Distribution of a pulsed current in a cylindrical conductor of variable conductivity

In the IPP-Kharkiv there are two torsatrons (stellarators) in operation, and in both of them Alfvén resonance heating under high-k ∥ conditions is used. This method of heating is advantageous for small-size devices, since in contrast to the minority and second-harmonic heating it can be realized at lower plasma densities. A series of experiments has been performed at the Uragan-3M torsatron with an aim to investigate the features of the discharge with a three-half-turn antenna. Electron temperatures in the range are achieved at plasma densities . The plasma energy content has increased by a factor of 2 with respect to the plasma produced with the frame antenna. A new four-strap shielded antenna has been manufactured and installed in the Uragan-2M. A high-frequency discharge for wall conditioning is introduced in the Uragan-2M torsatron. The discharge is sustained by a specially designed small frame antenna, and efficient hydrogen dissociation is achieved. A self-consistent model has been developed for simulation of plasma production in ICRF. The model includes a set of particle and energy-balance equations for the electrons, and the boundary problem for the Maxwell equations. The first calculation results on RF plasma production in the Uragan-2M stellarator with the frame-type antenna are presented.

Section: Wall Conditioning Discharges In Uragan-2mmentioning

confidence: 99%

mentioning

confidence: 99%

RF plasma production and heating below ion-cyclotron frequencies in Uragan torsatrons

Moiseenko¹,

Berezhnyj²,

Bondarenko³

et al. 2011

“…It is this fairly general case of high-frequency fields which is fulfilled in the experimental toroidal devices RT-0 [17] and RT-2 [18] . We shall restrict ourselves in this article to solving the cylindrical case because, as Shafranov [1] has shown, taking toroidality into account leads only to small corrections in the increments for the helical modes.…”

Section: General Formulation Of the Problemmentioning

confidence: 99%

Dynamic stabilization of magnetohydrodynamic instabilities by means of multipole high-frequency fields

Sidorov

Soldatenkov

1972

This article is devoted to problems of stability in a plasma column which has a hybrid current (constant and variable in time) flowing through it. The variable component of the current is, generally speaking, a helical multipole with zero skin layer. The constant current component exhibits either a skin effect or a uniform distribution over the column cross-section. The perturbations considered here are of the surface-wave type, since it is known that this type of perturbation plays a major role in a current plasma with a free boundary.Analysis of the dispersion equation obtained indicates that the application of high-frequency multipole fields reduces the critical q-value in current systems. From the physical point of view, stabilization is brought about by the presence of a time-averaged magnetic well and by the effect of dynamic shear. It was found that the effectiveness of stabilization increases as the multipolarity of the high-frequency field, a fact which is explained by increased depth (on average) of the magnetic well. This requires an increase in the radio-frequency circuit currents, however, which means that circuits with a high Q-factor must be used.The authors also show to what extent the high-frequency circuit (helical conductors) can assume the role of a stabilizing sheath. In the model adopted here the circuit is taken to be an anisotropically conducting sheath and the helical pattern is reflected; perturbations are found on which the circuit exercises a stabilizing effect. These are perturbations whose helix coincides with that of the high-frequency circuit currents projected on a cylindrical plasma surface of radius “a”. All other perturbations remain unaffected by the circuit: the perturbed currents do not form a circuit because the helices of the perturbation and the circuit are crossed.

“…The analysis is frequently based on the Vlasov equation in the drift approximation, or on the two fluid equations. Some of this literature is listed in Refs [74][75][76][77][78][79][80][81][82], There are considerable difficulties in the first place in identifying the drift instabilities experimentally, secondly the interaction of these instabilities with high-frequency oscillatory fields is even more difficult to study. However, due to ingenious experimental set-ups and techniques, a considerable amount of information has been obtained in this difficult field of plasma physics.…”

Section: Related Topicsmentioning

confidence: 99%

Equilibrium and stability of MHD-fluids by dynamic techniques

Berge¹

1972