SiPM’s: from analog to digital, from
laboratory to application
Philips Digital Photon Counting
(PDPC)
Dr. York Hämisch
Senior Director
Philips Corporate Technologies
Philips Digital Photon Counting
Digital Silicon Photomultipliers (dSiPM) The next solid state (digital) revolution?
Transistor
X-Ray imaging
YH
Television
Digital Camera
Digital Photon Counting
©Philips Digital Photon Counting, February 2011
2
Philips Digital Photon Counting
Koninklijke Philips Electronics B.V.
PHILIPS
Healthcare
FY
Lighting
2009
Lifestyle
2010
Employees 115,924
~ 119,000
Sales
23,189
~ 25,419 Mio. €
Profit
424 Mio
~ 1.452 Mio. €
YH
Corporate
Technologies
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
Philips Digital Photon Counting (PDPC)
Philips Corporate Technologies
Research
PDPC
IP&S
Healthcare
Incubators
Lifestyle
Dr. Thomas Frach
Dr. Carsten Degenhardt
total: 13 employees (June 9th, 2011)
YH
©Philips Digital Photon Counting, February 2011
Technology
Ventures
4
Philips Digital Photon Counting
PDPC: short history
YH
2004
Research project: “Novel technologies for future PET
systems”
2005
Dr.Thomas Frach invented the digital SiPM
2006
Research project: “Integrated digital light sensor”; first test
chip with promising results (inkubator)
2006
Disentanglement of Philips Semiconductors – now NXP
2007
Start of the PDPC venture
2008
Proof of concept
2009
Technology launch at IEEE NSS-MIC sensor V1.0
2010
PDPC separate unit of Philips Corporate Technologies
2011
Introduction of PDPC-TEK (Technology Evaluation Kit)
and sensor version 2.0
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Philips Digital Photon Counting
Initial Motivation: A better detector for PositronEmission-Tomography (PET) with TOF and DOI
TOF – time-of-flight
DOI – depth of
interaction
Graphics courtesy of Spanoudaki & Levin, Stanford,
in: Phys. Med. Biol. (56) 2011
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
PMT is the gold standard so far
Source: www.hamamatsu.com
• bulky
• fragile
• high voltage
• limited timing
• analoge
• needs amplifiers etc
• expensive ! (some).
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
(Not only) for scintillators a fast reacting light
detector was (is) desired
Graphs courtesy of Spanoudaki & Levin, Stanford, in Sensors, 10, 2010
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
From single APD to multiple SPAD’s:
Single Geiger-mode APD
• fully analog
• poor timing
• high bias voltage, but
below breakdown
B. Dolgoshein, V. Saveliev, V. Golovine
First idea: Russia, early 80‘s
Geiger-mode APD Array (SPAD’s):
“Silicon Photomultiplier”
• single photon resolution
• binary, but still analog
• better timing
• low bias voltage, above breakdown
YH
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Philips Digital Photon Counting
Ext. Voltage
(S)APD in Geiger-Mode
VBD
Breakdown
Current
Meta-stable
YH
Quenching
Time
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Signal formation in (analog) SiPM’s
Graphics courtesy of Spanoudaki & Levin, Stanford
in: Sensors, 10, 2010
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
SiPM-SPAD’s: sensitivity vs. dynamic range
Photographs courtesy of Spanoudaki & Levin, Stanford
Sensors, 10, 2010
YH
©Philips Digital Photon Counting, February 2011
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YH comment:
Energy Resolution
• 400 cell measurement shows saturation effect
• extreme aspect ratio
Typical 18F energy spectra with LYSO 1 x 1 x 20 mm³
Hamamatsu MPPC 400 cells/mm²
Hamamatsu MPPC 1600 cells/mm²
• Energy resolution
• 400 cells: ~12 % (70.0 V, RT, non-linear)
• 1600 cells: ~21 % (70.5 V, RT, linear)
Sebastian Fürst, “Development and
Evaluation of Novel Detectors for
Combined PET/MR Imaging,Based
on SiPMs and Fast Scintillation
Crystals”, Diplomarbeit, Klinikum
rechts der Isar, 2009
Coincidence Time Resolution
Hamamatsu MPPC S10362-11-050C, 400 cells
Data point
Gaussian fit
Coincidence FWHM:
Counts
913 ± 11 ps
FWHM for single MPPC:
