Magnetic-field study in a compact helical system

Abstract

Implementation of the designed magnetic field in the compact helical system torsatron device has been verified both experimentally and numerically. A misalignment of the outer two sets of poloidal field coils has been identified both quantitatively and qualitatively. A magnetic-field-mapping experiment has indicated that closed magnetic surfaces have been successfully achieved up to 95% of the outermost surface and that islands exist on the m=2 and 3 major rational surfaces. The experimental results and the computational analysis consistently explain that these islands are mainly caused by the ambient field resulting from magnetization of the building structure. The m=2 island width is estimated to be several millimeters during regular plasma heating experiments when the toroidal field is more than 1 T.

Experimental verification of nonconstant potential and density on magnetic surfaces of helical nonneutral plasmas

“…Finally, we should mention the effect of magnetic islands on the observed s variation on magnetic surfaces, because data are obtained in helical magnetic surfaces. A magnetic field mapping experiment 17 has identified magnetic islands on the m =2, 3, and n = 1 major rational surfaces on CHS, where m and n denote the poloidal and toroidal mode numbers, respectively. Since the width of the n / m =1/2 island is about 2.5 cm for the case where BӍat R ax is 0.9 kG, the islands probably influence the local structure of s around the rational surfaces.…”

Experiments on Injecting Electrons Into Helical Magnetic Field Configuration

“…Since the LCFS does not touch the vacuum vessel, the presence of the SMR outside the LCFS has been inferred from this computation. Closed magnetic surfaces for 0.9 kG on CHS have experimentally been confirmed by a magnetic surface mapping [10], [16].…”

Investigation of the Magnetic Field Configuration for Magnetic Surface Measurements in the CFQS Quasi-Axisymmetric Stellarator

“…The purpose of the experiments is to confirm the formation of magnetic field line structures for plasma confinement and the completeness of the magnetic coil installation. A fluorescent method [4][5][6][7] is planned to be adopted in the experiments for magnetic surface measurements. A mesh, which fully covers the poloidal cross-section of the plasma confinement region, is inserted into the vacuum vessel through a large rectangular outer port.…”