close

Вход

Забыли?

вход по аккаунту

?

The Geiger-APD a novel photon detector and its application in

код для вставкиСкачать
The Geiger-APD
a novel photon detector and its
application in
astrophysics experiments
and
positron emission tomography
A. Nepomuk Otte
MPI für Physik, Munich / Humboldt Universität, Berlin
Outline
• why new photon detectors for experiments
in astroparticle physics
• the G-APD and some of its characteristics
• application of G-APD in:
– positron emission tomography (PET)
– air Cherenkov telescopes
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
2
Many future experiments will use
>> 100,000 photon detectors
Requirements to be fulfilled by the photon detector candidate:
• robust and stable
• easy to calibrate
• blue sensitive
• low cost (+ low peripheral costs)
• compact
• low power consumption
•…
• highest possible photon detection efficiency
Astroparticle experiments that will use this photon detector
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
3
Cosmic Ray Physics from Space
30°

400 km

Atmospheric
Sounding

EECR
Atmosphere
Fluorescence
Čerenkov
230 km
Earth
M .C .M .
‘0 2
• Highest energy cosmic rays > 1020 eV
• GZK mechanism
• sources of CR
•…
http://www.euso-mission.org/
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
4
Ground based Gamma Ray Astrophysics
Gamma Ray induces electromagnetic cascade
relativistic particle shower in atmosphere
Cherenkov light
fast light flash (nanoseconds)
100 photons per m² (1 TeV Gamma Ray)
MAGIC: world largest
air Cherenkov telescope
http://wwwmagic.mppmu.mpg.de/
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
5
VHE gamma-ray sources: status ICRC 2007
71 known sources
factor of 6 increase
within 4 years
very successful
above 100GeV
Rowell
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
6
pushing to lower energies
entering an unexplored energy window between 10 GeV and 100 GeV
• extragalactic background light studies
• gamma ray bursts
• dark matter
• tests of quantum gravity
• pulsars
•…
requires:
• larger light collectors
• high efficiency photon detectors
currently used: classical photomultiplier tubes with ~20% QE
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
7
The G-APD
a promising photon detector concept invented in Russia in the 80’s
advantages
• sensors with ~60% efficiency become available
• internal gain ~105 -106
• compact and robust
• …
disadvantages
• small sizes (<5x5mm²)
• optical crosstalk (10%)
• high dark count rate (~MHz)
•…
P. Buzhan et al.
http://www.slac-stanford.edu/pubs/icfa/fall01.html
Otte et al., IEEE TNS. 53 (2006) 636.
SNIC-2006-0018, Apr 2006
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
8
3x3 mm² G-APD
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
9
A look into basic operations
of
semiconductor photon detectors
with
internal amplification
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
10
Working modes of avalanche photodiodes
Linear/Proportional Mode
•
•
Bias: slightly BELOW breakdown
Geiger Mode
•
breakdown voltage
Linear-mode: it’s an AMPLIFIER
•
Gain: limited < 300 (1000)
•
High temperature/bias dependence
•
No single photo electron resolution
A. Nepomuk Otte
Bias: (10%-20%) ABOVE
•
Geiger-mode: it’s a BINARY
device!!
•
Count rate limited
•
Gain: “infinite” !!
Max-Planck-Institut für Physik / Humboldt Universität Berlin
11
Advantages of APDs in Geiger Mode
or
Single Photon Avalanche Diodes (SPADs)
• Large standardized output signal
high immunity against pickup
• High sensitivity for single photons
• Excellent timing even for single photo electrons (<<1ns)
• Good temperature stability
• Low sensitivity to bias voltage drifts
• Devices operate in general < 100 V
• Complete insensitive to magnetic fields
• No nuclear counter effect (due to standardized output)
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
12
The principal disadvantage for many applications:
It is a binary device
One knows: There was at least one electron/hole initiating the breakdown
but not
how many of them
solved in the G-APD concept
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
13
Basic unit in a G-APD is a Single Photon Avalanche Diode (SPAD)
Si* Resistor
+
n
p-
Vbias
p+
Al-conductor
SiO2
Guardring n-
Substrate p+
from B. Dolgoshein (ICFA 2001)
http://www.slac.stanford.edu/pubs/icfa/
A. Nepomuk Otte
Breakdown in SPAD is quenched by
individual polysilicon resistor
(passive quenching)
Max-Planck-Institut für Physik / Humboldt Universität Berlin
14
The G-APD
typically 100…2000 small SPADs / mm²
1mm
Bias and
Output
All SPADs connected in parallel
Only one common signal line
SPAD
30µm
quenching resistor
small signal replacement circuit
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
15
SiPM output is the analog sum of all SPADs
Well defined output signal per SPAD  multi pixel resolution
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
16
Dynamic Range
working condition:
Number of photo electrons < SPAD
cells
Number of pixels fired
Dynamic range naturally limited by
number of available SPADs
1000
100
576
1024
4096
10
1
1
From probability considerations:
N firedcells
A. Nepomuk Otte
N
PDE


