Sheath and dust particle transport in plasmas

等离子体中的鞘层和尘埃粒子传输

• 批准号: RGPIN-2019-04333
• 负责人: Couedel, Lenaic
• 金额: $ 2.48万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=685364
• 关键词: Sheath; dust; particle; transport; plasmas

Plasmas are (weakly) ionised gases consisting of positive ions and free electrons. They can be found everywhere from astrophysical environment (stars, interstellar medium) to energy production and industrial applications (ion implantation, plasma etching, production of nanoparticles, Hall-effect thrusters, fusion devices, etc). In devices used for laboratory experiments or industrial applications, plasmas are confined and bound by the walls of the vessel. The plasma-wall interface (referred to as the plasma sheath) is a narrow region in which the quasi-neutrality condition applicable to bulk plasmas does not hold. The sheath plays a major role in determining the plasma discharge parameters and affects the flows of particles and the heat to the surface. Plasma-surface (or plasma-wall) interactions are thus common to all laboratory plasma systems.***Plasmas containing large solid particles (dusts) are called dusty plasmas. Due to interactions with the plasma electrons and ions, dusts acquire net electric charges. In laboratory low-temperature plasmas, dusts are usually charged negatively due to high electron mobility. Sheaths form in the vicinity of dusts affecting plasma species fluxes on dust surfaces and dust transport. Understanding dust interactions with the surrounding plasma requires a good comprehension of sheath formation around small floating solid grains and an accurate knowledge of local plasma parameters (electric fields, ion velocity distribution function). Hence, the problem can be widened to a more general study of plasma-surface interactions (PSI), plasma-dust interactions being only one aspect of it. While sheath formation in front of conducting surface in non-magnetised collision-less low-temperature plasma is known, sheath formation in front of surfaces emitting particles or in magnetised plasma is still poorly understood.***The long term objectives of the proposed research are to gain deep understanding on sheath formation and on the transport and dynamics of dust particles in plasmas. They can be formulated under two major themes:***(i) Electric fields and Ion velocity distribution function in the sheath,***(ii) Dynamics of dust particles in plasmas.***Short term objectives include:***(1) Studies of sheaths parameters in front of different surfaces using state-of-the-art laser based diagnostics;***(2) Dynamics and transport of dusts in conventional gas discharges;***(3) Dynamics, transport and lifetime of dust particles in tokamaks;***(4) Theoretical and numerical studies on sheath formation in front of emissive surfaces in plasmas.***HQPs will be involved in all steps of this research program which focus on a highly applicable area of plasma physics and technology.

等离子体是由正离子和自由电子组成的(弱)电离气体。从天体物理环境(恒星、星际介质)到能源生产和工业应用(离子注入、等离子体刻蚀、生产纳米粒子、霍尔效应推进器、聚变装置等)，它们随处可见。在用于实验室实验或工业应用的设备中，等离子体被限制和约束在容器的壁上。等离子体-壁界面(称为等离子体鞘)是一个狭窄的区域，适用于大块等离子体的准中性条件不适用于该区域。鞘层在决定等离子体放电参数中起着重要作用，它影响着粒子的流动和表面的热量。因此，等离子体-表面(或等离子体-壁)的相互作用在所有实验室等离子体系统中都是常见的。*含有大的固体颗粒(尘埃)的等离子体称为尘埃等离子体。由于与等离子体电子和离子的相互作用，尘埃获得了净电荷。在实验室低温等离子体中，由于高电子迁移率，粉尘通常带负电荷。在尘埃附近形成鞘层，影响尘埃表面的等离子体组分通量和尘埃的传输。要了解尘埃与周围等离子体的相互作用，需要对漂浮的小固体颗粒周围的鞘形成有很好的理解，并准确了解局部等离子体参数(电场、离子速度分布函数)。因此，这个问题可以扩大到对等离子体-表面相互作用(PSI)的更一般的研究，等离子体-尘埃相互作用只是其中的一个方面。虽然在非磁化无碰撞低温等离子体中导体表面前方的鞘层形成是已知的，但在发射粒子的表面或在磁性等离子体中的鞘层形成仍然知之甚少。*拟议研究的长期目标是深入了解鞘形成以及尘埃粒子在等离子体中的输运和动力学。短期目标包括：*(1)利用最先进的激光诊断技术研究不同表面前的鞘层参数；*(2)常规气体放电中粉尘的动力学和输运；*(3)托卡马克中尘埃粒子的动力学、输运和寿命；*(4)等离子体中发射面前鞘层形成的理论和数值研究。*HQP将参与本研究计划的所有步骤，这些步骤专注于等离子体物理和技术的一个高度适用的领域。