The resonant interaction between a runaway electron (RE) beam and a reactor-grade background plasma is investigated through two-dimensional particle-in-cell simulations, employing a simplified model of the system. The temporal evolutions of the electron momentum distribution function for two separate initial beam energies (1 and 10 MeV) are tracked, revealing the occurrence of plasma wave growth concomitant with pitch angle scattering or momentum distribution diffusion within the RE beam. Notably, we identify and confirm the dependence of the dominant resonance condition on the initial kinetic energy of the RE beam. Furthermore, we quantify the effect of particle-wave interactions on the RE momentum distribution diffusion by assessing the average kinetic energy flux from the RE distribution function.
This paper investigates the resonant interaction between runaway electron (RE) beams and background plasma through particle-in-cell simulations. It reveals that this interaction leads to the growth of plasma waves and pitch angle scattering or momentum distribution diffusion within the RE beam, with the dominant resonance condition depending on the initial kinetic energy of the RE beam.
Velocity diffusion in plasma waves excited by electron beams