Abstract
The scattering of lower hybrid (LH) waves due to scrape-off layer filaments is investigated. It is revealed that scattering can account for the LH spectral gap without any ad hoc modification to the wave-spectrum. This is shown using a multiscale simulation approach which allows, for the first time, the inclusion of full-wave scattering physics in ray-tracing/Fokker-Planck calculations. In this approach, full-wave scattering probabilities are calculated for a wave interacting with a statistical ensemble of filaments. These probabilities are coupled to ray-tracing equations using radiative transfer theory. This allows the modeling of scattering along the entire ray-trajectory, which can be important in the multi-pass regime. Simulations are conducted for LH current drive (LHCD) in Alcator C-Mod, resulting in excellent agreement with experimental current and hard x-ray profiles. A region in filament parameter space is identified in which the impact of scattering on LHCD is saturated. Such a state coincides with experimental LHCD measurements, suggesting saturation indeed occurs in C-Mod, and therefore the exact statistical properties of the filaments are not important.
| Original language | English |
|---|---|
| Article number | 016029 |
| Number of pages | 15 |
| Journal | Nuclear Fusion |
| Volume | 63 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 16 Dec 2022 |
Bibliographical note
Funding Information:This work was supported by US DoE under Contract Numbers: DE-SC0018090 supporting the RF-SciDAC 4 project, DE-SC0014264 supporting PSFC MFE projects, and DE-FC02-04ER54698 supporting DIII-D projects. The GENRAY/CQL3D simulations presented in this paper were performed on the MIT-PSFC partition of the Engaging cluster at the MGHPCC facility ( www.mghpcc.org ) which was funded by DoE Grant Number DE-FG02-91-ER54109.
Publisher Copyright:
© 2022 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd.
Keywords
- Alcator C-Mod
- filament
- LHCD
- turbulence