BOOTSTRAP CURRENT SCALING IN TOKAMAKS

Using a self-consistent equilibrium, the bootstrap current in a tokamak of arbitrary aspect ratio is studied. An empirical formula is deduced which determines the bootstrap current as a function of the pressure, temperature and total current profiles as well as the poloidal beta and aspect ratio of the device. This empirical formula is compared with an expression obtained by the ITER group; also a comparison with an analytical result (valid at large aspect ratio) is made. It is found that the empirical result determined here agrees well with the large aspect ratio result, but not so well with the empirical formula of the ITER group.