ALCPG, UT-Arlington January 10th 2003 Preliminary Investigations of Geiger-mode Avalanche...

ALCPG, UT-ArlingtonJanuary 10th 2003

Preliminary Investigations of Preliminary Investigations of Geiger-mode Avalanche Photodiodes Geiger-mode Avalanche Photodiodes

for use in HEP Detectorsfor use in HEP Detectors

David Warner, Robert J. Wilson Department of PhysicsColorado State University

R.J.Wilson, Colorado State University

OutlineOutline

Motivation

Avalanche Photodiodes

Characteristics

R&D Plans

Conclusions


MotivationMotivation

Scintillating fiber, or WLS readout of scintillator strips basic component of several existing detectors (MINOS, CMS-HCAL)

Standard photodetector – photomultiplier tubes, great devices but…– “Expensive” (including electronics etc.),

– Bulky, magnetic field sensitive…

For the next generation would like a photon detector to be:– Cheaper

– Compact? Low mass? Magnetic field insensitive? Radiation hard?

Future experiments– BaBar upgrade - endcap?

– Future e+e- Linear Collider? LHC?

– Nuclear physics? Space-based (NASA)?


Silicon Avalanche Photodiodes (APD)Silicon Avalanche Photodiodes (APD)

Solid state detector with internal gain. Avalanche multiplication

– initiated by electron-hole free carriers, thermally or optically generated within the APD

– accelerated in the high electric field at the APD junction.

Proportional Mode – bias voltage below the breakdown voltage, low gain

– avalanche photocurrent is proportional to the photon flux and the gain

Geiger Mode– bias voltage higher than the breakdown voltage, gain up to 108 from single carrier

– avalanche triggered either by single photon generated carriers or thermally generated carriers

– signal is not proportional to the incident photon flux.

– high detection efficiency of single carriers single photon counter

– to quench Geiger mode avalanche bias has to be decreased below the breakdown voltage


UV Enhanced Avalanche PhotodiodesUV Enhanced Avalanche Photodiodes

Development by Stefan Vasile et al, Radiation Monitoring Devices, Inc. Cambridge, Massachusetts, USA. (Now at aPeak, Newton, Mass.)

Small Business Innovative Research (SBIR) award motivated by an imaging Cerenkov device application (focusing DIRC). c. 1996/97-98

Design and fabrication of silicon micro-APD (APD) pixels– 20-180 µm pixels, single photon sensitivity in the 200-600 nm wavelength range.

– Q.E.= 59% at 254 nm (arsenic doping, thermal annealing)

– very high gain > 108

– Geiger mode APD array with integrated readout designed but process/funding problems.

blue-infrared UV-blue


Geiger Avalanche CharacteristicsGeiger Avalanche Characteristics

Thermal carriers trigger avalanche– dark count rate decreased using small APD

space charge region generation volume

Compatible with 5 volt logic– strong noise rate dependence

Temperature dependence factor 3 decrease for 25°C to 0°C factor 20 decrease for 25°C to -25°C

Size dependence– roughly linear with effective avalanche

region area– at room temp. predict few kHz for 100 m,

100 kHz for 500 m

Characteristics measured on a small number of samples

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5

Pulse Amplitude (V)

Cou

nts

/ sec

45V

44V

RMD Inc.

20 m diameter pixel, room temp.


Photon Detection EfficiencyPhoton Detection Efficiency

RMD Inc. RMD Inc.



Prototype Prototype APD ArrayAPD Array

• APD active area is 150 m x 150 m on 300 m pitch

• Compatible with CMOS process potential for low cost large-scale production

• 70% photon collection efficiency with fused silica micro-mirrors (for f-DIRC)

• Fabrication attempt failed 1998/99. RMD claims to have solved the problems

but no funds for a fabrication run.

RMD Inc.


Uses a large volume of cheap co-extruded scintillator bars (8m x 4cm x 1cm) with a single 1.2mmØ Y11-175 multiclad WLS fiber epoxied in extruded groove

WLS fiber is coupled to a long clear fiber and readout with a pixelated pmt

~3-4 pe/fiber at ~3.7 m including connections and pmt QE Several production facilities still operational

MINOS Scintillation SystemMINOS Scintillation System

Source: BaBar IFR Upgrade Status Report III


Short (3.7m vrs 8m) version of MINOS system with Time to the get the second coordinate

Replace the pmt with (low gain) APD : 4X higher QE Increase number of fibers to 4 : ~2X more light Increase scintillator thickness to ~2cm : ~1.5X more light Project ~ 50-60 pe at 3.7m for min. ion.

BaBar Modifications (SLAC/CalTech)BaBar Modifications (SLAC/CalTech)

Source: BaBar IFR Upgrade Status Report III


CSU+SLAC Commissioned R&D at aPeakCSU+SLAC Commissioned R&D at aPeak

P.o. placed December 2002 3.1. Package GPD pixels

– Wire bonding; – Breadboard passive quenching circuitry and GPD pixels.

