Collisionless reversed magnetic shear trapped electron instability and contribution of sidebands to anomalous transport

Journal Article · Tue Nov 15 00:00:00 EST 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2134770· OSTI ID:20782328

Rogister, Andre L; Singh, Raghvendra ^[1]

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1. Institut fuer Plasmaphysik, Forschungszentrum Juelich Gesellschaft mit beschraenkter Haftung (GmbH), Trilateral Euregio Cluster, European Atomic Energy Community (EURATOM) Association, D-52425 Juelich (Germany)

By keeping account of the trapped electron {nabla}B and curvature drifts, it is found that the spatial decay of the collisionless electron drift wave is governed either by the trapped electron response or by the resonant interaction of ions with the sidebands of the primary oscillation. In the former case, pairs of spatially bounded unstable and damped solutions are obtained for negative magnetic shear (s<0) if, as usual, L{sub T{sub e}}=1/{partial_derivative}{sub r} ln T{sub e}<0; there are no bounded solutions if sL{sub T{sub e}}<0. In the latter case, there is either a set of bounded damped solutions if {eta}{sub i}>0 or a set of bounded unstable solutions if {eta}{sub i}<0. The unstable modes have a radiating character and the growth rates are {gamma}{approx}(2n+1){radical}(1+2q{sup 2})vertical bar s{sub parallel}L{sub N}{omega}{sub e}*/qR vertical bar (n is the Hermite polynomial solution index, q the safety factor, s the magnetic shear parameter, R the major radius, {omega}{sub e}* the electron diamagnetic frequency, L{sub N}=1/{partial_derivative}{sub r} ln N{sub e}, and {eta}{sub i}=L{sub N}/L{sub T{sub i}}).The sidebands are responsible for unusually large ratios Q{sub e}/T{sub e}{gamma}{sub e}, where Q{sub e} and {gamma}{sub e} are the anomalous electron energy flux and the particle flux. These results may explain the box-type T{sub e} profile observed in lower hybrid current drive reversed magnetic shear plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60U Team, Phys. Fluids B 4, 2070 (1992)]. It is finally demonstrated that the ballooning hypothesis generally leads to conflicting requirements: it is thus hardly relevant for the electron drift branch{exclamation_point} The 'radiating' boundary condition that has formerly been imposed on the slab solution is finally discussed.

• OSTI ID: 20782328
• Journal Information: Physics of Plasmas, Vol. 12, Issue 11; Other Information: DOI: 10.1063/1.2134770; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BALLOONING INSTABILITY
BOUNDARY CONDITIONS
CHARGED-PARTICLE TRANSPORT
ELECTRON DRIFT
HERMITE POLYNOMIALS
IONS
JT-60U TOKAMAK
LOWER HYBRID CURRENT DRIVE
MAGNETIC FIELD CONFIGURATIONS
PLASMA
PLASMA DIAMAGNETISM
PLASMA DRIFT
PLASMA WAVES
REVERSED SHEAR
SHEAR
TRAPPED ELECTRONS