Equilibrium Transition Study of Merging Spheromaks to a Field-Reversed Configuration

利用两个具有相等但方向相反的环向磁通的并合球点，建立了一种新的反场位态并合结构。当它们的磁重联湮灭了它们的环向磁能时，离子温度从10eV显著增加到200eV。重新连接流出的离子加速和随后通过离子粘度的选择性离子加热导致了从低β(0.1)球点到高β (0.7-0.9) FRC的新平衡转变。这种高β弛豫湮灭了初始的磁螺旋度，揭示了一种不同于低β泰勒弛豫的新的高β弛豫。在总磁能固定的情况下，根据初始磁螺旋度小于或大于某一阈值，合并球标记会松弛为FRC或新球标记。这一形成过程的实验验证使我们得到了FRC缓慢形成、加热和欧姆加热线圈放大通量（电流）的新场景。制备的FRC的环向电流（极向磁通）在30 μ m内被成功地放大了2.5倍。

A novel merging formation of field-reversed configuration (FRC) has been developed by use of two merging spheromaks with equal but oppositely directed toroidal magnetic fluxes. A significant increase in ion temperature from 10eV to 200eV was documented when their magnetic reconnection annihilates their toroidal magnetic energies. The ion acceleration by reconnextion outflow and the follwing selective ion heating through ion viscosity were found to cause this new equilibrium transition from the low-beta (0.1) spheromaks to the high-beta (0.7-0.9) FRC.This high-beta relaxation annihilates the initial magnetic helicity, revealing a new high-beta relaxation different from the low-beta Taylor relaxation. The merging spheromaks were also found to relax either to an FRC or to a new spheromak, deoending on whether their initial magnetic helicity is smaller or larger than a threshold value under the fixed total magnetic energy. Experimental verification of this formation process lead us to anew scenario of FRC slow-formation, heating and flux (current) -amplification by ohmic heating coils. Th toroidal current (poloidal flux) of the produced FRC was amplified successfully by the factor 2.5 within 30musec.