First Experimental Demonstration of Plasma Shape Control in a Tokamak Through Model Predictive Control

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Recent progress in the Large Helical Device (LHD) experiment during the last 2 yr is reviewed. The LHD has been extending its operational regime toward fusion-relevant conditions while taking advantage of the net-current-free heliotron concept employing a superconducting coil system. Heating capability has exceeded 10 MW, and the central ion and electron temperatures have reached 7 and 10 keV respectively. The maximum values of beta and pulse length have been extended to 3.2% and 150 s, respectively. Severa

The dependence of the measured damping rate upon the neutral beam heating power (P-NBI) and plasma beta has been experimentally investigated for n = 1 toroidal Alfven eigenmodes (TAEs) in JET limiter plasmas with a monotonic safety factor profile and low edge magnetic shear. The mode frequency is observed to decrease with increasing beta, as predicted by various theoretical models. For low P-NBI < 3 MW, a single n = 1 TAE splits into two modes closely spaced around the expected TAE frequency, and the mode d

Gyrotrons at high frequency with high-output power are mainly developed for microwave heating and current drive in plasmas for thermonuclear fusion. For the stellarator Wendelstein 7-X, now under construction at IPP Greifswald, Germany, a 10-MW electron-cyclotron-resonance-heating (ECRH) system is foreseen. A 1-MW 140-GHz gyrotron with synthetic diamond window for continuous wave operation and with a single stage depressed collector for energy recovery and improvement of efficiency has been designed, constr

This paper presents an alternative approach to the deterministic global optimisation of problems with ordinary differential equations in the constraints. The algorithm uses a spatial branch-and-bound approach and a novel procedure to build convex underestimation of nonconvex problems is developed. Each nonconvex functional in the original problem is underestimated by adding a separate convex quadratic term. Two approaches are presented to compute rigorous values for the weight coefficients of the quadratic

A correlation-based controller tuning method is proposed for the \Design and optimization of restricted-complexity controllers" benchmark problem. The approach originally proposed for model following is applied to solve the disturbance rejection problem. The idea is to tune the controller parameters such that the closed-loop output be uncorrelated with the measured disturbance. Since perfect decorrelation between the closed-loop output and the disturbance is not attainable with a restricted-complexity contr

Electromagnetic microinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. Ion dynamics is described by the gyrokinetic equation, so that finite ion Larmor radius effects are taken into account to all orders. Nonadiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A large aspect ratio plasma with circular shifted surfaces is consider

An experimental study of the extraordinary mode (X mode) absorption at the third electron cyclotron harmonic frequency has been performed on the TCV tokamak in plasmas preheated by X mode at the second harmonic. Full single pass absorption of injected X3 power was measured with X2 preheating in co-current drive (CO-ECCD). The measured absorption exceeds that predicted by the linear ray tracing code TORAY-GA by more than a factor of 2 for the CO-ECCD case. Experimental evidence indicates that a large fractio

Long timescale density peaking has been observed in JET plasmas leading to densities exceeding the Greenwald value. These neutral beam heated discharges are characterized by type-I ELMS and good energy confinement. Central density is limited by neoclassical tearing modes or by termination of H-mode preceded by loss of sawteeth. When these limiting factors are avoided (i.e. at intermediate power level and With optimization of gas puffing) quasi-stationary high density plasmas with peaked density profile are

SULTAN (acronym for SUpraLeiter TestANlage) is the major facility for testing and evaluating high current superconductors for the next generation of fusion magnets. Located at Paul Scherrer Institut PSI in Villigen, Switzerland, the facility was constructed in the late seventies as a common venture of three European Laboratories: ENEA (Italy), ECN (Netherlands), and SIN (Switzerland). Since 1994 SULTAN is operated by EPFL-CRPP and is offered by the European Commission as contribution to the worldwide cooper

Current profile tailoring by electron cyclotron heating (ECH) and current drive (ECCD) is used to improve central electron energy confinement in the TCV tokamak. Counter-ECCD on axis alone achieves this goal in a transient manner only. A stable scenario is obtained by a two-step sequence of err-axis ECH, which stabilizes magnetohydrodynamics modes, and on-axis counter-ECCD, which generates a flat or inverted current profile. This high-confinement regime, with central temperatures up to 9 keV (at a. normaliz

A high temperature superconducting current lead for application in fusion magnets was developed in collaboration of three laboratories. Bi-2223 Ag/Au tapes were selected to be used in the current lead and two industrial fabricated 10 kA modules were extensively tested. Both modules were used in the 20 kA current lead which was successfully tested in continous operation at 20 kA and over short time up to 40 kA. (C) 2001 Elsevier Science B.V. All rights reserved.

Alfven eigenmodes (AEs) with intermediate toroidal mode numbers are modelled using the global gyrokinetic PENN code to determine the stability of high performance tokamak discharges in the presence of energetic particles. A large plasma pressure and a weak magnetic shear in the core give rise to radially extended kinetic AEs, which are stabilized by the high shear at the edge of a divertor (X point) configuration. Large values for the safety factor and the ion Larmor radius in reversed shear operation may h

First Experimental Demonstration of Plasma Shape Control in a Tokamak Through Model Predictive Control

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Review on the progress of the LHD experiment

Measurement of the damping rate of n=1 toroidal Alfven eigenmodes as a function of the neutral beam heating power and plasma beta on JET

Advanced high-power gyrotrons

A New Approach in Deterministic Global Optimisation of Problems with Ordinary Differential Equations

Correlation-Based Tuning of a Restricted-Complexity Controller for an Active Suspension System

Global-gyrokinetic study of finite beta effects on linear microinstabilities

Full absorption of third harmonic ECH in TCV tokamak plasmas in the presence of second harmonic ECCD

Long timescale density peaking in JET

User specifications for conductor samples to be tested in the SULTAN facility

Long-pulse improved central electron confinement in the TCV tokamak with electron cyclotron heating and current drive

Development program of a 60 kA high temperature superconductor current lead for the ITER toroidal field coils

Stability of Alfven eigenmodes in optimized tokamaks