Study of the MultiPixel Photon Counter for ILC calorimeter

1
Study of the Multi-Pixel Photon Counter for ILC
calorimeter

• Satoru Uozumi (Kobe University)
• BNM2008 _at_ Atami

• Introduction of ILC and MPPC
• The MPPC performance
• Calorimeter Prototype with MPPC
• Summary

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The International Linear Collider and ILD

• ee- collider with center-of-mass energy
• at 500 1000 GeV.
• ILD (International Large Detector) is one of the
  detector concepts proposed for the ILC
  experiment.
• Various precision measurements expected
• ee- g H, W, Z, tt, SUSY, etc
• g Multi-jets final states.

• Particle Flow Algorithm (PFA) allows precise
• jet-energy measurement
  .

ETOT pe p? pcharged hadron E? Eneutral
hadron tracks only
calorimeter only

• Separation of jet particles in the calorimeter is
  required for the PFA
• g Fine granular calorimeter is necessary.

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The ILC Scintillator-Strip Calorimeter

• One approach for the fine granular calorimeter.
• other approaches silicon strip cal, digital
  cal
• Sampling calorimeter with W/Pb - scintillator
  sandwich structure.
• Scintillator stirp structure to achieve fine
  granularity
• (strip size 1 x 4.5 x 0.20.3 cm).
• Signal of all the strips are read out
  individually..
• Therefore the number of channels is huge
• (10M for ECAL, 4M for HCAL).
• The calorimeter is placed inside 3 T
• magnetic field.

Need small, cheap, magnetic-field tolerant photon
sensor while having high performance comparable
with conventinal PMTs.
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The Multi-Pixel Photon Counter (MPPC)- A
Geiger-mode avalanche photo-diode with
multi-pixel structure -

• Belongs to Pixelated Photon
• Detector family (same as SiPM)
• Manufactured by Hamamatsu
• Photonics.
• High Gain (105106)
• Good Photon Detection
• Efficiency (15 with 1600 pixel)
• Compact
• (package size a few mm)
• Low Cost
• Insensitive to magnetic field
• Dark noise exists ( 100 kHz)
• Input vs output is non-linear

1 mm
Substrate
We are developing and studying the 1600-pixel
MPPC with Hamamatsu for the ILD calorimeter
readout.
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What are required to the MPPC ?

• Gain, Photon Detection Efficiency (P.D.E.)
  comparable to PMTs.
• Gain at least 105
• P.D.E. 20
• Dark noise rate (due to thermal electrons) and
• inter-pixel cross-talk probability as low as
  possible.
• Dark noise rate lt 1 MHz, Cross-talk probability
  a few per cent.
• Uniform performance over many pieces.
• Dynamic range enough to measure EM shower max.
• Electromagnetic shower is quite dense.
• Need dynamic range corresponds to 20005000
  photoelectrons.
• Stability Robustness.
• Tolerance to temperature change, long-term use,
• magnetic field and radiation.
• Low cost, compactness.
• Price order of 15, package size 2 x 2 mm2.
• Time resolution 1 ns
• Useful for bunch-ID, neutron separation

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Gain, Dark Noise Rate, Inter-pixel Cross-talk

• 30oC
• 25oC
• 20oC
• 15oC
• 10oC
• 0oC
• -20oC

• 30 oC
• 25 oC
• 20 oC
• 15 oC
• 10 oC
• 0 oC
• -20 oC

DV0/DT (56.00.1) mV/oC
1600 pixel

• 30 oC
• 25 oC
• 20 oC
• 15 oC
• 10 oC
• 0 oC
• -20 oC

Over-voltage

• C Pixel capacity
• V0 Breakdown voltage

• Gain comparable to conventional PMTs.
• Dark noise rate 100 kHz.
• Performance is temperature sensitive.
• gtemperature control / monitoring is
• important.

