A Theory of Noise for Electron Multipliers

Abstract

The noise in secondary-emission electron multipliers is considered from a theoretical viewpoint. The noise properties of a stage are correlated with its secondary-emission properties: the mean value m and mean-square deviation δ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of the number of secondaries per primary. If IpA2 and IsAf2 denote the mean-square noise current lying in the frequency band Δf in the primary- and secondary-electron currents, then 1aAf2= m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I, PV2+ 622eI,, Af where Ī <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> is primary direct current. This result is applied to many-stage multipliers. For n similar stages I, f2= M2I2PA2+ f 2[ M( M )/ m( m21)] 2eIpAf where M=m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> is the over-all gain of the multiplier.