Development of a Local Current Diagnostic using a Small Rogowski Coil for a Spherical Tokamak Plasma in TST-2

Abstract

A local current diagnostic using a small Rogowski coil was developed in the TST-2 spherical tokamak device (R = 0.38 m, a = 0.25 m, B_t = 0.3 T, I_p = 0.1 MA). A Rogowski coil is a cost effective tool for local current diagnostic that can detect the current signal directly. A new small Rogowski coil (outer diameter = 20 mm, inner diameter = 12 mm, number of turns = 360) with small sensitivity to external magnetic fields, such as B_t and B_p, was developed and successfully installed in the TST-2. The measured local current at the edge just inside the last closed flux surface for ohmic heating was about 15 A.