Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging
Abstract
An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contain information on the magnetic field vector B at the cutoff layer. By probing the plasma with different wave frequencies it provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. We proposed an reflectometric approach in order to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit Electron Bernstein Waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Furthermore, frequencies above the edge electron-cyclotron frequency (f >28 GHz here) would be preferable for the experiment, becausemore »
- Authors:
-
- General Atomics, San Diego, CA (United States)
- Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Applied Mathematics
- Publication Date:
- Research Org.:
- General Atomics, San Diego, CA (United States)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1371890
- Grant/Contract Number:
- FC02-04ER54698; FG02-95ER54309
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Review of Scientific Instruments
- Additional Journal Information:
- Journal Volume: 87; Journal Issue: 11; Related Information: O. Meneghini and F.A. Volpe, "Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging", Rev. Sci. Instr. 87, 11E120 (2016); Journal ID: ISSN 0034-6748
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
Citation Formats
Meneghini, Orso, and Volpe, Francesco A. Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging. United States: N. p., 2016.
Web. doi:10.1063/1.4960538.
Meneghini, Orso, & Volpe, Francesco A. Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging. United States. https://doi.org/10.1063/1.4960538
Meneghini, Orso, and Volpe, Francesco A. Fri .
"Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging". United States. https://doi.org/10.1063/1.4960538. https://www.osti.gov/servlets/purl/1371890.
@article{osti_1371890,
title = {Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging},
author = {Meneghini, Orso and Volpe, Francesco A.},
abstractNote = {An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contain information on the magnetic field vector B at the cutoff layer. By probing the plasma with different wave frequencies it provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. We proposed an reflectometric approach in order to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit Electron Bernstein Waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Furthermore, frequencies above the edge electron-cyclotron frequency (f >28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.},
doi = {10.1063/1.4960538},
journal = {Review of Scientific Instruments},
number = 11,
volume = 87,
place = {United States},
year = {Fri Aug 19 00:00:00 EDT 2016},
month = {Fri Aug 19 00:00:00 EDT 2016}
}
Web of Science
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