 photon
 N available  1  e Navailable 




10
100
1000
10000
Number of photoelectrons
from B. Dolgoshein Light06
 20% deviation from linearity if
50% of cells respond
Max-Planck-Institut für Physik / Humboldt Universität Berlin
17
Photon Detection Efficiency (PDE)
or
Effective Quantum Efficiency
Most important parameter of a photon detector!!
limiting factors:
• Intrinsic quantum efficiency
• Fraction of sensitive area (20% - 80%)
• Surface reflection losses
• Probability for Geiger breakdown
(depends on electric field)
• SPAD recovery time (passive quenching)
• Active volume / absorption length
W.Oldham, P.Samuelson, P.Antognetti, IEEE Trans. ED (1972)
In total: Currently claimed best PDE values are ~60%
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
18
Measurement of the Photon Detection
Efficiency
PDE measurements are not an easy task
– optical crosstalk
– dependency on bias voltage
often a photomultiplier with unknown photoelectron collection
efficiency is used as reference
 Overestimation of the PDE
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
19
A method to measure the PDE
use calibrated PiN-diode as reference
use integrating sphere with two exit ports (splitting ratio of several thousand)
flash PiN-diode and G-APD with pulsed monochromatic light source
Otte et al., NIM A 567 360–363, 2006
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
20
Problems:
Optical Crosstalk
High Dark Count Rate
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
21
Optical Crosstalk
• SPADs not only detect photons
they also emit photons during
breakdown
Emission microscopy picture of a prototype SiPM
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
22
Photons can trigger additional cells
Sketch from Cova et al. NIST 2003
Workshop on single photon detectors
 Optical crosstalk
Artificial increase in signal
 Excess Noise Factor of SiPM
can be quite significant
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
23
Using optical crosstalk to
learn more about the
photons emitted in
avalanches
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
24
Light Emission in Avalanches
• measured spectra do not show similar behavior
• emission mechanisms not well known
• very few absolute measurements
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
W. J. Kindt
25
optical crosstalk spectrum from dark noise
Try to reproduce this
distribution with Monte Carlo
simulations
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
26
SiSi: The SiPM Simulator
*Elisabeth
”Sisi” von Wittelsbach was
the empress consort of Emperor
Franz Joseph of Austria. She was born
1837 in Munich, Bavaria and
murdered
1898
in
Geneva,
Switzerland
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
27
SiSi
SiSi is an “almost” complete simulator of a SiPM
simulation of avalanche photons:
• black body radiation with
free parameters:
- temperature
- intensity
• isotropic emission
photoelectrons in non-depleted
bulk are subject to simple
diffusion model;
lifetime of electrons is a free
parameter
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
28
Example of a good match
residuals
Residuals can be explained by dark counts which are not simulated in SiSi
no unique set of model parameters (Temperature and Intensity of photon spectrum)
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
29
Characteristics of Photons that cause
Optical Crosstalk
Crosstalk is only caused by
photons within a narrow range of
energies
Peak: ~1.26eV
FWHM: ~0.2 eV
energy distribution of
photons causing
optical crosstalk
A. Nepomuk Otte
2 photon spectra that
reproduce the measured
crosstalk distributions
Intensity (1.15 … 1.40 eV):
~3*10-5 photons / electron
(systematic uncertainty of ~2)
Max-Planck-Institut für Physik / Humboldt Universität Berlin
30
Reason for narrow range of photon energies
strong dependence of absorption lengths on photon energy
not absorbed in G-APD
absorption in same cell
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
31
Two possible applications for G-APDs:
1. positron emission tomography (PET)
2. air Cherenkov telescopes
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
32
Positron Emission Tomography (PET)
Basic principle
PET : image distribution of a radio-labeled
tracer inside the body
γ
detectors
Tracer Molecules : Labeled by positron
emitting isotopes
( 11C, 13N, 15O, 18F)
γ
Object containing
some quantity of
radio-labeled tracer
Positron annihilation : two back-to-back
511 keV photons
(positron-source)
The emitted photons are detected by two
opposing detectors in coincidence
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
33
The Reconstruction Problem
This is...
what you are looking for!
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
34
G-APDs in PET: the first studies
Advantage: very compact, no sophisticated amplifier needed, …
• direct coupling of SiPM to
crystal
wrapped crystals
• no cooling
• Factor 4 area miss match
between SiPM and crystal
G-APDs
signal readout
Otte, et al. NIM A 545 (2005)
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
35
G-APDs in PET: the first studies
Advantage: very compact, no sophisticated amplifier needed, …
• direct coupling of SiPM to
crystal
first ever
measurement
• no cooling
• Factor 4 area miss match
between SiPM and crystal
• Energy resolution 22% FWHM
on 22Na coincidence spectrum
• Time resolution 1.5 nsec FWHM
Otte, et al. NIM A 545 (2005)
A. Nepomuk Otte
Things have quite improved since then
