On the effect of synchrotron radiation and magnetic fluctuations on the avalanche runaway growth rate

The avalanche runaway growth rate was recently determined by analysis of the trajectories of the secondary runaway electrons in momentum space [Parks et al., Phys. Plasmas 6, 2523 (1999)]. Here, such an approach is used to study the effect of the electron synchrotron radiation and the magnetic fluctuations on the secondary generation of runaway electrons. It is found that not only the threshold electric field for runaway generation is increased due to these effects, but also the creation rate of secondary runaway electrons may be noticeably reduced for electric fields close to the threshold field. It has been shown that avalanche runaway generation can be efficiently suppressed in large tokamaks, even during major disruptions, for stochastic magnetic fluctuation levels $b̃>10−3.$