.
Dark spectrum Dark spectrum0 p.e.
1 p.e.
2 p.e.
3 p.e.4 p.e.
Dark spectrumMPPC
Dark spectrum
MRS
R.J.Wilson
HPK MPPC : Cross-talkHPK MPPC : Cross-talk
Cross talk = # events above 1.5 p.e threshold# events above 0.5 p.e. threshold
(no subtraction of random coincidences)
0.5 p.e.1.5 p.e.
MPPC Crosstalk
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1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2
Vop-Vbr (V)
Cro
ssta
lk (
%) MPPC 50
MPPC 51
MPPC 54
MPPC 59
MPPC 56
R.J.Wilson
HPK MPPC : Gain curveHPK MPPC : Gain curve
From just beam off dark spectrum (similar results with signal spectrum) Linear - Slope ~ 4.5 x 105 /V => self-calibration
ND280 electronics req.
From fit to data – no crosstalk correction Measured Npe ~ linear w/ V=(Vbias-Vbd) “kink” at 3rd point – not understood…
R.J.Wilson
HPK MPPC : Dark RateHPK MPPC : Dark Rate
Dark Count Rate calculated from Beam Off spectrum for 0.5 p.e. & 1.5 p.e. thresholds Compare with manufacturer data
Gain measurements consistent (to 10%) > 0.5 p.e. rates lower 10-30% > 1.5 p.e. rates higher by factor 5-7
Effect of high crosstalk
R.J.Wilson
CPTA MRS : Gain/NpeCPTA MRS : Gain/Npe
From signal spectrum Gain ~ linear with V=(Vbias-Vbd) Slope ~ 3.8 x 105 /V
ND280 electronics req.
# pde increase linear with V
R.J.Wilson
Attenuation –PMT on MINOS+MINERVAAttenuation –PMT on MINOS+MINERVA
Bars indicate RMS of distributions
MINERVA/P0D MINOS
Beam on vertical center of middle MINERVA bar
R.J.Wilson
Attenuation – MPPC/MRS on MINOS barAttenuation – MPPC/MRS on MINOS bar
Beam on vertical center of MINOS bar From fit to data – no crosstalk correction (30-35% for MPPC)
c.f. PMT range 14.5 p.e. – 6 p.e.
MPPC MRS
R.J.Wilson
AttenuationAttenuation – – MPPC/MRS on MINERVA/P0D barMPPC/MRS on MINERVA/P0D bar
c.f. PMT range 13 p.e. – 5.5 p.e.
MPPC MRS
Beam on vertical center of MINERVA/P0D bar From fit to data – no crosstalk correction (30-35% for MPPC)
R.J.Wilson
Attenuation SummaryAttenuation Summary
MPPC and MRS bias chosen to meet T2K/ND280 electronics gain & DCR requirements
– MPPC_54: V=70.3V, Vop-Vbr =1.67V, Gain=822k, Xtalk=30%
– MRS_111: V=42.5, Vop-Vbr=2.2V, Gain=738k
Fit to an exponential, signal at end of 240 m P0D bar would be:
– 5.9 p.e. for MPPC
– 2.4 p.e. for MRS
– 3.5 p.e. for PMT P0D simulation assumes 6.5 p.e. for
blackened fiber end (~3.3 p.e./MeV)
Attentuation in MINERVA/P0D Bar
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MPPC – xtalk corrected
PMT
MRS
R.J.Wilson
SummarySummary
US developer (aPeak) with high density, (potential) low cost design– 64 fiber r/o with modest dynamic range (16-pixels) – Room temp. operation but single p.e. resolution only below -10°C– Recent 100-pixel single fiber r/o device tested– Future developments include lower DCR design (room temp. p.e.?)
Beam test of HPK/MPPC and CPTA/MRS with MINOS & T2K/ND280 P0D bars– Beam test conditions i.e. many noise sources, long cables etc.– Evaluated basic performance characteristics– MPPC promising for QE & single p.e. DCR but crosstalk worrisome– MRS older design – PDE not high enough for P0D
T2K/ND280 committed to PSiPs rather early in their commercial history - a bold choice not without risks… continued testing is essential