646 ± 8ps
x 102 ps Katja Zechmeister, “Evaluierung
• 2 MPPCs coupled to 1 x 1 x 20 mm³ LYSO
• Measured with 18F
neuer Detektoren für die kombinierte
PET/MR-Bildgebung, basierend auf
SiPM und schnellen
Szintillationskristallen”, Diplomarbeit,
Klinikum rechts der Isar, 2010
Temperature Dependency
Breakdown Voltage
Hamamatsu MPPC 400 cells/mm²
Hamamatsu MPPC 1600 cells/mm²
• Homogeneous illumination with blue pulsed LED
• Temperature coefficient:
• 400 cells: ~0.05 %/K @ 25 °C
• 1600 cells: ~0.05 %/K @ 25 °C
Sebastian Fürst, “Development and
Evaluation of Novel Detectors for
Combined PET/MR Imaging,Based
on SiPMs and Fast Scintillation
Crystals”, Diplomarbeit, Klinikum
rechts der Isar, 2009
Bias Voltage Dependency
Pulse Height
Hamamatsu MPPC 400 cells/mm²
Hamamatsu MPPC 1600 cells/mm²
• Illumination with blue pulsed LED
• Temperature was kept constant at 25°C in both series of measurements
• Bias voltage coefficient:
• 400 cells: 63 ± 2 %/V @ 69.83 V
Sebastian Fürst, “Development and Evaluation of Novel
Detectors for Combined PET/MR Imaging,Based on
SiPMs and Fast Scintillation Crystals”, Diplomarbeit,
Klinikum rechts der Isar, 2009
Temperature Dependency
Pulse Height
Bias voltage adjusted, 400 cells
YH comments:
• correction requires sophisticated ASIC
• correction is time critical
• adjusting bias changes PDE Æ non-linearity
Bias voltage not adjusted, 400 cells
• Temperature coefficients, illuminated with blue pulsed LED
• 400 cells
• 0.0 ± 0.2 %/K and -2.7 ± 0.2 %/K @ 25 °C
• 1600 cells
• 0.2 ± 0,6 %/K and -2.5 ± 0.4 %/K @ 25 °C Sebastian Fürst, “Development and Evaluation of Novel
Detectors for Combined PET/MR Imaging,Based on
SiPMs and Fast Scintillation Crystals”, Diplomarbeit,
Klinikum rechts der Isar, 2009
Philips Digital Photon Counting
PDPC dSiPM: Temperature dependency
0.33%/K
Without bias correction !
Picosecond Laser:
• 24 ps full-width at half-maximum timing resolution
• Photopeak changes 0.33% per degree C due to changing PDE
• Time changes 15.3 ps per degree C (TDC + trigger network drift)
• PDE drift can be easily compensated by adapting the bias voltage
• TDC offset can be periodically re-calibrated using the SYNC input
YH
©Philips Digital Photon Counting, February 2011
Measurements: energy resolution and linearity
detector energy resolution
detector response
22Na
137Cs
24
22
20
non‐linear detector response
18
16
14
12
10
8
71.1 V
71.3 V
71.5 V
71.7 V
71.9 V
72.1 V
72.3 V
72.5 V
2.0
polished
rough
1.5
pulse height (V)
energy resolution at 511 keV (% FWHM)
133Ba
57Co
1.0
0.5
6
4
71.0
71.2
71.4
71.6
71.8
SiPM bias (V)
72.0
72.2
72.4
0.0
0
100
200
300
400
500
600
700
photon energy (keV)
YH comments:
Non-linearity caused by
- saturation, recovery effects
- multiple “firing” of single SPAD’s
Molecular Imaging
Program at Stanford
Philips Digital Photon Counting
PDPC dSiPM: linearity only affected by
saturation Æ simple correction possible
(
p = − N ⋅ ln 1 − k
N
)
N: active cells (6400)
k: triggered cells
p: # of photons
• Experiments taken
at room
temperature
• No temperature
stabilization
YH
©Philips Digital Photon Counting, February 2011
Measurements: time resolution (I)
20 mm, polished
20 mm, rough
time resolution (FWHM, ns)
0.6
0.4
500‐350 ps
0.2
0.6
10 mm, polished
10 mm, rough
0.4
0.2
0.6
5 mm, polished
5 mm, rough
400‐250 ps
0.4
0.2
71.0
71.2
71.4
71.6
71.8
72.0
SiPM bias voltage (V)
Effect of crystal surface treatment dependent on crystal thickness
Molecular Imaging
Program at Stanford
Philips Digital Photon Counting
PDPC dSiPM: Coincidence timing resolution
YH
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Philips Digital Photon Counting
Digital Photon Counting: the concept
Therefore, while the APD is a linear amplifier for the input
optical signal with limited gain, the SPAD is a trigger
device so the gain concept is meaningless.
(source: Wikipedia)
Intrinsically, the SiPM is a
digital device:
A single cell (SPAD) breaks down or not.
