= Stochastic cooling
{wiki}
<Simon van der Meer>'s <stochastic cooling> uses measured beam fluctuations, a pick-up, <amplifier> and timed kicker. Finite samples supply the signal; other <particles> and electronic <noise> contribute unwanted kicks. Delay and oscillation phase must make the correction oppose the sampled deviation.<Stochastic Cooling and the Accumulation of Antiprotons by Simon van der Meer>[1984 lecture, sections 2–3, p.292 onward; section 5, p.295]{ref}
This active system dissipates <energy>; it is no one-particle <Maxwell's demon> individually tracking <antiprotons>. The <stochastic cooling variance model> isolates the tradeoff.
\Image[/stochastic-cooling-pickup-delay-kicker.png]
{title=Measured beam fluctuations drive a delayed kicker, while excessive gain amplifies noise}
{description=Original functional signal path, not a mechanical or scale drawing of a historical ring. Beam flight and electrical signal paths are distinct; phase and delay must make the correction oppose the sampled deviation. The graph is the stipulated scalar model with initial variance one and independent noise variance one quarter; it is not a measured cooling curve.}
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