Collisional Merging Process of Field-Reversed Configuration Plasmas in the FAT-CM Device

• Published in: Plasma and Fusion Research 2018/08/10, Vol.13, pp.3402098-3402098
• Main Authors: TANAKA, Fumiyuki, ASAI, Tomohiko, SEKIGUCHI, Junichi, TAKAHASHI, Tsutomu, ISHIWATA, Junpei, EDO, Takahiro, ONO, Naoto, MATSUI, Keisuke, WATANABE, Shintarou, HISHIDA, Daiki, KOBAYASHI, Daichi, HIROSE, Yousuke, HOSOZAWA, Akiyoshi, MOK, Yung, DETTRICK, Sean, ROCHE, Thomas, GOTA, Hiroshi, BINDERBAUER, Michl W., TAJIMA, Toshiki
• Format: Article
• Language: English
• Subjects: 2D resistive MHD simulation; field-reversed configuration; FRC merging; high beta plasma; magnetically confined plasma
• ISSN: 1880-6821; 1880-6821
• DOI: 10.1585/pfr.13.3402098

In order to investigate the collisional merging process of field-reversed configurations (FRCs), the FAT device has recently been upgraded to FAT-CM, consisting of two field-reversed theta-pinch (FRTP) formation sections and the confinement section. Collisional merging of the two FRCs causes a conversion of the kinetic energy to mostly thermal ion energy, resulting in an increase of the ion pressure that greatly expands the FRC size/volume. This increase of the FRC size is observed by magnetic diagnostics in the confinement region, leading to an increase in the excluded flux; on a side note, these characteristics/phenomena have also been observed in C-2/C-2U experiments at TAE Technologies. The process of FRC formation, translation and collisional merging in FAT-CM has been simulated by Lamy Ridge, 2D resistive magnetohydrodynamics code, in which the same phenomenon of the excluded-flux increase via FRC collisional merging has been observed. Simulation results also indicate that there is an importance of the external magnetic field structure/profile in the confinement region, clearly affecting the FRC merging. Steeper magnetic field gradient by a strong mirror field appears to suppress the axial expansion of collided FRCs and lead a merged FRC to higher temperature.