Ultra Start KE-6 Specifications download pdf (Page 40)

Version 1.1 rev Jan 2013

Page 40

iXon Ultra

Features & Functionality

3.1.3 - EM Gain ON vs EM Gain OFF

Signal to Noise (S/N) plots derived from the specications of the back-illuminated iXon Ultra EMCCDs (Figure 9), read

out at 10MHz for a photon wavelength at which the Quantum Efciency (QE) of the sensor is assumed to be 90%.

Such plots are very useful to gauge at what signal intensity it becomes appropriate to use EM Gain to increase S/N.

It is clear that at 10MHz readout, one needs relatively intense signals of > 2900 photons / pixel before it becomes

advantageous to operate with EM Gain off. Note that the “ideal” curve represents a pure Signal to Shot Noise ratio

and is shown for reference – if the camera had no sources of noise, this is what the curve would appear like. Even with

EM Gain turned on, we encounter uniformly lower signal to noise than the ideal curve. This is due to the inuence of

Multiplicative Noise, which has the effect of increasing the shot noise by a factor of √2 or ~1.41.

Figure 9: Signal to noise plots EM Gain ON vs. EM Gain OFF for back-illuminated iXon Ultra EMCCDs at 10MHz readout speed

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Ultra Start KE-6 Specifications Page 40