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Diagnostic development for parallel wave-number measurement of lower hybrid waves in EAST

Journal Article · · Review of Scientific Instruments
DOI:https://doi.org/10.1063/1.5144673· OSTI ID:1681201
 [1];  [2];  [2];  [3];  [3];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [4];  [5]
  1. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics; Univ. of Science and Technology of China, Hefei (China); OSTI
  2. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  4. Shenzhen Univ. (China). College of Optoelectronic Engineering
  5. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics; Univ. of Science and Technology of China, Hefei (China)
+ Show Author Affiliations
In this study, an eight-channel magnetic probe diagnostic system has been designed and installed adjacent to the 4.6 GHz lower hybrid (LH) grill antenna in the low-field side of the Experimental Advanced Superconducting Tokamak (EAST) in order to study the n∥ evolution of LH waves in the first pass from the launcher to the core plasma. The magnetic probes are separated by 6.6 mm, which allows measurement of the dominant parallel refractive index n∥ up to n∥ = 5 for 4.6 GHz LH waves. The magnetic probes are designed to be sensitive to the magnetic field component perpendicular to the background magnetic field with a slit on the casing that encloses the probe. The intermediate frequency stage, which consists of two mixing stages, down-coverts the frequency of the measured wave signals at 4.6 GHz to 20 MHz. A bench test demonstrates the phase stability of the magnetic probe diagnostic system. By evaluating the phase variation of the measured signals along the background magnetic field, the dominant n∥ of the LH wave in the scrape-off layer has been deduced during the 2019 experimental campaign. In the low density plasma, the measured dominant n∥ of the LH waves is about 2.1, corresponding to the main peak 2.04 of the launched n∥ spectrum. n∥ deduced by the least-squares linear fit method remains near this value in the low density plasma with a high spatial correlation magnitude of 0.9. With an eight-channel probe system, a wave-number spectrum has also been deduced, which has a peak near to the measured dominant n∥.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
Chinese Academy of Sciences; National Key Research and Development Program of China; National Magnetic Confinement Fusion Science Program of China; National Natural Science Foundation of China (NNSFC); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
SC0010492
OSTI ID:
1681201
Journal Information:
Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 7 Vol. 91; ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

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