Recent news about SiPM based applications R&D in DESY

Nicola D’AscenzoUniversity of Hamburg - DESY

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Calorimetry at International Linear Collider

The ILC physics requires a calorimeter with:

1. High granularity (Good jet energy resolution)

2. Ermeticity and good missing energy resolution

3. Compactness (The detector has to stay inside the magnetic coil)

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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The scintillator tile hadron calorimeter

• Sampling calorimeter : absorber stainless steel, active medium plastic organic scintillator.

• Along the magnetic field direction it extends in -220 cm < z <220 cm

• It covers the detector along the radius in the region 180 cm< r < 290 cm

• The test beam prototype: 1 m3 .• Test beam prototype : 38 layers, 216

channel per layer.

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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SiPM: a good photodetector for hadron calorimetry

The good SiPM for this application:

1. Low noise above the suggested cut on the mip spectrum (Controlled dark rate and cross talk)

2. Light Yield not exceeding the saturation behaviour of the device.

3. Stable and controlled production

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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The scintillator direct readout

The direct readout is easier to extend toa large scale production.The solution which respects the required bounds on the parameters:

1. Blue Sensitive? 2. Green sensitive and large?

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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The MPPC by Hamamatsu

Blue sensitive Silicon PhotoMultiplier,Suitable for the direct coupling

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Direct readout with MPPC

• Readout of a plastic scintillator tile directly and comparison with the mediated green fiber

• Tile wrapped with a 3M reflector. In case of the direct readout, only a window of 1mm x 1mm is open in front of the MPPC

• Source: Ru106 • Integration gate 80 ns• External trigger

(Photomultiplier tube) • Reproducibility of the

measurement +- 3%• systematic (coupling,

positioning etc ...)

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Direct readout with MPPC : Most Probable Value of the mip response

spectrum

400 px 1600 px

The green dots correspond to the traditional wavelength shifter fiber readout. The performances of the MEPHI SiPMs used are totally reproduced.

THe blue dots correspond to the direct readout: a good light yield is obtained

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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The direct readout with MPPC: mip collection efficiency

Cut at 3 KHz

400 px

1600 px

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Direct Readout with MPPC: application to electromagnetic calorimetry

GLD-CAL group, Kobe University

This is the first attempt of using MPPC in the direct readout configuration in the calorimeter design.

The study of the impact of this technology in the physics reconstruction is still in progress.

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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The direct readout: discussion

• The direct readout looks promising for the simplification of the design of the calorimeter and the extension of the concept to a large scale.

• Still some conceptual problems:– Uniformity of the light response according to the impact

of the particle in the scintillator• Montecarlo studies and experiments will test this

soon• What is the effect on the performance of the

calorimeter?– What is the best position for the coupling?

• The blue sensitive MPPC opened good perspectives to the design of calorimeters: ready to test new photodetectors.

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Application of MPPC in PET: motivations and goals

• The calorimeter si just a big PET machine:– The hadron calorimeter has

milions of channels– The hadron calorimeter has a very

high granularity: imaging detector!

• It is only needed to:– Change scintillator (from organic

to inorganic)– Change granularity (from 3x3 cm2

to ~1x1 mm2)

• The technology and the needs of the photodetector are the same !

• Energy resolution and timing measurements

This study is just at the beginning!

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Application of MPPC in PET: setup

2 LSO Crystals of 1mm x 1mm (3mm x3mm)Read out by 1x1 mm (3x3 mm) Hamamatu MPPC No amplification needed!!!

QDC

&

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Application of MPPC in PET: energy resolution

3mmx3mm LSO crystal

Coupled with a 3mmx3mm

MPPC

1mmx1mm LSO crystal

Coupled with a 1mmx1mm

MPPC Resolution =14 %

Resoultion =20 %

PRELIMIN

ARY

PRELIMIN

ARY

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Application of MPPC in PET: timing resolution

Cut at 7 photoelectrons

PRELIMIN

ARY

4 GHz Digital oscilloscope used to calculate the time difference (50 ps precision)

Still the system needs to be improved with a lower discrimination.

13 Giugno 2007 I Workshop Italiano su nuovi photodetectors

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Application of MPPC in PET:discussion

• The application of MPPC in Positron Emission Tomography looks promising: the blue sensitivity of the photodetectors is excellent.

• In DESY we will test different combinations of crystals and photodetectors: YAP, LYSO... With SenSL, new Hamamatsu ....

• The enrgy resolution measurement will be continuosly improved in reproducibility and stability of the system

• Timing measurement (important also for time of flight) is currently beeing improved.

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After the serious conclusions...

The spin off of the technlogical developement around the new high energy Phyics experiments is very important...

We are dedicating lots of efforts in order to keep open and fruictful the interplay between high energy physics and medical physics.

If we will not find the Higgs Boson, at least, we can tell we were useful for something...