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Mark Tate - Integrating Hybrid Pixel Detectors - BES Detector Workshop 2012 Cornell University

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Integrating Hybrid Pixel Detectors Mark W. Tate

Cornell University

• Intro to Pixel Array Detectors and Integrating PADs

• Survey of Detectors

• Facility Driven Needs

• Areas for R&D

• Summary


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Cornell PAD Group

• Actively working on PAD projects at Cornell:

– Darol Chamberlain

– Kate Green

– Marianne Hromalik

– Hugh Philipp

– Prafull Purohit

– Mark Tate

– Joel Weiss

– Sol Gruner

• PAD Design Collaborators:

– Area Detector Systems Corp.

– SLAC

• Past PAD Group Members:

– Dan Schuette

– Alper Ercan

– Tom Caswell

– Matt Renzi

– Guiseppe Rossi

– Sandor Barna

– Bob Wixted

– Eric Eikenberry

– Lucas Koerner

• Support:

– U.S. Dept. of Energy

– U.S. National Inst. Health

– U.S. National Science Found.

– Keck Foundation


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Large signal/x-ray Single photon sensitivity possible Energy resolution – w/ pulse height circuitry

Excellent PSF Charge cloud ~ 15 micron spread ** Signal < 10-4 in next pixel

Prompt signal collection ~ several ns collection **

Application specific pixel circuitry Electronic shuttering Photon counting High speed imaging Fast readout (~ msec framing possible) Increased dynamic range In-pixel frame storage Adaptive gain Phase-locked integration ...

Advantages of PADs

2740 20 e- / 10keV x-ray

X-rays

** can change for large pulses


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PADs come in two varieties

Photon counting PADs

• Front ends count each x-ray individually. (PILATUS, Medipix, Timepix, XPAD, etc.) Out growth of HEP.

• Many more are coming, especially from Europe.

• Instantaneous count-rate limited to ~106 -107x-rays/pix/sec.

SLS PILATUS

Integrating PADs • Use an integrating front-end to avoid the count-rate bottleneck.

• Capable of handling enormous count-rate.

• Proper signal recorded across pixel boundaries

• Cornell 100x92 pix prototype, first PAD to be applied.

• Existing variants include CSPAD, MMPAD.

• In the works: Cornell Keck PAD, AGIPD, LPD,

ADSC MM/Digital PAD, SOPHIAS, etc.

Cornell-SLAC LCLS

Cornell 100x92

prototype


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Integrating PAD Advantages: Recording small features at pixel boundaries

MMPAD raw data

Pixel 1

Pixel 2

Pixel 3

X-ray beam

Integrated spot intensity constant through charge sharing region!


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Example: Well Calibrated CCD

Variation of spot intensity over

multiple locations Tate, et al., J. Appl. Cryst. (1995), 28, 196-205.

DQE=(S/Nmeas / S/Nideal)2

There are no noiseless area detectors! Corollary: Every detector is limited in its accuracy.

Lots of reasons: Charge recombination, pixel-to-pixel variations in gain or collection

efficiency, absorption outside active detector region, in-pixel variations in sensitivity, detector gaps, point spread, stability, charge lost to adjacent pixel, etc.

A detector is only as good as it's calibrations. •Careful calibrations do help. Gain variations Image distortions

Geometrical absorption factors

•Fundamental limits to detector calibration. Rarely achieve better than 1% Systematics dominate noise!

Depends on nature of signal - especially challenging Features < 1-2 pixels in size (in-pixel variation in sensitivity) High local count rates (non-linear behavior)

Pixel Array Detectors: Calibration

… but don’t integrating detectors have read/dark noise?

Integrators can be made to threshold for single photons!


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Basic Integrator Front End

• Integration Capacitor Cint

Small - (~50 fF)

Single photon sensitivity

Large (~1 pF)

~104 x-rays full well

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Vref

VHV

Cint

Frame Reset

• Integrator Amplifier

Design to handle expected x-ray flux

e.g. 104 x-rays/s -> 4 A at input

CMOS processes

0.25 m - mature - 3.3V capable

0.18 m - 1.8 to 2.5 V - higher density

…

• Integrator Reset

Electronic shuttering

Sync to beam structure

• Pixel Back End

PAD specific functions


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CB Vb

RE

Output Stage

Input Stage

+60V

Diode

IR

2 pf SE Storage Stage

C1 C2 C3 C4 C5 C6 C7 C8

C1 - C8: 130 fF

Rapid framing (SE, IR closed)

1. select storage cap C1

2. Open IR switch (Frame integration begins)

3. Deselect Storage cap (Integration ends)

4. Close IR

repeat with C2 … C8

Pixel Read (open SE, close RE)

Connect storage caps in sequence with output

Pixels and caps both independently addressable

Rossi, et al., J. Synchr Rad, 6 (1999) 1096.

