A method for evaluations on the radiation trapping in an inductively coupled plasma in argon

Abstract

One of the general challenges for the evaluation and interpretation of optical emission spectroscopy measurements is the occurrence of radiation trapping, which is also named self-absorption or opacity. A convenient technique to treat radiation trapping is the introduction of a parameter, which is called escape factor and gives a measure for the amount of radiation trapping. In this paper evaluations on the concept of escape factors are presented for an inductively coupled plasma in argon. Especially, the strong argon line at 811.53 nm, which arises from the transition of 2p9−1s5, is under consideration. To estimate escape factors for this line, a particular method is proposed and presented here. First experimental results are obtained under the restrictive assumptions that transitions into the resonant levels 1s2 and 1s4 are sufficiently optically thin and ratios of population densities are constant.

Study of argon assimilation into the post-disruption runaway electron plateau in DIII-D and comparison with a 1D diffusion model

“…The lower state densities were approximated using Boltzmann equilibrium. In the case of Ar-I 811.5 nm, this is thought to be a reasonable approximation because the lower level 4s(1s 5 ) is metastable [11]. In the case of H-I 656.2 nm, this is thought to be a reasonable approximation also because the 2s level is metastable and the 1s-2p transition is expected to be strongly trapped.…”

Ion acceleration in Ar–Xe and Ar–He plasmas. I. Electron energy distribution functions and ion composition

“…Furthermore, given our low operating gas pressure, a small population of the 1s 5 metastable level is expected, and therefore the plasma might be considered optically thin at these wavelengths. 37 The emission intensities of the spectral lines of neutral argon and neutral xenon as a function of the xenon fraction, normalized to the measured emission intensities for the corresponding pure gas plasma, collected at z = 126 cm, are shown in Fig. 5 the ground states is obtained from Eq.…”

Application of the escape factor method for determination of excited states densities in a low‐pressure argon radio‐frequency discharge

“…Our modification of the method differences more in form, rather then in fundamental content. A related procedure was also used in [17] for a more specific task to estimate the degree of self-absorption on 811.53 nm argon line. When using a novel technique, the benchmarking by comparison with an independent method is of particular importance.…”