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Piece-by-piece Variation
Noise Rate 450 pieces
Gain 800 pieces
400 kHz
Noise Rate (kHz)
200 kHz
1 2 3 4 5
Over-voltage (V)

• Piece-by-piece variation is acceptably small.
• g No need for further selection or
  categorization on massive use !
• Just a small tuning of operation voltages is
  necessary.
• Further effort is ongoing by Hamamatsu to make
  the variation
• even smaller.

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Photon Detection Efficiency (PDE)
Measured by njecting same light pulse into both
MPPC and PMT, and comparing light yield.
LED
WLSF
MPPC
PMT
0.5 mm f hole
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MPPC
1600 pixel
PMT
The 1600-pixel MPPC has comparable P.D.E. with
normal photomultipliers (1520).
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Response Curve
w
LED
PMT
MPPC

• If the recovery time is very long, MPPC
• output is defined only by number of pixels.
• However if the recovery time is shorter than
• input light, dynamic range may be enhanced.

1600 pix Results
w 50 ns
24 ns
16 ns
8 ns
1600

• Linearity of 1600 pixel MPPC is not limited by
  number of pixels
• thanks to quick recovery time (4ns).
• No significant influence from changing bias
  voltage.
• Time structure of the light pulse gives large
  effects
• in non-linear region.
• Knowing time structure of input light is
  important.

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Things done / not yet done
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ECAL Prototype Performance
468 channels In total
Tungsten (3.5 mm thick)
The calorimeter with Full MPPC readout is proven
to work !
Scintillator layer (3 mm thick)
e
(1-6 GeV)
Energy Resolution for e
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Summary Prospects

• For the ILC calorimeter readout, study of the
  MPPC is extensively ongoing collaborating with
  Hamamatsu.
• Measured performance of 1600 pixel MPPC is almost
  satisfactory
• for the requirement
• Comparable gain / P.D.E. with photomultipliers.
• Low noise rate (100kHz) comparing with SiPMs.
• Small piece-by-piece variation.
• Short recovery time enhances the dynamic range
  for scintillator signal.
• The first EM calorimeter prototype with MPPC
  readout shows good and reasonable performance.
• We are still working on further study and
  improvement.
• More number of pixels for more dynamic range.
• Need to check long-term stability, robustness,
  radiation hardness.
• The MPPC is a promising device which has lots of
  excellent features !

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The MPPC Line-up

• Comparing with other Pixelated
• Photon Detectors (PPD),
• the MPPC has,
• Low dark noise
• High sensitivity to blue light
• Small device-by-device variation

From HPK catalog
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MPPC New Release Timeline(informed at NSS Nov
2007 by Hamamatsu)

• 2007 Dec 3x3 mm2 commercial sample
• 1x1mm2 SMD small package
  mechanical sample
• 2x2, 1x4 Array (3x3mm2)
  mechanical sample
• 2008 Jan SMD small package commercial samples
• 2008 Apr 3x3 mm2 product release
• Array commercial samples

1x4 array
2x2 array
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Backups
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Recovery Time Measurement
Oscilloscope view (with x63 amp)
Dt
t (nsec)
Black MPPC output for 1st Laser Green MPPC
output for 2nd Laser Red Laser LED Blue
(LaserLED) Laser net response
to 2nd laser Ratio of Blue / Green gives recovery
fraction.

• Recovery time of the 1600-pixel MPPC
• is measured to be 4 ns.
• This number is consistent with
• RC time constant of a pixel
• (C 20 fC, R 200 kW, RC 4 ns).

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Excellent photon counting ability
0,1,2,3,4,5,6,7, . . . Photoelectrons !
1 photoelectron
2 photoelectrons
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The MPPC has lots of advantages
The MPPC is a promising photon sensor, and
feasible for the GLD Calorimeter readout !
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Radiation hardness of MPPC (100 / 400 pixels)
Proton irradiation (400 pixel MPPC)
Gamma-ray
100 pixel MPPC
Neutron
3.3 x 107 n /cm
1 x 1010 n /cm