Diagnostic of Langmuir Solitons in Plasmas Using Hydrogenic Spectral Lines

Eugene Oks

doi:10.3390/atoms7010025

Abstract

The development of various spectroscopic diagnostics of relatively weak Langmuir waves in plasmas and their successful implementation have a history of over 50 years. As for spectroscopic diagnostics of Langmuir solitons (i.e., relatively strong Langmuir waves) in plasmas, there have only been very few theoretical papers. The most promising result so far was based on using satellites of the dipole-forbidden spectral lines of He, Li, or He-like and Li-like ions. It was shown that, in the case of Langmuir solitons, the peak intensity of the satellites of the dipole-forbidden lines can be significantly enhanced—by orders of magnitude—compared to the case of non-solitonic Langmuir waves. This distinctive feature of satellites under Langmuir solitons allows them to be distinguished from non-solitonic Langmuir waves. In the present paper, we perform a general study of the effects of Langmuir solitons on arbitrary spectral lines of hydrogen or hydrogen-like ions. Then, using the Ly-beta line as an example, we compare the main features of the profiles for the case of the Langmuir solitons with the case of the non-solitonic Langmuir waves of the same amplitude. We also show how the line profiles depend on the amplitude of the Langmuir solitons and on their separation from each other within the sequence of the solitons.

Highlights

The development of various spectroscopic diagnostics of relatively weak Langmuir waves in plasmas and their successful implementation have a history of over 50 years
We show how the line profiles depend on the amplitude of the Langmuir solitons and on their separation from each other within the sequence of the solitons
It can be seen that the integrated intensity of the most prominent satellite decreases as either a increases or as b increases

Summary

Introduction

The development of various spectroscopic diagnostics of relatively weak Langmuir waves in plasmas and their successful implementation have a history of over 50 years In paper [6], Hannachi et al added a magnetic field into consideration and performed simulations at the electron density Ne = 1013 cm−3 This electron density is unrealistic (too low) for the modern tokamaks (applications to which were hoped by the authors of paper [6]), and again, the additional broadening would rapidly diminish for more realistic (higher) values of Ne. this electron density is unrealistic (too low) for the modern tokamaks (applications to which were hoped by the authors of paper [6]), and again, the additional broadening would rapidly diminish for more realistic (higher) values of Ne It seems that the results by Hannachi et al [5,6] would not be useful for the experimental diagnostics of Langmuir solitons. We show how the line profiles depend on the amplitude of the Langmuir solitons and on their separation from each other within the sequence of the solitons

Brief Overview of the Theory

New Results

Both profiles have more features than inmaximum