Impurity and neutral effects on the dissipative drift wave in tokamak edge plasmas

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Abstract
Possible destabilizing mechanisms for the linear electrostatic dissipative drift waves (in tokamak edge plasmas) are investigated in slab geometry. The effects of processes such as ionization, charge exchange, radiation, and rippling are examined. In particular, the impurity condensation associated with radiation cooling is evaluated appropriately for the drift wave ordering, which is found to be an important driving mechanism in contrast to the results of earlier studies [R. J. Thayer and P. H. Diamond, Phys. Rev. Lett. 6 5, 2784 (1990)]. It is also shown that the role of ionization is quite complicated, and depends strongly on the manner in which the equilibrium is achieved. The linear eigenmode equation is studied both analytically and numerically. For the range of parameters relevant to TEXT tokamak [K. W. Gentle, Nucl. Fusion Technol. 1, 479 (1981)], both the charge exchange and the rippling effect are found to be unimportant for instability.

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