Momentum-space study of the effect of bremsstrahlung radiation on the energy of runaway electrons in tokamaks

The dynamics of runaway electrons in tokamak plasmas is studied in momentum space. In this analysis the electrons are accelerated by an electric field while they are decelerated by collisional drag, synchrotron radiation, and bremsstrahlung radiation. It is shown that the inclusion of bremsstrahlung losses into the calculations is important for the interpretation of disruption-mitigation experiments where large amounts of high Z are injected into the plasma. The inclusion of bremsstrahlung reduces the maximum energy that the runaway electrons can gain from the electric field.