New techniques of magnetic surface measurement on the compact Auburn torsatron

Abstract

Torsatron and stellarator plasma devices rely on magnetic surface mapping to verify the detailed vacuum magnetic field structure. Two new techniques of magnetic surface mapping are under development on the compact Auburn torsatron. The first is a fast-rotating fluorescent wire (FRFW) system. Compared with the usual fluorescent screen, fluorescent rod, or the capacitive point probe techniques, the FRFW system has the advantage of greatly increasing the number of detectable toroidal transits and of minimizing surface mapping time. The second technique is a resistive wire system which provides an alternative fast-field mapping method.

Setup and initial results from the magnetic flux surface diagnostics at Wendelstein 7-X

“…These can be divided into two groups. In the first one the spatial position of the toroidally and poloidally cir culating electron beam is detected electrically by measuring directly the electric current by means of moveable (electro static) probes or wire frames [8][9][10][11]. The second group com prises indirect optical detection methods of the electron beam, either by interaction with a background gas in the plasma vacuum vessel or by the excitation of a fluorescent detector rod [12][13][14][15][16][17][18] intersecting the magnetic field lines and hence generating a Poincaré plot.…”

Determination of error field sources by accurate mapping of the magnetic geometry of the H-1 heliac

“…Many different techniques have been used for mapping stellarator magnetic flux surfaces [8][9][10][11][12][13][14]. Wire tomography in the H-1NF heliac provides high resolution images of vacuum magnetic flux surfaces and islands without significant disruption of plasma operations [15,16].…”