SiPM’s: from analog to digital, from laboratory to applicationmuon.npl.washington.edu/exp/NewG2/private/CaloDesign/DigitalSiPM... · 2011/6/9 · YH ©Philips Digital Photon Counting,

Philips Digital Photon Counting(PDPC)Dr. York HämischSenior DirectorPhilips Corporate Technologies

SiPM’s: from analog to digital, from laboratory to application

YH ©Philips Digital Photon Counting, February 2011

Philips Digital Photon Counting

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Digital Silicon Photomultipliers (dSiPM) -The next solid state (digital) revolution?

Transistor Television

X-Ray imaging

Digital Camera

Digital Photon Counting



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Koninklijke Philips Electronics B.V.

PHILIPS

Healthcare Lighting Corporate TechnologiesLifestyle

FY 2009 2010

Employees 115,924 ~ 119,000

Sales 23,189 ~ 25,419 Mio. €

Profit 424 Mio ~ 1.452 Mio. €



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Philips Digital Photon Counting (PDPC)

Philips Corporate Technologies

PDPC

Research IncubatorsIP&S

Healthcare Lifestyle Technology

Ventures

Dr. Thomas FrachDr. Carsten Degenhardttotal: 13 employees (June 9th, 2011)



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PDPC: short history

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



Initial Motivation: A better detector for Positron-Emission-Tomography (PET) with TOF and DOI

Graphics courtesy of Spanoudaki & Levin, Stanford,in: Phys. Med. Biol. (56) 2011

TOF – time-of-flight

DOI – depth ofinteraction



PMT is the gold standard so far

• bulky• fragile• high voltage• limited timing• analoge• needs amplifiers etc• expensive ! (some).

Source: www.hamamatsu.com



(Not only) for scintillators a fast reacting light detector was (is) desired

Graphs courtesy of Spanoudaki & Levin, Stanford, in Sensors, 10, 2010



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From single APD to multiple SPAD’s:Single Geiger-mode APD

Geiger-mode APD Array (SPAD’s):“Silicon Photomultiplier”

B. Dolgoshein, V. Saveliev, V. GolovineFirst idea: Russia, early 80‘s

• fully analog• poor timing• high bias voltage, butbelow breakdown

• single photon resolution• binary, but still analog• better timing• low bias voltage, above breakdown



(S)APD in Geiger-ModeEx

t. Vo

ltage

Cur

rent

Time

VBD

Meta-stable

Breakdown

Quenching



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Signal formation in (analog) SiPM’s

Graphics courtesy of Spanoudaki & Levin, Stanfordin: Sensors, 10, 2010



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SiPM-SPAD’s: sensitivity vs. dynamic range

Photographs courtesy of Spanoudaki & Levin, StanfordSensors, 10, 2010

Energy Resolution

• Energy resolution• 400 cells: ~12 % (70.0 V, RT, non-linear)• 1600 cells: ~21 % (70.5 V, RT, linear)

Typical 18F energy spectra with LYSO 1 x 1 x 20 mm³ Hamamatsu MPPC 400 cells/mm² Hamamatsu MPPC 1600 cells/mm²

Sebastian Fürst, “Development and Evaluation of Novel Detectors for Combined PET/MR Imaging,Basedon SiPMs and Fast Scintillation Crystals”, Diplomarbeit, Klinikumrechts der Isar, 2009

• 400 cell measurement shows saturation effect• extreme aspect ratio

YH comment:

Coincidence Time Resolution

Hamamatsu MPPC S10362-11-050C, 400 cells

Katja Zechmeister, “Evaluierung neuer Detektoren für die kombinierte PET/MR-Bildgebung, basierend auf SiPM und schnellen Szintillationskristallen”, Diplomarbeit, Klinikum rechts der Isar, 2010

• 2 MPPCs coupled to 1 x 1 x 20 mm³ LYSO• Measured with 18F

Data pointGaussian fit

Coincidence FWHM:913 ± 11 psFWHM for single MPPC:646 ± 8ps

Cou

nts

x 102 ps

Temperature Dependency

• Homogeneous illumination with blue pulsed LED • Temperature coefficient:

• 400 cells: ~0.05 %/K @ 25 °C• 1600 cells: ~0.05 %/K @ 25 °C

Breakdown VoltageHamamatsu MPPC 400 cells/mm² Hamamatsu MPPC 1600 cells/mm²

Sebastian Fürst, “Development and Evaluation of Novel Detectors for Combined PET/MR Imaging,Basedon SiPMs and Fast Scintillation Crystals”, Diplomarbeit, Klinikumrechts der Isar, 2009

Bias Voltage Dependency

• 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

Pulse HeightHamamatsu MPPC 400 cells/mm² Hamamatsu MPPC 1600 cells/mm²

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

• 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

Pulse HeightBias voltage adjusted, 400 cells Bias voltage not adjusted, 400 cells

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

• correction requires sophisticated ASIC• correction is time critical• adjusting bias changes PDE non-linearity

YH comments:



PDPC dSiPM: Temperature dependency

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

0.33%/KWithout bias correction !

