Simulation of high-frequency modes and their effect on insulator breakdown in the pulse line ion accelerator
Simulation of high-frequency modes and their effect on insulator breakdown in the pulse line ion accelerator
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DOI：
10.1016/j.nima.2009.03.230
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发表时间：
2009-07
影响因子：
1.4
通讯作者：
C. Ling;Simon S. Yu;E. Henestroza
中科院分区：
文献类型：
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作者：
C. Ling;Simon S. Yu;E. Henestroza
脉冲线离子加速器（PLIA）通过向螺旋线的一端施加电压脉冲来产生行进电磁（EM）波，该螺旋线加速并轴向限制重离子束脉冲。在真空绝缘子表面上观察到一种异常闪络现象，这种现象限制了加速场的幅度。有人怀疑输入脉冲中高频模式的一小部分可能是击穿的原因。采用有限积分法的麦克斯韦方程进行了仿真，研究了绝缘子表面的电场。提出了一种标度律，大大减少了模拟计算时间。它是基于这样的假设，即对于给定波长的EM场的图案是独立的线间距，只要波长是远远长于线间距和终端电阻器被调整，以保持阻抗匹配。在这些数值模拟的基础上，我们得出结论，高频模式，即使在非常低的振幅，确实可能导致观察到的绝缘子闪络。
The pulse line ion accelerator (PLIA) produces a traveling electromagnetic (EM) wave by applying a voltage pulse to one end of a helix that accelerates and axially confines a heavy-ion beam pulse. An anomalous flashover phenomenon has been observed on the vacuum-insulator surface that limits the amplitude of the accelerating field. It has been suspected that a small component of high-frequency modes in the input pulse may be the cause of the breakdown. Simulation using MAFIA (MAxwell's equations by Finite Integration Algorithm) was conducted to investigate the fields on the insulator surface. A scaling law was proposed to reduce substantially the computational time in simulation. It is based on the hypothesis that the pattern of EM field for a given wavelength is independent of the wire spacing as long as the wavelength is much longer than the inter-wire spacing and the termination resistors are adjusted to maintain impedance matching. On the basis of these numerical simulations, we conclude that high-frequency modes, even at very low amplitudes, may indeed lead to the observed insulator flashover.