FAST-ION ORBITS IN SPHERICAL TOKAMAKS

In a spherical tokamak, the 1/R variation of the toroidal field is ext reme, and for a given value of the safety factor a relatively low aver age toroidal field can be used, together with large plasma current and large plasma minor radius and elongation, The poloidal and toroidal f ields are then of similar size. In consequence, the orbits of fast ion s depart considerably from the guiding center orbits because of gyromo tion in the small magnetic fields on the low-field side. (C) 1996 Amer ican Institute of Physics.