Direct determination of ion wave fields in a hot magnetized and weakly collisional plasma

Abstract

Electrostatic ion cyclotron wave fields are determined in a magnetized and weakly collisional plasma. A phased-locked Laser Induced Fluorescence (LIF) diagnostic is used to directly measure the wave perturbed ion velocity distribution. Comparing these local LIF measurements with a theoretical model uniquely determines the wave parameters, such as the wave potential, the three-dimensional wave vector, and the effective wave damping. The self-consistent wave–particle interaction is modeled by Boltzmann–Poisson equations in the limit of weak collisions. The wave parameters determined from local measurements agree with those determined from spatial scans.

Parallel inhomogeneous flows in a thermally anisotropic plasma: The electrostatic ion-acoustic branch

“…Perturbed distribution functions as a function of individual velocity components can be directly compared to plasma observations by measuring the component of the Doppler shifted absorption profile of metastable ions that oscillate at the wave frequency. [27][28][29] Because of their potential for experimental identification of specific instabilities, the perturbed distribution functions derived for these calculations are reproduced here …”

“…Experiments performed in laboratory plasmas have demonstrated that electrostatic wave amplitudes and wavelengths ͑assuming a particular dispersion relationship to eliminate either k Ќ or k ʈ ) can be noninvasively measured by comparing laser induced fluorescence ͑LIF͒ 30 measurements of the perturbed distribution function to theoretical expressions. [27][28][29] For those experiments, the data were compared to theoretical expressions that included the effects of thermal anisotropy and parallel flow, but not shear in the parallel flow. However, this work has focused on the development of a more general theory for use in experiments with both parallel flow shear and thermal anisotropy.…”

“…͑6͒ reduces to the same expression obtained by previous groups. 28 The first order perturbed distribution function is a onedimensional ͑in velocity space͒ description of the velocity dependent interaction of each particle with the wave fields for times prior to the moment of measurement. Experiments performed in laboratory plasmas have demonstrated that electrostatic wave amplitudes and wavelengths ͑assuming a particular dispersion relationship to eliminate either k Ќ or k ʈ ) can be noninvasively measured by comparing laser induced fluorescence ͑LIF͒ 30 measurements of the perturbed distribution function to theoretical expressions.…”

Experimental Characterization of Plasma Heating with Beating Electrostatic Waves

“…This tool probes the velocity distribution of ions in the system and provides information both on the ion temperature as well as the dielectric response of the ions to propagating plasma modes. 31,32 The LIF technique is an inherently non-invasive diagnostic for examining ion temperature and wave properties. This is a significant advantage since the kinetic BEW effect can be perturbed by placing probes in the plasma.…”

Kinetic modes in a hot magnetized and weakly collisional plasma

“…1 Traditionally, experimental studies of waves in plasmas have involved measuring the perturbed fluid parameters. While this is useful in its own right, a measurement of the perturbed distribution function can provide both the fluid quantities ͑from an evaluation of the relevant moments͒, as well as other wave-particle effects that are not easily determined from a measurement of the fluid perturbations.…”