Unraveling the Link Between Radio-frequency Wave Propagation and High Ionization Efficiency of Helicon Waves

揭示射频波传播与螺旋波高电离效率之间的联系

• 批准号: 1903316
• 负责人: Oliver Schmitz
• 金额: $ 45万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903316&HistoricalAwards=false
• 关键词: Unraveling; Link; Between; Radio; frequency

The focus of this research project is on the physics of generating very uniform plasmas for future particle accelerator applications. Plasmas, the fourth state of matter, are of importance for many science and industrial applications, one of which is as a medium for next generation particle accelerators. The electrical features of a plasma allow for high accelerating electric field gradients which are up to a factor of a hundred greater than in existing solid-state-based particle accelerators. This can translate into much more compact, energetic, and cheap accelerators. At CERN in Geneva, Switzerland, the AWAKE project aims to use a plasma column as a medium for a next generation electron accelerator based on the wakefield acceleration concept. This grant will support research aimed at improving the understanding of how a plasma column can be formed and tuned for the requirements in the AWAKE accelerator application. The understanding of such plasma sources is also of direct relevance to a variety of other applications, such as plasma processing in industry and life-sciences, plasma generation for fusion-based neutron sources, and development of a wind-tunnel experiment for astrophysical plasma turbulence.The specific method used for plasma generation in this project is the so-called Helicon wave. These are radio-frequency waves in the whistler regime, known broadly for reliable generation of magnetized plasmas at high density with very high ionization fractions. In the magnetic field regimes of 10^3 Gauss, these waves are canonically called Helicons. They are characterized by a transition from an inductively coupled, low density and low ionization regime into a regime of high density and almost complete gas ionization. This transition into the helicon regime and the ionization dynamics in this regime are not yet fully understood. This is linked to the application of a plasma as the medium for particle acceleration. This application requires unprecedented levels of homogeneity in the plasma density in the direction of the accelerated particle beam path. The goal of this research is to resolve the helicon transition and understand the ionization dynamics during the transition and shortly afterwards. Plasma diagnostics based on analyzing the light emitted from the plasma will be used to understand the plasma axial homogeneity and methods of active, local gas injection will be used to gain control of the axial plasma density.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.

这个研究项目的重点是为未来的粒子加速器应用产生非常均匀的等离子体的物理学。等离子体是物质的第四种状态，对许多科学和工业应用都具有重要意义，其中之一就是作为下一代粒子加速器的介质。等离子体的电学特性允许高加速电场梯度，这比现有的基于固态的粒子加速器高出100倍。这可以转化为更紧凑、更有活力、更便宜的加速器。在瑞士日内瓦的欧洲核子研究中心，觉醒项目旨在使用等离子体柱作为基于尾场加速概念的下一代电子加速器的介质。这笔赠款将支持旨在提高对如何形成和调整等离子体柱以满足唤醒加速器应用要求的理解的研究。对这类等离子体源的了解还与其他各种应用直接相关，如工业和生命科学中的等离子体处理，聚变中子源的等离子体产生，以及天体物理等离子体湍流风洞实验的发展。本项目中用于产生等离子体的具体方法是所谓的螺旋波。这些是哨声区域的射频波，以可靠地产生高密度、高电离分数的磁化等离子体而广为人知。在10^3高斯的磁场范围内，这些波被经典地称为螺旋子。它们的特征是从电感耦合、低密度和低电离区域过渡到高密度和几乎完全的气体电离区域。人们还没有完全了解这种向螺旋角系统的转变以及在这个系统中的电离动力学。这与应用等离子体作为粒子加速的媒介有关。这种应用要求加速粒子束路径方向上的等离子体密度具有前所未有的均匀度。这项研究的目的是解决螺旋跃迁，并了解跃迁过程中和之后不久的电离动力学。基于分析等离子体发出的光的等离子体诊断将用于了解等离子体的轴向均匀性，并将使用主动、局部气体注入的方法来获得对轴向等离子体密度的控制。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Discharge Directionality and Dominance of Right-Handed Modes in Helicon Plasmas due to Radial Electron Density Gradients

径向电子密度梯度导致的螺旋等离子体中右手模式的放电方向性和优势

• 发表时间: 2022
• 期刊: arXivorg
• 作者: Granetzny, Marcel;Zepp, Michael;Schmitz, Oliver
• 通讯作者: Schmitz, Oliver

Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence

• DOI: 10.1063/1.5129232
• 发表时间: 2020-04-01
• 期刊: PHYSICS OF PLASMAS
• 影响因子: 2.2
• 作者: Green, Jonathan;Schmitz, Oliver;Zepp, Michael
• 通讯作者: Zepp, Michael

Construction of a linear plasma device for studying helicon plasmas relevant to plasma-wakefield accelerators

• DOI: 10.1088/1361-6595/ab7852
• 发表时间: 2020-04
• 期刊: Plasma Sources Science and Technology
• 影响因子: 3.8
• 作者: J. Green;O. Schmitz