Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1907.01391

Amplification of coupled nonlinear oscillations of charged particle beam in crossed magnetic fields

A. R. Karimov·A. M. Bulygin·P. A. Murad
View original source ↗Read source document ↗Export metadata ↓

Abstract

A non-relativistic, charged-particle beam is placed into a crossed magnetic field. For such a system, the nonlinear electrostatic oscillations generation in the different degrees of the beam freedom may be triggered by the energy/momentum exchange between the beam's particles and these external fields. The influence of oscillation dynamics of these fields and beam have been studied based on the cold-fluid hydrodynamic description. As a result, the necessary conditions under resonant amplification of the beam's natural oscillations are identified. Present results demonstrate that the beam density increases when the amplitude of radial and axial velocities increase. This process decreases the radius of the beam over the course of time. The technical application of the process applies in real accelerators such as a gyrotrons, FELs, and cyclotrons, where transverse size is limited by the size of the vacuum chamber. Thus redistribution of energy between the external field and the kinetic energy of the beam can effectively accelerate the beam by using an external magnetic field. These fields with both axial and radial directions use further this beam as an effective light source by identifying the resonance frequency to improve stability, focus particles, and wave propagation.

Explore related subjects

physics.plasm-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. R. Karimov, A. M. Bulygin, P. A. Murad. 2019-06-28. Amplification of coupled nonlinear oscillations of charged particle beam in crossed magnetic fields. https://arxiv.org/abs/1907.01391

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Two-length spatial correlation function of turbulence in TCV

Spatial correlation functions of density fluctuations are measured in the Tokamak à Configuration Variable (TCV) using a dual-channel Doppler backscattering (DBS) diagnostic. In certain cases, the spatial correlation function exhibits two characteristic length scales. By analogy with nonlinear reduced simulations, the presence of two correlation lengths may be indicative of avalanche-like transport. The correlation functions obtained from DBS are compared with those from short-pulse reflectometry measurements and show reasonable agreement. Both short- and long-range correlations are measured in the same plasma geometry for different heating powers. Short-scale correlation lengths are found to be on the order of 3-5 Larmor radii, while large-scale correlations extend over approximately 5-15 Larmor radii. The correlations are found to decrease towards the very edge of electron cyclotron heated discharges, coinciding with a narrow Er well.

physics.plasm-ph↗
arXiv2026

Direct observation of electron shedding from a laser-plasma accelerator

Laser-plasma accelerators have demonstrated the ability to produce ultrashort relativistic electron bunches with peak currents suitable for compact light sources, ultrafast diffraction, and strong-field studies. However, their performance critically depends on preserving the longitudinal phase-space density of the beam as it exits the plasma accelerator. Here, we report the first direct observation of a previously unresolved process in which a highly charged electron bunch undergoes significant longitudinal expansion and progressively loses electrons during extraction from a laser-driven wakefield accelerator, a phenomenon we refer to as electron shedding. Using femtosecond relativistic electron microscopy, we tracked the evolution of the beam far beyond the accelerator exit and observed the bunch stretching over many plasma wavelengths before shedding electrons during propagation. Particle-in-cell simulations reproduce the observed behavior and reveal that it originates from a combination of effects when a high-charge-density beam exits the accelerator. These dynamics redistribute energy from the beam head into a low-energy tail, thereby reducing the useful peak charge density and ultimately decreasing the efficiency of the laser-plasma accelerator. Our results provide new insight into beam extraction and phase-space evolution in laser plasma accelerators and highlight the importance of controlling these collective effects for future applications.

physics.plasm-ph↗
arXiv2026

Pfirsch-Schlüter Current

The Pfirsch-Schlüter current is a current that flows along the magnetic field lines in a toroidal plasma equilibrium that is required to make the plasma current density divergence free in the presence of a plasma-pressure gradient. A distortion in the plasma shape is caused by the Pfirsch-Schlüter current, and it is desirable to minimize both the strength and the distance this current flows along the magnetic field lines. The Pfirsch-Schlüter current is localized within a half period of a stellarator when $d\ell/B$ integrated over the half period is the same for all lines in the magnetic surface. It is shown that within parts in a thousand this is the same condition as the distance $\ell_{s}$ required for a field line to cross the half period being the same for all lines in the surface. To make the $\ell_{s}$'s the same, the lines started on the small major radius side of the plasma must undergo wiggles to make their $\ell_{s}$ as long as those started on the outboard side. This is generally achieved using modular coils with a large helical component on the small major radius side but could be achieved with a central column carrying a helical current.

physics.plasm-ph↗