Electron Cyclotron Absorption Research Articles

Analytical approximations for the electron cyclotron absorption coefficient at the fundamental frequency in the Doppler regime

The index of refraction and the electron cyclotron absorption coefficient at ω≊ωc in the Doppler regime are examined for a plasma in thermal equilibrium. Regimes where the known analytical approximations fail are quantitatively delineated. The exact numerical solution to the dispersion relation is given in the regimes where known analytical theory fails.

Electron Cyclotron Heating in Weakly Relativistic Finite-Beta Tandem Mirror Plasmas

Electron cyclotron resonance frequency wave and absorption theory and ray tracing are reviewed and a numerical model for the study of electron heating in tandem mirror plugs and barriers is presented. It is found that substantial shifts in the spatial energy deposition profile occur from the cold plasma electron cyclotron resonance at elevated temperatures and that surface absorption can be substantial. The O-mode exhibits a ray trajectory that more easily penetrates to the plasma core and has an adequate single-pass absorption at temperatures >10 keV.

A theory of currents induced by radio-frequency waves in toroidal plasmas

A Fokker-Planck treatment of the plasma electron current driven by radio-frequency waves is presented for the electron cyclotron and Landau damping wave absorption mechanisms. Electron-electron collisions are taken into account using the full Fokker-Planck collision operator which leads to an integro-differential equation for the perturbation of the electron distribution function produced by the wave. This equation is solved analytically in the Lorentz gas approximation and numerically in its full form. Efficient current drive is predicted for high phase velocity waves in the electron cyclotron scheme while Landau damping is efficient at both high and low phase velocities. The reduction of the current due to trapping of electrons in a Tokamak field configuration is calculated and a dramatic suppression of the current is predicted for low phase velocities. The efficiency of driving currents with waves is found to be comparable with that obtained using fast ion beams but much less than that using steady electric fields. A comparison with an idealised wave shows that the two practical schemes considered are far from optimum.

A theoretical study of electron-cyclotron absorption in ELMO Bumpy Torus

The basic features of microwave propagation and electron-cyclotron damping in ELMO Bumpy Torus (EBT) devices are investigated to provide an understanding of the heating of the toroidal core plasma component. The characteristics of microwave propagation in EBT geometry, where there is strong variation of along field lines, are described and contrast is made with the electron-cyclotron heating (ECH) of tokamaks. Linear cyclotron damping calculations are presented for plasmas having parameters typical of EBT-I and parameters projected for EBT-II. It is shown that the extraordinary mode is completely absorbed near the fundamental cyclotron resonance when propagating from the high-magnetic-field side (mirror throat). For EBT-I parameters, heating by the ordinary mode at the fundamental cyclotron resonance and by both modes at the second-harmonic resonance is negligible. For projected EBT-II parameters, the ordinary mode is heavily damped at the fundamental and the extraordinary mode is heavily damped at the second harmonic. Since the right-hand cut-off prevents injected extraordinary-mode energy from propagating to the cyclotron resonance, a mechanism must exist outside of geometrical optics by which the extraordinary mode reaches resonance. It is argued that this mechanism is the conversion of ordinary-mode energy to extraordinary mode in the high-field region upon wall reflection.

Cyclotron resonance study of conduction electrons in n-type indium antimonide under a strong magnetic field. (II) hot electrons

Abstract A system of hot electrons in the n -InSb under the application of a strong magnetic field has been studied by far IR cyclotron resonance. A three band model and an energy independent scattering time were assumed in analyzing the line shape variation with electric field applied either parallel or perpendicular to the magnetic field. Two kinds of electron temperature, inter- and intra-subband, were introduced to describe the electron distribution in energy space. The electron distribution function was found to deviate from an essentially Maxwellian form in the manner predicted by Yamada and Kurosawa. A remarkable difference exists between the two geometries: E∥H and E ⊥ U . A brief survey of cyclotron emission, and the reverse process of hot electron cyclotron absorption, is summarized at the end as an addendum.

Cyclotron resonance study of conduction electrons in n-type indium antimonide under a strong magnetic field—II: Hot electrons

A system of hot electrons in the n-InSb under the application of a strong magnetic field has been studied by far IR cyclotron resonance. A three band model and an energy independent scattering time were assumed in analyzing the line shape variation with electric field applied either parallel or perpendicular to the magnetic field. Two kinds of electron temperature, inter- and intra-subband, were introduced to describe the electron distribution in energy space. The electron distribution function was found to deviate from an essentially Maxwellian form in the manner predicted by Yamada and Kurosawa. A remarkable difference exists between the two geometries: E∥H and E⊥ U. A brief survey of cyclotron emission, and the reverse process of hot electron cyclotron absorption, is summarized at the end as an addendum.

Penetration of a strong electromagnetic wave in an inhomogeneous plasma generated by ECR using a magnetic beach

This paper deals with the penetration of a strong electromagnetic wave into a dense inhomogeneous plasma generated by electron cyclotron absorption of this wave on a magnetic beach. It was experimentally found that the plasma density increases considerably after a certain time. This increase of plasma density is due to a passage of an electromagnetic wave through an evanescent region which appears in the inhomogeneous plasma in the region where the electron density is such that omega 02/ omega 2 approximately=1; omega is the frequency of the wave which generates and penetrates the plasma, omega 0 is the plasma frequency. The time dependences of the reflected power, spatial electron density distribution and transmitted power demonstrate the existence of the evanescent region and show the conditions for the free passage of the electromagnetic wave through this region. The experimental results are in a good qualitative agreement with the theory.