Numerical investigation of dielectric window breakdown with different high-power microwave and material characteristic parameters

For investigating the influence of high-power microwave and material characteristic parameters on flashover and breakdown on dielectric surfaces, a 1D3V PIC-MCC code is adopted in this simulation. By using this code, the number of electrons and ions, electron and ion density distributions, time and space distribution of space charge field, average electron energy, discharge power, deposited power, excitation and ionization loss power, and ionization frequency are studied numerically in detail. Ionization frequency increases with electric-field increasing, and then reaches to saturation and decreases slowly; higher value of electric-field causes more secondary electrons to form higher deposited power. Ionization frequency increases with microwave frequency decreasing, and then reaches to saturation and decreases slowly; higher frequency may suppress multipactor discharge. Thus high-power microwaves with higher value of electric-field and lower frequency is easier to induce breakdown. Reflection causes electric-field decrease and magnetic-filed increase on dielectric surfaces, which leads to the decrease of ionization frequency and secondary electron decrease, the shortening of the oscillation time of multipactor discharge, and the breakdown risk increase of the inner region of device. Compared with linear polarization, circular polarization causes more secondary electrons to form higher deposited power, and the breakdown risk increases. Shorter pulses produce fewer electrons and ions with lower average energy, which form lower deposited power, so high-power microwaves with long pulses are easier to induce breakdown. Longer rise time of pulses causes longer breakdown time, but could not decrease the breakdown risk. Compared with surface roughness, higher value of materials secondary emission yield increases breakdown risk markedly. Ionization frequency and average electron energy increase firstly, and then decrease with gas pressure increasing. Multipactor discharge dominates at low pressure, and ionization dominates at high pressure.