Nicola DAscenzo, Erika Garutti, Martin Göttlich University of Hamburg – DESY Hans-Christian...

Nicola D’Ascenzo, Erika Garutti, Martin Göttlich

University of Hamburg – DESY

Hans-Christian Schultz-Coulon, Alexander Tadday

University of Heidelberg

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

calorimeter

tracker

MPPC

1 Nov. 2007 Erika Garutti - IEEE 2/13

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The Multi Pixels Photon Counter(from Hamamatsu)

# Pixels (size mm2)

Pieces Bias Dark Rate

>0.5pixels

Dark Rate

> 1.5 pixels

Gain

(10^5)

400 (1x1) 5 76 V 220-250 kHz 9-10 kHz 7.4- 7.5

1600 (1x1) 5 78 V 50-60 kHz 0.05-0.1 kHz 2.6-2.7

3600 (3x3) 5 70 V 3.2-3.3 MHz 320-330 kHz 7.4-7.5

Blue sensitive device:ideal for direct r/o of plastic scint. and crystals

1x1 mm2 active area

3x3 mm2 active area

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

PET application

calorimetryapplication


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MPPC characterization

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

intrinsic recovery time of MPPC ~ 4 ns

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


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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

prototypeactive layer100x100 cm2

DATA CALICE test beamCERN 2007

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

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

~8000 SiPMoperated

see talk by F. Sefkow, N13-5

Erika Garutti - IEEE 5/13

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Readout of plastic scintillators with MPPCstudy driven by calorimetry applications for a ILC detector

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

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

Present statusSiPM 1056 pixels(MEPHI/Pulsar, RU)green sensitive

3 cm

MPPC directly coupled

response to Ru106 source

MPPC 1600 px

operation point

lig

ht

yie

ld [

pix

els/

MIP

]

MIP

Vbias - Vbreakdown [V]

LY sufficient for calorimeter applicationbut higher LY would allow thinner tiles (lower cost)

w WLS fiber

direct r/o


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Cut at 3 KHz

400 px

1600 px

Readout of plastic scintillators with MPPCMIP collection efficiency

threshold at 1.5 pixdark rate < 3 kHz

noise spectrum

MIP spectrum

MIP detection efficiency > 97%for all r/o combinationscomparable with present status

larger dynamic range than at present

ILC requirement dark rate < 300 HzMIP eff ~ 95%low but acceptable

w WLS fiber

direct r/o


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Application in PET detectorsreduction 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 Compton-scattered with good energy resolution

remove combinatorial bg by ToF meas.

t = 500 ps


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Readout of scintillators crystals with MPPCstudy driven by possible PET applications

* Lutetium OrthoSilicate from Heilger Crystals** Lutetium Fine Silicate from Lebedev, Moskow

2 x scintillator crystalsLSO*: 1x1x15 mm3

3x3x15 mm3 LFS**: 3x3x15 mm3

emission: ~420 nmdecay time: ~40 ns

Teflon wrapping

2 x MPPC1x1 mm2, 400 pixels3x3 mm2, 3600 pixels

coupled with optical grease

Na22 source

• 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)


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• LSO and LFS similar performance (within syst. uncertainty of ~ ± 2%)• Result comparable with typical value for LSO crystals + PMT is E/E ~ 10 % @ 511 keV

Readout of scintillators crystals with MPPCEnergy resolution

MPPC 400

LSO Crystal

1x1 mm2 system 3x3 mm2 systems

MPPC 3600

~ 8% for LSO negligible blue sensitivity

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


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Issue of MPPC saturation

integral of 511 keV signal ~ 2000 p.e.

! but: signal width ~120 nspeak amplitude ~ 400 p.e.

below saturation estimated at > 10000 pix. for 3600 pix. MPPC and 120 ns signalbut MPPC response non-linear everywhere (see talk N18-2, K.C. Burr)

3600 pix. MPPC coupled to 3x3x15 mm3 LSO crystal

QDC spectrum

scope signal


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Readout of scintillators crystals with MPPCTime resolution

Procedure for time resolution measurement:0. store two waveforms from scope if amplitude > noise level (~ 2mV or ~10 pixels)1. apply energy cut to exclude Compton background 2. define a timing threshold to measure time difference between signals

tcut

2.

two waveforms from the photon peakthe voltage of the two MPPC is tunedto give same response to 511 keV

Npe1.


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Time resolution: result

• Npe = ± 1 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

Background

# ev

ents

time difference [ns]

2 photon-peak amplitudes

Compton background

Photoelectric

fix threshold discr.

Constant fraction discr.

threshold [pixels]


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Conclusions

• 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 MPPC 3600

6x6 LFS crystals 3x3x15 cm3

we would like to thank Hamamatsu

for providing the MPPC samples for this study

Nicola DAscenzo, Erika Garutti, Martin Göttlich University of Hamburg – DESY Hans-Christian...

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