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Preliminary Investigations of Geiger

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Preliminary Investigations of
Geiger-mode Avalanche Photodiodes
for use in HEP Detectors
David Warner, Robert J. Wilson
Department of Physics
Colorado State University
ALCPG, UT-Arlington
January 10th 2003
Outline
пЃ¬
Motivation
пЃ¬
Avalanche Photodiodes
пЃ¬
Characteristics
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R&D Plans
пЃ¬
Conclusions
R.J.Wilson, Colorado State University
Motivation
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Scintillating fiber, or WLS readout of scintillator strips basic
component of several existing detectors (MINOS, CMS-HCAL)
пЃ¬
Standard photodetector – photomultiplier tubes, great devices but…
–
“Expensive” (including electronics etc.),
– Bulky, magnetic field sensitive…
пЃ¬
For the next generation would like a photon detector to be:
– Cheaper
– Compact? Low mass? Magnetic field insensitive? Radiation hard?
пЃ¬
Future experiments
– BaBar upgrade - endcap?
– Future e+e- Linear Collider? LHC?
– Nuclear physics? Space-based (NASA)?
R.J.Wilson, Colorado State University
Silicon Avalanche Photodiodes (APD)
пЃ¬
Solid state detector with internal gain.
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Avalanche multiplication
пЃ¬
пЃ¬
–
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 пѓћ single photon counter
–
to quench Geiger mode avalanche bias has to be decreased below the breakdown voltage
R.J.Wilson, Colorado State University
UV Enhanced Avalanche Photodiodes
пЃ¬
Development by Stefan Vasile et al, Radiation Monitoring Devices, Inc.
Cambridge, Massachusetts, USA. (Now at aPeak, Newton, Mass.)
пЃ¬
Small Business Innovative Research (SBIR) award motivated by an imaging
Cerenkov device application (focusing DIRC). c. 1996/97-98
пЃ¬
Design and fabrication of silicon micro-APD (mAPD) pixels
–
20-180 Вµm 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
R.J.Wilson, Colorado State University
Geiger Avalanche Characteristics
Thermal carriers trigger avalanche
–
пЃ¬
Temperature dependence
Size dependence
–
–
пЃ¬
45V
30
strong noise rate dependence
п‚» factor 3 decrease for 25В°C to 0В°C
п‚» factor 20 decrease for 25В°C to -25В°C
пЃ¬
20 mm diameter pixel,
room temp.
35
Compatible with 5 volt logic
–
пЃ¬
40
dark count rate decreased using small APD
space charge region generation volume
roughly linear with effective avalanche
region area
at room temp. predict few kHz for 100 mm,
п‚» 100 kHz for 500 mm
Characteristics measured on a small
number of samples
Counts / sec
пЃ¬
25
44V
20
15
10
5
0
0
1
2
3
4
5
Pulse Amplitude (V)
RMD Inc.
R.J.Wilson, Colorado State University
Photon Detection Efficiency
0
C 52 ,mn 074
es lup/snotohp 5.1
570 nm, 25 0C
1.5 photons/pulse
54
04
53
DE(%)
20
)%(ED
03
52
02
51
25
15
10
01
5
0
64
54
RMD Inc.
44
34
) tl o v(rV
24
14
5
0
40
04
41
42
43
44
45
Vr(volt)
RMD Inc.
R.J.Wilson, Colorado State University
R.J.Wilson, Colorado State University
Prototype mAPD Array
RMD Inc.
•
•
•
•
APD active area is 150 mm x 150 mm on 300 mm pitch
Compatible with CMOS process пѓћ 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.
R.J.Wilson, Colorado State University
MINOS Scintillation System
Uses a large volume of cheap co-extruded scintillator bars (8m x 4cm x 1cm)
with a single 1.2mm� Y11-175 multiclad WLS fiber epoxied in extruded groove
пЃ¬ WLS fiber is coupled to a long clear fiber and readout with a pixelated pmt
пЃ¬ ~3-4 pe/fiber at ~3.7 m including connections and pmt QE
пЃ¬ Several production facilities still operational
пЃ¬
Source: BaBar IFR Upgrade Status Report III
R.J.Wilson, Colorado State University
BaBar Modifications (SLAC/CalTech)
пЃ¬
пЃ¬
пЃ¬
пЃ¬
пЃ¬
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.
Source: BaBar IFR Upgrade Status Report III
R.J.Wilson, Colorado State University
CSU+SLAC Commissioned R&D at aPeak
пЃ¬
P.o. placed December 2002
пЃ¬ 3.1. Package GPD pixels
–
–
пЃ¬
3.2. Reliability evaluation
–
пЃ¬
–
–
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
–
пЃ¬
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
–
–
пЃ¬
Wire bonding;
Breadboard passive quenching circuitry and GPD pixels.