Molecular ImagingProgram at Stanford

Measurements: energy resolution and linearitydetector energy resolution

0 100 200 300 400 500 600 7000.0

0.5

1.0

1.5

2.0

puls

e he

ight

(V)

photon energy (keV)

71.1 V 71.3 V 71.5 V 71.7 V 71.9 V 72.1 V 72.3 V 72.5 V

detector response

57Co

133Ba

22Na137Cs

71.0 71.2 71.4 71.6 71.8 72.0 72.2 72.44

6

810

12

14

16

1820

22

24

ener

gy re

solu

tion

at 5

11 k

eV (%

FW

HM

)

SiPM bias (V)

polished rough

non‐linear detector response

Non-linearity caused by- saturation, recovery effects- multiple “firing” of single SPAD’s

YH comments:



PDPC dSiPM: linearity only affected by saturation simple correction possible

( )NkNp −⋅−= 1lnN: active cells (6400)k: triggered cellsp: # of photons

• Experiments taken at room temperature

• No temperature stabilization

Measurements: time resolution (I)

Molecular ImagingProgram at Stanford

71.0 71.2 71.4 71.6 71.8 72.00.2

0.4

0.60.2

0.4

0.60.2

0.4

0.6

5 mm, polished 5 mm, roughtim

e re

solu

tion

(FW

HM

, ns)

SiPM bias voltage (V)

10 mm, polished 10 mm, rough

20 mm, polished 20 mm, rough

Effect of crystal surface treatment dependent on crystal thickness

500‐350 ps

400‐250 ps



PDPC dSiPM: Coincidence timing resolution

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Digital Photon Counting: the concept

Intrinsically, the SiPM is adigital device:

A single cell (SPAD) breaks down or not.

It works like a switch:no breakdown: „0“ – no photonbreakdown: „1“ – single photon

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)



Digital Photon Counting: realization

analog SiPM

www.hamamatsu.com

Summing all cell outputs leads to an analog output signal and limited performance

TDC andphoton counter

Digital output of• Number of photons• Time-stamp

Digital Cells

digital SiPM (dSiPM)

Integrated readout electronics is the key element to superior detector performance



Analog vs. Digital SiPM

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Digital SiPM: Principle



Digital SiPM: architecture and pixel diagram

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Single pixel

Die (2 x 2pixel)

(smart) tile (8x8 pixel)



PDPC Digital SiPM: architecture of one die (die = 2x2 pixels)



Digital SiPM array (tile 2.0)advanced integration

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FPGA/Flash:

• tile firmware• data collection/concentration• Skew correction• Saturation correction• configuration• temperature measurement • dark count maps

200 MHz ref. clock

Power (1.2V, 1.8V, 2.5V, 3.3V, 30V)

SPI interface

Serial Dataoutput (x2)



Digital SiPM: Typical acquisition sequence (example)



PDPC dSiPM: intrinsic timing resolution

PDPC array

USB

Coincidencedetection

PDPC array

Clock,Config,Data

Clock,Config,

Data

PCFPGA board FPGA board

electronic trigger

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psec-laser

Timing jitter: 44 ps FWHM 59 ps FWHM



PDPC: scintillator coincidence setup

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Recently achieved120 ps FWHMusing LSO:Ca

(Schaart et.al., TU Delft,submitted to IEEE-MIC)



PDPC dSiPM: Spectral sensitivity

Effective PDE:

LYSO(Ce) 25.9%CsI(Na) 23.7%CsI(Tl) 20.5%NaI(Tl) 24.2%BGO 24.2%LaBr3(Ce) 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



PDPC dSiPM: Scintillator readout (1:1 coupling)Ideal Floodmap

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• LYSO array, 8 x 8 crystals, 4 mm x 4 mm pitch, 22 mm length



PDPC dSiPM: Small crystal readout

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LYSO array, 30 x 30 crystals, 1 mm x 1 mm pitch, 10 mm length

Data analysis by P. Düppenbecker, Philips Research

Log scale



PDPC dSiPM: Small crystal identification limits

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PDPC dSiPM: Dark count mapWorst 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



PDPC dSiPM: slow scan imaging mode



PDPC dSiPM: crosstalk reduction by trenches



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Comparison of light detectors – which one is going to win?

