EFFECTS OF ORBIT SQUEEZING ON ION-TRANSPORT PROCESSES CLOSE TO MAGNETIC AXIS

It is shown that ion thermal conductivity close to the magnetic axis i n tokamaks is reduced by a factor of \S\(5/3) if (M-i/M-e)(2/3)(T-e/T- i)(4/3)/\S\(5/3)much greater than 1. Here, S is the orbit squeezing fa ctor, M-i(M-e) is the ion (electron) mass, and T-i(T-e) is the ion (el ectron) temperature. The reduction reflects both the increase of the f raction of trapped particles by a factor of \S\(1/3), and the decrease of the orbit size in units of the poloidal flu?; psi by a factor of \ S\(2/3). (C) 1997 American Institute of Physics.