Geiger-mode APD as a RICH Photodetector

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Geiger-mode APD as a RICH Photodetector
International Workshop on New Photo-Detectors
(PD07) _at_ Kobe University

• Toru Iijima
• Nagoya University

June 28, 2007
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Collaborators

• Koji Hara, Toru Iijima, Yuri Mazuka, Mio Yamaoka
• Department of Physics, Nagoya University
• Rok Dolenec, Samo Korpar, Peter Krizan, Rok
  Petotnik, Andrej Petelin
• Jozef Stefan Institute, Ljubljana
• Special Thanks to
• Belle-ACC group, KEKDTP RD-photon group
• Hamamatsu Photonics, Yuri Kudenko

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Talk Outline
Can we use Geiger-mode APD (SiPM / MPPC) as a
RICH photosensor ?

• RICH w/ Aerogel radiators
• Why Geiger-mode APD for RICH ?
• Characterization of G-APD
• Light collection system
• Expected performance
• Summary/Prospect

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Proximity Focusing Aerogel RICH

• Aerogel radiator (n1.05, 2cm) photodetector
  (Dx 5mm)
• gt4s K/p for 0.7 lt p lt 4.5 GeV/c
• Proximity focusing geometry
• No mirror complex.
• Suitable for collider and space experiments.
• Rayleigh scattering dominates in aerogel.
• ? Demand for positioning of a single photon in
  the visible wave length region.

Design values for Belle upgrade
Npe 7.5
s0 11mr
s(pix) 6.4mr
s(em) 8.6mr
s(chr) 2.0mr
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Belle PID Upgrade Option

• Barrel ? TOP (Time-Of-Propagation) Counter
• Endcap ? Proximity Focusing Aerogel-RICH

Barrel PID ? TOP
Endcap-PID ? Aerogel-RICH
Talk by K.Inami
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RICH with Multiple Radiators
NIM A548(2005)383

• Demonstration of principle
• 44 array of H8500 (85 effective area)

p/K separation with focusing configuration 4.8s
_at_4GeV/c
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RICH with Precision Timing

• Fast photon detector enables Aerogal RICH to have
  TOF info.

photosensor
_at_ 4GeV/c
In case of Belle
Cherenkov lights from aerogel
aerogel
DTring(p/K) 37ps
p/K 4GeV
DTwindow(p/K) 47ps
IP
1.8m
0.2m
Beam test result w/ Burle 85011-501
p/K separation w/ TOF
Positive ID of K/p below thereshold.
swindow 34 ps w/ glass hit
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Why SiPM/MPPC for RICH ?

• Comparison to other photodetctors

PMT MCP-PMT HPD / HAPD G-APD
Gain gt106 106 103 X10100 w/ APD 106
Quantum Eff. 20, 400nm (bialkali) 20, 400nm (bialkali) 20, 400nm (bialkali) 80, 600nmto be checked
Collection Eff. 70 60 100 50
Time resolution 300ps 30ps 150ps Depends on readout lt100ps To be checked
B-field immunity ? Depends on angle ? Depends on angle ?
Problems lifetime Noise, size

• Cons.
• Noize
• Size
• Rad. hardness ?

• Pros.
• High PDE
• B field immunity

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Possibility of G-APD for RICH

• To improve S/N
• Increase the number of signal hits/sensor by
  using light collectors (with optimization of pad
  size to the ring thickness).
• Reduce the noise by a narrow time window (lt10ns).
• Light collector serves as a light emitter for
  TOF measurement.

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G-APD Characterization

• Measured Items
• Photon-counting performance
• Timing property
• Use of timing for random noise rejection
• also for TOF measurement
• Photo-Detection Efficiency
• As a function of l
• Noise Performance

We report basic performance using 1 x 1 mm2
samples
Measured samples
MPPC from HPK
MRS-APD (CPTA) 1710 series 1.1mm2 556 pixels.
Sample H100-old H400-old H100-new1,2 H400-new1,2
Area 1.0x1.0mm2 1.0x1.0mm2 1.0x1.0mm2 1.0x1.0mm2
Production. 2005 / beg. 2005 / beg. 2006 /end. 2006 /end.
pixels 100 400 100 400
Geom. Eff. () - - 78.5 61.5

SiPM (MePhI/PULSAR) 1710 series 1.1mm2 556 pixels.
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Performance Photon-counting

• Excellent resolution to separate 0 and 1 photon
  (and more).
• Gain 1.8 x 106 at Vbias71.5V
• S/N Dmean/s 12

H100-old, Vbias71.5V, noise1.0MHz
meanped 98.9mean1pe 137.1sped 3.0
H100-old.
Pulse laser HPK PLP-02 (410nm) ALS PiL063 (636nm)
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Performance PDE

• Photo Detection Efficiency

45 at peak (460nm)
P.D.E. ()

• Higher efficiency at peak and long wave length,
  compared to conventional PMTs.
• Our result is consistent with HPK.
• Need confirmation by photo-counting to
  disentangle the effects of cross talks and
  after-pulses.

