[en] Magnetic islands in toroidal plasma confinement devices are generated by resonant magnetic error fields. Energetic particle drift surfaces can differ substantially from magnetic flux surfaces. In this Letter the first direct measurement of islands in energetic particle drift surfaces are presented. The understanding of these drift islands is important for the optimization of plasma confinement. These drift islands are demonstrated to form in energetic electron drift surfaces as a result of resonant magnetic field perturbations and resonant, applied electric field perturbations. The results, once corrected for inherent magnetic error fields, agree well with theoretical predictions. copyright 1995 American Institute of Physics

[en] The experimental method was developed for evaluation of a hydrogen particle flux balance over a wide range of operating conditions in the Uragan-3M torsatron (U-3M) in the course of RF discharges. Standard pressure gauges were tested for measurement of non-stationary hydrogen pressure in the U-3M vacuum chamber. The average lifetime of hydrogen ions was determined for each operation mode of U-3M.

[en] The invention is aimed at reducing magnetic field excitations in the torsatron conditioned by the discreteness of the module magnetic system and the presence of jumpers; at decreasing of heat losses in the jumpers; at diminishing and distributing ponderomotive forces between the jumpers in a more uniform way; at selecting the number of modules in a wide range; at creating a module system on the basis of a helical coil with any number of starts; at uniting all modules in a single toroidal structure wth flange resting of neighbouring modules

[en] Using analytical methods, the authors study the reasons for the formation of a magnetic-surface island structure in the central region of l=3 stellarator and torsatron magnetic configurations. Possible methods of substantially reducing the dimensions of this structure at minimum magnetic-configuration distortions are discussed. Magnetic configurations are considered both in vacuum and in the presence of a plasma. (author)

[en] The present status of LHD (Large Helical Device) control system design is described, emphasizing on the plasma operation modes, the architecture of the LHD control system, the real-time plasma feedback system with PID or Fuzzy controllers and the construction schedule of the LHD control system. The conceptual and detailed designs are under way taking flexible and reliable operations for physics experiments into account. (author)

[en] The design of superconducting magnets for a torsatron plasma confinement experiment are presented. A torsatron is a variation of a stellarator which requires half the helical windings and no toroidal field coil. Both the toroidal and poloidal fields are produced by a single set of helical winding. Due to the particular distribution of magnetic forces in the helical windings, the design of a torsatron configuration requires special consideration. In this paper, we present the force distribution on the helical coils. For the special case of uniformly distributed winding, magnetic forces and energy are calculated directly from formula for the inductance of toroids and dipoles. Significant reduction in the standard requirement can be achieved if the winding angle can be set at a particular value

No abstract available

[en] A multicontact probe placed near the wall has been used to study the distribution of the divertor fluxes over the minor azimuth in stellarator and torsatron regimes of the Saturn machine. It has been found that the plasma flux towards the outer part of the torus is much higher than the flux measured along the direction to the inner part. The plasma fluxes are localized in the vicinity of the apexes of the magnetic surfaces and their azimuthal width near the wall does not exceed 1/18th of the vacuum chamber circumference. (author)

[en] An overview is presented of an experimental program of magnetic field line mapping on the research-grade Compact Auburn Torsatron (CAT). The vacuum magnetic flux surfaces of the CAT device have been experimentally mapped in a variety of magnetic configurations. The results are compared with an extensive computer model in order to validate the coil design. In initial field mapping experiments, an up-down symmetry was identified in the vacuum magnetic surfaces, and was corrected with the use of a radial trim field. Magnetic islands are observed and their size has been reduced, also through the use of auxiliary trim coils. The Compact Auburn Torsatron is equipped with two pairs of large Helmholtz coils producing mutually orthogonal magnetic fields in the horizontal plane, and two pairs of helical saddle coils wound directly on the toroidal vacuum vessel. These trim coils are used to control the size and phase of the t = 1/2 magnetic island. Through a systematic variation of trim field components, the authors demonstrate a reduction of the inherent t = 1/2 magnetic island size by a factor of three. The technique is applicable to correcting small error fields in larger helical confinement devices. The measurements of island size are compared with measurements of magnetic field line rotation within the island, and are found to be in good agreement with first-order perturbation theory

No abstract available