Observation of Localized Electron Cyclotron Resonance Heating in a Magnetic Mirror

A right-hand circularly polarized (RHCP) electron cyclotron wave is launched along the axis of a steady-state magnetically confined plasma column. Detailed measurements of the spatial variation of electron temperature, density, plasma potential, and wave amplitude about the resonance zone are presented. In particular, data are presented where the temperature increase due to electron cyclotron resonance heating (ECRH) is strongly localized near the resonance position. A numerical wave heating model has been developed for electrons in a magnetic mirror and is found to be in qualitative agreement with observations.     

Electron Cyclotron Resonance Heating (ECRH) of a Spheromak Plasma

ECRH calculations are carried out for the MS Spheromak (Bto = 20-25 kG, ne ? 1014 cm-3) under the assumption of a straight-line ray path. These preliminary calculations indicate that for "end-on" illumination of the Spheromak plasma by an extraordinary wave at the second harmonic of the cyclotron frequency, almost complete single-pass absorption is achieved even when electron temperature is low (? 100 eV). The use of gyrotrons currently under development would make an early experimental demonstration possible.     

Features of Wave Propagation in an Inhomogeneous Plasma near the Electron Cyclotron Resonance

JETP Letters - Features of the propagation of electromagnetic waves in an inhomogeneous plasma at frequencies close to the electron-cyclotron resonance have been studied experimentally. It has been...     

Efficiency Enhancement of Coaxial-Cavity Electron Cyclotron Resonance Maser by Tapering Guide Magnetic Field

A coaxial-cavity cyclotron resonance maser (CRM) oscillator with tapered guide magnetic field is proposed. It is shown that the transmission quality can be improved by tapering the guide magnetic field. Simulation indicates that the efficiency of a millimeter-wave gyrotron oscillator may be reached up to 38.7% by optimizing the tapered magnetic field.     

Forming-Free Memristors Based on Hafnium Oxide Processed in Electron Cyclotron Resonance Hydrogen Plasma

JETP Letters - It is shown that the treatment of stoichiometric HfO2, which is synthesized by atomic layer deposition, in electron cyclotron resonance hydrogen plasma leads to a significant...     

Atomic and Electronic Structure of SiOx Films Obtained with Hydrogen Electron Cyclotron Resonance Plasma

Journal of Experimental and Theoretical Physics - The silicon oxide thin films obtained by thermal SiO2 treatment in hydrogen electron cyclotron resonance plasma at various exposure times are...     

Time Evolution of High-Energy Bremsstrahlung and Argon Ion Production in Electron Cyclotron Resonance Ion-Source Plasma

Bremsstrahlung radiation measurement is one of the most commonly used plasma-diagnostics methods. Most of the bremsstrahlung measurements with electron cyclotron resonance ion sources (ECRISs) have been performed in continuous-operation mode yielding information only on the steady-state bremsstrahlung emission. This paper describes results of bremsstrahlung and argon ion-current measurements with the JYFL 14-GHz ECRIS operated in a pulsed mode. The bremsstrahlung radiation was studied as a function of neutral-gas pressure and radio frequency power. The timescale of ECRIS bremsstrahlung production is compared to ion-production timescale for different charge states of argon for the first time. It was observed, for example, that the ion currents of different charge states reach the steady state before the bremsstrahlung emission rate saturates.      

Electron Acceleration by the E0n Wave in a Circular Waveguide in the Cyclotron Resonance Mode

Technical Physics - A method for acceleration of electrons in a smooth cylindrical waveguide in the presence of the magnetic field of a solenoid is proposed. Electrons move in the waveguide along a...     

Gyrokinetics of Coaxial-Cavity Electron Cyclotron Maser

Based on the gyrokinetics of free-electron masers, the energy-transfer rate and starting current are derived for a coaxial-cavity electron cyclotron maser (gyrotron oscillator) with the misalignment of the inner-rod axis to the outer-cavity axis taken into account. The effect of the finite cavity length is included in the derivation. The stable term of the instability which results from the contribution of the guiding-center distribution is of significance, although it is usually neglected in a cylindrical-cavity gyrotron. It is found that the structure misalignment has more serious influence on the performance of the coaxial cavity gyrotron than the beam misalignment.     

X-Ray Measurements during Whistler-Mode Electron Cyclotron Resonance Plasma Startup and Heating in an Axisymmetric Magnetic Mirror

New measurements and analyses of whistler-mode electron cyclotron resonant heating (ECRH) startup and heating in an axisymmetric magnetic mirror are presented. Experimental studies of startup are presented which include the effects of initial neutral gas pressure on density and energy buildup rates, the effects of electron-beam-generated seed plasma on startup times, and a possible density threshold for the absolute whistler instability. Results of two types of analyses are presented. The first is a Fokker-Planck finite-element simulation the principal result of which is the prediction of the creation of a sloshing electron velocity distribution in the first 10 ?s after microwave power is applied. The second simulation uses rate equations to predict buildup, with rate coefficients based on a model sloshing-electron distribution function. Both results are consistent with experimental observations. Measurements of X-ray emission provided information about plasma transport, the sloshing electron spatial distribution, and the hot-electron average energy. The foil ratio technique gave average energies of 1-3 keV during whistler-mode ECRH, in agreement with afterglow measurements of hot electron decay. Possible applications of whistler-mode ECRH plasma production and heating are for plasma soft X-ray sources and plasma potential modification in tandem mirror machines.     

