Transcript Application of new photo-detectors to calorimetry and

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 ?
•
•
•
•
•
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
27 June 2007
PD07 Kobe
Devices from MEPHI,
Hamamatsu and SensL
currently avalaible in DESY:
Good possibility of comparison
and testing
2
ILC Physics: challenges in calorimetry
•
•
•
ILC physics places premium on jet measurements and flavoure tagging, in an environment where event
reconstruction is possible
e e  WW
– tth  8 jets
– hZ  2l + 2 jets, 4 jets
– hhZ  2l + 4 jets, 6jets
Aim to fully reconstruct final state
•
•
Electron-positron
accelerator
Energy: 500 GeV up
to 1 TeV
, e e  ZZ
+ SUSY, quark, τ tagging,
lepton/hadron id
Missing energy signatures of SUSY and
extra-dimensions
This requires a calorimeter which is:
COMPACT – Inside the magnetic coil
HIGH GRANULAR – Imaging calorimeter
HERMETIC
27 June 2007
PD07 Kobe
60% E
30% E
3
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
27 June 2007
HCAL
PD07 Kobe
ECAL
TPC
4
SiPM: a good photodetector for hadron calorimetry
Test Beam CERN. 10 GeV Pion in the HCAL
The minimum signal in 1 cell is a m.i.p.
The good SiPM for this application:
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.
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 production
4. Compactness, unsensitivity to magnetic
Test
field up to 5 T, radiation hardness ...
27 June 2007
PD07 Kobe
Beam data are under analysis
5
New approach to the calorimeter design:
the direct readout of the scintillator
Present status
• 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
27 June 2007
R&D
The direct readout is easier to extend to
a large scale production.
What is the solution which respects the required bounds
on the parameters:
1. Blue Sensitive?
2. Green sensitive and large?
PD07 Kobe
6
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
7
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
8
Direct readout with MPPC : Most Probable
Value of the mip response spectrum
1600 px
400 px
Direct (Blue dots) and
Wavelength shifter mediated
readout (Green dots) .
27 June 2007
Light Yield in the calorimeter prototype
PD07 Kobe
9
Direct readout with MPPC:
mip collection efficiency
1600 px
Cut at 3 KHz
400 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
10
3x3 MPPC: direct readout
Ru106 response
LED Light
•
•
About 50 p.e. Per MPV
Good single photoelectron resolution!
27 June 2007
PD07 Kobe
11
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
12
Application of Geiger Mode Avalanche
Photodiodes to PET: motivations and goals
27 June 2007
•
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)
PD07 Kobe
13
Energy and time resolution in PET
The scattered coincidences can
be cut with a good energy
resolution: only the photoelectric
peak is allowed.
E

E
1
N phot
Good PDE in the blue region.
The timing resolution of the
module restricts the analysis area.
500 ps (FWHM) -> 7.5 cm (FWHM)
27 June 2007
PD07 Kobe
14
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 !!!
&
QDC
Timing with 4 GHz Oscilloscope (50 ps
resolution)
Reproducibility of the measurement : 5%
(Coupling is the main systematic problem)
27 June 2007
PD07 Kobe
15
Application of MPPC in PET:
energy resolution (LSO)
1mmx1mm LSO
crystal
Coupled with a
1mmx1mm
MPPC
Resolution
(FWHM) ~ 14 %
~300 p.e.
3mmx3mm LSO
crystal
Coupled with a
3mmx3mm
MPPC
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
16
Energy resolution: LSO and LFS
3mmx3mm LFS
crystal
Coupled with a
3mmx3mm
MPPC
3mmx3mm LSO
crystal
Coupled with a
3mmx3mm
MPPC
Resolution
(FWHM) ~ 10 %
Resolution
(FWHM) ~ 11 %
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
17
Timing resolution in PET
1

N cut 
N pe
3mmx3mm LSO
crystal
Coupled with a
3mmx3mm
MPPC
2
Mean1: 4.42 ± 0.02
Sigma1: 0.171 ±
0.020
Mean2: 4.39 ± 0.01
Sigma2: 0.639±
0.015
1 : Define a coincidence threshold
2 : 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...
27 June 2007
PD07 Kobe
18
Application of MPPC in PET:timing resolution (1x1)
Coincidence
At ~10 p.e.
1mmx1mm LSO
crystal
Coupled with a
1mmx1mm
MPPC
Coincidence
At ~ 50 p.e.
Mean1: 4.42 ± 0.02
Sigma1: 0.295 ±
0.020
Coincidence
At ~30 p.e.
Mean2: 4.39 ± 0.01
Sigma2: 0.570±
0.050
Mean1: 5.39 ± 0.02
Sigma1: 0.286 ±
0.020
1mmx1mm LSO
crystal
Coupled with a
1mmx1mm
MPPC
Background
Mean1: 5.36 ± 0.01
Sigma1: 0.276 ±
0.005
Mean2: 4.9 ± 10.3
Sigma2: 0.570±
0.050
Signal
1mmx1mm LSO
crystal
Coupled with a
1mmx1mm
MPPC
Compton
27 June 2007
PD07 Kobe
Photoelectric
19
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
20
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 noise
This is not more a dream...
The Particle Physics and the Medical
Physics communities are profiting
of a continous interchange...
27 June 2007
PD07 Kobe
21