Study of the Multi-Pixel Photon Counter for ILC calorimeter Satoru Uozumi (Kobe University) BNM2008 @ Atami Introduction of ILC and MPPC The MPPC performance.

Study of the Multi-Pixel Photon Counter for ILC calorimeter

Satoru Uozumi (Kobe University)

BNM2008 @ Atami

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

The International Linear Collider and ILD

ETOT = pe+ p + pcharged hadron + E + Eneutral hadron

[ tracks only] [calorimeter only]• Separation of jet particles in the calorimeter is required for the PFA

Fine granular calorimeter is necessary.

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

• e+e- 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:

– e+e- H, W, Z, tt, SUSY, etc … Multi-jets final states.

• 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 0.2~0.3 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.

The ILC Scintillator-Strip Calorimeter

Need small, cheap,magnetic-field tolerant

photon sensorwhile having high performance

comparable with conventinal PMTs.

• Belongs to Pixelated Photon Detector family (same as SiPM)• Manufactured by Hamamatsu Photonics.• High Gain (105~106)• 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

The Multi-Pixel Photon Counter (MPPC)- A Geiger-mode avalanche photo-diode with multi-pixel structure -

We are developing and studying the1600-pixel MPPC with Hamamatsufor the ILD calorimeter readout.

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 < 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 2000~5000 photoelectrons.

• Stability & Robustness.Tolerance to temperature change, long-term use,magnetic field and radiation.

• Low cost, compactness.– Price order of $1~5, package size ~ 2 x 2 mm2.

• Time resolution ~ 1 ns– Useful for bunch-ID, neutron separation

•30oC•25oC•20oC•15oC•10oC•0oC•-20oC

– C … Pixel capacity

– V0 … Breakdown voltage

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

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

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

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

Over-voltage

1600 pixel

V0/T= (56.0±0.1) mV/oC

Piece-by-piece Variation

• Piece-by-piece variation is acceptably small. 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.

Nois

e R

ate

(kH

z)

Over-voltage (V)1 2 3 4 5

200 kHz

400 kHz

Gain – 800 pieces Noise Rate450 pieces

Photon Detection Efficiency (PDE)

MPPC

0.5 mm holePMT

LEDWLSF

PMTPMTep

MPPCep

MPPC PDEN

NPDE

..

..~ 16 %

Measured by njecting same light pulse into both MPPC and PMT,

and comparing light yield.

MPPC

PMT

The 1600-pixel MPPC has comparable P.D.E.with normal photomultipliers (15~20%).

1600 pixel

Response Curve•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.

• 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.

8 ns16 ns

24 ns

w = 50 ns

1600

PMTLED

w

MPPC

1600pixSimulationSlow recovery

1600

1600 pixResults

Performance status

Gain 105~106 OK

Photon Detection Eff. ~0.2 for 1600 pix. MPPC OK

Dark Noise Rate ~ 100 kHz OK

Photon counting Great OK

Bias voltage ~ 70 V OK

Size Compact OK

Dynamic range Determined by # of pixels and recovery time

underway

Cost Expected to be < $10 Negotiating

Long-term Stability Unknown To be checked

Robustness Unknown, presumably good underway

Radiation hardness Concerned underway

B field Expected to be Insensitive Looks OK

Timing resolution Expected to be 0.1~1 ns To be checked

Things done / not yet done

ECAL Prototype PerformanceMPPCs (1600 pixels)

Scintillator strip(1 x 4.5 x 0.3 cm)

Frame

WLS fibre

Tungsten(3.5 mm thick)

Scintillator layer(3 mm thick)e+

468 channelsIn total

(1-6 GeV)

Linearity

+ 1%

Energy Resolution for e+

The calorimeter with Full MPPC readoutis proven to work !

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 !

Number of pixels 100 400 1600

Sensor size 1 x 1 mm2

Nominal Bias Volt. 70 10 V 77 10 V

Gain (x 105) 24.0 7.5 2.75

Noise Rate (kHz) 400 270 100

Photon Detection Efficiency 65 % 50 % 25 %

Temperature dependence (V0/T) 50 mV / oC

The MPPC Line-upComparing with other PixelatedPhoton Detectors (PPD),the MPPC has,• Low dark noise• High sensitivity to blue light• Small device-by-device variation

From HPK catalog

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

Backups

Recovery Time Measurement

1600 pixel

t (nsec)

Oscilloscope view (with x63 amp)

t

Black … MPPC output for 1st LaserGreen … MPPC output for 2nd LaserRed … Laser + LEDBlue … (Laser+LED) – Laser = net response to 2nd laser

Ratio of Blue / Green givesrecovery 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 k, RC ~ 4 ns).

Excellent photon counting ability

0,1,2,3,4,5,6,7, . . . Photoelectrons !

1 photoelectron

2 photoelectrons

Photomultiplier MPPC

Gain ~106 105~106

Photon Detection Eff. 0.1 ~ 0.2 ~0.2 for 1600 pix. MPPC

Response fast fast

Photon counting Yes Great

Bias voltage ~ 1000 V ~ 70 V

Size Small Compact

B field Sensitive Insensitive

Cost Very expensive ! Not very expensive

Dynamic range Good Determined by # of pixels

Long-term Stability Good Unknown

Robustness decent Unknown, presumably good

Noise (fake signal by thermions)

Quiet Noisy (order of 100 kHz)

The MPPC has lots of advantages

The MPPC is a promising photon sensor, and feasible for the GLD Calorimeter readout !

Radiation hardness of MPPC (100 / 400 pixels)

Gamma-ray

Neutron3.3 x 107 n /cm 1 x 1010 n /cm

Proton irradiation(400 pixel MPPC)

100 pixel MPPC