Formation of a long-lived hot field reversed configuration by dynamically merging two colliding high-β compact toroids

Abstract

A high temperature field reversed configuration (FRC) has been produced in the newly built, world’s largest compact toroid (CT) facility, C-2, by colliding and merging two high-β CTs produced using the advanced field-reversed θ-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional θ-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (Te + Ti) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-β plasmas.

Achieving a long-lived high-beta plasma state by energetic beam injection

“…This is reminiscent of the ejecta from astrophysical jets and coronal mass ejections [38][39][40][41] . Incidentally, relaxation has also been observed during dynamic FRC formation processes 10,11,19 , suggesting the tendency towards a preferred plasma state in these high-b systems, just as is well known in some low-b laboratory plasmas [42][43][44][45][46][47] . Of particular importance is that the internal tilt mode usually leads to reconnection and annihilation of internal magnetic fields and hence termination of FRC.…”

“…Spectacular progress has been made on both physics and technology fronts of FRC development in the C-2 CT-merging FRC experiment (Fig. 1) [10][11][12][13] , an effort entirely funded by private resources. It has recently achieved a long-lived FRC regime, with a marked improvement in confinement over one order of magnitude, departing from the predictions based on the scaling law in the previous experiments 14 .…”

“…C-2 has adopted a collision-merging FRC formation scheme [15][16][17] by colliding two high-b CTs at a supersonic speed, each formed by a conventional theta-pinch 10,11 , producing hightemperature FRCs with radius r s B0.35 m, length ' s $ 3 m, density n e B5 Â 10 19 m À 3 , total temperature T t ¼ T i þ T e up to 1 keV, external magnetic field, B e B0.1 T, plasma current…”

MHD Activity in an Extremely High-Beta Compact Toroid

“…al., 1993). At the same time, the FRTP-based formation method has been significantly improved (Slough et al, 1989;Hoffman et al, 1993;Pietrzyk et al, 1987;Pierce et al, 1995;Guo et al, 2004Asai et al, 2000;Binderbauer et al, 2010;Guo, et al, 2011). Recently initiated new formation methods include (1) counter-helicity spheromakmerging (CHSM) (Yamada et al, 1990;Ono et al, 1993;Gerhardt et al 2008), (2) rotating magnetic field (RMF) (Slough & Miller, 2000;Knight & Jones, 1990;A.…”

“…Improved FRTP methods have also introduced low inductive voltage and program formation by FRTP (Slough et al, 1989;Hoffman et al, 1993), the coaxial slow source (CSS) (Pietrzyk et al, 1987;Pierce et al, 1995), translation-trapping formation by FRTP (Guo et al, 2004Asai et al, 2000), and collision FRC merging by FRTP (Binderbauer et al, 2010;Guo et al, 2011). Through these innovative new methods and improved FRTP methods, the FRC lifetime has been prolonged to the order of several ms, and the confinement properties have also been improved [34].…”