2x104 x-rays full well 2 x-rays noise 150 ns min frame 600 ns min between frames 150 m pixel

Cornell 100x92 PAD: Microsecond Imaging 8 frame rapid storage

{


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Science with Cornell 100x92 PAD

Trenkle, et al., Applied Physics Letters (2008), 93, 081903

Reactive foil dynamics @ 50 s w/ Hufnagle Group, Johns Hopkins

Cai, et al., Appl. Phys. Lett., 83, 2003, 1671-1673

Liu, et al., Appl. Phys. Lett. 94, 2009, 084101-1 to -3.

MacPhee, et al., Science, 295, 2002, 1261-1263.

Kyoung-Su Im, et al., Phys. Rev.Lett. (2009) 102, 074501

Shock Wave Imaging @ 5 s w/ Jin Wang group at APS

Fuel Sprays @ 5 s

Radiographs +

Tomographic reconstructions w/ Jin Wang group at APS


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Cornell Keck PAD

Koerner & Gruner, J. Synch. Rad. 18 (2011) 157.

Improvements to microsecond imager

Goals: • Image successive synchrotron bunches

- successive frames <150 ns apart

• Multiple accumulation periods per image

- phase to repetitive signal

- (analogous to lock-in)

• Improved data output

- < 1 ms to read frame

16x16 pixel prototype tested

128 x 128 pixel modules under construction


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15 x 200 ns

summed

after read

15 x 200 ns

summed using

in-pixel accumulation

Noise reduced!

Accumulator summing Sums of 15 frame periods

(30 kHz signal)

Cornell Keck PAD 16 x 16 testing

Successive bunch isolation 100 ns integrations

4 bunches - blanks between bunches


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Goals: • Increase dynamic range (107 x-rays/pixel) • Keep high count rates (>108 Hz) • Fast framing (~ 1ms deadtime) • Single photon S/N (S/N=6 @ 8 keV)

• 150 m pixel

Methods: • Integrating pixel w/ digital overflow counter / charge removal • Analog remainder read at end of frame • Fabricated in 0.25 m TSMC 3.3 V, metal on metal capacitors

Chip development: Collaboration with Area Detector Systems Corporation

Mixed Mode PAD Extended Dynamic Range Detector

S.G. Angello, et al, IEEE 2004 Nuc. Sci. Symposium, Rome, (Oct. 16-22, 2004).


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Mixed Mode Pixel Integrating pixel w/ overflow counter / charge reset

Monostable

Vref

Integrator

Vth

Comparator

Sample and Hold

VHV

18-Bit Counter

Analog Vout

Vlow

Vref

Csub

Cint

Frame Reset

Digital Out

100 – 1000 X-ray capacity

High gain for sensitivity

Charge

removal

Exceed threshold:

• remove charge

• increment counter

“Remainder” read

at end of frame

Number of overflows No dead-time for charge

removal

… although it takes 1 s


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MMPAD X-ray Testing Count Rate / Dynamic Range

Aluminum diffraction

CHESS F2 (No beam stop!)

•1 sec integration

•2x107 x-rays/pix

in center

•700 x-rays/pix

in weakest spots

x1

x104 One image displayed

at four scales


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2x3 tiled array of MMPAD chip Assembled 2012 @ Cornell for synchrotron experiments

1100 Hz max framing Large dynamic range High photon rates

Mixed Mode PAD 2x3 Array for kHz Imaging

Ptychography at APS 2-ID-B High dynamic range - low energy 2.5 keV - 108 photons/s in 150 nm focus (w/ Vine, McNulty at APS, Mancuso Group at European XFEL)

1 s image from Pt zone plate 105 photons full scale


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2 ms images from Al3Ni bilayer foil undergoing reactive mixing 5 x-rays / pixel full scale

Photon energy spectrum from single image at left.

Time resolved reactive foil mixing at CHESS A2 Single photon sensitivity - 15 keV (w/ Darren Dale : CHESS, Todd Hufnagle Group : Johns Hopkins)

0, 1, 2, … 15 keV photons

+ Ni fluorescence

Mixed Mode PAD 2x3 Array for kHz Imaging

0.0 s 2.5 s


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LCLS Coherent X-ray Imaging Experiment All the photons arrive in a subpicosecond pulse - Integration required

What to expect from small particle &

xtal scattering at the CXI beamline

Rate: 120 Hz

Energy: 4-8 keV

Signal: << 1 photon/pix to >103/pix

S/N > 3 @ 8keV

Full well > 103 photons

Detector coverage needed:

Pixel Size: 100 - 200 m

# pixels > 500 x 500

CSPAD - Cornell: Detector chips. SLAC: Mechanicals & off-chip electronics

S/N=8

2700

110 m

1516 x 1516


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CSPAD Pixel-Level Schematic

Programmable per pixel

490 fF Low gain

(2700 x-rays)

75 fF High gain (S/N ~8)

In pixel ADC

Global ramp

Philipp, et al., IEEE Trans. Nucl. Sci. (2010). 57, 3795-3799.