Fab. and evaluate 4x1 beam couplers using GRIN and/or tapered fibers
3.5. Test GPD in Cosmic Ray Setup
R.J.Wilson, Colorado State University
50 mm diameter GPD layout
Proprietary. Do not distribute.
R.J.Wilson, Colorado State University
Recovery Time with Passive Quenching.
1 x 10 mm GPD
10 ms
475 mV
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пЃ¬
Simple electronics -limiting resistor
10 ms quench time
R.J.Wilson, Colorado State University
Recovery Time - Active Quenching
Design 1:
1 ms
2.75 V
Design 2:
0.5 ms
325 mV
Trade off pulse amplitude with pulse width (quench the avalanche sooner)
R.J.Wilson, Colorado State University
Active Quenching - New Design
Design 3:
100 ns
1.2 V
R.J.Wilson, Colorado State University
Temperature Dependence
R.J.Wilson, Colorado State University
Detection Efficiency
10 mm f gAPD
пЃ¬ 550 nm, 150 ns laser, 10 kHz
пЃ¬ Avg. ~7 photons/pulse
пЃ¬ DE = (Illuminated Rate - Dark Rate)/10 kHz
пЃ¬
DE
0.30
T (В°C) -43
-32
-30
-24
-20
-13
2
9
23
0.25
0.20
0.15
-43
-20
2
23
T (В°C)
0.10
Nominal
operating voltage
0.05
0.00
12
12.2
12.4
12.6
12.8
13
Bias Voltage, Vr (V)
0 200 400 600 800 1000120014001600
Dark Count Rate (Hz)
R.J.Wilson, Colorado State University
Optical coupling to small diameter pixels
пЃ¬
Couple 4 x 1.2 mm WLS fibers to 4 x 1mm glass fibers
пЃ¬ Draw 4 glass fiber into single fiber, various exit diameters
пЃ¬ Investigate light transmission efficiency
D
d
A
a
Concentration Factor, CF =
Area of input aperture (A) / Area of photodetector (a)
Coupler Transmission Factor, TF =
Intensity at input aperture / Intensity at output aperture
R.J.Wilson, Colorado State University
Transmission Factor
Optical couplers – area reduction
ratio of areas
Concentration Factor, CF
пЃ¬
пЃ¬
пЃ¬
Concentration Factor, CF
Benefit from tapered fibers compared to ratio of areas is not dramatic п‚» 50-200%
Preliminary measurements at aPeak are in general agreement with the model
We expect to get samples at CSU soon
R.J.Wilson, Colorado State University
Test Setup at CSU
Portable dark box
пЃ¬
Cosmics rays
пЃ¬ Calibrated with well-understood
PMT at CSU
пЃ¬ Measure efficiency with
gAPD+couplers
Initial Tests
R.J.Wilson, Colorado State University
gAPD Progress Summary
пЃ¬
SLAC+CSU initiated a p.o. to jumpstart further gAPD work at aPeak.
пЃ¬
New design from aPeak claims to be a more reliable process than the old one.
пЃ¬
Detection efficiency in 10 micron pixels 15% at room temp.,  25% at –40°C (~kHz
dark count rate).
пЃ¬
Only modest dark count reduction with lower temperature; expected to be better in
next batch.
пЃ¬
Active quenching circuitry provides 1ms-0.1ms pulse widths, no additional deadtime.
пЃ¬
Successful fabrication of 4x1 tapered couplers – complexity trade-off unclear.
пЃ¬
50 mm diameter gAPDs breakdown; occurs predominantly at the surface. Due to
suspected design sensitivity to humidity.
пЃ¬
New run, with better control of the surface breakdown is being fabricated. Added
backup design to layout. Larger, 150 mm devices by early February, 2003.
R.J.Wilson, Colorado State University
Motivation for Geiger-mode APDs - Recap
пЃ¬
High gain (~109), > 1 volt pulses
–
пЃ¬
Good detection efficiency in WLS range (>20%? At 550 nm)
–
пЃ¬
Simplifies wiring harness
Minimal cooling requirements
–
пЃ¬
Efficient for low light output from WLS fibers
Low supply voltage requirements (~10-40V)
–
пЃ¬
Minimizes required electronics
Simplifies mechanical plant
CMOS process
–
–
“simple”
on-chip integration of readout -> cost-savings
R.J.Wilson, Colorado State University
Next Steps
пЃ¬
Many unanswered questions. Need to get the devices in our own lab!
пЃ¬
Assisting aPeak with SBIR proposal.
пЃ¬
CSU proposal to DoE Advanced Detector R&D.
пЃ¬
Hope to provide a real HEP demonstration of utility for broad range of
fiber applications.
R.J.Wilson, Colorado State University
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