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          Institute: MPI für Plasmaphysik     Collection: Articles, Books, Inbooks     Display Documents

ID: 21073.0, MPI für Plasmaphysik / Articles, Books, Inbooks
Characteristics of detached plasmas associated with electron- ion and molecular assisted recombinations in NAGDIS-II
Authors:Nishijima, D.; Wenzel, U.; Ohsumi, K.; Ohno, N.; Uesugi, Y.; Takamura, S.
Date of Publication (YYYY-MM-DD):2002-05
Title of Journal:Plasma Physics and Controlled Fusion
Journal Abbrev.:Plasma Phys. Control. Fusion
Issue / Number:5
Start Page:597
End Page:610
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Recombination in a helium and helium-hydrogen plasma was experimentally investigated in the linear divertor simulator NAGDIS-II. To identify the physical mechanisms, electron-ion recombination (EIR) and molecular assisted recombination (MAR), the plasma parameters in the recombining region have been measured. We used spectroscopic techniques on the basis of continuum emission and line en-fission from highly excited levels due to EIR and Langmuir probes. The dependence of the plasma parameters on the neutral pressure in a pure helium plasma and in a helium-hydrogen mixture shows clearly that recombination is caused by different processes in the two cases. In a pure helium plasma a roll-over and a following decrease of the electron density as well as a monotonic decrease of the electron temperature down to 0.1 eV were observed when increasing the helium pressure. Here EIR is the recombination mechanism. Conversely, when hydrogen is added to the helium plasma, the electron density decreases monotonically while the central electron temperature remains above I eV. This particular behaviour in the helium-hydrogen plasma can only be explained by the dominant action of MAR.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Plasmaphysik/HU Berlin
External Affiliations:Nagoya Univ, Grad Sch Engn, Dept Energy Engn & Sci, Chikusa Ku,; Furo Cho, Nagoya, Aichi 4648603, Japan; Nagoya Univ, Ctr Integrated Res Sci & Engn, Chikusa Ku, Nagoya, Aichi 4648603, Japan
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