Magnetic and Drift Surface Measurements in Heliotron DR and Compact Auburn Torsatron

Both magnetic flux surfaces and drift surfaces have been measured by electron beam mapping method in Heliotron DR and Compact Auburn Torsatron. Electron beams with the beam energy E ≤ 2 keV are launched parallel to toroidal magnetic fields of B = (0.03~ 0.05) T. Horizontal shifts of the drift surfaces are measured as a function of beam energy which show an agreement with a theoretical prediction. It has been also observed in both devices that drift surfaces near magnetic islands change their orbits at specific energies from elliptical shapes that encircle minor axis to island-like ones (“drift islands”).