Table courtesy of Spanoudaki & Levin, Stanfordin: Sensors, 10, 2010

PDPCdSiPM

meaninglessfirst photon

25-75< 350.33No

mm²-m²Currently: ~25



A digital light sensor might beuseful beyond PET

?

?

ClinicalPET

imaging

Pre-clinical

PET&SPECT

PET/MR

ClinicalSPECTimaging

SpectralCT

Low doseCT

Analytical Instrumentation

High Energy Physics

Night Vision / Surveillance / Security

DNA Sequencing

Microscopy

Microarrays

AntineutrinoDetection

Particle Accelerators

Automotive Night Vision LIDAR

Facility/Homeland

Security

Cherenkov Detectors

?

LoC

Intra-operativeprobes



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Digital SiPM – Čerenkov Light Detection

• 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

beam



4646

Setup at CERN SPS Test Beam

• Protons at 120GeV, intensity ~5000/sec • Sensor temperature 2 – 3°C• 2% diodes disabled • First photon trigger, all events validated

CRT σ = 85.9ps



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Key parameters of light detectors

λ

sens.

res.

speed

timingdyn. range

size

priceKey parameters:

1. Wavelength2. Sensitivity3. Spatial resolution4. Speed5. Timing6. Dynamic range7. Size8. Price



4848

What does the ideal spider web for HEP look like?

Key parameters:

1. Wavelength2. Sensitivity3. Spatial resolution4. Speed5. Timing6. Dynamic range7. Size8. Price

λ

sens.

res.

speed

timingdyn. range

size

price



Video showing glass PMT burning into flames and PDPC sensor evolving



www.philips.com/digitalphotoncounting

[email protected]

SiPM’s: from analog to digital, from laboratory to applicationDigital Silicon Photomultipliers (dSiPM) -�The next solid state (digital) revolution?Koninklijke Philips Electronics B.V.Philips Digital Photon Counting (PDPC)PDPC: short historyInitial Motivation: A better detector for Positron- Emission-Tomography (PET) with TOF and DOIPMT is the gold standard so far(Not only) for scintillators a fast reacting light detector was (is) desiredFrom single APD to multiple SPAD’s:(S)APD in Geiger-ModeSignal formation in (analog) SiPM’sSiPM-SPAD’s: sensitivity vs. dynamic rangeFoliennummer 13Foliennummer 14Foliennummer 15Foliennummer 16Foliennummer 17PDPC dSiPM: Temperature dependencyFoliennummer 19PDPC dSiPM: linearity only affected by saturation simple correction possibleFoliennummer 21PDPC dSiPM: Coincidence timing resolutionDigital Photon Counting: the conceptDigital Photon Counting: realizationAnalog vs. Digital SiPMDigital SiPM: PrincipleDigital SiPM: Principle Digital SiPM: PrincipleDigital SiPM: PrincipleDigital SiPM: architecture and pixel diagramPDPC Digital SiPM: architecture of one die � (die = 2x2 pixels)Digital SiPM array (tile 2.0)�advanced integration�Digital SiPM: Typical acquisition sequence (example)PDPC dSiPM: intrinsic timing resolutionPDPC: scintillator coincidence setupPDPC dSiPM: Spectral sensitivityPDPC dSiPM: Scintillator readout (1:1 coupling)�Ideal FloodmapPDPC dSiPM: Small crystal readoutPDPC dSiPM: Small crystal identification limitsPDPC dSiPM: Dark count mapPDPC dSiPM: slow scan imaging modePDPC dSiPM: crosstalk reduction by trenchesComparison of light detectors – which one is going to win?A digital light sensor might be�useful beyond PETDigital SiPM – Čerenkov Light DetectionSetup at CERN SPS Test BeamKey parameters of light detectorsWhat does the ideal spider web for HEP look like?Foliennummer 49Foliennummer 50

Documents

SiPM’s: from analog to digital, from laboratory to applicationmuon.npl.washington.edu/exp/NewG2/private/CaloDesign/DigitalSiPM... · 2011/6/9 · YH ©Philips Digital Photon Counting,