Modeling Ion Extraction from First Toroidal Electron-Cyclotron-Resonance Ion Source

该项目将使用计算建模来测试用于粒子加速器的新型离子源的可行性，粒子加速器是科学界最普遍的工具之一，其用途从基础研究到应用到癌症治疗、材料科学和纳米制造。世界各地的几个粒子加速器将离子加速到非常高的速度，接近光速。例如，欧洲核子研究中心的大型强子对撞机加速铅离子；布鲁克海文的相对论重离子对撞机对撞金离子，以重建和研究大爆炸后前10微秒的物理。所有这些都需要一个离子源。它们还要求离子具有高电荷，即从尽可能多的电子中剥离。而且它们每单位时间需要很多离子。这里提出的新概念建立在一种名为电子回旋共振离子源的离子源上，但它是受核聚变实验启发的一种新的甜甜圈形状的几何结构。在这个项目中调查的这种来源，将大大改善现有的那些特征。多年来，人们一直试图增加电子回旋共振离子源(ECRIS)等离子体的密度、温度和限制时间，从而产生更高电荷的离子。在聚变等离子体中，为了提高聚变反应性，人们迫切需要增加几乎相同数量的‘三倍积’。在这个类比的启发下，这个项目将数值地探索环形限制的离子源相关性，并将其与线性ECRIS范例进行比较，线性ECRIS范例是磁镜和六极场的组合。乍一看，环形几何形状非常吸引人。它更好地利用了磁场，环形ECRIS可以被加热并被限制在相同的磁场中。另一方面，离子提取不会像从线性ECRIS中那样直接。该项目将通过比较静磁、静电和漂移提取技术来从数值上解决这一问题。要研究的第二个方面是线性ECRIS和环形ECRIS中的输运和限制的比较：虽然聚变研究中众所周知的H，D和T的热离子在环形装置中比线性装置更好地限制，但对于重物种的冷碰撞离子却不能保证同样的情况。这两个问题将通过利用辛积分器以数字方式跟踪几个“测试离子”的轨道，并让这些离子根据分布函数相互碰撞以及与背景等离子体中的离子和电子发生碰撞来解决。

This project will use computational modeling to test the feasibility of a novel source of ions for particle accelerators, one of the most ubiquitous tools within the scientific community, with uses ranging from fundamental research to applications to cancer therapy, materials science, and nanofabrication. Several particle accelerators worldwide accelerate ions to very high velocities, approaching the speed of light. For example, the Large Hadron Collider at CERN accelerates ions of lead; the Relativistic Heavy Ion Collider at Brookhaven collided ions of gold to recreate and study the physics of the first 10 microseconds after the Big Bang. All require a source of ions. They also require the ions to have high charge, that is, to be stripped from as many electrons as possible. And they require many ions per unit time. The new concept proposed here builds on a type of ion source called an Electron Cyclotron Resonance Ion Source, but in a new doughnut-shaped geometry inspired by nuclear fusion experiments. Such a source, investigated within this project, would have greatly improved characteristics over those presently available. There have been attempts over the years to increase the density, temperature and confinement-time of Electron Cyclotron Resonance Ion Source (ECRIS) plasmas, resulting in ions of higher charge. In fusion plasmas there is a push to increase the 'triple product' of nearly the same quantities for the sake of increasing the fusion reactivity. Inspired by this analogy, this project will numerically explore the ion-source-relevance of toroidal confinement, and compare it with the linear ECRIS paradigm, a magnetic mirror combined with an hexapolar field. At a first glance, the toroidal geometry is highly attractive. It makes a better use of the magnetic field, where toroidal ECRIS could be heated and confined at the same field. On the other hand, ion extraction will not be as straightforward as from a linear ECRIS. This project will numerically address this aspect by comparing magnetostatic, electrostatic and drift-based extraction techniques. The second aspect to investigate is how transport and confinement compare in a linear and a toroidal ECRIS: while hot ions of H, D and T are well-known from fusion research to be better confined in toroidal devices than linear ones, the same is not guaranteed for cold collisional ions of heavy species. Both problems will be addressed by numerically tracing the orbits of several "test ions", by means of symplectic integrators, and by letting these ions undergo collisions - according to a distribution function - with each other and with ions and electrons from the background plasma.