The Multi-Pixel Photon Counter for the GLD Calorimeter Readout

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The Multi-Pixel Photon Counter for the GLD
Calorimeter Readout

• Jul-20 2006 LCWS_at_UBC
• Satoru Uozumi
• University of Tsukuba, Japan
• for the GLD Calorimeter group

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The GLD Calorimeter

• Sampling calorimeter with Pb/W - scintillator
  sandwich structure with WLSF readout
• Particle Flow Algorithm (PFA) needs particle
  separation in the calorimeter
• Fine granularity with strip/tile scintillator
• Huge number of readout channels
• 10M (ECAL) 4M (HCAL) !
• 10k for muon detector
• Used inside 3 Tesla solenoid

Need new photon sensor which is compact and
low-cost, but has enough performance.
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The Multi-Pixel Photon Counter named by
Hamamatsu (Silicon Photomultiplier general
name) is a novel type semiconductor photon sensor
400 pixels
1 mm
20100 mm
8 mm
Depletion region 2 mm
Substrate
Si Resistor
1600 pixels
Vbias
Guard ring n-
p
n
Al conductor
p-
substrate p
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The MPPC performance

PMT MPPC
Gain 106 105106
Photon Detection Efficiency 0.1 0.2 0.1 0.4
Response fast fast
Photon counting Yes Great
Bias voltage 1000 V 30 70 V
Size Small Compact
B field Sensitive No influence
Cost Not low Low (110?)
Dynamic range Good Not so good
Stability Good Unknown, maybe good
Noise (fake signal by thermions) Quiet Noisy (order of MHz)
The MPPC looks feasible for theGLD Calorimeter
readout!
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Required performance for the GLD Calorimeter

• Gain Best to have 106 , at least 105
• Dynamic range can measure 1000 p.e.
• satisfactory to measure EM shower maximum
• need gt 2500 pixels
• Photon Detection Efficiency 30
• to distinguish MIP signal
• Noise rate 1 MHz (threshold 0.5 p.e.,
• threshold 1.5 p.e is also
  acceptable)
• good uniformity, small cross-talk
• Timing Resolution 1 nsec
• Necessary for bunch ID, slow neutron separation
• Sensor area 1.5 x 1.5 mm
• suitable for 1.5 mmf fiber
• Should be stable against bias voltage /
  temperature / time

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RD Status _at_ GLD Calorimeter

• The MPPC performance looks feasible for the GLD
  calorimeter readout, but still not sufficient.
• Need study and improvement of the fundamental
  property to achieve our goal.
• Now we are measuring performance of 400 / 1600
  pixel MPPC prototypes provided by Hamamatsu.
• Based on its results, we provide feedback to
  Hamamatsu to have improved sample.

Evaluate performance of the MPPC
prototypes Provide feedback to HPK Improved
samples from HPK
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Current Resultsof the Performance Study
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Gain vs Bias Voltage
Green LED
MPPC
400 pixel with x63 amp
Pedestal

• C Pixel capacity
• V0 Geiger-mode starting voltage
• Typically 5-12 x 105(400 pixel),
  
• 1.5-3 x 105(1600 pixel)
• Need precise control of Vbias to have stable gain

1 p.e signal
400 pixel x 2
1600 pixel
C 0.13 0.01 pF V0 67.60 0.01 V
C 0.02 0.01 pF V0 67.40 0.02 V
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Noise Rate (1600 pixel)
Count rate of noises above threshold (gt0.5 /
1.5 photoelectrons)

threshold0.5pe
thr1.5pe
2 MHz
1 MHz
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• Laser Bench Test

• YAG Laser (? 532 ?m) with microscope
• Pulse width 2 nsec
• Laser spot size 1 ?m
• Moving stage pos. resolution 0.02mm
• Can perform precise pinpoint scan with the
  well-focused laser

1600 pixel
25mm
Laser Spot (before light reduction)
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Scan within a pixel- Detection Efficiency -
Num. of gt 1 pix. fired events
Num. of all events
Vbias 70 V
-71.0V -70.0V -69.5V
1600 pixel Preliminary
One pixel
x-point (2 mm pitch)

• Geometrical acceptance within a pixel 20
• Variation within an active region 7-13

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Scan within a pixel- Gain -
y-point (1 mm pitch)
Active area only
1600 pixel Preliminary
x-point (1 mm pitch)

• Shows inverted-U shape
• Variation 2-3

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More Laser Results?Cross-talkAll-pixel scan
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Summary Plans

• MPPC is a great device, and feasible for the GLD
  calorimeter readout.
• Extensive RD is ongoing collaborating with the
  Hamamatsu Photonics.
• We still have lots of things to do in a short
  term
• Need more study of fundamental properties
• (Photon Detection Efficiency, Linearity, etc)
• Stability, Robustness, B-field tolerance
• Time resolution
• Device-by-device variation
• Current target is a beam test of EM calorimeter
• module with the full MPPC readout (next talk).

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Backups
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() Multi-pixels
PMT MCP-PMT HPD APD MPPC (SiPM)
HV 1kV 1kV 8kV300V 300V 50V
Gain 106 106 105 102 106
Noize lt10Hz lt10Hz ?? Very Sensitive 1MHz
B Filed NA OK OK OK OK
Price/channel 25 60 --- 30 10
QE 15 8 8 70 1020
RD No marginal necessary Marginal necessary
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Setup
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b-ray test (in 2005)

• Practical test with Scintillator WLSF
• Compare performance with PMT

Co60
Preliminary result
b - ray
Device of p.e. detected of photons from fiber
MPPC (100 pix) 6.10.7 (pixels) 2810
PMT 5.80.5 (p.e.) 296
MPPC or PMT
(1mmf)
Scintilltor (10x40x2mm)
MPPC performance is comparable with PMT for
the practical use.