本文采用数值方法求解Grad‐Shafranov方程获得CT‐6B交流放电实验总电流过零时的平衡位形和磁场分布，进而结合粒子在磁场中的运动方程，模拟氘离子在该平衡位形中的运动轨迹，统计氘离子的损失率与损失位置。结果表明：总电流过零时刻的平衡位形为内外两侧电流反向平衡位形，在强、弱场侧各存在1个磁岛，电流在磁岛附近取极值；位于强场侧的粒子几乎不损失，弱场侧的粒子在径向位置很大时存在损失，越靠近边界损失率越高；损失位置基本上位于赤道面以下并在最底部达到极值；随初始角变大，氘离子轨迹由通行轨迹变成损失轨迹再向香蕉轨迹演变。%The equilibrium configuration and magnetic distribution were achieved by numerically solving Grad‐Shafranov equation w hen the total current exceeded zero in the AC operation experiment on CT‐6B .Considering the motion equation of particles in magnetic field , trajectories of deuterium ions in this equilibrium configuration were simulated ,and also ,the ratios and positions of deuterium ions loss were statistically calculated .The results indicate that the equilibrium configuration is the current‐reversal equilibrium configurations with two oppositely flowing current components on the high‐field side and low‐field side w hen the total current exceeds zero ,magnetic islands exist at high‐field side and low‐field side both ,and current value is extreme value near the magnetic island . T he particles in high‐field side lose barely , but loss happens w hen radial location is much high at low‐field side and the loss rate increases as it reaches to boundary .Basically ,positions of loss locate beneath equatorial plane and loss reaches the extreme value at the very bottom .Trajectory of deuterium ions converts from pass‐ing particle trajectory to lost particle trajectory firstly ,and further ,to trapped particle trajectory w hen the initial angle becomes large .
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