Experimental Study of Ion Species Separation in Multi-Component Plasma Shocks

在空气中经常观察到的冲击波也发生在高温气体中，在那里电子从离子中解放出来，形成等离子体。该项目将通过等离子体射流与静止等离子体碰撞来实验研究冲击波。当等离子体由不同电荷和质量的物质组成时，等离子体特性在冲击波中的快速变化会导致这些物质的分离，从而使激波结构进一步复杂化。理解这些场景中的物理现象对于进一步理解天体物理现象非常重要，包括II型超新星爆炸，以及在惯性约束聚变实验中发生的内爆的物理现象。该项目将收集详细的实验数据，描述高速多种类等离子体射流和停滞等离子体之间的碰撞，在一个实验中，预计冲击厚度足够大，可以很容易地被诊断仪器观察到。本项目旨在通过实验确定多组分等离子体在参数空间中的冲击，从而有可能解决离子冲击层的结构。在平均自由路径小到足以使射流相互作用发生碰撞，但又大到足以在几百个平均自由路径上尝试诊断激波结构的情况下，将研究多种等离子体与停滞等离子体的碰撞相互作用。该项目的范围将是识别在这些相互作用中形成的激波，并研究参数空间，以确认观察到的激波是否存在于多离子等离子体中。线性等离子体电枢轨道炮将发射一系列多离子等离子体射流。在第一股射流在屏障上停滞后不久，第二股射流将以足以在等离子体中引发激波的速度与停滞的等离子体相遇。一套诊断方法将用于捕获表明存在个别等离子体的数据。将采用的诊断方法包括：(i)高空间分辨率测量光谱学，用于定位激波前沿离子的发射；（ii）多弦干涉测量法，将与光谱学结合使用，推断激波和非激波区域的电荷状态和电子温度。本研究所寻求的实验观察有可能揭示由离子种类碰撞扩散引起的从未观察到的激波结构。这可以增强对天体物理现象和惯性聚变等离子体物理学的理解。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。

Shock waves, frequently observed in air, also occur in high temperature gases where electrons have been liberated from ions, forming a plasma. This project will experimentally study shock waves by colliding plasma jets with stagnant plasma. When the plasma is composed of species of differing electric charge and mass, the rapid change in plasma properties across the shock wave can cause separation of these species, further complicating the shock structure. Understanding the physics present in these scenarios is important to furthering the understanding of astrophysical phenomena, including Type II supernova explosions, as well as the physics of implosions that occur in inertial-confinement fusion experiments. This project will collect detailed experimental data characterizing collisions between high-velocity multi-species plasma jets and stagnant plasma in an experiment where shock thickness is predicted to be large enough to be readily observable by diagnostic instruments.This project aims to experimentally identify shocks in multi-component plasmas in a parameter space where it is possible to resolve the structure of the ion shock layer. Interactions of collisional multi-species plasma jets with stagnated plasma will be studied in a regime where the mean-free-path is small enough for the jet interaction to be collisional yet large enough to attempt diagnosis of the shock structure over a few hundred mean-free-paths. The scope of the project will be to identify shocks formed during these interactions and investigate the parameter space to confirm whether the observed shocks are present in multi-ion-species plasmas. A series of multi-ion-species plasma jets will be emitted by a linear plasma-armature railgun. Shortly after the first jet stagnates against a barrier, the second jet will encounter the stagnant plasma at velocities sufficient to drive a shock in the plasma. A suite of diagnostics will be used to capture data indicating the presence of individual plasma species. The diagnostics that will be employed include (i) high spatial resolution survey spectroscopy to locate emission from ion species at the shock front and (ii) multi-chord interferometry which will be used in conjunction with spectroscopy to infer charge state and electron temperature in the shocked and unshocked regions. The experimental observations sought by this research have the potential to shed light on never-before-observed shock structures caused by collisional diffusion of ion species. This could enhance understanding of astrophysical phenomena and the physics of inertial fusion plasmas.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.