Collective microdynamics and noise suppression in dispersive electron beam transport

Abstract

A general formulation is presented for deep collective interaction micro-dynamics in dispersive e-beam transport. In the regime of transversely coherent interaction, the formulation is applicable to both coherent and random temporal modulation of the electron beam. We demonstrate its use for determining the conditions for suppressing beam current noise below the classical shot-noise level by means of transport through a dispersive section with a small momentum compaction parameter.

Beating the shot-noise limit

“…In electron-beam transport under appreciable space-charge conditions, the microdynamic noise evolution process may be viewed as the stochastic oscillations of Langmuir plasma waves 1 . In the linear regime, the evolution of longitudinal current and velocity modulations of a beam of average current I b , velocity βc and energy E = (γ −1)mc 2 , can be described in the laboratory frame by 17 :…”

“…The single-frequency Langmuir plasma wave model expression (3) can be solved straightforwardly in the case of uniform drift transport. After employing an averaging process, this results in a simple expression for the spectral parameters of stochastic current and velocity fluctuations (noise) in the beam assuming that they are initially uncorrelated 1,17 :…”

“…Theory predicts that much bigger factors of shot-noise suppression are possible in more favourable configurations, and schemes have been suggested for producing the noise suppression process in shorter lengths using dispersive transport 17,21 (dispersive transport The experimental set-up is presented in Fig. 2.…”

Subradiant spontaneous undulator emission through collective suppression of shot noise

“…The chicane is a factor of 30 shorter than the accelerator, so the second assumption is safe. However, the first assumption may not be satisfied strongly, and it is possible that the particles have gone through a portion of a plasma oscillation before reaching the chicane [31,32]. In this case, even with R 56 ¼ 0 mm, we would expect some degree of subradiance.…”

High-Power Terahertz Free Electron Laser via Tapering-Enhanced Superradiance

“…Spontaneous undulator radiation [47][48][49][50] by a beam of randomly injected electrons is incoherent. Thus, the total emitted radiation energy is proportional to the number of electrons (N e ), while the field average vanishes due to random interference of the generated wave packets [51,52]. To obtain superradiance [53,54], it is required that the electron bunch duration (t b ) will be shorter than the radiation period (t b << 2π ω ).…”