Application of new photo-detectors to calorimetry and medical physics

Nicola D’Ascenzo, Erika Garutti University of Hamburg – DESY

Alexander TaddayUniversity of Heidelberg

27 June 2007 PD07 Kobe 2

The Geiger Mode Avalanche Photodiode

• High gain (Typically 105 - 106)• Low bias voltage (30 V -70 V)• Small area (1 mm2)• Up to 1600 pixels per mm2 • Not sensitive to magnetic field

Why is this detector so interesting ?

Devices from MEPHI, Hamamatsu and SensLcurrently avalaible in DESY:Good possibility of comparison and testing

27 June 2007 PD07 Kobe 3

ILC Physics: challenges in calorimetry

• ILC physics places premium on jet measurements and flavoure tagging, in an environment where event reconstruction is possible

– tth 8 jets– hZ 2l + 2 jets, 4 jets– hhZ 2l + 4 jets, 6jetsAim to fully reconstruct final state

• + SUSY, quark, τ tagging, lepton/hadron id

• Missing energy signatures of SUSY and extra-dimensions

, ZZeeWWee

E%30E%60This requires a calorimeter which is:COMPACT – Inside the magnetic coilHIGH GRANULAR – Imaging calorimeterHERMETIC

• Electron-positron accelerator

• Energy: 500 GeV up to 1 TeV

27 June 2007 PD07 Kobe 4

The scintillator tile hadron calorimeter• Sampling calorimeter : absorber

stainless steel, active medium plastic organic scintillator.

• High granular, compact, hermetic.• 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.• Fully equipped with MEPHI/PULSAR

SiPM

TPCTPC

ECALECALHCALHCAL

27 June 2007 PD07 Kobe 5

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, but high enough to detect a m.i.p. with at least 95% efficiency. (good PDE in the light peak spectrum)

3. Stable and controlled production4. Compactness, unsensitivity to magnetic

field up to 5 T, radiation hardness ...

Test Beam CERN. 10 GeV Pion in the HCAL

The minimum signal in 1 cell is a m.i.p.

The test beam prototype, fully equipped woth MEPHI SiPMs,

is showing good performances for a long time operation

of the device: the high granular calorimeter operated with SiPMs is starting to be a suitable option.

Test Beam data are under analysis

27 June 2007 PD07 Kobe 6

New approach to the calorimeter design:the direct readout of the scintillator

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

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

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

In order to:• Assure Light yield (MEPHI SiPM is green sensitive)• Assure Light collection uniformity

Present status R&D

27 June 2007 PD07 Kobe 7

The MPPC produced by Hamamatsu

Blue sensitive Multi Pixel Photon Counter

Pixels Avalaible Op. Voltage

Dark Rate>0.5pixels

Dark Rate> 1.5 pixels

Gain(10^5)

400 (1x1) 5 76 V 220 – 250 kHz

9 K – 10 K 7.4- 7.5

1600 (1x1) 5 78 V 50 K– 60K 0.05K 0.09K 2.6-2.7

3600 (3x3) 5 70 V 3 .2 – 3.3 M 320K - 330K 7.4-7.5

27 June 2007 PD07 Kobe 8

Direct readout with MPPC

• Readout of a plastic scintillator tile directly and comparison with 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 ...)

27 June 2007 PD07 Kobe 9

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

400 px 1600 px

Direct (Blue dots) and Wavelength shifter mediated readout (Green dots) .

Light Yield in the calorimeter prototype

27 June 2007 PD07 Kobe 10

Direct readout with MPPC: mip collection efficiency

Cut at 3 KHz

400 px

1600 px

The cut at 3 KHz (as in the actual prototype) corresponds to a low number of pixels(low dark rate and cross talk). The efficiency is, then, always more than 97 %.

27 June 2007 PD07 Kobe 11

3x3 MPPC: direct readout

• About 50 p.e. Per MPV • Good single photoelectron resolution!

LED Light

Ru106 response

27 June 2007 PD07 Kobe 12

The direct readout of MPPC: discussion

• MPPCs are a good starting point for the discussion of the direct readout in the hadron calorimetry:– High PDE in the blue emission of the scintillator: good m.i.p. signal

determination. – Low dark rate and cross talk: cut for noise even for the stricter

requirement of ILC (300 Hz), without loosing m.i.p efficiency (>95%)– High dinamic range (up to 1600 pixels)

• Some points under investigation:– Uniformity of the light collection

• Done in laboratory setup in ITEP and LNF-FRASCATI• Real prototype (ECAL): Japan

– Radiation hardness• Under investigation in ITEP

• For a thinner scintillator solution, the tested samples seem to have a too low Light Yield in this readout configuration.

