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(IC/P-14) Current Drive by Neutral Beams, Rotating Magnetic Fields and Helicity Injection in Compact Toroids

R. Farengo¹⁾, A.F. Lifschitz²⁾, N.R. Arista¹⁾, R.A. Clemente^3)
 
1) Comision Nacional de Energia Atomica Centro Atomico Bariloche, Bariloche, Argentina
²⁾ Consejo Nacional de Investigaciones Cientificas y Tecnicas, Argentina
³⁾ Universidade Estadual de Campinas, Campinas SP, Brasil

Abstract.  A Monte-Carlo code is used to study neutral beam current drive in Spheromaks. The exact particle trajectories are followed in the self-consistent equilibria calculated including the beam current. Reducing Z(eff) does not increase the current drive efficiency because the reduction of the stopping cross section is compensated by an increase in the electron canceling current. Significant changes in the safety factor profile can be produced with relatively low beam currents. Minimum dissipation states of a flux core spheromak sustained by helicity injection are presented. Helicity balance is used as a constraint and the resistivity is considered to be non-uniform. Two types of relaxed states are found; one has a central core of open flux surrounded by a toroidal region of closed flux surfaces and the other has the open flux wrapped around the closed flux surfaces. Non-uniform resistivity effects can be very important due to the changes they produce in the safety factor profile. A hybrid, fluid electrons particle ions, code is employed to study ion dynamics in FRCs sustained by rotating magnetic fields.

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