VINETA (Versatile Instrument for studies on Nonlinearity, Electromagnetism, Turbulence and Applications) creates a linear plasma column with overall length L = 4 m and radius r >10 cm. An advantage is the comparatively large plasma volume which allows for the investigation of plasma waves and instabilities, e.g. the long wavelength Alfvén-dynamics.
VINETA has a modular concept where each module has a lenght of about 1 m, an inner diameter of about 0.4 m and is surrounded by eight magnetic field coils. Each module can be operated alone or in combination with the others. Coil position and coil currents can be set separately. Such homogenous magnetic fields as possible as well as mirror- or separatrix configurations.
The plasma is created by a Helicon antenna. Helicon waves are righthand circular polarized electromagnetic waves which due to the boundary conditions in the cylinder geometry constitute an eigenmode structure. Plasma production and heating by Helicon waves are rather efficient. Densities of several 1020 m -3 are easily acessible at electron temperatures up to 10 eV. The Helicon source consists of a RF-sender (1.8 - 30 MHz), an power amplifier (Pmax= 2.5 kW (cw)), and the antenna (Nagoya Typ III).
Standard diagnostics are Langmuir-probes as well as emissive probes und magnetic probes. A LIF-diagnostics (laser induced fluorescence) and a microwave interferometer are under construction.
The flexibility of VINETA allows for systematic studies of the dynamics of plasma waves and instabilities under various pressure regimes. Currently the following projects are performed:
- the dynamics of Helikon- und Whistler waves
- low-frequency gradient driven electromagnetic instabilities
- kinetic Alfvén waves
Another central aspect of the investigations is the influence of boundary conditions and inhomogenities on the plasma dynamics.