Vancouver Linear Collider Workshop University of British Columbia, Canada July 20 th 2006...
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Transcript of Vancouver Linear Collider Workshop University of British Columbia, Canada July 20 th 2006...
Vancouver Linear Collider Workshop
University of British Columbia, Canada
July 20th 2006
Scintillator/WLS Fiber Readout withScintillator/WLS Fiber Readout withGeiger-mode APD ArraysGeiger-mode APD Arrays
Pablo Bauleo, Rey Nann Ducay, Eric Martin, David Warner, Robert J. Wilson, Qinglin Zeng, Department of PhysicsColorado State UniversityStefan VasileaPeak Inc.63 Albert Road, Newton, MA 02466-1303
R.J.Wilson, Colorado State University
OverviewOverview
Motivation
Recap 7-GPD cluster measurements with MINOS-type bars
Recap single square GPD measurements
New single-chip 64-fiber readout
Summary
R.J.Wilson, Colorado State University
MotivationMotivation
WLS readout of scintillator strips basic component of several existing detectors (MINOS, CMS-HCAL); option for LC muon/calorimeter systems
Geiger-mode Avalanche photodiodes (GPDs)– Pros: Large pulse (~volt); high quantum efficiency; relatively fast; compact; low
mass; low voltage operation (~10s volts); modest physical plant; magnetic field insensitive; compatible with CMOS -> cheap?
– Cons: High dark count rate; small pixels (13-160 microns); unproven.
Growing number of developers…– SiPM: Dolgoshein et al., Russia – some production level; tested by several groups– MRS APD (Metal Resistor Silicon APD): INR, Moscow; manufactured by CPTA,
Russia – few hundreds; tested by several groups– MPPC (Multi-Pixel Photon Counters): Hamamatsu Photonics, Japan – a few R&D
devices; one group? (possibly others in Japan)– GPD: aPeak, USA – a few R&D devices; examined at CSU
R.J.Wilson, Colorado State University
7-pixel GPD cluster (2005)7-pixel GPD cluster (2005)
Seven 150 m GPDs; ~16% of 1 mm fiber area Individual readout of each pixel Response to cosmic rays measured at CSU with modified MINOS bar + WLS Average individual pixel Detector Efficiency, DE ~14% Cluster DE ~65%
GPD cluster
Clear fibers
Active Quenching Circuit (AQC)
R.J.Wilson, Colorado State University
Single 162 x 162 Single 162 x 162 mm22 Square GPD (2005) Square GPD (2005)
DE – measured detection efficiency DCR – Dark Count Rate DE1000 – effective DE if the quenching time is 1000 ns (typical of unquenched devices)
DE & DCR for "Optimal" GPD bias
9
10
11
12
13
14
15
16
17
18
-20 -10 0 10 20 30
Temperature (degC)
DE
(%
)
0
0.5
1
1.5
2
2.5
3
3.5
4
DC
R (
10
^5
Hz)
DE DE1000 DCR (10 5̂ Hz)
Single 162m x 162m GPD 5 photons/event
R.J.Wilson, Colorado State University
New 64-fiber Readout (16-GPD/pixel)New 64-fiber Readout (16-GPD/pixel)
aPeak goal is high efficiency, high-density, compact, cheap 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)
No active quenching circuitry
1.2 mm
10 mm
R.J.Wilson, Colorado State University
GPD Testing/ComparisonGPD Testing/Comparison
Use PMT (EMI 911B) response to cosmics & 550 nm LED as a reference
PMT used to read out WLS fiber embedded in MINOS bar (courtesy FNAL);
fiber extends 22” beyond end of the bar
Charge spectrum collected for ~vertical cosmic rays
Same PMT fitted with a mask with 1 mm diameter circular hole; placed 80 cm from 550
nm LED
LED voltage and pulse width adjusted to replicate cosmic ray charge spectrum; process
repeated with different LED settings to produce range of intensities
Replace the PMT with GPD array at same position
LED allows testing at much higher event rates and controllable range of intensities
R.J.Wilson, Colorado State University
PMT Cosmic Ray/LED charge distributionsPMT Cosmic Ray/LED charge distributions
Charge spectrum of ~ vertical cosmic rays (VCR) in 300 ns gate; use this to define unit of 1 VCR; mean charge ~11 pC (PMT gain ~107)
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)
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
