A generalized plasma dispersion function for electron damping in tokamak plasmas

Journal Article · Fri Oct 14 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4964766· OSTI ID:1341560

Berry, L. A. ^[1]; Jaeger, E. F. ^[1]; Phillips, C. K. ^[2]; Lau, C. H. ^[3]; Bertelli, N. ^[2]; Green, D. L. ^[3]

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1. XCEL Engineering, Oak Ridge, TN (United States)
2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Radio frequency wave propagation in finite temperature, magnetized plasmas exhibits a wide range of physics phenomena. The plasma response is nonlocal in space and time, and numerous modes are possible with the potential for mode conversions and transformations. Additionally, diffraction effects are important due to finite wavelength and finite-size wave launchers. Multidimensional simulations are required to describe these phenomena, but even with this complexity, the fundamental plasma response is assumed to be the uniform plasma response with the assumption that the local plasma current for a Fourier mode can be described by the Stix conductivity. But, for plasmas with non-uniform magnetic fields, the wave vector itself is nonlocal. When resolved into components perpendicular (k ) and parallel (k ||) to the magnetic field, locality of the parallel component can easily be violated when the wavelength is large. The impact of this inconsistency is that estimates of the wave damping can be incorrect (typically low) due to unresolved resonances. For the case of ion cyclotron damping, this issue has already been addressed by including the effect of parallel magnetic field gradients. In this case, a modified plasma response (Z function) allows resonance broadening even when k || = 0, and this improves the convergence and accuracy of wave simulations. In our paper, we extend this formalism to include electron damping and find improved convergence and accuracy for parameters where electron damping is dominant, such as high harmonic fast wave heating in the NSTX-U tokamak, and helicon wave launch for off-axis current drive in the DIII-D tokamak.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC05-00OR22725; AC02-05CH11231
• OSTI ID: 1341560
• Journal Information: Physics of Plasmas, Vol. 23, Issue 10; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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