Effects Of Background Plasma Research Articles

Feasibility study and CXRS synthetic diagnostic model for COMPASS upgrade based on Cherab and Raysect framework

In this article the forward model and feasibility study of the CXRS (Charge Exchange Recombination Spectroscopy) diagnostic for the COMPASS Upgrade tokamak [1] based on the Raysect and Cherab framework [2–4] is presented. The neutral beam model available in Cherab is expanded and based on individual acceleration grid beamlets. The spatial density distribution calculation takes into account 3D geometry of the port structure. Beam density profile calculated with the expanded model is used to estimate realistic radial resolution of measurement and to produce forward models of the spectra. Effects of background plasma and beam halo are not included. The spectra are used to reconstruct the plasma profiles and are compared with the simulation input to estimate measurement errors with respect to positions of collecting optics.

Energy enhancement of proton acceleration in combinational radiation pressure and bubble by optimizing plasma density

The combinational laser radiation pressure and plasma bubble fields to accelerate protons are researched through theoretical analysis and numerical simulations. The dephasing length of the accelerated protons bunch in the front of the bubble and the density gradient effect of background plasma on the accelerating phase are analyzed in detail theoretically. The radiation damping effect on the accelerated protons energy is also considered. And it is demonstrated by two-dimensional particle-in-cell simulations that the protons bunch energy can be increased by using the background plasma with negative density gradient. However, radiation damping makes the maximal energy of the accelerated protons a little reduction.

Three-Dimensional Particle Acceleration in Electromagnetic Dominated Outflows with Background Plasma and Clump

The effect of background plasma on particle acceleration via Poynting fluxes is studied in 3D PIC simulation of electron-positron and electron-ion plasmas. When a strongly magnetized ejecta at the center expands to low-temperature electron-positron ambient plasma background and a low-density clump, electromagnetic wave front accelerates particles in the background and clump, and captures them in the Ponderomotive potential well. We do not observe any instability, and the momentum distributions of background and clump form a power law of slope close to −1.5 with a sharp peak in the middle. When an ejecta expands to the ion-electron interstellar medium (ISM), the acceleration via Poynting flux is severely damped due to the charge separation.

Effects of Background Plasma on Free Electron Laser with Planar Wiggler

Dispersion equation of planar-wiggler free-electron laser with background plasma is derived using linear fluid theory. The characteristic of this plasma FEL is analyzed in detail. It is shown that reasonable background plasma density tends to improve FEL growth rate. We also find there exits a critical plasma density for FEL operating. When the background plasma density is higher than critical density, the FEL can no longer be excited.

Linear theory of plasma filled backward wave oscillator

An analytical and numerical study of backward wave oscillator (BWO) in linear regime is presented to get an insight into the excitation of electromagnetic waves as a result of the interaction of the relativistic electron beam with a slow wave structure. The effect of background plasma on the BWO instability is also presented.

Two-dimensional modeling of x-ray output from switched foil implosions on Procyon

A series of two-dimensional radiation magnetohydrodynamic calculations are presented of a Z-pinch implosion using a plasma flow switch. Results from a recent experiment using the high explosive driven generator Procyon, which delivered 16.5 MA to a plasma flow switch and switched about 15 MA into a static load, are used to study the implosion of a 29 mg load foil [J. H. Goforth et al., ‘‘Review of the Procyon Explosive Pulsed Power System,’’ in Ninth IEEE Pulsed Power Conference, June 1993, Albuquerque, edited by K. R. Prestwich and W. L. Baker (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1993), p. 36]. The interaction of the switch with the load plasma and the effects of background plasma on the total radiation output is examined. Models which assume ideal switching are also included. Also included are the effects of perturbations in the load plasma which may be associated with initial vaporization of the load foil. If the background plasma density in the switch region and in the load region does not affect the dynamics, the pinch is predicted to produce a total radiation output of about 4 MJ. Including perturbations of the load plasma associated with switching and assuming a background plasma density after switching in excess of 10−7 g/cm3 results in a total output from the pinch of about 0.6 MJ.

Effect of background plasma on slow cyclotron waves of electron beam

The effect of plasma loading in the field structure and dispersive characteristics of slow cyclotron waves propagated in electron beams is studied. A requirement is established for the maximum permissible plasma concentration at which a slow cyclotron wave can be used for collective ion acceleration. The degree of vacuum required for operation of an autoresonant accelerator is estimated.

The effect of background plasma in the undulator on free electron lasers

A new unconventional FEL scheme (named PFEL), which has injected rarefied ionized background plasma in the undulator, is studied theoretically. It is shown that there exists a critical density np; for the background plasma. When the background plasma density np is higher than np c, the FEL can no longer be excited. When np ≲ np c, the laser gain for Raman FEL may be increased noticeably.