Fokker-Planck description of the scattering of radio frequency waves at the plasma edge

Hizanidis, K; Ram, AK; Kominis, Y; Tsironis, C

dc.contributor.author	Hizanidis, K	en
dc.contributor.author	Ram, AK	en
dc.contributor.author	Kominis, Y	en
dc.contributor.author	Tsironis, C	en
dc.date.accessioned	2014-03-01T01:33:29Z
dc.date.available	2014-03-01T01:33:29Z
dc.date.issued	2010	en
dc.identifier.issn	1070-664X	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20452
dc.subject	Fokker-Planck equation	en
dc.subject	plasma boundary layers	en
dc.subject	plasma confinement	en
dc.subject	plasma electromagnetic wave propagation	en
dc.subject	plasma fluctuations	en
dc.subject	plasma pressure	en
dc.subject	plasma turbulence	en
dc.subject	tearing instability	en
dc.subject	Tokamak devices	en
dc.subject.classification	Physics, Fluids & Plasmas	en
dc.subject.other	Cold plasmas	en
dc.subject.other	Current profile	en
dc.subject.other	Density fluctuation	en
dc.subject.other	Edge region	en
dc.subject.other	Electron cyclotrons	en
dc.subject.other	Excitation structures	en
dc.subject.other	Fokker Planck	en
dc.subject.other	Geometric optics	en
dc.subject.other	Lower hybrid	en
dc.subject.other	Magnetic fusion devices	en
dc.subject.other	Neoclassical tearing modes	en
dc.subject.other	Plasma current profile	en
dc.subject.other	Plasma edges	en
dc.subject.other	Plasma environments	en
dc.subject.other	Plasma pressures	en
dc.subject.other	Propagation properties	en
dc.subject.other	Radio frequency waves	en
dc.subject.other	Randomly distributed	en
dc.subject.other	Real-space	en
dc.subject.other	RF waves	en
dc.subject.other	Target regions	en
dc.subject.other	Theoretical models	en
dc.subject.other	Wave vector	en
dc.subject.other	Cyclotrons	en
dc.subject.other	Diffusion	en
dc.subject.other	Electric conductivity measurement	en
dc.subject.other	Experimental reactors	en
dc.subject.other	Fokker Planck equation	en
dc.subject.other	Fusion reactors	en
dc.subject.other	Magnetic field effects	en
dc.subject.other	Plasma confinement	en
dc.subject.other	Plasma turbulence	en
dc.subject.other	Plasma waves	en
dc.subject.other	Radio	en
dc.subject.other	Radio waves	en
dc.subject.other	Reconnaissance aircraft	en
dc.subject.other	Refraction	en
dc.subject.other	Scattering	en
dc.subject.other	Vector spaces	en
dc.subject.other	Vectors	en
dc.subject.other	Electromagnetic wave propagation in plasma	en
dc.title	Fokker-Planck description of the scattering of radio frequency waves at the plasma edge	en
heal.type	journalArticle	en
heal.identifier.primary	10.1063/1.3304241	en
heal.identifier.secondary	http://dx.doi.org/10.1063/1.3304241	en
heal.identifier.secondary	022505	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	In magnetic fusion devices, radio frequency (rf) waves in the electron cyclotron (EC) and lower hybrid (LH) range of frequencies are being commonly used to modify the plasma current profile. In ITER, EC waves are expected to stabilize the neoclassical tearing mode (NTM) by providing current in the island region [R. Aymar, Nucl. Fusion 41, 1301 (2001)]. The appearance of NTMs severely limits the plasma pressure and leads to the degradation of plasma confinement. LH waves could be used in ITER to modify the current profile closer to the edge of the plasma. These rf waves propagate from the excitation structures to the core of the plasma through an edge region, which is characterized by turbulence-in particular, density fluctuations. These fluctuations, in the form of blobs, can modify the propagation properties of the waves by refraction. In this paper, the effect on rf due to randomly distributed blobs in the edge region is studied. The waves are represented as geometric optics rays and the refractive scattering from a distribution of blobs is formulated as a Fokker-Planck equation. The scattering can have two diffusive effects-one in real space and the other in wave vector space. The scattering can modify the trajectory of rays into the plasma and it can affect the wave vector spectrum. The refraction of EC waves, for example, could make them miss the intended target region where the NTMs occur. The broadening of the wave vector spectrum could broaden the wave generated current profile. The Fokker-Planck formalism for diffusion in real space and wave vector space is used to study the effect of density blobs on EC and LH waves in an ITER type of plasma environment. For EC waves the refractive effects become important since the distance of propagation from the edge to the core in ITER is of the order of a meter. The diffusion in wave vector space is small. For LH waves the refractive effects are insignificant but the diffusion in wave vector space is important. The theoretical model is general enough to study the effect of density blobs on all propagating cold plasma waves. © 2010 American Institute of Physics.	en
heal.publisher	AMER INST PHYSICS	en
heal.journalName	Physics of Plasmas	en
dc.identifier.doi	10.1063/1.3304241	en
dc.identifier.isi	ISI:000275028700019	en
dc.identifier.volume	17	en
dc.identifier.issue	2	en