Parametric decay instabilities driven by high power helicon waves in DIII-D
Name
070004_1_5.0163570.pdf
Description
Published version
Size
2.79 MB
Format
Adobe PDF
Checksum (MD5)
df56bbe9eaa10d538a464820326d856d
Author(s)
Porkolab, M
Pinsker, RI
DeGrandchamp, GH
Baek, SG
Compernolle, B Van
Denk, S
Petty, CC
Tang, SX
Thome, KE
Date Issued
August 18, 2023
Journal
AIP Conference Proceedings
Publisher
AIP Publishing
Citation
M. Porkolab, R. I. Pinsker, G. H. DeGrandchamp, S. G. Baek, B. Van Compernolle, S. Denk, C. C. Petty, S. X. Tang, K. E. Thome; Parametric decay instabilities driven by high power helicon waves in DIII-D. AIP Conf. Proc. 18 August 2023; 2984 (1): 070004.
Version
Final published version
Abstract
High power helicon waves (whistler or very high harmonic fast lower hybrid waves) at a frequency of 476 MHz are being tested for efficient off-axis current drive on DIII-D with the goal of demonstrating profile control in AT plasmas [1-4]. In agreement with earlier theoretical predictions, strong Parametric Decay Instability (PDI) has been observed at injected RF power levels in the range of 0.05-0.5 MW with corresponding electric fields of 10-30 kV/m [5,6]. The dominant driver of the PDI is the E×B and the polarization drift velocity which can drive ion cyclotron quasi-modes and lower hybrid (or IBW) sideband waves unstable [5,6]. Initial experimental results have been obtained with powers up to 0.3 MW showing evidence of strong PDI measured with high-frequency one-turn magnetic probes located at both the outboard and the inboard wall at frequencies set by the usual selection rules [7,8]. Here we review the appropriate analytic formulation to predict such instabilities and present numerical evaluation of frequencies and growth rates relevant to DIII-D plasma parameters. We also assess the convective thresholds for the PDIs, and compared them with experimental observations.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Terms of Use
Creative Commons Attribution
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1063/5.0163570
