Continuous-Wave Laser Thomson Scattering Diagnostic for Low Temperature Plasmas

本项目旨在开发一种新的诊断方法来定量研究低温等离子体中的电子居群。等离子体通常被称为物质的第四态，是一种含有电子和离子等带电物质的气体。低温等离子体也含有高能原子和分子，被称为自由基，可以实现许多技术应用。低温等离子体的特性在很大程度上是由电子控制的，等离子体科学的一个持续挑战是开发诊断技术来测量电子的温度和数量密度。目前的项目解决了这一需求，通过发展诊断，被称为连续波激光汤姆逊散射（CW LTS），定量测量电子。在连续波LTS中，高功率激光束照射待研究的等离子体，激光光子被等离子体电子弹性散射（就像碰撞的台球）。然后检测到散射的光子，从而推断出等离子体的电子特性。该项目将有利于低温等离子体的基础研究和技术应用，包括半导体工业的等离子体处理、空间探索的等离子体推进器和大气压等离子体。该项目还旨在吸引代表性不足的群体的学生参与二氧化碳激光演示的开发，以便向当地K-12学生推广。该项目旨在开发一种基于连续波（CW）、大功率（kW）光源的激光汤姆逊散射（LTS）新模式，与传统的脉冲激光系统相比，实现更高的散射计数和改进的检测极限。由于信号流是连续的，CW LTS方法将尝试将LTS从测量时间平均电子参数推进到捕获高达~10-100 kHz的时间分辨动态。这将代表LTS在研究等离子体动力学（如脉冲放电中的电离和重组）、等离子体波和振荡（如霍尔效应推进器中的呼吸模式）方面取得了前所未有的强大进展。诊断的进展将在出版物和会议上分享，并将整合到科罗拉多州立大学的本科和研究生课程中。来自代表性不足的少数群体的学生将被寻求参与该项目，以进行研究生论文研究和本科生研究经验。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 project will aim to develop a novel diagnostic to quantitatively study electron populations in a low temperature plasma. Plasma, often referred to as the fourth-state of matter, is a gas that contains charged species such as electrons and ions. Low temperature plasmas that also contain energetic atoms and molecules, referred to as radicals, can enable many technological applications. The properties of low temperature plasmas are largely governed by electrons and an ongoing challenge in plasma science has been to develop diagnostic techniques to measure the temperature and number density of electrons. The present project addresses this need through the development of a diagnostic, referred to as continuous-wave Laser Thomson scattering (CW LTS), to quantitatively measure the electrons. With CW LTS, a high-power laser beam illuminates the plasma to be studied and the laser light photons are elastically scattered by the plasma electrons (like colliding billiard balls). The scattered photons are then detected allowing one to infer electron properties of the plasma. The project will benefit basic investigations of low temperature plasmas as well as technological applications including processing plasmas for the semiconductor industry, plasma thrusters for space exploration, and atmospheric pressure plasmas. The project will also aim to attract students from underrepresented groups to participate in the development of a CO2 laser demonstration for outreach to local K-12 students. The project seeks to develop a new paradigm for Laser Thomson scattering (LTS) based on using continuous-wave (CW), high-power (kW) light sources to achieve higher scattering counts and improved detection limits as compared to conventional systems with pulsed lasers. Since the signal stream is continuous, the CW LTS approach will attempt to advance LTS from measuring time-average electron parameters to capturing temporally resolved dynamics up to ~10-100 kHz. This would represent an unprecedented and powerful advance of LTS towards studying plasma dynamics such as ionization and recombination in pulsed discharges, plasma waves, and oscillations such as the breathing mode in Hall effect thrusters. The diagnostic advances will be shared in publications and conferences and will be integrated into undergraduate and graduate courses at Colorado State University. Students from underrepresented minority groups will be sought to work on the project both for graduate thesis research and for undergraduate research experience.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.