Topic/Type: 1.2 Fusion Plasmas (magnetic & inertial confinement), Oral

Drift flute turbulence in a high beta plasma

J. Kindel1, V. I. Sotnikov1, O. Onishchenko1, V. Ivanov1, R. Presura1, E. Yasin1, J. Leboeuf2

1 Nevada Terawatt Facility, University of Nevada Reno, 0220, Reno, NV 89557, USA
2 JNL Scientific, Casa Grande, AZ 85294, USA

Linear analysis of the compressible electromagnetic flute mode instability in a finite beta current carrying Z-pinch plasma has demonstrated good qualitative agreement between theory and experiment. Experimental data obtained during wire array implosion experiments on the Zebra pulsed power generator has shown good agreement with respect to excited wavelengths and characteristic growth rates.
In order to investigate the nonlinear stage of the instability, nonlinear equations applicable in a high beta plasma for arbitrary spatial scales in comparison with the ion Larmor radius are derived. In order to solve numerically nonlinear equations which describe saturation of the flute instability, we developed a 2D numerical code FLUTE based on the pseudo-spectral method for spatial representation and the two-step predictor corrector method for time advance. The code solves nonlinear equations for density, electrostatic potential and ion temperature.
The numerical solution describes spontaneous generation of large-scale structures as an efficient channel for the energy transfer from small-scale flute turbulence to large-scale convective motions. Numerical results also show wave energy transfer to a shorter wavelength region. These flute modes can be responsible for the intermittent convective-like transport across the magnetic field associated with meso-scale coherent structures and enhanced viscous heating associated with short scales in the turbulent wave spectrum. Spectral analysis of the numerical results allows us to see the evolution of the excited drift flute turbulence in space and time.
This work will demonstrate that two-fluid hydrodynamics can adequately describe nonlinear dynamics of flute waves in an inhomogeneous plasma with arbitrary spatial scales and arbitrary plasma beta. For Z-pinches this is an important consideration.

O. Onishchenko permanent address: Institute of Physics of Earth, 123995 Moscow, Russia

Work supported by the US Department of Energy under Grant No. DE-FC52-06NA27616 at UNR and ISTC N3520.