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Performance Gain vs Noise

• Recent HPK products have much lower noise rate
• lt 1/3 at the same gain.

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Performance Time Resolution
Sample MPPC Bias -71.5V Threshold 0.5pe Only
Single photon data
Measured w/ pulse laser 636 / 410nm
MPPC (HPK)
636nm
410nm
s110ps
s103ps
Time walk corrected.
MRS-APD
s140ps
s70ps
Depend on internal structure ?
Can be used for TOF measurement as well.
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Time resolution (MRS-APD)
Single photon, threshold 0.4pe
l635nm
long tail(4ns)
s69ps
39.5
40.0
40.5
41.0
41.5
TDC(ns)
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Setup for Surface Scan
_at_ Jozef Stefan Inst.
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SiPM surface sensitivity
Size 1mm Scanned with laser, resolution 5
mm Single photon response
SiPM (MePHY/Pulsar)
MRS APD by CPTA (Moscow)
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Micro Structure
SiPM (MePHY/Pulsar)
MRS APD by CPTA (Moscow)
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Hamamatsu MPPCs
400 pixels
100 pixels
1mm
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Light Guide

• Possible design
• Trapezoid
• Winston Cone
• Lens

Ex.) Trapezoid, incident at 0.3rad (max. in case
of Super-B)
?5mm ? ?1mm
?5mm ? ?2mm
CE95
CE37
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Light Guide

• Simulation conditions
• Incident angle 0.3rad
• Wave length 400nm
• No internal absorption
• n1.47 acryl ic material

• Lens (half-sphere) Trapezoid

• Trapezoid

length
5mm
5mm
2mm
2mm
length
Lgt12mm to obtain max. eff.
Lgt9mm to obtain max. eff.
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Light Guide (2)
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Expected RICH Performance
The simulation is adjusted to reproduce beam test
results with multi-anode PMT.

• A photosensor based on Light-guide Geiger-mode
  APD can give x 4 Npe (number of detected
  photons).

Should be corrected for cross talk / after-pulse
contribution (because PDE based DC current
measurement is used here).
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Effect of Noise

• Random background embeded in a simulation.
• Assume Npe 20 / ring (conservatively)

Noise rate (HPK-100) 200KHz/mm2 _at_ 106 gain.
0.8MHz for 4mm2 pad and 10ns time window
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Summary

• Geiger-mode APD is very attractive device as a
  photosensor for a RICH with aerogel radiator.
• High PDE ? Significant increase in Npe (x 4
  possible).
• Good time resolution (s100ps /p.e.) ? RICH w/
  TOF
• Free from magnetic field ? Large advantage !
• Noise rate has been reduced significantly and in
  a tolerable region (lt1MHz/pad) for recent
  products from HPK .
• ? Very encouraging !
• Light colletction based on tapered lightguide
  (lens) will be useful to increase the detection
  area, and hence improve S/N.
• Devices with larger size (?35mm) are highly
  welcome.
• We are starting to measure ?3mm sample from HPK.

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Backup
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Light absorption in silicon
Light absorption length a f (l)
l (nm) a(mm) s(ps) tail(ns)
410 0.16 140 0.5
639 3.65 70 4
Red(l635nm) absorbed in Geiger region
?make prompt signals absorbed in drift
region ?make slow signals, long
tail Blue(l405nm) absorbed before reach to
Geiger region ?TDC has short tail, worse
resolution in Geiger region
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Temperature Dep. of Noise
MPPC
MRS-APD
Geiger mode APD?????? ???? ????????? ?
???????????? ? ????????
(deg.)

• 0??????2030????
• MRS-APD MPPC
• 300kHz_at_ 0? 200kHz _at_ 0?

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Performance Gain vs Noise (MRS-APD)
Noise (kHz)
Gain (x 103)
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Plan

• Further measurements of samples
• HPK starts to provide 3x3mm2 samples.
• Better understanding of critical properties.
• Feedback to producers.
• Light-guide design
• Measurements with a test sample.
• Method to produce the assembly.
• How to make the light-guide (LG) array.
• Optical connection between LG and SiPM/MPPC.
• Readout Electronics

Photo from the talk by Sato-san (HPK) at the
photosensor WS (Dec.7-8,2006).