Two-dimensional kinetic model for the evaporation of hydrogen pellets in a tokamak
1985; Linguagem: Inglês
Autores
B. V. Kuteev, A. P. Umov, L. D. Tsendin,
Tópico(s)Nuclear reactor physics and engineering
ResumoThe problem of the evaporation of a hydrogen fuel pellet in a hot plasma is solved for the case with a Maxwellian electron velocity distribution and a nonuniform evaporation over the surface of the pellet. An expression derived for the evaporation rate N describes this rate within 10% as a function of the temperature, the plasma density, and the pellet radius. The values found for N are only slightly higher than the values calculated in the model of Parks et al. (Nucl. Fusion 17, 539 (1977)), Milora and Foster (IEEE Trans. Plasma Sci. 6, 578, (1978)), and Parks and Turnbull (Phys. Fluids 21, 1735 (1978)). The reason is a mutual cancellation of some factors ignored in that model: the electron distribution as a function of energy and angle and the nonuniformity of the evaporation. In a kinetic model, the heat flux to the pellet is carried by electrons with an initial energy (6--8)T/sub e/. This circumstance explains why the electric fields have only a weak effect on the evaporation rate near the surface. A refined model is used to calculate the evaporation rates in existing devices.
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