Spectroscopic Diagnosis Of A Dense Hydrogen Plasma Source

This report gives the details of experiments performed to measure the levels and the angular distribution of oscillating electric fields in an aluminum plasma produced by the Phoenix advanced pulsed radiation source. The electric field values were obtained by measuring the L (beta), L (gamma), L (sigma), and L (epsilon) line profiles of Al XIII and fitting the profiles to a model for the Phoenix plasma source. The model attempts to take into account all of the mechanisms which lead to broadening of the observed profiles for the conditions present in the Phoenix plasma. The main broadening mechanisms used in the model include Doppler broadening from the bulk motion of the plasma, stark broadening by electrons, ions and oscillating electric fields, and self absorption. In addition to the flat crystal and two curved crystal spectrometers used to measure the lines profiles, a pinhole camera and a four frame camera were used to try and obtain the size of the most dense retions in the plasma. The size of these "hot spots" were found to be less than 500 microns. From fits of the experimental profiles to the data, the level of anomalous electric fields in the Phoenix plasma source were found to be Eo = 1 - 9 Gv/cm, indicative of a strong Langmuir turbulence. The fields were also found to develop anisotropically, primarily along the direction of the discharge.

A spectroscopic diagnostic tool has been developed to determine the electron temperature and the neutral density in helium, hydrogen and argon plasmas from absolutely calibrated spectroscopic measurements. For each gas, a method of analysis which uses models specific to each species present in the plasma (neutral atom or singly ionized atom) has been defined. The experimental electron density is used as an input parameter to the models, and the absolutely calibrated spectroscopic data are processed beforehand to obtain the populations of the upper excited levels corresponding to the observed spectral lines. For helium plasmas, the electron temperature is inferred from the experimental helium ion excited level p = 4 population using a corona model, and then the neutral density is determined from the experimental helium neutral excited level populations using a collisional-radiative model for helium neutrals. For hydrogen plasmas, combinations of the electron temperature and the neutral density are determined from the experimental hydrogen neutral excited level populations using a collisional-radiative model specific to hydrogen atoms. For argon plasmas, the electron temperature is inferred from the experimental argon ion excited level populations using a collisional-radiative model for argon ions, and then the neutral density is determined from the experimental argon neutral excited level populations using a collisional-radiative model for argon neutrals. This diagnostic tool was applied to three experiments with different geometries and plasma conditions to test the validity of each data analysis method. The helium and hydrogen data analysis methods were tested and validated on helium and hydrogen plasmas produced in the VASIMR experiment, a plasma propulsion system concept. They gave electron temperatures and neutral densities that were consistent with other diagnostics and theory. The argon diagnostic tool was tested on argon plasmas produced in the VASIMR experiment, the Helimak experiment and the Helicon experiment. The electron temperature and neutral density obtained on both the Helimak and the Helicon experiments were consistent with other diagnostics and with theory, and validated the method of analysis. An impurity problem on the VASIMR experiment made it difficult for the data analysis to be validated.

The results of the present work show an opportunity of pure spectroscopic detection of the degree of dissociation of hydrogen in low temperature plasmas and indicate an insufficient knowledge about elementary processes for plasma diagnostic.

Market: Plasma physicists and students. Upon publication in 1968, Plasma Diagnostics represented the most up- to-date survey of the experimental methods used in plasma analysis, including the necessary theoretical background. This work emphasizes spectroscopic techniques along with in-depth sections on laser techniques and electric and magnetic probe methods. The evaluation of collision and transport cross sections, heat and electrical conductivity, and viscosity are some of the many applications of plasma diagnostics reviewed as well. This long-awaited reprint volume is of interest to both physicists and students of theoretical physics as it deals with plasma theory from a fundamental point of view, stressing a careful derivation and discussion of the equations.

A system to determine the density and temperature of ground state hydrogen atoms in a plasma by vacuum ultraviolet laser absorption spectroscopy is described. The continuous tunability of the spectrometer allows for analysis at any of the Lyman transitions. The narrow bandwidth of the laser system allows for the accurate determination of the absorption lineshape and hence the translational temperature. The utility of the system is exemplified by data obtained on an ion-source plasma. The measurements demonstrate the quality of the data as well as illustrating the behavior of this ion source under varying discharge conditions. 9 refs., 5 figs., 1 tab.

Nonequilibrium atmospheric pressure plasma jets (N-APPJs) generate plasma in open space rather than in a confined chamber and can be utilized for applications in medicine. This book provides a complete introduction to this fast-emerging field, from the fundamental physics, to experimental approaches, to plasma and reactive species diagnostics. It provides an overview of the development of a wide range of plasma jet devices and their fundamental mechanisms. The book concludes with a discussion of the exciting application of plasmas for cancer treatment. The book provides details on experimental methods including expert tips and caveats. covers novel devices driven by various power sources and the impact of operating conditions on concentrations and fluxes of the reactive species. discusses the latest advances including theory, modeling, and simulation approaches. gives an introduction, overview and details on state of the art diagnostics of small scale high gradient atmospheric pressure plasmas. covers the use of N-APPJs for cancer applications, including discussion of destruction of cancer cells, mechanisms of action, and selectivity studies. XinPei Lu is a Chair Professor in the School of Electrical and Electronic Engineering at Huazhong University of Science and Technology. Stephan Reuter is currently Visiting Professor at Université Paris-Saclay. In a recent Alexander von Humboldt research fellowship at Princeton University, he performed ultrafast laser spectroscopy on cold plasmas. Mounir Laroussi is Professor of Electrical and Computer Engineering and director of the Plasma Engineering and Medicine Institute at Old Dominion University. He is a Fellow of IEEE and recipient of an IEEE Merit Award. DaWei Liu is Professor in the School of Electrical and Electronic Engineering at Huazhong University of Science and Technology.