Presentation on theme: "Electron Multiplying CCDs"— Presentation transcript:
1 Electron Multiplying CCDs An IntroductionSimon Tulloch
2 Electron Multiplying CCDs Multiplication registerStore AreaImage AreaNormal Serial registerAvalanche multiplication takesplace in Multiplication Register,using an HV clock (40-45Volts).Multiplication register1e- in1000e- signal outMultiplication registerStandard MOSFETamplifierCommercially available :CCD x 128CCD87/ x512CCD201 1K x 1K
4 Multiplication Clocking 1 In this diagram we see a small section of the gain registerGain electrodePotential Energy
5 Multiplication Clocking 2 Gain electrode energised. Charge packets accelerated strongly into deep potential well.Energetic electrons loose energy through creation of more charge carriers (analogous tomultiplication effects in the dynodes of a photo-multiplier) .Gain electrodePotential EnergyPotential Energy
6 Multiplication Clocking 3 Clocking continues but each time the charge packets pass through the gain electrode, furtheramplification is produced. Gain per stage is low, <1.015, however the number of stages is high so thetotal gain can easily exceed 10,000Potential EnergyPotential Energy
7 Multiplication NoiseFlat fields taken with an EMCCD show unusual statistics. The variancein the flat fields is no longer equal to the mean signal as is expectedwith photon statistics.Effect is to increase the photon noise by a a factor of
8 EMCCD becomes competitive at lower exposure levels With EM Gain: At low illumination, photons are resolved.Without EM Gain: object only just visible above noise.Also visible is the Clock Induced Charge (CIC) whichis the dominant noise source (typical value 0.03e-)
9 EMCCD range of operation So at higher expsoure levels the EMCCD actually performs worse than a normal CCDEMCCDEMCCD wins due to zero read noiseEMCCD loses due to multiplication noise
10 Early EMCCD Demonstrations 1) Crab Nebula pulsar at 180fps2) Photon interference in the labThresholdCryogenic CCD87 imaging a faint pinholeRaw input framesThresholded and accumulatedParticles? Waves?
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