Physical modeling and particle simulation technology of multi-pulse MILO cathode outgassing ionization
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摘要: 在磁绝缘线振荡器（MILO）阴极释气电离物理建模技术以及三维自洽运算基础上，研究了残存气体脉冲缩短，并分析了释气电离对多脉冲MILO运行的影响。把多脉冲释气分为脉冲内阴极释气脉间残余气体累积两个部分，研究了不同释气率以及残余气体对整个器件的运行产生影响。计算结果表明，多脉冲运行MILO最主要影响因素是释气后电离产生的正离子，当正离子密度超过发射电子密度时，束波互作用被破坏。Abstract: The commutation phenomena produced by cathode outgassing ionization is a possible factor to limit work performance of magnetically insulated transmission line oscillator (MILO), and also is the main obstacle to limit its repeat frequency. In this paper, physical modeling technology of MILO cathode outgassing ionization phenomena and three-dimensional particle simulation are presented. The relation between remaining gas of previous outgassing and pulse duration is analyzed. When the number of positive ions is greater than that of electrons the plasma caused by the ionization will rapidly reduce microwave output power.
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图 5 系统电子与气体电离离子数随时间变化关系图
Figure 5. Number of electrons and positive ions produced by N2 ionization vs time
图 6 中性化因子以及归一化周期平均功率随时间变化图
Figure 6. Charge neutralization factor fe and unitary power vs time
图 7 L-MILO典型的输入电压、电流以及相对释气率 10时电子和氮气分子的宏粒子数波形图
Figure 7. The classical waveform of input voltage, current in the L-MILO and the waveform of number of macro-particles both of electrons and N2 molecules, N3 molecules when relative outgassing rate is 10
图 8 相对释气率为10时氮气分子电离产生的正离子和二次电子的空间分布
Figure 8. Distribution of positive ions and secondary electrons produced by N2 ionization when relative outgassing rate is 10
图 10 脉间加负电压时相对释气率为10输出功率、电流以及正离子宏粒子数和二次电子，电子宏粒子数（含发射一次电子和电离的二次电子）随时间的演化关系
Figure 10. Waveforms when relative outgassing rate is 10 with negative voltage
图 11 脉间不加负电压时，相对释气率为10时的输出功率、电流以及正离子宏粒子数和二次电子，电子宏粒子数（含发射一次电子和电离的二次电子）随时间的演化关系
Figure 11. Waveforms when relative outgassing rate is 10 without negative voltage
图 12 多脉冲中性化因子以及归一化周期平均功率随时间变化图
Figure 12. Repeat frequency MILO charge neutralization factor fe and unitary power vs time
表 1 不同密度残余气体脉冲缩短时间
Table 1. Different remaining gas density vs pulse shorten time
gas density/m−3 pulse shorten time/ns 5.02×1021 3 2.51×1021 5 1.004×1021 10 5.02×1020 20 2.51×1020 70 5.02×1019 95 2.51×1019 105 5.02×1018 175 5.02×1017 220 
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