Influence of the Ion Mass in the Radial to Orbital Transition in Weakly Collisional Low-Pressure Plasmas Using Cylindrical Langmuir Probes
| Autor: | J. Ballesteros, José Ignacio Fernández Palop, Guillermo Fernando Regodón, J M Díaz-Cabrera |
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| Rok vydání: | 2020 |
| Předmět: |
Mean free path
chemistry.chemical_element cold plasma Computer Science::Digital Libraries lcsh:Technology 01 natural sciences ion-neutral charge-exchange collisions 010305 fluids & plasmas Ion lcsh:Chemistry symbols.namesake Neon Physics::Plasma Physics 0103 physical sciences Langmuir probe General Materials Science lcsh:QH301-705.5 Instrumentation Debye length 010302 applied physics Fluid Flow and Transfer Processes Physics lcsh:T Process Chemistry and Technology General Engineering sheath theories Ion current plasma surface technology Plasma lcsh:QC1-999 Computer Science Applications TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES lcsh:Biology (General) lcsh:QD1-999 plasma diagnosis chemistry lcsh:TA1-2040 ion temperature symbols Computer Science::Programming Languages Electron temperature ion mean free path Atomic physics lcsh:Engineering (General). Civil engineering (General) lcsh:Physics |
| Zdroj: | Applied Sciences Volume 10 Issue 17 Applied Sciences, Vol 10, Iss 5727, p 5727 (2020) |
| ISSN: | 2076-3417 |
| DOI: | 10.3390/app10175727 |
| Popis: | This paper presents an experimentally observed transition from the validity of the radial theories to the validity of the orbital theories that model the ion current collected by a cylindrical Langmuir probe immersed in low-pressure, low-temperature helium plasma when it is negatively biased with respect to the plasma potential, as a function of the positive ion-neutral collision mean free path to the Debye length ratio &Lambda =&lambda +/&lambda D. The study has been also conducted on argon and neon plasmas, which allows a comparison based on the mass of the ions, although no transition has been observed for these gases. As the radial or orbital behavior of the ions is essential to establish the validity of the different sheath theories, a theoretical analysis of such a transition not only as a function of the parameters &Lambda and &beta =T+/Te, T+ and Te being the positive ion and electron temperature, respectively, but also as a function of the ion mass is provided. This study allows us to recognize the importance of the mass of the ion as the parameter that explains the transition in helium plasmas. Motivated by these theoretical arguments, a novel set of measurements has been performed to study the relationship between the &Lambda parameters in the transition that demonstrate that the effect of the ion mean free path cannot be completely ignored and also that its influence on the ion current collected by the probe is less important than the effect of the ion temperature. |
| Databáze: | OpenAIRE |
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