application of new photo-detectors to calorimetry and medical physics
DESCRIPTION
Application of new photo-detectors to calorimetry and medical physics. Nicola D’Ascenzo, Erika Garutti University of Hamburg – DESY Alexander Tadday University of Heidelberg. The Geiger Mode Avalanche Photodiode. Why is this detector so interesting ?. - PowerPoint PPT PresentationTRANSCRIPT
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...