Experiments to investigate parametric wave interaction in Helicon Plasma

等离子体是一种由粒子之间的集体相互作用主导的物质状态，由远程电磁力主导。至少有两种（负电子和正离子）。两种粒子的电荷使它们各自对电磁场（如光、微波和无线电波）作出反应，但方向相反，速度也大不相同。它们对频率接近自然等离子体振荡频率的波的反应尤其明显，这是由任何静态磁场的大小和方向、粒子的数量密度和质量的复杂组合决定的。它们可以吸收频率为“共振”的波能，并反射频率为“截止”的波能。这些效应经常在重要的实验室实验和应用中用于加热或测量等离子体，例如通过聚变反应（磁约束）和工业加工产生能量的新技术，天然等离子体对现代能量分配、通信和导航系统的影响是重要的。在工业加工中，等离子体物理是半导体加工和现代数字技术的基础。在核聚变能源方面，其潜在影响可能是深远的，可以实现几乎无限的能源供应，解决围绕使用化石燃料的严重环境问题，而不会产生长期放射性副产品。参数耦合是指当两个或多个波的频率与一个固有等离子体振荡频率相关时，它们交换能量的多波相互作用。这种过程最近被发现在惯性约束聚变的激光等离子体相互作用中造成困难，同时为将能量传递到惯性和磁约束聚变等离子体的新的更灵活的方式提供了令人兴奋的潜力。随着这些领域的研究从基础实验转向应用规模设备，这些新技术将变得越来越重要。该项目将进行基础研究，调查微波频率范围内的这些相互作用。微波范围对此类研究具有吸引力，因为为一系列应用开发的强大源和放大器很容易获得，可以非常精确地控制，增强了研究等离子体物理动力学的能力，同时开创性的研究指向微波发生器实现非常高水平的归一化功率。微波-等离子体耦合与工业加工和磁约束聚变等离子体物理直接相关，在后者的情况下，热波相互作用可能在加热下一代反应堆中发挥特殊作用，可能高度依赖电磁波将热量和电流引入反应堆。研究了两束精确控制的微波束（~10cm ~ 3cm波长）在（弱到强）磁化的螺旋等离子体中电子和离子的等离子体（类声）振荡、电子和离子的回旋振荡以及包括准声运动和回旋运动在内的混合振荡的耦合。随着随机加热的影响，高振幅波中粒子的“准随机”运动使有效温度迅速增加。

Plasma is a state of matter dominated by collective interactions between particles, dominated by long range electro magnetic forces. There are a minimum of two species (negative electrons and positive ions). The charge of both types of particle make them each respond to electromagnetic fields (such as light, microwave and radio waves), but in opposite directions, and at very different rates. They particularly respond to waves at frequencies close those of natural plasma oscillations, determined by complicated combinations of the magnitude and direction of any static magnetic field, the number density and mass of the particles. They can absorb wave energy at frequencies called 'resonances', and reflect wave energy at frequencies called 'cut-offs'. These effects are often used to heat or measure plasmas in important laboratory experiments and applications, such as new techniques for energy production through fusion reactions (magnetically confined) and industrial processing, and natural plasma is important through its impact on modern energy distribution, communication and navigation systems. In industrial processing, plasma physics underpins semiconductor processing and hence modern digital technology. In fusion energy the impact potential can be profound, enabling an almost unlimited supply of energy, addressing serious environmental concerns surrounding the use of fossil fuel, with no long term radioactive byproducts.Parametric coupling refers to a multi-wave interaction where two or more waves exchange energy when their frequencies are related by a natural plasma oscillation frequency. Such processes have recently been found to cause difficulties in laser-plasma interactions for inertial confinement fusion, whilst at the same time offering exciting potential for new and more flexible ways of delivering energy into both inertially and magnetically confined fusion plasmas. Such new techniques will be increasingly important as research in these fields moves from fundamental experiments to application scale equipment. This project will undertake fundamental research investigating these interactions in the microwave frequency range. The microwave range is attractive for such research since powerful sources and amplifiers, developed for a range of applications, are readily available, can be very precisely controlled, enhancing the ability to investigate the plasma physics dynamics, whilst groundbreaking research points towards microwave generators achieving very high levels of normalised power. Microwave-Plasma coupling is directly relevant to industrial processing and magnetic confinement fusion plasma physics, and in the latter case beat wave interaction may have a special role to play in heating next generation reactors, likely to be highly dependent on EM waves to introcude heat and current into the reactor.The coupling of two precisely controlled microwave beams (~10cm to 3cm wavelength) in a (weakly to strongly) magnetised helicon plasma by plasma (acoustic-like) oscillations in the electrons and ions, cyclotron oscillation of the electrons and ions and hybrid oscillations including both quasi-acoustic and cyclotron motion will be investigated, as will the effects of stochastic heating where 'quasi-random' motion of particles in high amplitude waves gives very rapid increase in effective temperature.