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Author(s):
N. Nakajima and M. Okamoto
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Title:
Beam-Driven Currents in the 1/ (nu) Regime in a Helical System
Date of publication:
Apr. 1990
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Key words:
beam-driven current , Ohkawa current , helical system, stellarator, heliotron, torsatron, neoclassical theory
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Abstract:
Beam currents driven by a neutral particle injection in a helical system ( stellarator, heliotron/torsatron ) are studied in the 1/nu collisionality regime. The general expression for the beam-driven current is obtained for arbitrary magnetic field configurations by solving the drift kinetic equation for electrons. It is found that F = J_net/J_b ( J_net is the net current and J_b is the fast ion beam current ) increases as f_t and Z_eff where f_t is the fraction of trapped electrons and Z_eff is the effective ionic charge number . Especially, for Z_eff simeq I the effect of trapped electrons is large and F is roughly proportional to f_t . On the other hand, if Z_eff is greater than or equal to 3 the effect of trapped electrons becomes small.
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