A Lagrangian model for laser-induced fluorescence and its application to measurements of plasma ion temperature and electrostatic waves
- Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy
Extensive information can be obtained on wave-particle interactions and wave fields by a direct measurement of perturbed ion distribution functions using laser-induced fluorescence (LIF). For practical purposes, LIF is frequently performed on metastable states that are produced from neutral gas particles and ions in other electronic states. If the laser intensity is increased to obtain a better LIF signal, then optical pumping can produce systematic effects depending on the collision rates which control metastable population and lifetime. We numerically simulate the ion velocity distribution measurement and wave-detection process using a Lagrangian model for the LIF signal for the case where metastables are produced directly from neutrals. This case requires more strict precautions and is important for discharges with energetic primary electrons and a high density of neutrals. Some of the results also apply to metastables produced from pre-existing ions. The simulations show that optical pumping broadening affects the ion velocity distribution function f0(v) and its first-order perturbation f1(v,t) when the laser intensity is increased above a certain level. The results also suggest that ion temperature measurements are only accurate when the metastable ions can live longer than the ion-ion collision mean free time. For the purposes of wave detection, the wave period has to be significantly shorter than the lifetime of metastable ions for a direct interpretation. It is more generally true that metastable ions may be viewed as test-particles. Finally, as long as an appropriate model is available, LIF can be extended to a range of environments.
- Research Organization:
- Univ. of Iowa, Iowa City, IA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- FG02-99ER54543
- OSTI ID:
- 1515034
- Alternate ID(s):
- OSTI ID: 1416463
- Journal Information:
- Physics of Plasmas, Vol. 25, Issue 1; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Analysis and comparison of ion-acoustic wave reflection using laser-induced fluorescence and Langmuir probes
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journal | December 2018 |
Laser-induced fluorescence saturation effects on ion velocity distribution functions in the vicinity of reflecting surfaces
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journal | February 2019 |
Measurement of wave-particle interaction and metastable lifetime using laser-induced fluorescence
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journal | April 2019 |
Laser induced fluorescence of Ar-I metastables in the presence of a magnetic field
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journal | June 2018 |
Measurement of wave-particle interaction and metastable lifetime using laser-induced fluorescence | text | January 2019 |
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