Ionization and recombination coefficients for Fe xv—Fe xix

During neutral-beam-heated, counter-injection discharges in the ISX-$B$ tokamak, impurities tend to collect in the interior of the plasmas. In these circumstances iron ions preferentially accumulate with long confinement times in regions of almost constant electron temperature. The concentrations of intermediate stages of iron (Fe XV, XVI, XVIII, and XIX) have been studied under these conditions to investigate the ratios of recombination and ionization coefficients. The dielectronic recombination coefficients are then deduced by assuming that the ionization and the radiative and charge-exchange recombination rates can be calculated closely from theory.