Modeling the influence of anode-cathode spacing in a pulsed discharge nozzle
Modeling the influence of anode-cathode spacing in a pulsed discharge nozzle
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DOI：
10.1016/j.sab.2005.08.012
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发表时间：
2005-11
期刊：
影响因子：
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通讯作者：
B. Broks;Wjm Wouter Brok;J. Remy;van der J.J.A.M. Mullen;A. Benidar;L. Biennier;Farid Salama
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文献类型：
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作者：
B. Broks;Wjm Wouter Brok;J. Remy;van der J.J.A.M. Mullen;A. Benidar;L. Biennier;Farid Salama
脉冲放电喷嘴（PDN）是一种光谱化学源，其设计用于在实验室中的天体物理相关环境中产生和冷却分子离子，并具有有限的碎片。为了更好地了解PDN，并优化PDN源中分子离子和自由基的产率，通过放电模型进行了极间距离对等离子体特性影响的参数研究，提供了等离子体的定性和定量的图片。我们模型的电子密度和能量，以及氩离子和亚稳原子数密度为各种电极间的距离。结果表明，增加极间距离并没有显着影响等离子体在阴极和阳极。然而，在电极之间形成正柱，其长度随着电极间距离的增加而增加。这是TON是辉光放电的额外证据。这个正柱对亚稳态氩原子的形成没有显著的贡献。由于亚稳态氩被认为是通过中性分子前体的潘宁电离形成分子离子的主要试剂，因此预期增加电极间距离不会带来任何益处。事实上，柱中分子的电子碰撞解离甚至可能使源对于较长的柱长度效率较低。这里提出的模拟提供了物理洞察星际物种类似物在实验室实验中的特点。
The pulsed discharge nozzle (PDN) is a spectrochemical source that is designed to produce and cool molecular ions in an astrophysically relevant environment in the laboratory with limited fragmentation. In order to gain a better understanding of the PDN and to optimize the yield of molecular ions and radicals in the PDN source, a parameter study of the influence of the interelectrode distance on the plasma properties is carried out by means of a discharge model, providing a qualitative as well as a quantitative picture of the plasma. We model the electron density and energy, as well as the argon ion and metastable atom number density for various interelectrode distances. The results reveal that increasing the interelectrode distance does not significantly influence the plasma at the cathode and at the anode. However, a positive column forms between the electrodes, which increases in length as the interelectrode distance increases. This is an additional evidence that the PDN is a glow discharge. This positive column does not contribute significantly to the formation of metastable argon atoms. Because metastable argon is thought to be the primary agent in the formation of molecular ions through Penning ionization of the neutral molecular precursor there is no benefit to be expected from an increase of the interelectrode distance. In fact, electron impact dissociation of the molecules in the column might even make the source less efficient for longer column lengths. The simulations presented here provide physical insight into the characteristics of interstellar species analogs in laboratory experiments.