Kinetic Effects in Nonlinear Plasma Waves

该奖项支持一个实验、模拟和理论项目，研究一种新型的振幅大的等离子体波的不稳定性——在带电粒子自由相互作用的气体中的波。这些研究将集中在以几乎恒定的波速传播的波浪中似乎主导这种不稳定性的新型“动力学”效应上并对其进行表征。这种波在自然产生的等离子体和实验室等离子体中都是普遍存在的。新的不稳定机制非常简单和通用，因此可以应用于一系列场景，包括空间等离子体和聚变等离子体发电。实验将在非中性等离子体上进行，利用具有广泛操作制度和诊断的电子陷阱和离子陷阱。这些系统的简单性使得理论和实验之间的理解深度和比较精度成为可能，这对于复杂几何中的准中性等离子体来说是很少可能的。目的是验证理论的适用性，并在需要时激发新的理论。最近的分析发现，令人惊讶的是，标准流体理论不足以描述近声Trivelpiece-Gould [TG]等离子体波的参数不稳定性。一种新的动力学不稳定机制，涉及被困在波谷中的一小部分等离子体，将被研究并应用于理解在热重波和电子声波中观察到的参数不稳定性。实验和模拟将用于表征波作用下的粒子分布，包括捕获的粒子，以便与理论直接比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports a program of experiments, simulations, and theory on a new type of instability of large amplitude plasma waves - waves in a gas of freely interacting electrically charged particles. The studies will focus on and characterize novel 'kinetic' effects that appear to dominate this instability in waves that propagate with nearly constant wave speed. Such waves are ubiquitous in both naturally-occurring and laboratory plasmas. The new instability mechanism is quite simple and general, and therefore has application to a range of scenarios, including space plasmas and fusion plasmas for power generation.Experiments will be performed on non-neutral plasmas, utilizing an electron trap and an ion trap with a broad range of operating regimes and diagnostics. The simplicity of these systems allows a depth of understanding and a precision of comparison between theory and experiment which is rarely possible for quasi-neutral plasmas in complex geometry. The goal is to verify applicability of the theory, and to stimulate new theory where needed. Recent analysis has found that, surprisingly, standard fluid theory is inadequate to describe parametric instability for near-acoustic Trivelpiece-Gould [TG] plasma waves. A new kinetic instability mechanism, involving a small fraction of plasma that is trapped in the wave troughs, will be studied and applied to understand parametric instabilities observed both in TG waves and in electron-acoustic waves. Experiments and simulations will be used to characterize the particle distribution under the action of the wave, including trapped particles, for direct comparison to theory.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.