Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power
[1];
[2];
[3];
[4]
- Univ. of California, San Diego, CA (United States). Dept. of Mechanical and Aerospace Engineering; Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Max Planck Inst. for Plasma Physics, Garching (Germany)
- Univ. of York (United Kingdom). York Plasma Inst., Dept. of Physics
- Univ. of Stuttgart, Stuttgart (Germany)
- Tokamak Energy Ltd, Milton Park, Abingdon (United Kingdom)
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. Finally, we calculate the instability rate analytically and find this basic theory to be in reasonable agreement with our simulation results.
- Research Organization:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- FG02-04ER54742; AC02-09CH11466; EP/G054940; EP/G055165; EP/G056803
- OSTI ID:
- 1432666
- Journal Information:
- Nuclear Fusion, Vol. 57, Issue 11; ISSN 0029-5515
- Publisher:
- IOP ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas
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journal | June 2019 |
Mode-conversion of the extraordinary wave at the upper hybrid resonance in the presence of small-amplitude density fluctuations
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journal | November 2018 |
Particle-in-cell simulations of parametric decay instabilities at the upper hybrid layer of fusion plasmas to determine their primary threshold
|
journal | November 2019 |
| Mode-conversion of the extraordinary wave at the upper hybrid resonance in the presence of small-amplitude density fluctuations | text | January 2018 |
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