Modeling nanoparticle charge distribution in the afterglow of non-thermal plasmas and comparison with measurements
Modeling nanoparticle charge distribution in the afterglow of non-thermal plasmas and comparison with measurements
复制标题
DOI：
10.1088/1361-6463/abf70c
复制
发表时间：
2021-04
期刊：
影响因子：
--
通讯作者：
Vikram Suresh;Li Li-Li;Joshua Redmond Go Felipe;R. Gopalakrishnan
中科院分区：
文献类型：
--
作者：
Vikram Suresh;Li Li-Li;Joshua Redmond Go Felipe;R. Gopalakrishnan
非热等离子体余辉中的粒子充电通常发生在非中性空间电荷环境中。我们通过将粒子离子碰撞速率常数模型（通过分析使用 Langevin Dynamics (LD) 模拟计算的粒子离子轨迹而开发的）纳入余辉中离子、电子和带电粒子的物种输运方程来建立相同的模型。提出了粒子充电的缩放分析和粒子-离子碰撞速率常数的附加 LD 计算，以将离子静电与热能比 300 和扩散努森数（与气压成反比）的适用范围扩大到 2000。开发的碰撞速率常数模型首先通过将粒子电荷的预测与 Ratynskaia 等人发表的过去 PK-4 活动中静态、非热 DC 等离子体中的测量值进行比较来验证。 (2004 Phys. Rev. Lett. 93 085001) 和 Khrapak 等人 (2005 Phys. Rev. E 72 016406)。比较表明，在~20−150Pa 的气压范围内，半径为 0.6、1.0、1.3 μm 的颗粒在 ±35% 范围内具有良好的一致性。 Sharma 等人 (2020 J. Chemistry D: Appl. Phys. 53 245204) 探测粒子电荷分布的实验使用经过验证的粒子-离子碰撞速率常数模型进行建模，并将计算出的电荷分数与测量结果进行比较。比较表明，余辉中的离子/电子浓度和气体温度严重影响粒子电荷，并且预测通常与测量结果定性一致。除了对建模假设进行严格评估外，还为未来探测余辉充电的实验设计提出了一些建议。
Particle charging in the afterglows of non-thermal plasmas typically take place in a non-neutral space charge environment. We model the same by incorporating particle–ion collision rate constant models, developed in prior work by analyzing particle–ion trajectories calculated using Langevin Dynamics (LD) simulations, into species transport equations for ions, electrons and charged particles in the afterglow. A scaling analysis of particle charging and additional LD calculations of the particle–ion collision rate constant are presented to extend the range of applicability to ion electrostatic to thermal energy ratios of 300 and diffusive Knudsen number (that scales inversely with gas pressure) up to 2000. The developed collision rate constant models are first validated by comparing predictions of particle charge against measured values in a stationary, non-thermal DC plasma from past PK-4 campaigns published in Ratynskaia et al (2004 Phys. Rev. Lett. 93 085001) and Khrapak et al (2005 Phys. Rev. E 72 016406). The comparisons reveal excellent agreement within ±35% for particles of radius 0.6,1.0,1.3 μm in the gas pressure range of ∼20−150Pa . The experiments to probe particle charge distributions by Sharma et al (2020 J. Physics D: Appl. Phys. 53 245204) are modeled using the validated particle–ion collision rate constant models and the calculated charge fractions are compared with measurements. The comparisons reveal that the ion/electron concentration and gas temperature in the afterglow critically influence the particle charge and the predictions are generally in qualitative agreement with the measurements. Along with critical assessment of the modeling assumptions, several recommendations are presented for future experimental design to probe charging in afterglows.