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

Electron

Hole

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

1 Nov. 2007 Erika Garutti - IEEE 3/13

Electron

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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

1 Nov. 2007 Erika Garutti - IEEE 4/13

Electron

Hole

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

Electron

Hole

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

1 Nov. 2007 Erika Garutti - IEEE 6/13

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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

1 Nov. 2007 Erika Garutti - IEEE 7/13

Electron

Hole

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

1 Nov. 2007 Erika Garutti - IEEE 8/13

Electron

Hole

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)

1 Nov. 2007 Erika Garutti - IEEE 9/13

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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 ?

1 Nov. 2007 Erika Garutti - IEEE 10/13

Electron

Hole

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

1 Nov. 2007 Erika Garutti - IEEE 11/13

Electron

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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.

1 Nov. 2007 Erika Garutti - IEEE 12/13

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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]

1 Nov. 2007 Erika Garutti - IEEE 13/13

Electron

Hole

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