Magnetic configuration scans during divertor operation of Wendelstein 7-X

2021 ◽  
Author(s):  
Tamara Andreeva ◽  
Joachim Geiger ◽  
Andreas Dinklage ◽  
Glen A Wurden ◽  
H Thomsen ◽  
...  
Keyword(s):  
Plasma Boundary ◽  
Magnetic Configuration ◽  
Magnet System ◽  
Plasma Properties ◽  
Flux Surface ◽  
Plasma Energy ◽  
Mode Amplitude ◽  
Main Observation ◽  
Operational Phase ◽  
Rotational Transform

Abstract Wendelstein 7-X (Greifswald, Germany) is an advanced stellarator, which uses the modular coil concept to realize a magnetic configuration optimized for fusion-relevant plasma properties. The magnet system of the machine allows a variation of the rotational transform (iota) at the boundary. In the latest Wendelstein 7-X operational phase a dedicated configuration scan has been performed varying the rotational transform between magnetic configurations with iota=5/4 and iota=5/5 at the boundary. This paper presents an overview of the experiments and of the main results with respect to confinement and stability. The main observation is an increase of the plasma energy in several intermediate configurations of the scan when the 5/5-islands are close to the plasma boundary but still inside the last-closed-flux-surface. In addition, these configurations showed marked MHD-activity with a crashing behavior related to the 5/5-islands. The corresponding mode amplitude was correlated with the size of the internal 5/5 islands.

scholarly journals Kinetic processes in the overdense plasma under the action of ultra-intense laser pulses

1997 ◽  
Vol 15 (1) ◽  
pp. 33-44 ◽  
Author(s):  
M.G. Cadjan ◽  
M.F. Ivanov ◽  
A.V. Ivlev
Keyword(s):  
Vortex Formation ◽  
Laser Pulses ◽  
Incident Radiation ◽  
Plasma Boundary ◽  
Analytical Investigation ◽  
Intense Laser ◽  
Field Energy ◽  
Plasma Energy ◽  
Effects Of Radiation ◽  
Overdense Plasma

The results of numerical and analytical investigation of the ultra-intense laser pulse's interaction with overdense plasma are presented. The mechanisms of the wave field energy transformation into the overdense plasma energy are discussed. The effects of radiation propagation deep into plasma as well as long-living vortex formation, plasma boundary instability, and the surface structures formation are obtained. The basic mechanisms for the absorption of incident radiation and the role played by polarization of the radiation are studied. Nonlinear theory of plasma surface instability in the field of the strong electromagnetic wave is developed.

scholarly journals First operational phase of the superconducting magnet system of Wendelstein 7-X

2017 ◽  
Vol 124 ◽  
pp. 10-13 ◽  
Author(s):  
Konrad Risse ◽  
Victor Bykov ◽  
Michael Nagel ◽  
Thomas Rummel ◽  
Hans-Stephan Bosch ◽  
...  
Keyword(s):  
Superconducting Magnet ◽  
Magnet System ◽  
Superconducting Magnet System ◽  
Operational Phase

ELECTROMAGNETIC WAVES IN A BOUNDED, ANISOTROPIC PLASMA

1962 ◽  
Vol 40 (7) ◽  
pp. 887-905 ◽  
Author(s):  
K. A. Graf ◽  
M. P. Bachynski
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field ◽  
Electromagnetic Waves ◽  
Plane Electromagnetic Wave ◽  
Plasma Boundary ◽  
Plasma Properties ◽  
Magnetic Field Data ◽  
Reflected Waves ◽  
Quartic Equation ◽  
The Magnetic Field

The interaction of a plane, electromagnetic wave with a flat, uniform free-space – plasma interface in a static magnetic field has been considered for arbitrary angles of incidence. The dispersion relation for the plasma is a complex quartic equation which reduces to a quadratic if the static magnetic field and plasma boundary are oriented along any one of the rectangular co-ordinate axes. (These axes need not simultaneously be the same for the plasma and the magnetic field.)Numerical results are presented for the attenuation and phase constants for each of the two possible waves in the plasma, for each orientation of the static magnetic field. Data are given for various angles of incidence, plasma properties, and orientations of the static magnetic field relative to the plasma boundary.Inspection of the fields in the plasma reveals some interesting aspects. In certain cases, waves which appear to move upward towards the plasma interface exist. Since these waves may carry energy into the plasma, they have been referred to as "backward" waves. Totally reflected waves which have both finite attenuation and finite phase coefficients can also exist in the plasma. These have been termed "modified Sommerfeld" waves.

scholarly journals Gradient-based optimization of 3D MHD equilibria

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Elizabeth J. Paul ◽  
Matt Landreman ◽  
Thomas Antonsen
Keyword(s):  
Plasma Boundary ◽  
Plasma Phys ◽  
Vacuum Field ◽  
Fixed Boundary ◽  
Mhd Equilibria ◽  
Gradient Based ◽  
Boundary Optimization ◽  
Novel Method ◽  
Rotational Transform ◽  
Magnetic Well

Using recently developed adjoint methods for computing the shape derivatives of functions that depend on magnetohydrodynamic (MHD) equilibria (Antonsen et al., J. Plasma Phys., vol. 85, issue 2, 2019; Paul et al., J. Plasma Phys., vol. 86, issue 1, 2020), we present the first example of analytic gradient-based optimization of fixed-boundary stellarator equilibria. We take advantage of gradient information to optimize figures of merit of relevance for stellarator design, including the rotational transform, magnetic well and quasi-symmetry near the axis. With the application of the adjoint method, we reduce the number of equilibrium evaluations by the dimension of the optimization space ( ${\sim }50\text {--}500$ ) in comparison with a finite-difference gradient-based method. We discuss regularization objectives of relevance for fixed-boundary optimization, including a novel method that prevents self-intersection of the plasma boundary. We present several optimized equilibria, including a vacuum field with very low magnetic shear throughout the volume.

THE LEP MAGNET SYSTEM

1984 ◽  
Vol 45 (C1) ◽  
pp. C1-233-C1-239 ◽  
Author(s):  
L. Resegotti
Keyword(s):  
Magnet System

Applications of new variable hybrid magnet system

2002 ◽  
Vol 90 ◽  
pp. 65-66 ◽  
Author(s):  
Kazuya Oguri ◽  
Akihiro Mizutani ◽  
Sanshiro Ogino ◽  
Yasuzumi Ochial ◽  
Yoshitake Nishi
Keyword(s):  
Hybrid Magnet ◽  
Magnet System

Analysis of structure factors affecting suspension force of permanent magnet system with variable magnetic flux path control

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1495-1504
Author(s):  
Fangchao Xu ◽  
Yongquan Guo ◽  
Ran Zhou ◽  
Junjie Jin ◽  
Chuan Zhao ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Permanent Magnet ◽  
System Structure ◽  
Magnet System ◽  
Load Torque ◽  
Factors Affecting ◽  
Annular Gap ◽  
Path Control ◽  
Structure Factors ◽  
Flux Path

To solve the problem of reduction of suspension force of permanent magnet system with variable magnetic flux path control, according to the structure of the system, suspension principle of the permanent magnet system with variable magnetic flux path control and the generation principle of the load torque, the influence of the mechanical structure of the system on the suspension force is analyzed by changing part of parameters of the system structure. The results show that the existence of magnetic isolation plate is the main reason for the decrease of suspension force, the permanent magnet ring can be thickened to 11.91 mm, the annular gap can be reduced to 1 mm, thickness of the “F” shaped magnetizer can be increased to 9 mm to increase the suspension force.

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