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tracker. calorimeter. Application of novel Silicon-based photo-detectors to calorimetry and medical physics. MPPC. Nicola D’Ascenzo, Erika Garutti , Martin G ö ttlich University of Hamburg – DESY Hans-Christian Schultz-Coulon, Alexander Tadday University of Heidelberg.

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Application of novel Silicon-based photo-detectors to calorimetry and medical physics

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Application of novel Silicon-based photo-detectors to calorimetry and medical physics


Nicola D’Ascenzo, Erika Garutti, Martin Göttlich

University of Hamburg – DESY

Hans-Christian Schultz-Coulon, Alexander Tadday

University of Heidelberg

1x1 mm2 active area

3x3 mm2 active area

The Multi Pixels Photon Counter(from Hamamatsu)

The MPPC is a multi-pixel avalanche photo-diode operated in Geiger mode



Blue sensitive device:

ideal for direct r/o of plastic scint. and crystals

PET application

Erika Garutti - IEEE

MPPC characterization

intrinsic recovery time

of MPPC ~ 4 ns

measured at university ofShinshu (see talk S. Uozumi, N41-4)

response curve to a 50ns long light signal

dynamic range artificially extended for

long signals due to fast recovery time

MPPC 1600pix has ~ 6000 effective pix. for

50ns long signal

Erika Garutti - IEEE

Application in HEP calorimeters

Task: readout of active layers of highly-segmented and granular calorimeter

Single calorimeter cell readout with SiPM

3x3 cm2 x 0.5 cm thick

see talk by F. Sefkow, N13-5

CALICE test beam

CERN 2007



active layer

100x100 cm2

  • Requirements to photo-detector:

  • insensitive to B-field (~ 5T)

  • couple to organic scintillator (green/blue)

  • low noise (dark rate + cross talk above thresh.) ~ 10-4

  • detection eff. for Minimum Ionizing Particles* >95%

  •  light yield for MIP ~10 pixels

  • dynamic range ~ 100-500 MIP

~8000 SiPM


Erika Garutti - IEEE

* one MIP in 0.5 cm scintillator ~ 10000 g ( · WLS eff ~ 200 g on SiPM)

Present status

SiPM 1056 pixels

(MEPHI/Pulsar, RU)

green sensitive

Scintillator tile (Uniplast, Vladimir RU) + Green wavelength shifter fiber (Kurakay)

Readout of plastic scintillators with MPPC

study driven by calorimetry applications for a ILC detector


response to

Ru106 source

3 cm

MPPC 1600 px

operation point

w WLS fiber

light yield [pixels/MIP]

R&D: direct r/o of scintillator tiles 3x3x0.5cm3

direct r/o

Vbias - Vbreakdown [V]

MPPC directly coupled

 LY sufficient for calorimeter application

but higher LY would allow thinner tiles (lower cost)

Erika Garutti - IEEE

Readout of plastic scintillators with MPPC

MIP collection efficiency

noise spectrum

w WLS fiber

threshold at 1.5 pix

dark rate < 3 kHz

direct r/o

  • ILC requirement

  • dark rate < 300 Hz

  • MIP eff ~ 95%

    low but acceptable

MIP detection efficiency > 97%

for all r/o combinations

comparable with present status

400 px

Cut at3KHz

MIP spectrum

 larger dynamic

range than at present

1600 px

Erika Garutti - IEEE

Application in PET detectors

reduction of background

Task: identify back-to-back scattered 511 keV photons from e+e- annihilation

suppress background and determine true line of response

Background events

remove combinatorial bg by ToF meas.

Dt = 500 ps 

remove Compton-scattered g

with good energy resolution

Erika Garutti - IEEE

2 x scintillator crystals

LSO*: 1x1x15 mm3

3x3x15 mm3

LFS**: 3x3x15 mm3

emission: ~420 nm

decay time: ~40 ns

Teflon wrapping

2 x MPPC

1x1 mm2, 400 pixels

3x3 mm2, 3600 pixels

coupled with optical grease

Na22 source

Readout of scintillators crystals with MPPC

study driven by possible PET applications

  • due to high MPPT gain (7.5x105) no amplification needed  simple readout

  • energy integral on VME QDC (Lecroy 1182)

  • time resolution measurement: 4 GHz Oscilloscope, 50 ps resolution (Textronix TDS7404B)

* Lutetium OrthoSilicate from Heilger Crystals

** Lutetium Fine Silicate from Lebedev, Moskow

Erika Garutti - IEEE

Readout of scintillators crystals with MPPC

Energy resolution

3x3 mm2 systems

1x1 mm2 system

LSO Crystal

MPPC 400

MPPC 3600

blue sensitivity

~ 8% for LSO negligible

  • LSO and LFS similar performance (within syst. uncertainty of ~ ± 2%)

  • Result comparable with typical value for LSO crystals + PMT is DE/E ~ 10 % @ 511 keV

Erika Garutti - IEEE

! after 4 months of test E resolution ~ 13±2%  degradation of MPPC package or crystal surface ?

Issue of MPPC saturation

3600 pix. MPPC coupled to 3x3x15 mm3 LSO crystal

QDC spectrum

scope signal

  • integral of 511 keV g signal ~ 2000 p.e.

  • ! but: signal width ~120 ns

  • peak amplitude ~ 400 p.e.

  • below saturation estimated at > 10000 pix. for 3600 pix. MPPC and 120 ns signal

  • but MPPC response non-linear everywhere (see talk N18-2, K.C. Burr)

Erika Garutti - IEEE



Readout of scintillators crystals with MPPC

Time resolution

  • Procedure for time resolution measurement:

  • 0. store two waveforms from scope if amplitude > noise level (~ 2mV or ~10 pixels)

  • apply energy cut to exclude Compton background

  • define a timing threshold to measure time difference between signals



two waveforms from the photon peak

the voltage of the two MPPC is tuned

to give same response to 511 keV g

Erika Garutti - IEEE

# events

2 photon-peak amplitudes

Compton background


time difference [ns]

Time resolution: result

fix threshold discr.

threshold [pixels]

  • Npe = ± 1 s of photon peak

  • ~10-15% of collected events used

  • for lowest threshold FWHM ~ 650 ps

    limited by scope noise

    *no Jitter analysis package used for this analysis


Constant fraction discr.

Erika Garutti - IEEE


  • MPPC 400 and 1600pix very good candidates for highly-granular calorimeter:

    - direct coupling to plastic scintillator

    - LYMIP ~ 7 (10) p.e. with direct coupling (WLS fiber mediated coupling)

    - satisfactory MIP detection efficiency with required noise cut

  • MPPC 3600 pixels excellent performance for PET application:

    - E resolution comparable to PMT

    - t resolution < 650 ps (noise limited)

  • next step: build 2 matrices of 6x6 MPPC

    with individual readout to test

    homogeneity, stability, reproducibility,

    calibration, multi-channel system

6x6 LFS crystals 3x3x15 cm3

6x6 MPPC 3600

we would like to thank Hamamatsu

for providing the MPPC samples for this study

Erika Garutti - IEEE

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