Heating by an electron Bernstein wave in a spherical tokamak plasma via mode conversion

The first successful high power heating of a high dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited by mode conversion (MC) of an mode cyclotron wave injected from the low magnetic field side of the TST-2 spherical tokamak. Evidence of electron heating was observed as increases in the stored energy and soft x-ray emission. The increased emission was concentrated in the plasma core region. A heating efficiency of over 50% was achieved, when the density gradient in the MC region was sufficiently steep.     

Excitation of an optical satellite by thermal electron oscillations of a lithium plasma

An optical satellite excited by thermal electron plasma oscillations is observed near the 2P–3P forbidden line of a dense lithium plasma. The observations are compared with predictions of second order time-dependent Stark theory.     

Current drive by an HF electromagnetic wave in a magnetized plasma

The problem of current drive by an HF wave is analyzed in a one-particle model of a magnetized plasma. A general expression for the current drive is derived by an averaging method in the nonrelativistic case, in second order in the expansion parameter. The presence of a constant and strong magnetic field, the presence of a constant electric field, and the dynamic friction effect are all taken into account. For a monochromatic wave with an amplitude which varies slowly in time and space, expressions for the current drive are derived in closed form. The mechanism for the current drive is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 87–91, March, 1989.     

Excitation of an upper hybrid wave by two intense laser beams and particle acceleration

This Letter presents an investigation of the excitation of an upper hybrid wave (UHW) by cross focusing of two intense laser beams in a collisionless hot magnetoplasma, when relativistic and ponderomotive nonlinearities are operative. The electric vectors of the two beams are polarized along uniform static magnetic field and the beams propagate perpendicular to the static magnetic field. Analytical expressions for the beam width of the laser beams, electric vector and power of the excited UHW and energy gain have been obtained. The UHW generation at the difference frequency and particle acceleration has also been studied. The nonlinear coupling between intense laser beams and UHW is so strong that UHW gets excited and a large fraction of the laser beam energy gets transferred to UHW and this UHW accelerates electrons. It has been shown that the presence of a magnetic field affects significantly the power of the UHW and energy gain by the electron in the presence of the UHW.     

Excitation of electron cyclotron harmonic waves due to helical electron beams in a plasma

Instabilities of electron cyclotron harmonic waves due to the anisotropy of the velocity distribution of electrons which was produced by the injection of the electron beam perpendicular to the magnetic field have been observed.     

Excitation of intrinsic defects in ionic crystals by high-power optical and electron beams

The efficiency of excitation and recharging of intrinsic defects by hot charge carriers has been investigated in ionic crystals acted on by high-power optical and electron beams. The interaction cross sections of hot electrons and holes with intrinsic lattice sites and F _n -type defects (n=1,2) are shown to be commensurate. It is also shown that the potential of the intracrystalline field in the vicinity of F and F ₂ centers is nearly regular. Fiz. Tverd. Tela (St. Petersburg) 40, 1030–1035 (June 1998)     

Excitation of surface plasma waves over metallic surfaces by lasersand electron beams

A laser incident on a metal film (deposited on a glass substrate) from the glass side at a specific angle of incidence, excites a surface plasma wave (SPW) at the metal-free space interface. The ratio of the SPW field to the laser field increases with the laser spot size b attaining a value much greater than one at b>exp(2wα/c) where a is the film thickness and ω is the laser frequency. The SPW (ω, k_z,) can also he excited by a relativistic electron beam, propagating parallel to the interface in the free space region, via Cerenkov interaction when beam energy ϵb=(|ϵ|-1)mc² where ϵ is the effective metal permittivity, and mc² is the electron rest mass energy. When the surface has a ripple of wave number k₀, the SPW (ω, k_zz) can be excited at lower beam energy via sideband coupling, ω=(k_zz +k₀)v_b where v_bzˆ is the beam velocity. In both cases, however, the positioning of the beam in the close proximity of the interface is required. The scheme is useful for the generation of wavelengths longer than 1 μm     

Controlled optimization of mode conversion from electron Bernstein waves to extraordinary mode in magnetized plasma

In the CDX-U spherical torus, agreement between radiation temperature and Thomson scattering electron temperature profiles indicates approximately 100% conversion of thermally emitted electron Bernstein waves to the X mode. This has been achieved by controlling the electron density scale length (L(n)) in the conversion region with a local limiter outside the last closed flux surface, shortening L(n) to the theoretically required value for optimal conversion. From symmetry of the conversion process, prospects for efficient coupling in heating and current drive scenarios are strongly supported.     

New acceleration mechanism of electrons by an electromagnetic wave in a weakly magnetized plasma

Acceleration of electrons by an electromagnetic wave has been observed in a weakly magnetized (ω_ce/ω₀ ? 10^?2) inhomogeneous plasma. This acceleration is interpreted as a V_p × B₀ acceleration, which is a new concept for heating or accelerating electrons very efficiently to high energy.     

