Journalartikel

Jahr der Veröffentlichung: 2021

Zeitschrift: Physics of Plasmas

Bandnummer: 28

Heftnummer: 1

ISSN: 1070-664X

eISSN: 1089-7674

DOI Link: https://doi.org/10.1063/5.0032524

Verlag: American Institute of Physics

Abstract: 

A new quantitative evaluation of tunable diode laser induced fluorescence (TDLIF) measurements in magnetized plasma is presented in this article, taking into account Zeeman splitting of energetic levels as well as inter- and intra-multiplet mixing, defining the density distribution (alignment) of the excited

2 p 8 multiplet of argon. TDLIF measurements were used to evaluate light-transport properties in a strongly magnetized optically thick argon plasma under different pressure conditions. Therefore, a coupled system of rate balance equations was constructed to describe laser pumping of individual magnetic sub-levels of the

2 p 8 state through frequency-separated sub-transitions originating from

1 s 4 magnetic sub-levels. The density distribution of the

2 p 8 multiplet was described by balancing laser pumping with losses, including radiative decay, transfer of excitation between the neighboring levels within the

2 p 8 multiplet driven by neutral collisions, and quenching due to electron and neutral collisions. Resulting

2 p 8 magnetic sub-level densities were then used to model polarization dependent fluorescence, considering self-absorption, which could be directly compared with measured polarization-resolved TDLIF measurements. The achieved results enable to obtain unique solutions for the

1 s 4 and

1 s 5 magnetic sub-level densities which were found to be in good agreement with the densities obtained by laser absorption measurements. It is shown that polarization resolved TDLIF measurements in magnetized plasma conditions have strong pressure dependence. The effective disalignment rate constant which redistributes the

2 p 8 sub-levels among each other has to be considered for a correct description of the TDLIF. This rate is dependent on the neutral gas density and a specific rate coefficient. With the presented method, 1s state densities involved in the TDLIF can be determined without any absolute intensity calibration in an optically thick plasma. Additionally, the presented measurement method and model can help to further understand and improve the description of optical emission of argon based on individual sub-transition descriptions under magnetized conditions.

Harvard-Zitierstil: Bergert, R., Isberner, L., Mitic, S. and Thoma, M. (2021) Quantitative evaluation of laser-induced fluorescence in magnetized low-pressure argon plasma, Physics of Plasmas, 28(1), Article 013301. https://doi.org/10.1063/5.0032524

APA-Zitierstil: Bergert, R., Isberner, L., Mitic, S., & Thoma, M. (2021). Quantitative evaluation of laser-induced fluorescence in magnetized low-pressure argon plasma. Physics of Plasmas. 28(1), Article 013301. https://doi.org/10.1063/5.0032524