Helium atom line-intensity ratios as an integrated diagnostic tool for low-pressure and low-density plasmas

Abstract

Detection of anisotropy in the electron velocity distribution produced by electron cyclotron resonance heating using the polarization of helium atom emission lines

Spectroscopic Measurement of Hydrogen Atom Density in a Plasma Produced with 28 GHz ECH in QUEST

“…When the opacity is significant, the reabsorption of Lyman series emission lines increases the excited hydrogen atom density, and ignoring the effect results in the overestimation of n H (R). Since the present CR model analysis is mainly affected by the L ε line (p = 1-6) and the secondary effect, namely, the increase in n H,6 (R) owing to the absorption of the other Lyman series emission lines, is small [14,15], we evaluated the effect of the opacity by calculating the optical depth of the L ε line at its line center [16] under the assumption of a uniform plasma as follows:…”

On the Spatial Uniformity of the Degree of Ionization in a Helium ECR Plasma Produced under a Simple Cusp Field

“…An advantage of the present method is the empirical determination of these parameters, owing to the reliability of the CR model calculation. The relevance of the parameters, from the viewpoint of the order of magnitude, was discussed in Reference [3,4].…”

“…The adopted model was developed by Goto [5] and Fujimoto [6], and we additionally included the optical escape factor (OEF), which represents the effective reduction of the spontaneous emission coefficient due to radiation trapping [7][8][9]. In our plasma, the density in a state p, which designates a term resolved into the orbital angular momentum (e.g., 2 1 P, 2 3…”

“…In this study, we simultaneously evaluate n e and n 1 1 S , using the helium atom (HeI) emission-line intensities and by collisional-radiative (CR) model analysis. This is becoming a standard method, owing to the recent improvements in its measurement accuracy for various types of plasma (see Reference [3] and the references therein). We previously measured a one-dimensional spatial distribution of the DOI [3,4] and found that the DOI increased by up to 30% inside the ECR surface.…”

“…This is becoming a standard method, owing to the recent improvements in its measurement accuracy for various types of plasma (see Reference [3] and the references therein). We previously measured a one-dimensional spatial distribution of the DOI [3,4] and found that the DOI increased by up to 30% inside the ECR surface. The purpose of the present study is to extend the measurement to two dimensions in order to confirm the spatial uniformity of the DOI.…”