000200160 001__ 200160
000200160 005__ 20190316235933.0
000200160 0247_ $$2doi$$a10.5075/epfl-thesis-6197
000200160 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6197-3
000200160 02471 $$2nebis$$a10181016
000200160 037__ $$aTHESIS
000200160 041__ $$aeng
000200160 088__ $$a6197
000200160 245__ $$aTurbulent regimes in the tokamak scrape-off layer
000200160 269__ $$a2014
000200160 260__ $$aLausanne$$bEPFL$$c2014
000200160 336__ $$aTheses
000200160 502__ $$aProf. O. Schneider (président) ; Prof. P. Ricci (directeur) ; Prof. B.N. Rogers,  Prof. P. Beyer,  Dr B. Labit (rapporteurs)
000200160 520__ $$aThe tokamak scrape-off layer (SOL) is the plasma region characterized by open field lines that start and end on the vessel walls. The plasma dynamics in the SOL plays a crucial role in determining the overall performance of a tokamak, since it controls the plasma-wall interactions, being responsible of exhausting the tokamak power, it regulates the overall plasma confinement, and it governs the plasma refueling and the removal of fusion ashes. Scrape-off layer physics is intrinsically non-linear and characterized by phenomena that occur on a wide range of spatio-temporal scales. Free energy sources drive a number of unstable modes that develop into turbulence and lead to transport of particles and heat across the magnetic field lines. Depending on the driving instability, different SOL turbulent regimes can be identified. As the SOL turbulent regimes determine the plasma confinement properties and the SOL width (and, consequently, the power flux on the vessel wall, for example), it is of crucial importance to understand which turbulent regimes are active in the SOL, under which conditions they develop, and which are the main properties of the associated turbulent transport. In the present thesis we define the SOL turbulent regimes, and we provide a framework to identify them, given the operational SOL parameters. Our study is based on the drift-reduced Braginskii equations and it is focused on a limited tokamak SOL configuration. We first describe the main SOL linear instabilities, such as the inertial and resistive branches of the drift waves, the resistive, inertial and ideal branches of the ballooning modes, and the ion temperature gradient mode. Then, we find the SOL turbulent regimes depending on the instability driving turbulent transport, assuming that turbulence saturates when the radial gradient associated to the pressure fluctuations is comparable to the equilibrium one. Our methodology for the turbulent regime identification is supported by the analysis of non-linear turbulence simulations performed with the GBS code, a flux-driven, 3D code that solves the drift-reduced Braginskii equations without separation between background and fluctuations. We find that drift waves drive transport at low resistivity and negative magnetic shear, while ballooning modes dominate at high resistivity and positive magnetic shear. The ion temperature gradient instability plays a negligible role in the SOL dynamics, since the ion temperature gradient is generally below the threshold necessary for the development of this instability
000200160 6531_ $$aplasma physics
000200160 6531_ $$acontrolled fusion
000200160 6531_ $$ascrape-off layer
000200160 6531_ $$aplasma turbulence
000200160 6531_ $$afluid simulations
000200160 6531_ $$aturbulent regimes
000200160 6531_ $$aturbulent transport
000200160 6531_ $$aplasma instabilities
000200160 700__ $$0242284$$aMosetto, Annamaria$$g201346
000200160 720_2 $$0240122$$aRicci, Paolo$$edir.$$g176621
000200160 8564_ $$s6128719$$uhttps://infoscience.epfl.ch/record/200160/files/EPFL_TH6197.pdf$$yn/a$$zn/a
000200160 909C0 $$pCRPP
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000200160 909CO $$ooai:infoscience.tind.io:200160$$pthesis$$pthesis-bn2018$$pthesis-public$$pDOI$$pSB$$qDOI2$$qGLOBAL_SET
000200160 917Z8 $$x108898
000200160 917Z8 $$x108898
000200160 918__ $$aSB$$dEDPY
000200160 919__ $$aCRPP-TH
000200160 920__ $$a2014-7-11$$b2014
000200160 970__ $$a6197/THESES
000200160 973__ $$aEPFL$$sPUBLISHED
000200160 980__ $$aTHESIS