27 June 2007 PD07 Kobe 13

Application of Geiger Mode Avalanche Photodiodes to PET: motivations and goals

• Why applying these photodetectors to PET?– Compact – Not sensitive to magnetic field

(Combination with MRI)– Coupling with cristal (1x1

mm2): high space resolution.

• The calorimeter is just a big PET machine:

– A calorimeter measures the energy deposited.

– 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)

27 June 2007 PD07 Kobe 14

Energy and time resolution in PET

The scattered coincidences can be cut with a good energy resolution: only the photoelectric peak is allowed.

Good PDE in the blue region.

photNE

E 1

The timing resolution of the module restricts the analysis area.500 ps (FWHM) -> 7.5 cm (FWHM)

27 June 2007 PD07 Kobe 15

Application of MPPC in PET: setup

2 LSO Crystals (Hilger Crystals, emission peak at 420 nm, 40 ns decay time) of 1mm x 1mm x 15mm (3mm x3mmx15mm)

2 LFS crystals (Lebedev institute, Moscow, new crystal, with few specifications) of 3mm x3mmx15mm

Read out by 1x1 mm (3x3 mm) Hamamatu MPPC, coupled 1:1 with the photodetector.

No amplification needed !!!

Timing with 4 GHz Oscilloscope (50 ps resolution)

Reproducibility of the measurement : 5%(Coupling is the main systematic problem)

QDC

&

27 June 2007 PD07 Kobe 16

Application of MPPC in PET: energy resolution (LSO)

1mmx1mm LSO crystal

Coupled with a 1mmx1mm

MPPC

3mmx3mm LSO crystal

Coupled with a 3mmx3mm

MPPC

Resolution (FWHM) ~ 14 %~300 p.e.

Resolution(FWHM) ~ 10 %~500 p.e.

The typical value of the single LSO crystal energy resolution (at 511 KeV)measured with the traditional photomultiplier tube is 10 %.

27 June 2007 PD07 Kobe 17

Energy resolution: LSO and LFS

3mmx3mm LSO crystal

Coupled with a 3mmx3mm

MPPC

3mmx3mm LFS crystal

Coupled with a 3mmx3mm

MPPC Resolution(FWHM) ~ 11 %

Resolution(FWHM) ~ 10 %

Spectra acquired at the same voltage. The difference of the resolution is inside the reproducibility of the measurement. The crystals look equivalent.

27 June 2007 PD07 Kobe 18

Timing resolution in PET

pe

cut

N

N

3mmx3mm LSO crystal Coupled with a 3mmx3mmMPPC

1 2

1 : Define a coincidence threshold2 : Define a timing threshold N_cut Dt = t(s1>N_cut) – t(s2>N_cut)

sigma150 ps expected from the formula.

150-200 ps typical with PM tube(Bill Moses, LBL)

A background is superimposed and ruins the time resolution...

Mean1: 4.42 ± 0.02Sigma1: 0.171 ± 0.020

Mean2: 4.39 ± 0.01Sigma2: 0.639± 0.015

27 June 2007 PD07 Kobe 19

Application of MPPC in PET:timing resolution (1x1)

SignalBackground

Compton Photoelectric

Coincidence At ~10 p.e.

Coincidence At ~30 p.e.

Coincidence At ~ 50 p.e.

1mmx1mm LSO crystal Coupled with a 1mmx1mmMPPC

1mmx1mm LSO crystal Coupled with a 1mmx1mmMPPC

1mmx1mm LSO crystal Coupled with a 1mmx1mmMPPC

Mean1: 4.42 ± 0.02Sigma1: 0.295 ± 0.020

Mean2: 4.39 ± 0.01Sigma2: 0.570± 0.050

Mean1: 5.36 ± 0.01Sigma1: 0.276 ± 0.005

Mean2: 4.9 ± 10.3Sigma2: 0.570± 0.050

Mean1: 5.39 ± 0.02Sigma1: 0.286 ± 0.020

27 June 2007 PD07 Kobe 20

MPPC in PET : discussion

• MPPC show for the first time a very promising possibility of

application of Geiger Mode avalnche photodiodes to Positron Emission Tomography:– Energy resolution 10% with LSO DONE!!!!– Time resolution (500 ps FWHM) ALMOST THERE!!!!

• More studies needed:– Study in magnetic field, combined with Magnetic Resonance.– What crystal ? WORK IN PROGRESS (LSO, LSF, YAP...) – Study spatial resolution of a matrix– Buid a prototype and verify the concept

27 June 2007 PD07 Kobe 21

Outlook ...

A big effort is running , all over the world, in order to steer the production of the Geiger Mode avalanche photodiodes:

• Blue sensitivity• Good dynamic range• Low noiseThis is not more a dream...

The Particle Physics and the Medical Physics communities are profiting of a continous interchange...