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Characterisation ofCharacterisation ofActive Pixel SensorsActive Pixel Sensors

Dima ManeuskiDima Maneuski1st year PhD Student1st year PhD StudentUniversity of GlasgowUniversity of Glasgow

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OutlineOutline

• What is APS? What is CCD?What is APS? What is CCD?• Vanilla APSVanilla APS• HEPAPS4HEPAPS4• What do we actually need to characterise?What do we actually need to characterise?• Photon transfer techniquePhoton transfer technique• Experimental setupExperimental setup• Status on Prague activityStatus on Prague activity

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We live here in Kevin BuildingWe live here in Kevin Building

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Basic CCD cameraBasic CCD camera

Advantages:Advantages:

• Low noise;Low noise;• High full-well High full-well capacity;capacity;• 100% fill factor;100% fill factor;• High uniformity;High uniformity;• Mature technology;Mature technology;

Disadvantages:Disadvantages:

• Slow readout;Slow readout;• Pixel blooming;Pixel blooming;• Specialised Specialised fabrication;fabrication;• Low functionality;Low functionality;

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Basic CMOS cameraBasic CMOS camera

Advantages:Advantages:

• High Speed readout;High Speed readout;• Random access;Random access;• On-chip intelligence;On-chip intelligence;• Low power Low power consumption;consumption;

Disadvantages:Disadvantages:

• High read-out noise;High read-out noise;• Reduced dynamic Reduced dynamic range;range;• Reduced uniformity;Reduced uniformity;• Reduced fill-factor;Reduced fill-factor;• High cost;High cost;

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Vanilla APSVanilla APS• 512 x 512 pixels – 25 512 x 512 pixels – 25 m squarem square• Fill Factor ~ 85 %Fill Factor ~ 85 %• Optional soft/hard/flushedOptional soft/hard/flushed• Analogue and digital outputAnalogue and digital output• up to 100 fps at 12 bit digital up to 100 fps at 12 bit digital outputoutput• Flexible ROIs (up to 6 x 6 @ Flexible ROIs (up to 6 x 6 @ 20kHz in analogue output)20kHz in analogue output)• 100k 100k ––e full well capacitye full well capacity

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Flushed ResetFlushed Reset• Soft reset results in a Soft reset results in a

lowered reset noise lowered reset noise (kTC/2)(kTC/2)1/21/2 instead of instead of (kTC)(kTC)1/21/2

• However, frames taken However, frames taken utilising soft reset are utilising soft reset are affected by image lag, affected by image lag, where the current image where the current image is affected by the previous is affected by the previous frame.frame.

• Using hard reset, image Using hard reset, image lag is overcome, but lag is overcome, but results in full (kTC)results in full (kTC)1/21/2 noise noise and reduced full well and reduced full well capacity.capacity.

• By using a hard reset By using a hard reset followed by a soft reset, it followed by a soft reset, it is possible to get the best is possible to get the best of both reset methods. of both reset methods. This is known as flushed This is known as flushed reset.reset.

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Region of InterestRegion of Interest• 12 bit digital output for full frame mode.12 bit digital output for full frame mode.• Region of Interest (ROI) readout for up to 6 ROI (6 x 6 pixels/ROI).Region of Interest (ROI) readout for up to 6 ROI (6 x 6 pixels/ROI).• 20kHz analogue readout at 10 bits resolution for ROI.20kHz analogue readout at 10 bits resolution for ROI.

520x520 – 4fps520x520 – 4fps 200x200 – 28fps200x200 – 28fps 50x50 – 432fps50x50 – 432fps

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HEPAPS4HEPAPS4

• 1024 x 384 pixels – 15 mm 1024 x 384 pixels – 15 mm squaresquare• 100 % efficiency for MIPs100 % efficiency for MIPs• 20um epi20um epi• Radiation hard ( > Mrad) (?)Radiation hard ( > Mrad) (?)

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Spectral ResponseSpectral ResponseRefers to the detected signal response as a function of the wavelength Refers to the detected signal response as a function of the wavelength of light. Often expressed in terms of the Quantum Efficiency, a of light. Often expressed in terms of the Quantum Efficiency, a measure of the detector's ability to produce an electronic charge as a measure of the detector's ability to produce an electronic charge as a percentage of the total number of incident photons that are detected.percentage of the total number of incident photons that are detected.

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Dynamic RangeDynamic RangeA measure of the maximum and minimum A measure of the maximum and minimum intensities that can be simultaneously detected in intensities that can be simultaneously detected in the same field of view. It is often calculated as the the same field of view. It is often calculated as the maximum signal that can be accumulated, divided maximum signal that can be accumulated, divided by the minimum signal which in turn equates to by the minimum signal which in turn equates to the noise associated with reading the minimum the noise associated with reading the minimum signal. It is commonly expressed in decibel scale.signal. It is commonly expressed in decibel scale.

Camera GainCamera GainThe camera gain is the conversion factor that The camera gain is the conversion factor that relates the ADU value to the number of electrons relates the ADU value to the number of electrons collected by a pixel.collected by a pixel.

