射频击穿等离子体对高功率微波传输特性的影响

High power microwave propagation properties in radio frequency breakdown plasma

利用极化正交的高功率微波合路器,开展了等离子体对于微波传输特性的实验研究.通过改变前级源的功率和脉冲宽度,使得在合路器耦合缝处发生射频击穿,产生等离子体.等离子体扩散进入微波传输主通道,对于高功率微波的传输产生明显的影响,导致微波能量吸收和极化的偏转.初步实验结果表明,等离子体扩散到主通道中心的时间约为3μs,扩散速度约为1μs/cm,等离子体的恢复时间约为5μs.实验测得等离子体导致的微波极化方向最大偏转角度约为4.1?,此时通道内电子个数约为3.7×1015,极化偏转角度与电子数密度以及微波频率相关.

The effect of plasma on the microwave propagation properties is investigated experimentally by using a high power microwave combiner. The plasma is generated by radio-frequency breakdown on the coupling slit of the combiner through changing the power or pulse width of the prime microwave source. The plasma diffuses from the slit to the high power microwave transmission channel, and induces the absorption of microwave energy and the rotation of microwave polarization. The results show that the spread velocity of plasma is about 1 μs/cm, and the duration is about 5 μs. The polarization rotating angle is determined by electron density and microwave frequency. The maximum rotating angle is 4.1° while the number of electron is about 3.7×10^15.