Design and implementation of high-field-side divertor target biasing system on J-TEXT

Recently, a toroidally quasi-symmetric high-field side divertor target biasing (HDTB) system has been newly installed on the J-TEXT tokamak. It aims to modulate the E×B drift in the scrape-off layer (SOL) under the high-field side mid-single null (HFS-MSN) divertor configuration by applying biasing to the divertor targets. The HDTB system consists of upper and down target arrays, which are misaligned in the magnetic surface coordinate system. The upper biased target (UBT) array is located entirely within the SOL region, while the down biased target (DBT) array covers the down strike point and partially extends into the private flux region (PFR). Each array is further divided into 6 mutually insulated target groups distributed toroidally. Utilizing a switch control system, various biasing modes can be generated, including grounded hybrid biasing (GHB) mode, floating hybrid biasing (FHB) mode and driving non-axisymmetric SOL current filaments. Preliminary experimental results show that GHB mode and FHB mode effectively alter the distribution of E×B flow in the SOL, modulate the asymmetry of strike point parameters, and change the decay length of particle flow in the SOL.