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  • Extension of collisionless discharge models for application to fusion-relevant and general plasmas [Elektronski vir]
    Kos, Leon, 1966- ; Duhovnik, Jože, 1948- ; Jelić, Nikola
    Defining and finding the plasma-sheath boundary (also referred to as plasma edge, sheath edge or sheath entrance) is a problem of general relevance in plasma physics, and particularly so in the ... context of laboratory, space and fusion plasmas. In a most general approach this problem starts from the Poisson equation under the condition that (i) the electron density distribution is a known function of local potential, (ii) the ion source velocity distribution is known (iii) with additional assumption that the potential profile is monotonic. The basic unknowns of the problem to be found are the spatial potential profile and the final ion-velocity distribution. Once this solution is found, the moments of the velocity distribution, i.e, density, particle flux energy, and thermal fluxes are calculated based on the velocity distribution as calculated in any location of the system like e.g., scrape-off layer (SOL) in Tokamak devices. From a physical point of view the problem was defined by Bissell and Johnson(B&J) [Phzs. Fluids 30, 779 (1987)] as a task to find the ion potential profile and ion velocity distribution in a plane parallel discharge with a Maxwellian ion source. The B&J model is a generalization of well known Tonks-Langmuir (T&L) [Phys. Rev. 34, 876 (1929)] discharge characterized by the so-called cold ion source. Unlike the T&L model, which can be readily solved analytically, attempts on solving the B&J model with a so-called warm ion source were done only numerically. Since the applicability of numerical solutions has been limited only to a narrow range of the ionsource temperature for many years, Kos et al. [Phys. Plasmas 26(9), (2009)] recently tackled and solved the problem without any approximation of the integral equation kernel. The solution of Kos et al. is valid without any restriction regarding the ion temperature, i.e., applicable to both general and fusion plasmas with high ion temperatures. However, it still remains restricted to the specific case of ionization strength distribution, which is according to B&J proportional to the local electron density. In this paper we extend further the Kos et al. model to the case of constant ionization strength distribution.
    Vrsta gradiva - prispevek na konferenci
    Leto - 2009
    Jezik - angleški
    COBISS.SI-ID - 11235867