It works like a switch:
no breakdown: „0“ – no photon
breakdown: „1“ – single photon
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital Photon Counting: realization
analog SiPM
digital SiPM (dSiPM)
TDC and
photon counter
Digital Cells
Digital output of
• Number of photons
• Time-stamp
www.hamamatsu.com
Summing all cell outputs leads
to an analog output signal and
limited performance
YH
Integrated readout electronics
is the key element to superior
detector performance
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Analog vs. Digital SiPM
YH
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Philips Digital Photon Counting
Digital SiPM: Principle
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital SiPM: Principle
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital SiPM: Principle
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital SiPM: Principle
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital SiPM: architecture and pixel diagram
Single pixel
Die (2 x 2pixel)
(smart) tile (8x8 pixel)
YH
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Philips Digital Photon Counting
PDPC Digital SiPM: architecture of one die
(die = 2x2 pixels)
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Digital SiPM array (tile 2.0)
advanced integration
Power
(1.2V, 1.8V, 2.5V,
3.3V, 30V)
200 MHz ref. clock
SPI interface
Serial Dataoutput (x2)
FPGA/Flash:
•
•
•
•
•
•
•
YH
tile firmware
data collection/concentration
Skew correction
Saturation correction
configuration
temperature measurement
dark count maps
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
Digital SiPM: Typical acquisition sequence
(example)
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
PDPC dSiPM: intrinsic timing resolution
electronic trigger
PDPC array
psec-laser
Clock,
Config,
Data
YH
Clock,
Config,
Data
Coincidence
detection
FPGA board
FPGA board
Timing jitter:
PDPC array
44 ps FWHM
©Philips Digital Photon Counting, February 2011
USB
PC
59 ps FWHM
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Philips Digital Photon Counting
PDPC: scintillator coincidence setup
Recently achieved
120 ps FWHM
using LSO:Ca
(Schaart et.al., TU Delft,
submitted to IEEE-MIC)
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
PDPC dSiPM: Spectral sensitivity
Effective PDE:
LYSO(Ce)
CsI(Na)
CsI(Tl)
NaI(Tl)
BGO
LaBr3(Ce)
25.9%
23.7%
20.5%
24.2%
24.2%
9.6%
• Peak PDE ~30% at 430 nm and 3.3 V excess voltage
• Conservative diode design (50 % fill-factor)
• No anti reflection coating used
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
PDPC dSiPM: Scintillator readout (1:1 coupling)
Ideal Floodmap
• LYSO array, 8 x 8 crystals, 4 mm x 4 mm pitch, 22 mm length
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
PDPC dSiPM: Small crystal readout
LYSO array, 30 x 30 crystals, 1 mm x 1 mm pitch, 10 mm length
Log scale
Data analysis by P. Düppenbecker, Philips Research
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
PDPC dSiPM: Small crystal identification limits
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
PDPC dSiPM: Dark count map
Worst cells
are switched
off
• Dark counts per second at 20°C and 3.3V excess voltage
• ~ 95% good diodes (dark count rate close to average)
• Typical dark count rate at 20°C and 3.3V excess voltage: ~150Hz / diode
• Dark count rate drops to ~1-2Hz per diode at -40°C
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
PDPC dSiPM: slow scan imaging mode
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
PDPC dSiPM: crosstalk reduction by trenches
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
Comparison of light detectors – which one is
going to win?
PDPC
dSiPM
meaningless
first photon
25-75
< 35
0.33
No
mm²-m²
Currently: ~25
Table courtesy of Spanoudaki & Levin, Stanford
in: Sensors, 10, 2010
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
A digital light sensor might be
useful beyond PET
Analytical Instrumentation
DNA
Sequencing
Microscopy
?
Microarrays
PET/MR
Clinical
PrePET
clinical
imaging
PET&SPECT
Intraoperative
probes
YH
LoC
High Energy Physics
Low dose
CT
Antineutrino
Detection
Cherenkov
Detectors
Particle
Accelerators
?
Night Vision / Surveillance / Security
Clinical
SPECT
imaging
Spectral
CT
©Philips Digital Photon Counting, February 2011
Automotive
Night Vision
Facility/
Homeland
Security
LIDAR
?
Philips Digital Photon Counting
Digital SiPM – Čerenkov Light Detection
beam
• PMMA radiator coupled via air gap to two PDPC dSiPM’s in coincidence
• Box isolated and temperature-controlled with a TEC to 2 – 3°C
• External beam gate signal to minimize randoms due to low beam duty-cycle
• Cooperation between University Giessen (Prof. Düren) and Philips DPC
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
Setup at CERN SPS Test Beam
• Protons at 120GeV, intensity ~5000/sec
• Sensor temperature 2 – 3°C
• 2% diodes disabled
CRT σ = 85.9ps
• First photon trigger, all events validated
YH
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
Key parameters of light detectors
λ
price
sens.
size
dyn. range
YH
res.
speed
Key parameters:
1.
2.
3.
4.
5.
6.
7.
8.
Wavelength
Sensitivity
Spatial resolution
Speed
Timing
Dynamic range
Size
Price
timing
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
What does the ideal spider web for HEP look
like?
λ
Key parameters:
price
sens.
size
dyn. range
YH
res.
speed
1.
2.
3.
4.
5.
6.
7.
8.
Wavelength
Sensitivity
Spatial resolution
Speed
Timing
Dynamic range
Size
Price
timing
©Philips Digital Photon Counting, February 2011
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Philips Digital Photon Counting
Video showing glass PMT burning into flames and PDPC sensor evolving
YH
©Philips Digital Photon Counting, February 2011
Philips Digital Photon Counting
york.haemisch@philips.com
www.philips.com/digitalphotoncounting
YH
©Philips Digital Photon Counting, February 2011