Homogenization theory for the effective permittivity of a turbulent tokamak plasma in the scrape-off layer

Journal Article · Thu Sep 06 00:00:00 EDT 2018 · Journal of Plasma Physics

DOI:https://doi.org/10.1017/s0022377818000922· OSTI ID:1609001

Bairaktaris, F. ^[1]; Hizanidis, K. ^[1]; Ram, A. K. ^[2]; Papagiannis, P. ^[1]; Tsironis, C. ^[1]; Kominis, Y. ^[1]; Glytsis, E. ^[1]; Chellai, O. ^[3]; Alberti, S. ^[3]; Furno, I. ^[3]

---

1. National Technical University of Athens (Greece)
2. Massachusetts Institute of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
3. Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)

We report that there has been a growing interest, over the past few years, on understanding the effect on radio frequency waves due to turbulence in the scrape-off layer of tokamak plasmas. While the far scrape-off layer density width is of the order of centimetres in contemporary tokamaks, in ITER (International Thermonuclear Experimental Reactor), and in future fusion reactors, the corresponding width will be of the order of tens of centimetres. As such, this could impact the spectral properties of the waves and, consequently, the transport of wave energy and momentum to the core plasma. The turbulence in the scrape-off layer spans a broad range of spatial scales and includes blobs and filaments that are elongated along the magnetic field lines. The propagation of radio frequency waves through this tenuous plasma is given by Maxwell’s equations. The characteristic properties of the plasma appear as a permittivity tensor in the expression for the current in Ampere’s equation. This paper develops a formalism for expressing the permittivity of a turbulent plasma using the homogenization technique. This technique has been extensively used to express the dielectric properties of composite materials that are spatially inhomogeneous, for example, due to the presence of micro-structures. In a similar vein, the turbulent plasma in the scrape-off layer is spatially inhomogeneous and can be considered as a composite material in which the micro-structures are filaments and blobs. The classical homogenization technique is not appropriate for the magnetized plasma in the scrape-off layer, as the radio frequency waves span a broad range of wavelengths and frequencies – from tens of megahertz to hundreds of gigahertz. The formalism in this paper makes use of the Fourier space components of the electric and magnetic fields of the radio frequency waves for the scattered fields and fields inside the filaments and blobs. These are the eigenvectors of the dispersion matrix which, using the Green’s function approach, lead to a homogenized dielectric tensor.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES); EUROfusion Consortium; Association EURATOM/Hellenic Republic.
• Grant/Contract Number: FC02-01ER54648; FG02-91ER54109; FG02-99ER54525
• OSTI ID: 1609001
• Journal Information: Journal of Plasma Physics, Vol. 84, Issue 5; Conference: 17. European Fusion Theory Conference, Athens (Greece), 9-12 Oct 2021; ISSN 0022-3778
• Publisher: Cambridge University Press
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
fusion plasma
plasma waves