skip to main content

DOE PAGESDOE PAGES

Title: Novel analysis technique for measuring edge density fluctuation profiles with reflectometry in the Large Helical Device

A new method for measuring density fluctuation profiles near the edge of plasmas in the Large Helical Device (LHD) has been developed utilizing reflectometry combined with pellet-induced fast density scans. Reflectometer cutoff location was calculated by proportionally scaling the cutoff location calculated with fast far infrared laser interferometer (FIR) density profiles to match the slower time resolution results of the ray-tracing code LHD-GAUSS. Plasma velocity profile peaks generated with this reflectometer mapping were checked against velocity measurements made with charge exchange spectroscopy (CXS) and were found to agree within experimental uncertainty once diagnostic differences were accounted for. Measured density fluctuation profiles were found to peak strongly near the edge of the plasma, as is the case in most tokamaks. These measurements can be used in the future to inform inversion methods of phase contrast imaging (PCI) measurements. This result was confirmed with both a fixed frequency reflectometer and calibrated data from a multi-frequency comb reflectometer, and this method was applied successfully to a series of discharges. The full width at half maximum of the turbulence layer near the edge of the plasma was found to be only 1.5–3 cm on a series of LHD discharges, less than 5% of themore » normalized minor radius.« less
Authors:
ORCiD logo [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ; ORCiD logo [2] ;  [2] ;  [2] ;  [3]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  2. National Inst. for Fusion Science, Toki, Gifu (Japan)
  3. Australian National Univ., Canberra, ACT (Australia). Plasma Research Lab.
Publication Date:
Grant/Contract Number:
SC0006419
Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 88; Journal Issue: 7; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 47 OTHER INSTRUMENTATION
OSTI Identifier:
1474379
Alternate Identifier(s):
OSTI ID: 1371794