Vancouver Linear Collider Workshop University of British Columbia, Canada July 20 th 2006 Scintillator/WLS Fiber Readout with Geiger-mode APD Arrays Pablo

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


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


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)


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


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


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


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


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


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


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


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


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


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!

Documents

Vancouver Linear Collider Workshop University of British Columbia, Canada July 20 th 2006 Scintillator/WLS Fiber Readout with Geiger-mode APD Arrays Pablo