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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VCR equivalent LED output

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pC

)

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VCR equivalent LED output

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GPD bias -14.2 VRoom temp. ( ~23°C)

corr

ect

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fo

r -2

9 d

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ato

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ier

R.J.Wilson

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

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y4in/10cm 35in/89cm

69in/175cm

3 horizontal positions3-5 vertical positions

y

x

120 GeV/c protons

40.8

mm

66 m

m

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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

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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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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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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