Design and Analysis of Halo Current Diagnostic for RFX-mod2

Abstract

During its experimental campaign, the RFX-mod2 device, the upgrade of RFX-mod which is currently in its manufacturing phase, is expected to explore both Reverse Field Pinch (RFP) and tokamak operations. Both the cases will be characterized by strong halo currents, which will flow from the plasma to the graphite tiles [i.e., the plasma facing components (PFCs)], and into the resistive Inconel 625 cage which is placed around the passive stabilizing Shell (PSS). In order to measure such halo currents, and to characterize their poloidal distribution, a set of Halo Sensors (HSs) will be installed on the machine. Considering the electrical and geometrical configuration, the proposed solution is a resistive shunt made of a high precision resistive element (i.e., a manganin strip) brazed to the copper fixing elements bolted to the locking bushes (LBs, i.e., the bayonet anchoring the PFCs to the resistive cage). An array of 12 HS will be installed at a given toroidal position and covering a complete <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula> angle in the poloidal direction. This article presents the proposed design for the halo current diagnostic, describing also the multiphysics modeling activity carried out to develop such a solution.