Resonance in Fast-Wave Amplitude in the Periphery of Cylindrical Plasmas and Application to Edge Losses of Wave Heating Power in Tokamaks

Dataset · Fri Jul 01 00:00:00 EDT 2016

DOI:https://doi.org/10.11578/1366752· OSTI ID:1366752

Perkins, R.J ^[1]; Hosea, J.C. ^[2]; Bertelli, N. ^[2]; Taylor, G. ^[2]; Wilson, J.R. ^[2]

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1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Princeton Plasma Physics Laboratory
2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Heating magnetically confined plasmas using waves in the ion-cyclotron range of frequencies typically requires coupling these waves over a steep density gradient. This process has produced an unexpected and deleterious phenomenon on the National Spherical Torus eXperiment (NSTX): a prompt loss of wave power along magnetic field lines in front of the antenna to the divertor. Understanding this loss may be key to achieving effective heating and expanding the operational space of NSTX-Upgrade. Here, we propose that a new type of mode, which conducts a significant fraction of the total wave power in the low-density peripheral plasma, is driving these losses. We demonstrate the existence of such modes, which are distinct from surface modes and coaxial modes, in a cylindrical cold-plasma model when a half wavelength structure fits into the region outside the core plasma. The latter condition generalizes the previous hypothesis regarding the occurence of the edge losses and may explain why full-wave simulations predict these losses in some cases but not others. If valid, this condition implies that outer gap control is a potential strategy for mitigating the losses in NSTX-Upgrade in addition to raising the magnetic field or influencing the edge density.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
• DOE Contract Number: AC02-09CH11466
• OSTI ID: 1366752
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Magnetically confined fusion Wave heating Cold plasma waves