Nonlinear microwave interactions and induced turbulence in magnetised laboratory plasma

实验室等离子体在当代高价值、高科技产业中得到越来越多的利用。与此同时，利用聚变能以环境安全、无碳的方式提供世界的能源需求可能是基于磁约束等离子体。用于加热聚变等离子体的主要方法之一是注入大幅度微波并通过模式转换或通过非线性过程在等离子体中激发各种共振。例如，电磁波与动力学模式（如电子伯恩斯坦波）的耦合是为MAST升级球形托卡马克提出的加热机制和诊断之一。了解诱导的湍流和由此产生的电流和运输是一项具有挑战性的任务。磁约束等离子体中不同长度和时间尺度之间的相互作用，以及小尺度湍流如何通过波粒相互作用影响等离子体中的大尺度电流和输运，是一个悬而未决的问题。该项目旨在对大振幅微波与磁化等离子体和光束之间的非线性相互作用进行理论和数值研究，并诊断等离子体中的湍流过程和输运，通过数值模拟和理论模型的支持。原子、光束和等离子体小组在使用线性等离子体装置进行实验室实验方面具有丰富的经验，以研究微波和等离子体之间的相互作用以及导致辐射逸出等离子体的动力学不稳定性。ABP集团还率先使用相对论电子束产生微波，其波长从厘米到亚毫米不等。这些微波将被用作诊断和研究波等离子体相互作用，包括各种散射不稳定性。该项目将与卡勒姆聚变能中心（CCFE）密切合作，在那里将进行实验诊断和解释。

Laboratory plasmas are being increasingly exploited in contemporary high-value, high-technology industries. At the same time, the harnessing of fusion energy to provide the world's energy needs in an environmentally safe, carbon-free way may be based on magnetically confined plasmas. One of the major methods used to heat fusion plasmas is to inject large amplitude microwaves and to excite various resonances in the plasma via mode conversion or via nonlinear processes. For example, the coupling of electromagnetic waves to kinetic modes such as electron Bernstein waves is one of the heating mechanisms and diagnostics proposed for the MAST Upgrade spherical Tokamak. To understand the induced turbulence and resulting currents and transport is a challenging task. An open question is the interplay between different length- and time-scales in magnetically confined plasma, and how small-scale turbulence influences large-scale currents and transport in the plasma via wave-particle interactions.The project aims to undertake a theoretical and numerical investigation of nonlinear interaction between large amplitude microwaves and magnetised plasma and beams, as well as diagnostics of turbulent processes and transport in the plasma, supported by numerical simulations and theoretical modelling. The Atoms, Beams and Plasmas group has extensive experience in laboratory experiments using a linear plasma device, to study the interaction between microwaves and plasmas, and kinetic instabilities leading to radiation escaping the plasma. The ABP group has also pioneered microwave generation using relativistic electrons beams, with waves ranging from centimetres to sub-millimetres. These microwaves will be used both as a diagnostic and for studying wave-plasma interactions, including various scattering instabilities. The project will be carried out in close collaboration with the Culham Centre for Fusion Energy (CCFE), where diagnostics from experiments will be carried out and interpreted.