Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak
Name
Den Whyte Faust - Phys of Plas 23 5 2016.pdf
Size
2.98 MB
Format
Adobe PDF
Checksum (MD5)
7eb6741f6fbdf2eca2fb72836a1b89ed
Author(s)
Faust, Ian Charles
Brunner, Daniel Frederic
Labombard, Brian
Terry, James L
Whyte, Dennis G
Baek, Seung Gyou
Edlund, Eric Matthias
Hubbard, Amanda E
Hughes Jr, Jerry
Kuang, Adam QingYang
Date Issued
May 2016
Journal
Physics of Plasmas
Publisher
American Institute of Physics (AIP)
Citation
Faust, I. C., D. Brunner, B. LaBombard, R. R. Parker, J. L. Terry, D. G. Whyte, S. G. Baek, et al. “Lower Hybrid Wave Edge Power Loss Quantification on the Alcator C-Mod Tokamak.” Physics of Plasmas 23, no. 5 (May 2016): 056115.
Version
Author's final manuscript
Abstract
For the first time, the power deposition of lower hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Lyα ionization camera, the toroidal, poloidal, and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt (t<[Greel letter tau lower case][subscript E upper case]) response of the scrape-off-layer (SOL) plasma to Lower Hybrid Radiofrequency (LHRF) power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high density previously observed on Alcator C-Mod, and displaying characteristics that contrast with the local RF edge absorption seen on other tokamaks. Measurements of ionization in the active divertor show dramatic changes due to LHRF power, implying that divertor region can be a key for the LHRF edge power deposition physics. These observations support the existence of a loss mechanism near the edge for LHRF at high density (n[subscript e]>1.0×10[superscript 20] (m[superscript −3])). Results will be shown addressing the distribution of power within the SOL, including the toroidal symmetry and radial distribution. These characteristics are important for deducing the cause of the reduced LHCD efficiency at high density and motivate the tailoring of wave propagation to minimize SOL interaction, for example, through the use of high-field-side launch.
MIT Department
Massachusetts Institute of Technology. Department of Biological Engineering
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Department of Mathematics
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1063/1.4951736
