Arefiev, A. V., Dodin, I. Y., Köhn, A. et al. (4 more authors) (2017) Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power. Nuclear Fusion. ISSN 1741-4326
Abstract
Spherical tokamak plasmas are typically overdense and thus inaccessible to externally-injected microwaves in the electron cyclotron range. The electrostatic electron Bernstein wave (EBW), however, provides a method to access the plasma core for heating and diagnostic purposes. Understanding the details of the coupling process to electromagnetic waves is thus important both for the interpretation of microwave diagnostic data and for assessing the feasibility of EBW heating and current drive. While the coupling is reasonably well-understood in the linear regime, nonlinear physics arising from high input power has not been previously quantified. To tackle this problem, we have performed one- and two-dimensional fully kinetic particle-in-cell simulations of the two possible coupling mechanisms, namely X-B and O-X-B mode conversion. We find that the ion dynamics has a profound effect on the field structure in the nonlinear regime, as high amplitude short-scale oscillations of the longitudinal electric field are excited in the region below the high-density cut-off prior to the arrival of the EBW. We identify this effect as the instability of the X wave with respect to resonant scattering into an EBW and a lower-hybrid wave. We calculate the instability rate analytically and find this basic theory to be in reasonable agreement with our simulation results.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details. |
Keywords: | physics.plasm-ph |
Dates: |
|
Institution: | The University of York |
Academic Units: | The University of York > Faculty of Sciences (York) > Physics (York) |
Depositing User: | Pure (York) |
Date Deposited: | 11 Jul 2017 09:45 |
Last Modified: | 26 Feb 2025 00:04 |
Published Version: | https://doi.org/10.1088/1741-4326/aa7e43 |
Status: | Published |
Refereed: | Yes |
Identification Number: | 10.1088/1741-4326/aa7e43 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:111957 |
Downloads
Filename: 1612.07860v1
Description: pdf
Filename: Nuclear_Fusion_revised_2_full.pdf
Description: Nuclear_Fusion_revised_2_full
Filename: Arefiev_et_al_2017_Nucl._Fusion_10.1088_1741_4326_aa7e43.pdf
Description: Arefiev+et+al_2017_Nucl._Fusion_10.1088_1741-4326_aa7e43
Licence: CC-BY-NC-ND 2.5