A differential B-dot used for current measure of the magnetically insulated transmission lines (MITL) has been developed. By using the commercial PSpice software, the equivalent circuit model of the B-dot monitor, the transfer-equations and the frequency responses of the B-dot were obtained. Calculation results show that signals with frequency more than 2. 5 MHz can be perfectly measured by the B-dot. This B-dot monitor has been used for the 1. 0 m long, 2 cm AK gap coaxial-MITL experiments on "QiangGuang- I " accelerator. Experimental results show that with the shorted load, the current waveforms measured by the B-dots along the MITL are almost the same (the peak current is 1. 0 MA, and the risetime is 125 ns), namely, the current loss along the line is negligible. This results perfectly accord with the theoretical transfer characteristics of the MITL with shorted load.%研制了一种用于磁绝缘传输线(MITL)电流测量的差模式B-dot探头；利用PSpice商用软件和标定实验数据,建立了该探头等效电路模型,给出了探头系统传递函数,并分析了探头频率响应特性.计算结果表明,该探头对于被测信号大于2.5 MHz频率分量部分的相频响应基本保持不变,而幅频响应曲线呈较好的直线性.该探头已用于强光一号1.0 m长、2 cm阴阳极间隙的同轴型MITL电流传输特性研究实验,并获得了较好的测量波形.测量结果表明:短路负载条件下,传输线沿线不同位置B-dot电流测量结果基本相同,峰值电流约1.0 MA、峰值时间约125 ns.即传输线沿线电流损失几乎可以忽略,该实验结果与短路负载MITL工作特性理论较好地吻合.
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