Interaction of electrons with the walls confining a plasma

电子与限制等离子体的壁的相互作用

• 批准号: 495729137
• 负责人: Privatdozent Dr. Franz Xaver Bronold
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/495729137?language=en
• 关键词: Interaction; electrons; walls; confining; plasma

Man-made plasmas are in contact with solids. In fact, it is the plasma-solid interaction, which is the core of many technological plasma applications. Not in all plasma devices, however, is the plasma-solid interaction beneficial. For instance, to keep fusion plasmas, Hall thrusters, and miniaturized dielectric barrier discharges stable, the interaction with the solid, and hence the plasma fluxes onto the walls, should be minimized. Since the fluxes depend on the electric response of the plasma-wall interface, resulting from charge-transferring atomic collisions and the interaction of electrons from the plasma with the wall, controlling the latter is of technological interest. The interaction typically occurs at energies below 50~eV, an energy range which has not been widely addressed. Little is thus quantitatively known about the coefficients characterizing it. In this project, we develop a theoretical tool for studying the interaction of low-energy electrons with solids, as it applies to plasma devices, and use it to start building up - for homogeneous and coated walls - a data base for electron emission yields and their complements, the electron sticking coefficients. To counter the lack of crystallographic information about the walls, we base the calculations on a Jellium-type model, augmented by the most generic crystal effects, coherent Bragg scattering on planes coplanar to the interface and incoherent elastic scattering on ion cores. Describing moreover the scattering and physical processes included in a manner that depends only on a few easily accessible parameters, we get a surface and scattering model applicable to different classes of materials. It is used, within an invariant embedding principle for the backscattering function, summing up the backscattering trajectories arising from the interaction of the primary electron with the excitations and imperfections of the solid, to calculate the yield for secondary electron emission as well as the electron sticking coefficient. The embedding equations for backscattering from homogeneous and coated walls are derived and solved numerically with strategies developed for interface transport in nuclear physics. Using them, we tap the full potential of the embedding approach for quantifying the interaction of low-energy electrons with solids, a prerequisite for future efforts to optimize plasma devices by judiciously choosing the wall materials.

人造等离子体与固体接触。事实上，它是等离子体-固体相互作用的核心，这是许多等离子体技术应用的核心。然而，并不是在所有的等离子体设备中，等离子体-固体相互作用都是有益的。例如，为了保持聚变等离子体、霍尔推进器和小型化介质阻挡放电的稳定，应该最大限度地减少与固体的相互作用，从而使流入墙壁的等离子体通量降至最低。由于通量取决于电荷转移原子碰撞引起的等离子体-壁界面的电响应以及来自等离子体的电子与壁的相互作用，因此控制后者具有重要的技术意义。这种相互作用通常发生在能量低于50 eV的地方，这个能量范围还没有得到广泛的解决。因此，人们对表征它的系数知之甚少。在这个项目中，我们开发了一个理论工具来研究低能电子与固体的相互作用，因为它应用于等离子体设备，并使用它来开始建立-对于均匀的和涂覆的墙-电子发射产额及其补充的数据库，电子粘着系数。为了应对缺乏关于壁面的结晶学信息，我们基于凝胶型模型，增加了最常见的晶体效应，在与界面共面的平面上的相干布拉格散射，以及在离子核上的非相干弹性散射。此外，我们还以一种只依赖于几个容易获得的参数的方式描述了包含的散射和物理过程，得到了适用于不同类型材料的表面和散射模型。在背向散射函数的不变嵌入原理下，它用来总结初级电子与固体的激发和缺陷相互作用产生的背向散射轨迹，以计算二次电子发射产额和电子粘着系数。推导了均匀壁和涂层壁后向散射的嵌入方程，并用核物理中的界面输运策略进行了数值求解。使用它们，我们挖掘了嵌入方法的全部潜力，用于量化低能电子与固体的相互作用，这是未来通过明智地选择壁材来优化等离子体设备的先决条件。