Low-Threshold Parametric Excitation of Electron Plasma Waves Localized in the Edge Transport Barrier of a Tokamak during Electron Cyclotron Resonance Heating of a Plasma

JETP Letters - The possibility of the localization of longitudinal waves in the intermediate frequency range in the edge transport barrier of a toroidal nuclear fusion facility is discovered. It is...     

Radiation Spectrum of an Electron Cyclotron Maser

We consider generation of electromagnetic radiation at the electron cyclotron harmonics by energetic-electron beams having the mean momentum parallel, transverse, or oblique to the external magnetic field. This process is most efficient if the characteristic transverse momentum is sufficiently large. The radiation spectrum of the beam moving exactly along the magnetic field is closest to the equidistant one. The angle between the direction of the maximum emission and the magnetic field varies from 70^° for the field-aligned beam to 90^° for the beam whose characteristic momentum is transverse to the magnetic field. In fairly strong magnetic fields, i.e., for _Be >_pe, where _Be and _pe are the electron cyclotron and plasma frequencies, respectively, the radiation is maximum at low cyclotron harmonics and the second harmonic dominates. In the weaker fields (_Be < _pe), higher harmonics, up to fifth or sixth, are generated. Both wave modes are generated, but generation of the ordinary waves is far less efficient than that of the extraordinary waves under the same conditions.     

Effect of F- and CH-Doped on Dielectric Properties of SiCOH Films Deposited by Decamethylcyclopentasiloxane Electron Cyclotron Resonance Plasma

We investigate the effect of CH-doped and F-doped on dielectric properties of SiCOH films deposited by de- camethylcyclopentasiloxane （DMCPS） electron cyclotron resonance plasma. The dielectric constant k is closely related to the configurations of films. For the films deposited only using DMCPS, the minimum k is as low as 2.88. By adding CH4 in the precursor, the k value can be reduced to 2.45 due to the film density decreasing by incorporating large size CHx groups. By adding CHF3 in the precursor, the k value can also be reduced to 2.48 due to the incorporation of the weak-polarization F atom. Thus the dielectric constant for SiCOH films depends on not only the film density but also the polarization of atoms. By increasing the film density or by reducing the polarization of atoms under the condition of a lower film density, the low dielectric constant SiCOH films can be obtained.     

On the Possibility of Strong Anomalous Absorption of Microwaves in Experiments on Electron Cyclotron Plasma Heating at the Second Resonance Harmonic

JETP Letters - It has been shown that more than two thirds of the pumping power can be transmitted to the upper hybrid waves localized near the local maximum of the plasma density as a result of...     

Experimental Examination of Gyrokinetics of Electron Cyclotron Maser

In this paper the linear and quasi-linear kinetic theories of the electron cyclotron maser are introduced and experimantal examination is made. It is indicated that the transverse momentum spread of the electron beam has critical value; as it grows upto the critical value in the process of the beam-wave interaction, the electron cyclotron maser runs to saturation. Comparison shows good agreement between the theories and a typical experiment.     

Electron Cyclotron Heating Experiments in Tokamaks and Stellarators

This paper reviews the application of high-frequency microwave radiation to plasma heating near the electron cyclotron frequency in tokamaks and stellarators. Successful plasma heating by microwave power has been demonstrated in numerous experiments. Predicted future technological developments and current theoretical understanding suggest that a vigorous program in plasma heating will continue to yield promising results.     

Mechanical Analysis and Measurements of a Multicomponent NbTi/Cu Superconducting Magnets Structure for the Fully Superconducting Electron Cyclotron Resonance Ion Source

A fully superconducting electron cyclotron resonance(ECR) ion source(SECRAL Ⅱ) is currently being built in the Institute of Modern Physics,Chinese Academy of Sciences.Its key components are three superconducting solenoids(Nb-Ti/Cu) and six superconducting sextupoles(Nb-Ti/Cu).Different from the conventional superconducting ECR magnetic structure,the SECRAL Ⅱ includes three superconducting solenoid coils that are located inside the superconducting sextupoles.The SECRAL Ⅱ can significantly reduce the interaction forces between the sextupole and the solenoids,and the magnets can also be more compact in size.For this multi-component SECRAL Ⅱ generating its self Held of ~8T and being often exposed to the high self Geld,the mechanical analysis has become the main issue to keep their stress at 200 MPa on coils.The analytical and experimental results in mechanics are presented in the SECRAL Ⅱ structure.To improve the accuracy and efficiency of analysis,according to the composite rule of micromechanics,the equivalent uniform windings are used to simuiate the epoxy-impregnated Nb-Ti/Cu coils.In addition,using low temperature strain gauges and a wireless fast strain acquisition system,a fundamentai experiment on the strains developments of a sextupole is reported.Finally,based on our analysis,the stresses and deformations for its assembly of each SECRAL Ⅱ coil will be further optimized.     

Wave Trajectory and Electron Cyclotron Heating in Tokamak Plasmas

Wave trajectories in high density tokamak plasmas are studied numerically. Results show that the ordinary wave injected at an appropriate incident angle can propagate into the dense plasmas and is mode-converted to the extraordinary wave at the plasma cutoff, is further converted to the electron Bernstein wave during passing a loop or a folded curve near the upper hybrid resonance (UHR) layer, and is cyclotron damped away, resulting in local electron heating before arriving at the cyclotron resonance layer. Similar trajectory and damping are obtained when a microwave in a form of extraordinary wave is injected quasi-perpendicularly in the direction of decreasing toroidal field.