Plasma flow asymmetries in the natural helical divertor of anl= 3 torsatron and their relation to particle losses

Autor:	N.I. Nazarov, A.V. Lozin, V.A. Rudakov, M.S. Smirnova, A.S. Slavnyj, I.Yu. Adamov, S. A. Tsybenko, L.I. Grigor'eva, A. Ye. Kulaga, K.S. Rubtsov, K. Yamazaki, A.P. Litvinov, E.D. Volkov, Tomohiro Morisaki, V.D. Kotsubanov, I. K. Nikolskij, Yu.K. Mironov, E.L. Sorokovoj, T. Mizuuchi, Nobuyoshi Ohyabu, V.V. Chechkin, Suguru Masuzaki
Rok vydání:	2002
Předmět:	Physics Nuclear and High Energy Physics Toroid Ambipolar diffusion Divertor Torus Plasma Condensed Matter Physics Charged particle Magnetic field symbols.namesake Physics::Plasma Physics symbols Langmuir probe Atomic physics
Zdroj:	Nuclear Fusion. 42:192-201
ISSN:	1741-4326 0029-5515
DOI:	10.1088/0029-5515/42/2/311
Popis:	In the l = 3/m = 9 Uragan-3M (U-3M) torsatron (R0 = 1m , ¯ a ≈ 0.12 m, Bφ = 0.72 T, ι(¯ a)/2π ≈ 0.4), an open helical divertor is realized. A hydrogen plasma with ¯ ne ≈ 2 × 10 18 m −3 , Te ≈ 0.3 keV, Ti ≈ 0.1 keV is produced and heated by RF fields (ω ≈ ωci). The flows of diverted plasma are detected by 78 plane Langmuir probes aligned poloidally in the spacings between the helical coils in two geometrically symmetric poloidal cross-sections of the torus. In measurements of the distributions of ambipolar (e.g. the ion saturation current Is) and non-ambipolar (e.g. the current to a grounded probe Ip) plasma flows, a strong vertical asymmetry of these distributions is observed, its main characteristics being a many-fold difference in the values of Is in the outgoing flows in the upper and lower parts of the torus and the opposite signs of Ip in these flows, with the positive current corresponding to the larger ambipolar flow of the diverted plasma. Reversal of the direction of the toroidal magnetic field results in the reversal of the asymmetry, with the larger flux (and Ip > 0) always flowing in the ion B × ∇B drift direction. On this basis, it is concluded that the asymmetry is related to direct (non-diffusive) losses of charged particles from the confinement volume. This conclusion is validated by numerical modelling of thermal and fast particle orbits in U-3M, where qualitative agreement has been revealed between the calculated distribution of the angular co-ordinates of lost particles and the measured poloidal distributions of the flows of diverted plasma.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::a6f1a0aa806983b18bbee3fcde9623a0 https://doi.org/10.1088/0029-5515/42/2/311 Zobrazit plný text záznamu