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Ralf Schulze <ralf.schulze@philips.com> Philips Digital Photon Counting
The PDPC Technology Evaluation KitYour Entry to Digital Photon Counting
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
The PDPC Technology Evaluation Kit
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PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Overview
• Technology overview– Photon detection with SiPMs– Digital vs. analog
• The Philips Digital Photon Counting (PDPC) sensor• The PDPC Technology Evaluation Kit (PDPC-TEK)
– Components – Features
• Sample applications
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Principle of Silicon Photomultipliers
● Operating diodes in reverse bias in Geiger-mode (above breakdown voltage)
● Single photon triggers breakdown of diode
● Diode breakdown can be detected and indicates photon hit
↪ Single photon detection
Voltage
Current
Time
VBD
Meta-stable
Breakdown
Quenching
VBiasV
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
SiPM Acquisition: The Analog Way
www.hamamatsu.com
● Photon detection current gives analog signal ● Number of detection photons determined by
peak-shape analysis
↪ Pulse shape analysis difficult, influenced by external parameters (magnetic field,
noise, temperature, etc.)
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
dSiPM Acquisition: The Digital Way
● Photon detection signal is digital by nature (photon or no photon)● Keep further processing fully digital by counting number of cells that broke
down with on-chip digital electronics (Adder circuitry, TDC, etc.) ● Chip output is digital number of photons with timestamp
↪ Fully digital processing chain ensures minimal impact of external parameter changes and greater flexibility
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
PDPC Sensor Structure
● Configurable event validation (on sub-pixel and pixel level)
● Integrated TDCs on die● Integrated event adding
↪ Timestamp and number of detected photons per pixel
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
PDPC Sensor Array
● 8x8 pixels per array● Readout and control electronics● Temperature sensor● Data correction and calibration
data stored on array● Time sorted events● Upgradeable firmware
↪ Smart tile
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting 9
PDPC TEK Components
Up to 4 smart tiles Base unit for sensor control• USB 2.0 connection
• Supports up to 4 smart tiles
Preinstalled Linux laptop
• Control software
• Calibration tools
Power supplies for base unit
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
The PDPC Technology Evaluation Kit(PDPC-TEK)
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Linux Based Control Software
• Command line interface
• Scriptable for automated measurements
• Source code included for own modifications or integration in own acquisition infrastructure
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Software: Testing Capabilities
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Software: Sensor Status (Power, Temperature, ...)
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Further Software Functionality
• Adjustment of acquisition parameters
– Event validation (thresholds, photon triggers, ...)
– Acquisition settings (integration interval, cell recharge timings, ...)
• Data acquisition
• Calibration for photon saturation, TDC linearity, …
• Temperature monitoring
• Bias voltage adjustments
• Dark count rate measurements
• ...
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Performance Enhancement by Saturation Correction
p=−N⋅ln(1−k N )N: active cellsk: triggered cellsp: # of photons
Digital acquisition allows correction of saturation effect
● Saturation curve upload to smart sensor array
● Automated, on-array correction before readout
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
dSiPM: Dark Count Rate Mapping
● Dark count rate specific to cell● Influenced by production process, radiation damages, ...● Few cells with very high rates
↪ Disabling a small percentage of cells can improve performance significantly
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Comparison of High Dark Count Diodes Influence
Analog SiPM
High dark count cells influence pulse shape
↪ One single cell may render analog SiPM useless
Digital SiPM
High dark count cells can be selectively
disabled
↪ Digital SiPM still functional
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Disabling High Dark Count Cells
● Scanning sensor with single cells in pixel enabled (software based)● Measurement of dark counts allows detection of high count rate cells● Upload inhibit memory map to sensor for cell deactivation
↪ Dark count conditions already improved without chip cooling
Pixel 1 Pixel 4 Pixel 1 Pixel 4
Dark count map Inhibit memory map
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Application: Slow Scan Imaging
● Measurement with single cells enabled● Scan over full sensor area● High resolution imaging, although slow (~15 min acquisition)
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Coincidence Measurements
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Timing Performance (Demonstrator Chip)
Preliminary
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
Your Application Here
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PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
The PDPC-TEK: What You Get
● Hardware:● Smart tiles (1-4)● base unit for tile control and
readout● laptop (preinstalled)● power supplies● cabling
● Software for configuration, measurement, testing (source code included).
● Firmware for sensor array and base unit
● Setup, testing and training on site
● 3 years of support
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
http://www.philips.com/digitalphotoncounting
PDPC Cruise Dinner June, 10th 2011 - Philips Digital Photon Counting
The PDPC dSiPM Sensor
● 4 pixels per sensor● 6396 cells per
pixel● On-chip
● validation,● timing, and ● control logic.
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