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Abstract
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In recent years, a great deal of consideration has been paid to the nonextensive generalization of the Boltzmann-Gibbs-Shannon (BGS) entropy where it has been successfully used to explain some interesting problems in physics. Self-gravitating systems and plasma are two main candidates that use this entropy [1-3]. This entropy first recognized by Renyi[4] and then proposed by Tsallis[5]. Tsallis proposed the q-entropy as , where K_B is the Boltzmann constant, P_i is the probability of the i’th microstate and q is a parameter quantifying the degree of non-extensivity of the system. In this work, using multi fluid model and Sagdeev potential method, a modified Bohm’s criterion for formed sheath in collisional electronegative plasma in which electrons and negative ions have non-extensive velocity distribution, is derived. The effects of nonextensivity degree q and collision parameter α on the formed sheath criterion which has upper and lower limits are investigated. Furthermore the modified Bohm’s criterion which we obtain coincides with those given by the Maxwellain distribution function, when q tends to 1. Also by using numerical methods the behavior of positive ions density and electrical potential in the sheath region for different value of q and α as function of normalized distance are studied.
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