Max-Planck-Institut für Physik / Humboldt Universität Berlin
36
Result of measurements with MW-3 (3x3 mm2) Geiger- mode
APDs from Dubna (Z. Sadygov) + LYSO crystals (2x2x10 mm3)
22
Energy Resolution:
12% FWHM
3
Na + LSO (2x2x10 mm ; reflector = teflon)
2
MW-3 (3x3 mm , n.1): RT, U = 138.0V, I = 1.05A
2000
2000
Time Resolution:
540ps
Counts
1500
1000
1500
(limited by crystal)
500
0
150
1000
200
250
511 keV : A/A = 12.7% (FWHM)
1275 keV : A/A = 7.7%
A1275 / A511 = 2.60
500
MRS diode used
0
0
200
400
Amplitude (pC)
600
Alexey Stoykov,
Dieter Renker (PSI)
(2006)
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
37
Imaging Air Cherenkov
Technique
Cherenkov light image of particle shower
in telescope camera
Gamma
ray
Particle
shower
~ 10 km • fast light flash (nanoseconds)
• 100 photons per m² (1 TeV Gamma Ray)
~ 1o
~ 120 m
A. Nepomuk Otte
reconstruct:
arrival direction, energy
reject hadron background
Max-Planck-Institut für Physik / Humboldt Universität Berlin
38
Figure of Merit
Cherenkov spectrum folded with
photon detector response
Cherenkov spectrum on ground
A. Nepomuk Otte
photon detector response
Max-Planck-Institut für Physik / Humboldt Universität Berlin
39
Application of G-APDs in air Cherenkov telescopes
Figure of Merit
Cherenkov spectrum folded with
photondetector response
MPPC from Hamamatsu with highest PDE
(from data sheet MPPC
with 100x100 µm² cells)
photomultiplier tubes
can hope for
factor >2 increase in
sensitivity compared to
bialkali PMTs
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
40
Test on La Palma with MAGIC
MAGIC Pixel Size
4 MPPC-33-050C from Hamamatsu:
sensor size: 3x3mm²
single cell size: 50x50µm²
nominal bias: 70.4V
dark rate at nominal bias: ~2MHz
gain at nominal bias: 7.5*105
crosstalk at nominal bias: 10%
Array of 4 MPPCs:
light catchers with factor 4
concentration; 6x6mm² onto
3x3mm²
peak photon detection efficiency 55%
needs to be confirmed
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
41
array mounted next to the
MAGIC camera for 3 nights for
fine tuning and tests
G-APDs signals recorded by the
MAGIC DAQ with each trigger
• array not removed or
protected during day
• it was raining for one day!
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
42
Array mounted
onto the MAGIC
camera entrance
window for two
nights
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
43
Light recorded from Calibration Runs
Pedestal
1 phe
UV-LEDs 375nm
single phe-resolution
degraded because of
light from night sky
2 phe
3phe
…
easy calibration
 reduced systematics
some recorded showers 
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
44
location of MPPC array
1 phe
2 phe
4 phe
1 phe
MPPCs
70 phe
35 phe
35 phe
15 phe
PMTs
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
45
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
46
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
47
Shower Signals: MPPC vs PMT
event selection:
two PMTs next to MPPCs with
more than 15 photoelectrons
in each tube
counts
~300 events from ~30 min data
signals are correlated
on average MPPC record a
larger signal
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
48
ratio of signals
MPPC/ (scaled) PMT
event by event
100% efficiency
assumed for the light
catcher in front of the
MPPCs
 on average 1.6 times more light detected with MPPCs (crosstalk corrected)
in reality higher due to non perfect light concentrator
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
49
Summary
The silicon photomultiplier is a real breakthrough in
photon detection!!
High photon detection efficiency (>60%)
Offers high internal amplification (>105)
Fast timing (<nsec)
Low power consumption (1…100µW/mm²)
It can not be damaged by exposure to strong source of light
No aging
CMOS like technology  prospects for cheap mass production <10$ per mm²
…
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
50
Summary
In PET G-APDs already outperform other photon detectors
+ they allow to build very compact and robust scanners insensitive to
magnetic fields  combination of MRT and PET
PMTs in Cherenkov telescopes could be replaced by G-APDs
• at least 1.6 times more light recorded
• G-APD intrinsic noise is 10 times lower than the “noise” coming from
the night sky
• optical crosstalk is an issue for IACTs and should be reduced to below
5%
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
51
The End
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
52
Ongoing Development:
SiPM exploiting Backillumination
By the Semiconductor Laboratory
affiliated to the MPIs for Physics and Extraterrestrial Physics
photon
depleted bulk
path of the photo electron
avalanche regions
50µm … 450µm
Si
Blow up of one “cell”
output
predicted characteristics:
• PDE > 80%
• Single photo electron time jitter ~ nsec
• Cooling is mandatory
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
53
drift path of the photo electron
shallow p+
photon
n type depleted bulk
drift rings p+
50µm...450µm
deep n
avalanche region
quenching resistor
100µm
output line
• test structures of novel avalanche structure will be finished next month
• After successful evaluation  prototypes end 2007
Crosstalk problem can be a showstopper!!
will be evaluated by dedicated structures
small cell capacitance is of advantage
A. Nepomuk Otte
Max-Planck-Institut für Physik / Humboldt Universität Berlin
54
Документ
Категория
Презентации
Просмотров
14
Размер файла
11 986 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа