Kuppart Kristian, Vigonski Simon, Aabloo Alvo, Wang Ye, Djurabekova Flyura, Kyritsakis Andreas, Zadin Veronika
Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia.
Helsinki Institute of Physics and Department of Physics, University of Helsinki, P.O. Box 43 (Pehr Kalms gata 2), FI-00014 Helsinki, Finland.
Micromachines (Basel). 2021 Sep 29;12(10):1178. doi: 10.3390/mi12101178.
We present a credible mechanism of spontaneous field emitter formation in high electric field applications, such as Compact Linear Collider in CERN (The European Organization for Nuclear Research). Discovery of such phenomena opens new pathway to tame the highly destructive and performance limiting vacuum breakdown phenomena. Vacuum breakdowns in particle accelerators and other devices operating at high electric fields is a common problem in the operation of these devices. It has been proposed that the onset of vacuum breakdowns is associated with appearance of surface protrusions while the device is in operation under high electric field. Moreover, the breakdown tolerance of an electrode material was correlated with the type of lattice structure of the material. Although biased diffusion under field has been shown to cause growth of significantly field-enhancing tips starting from initial nm-size protrusions, the mechanisms and the dynamics of the growth of the latter have not been studied yet. In the current paper we conduct molecular dynamics simulations of nanocrystalline copper surfaces and show the possibility of protrusion growth under the stress exerted on the surface by an applied electrostatic field. We show the importance of grain boundaries on the protrusion formation and establish a linear relationship between the necessary electrostatic stress for protrusion formation and the temperature of the system. Finally, we show that the time for protrusion formation decreases with the applied electrostatic stress, we give the Arrhenius extrapolation to the case of lower fields, and we present a general discussion of the protrusion formation mechanisms in the case of polycrystalline copper surfaces.
我们提出了一种在高电场应用中自发形成场发射体的可靠机制，例如欧洲核子研究组织（CERN）的紧凑型直线对撞机。此类现象的发现为控制极具破坏性且限制性能的真空击穿现象开辟了新途径。在粒子加速器以及其他在高电场下运行的设备中，真空击穿是这些设备运行过程中的常见问题。有人提出，真空击穿的起始与设备在高电场下运行时表面突起的出现有关。此外，电极材料的击穿耐受性与材料的晶格结构类型相关。尽管已表明场致偏置扩散会导致从初始纳米尺寸的突起开始生长出显著增强场的尖端，但后者生长的机制和动力学尚未得到研究。在本文中，我们对纳米晶铜表面进行了分子动力学模拟，并展示了在施加的静电场对表面施加的应力作用下突起生长的可能性。我们展示了晶界在突起形成中的重要性，并建立了突起形成所需的静电应力与系统温度之间的线性关系。最后，我们表明突起形成的时间随施加的静电应力而减少，我们对低场情况进行了阿仑尼乌斯外推，并对多晶铜表面情况下的突起形成机制进行了一般性讨论。
