Author: F. N. SkiffPublisher:
ISBN:
Category :
Languages : en
Pages : 12
Book Description
Harmonic Generation and Parametric Decay in the Ion Cyclotron Frequency Range
Author: F. N. SkiffHarmonic Generation and Parametric Decay in the Ion Cyclotron Frequency Range
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Harmonic generation and parametric decay are examined in a toroidal ACT-I plasma using electrostatic plate antennas. The harmonic generation, which is consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically. Resonant and nonresonant parametric decay of the second harmonic are observed and compared with uniform pump theory. Resonant decay of lower hybrid waves into lower hybrid waves and slow ion cyclotron waves is seen for the first time. Surprisingly, the decay processes are nonlinearly saturated, indicating absolute instability.
Energy Research Abstracts
Author: Nonlinear Decay Instability and Parametric Amplification of Cyclotron Harmonic Plasma Waves
Author: Miklos PorkolabPublisher:
ISBN:
Category : Cyclotron resonance
Languages : en
Pages : 30
Book Description
Experimental Studies of Multi-Species Pure Ion Plasmas
Author: Matthew AffolterPublisher:
ISBN:
Category :
Languages : en
Pages : 87
Book Description
Cyclotron modes are studied on rigid rotor, multi-species ion plasmas confined in a Penning-Malmberg trap. Collective effects and radial electric fields shift the cyclotron mode frequencies away from the "bare" cyclotron frequencies for each species s. These frequency shifts are measured on the distinct cyclotron modes (m = 0, 1, and 2) with sinusoidal azimuthal dependence. We find that the frequency shifts corroborate a simple theory expression in which collective effects enter only through the ExB rotation frequency and the species fraction, when the plasma is radially uniform. At ultra-low temperatures, these plasmas exhibit centrifugal separation by mass, and additional frequency shifts are observed in agreement with a more general theory. Additionally, quantitative measurements of the plasma heating from short resonant cyclotron bursts are found to be proportional to the species fraction. These cyclotron modes are used as a diagnostic tool to estimate the plasma composition, in order to investigate the damping of Langmuir waves due to inter-species collisions. Experiments and theory of this collisional inter-species drag damping are presented. This also provides the first experimental confirmation of recent theory predicting enhanced collisional slowing due to long-range collisions. Drag damping theory, proportional to the collisional slowing rate, is in quantitative agreement with the experimental results only when these long-range collisions are included, exceeding classical collision calculations by as much as an order of magnitude. At large wave amplitudes, Langmuir waves exhibit harmonic generation, non-linear frequency shifts, and a parametric decay instability, which are experimentally investigated. The parametric wave-wave coupling rates are in agreement with three-wave instability theory in the dispersion dominated oscillatory coupling regime, and in the phase-locked exponential decay regime. However, significant variations are observed near the decay threshold, including slow, oscillatory growth of the daughter wave. These experimental results have motivated wide-ranging theory and simulations, which provide both insights and puzzles.
Physics Briefs
Author: Effects of Ion Cyclotron Harmonic Damping on Current Drive in the Lower Hybrid Frequency Range
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
We investigate the ion cyclotron harmonic damping effects on slow and fast waves in the lower hybrid frequency range for tokamak reactor parameters. Inclusion of the higher order terms in the hot plasma dielectric tensor introduces ion cyclotron harmonic damping; these terms also contribute to the real part of the dispersion relation and affect the wave trajectories. However, wave absorption by 15 keV deuterium and tritium ions can be avoided by choosing the slow wave frequency above the lower hybrid frequency and the fast wave frequency below the lower hybrid frequency. But preliminary estimates show that energetic alpha particles tend to absorb both the slow and the fast waves. This absorption may become a serious obstacle for fusion-reactor current drive in the lower hybrid frequency range.
Nuclear Science Abstracts
Author: INIS Atomindeks
Author: Cyclotron Waves in Plasma
Author: D. G. LominadzePublisher: Elsevier
ISBN: 1483280780
Category : Science
Languages : en
Pages : 219
Book Description
Cyclotron Waves in Plasma is a four-chapter text that covers the basic physical concepts of the theory of cyclotron waves and cyclotron instabilities, brought about by the existence of steady or alternating plasma currents flowing perpendicular to the magnetic field. This book considers first a wide range of questions associated with the linear theory of cyclotron oscillations in equilibrium plasmas and in electron plasmas in metals and semiconductors. The next chapter deals with the parametric excitation of electron cyclotron oscillations in plasma in an alternating electric field. A chapter focuses on plasma turbulence, which results from the development of cyclotron instabilities. The last chapter discusses pertinent experimental data concerning cyclotron waves in plasma. The book is intended for specialists in plasma physics and a number of related fields, including the physics of the ionosphere, solar wind and, metals, as well as for students and teachers who are specializing in these subjects.