Study on the electrostatic potential in the formation of closed magnetic configuration

在低纵横比环面实验(LATE)装置中，观察到电子回旋共振等离子体在叠加在环状磁场上的弱垂直场下自发形成闭合位形的磁场。重离子束探头(HIBP)系统被用来测量静电势，它可能在磁拓扑结构的转变中起到重要作用。首次观察到当形成闭合磁场构型时，在EC共振层附近的中面上，静电势在-20~-30V处为负。这一结果与开场配置的情况完全不同，在开场配置的情况下，整个区域的静电势为正。这一结果表明，在从开场构型到闭场构型的转变过程中，静电势发生了剧烈的变化。

In the Low Aspect-ratio Torus Experiment (LATE) device, there observed a spontaneous formation of closed configuration of magnetic field when a electron cyclotron (EC) resonance plasma is produced under a weak vertical field superimposed on a toroidal field. A heavy ion beam probe (HIBP) system has been developed to measure the electrostatic potential which may play an important role on the transition of the magnetic topology. It is observed at the first time that the electrostatic potential is negative at -20 ~ -30V on the midplane near the EC resonance layer when the closed magnetic field configuration is formed. The result is completely different from the open field configuration case where the electrostatic potential is positive in the entire region. This result suggests that the electrostatic potential changes drastically through the transition from the open field configuration to the closed one.