3.2. Reliability evaluation – Bias several pixels at 1.1V above breakdown for 1,000 hours, document

changes in dark count rate, and failure modes, if any.

3.3. GPD performance evaluation – dark count rate vs. T–40 to 30 °C – recovery time vs. pixel area: determine if one microsecond recovery time can

be achieved with passive quenching– Gain vs. Temp. and bias Voltage– Detection Efficiency @ Room Temp.

3.4. Optical interface fabrication and assembly– Fab. and evaluate 4x1 beam couplers using GRIN and/or tapered fibers

3.5. Test GPD in Cosmic Ray Setup


50 m diameter GPD layoutProprietary. Do not distribute.


Recovery Time with Passive Quenching.Recovery Time with Passive Quenching.

1 x 10 m GPD

Simple electronics -limiting resistor 10 s quench time

475 mV

10 s


Recovery Time - Active QuenchingRecovery Time - Active Quenching

Design 1:

Design 2:

Trade off pulse amplitude with pulse width (quench the avalanche sooner)

1 s

0.5 s

2.75 V

325 mV


Active Quenching - New DesignActive Quenching - New Design

Preliminary

Design 3:

1.2 V

100 ns


Temperature DependenceTemperature Dependence


0.00

0.05

0.10

0.15

0.20

0.25

0.30

12 12.2 12.4 12.6 12.8 13Bias Voltage, Vr (V)

-43-32

-30-24

-20-13

29

23

T (°C)

Preliminary

Detection EfficiencyDetection Efficiency

Nominal operating voltage

0 200 400 600 800 1000120014001600Dark Count Rate (Hz)

-43

-20 223

T (°C)

10 m gAPD 550 nm, 150 ns laser, 10 kHz Avg. ~7 photons/pulse DE = (Illuminated Rate - Dark Rate)/10 kHzDE

Preliminary


Optical coupling to small diameter pixelsOptical coupling to small diameter pixels

Couple 4 x 1.2 mm WLS fibers to 4 x 1mm glass fibers Draw 4 glass fiber into single fiber, various exit diameters Investigate light transmission efficiency

aA

Dd

Concentration Factor, CF =

Area of input aperture (A) / Area of photodetector (a)

Coupler Transmission Factor, TF =

Intensity at input aperture / Intensity at output aperture


Optical couplers – area reductionOptical couplers – area reduction4x1 Coupler Yield

(input aperture = 2.697 mm)

0.01

0.10

1.00

1 10 100

Concentration Factor

Yie

ld

w/concentratorcoupler exit aperture = 1mmcoupler exit aperture=0.8 mmcoupler exit aperture = 0.6 mm

GPD

GPD

Single Cone Concentrator Yield

0.01

0.10

1.00

1 10 100

Concentration Factor

Yie

ld

w/concentratorw/o concentrator

GPD

Benefit from tapered fibers compared to ratio of areas is not dramatic 50-200% Preliminary measurements at aPeak are in general agreement with the model We expect to get samples at CSU soon

ratio of areas

Concentration Factor, CF Concentration Factor, CF

Tra

nsm

issi

on F

acto

r


Test Setup at CSUTest Setup at CSU

Portable dark box

Initial Tests

Cosmics rays Calibrated with well-understood

PMT at CSU Measure efficiency with

gAPD+couplers


gAPD Progress SummarygAPD Progress Summary

SLAC+CSU initiated a p.o. to jumpstart further gAPD work at aPeak.

New design from aPeak claims to be a more reliable process than the old one.

Detection efficiency in 10 micron pixels 15% at room temp., 25% at –40°C

(~kHz dark count rate).

Only modest dark count reduction with lower temperature; expected to be better in

next batch.

Active quenching circuitry provides 1s-0.1s pulse widths, no additional deadtime.

Successful fabrication of 4x1 tapered couplers – complexity trade-off unclear.

50 m diameter gAPDs breakdown; occurs predominantly at the surface. Due to

suspected design sensitivity to humidity.

New run, with better control of the surface breakdown is being fabricated. Added

backup design to layout. Larger, 150 m devices by early February, 2003.


Motivation for Geiger-mode APDs - RecapMotivation for Geiger-mode APDs - Recap

High gain (~109), > 1 volt pulses– Minimizes required electronics

Good detection efficiency in WLS range (>20%? At 550 nm)– Efficient for low light output from WLS fibers

Low supply voltage requirements (~10-40V)– Simplifies wiring harness

Minimal cooling requirements– Simplifies mechanical plant

CMOS process– “simple”– on-chip integration of readout -> cost-savings


Next StepsNext Steps

Many unanswered questions. Need to get the devices in our own lab!

Assisting aPeak with SBIR proposal.

CSU proposal to DoE Advanced Detector R&D.

Hope to provide a real HEP demonstration of utility for broad range of fiber applications.

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ALCPG, UT-Arlington January 10th 2003 Preliminary Investigations of Geiger-mode Avalanche...

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