Turbulence investigations during ergodic divertor operation with induced 2/1 tearing mode

Within the last year of TEXTOR operation a major part of the experiments were dedicated to the interaction of the ergodized plasma edge, induced by the dynamic ergodic divertor (DED), with the core plasma. Systematic experiments are performed in the 3/1 configuration of the DED. Depending on , the DED generates a locked 2/1 mode in the plasma at a critical current in the DED coils. Different diagnostics were used to measure the plasma response in the core and edge. The investigations in this paper are focused on the measurement of density fluctuation and the analysis of the coherent-mode structure outside the q = 2 surface using O-mode poloidal correlation reflectometry. A reduction of the quasi-coherent mode amplitude and frequency is observed, caused by the 2/1 mode together with a decrease of the density scale length. Moreover, the deduced poloidal rotation velocity at the q = 3 surface changes from the electron to the ion diamagnetic drift direction with the onset of the 2/1 island. Also a reduction of the density fluctuations is observed as well as a decrease in the poloidal correlation length. From Ar-injection a delayed inward propagation of the emission maximum is observed for different Ar ionization stages when the 2/1 mode is generated.Similar experiments with a slowly rotating DED show that the steepened density gradients are spatially localized and confirm the hypothesis that the 2/1 mode is responsible for the observations.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004.     

Study of the plasma potential evolution during ECRH in the T-10 tokamak and TJ-II stellarator

Comparison of the plasma electric potential evolution in the T-10 tokamak and TJ-II stellarator was performed. The core potential was measured by the heavy-ion beam probing and the edge potential was measured by Langmuir probe. The intrinsic potentials in both devices are different in sign, positive in TJ-II low-density discharge and negative in T-10 higher-density discharges, but during ECRH they evolve similarly: the potential becomes more positive, and increase of ECRH power leads to stronger rise of core potential. Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005.     

Study of Geodesic Acoustic and Alfvén Modes in Toroidal Fusion Devices (Brief Review)

JETP Letters - Geodesic acoustic modes, Alfvén eigenmodes, stationary and oscillating components of the electric field, and their relations to plasma confinement have been studied. Theoretical...     

Efficiency of Sulfuric Acid Leaching of Lanthanides in Relation to Quality of Phosphosemihydrate Obtained from Khibiny Apatite Concentrate

Reasons for a decrease in recovery of lanthanides by sulfuric acid leaching from separate lots of phosphosemihydrate produced by Voskresenskie Mineral'nye Udobreniya joint-stock company were studied.     

Stationary Operated Lithium In-Vessel Elements of a Tokamak

Physics of Atomic Nuclei - The concept of plasma facing elements (PFE) of a stationary fusion tokamak reactor based on the use of stagnant or slow-flowing liquid lithium enclosed in a...     

Leaching of Lanthanides from Phosphohemihydrate with Nitric Acid

Factors were examined that determine passing of lanthanides into solution during nitric acid leaching of phosphohemihydrate obtained in the course of production of wet-process phosphoric acid from Khibiny apatite concentrate by the hemihydrate technique. The data obtained were compared to the results of sulfuric acid leaching.     

Interpolation with Specified Error of a Point Series Belonging to a Monotone Curve

The paper addresses the problem of modeling a smooth contour interpolating a point series belonging to a curve containing no special points, which represents the original curve with specified accuracy. The contour is formed within the area of possible location of the parts of the interpolated curve along which the curvature values are monotonously increased or decreased. The absolute interpolation error of the point series is estimated by the width of the area of possible location of the curve. As a result of assigning each intermediate point, the location of two new sections of the curve that lie within the area of the corresponding output section is obtained. When the interpolation error becomes less than the given value, the area of location of the curve is considered to be formed, and the resulting point series is interpolated by a contour that lies within the area. The possibility to shape the contours with arcs of circles specified by characteristics is investigated.     

Representation of a Monotone Curve by a Contour with Regular Change in Curvature

The problem of modelling a smooth contour with a regular change in curvature representing a monotone curve with specified accuracy is solved in this article. The contour was formed within the area of the possible location of a convex curve, which can interpolate a point series. The assumption that if a sequence of points can be interpolated by a monotone curve, then the reference curve on which these points have been assigned is monotone, provides the opportunity to implement the proposed approach to estimate the interpolation error of a point series of arbitrary configuration. The proposed methods for forming a convex regular contour by arcs of ellipses and B-spline ensure the interpolation of any point series in parts that can be interpolated by a monotone curve. At the same time, the deflection of the contour from the boundaries of the area of the possible location of the monotone curve can be controlled. The possibilities of the developed methods are tested while solving problems of the interpolation of a point series belonging to monotone curves. The problems are solved in the CAD system of SolidWorks with the use of software application created based on the methods developed in the research work.     

Modern Diagnostics for Investigation of Lithium Element Behavior in Tokamaks

Physics of Atomic Nuclei - The introduction of lithium as a material for production of in-vessel plasma-facing elements of the tokamak necessitates the development of the corresponding diagnostic...     

Space and time evolution of plasma potential in T-10 undervariation of main gas influx

The HIBP method was used in the experiments on the T-10 tokamak to measure the space potential distribution as a function of gas feed. A high electric field was observed in the region where the ionization of neutrals takes place. The correlation of the potential with the gas flux dynamics and the MHD activity was also found