Neutral depletion in a collisionless plasma
Neutral depletion in a collisionless plasma
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DOI：
10.1109/tps.2008.918777
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发表时间：
2008-04-01
影响因子：
1.5
通讯作者：
Fruchtman, Amnon
中科院分区：
文献类型：
--
作者：
Fruchtman, Amnon
中性耗竭对低温等离子体的稳态有显著影响。最近的理论分析预测了中性耗竭在碰撞和无碰撞状态下的意外影响。在本文中，我们讨论了中性耗竭对在无碰撞中性气体中产生的无碰撞等离子体稳态的影响。中性离子和等离子体只有通过体积电离和壁复合才能耦合。对于一个零质量流的封闭系统，我们得到了等离子体和中性体的密度分布，并推导出了在渐近极限下的耗竭率值。结果表明，在密度最小的地方，无碰撞中性气体的压力最大。这与中性气体被热化的情况相反。对于非零质量流的开放系统，导出了等离子体和中性流剖面的解析表达式。考虑到等离子体推进器的这种配置，我们计算了预期推力、推进剂利用率、比冲和效率。电离的能量成本和后壁能量损失显著降低了效率。
Neutral depletion can significantly affect the steady state of low-temperature plasmas. Recent theoretical analyses predicted unexpected effects of neutral depletion in both collisional and collisionless regimes. In this paper, we address the effects of neutral depletion on the steady state of a collisionless plasma generated in a collisionless neutral gas. The neutrals and the plasma are coupled only through volume ionization and wall recombination. For a closed system with zero mass flow, the density profiles of both plasma and neutrals are found, and values for the rate of depletion at asymptotic limits are derived. It is shown that the pressure of the collisionless neutral gas is maximal where the density is minimal. This is in contrast to the case in which the neutral gas is thermalized. For an open system of a nonzero mass flow, analytical expressions are derived for the profiles of the plasma and the neutral flows. Considering such a configuration for a plasma thruster, we calculate the expected thrust, propellant utilization, specific impulse, and efficiency. The energy cost for ionization and backwall energy losses are shown to significantly reduce the efficiency.