激光等离子体实验中脉冲强磁场设备产生的电磁干扰和屏蔽方法

Generation and mitigation of electromagnetic pulses from pulsed intense magnetic field device in laser plasma experiments

  • 摘要: 脉冲强磁场在高功率激光与物质相互作用领域有着重要的作用。报导了用于激光等离子体实验的脉冲强磁场设备产生的电磁干扰的空间和频谱分布特征以及屏蔽方法的实验结果。发现电磁干扰来自于脉冲强磁场设备的放电主回路、充电和接地的次级回路。这些电磁干扰主要通过电容性耦合进入真空靶室、进而通过传导型耦合途径从靶室进入电子设备,或通过充电线和接地线进入电网或弱电电缆、最终进入电子设备,部分电磁辐射通过自由空间传输方式耦合进电缆和电子设备。通过断开传导型耦合路径和屏蔽自由空间电磁辐射等途径来消弱电磁干扰,对比实验发现这些措施对抑制电磁干扰有明显的效果。这些结果可以应用于强磁场调控激光等离子体的实验研究。

     

    Abstract: Pulsed intense magnetic fields play an important role in the field of high power laser material interaction, while the electromagnetic pulse generated by pulsed intense magnetic field devices will disturb the signal measurement in laser plasma experiment. We measured the spatial distribution and spectral characteristics of electromagnetic pulse using Rogowski coils, high-voltage probes, antennas, and sampling resistors on the laser plasma experimental platform. It is found that the electromagnetic pulses come from the main discharge circuit of the pulsed intense magnetic field device, and the secondary circuit of charging and grounding. The electromagnetic pulses transform onto the vacuum target chamber through capacitive coupling between the transmission line and the flange on the vacuum target chamber that places the transmission line, and then enter the electronic devices through conductive coupling pathways, or enter the power grid or weak current cables through charging lines and grounding wires, and finally enter the electronic devices. Part of the free space electromagnetic pulse is directly coupled into cables and electronic devices. We depress the electromagnetic noise that enters the detector by disconnecting the conductive coupling path and shielding free space electromagnetic pulse. Experiments showed that the measured electromagnetic pulse amplitude, especially at the 0.14 MHz discharge main frequency component, was well suppressed, by physically disconnecting the electrical connection between the power grid and electronic equipment. Isolating the high-voltage power supply from the low-voltage grounding connection can decrease the electromagnetic noise markedly. Shielding shell and shielding cabinet that cover the electronic devices are available approaches to depress the free space and conductive coupled electromagnetic noise.

     

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