Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak
Name
PhysRevLett.121.055001.pdf
Description
Published version
Size
636.5 KB
Format
Adobe PDF
Checksum (MD5)
54ee138732cfe025c3bfb050117a2cd8
Author(s)
Baek, SG
Wallace, GM
Bonoli, PT
Brunner, D
Faust, IC
Hubbard, AE
Hughes, JW
LaBombard, B
Parker, RR
Porkolab, M
Date Issued
2018
Journal
Physical Review Letters
Publisher
American Physical Society (APS)
Version
Final published version
Abstract
© 2018 American Physical Society. Efficient lower hybrid current drive (LHCD) is demonstrated at densities up to ne≈1.5×1020 m-3 in diverted plasmas on the Alcator C-Mod tokamak by operating at increased plasma current - and therefore reduced Greenwald density fraction. This density exceeds the nominal "LH density limit" at ne≈1.0×1020 m-3 reported previously, above which an anomalous loss of current drive efficiency was observed. The recovery of current drive efficiency to a level consistent with engineering scalings is correlated with a reduction in density shoulders and turbulence levels in the far scrape-off layer. Concurrently, rf wave interaction with the edge and/or scrape-off-layer plasma is reduced, as indicated by a minimal broadening of the wave frequency spectrum measured at the plasma edge. These results have important implications for sustaining steady-state tokamak operation and indicate a pathway forward for implementing efficient LHCD in a reactor.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
https://doi.org/10.1103/PHYSREVLETT.121.055001