Self-focusing of helicon beams in a magnetized solid-state plasma

It is demonstrated that narrow helicon beams with zero diffraction convergence can propagate within a magnetized solid-state (metal or semiconductor) plasma. The phase velocity and attenuation of such beams are significantly lower than in the case of a plane helicon.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 23–25, February, 1985.     

Excitation of microwave by an annular electron beam in a plasma-filled dielectric lined waveguide

An axial relativistic electron beam passing through a slow wave structure is unstable to an electromagnetic perturbation whose phase velocity equals the velocity of the beam. This phenomenon of Cherenkov emission is the basis of all traveling wave tubes. In this paper an excitation of Cherenkov radiation by a thin annular relativistic electron beam in a plasma-filled dielectric-lined waveguide is analysed by use of the self-consistent linear theory. The effect of the thin annular electron beam on the beam-wave interaction is completely described by a jump condition. The dispersion equation and the simultaneous condition of the beam-wave interaction are derived. Finally, the growth rate of the wave is obtained, and the effect of the background plasma density and the electron beam radius on the growth rate of the wave are presented.This work is supported by National Natural Science Foundation of China.     

Excitation of ion cyclotron waves at the difference frequency of two microwave beams in a semiconductor

This paper presents an investigation of the resonant excitation of the electrostatic ion cyclotron wave at the difference frequency of two microwave beams propagating in a magnetoactive solid state plasma, viz. n InSb. The resonant excitation of the electrostatic ion cyclotron wave occurs when the difference frequency of the two microwave beams and the difference of their propagation vectors satisfy the dispersion relation corresponding to the electrostatic ion cyclotron wave. For typical plasma parameters of n InSb and microwave beams of power densities 1 MW cm^?2, the power density of the excited ion cyclotron wave is 0.40 kW cm^?2 when external magnetic field is $\text{1.46 kG (}\text{Ω}{}_{\mathrm{c}}\text{ω}\text{) = 0.1)}$. The power density of the excited ion cyclotron wave increases with the magnetic field. This study may provide new means for the characterisation and diagnostic of semiconductors.     

Excitation of ion acoustic waves at the difference frequency of two microwave beams in a semiconductor

This letter presents an investigation of the resonant excitation of the electrostatic ion acoustic wave at the difference frequency of two microwave beams in a semiconductor, viz., n-type InSb. The ponderomotive force at the difference frequency on electrons drives the ion acoustic wave at the difference frequency. The resonance conditions are satisfied over a wide range of semiconductor parameters. For typical plasma parameters of n-InSb and microwave beams of power densities 1 MW cm^?2, the power density of the excited ion acoustic wave is ≈ 1.76 kW cm^?2.     

Excitation of nonlinear surface modes by wave beams

We consider the interaction of 2-D and 3-D wave beams with an interface between linear and nonlinear media. The range of parameters of Gaussian beams exciting nonlinear surface waves (NSW) with high efficiency is analytically determined. Different regimes of NSW excitation are numerically studied. Analytical data are in good agreement with numerical results.Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 246–255, March–April, 1995.     

Excitation of plasma waves by an externally applied electromagnetic wave to a nonuniform classical plasma

Radiation-driven plasma wave equations (RWE's) are derived from the basic dynamical plasma equations through restaining the external radiation source terms and significant nonlinear terms under the simplified assumptions used by Zakharov [1]. Excitation processes of the transverse plasma waves, Langmuir waves by an externally applied electromagnetic wave to a nonuniform unmagnetized plasma are investigated by means of rough numerical simulations based on RWE's. The results show that the amplitude of the transverse plasma waves is sensitive to their effective damping rate and that the radiation-induced density profile modification looks like a step, which are in qualitative agreement with analytical results.Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 959–987, August, 1996.One of the authors (Li) wishes to thank V.L. Ginzburg, E. Mjølhus, B. Thidé, N.S. Erokhin, J.Y. Liu, J.W. Lee, T.D. Carozzi, and J. Bergman for helpful oral discussions on this topic. Li also wants to thank M. Matsuoka for the kind hospitality during his year-long stay at RIKEN, where this work was completed.     

Electromagnetic wave scattering from a magnetized plasma column including a thin annular magnetized relativistic rotating electron beam (TAMRREB)

The problem of the scattering of electromagnetic waves from a magnetized plasma column including a thin annular magnetized relativistic rotating electron beam is discussed theoretically. The backscattering cross-section and scattering pattern are presented for a transverse electric (TE) polarization. An investigation on the effects of system parameters on the backscattering cross-section and scattering pattern is done and the corresponding polarized charge density plots are presented.