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CSPAD @ LCLS - 1.9 Å Structure from microcrystals

Bragg spots typically >> 1 photon/frame

- other experiments will require single photon sensitivity

1.5x106 frames - 4.5% were crystal hits


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Single Module CSPAD 8 keV Photon Energy Histogram

Counting Photons in a Pixel

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# e-/hole pairs = total energy in pixel / 3.65 eV

Set software threshold

Thresholding: Allows suppression of read noise

and dark current at low fluence.

False positive rate set by S/N

0 photons

1 photon

2

3

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False Positive Rates

Threshold set to -

3 : 1x10-3

4 : 3x10-5

5 : 1x10-6


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This ring: ~10-3 photons/pixel/frame

Between peaks: ~ 10-4 photons/pix/frame

Raw sum of 1000 frames Accumulation of read noise

+ detector systematics

Single 10 ms image ~ 30 photons

Single Module CSPAD - Low Flux Diffraction

Same 1000 frames

w/ thresholding

Philipp, Tate, & Gruner, JINST (2011) 6, C11006.


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FELs: Bigger Challenges with Smaller Particles Reconstruction with low fluence images of unknown orientation

But will it work with a real detector

and with real data?

Expectation Maximization Loh & Elser, Phys Rev E, 80(2009)1715.

1. How much information is needed (photons per frame)?

2. Can imager provide the needed S/N?

3. Is there an algorithm that works? (tied to question 1)


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Single Module CSPAD

No rotation

1.2 million x-rays

0.2 x-ray/pix/frame

sum of 432 frames

Turn intensity WAY down and rotate mask: 2.5 x-rays per FRAME (3 frames shown)

Discard angular information for frame

Philipp, Ayyer, Tate, Elser & Gruner, Optics Express, 20 (2012) 13129.


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Mask rotating

1.2 million x-rays

10-4 x-ray/pix/frame

sum of 450,000 frames

No rotation

1.2 million x-rays

0.2 x-ray/pix/frame

sum of 432 frames

Expectation

Maximization

Philipp, Ayyer, Tate, Elser & Gruner, Optics Express, 20 (2012) 13129.

It Works!!


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XFEL AGIPD

B. Henrich, et al., Nucl. Instr. and Meth. A (2010)

European XFEL - 2700 pulses at 4.5 MHz every 0.1 s 3 stage adaptive gain - single photon to 104 photons/pixel

>200 storage elements - 4.5 MHz flash frame operation

200 m pixels (to fit all the storage cells)

Automatic gain switching


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XFEL Large Pixel Detector (LPD)

European XFEL - 2700 pulses at 4.5 MHz every 0.1 s 3 parallel storage stages - multigain

512 storage elements / gain

500 m pixels

Simultaneous recording

at 3 gains

Rutherford Appleton / Glasgow


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Source/Experiment Driven Requirements • Synchrotrons / ERLs / USRs

– 100x92 microsecond imaging

– MMPAD up to 1 kHz imaging for small arrays- large dynamic range

– Keck PAD synchrotron bunch isolation - phased accumulation

o Reduce readout dead time (to <1 s)

o Increase sustained frame rate (to > 1kHz)

o Higher Energy Detectors - HiZ sensors

o Lower Energy Detectors - diode structure limitations - higher sensitivity electronics

o Even small detectors (with existing capabilities) will make a big impact

• LCLS + other low duty pulsed FELs

– CSPAD single photon to 3000 x-rays/pixel

o Extend dynamic range and low energy operation

o Is the low end low enough? (e.g. use higher sensitivity front end)

o Can we extend full well to 106 or 107 per pulse?

charge collection from diode slows @ large pulse- use MMPAD approach? Nonlinear

integrators?)

• European XFEL - rapid multiframe storage

– AGIPD, LPD

o These detector types will be useful at other sources as well

27 O = suggested areas for effort - = exists or in the works


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Areas for R&D

• Extended dynamic range at high instantaneous rates (e.g. FELs)

• Understand sensor dynamics at high photon densities

• Single bunch imaging (limits to timing?)

• Phased integration of repeating signal (lock-in)

• Through Silicon Vias (TSV) / packaging for larger tiled arrays / 3D integration

• Smaller pixels - (but…lower voltages for smaller feature processes)

• Edgeless sensors

• Hi-Z Sensors

• Low energy sensor windows / increase pixel sensitivity

• Silicon On Insulator (SOI)

• Calibration procedures / tools for characterization

pixels are multigain, multiframe, etc.

test rate dependence, energy dependence, timing, …


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Summary

Needed Efforts for Integrating PADs

• Improve dynamic range

• Take advantage of timing structure of beam

– Single bunch imaging (limits to timing?)

– Phased integration of repeating signal (lock-in)

– Use low rep rate of LCLS to extend dynamic range

• High energy (>20 keV) detectors

• Low energy (< 4 keV) detectors

• Sensor improvements

• Smaller pixels

• Improvements to packaging / 3D integration

• Streaming images at > 1 kHz

• Spend time on Calibrations

• Get detectors on Beamlines!

– including small versions of existing detectors

• Tight feedback loop between users and developers

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