TRANSPORT PROCESSES CLOSE TO MAGNETIC AXIS IN QUASIHELICALLY SYMMETRICAL STELLARATORS

Transport processes in the region close to the magnetic axis in quasih elically symmetric stellarator's are investigated by solving fluid and kinetic equations. It is found that the isomorphic transformation bet ween transport fluxes in quasihelically symmetric stellarators and tho se in tokamaks is still valid if the dependence of the Fourier amplitu de of the magnetic field spectrum on the flux function does not transf orm accordingly, and if the absolute values are employed in the transf ormations of orbit, size and fraction of trapped particles. It is also found that orbit squeezing effects are less effective in quasihelical ly symmetric stellarators because the size of the orbit is smaller tha n that in tokamaks. The bootstrap current density does not vanish on t he magnetic axis if dp/d psi remains finite. Here, psi is the toroidal flux function and p is the plasma pressure. The direction of the boot strap current density is also opposite to that in tokamaks similar to that in the core region. (C) 1997 American Institute of Physics.