Signal to Noise RatioSignal to Noise Ratio

The comparison measurement of the The comparison measurement of the incoming light signal versus the various incoming light signal versus the various inherent or generated noise levels, and is a inherent or generated noise levels, and is a measure of the variation of a signal that measure of the variation of a signal that indicates the confidence with which the indicates the confidence with which the magnitude of the signal can be estimated.magnitude of the signal can be estimated.

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LinearityLinearity

non-linearitynon-linearityis based on the error between is based on the error between the best-fit straight-line to the the best-fit straight-line to the original data of the camera original data of the camera input vs. the camera mean input vs. the camera mean response at each illumination response at each illumination level, in ADU’slevel, in ADU’s

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Noise, noise, noise…Noise, noise, noise…

• • Read NoiseRead Noise: inherent output amplifier : inherent output amplifier noisenoise• • Dark NoiseDark Noise: thermally induced noise : thermally induced noise arising from the camera in the absence of arising from the camera in the absence of light light • • Shot NoiseShot Noise (Light Signal): noise arising (Light Signal): noise arising out of the stochastic nature of the photon out of the stochastic nature of the photon flux itselfflux itselfSensorSensorPhoton noise, dark current, fixed Photon noise, dark current, fixed pattern noise, and shot noisepattern noise, and shot noiseElectronicsElectronicsreset noise, quantization noisereset noise, quantization noise

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Photon Transfer CurvePhoton Transfer CurveMeasuring noise with noise• The camera is a system block

with light as an input, and digital data as an output

• The only noise introduced at the input is shot noise.

• Any difference between the noise at the input and the noise at the output is sensor and/or electronics noise.

!),(

x

eSxSP

Sx Mean = S (signal)Mean = S (signal)

Standard deviation = SStandard deviation = S1/2 1/2 (Noise)(Noise)

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Photon Transfer CurvePhoton Transfer Curve

Direct dataDirect data• Read noiseRead noise• GainGain• Full wellFull well

Indirect dataIndirect data • Dynamic rangeDynamic range• SNRSNR• Linearity (if power of LED is known)Linearity (if power of LED is known)

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HEPAPS4 PTCHEPAPS4 PTC

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Performance Parameter Value Units

Camera Gain 10.9 electrons/DN

Read Noise 51 electrons

Full Well (ADC saturation)

~ 4 x 104 electrons

SNR 47 dB

Dynamic Range 70 dB

VanillaVanilla

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Prague activityPrague activity

Calibration of MXRs for ATLASCalibration of MXRs for ATLAS

• 55Fe 6 KeV• 241Am 50 KeV, 14 KeV• 252Cf 2 MeV• AmBe 4 MeV

Results in numbersResults in numbers

• 16 MXRs calibrated with Am and Fe

1 in progress, 4 left• 10 MXRs calibrated with Sr• 4 MXRs calibrated with neutrons

0 5 10 15 20 25 30 35 40 45 50 55 60 65

50

100

150

200

250

300

350

400

450

-0,16

-0,14

-0,12

-0,10

-0,08

-0,06

-0,04

-0,02

0,00

0,02

241Am - 59,5KeV

241Am - 13,9KeV

Energy Calibration for Assembly 2 - F03-W0048

THLY = A + B * X

Parameter Value Error--------------------------------------------A 473,59 6,57145B -6,7857 0,18539--------------------------------------------

TH

L

Energy (KeV)

55Fe - 6KeV

TH

L-F

BK

THL-FBKY = A + B * X

Parameter Value Error------------------------------------------------A 0,01808 5,21937E-4B -0,00276 1,47244E-5------------------------------------------------

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Thank you for attention!Thank you for attention!

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University of Glasgow, Scotland1st - 5th September 2008

The conference explores the scientific and technical developments of detector systems used in: Astronomy and space

science; Astrophysics; Condensed matter studies; Industrial applications;

Life sciences; Medical physics; Nuclear Physics, Particle physics and Synchrotron based science.

National Organising

Committee(subject to change)

P.P. Allport, LiverpoolR.L. Bates, GlasgowA.J. Bird, SouthamptonC.R. Cunningham, UK

ATC, EdinburghG.E. Derbyshire,

STFC, RALP. Evans, ICR, London R. Farrow, STFC,

DaresburyW. Faruqi, MRC,

CambridgeM. Grande,

AberystwythP.R. Hobson, BrunelD.P. Langstaff,

AberystwythP.J. Nolan, LiverpoolD.J. Parker,

BirminghamP.J. Sellin, SurreyA. Smith, MSSL,

LondonR. Speller, UCL,

LondonT.J. Sumner, IC,

LondonS. Watts, Manchester

psd8@physics.gla.ac.ukhttp://www.psd8.physics.gla.ac.uk

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Metal layers

Polysilicon

P-Well N-Well P-Well

N+ N+ P+ N+

Dielectric for insulation and passivation

Radiation

------

- +++++++

- +- +- +

P-substrate

P-epitaxial layer

Potential barriers

epi

sub

N

Nln

q

kTV

Concept first proposed in 1999, and published in NIM in 2001 (R. Turchetta et al.)