为获取PTS装置磁绝缘传输线的电流, 设计、标定了微分环。探头使用镍铬合金膜屏蔽空间电子, 采用在线标定。设计相应的馈入结构从负载区分别对不同层磁绝缘传输线馈入信号, 在每个三平板传输线出口的板堆过渡区位置安装短路杆, 能够在磁绝缘传输线上得到基本均匀的电流, 实现电流探头的逐层标定。频响分析表明金属膜屏蔽效应导致探头的高频特性变差。实验表明, 贴膜的探头频响上限为50.3 MHz, 满足被测信号的要求。实测PTS装置磁绝缘传输线电流与负载区电流的测量结果自洽, 且各层电流与总电流等结果符合理论预计。

Differential-output current loops (B-dot probes) were designed and calibrated to derive magnetically-insulated transmission line(MITL) current in the PTS facility. Nichrome films were used to shield the loops from sheath electrons. All the B-dots were calibrated insitu. A feeding structure was designed to drive the MITLs from load area. In order to realize uniform current distribution azimuthally, MITL was terminated with short-circuit rods at the end of the corresponding tri-plate water line. Then the B-dots at each level could be calibrated respectively. Frequency response analysis indicates that the using of nichrome film makes the high frequency characteristics worse for B-dots. It shows in experiments that B-dots’ upper limiting frequency is 50.3 MHz, which is satisfactory for current measurement in our experiments. It also shows that MITL current and load current are self-consistent. Current of each level and combined current of all levels are reasonable according to theoretical predictions.