No absolute calibration; Approx. 1 VCR = 200 “photons“ out of WLS
0 20 40 60 80 100 120 140 160 180 200 220 2400
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
400
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 bin = 0.25 pc
Charge (ADC bins)
Cosmics
g180-s145-250V - ADC0
LED
R.J.Wilson, Colorado State University
GPD SignalGPD Signal
GPD bias -14.2 V 550 nm LED illumination 10x linear amplifier DC offset – origin unclear,
depends on bias
Single shot Average many triggers
R.J.Wilson, Colorado State University
GPD Cluster LED charge distributionsGPD Cluster LED charge distributions
10x amplifier on the GPD output for timing measurements
29dB attenuator used to bring the signal into the ADC range
LED rate – 30 Hz 500 ns ADC gate;
pedestal 20 pC (bin 80)
120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 4600
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1,000
1,050
1,100
Data - PIXEL45_g500ns_30dB_08vcr_250V_145ns_30hz - ADC0GPD cluster charge spectrum for
~ 1 & 4 VCR equivalent LED intensity;
~ 200 & 800 incident “photons”;
~ 4 & 16 “photons”/individual GPD1,000
1,100
1,200
1,300
140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 5200
100
200
300
400
500
600
700
800
900
PIXEL45_g500ns_30dB_3vcr_325V_18ns_30hz - ADC0
1 VCR4 VCR
GPD bias -14.2 V
R.J.Wilson, Colorado State University
Pixel Charge vs. IntensityPixel Charge vs. Intensity
Linear for 0-1.3 VCR Rollover corresponds to all GPDs in the cluster registering a hit; shape consistent
with a model based on earlier single GPD DE measurements; Similar distribution seen if average peak voltage used instead of charge
GPD pixel 4-3 amplifier output, 500 ns gate
0
1000
2000
3000
4000
5000
6000
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
ch
arg
e (
pC
)
2000
2500
3000
3500
0.0 0.5 1.0
VCR equivalent LED output
char
ge
( p
C )
GPD bias -14.2 V
corr
ect
ed
fo
r -2
9 d
B a
tte
nu
ato
r b
ut
no
t 1
0x
am
plif
ier
R.J.Wilson, Colorado State University
Detection Efficiency/Dark Count RateDetection Efficiency/Dark Count Rate
For signal threshold voltage, Vth
– Dark Count Rate (DCR) from scaler– Detection Efficiency (DE) calculated
from comparing discriminated pixel signal rate with/without pulse generator
Fall off of at low Vth due to high DCR and signal width
Product of signal width (w) and dark count rate (DCR) reduces effective detection efficiency by factor ~(1-w*DCR)
– e.g. for 300 ns & 1 MHzDE_eff = 0.7*DE
Improve by lowering temperature
Detection Efficiency & Dark Count Rate
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
-1000-800-600-400-2000
Vth ( mV )
DE
& D
CR
(M
Hz)
0.2
0.4
0.7
0.9
1.2
2.6
3.9
5.2
6.5
7.9
9.2
10.5
DCR
Note: GPD signal with 10x amplifier
GPD bias -14.2 V
95% DE
0.9 VCR2.6 VCR
5.2 VCR
Signal overlap
R.J.Wilson, Colorado State University
Detection Efficiency vs. ChargeDetection Efficiency vs. ChargeDetection Efficiency
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Threshold (pC)
de
tec
tio
n e
ffic
ien
cy
13 VCR
12 VCR
11 VCR
9.2 VCR
7.9 VCR
6.5 VCR
4 VCR
3.9 VCR
2.6 VCR
1.2 VCR
0.95 VCR
0.69 VCR
0.43 VCR
0.21 VCR
dark
R.J.Wilson, Colorado State University
SummarySummary
New aPeak high density readout (64 fibers/chip) Modest “calorimetric” response demonstrated; useful for threshold tuning High efficiency demonstrated but only for relatively high light levels at room
temperature due to high dark count rate/long pulses Temperature dependence to be measured soon (starting this week) Progress, but not yet demonstrated to be competitive with other options
Funding– LCRD funding - $14k = 4 weeks Dave Warner + trip to midwest
– aPeak phase II funding: no-cost extension 7/06 -> 4/07; goal to test 64 fiber r/o with muon prototype (Dave planning a Fermilab trip soon)
Related news – CSU group now part of T2K collaboration– ND280 (Near-Detector) will use Russian MRS APD and Japanese (HPK) MPPC
– Testing of >10,00 at CSU; good training for LCD muon system!