Plasma edge density and lower hybrid current drive in JET (Joint European Torus)

Externally launched lower hybrid (LH) waves do not propagate into the plasma core during operations of JET with radial profiles with relatively high density even at the periphery, approaching the condition necessary for ITER. Modelling results indicate that this problem would be caused by parametric instability (PI)-induced LH spectral broadening, which is expected to occur in the plasma edge and prevents the coupled LH power penetrating the plasma core. However, operation with relatively high electron temperature at the edge is expected to diminish the PI effect and extend the LH current drive effectiveness to reactor-grade high density plasmas, consistent with results obtained in other experiments.

[1]  Miklos Porkolab,et al.  Theory of parametric instability near the lower‐hybrid frequency , 1974 .

[2]  Sauro Succi,et al.  Generation of Superthermal Electrons Interacting with Waves in Lower-Hybrid Range of Frequency Revisited , 1985 .

[3]  V. Parail,et al.  Effect of low magnetic shear induced by lower hybrid current drive on high performance internal transport barriers in the Joint , 2002 .

[4]  D Mazon,et al.  Modeling of a lower-hybrid current drive by including spectral broadening induced by parametric instability in tokamak plasmas. , 2004, Physical review letters.

[5]  R. Cano,et al.  Electron cyclotron emission and absorption in fusion plasmas , 1983 .

[6]  V. Tripathi,et al.  Density threshold for parametric instability of lower‐hybrid waves in tokamaks , 1984 .

[7]  M. Rosenbluth,et al.  Chapter 5: Physics of energetic ions , 1999 .

[8]  Jet Efda Contributors,et al.  Prospects for steady-state scenarios on JET , 2007 .

[9]  V. Pericoli-Ridolfini,et al.  Study of the parametric instabilities in the lower hybrid frequency range in the FT tokamak , 1987 .

[10]  J. Garcia,et al.  Lower hybrid current drive for the steady-state scenario , 2010 .

[11]  G Schettini,et al.  Current drive at plasma densities required for thermonuclear reactors. , 2010, Nature communications.

[12]  N. Fisch.  Confining a Tokamak Plasma with rf-Driven Currents. , 1978 .

[13]  F. Imbeaux,et al.  Progress in internal transport barrier plasmas with lower hybrid current drive and heating in JET (Joint European Torus) , 2002 .

[14]  K-D Zastrow,et al.  JET quasistationary internal-transport-barrier operation with active control of the pressure profile. , 2002, Physical review letters.

[15]  Yuichi Takase,et al.  Parametric excitation of ion‐sound quasimodes during lower‐hybrid heating experiments in tokamaks , 1983 .

[16]  Nathaniel J. Fisch,et al.  Theory of current-drive in plasmas , 1987 .

[17]  J. Hosea,et al.  Lower-Hybrid Current Drive in the PLT Tokamak , 1982 .

[18]  W. Fundamenski,et al.  Spectral broadening of lower hybrid waves produced by parametric instability in current drive experiments of tokamak plasmas , 2006 .

[19]  F. Crisanti,et al.  High Plasma Density Lower-Hybrid Current Drive in the FTU Tokamak , 1999 .

[20]  A. Cardinali,et al.  Parametric instabilities excited by ion sound and ion cyclotron quasi-modes during lower hybrid heating of tokamak plasmas , 1989 .

[21]  M. Lennholm,et al.  Functional dependence of the lower hybrid power absorption coefficient in JET , 1997 .

[22]  R. Slusher,et al.  Observation of parametric instabilities in the lower‐hybrid range of frequencies in the high‐density tokamak , 1985 .