Scrape-Off-Layer Currents in HBT-EP Investigated Using High-Field-Side Tiles and Magnetic Sensors

A new set of high-field-side scrape-off-layer (HFS SOL) tiles was recently installed on the High Beta Tokamak-Extended Pulse (HBT-EP) device, providing data on SOL currents (SOLC). The tiles provide particularly important data on disruptions (See Levesque, this session). This study focuses on currents seen by the tiles during the main discharge period of plasmas, focusing on the correlation and phase relationships between current and magnetic perturbations seen through the tile arrays and magnetic sensor arrays. An extension of work previously done using low-field-side (LFS) tiles, this work characterizes SOLC using the HFS array in two toroidal locations separated by ~90°, comparing these results with those found using LFS tiles in six toroidal locations. We then use the observed properties of SOLC in HBT-EP to distinguish between proposed theoretical mechanisms, such as those presented in [1], for asymmetric SOLC.

[1] J.P. Levesque et al 2017 Nucl. Fusion 57 086035.