COMPUTATIONAL MODEL ANALYSIS FOR EXPERIMENTAL OBSERVATION OF OPTICAL CURRENT NOISE SUPPRESSION BELOW THE SHOT-NOISE LIMIT

In this paper we present simulation analysis of experi- mental results which demonstrate noise suppression in the optical regime, for a relativistic e-beam, below the classi- cal shot-noise limit. Shot-noise is a noise resulting from the granular nature of the space-charge in an e-beam. It is linear to the beam current due to its Poissonic distribution in the emission process. Plasma oscillations driven by col- lective Coulomb interaction during beam drift between the electrons of a cold intense beam are the source of the effect of current noise suppression. The effect was experimen- tally demonstrated [1] by measuring Optical Transition Ra- diation (OTR) power per unit e-beam pulse charge. The in- terpretation of these results is that the beam charge homog- enizes due to the collective interaction (sub-Poissonian dis- tribution) and therefore the spontaneous radiation emission from such a beam would also be suppressed (Dicke’s sub- radiance [2]). Analysis of the experimental results using GPT simulations will demonstrate the suppression effect. For the simulation results we used a full 3D GPT model of the ATF section in which the experiment took place at.