Analysing the distribution of runaway electrons in the EAST tokamak based on SOFT

Abstract In the Experimental Advanced Superconducting Tokamak (EAST), the energy of runaway electrons confined in plasma can reach tens of MeV. These electrons can emit synchrotron radiation and, in turn, their distribution can be obtained by synchrotron radiation. The Synchrotron-detecting Orbit Following Toolkit (SOFT) can simulate synchrotron radiation images with different runaway electron distributions. In these simulations, one initially assumes that the runaway electrons are mono-energetic, then obtains the distribution of the electron pitch angle θ p with respect to the magnetic field, which is then employed to analyze the energy distributions of runaway electrons. In this way, one evaluates whether the simulation results are in agreement with experimental results concerning the synchrotron radiation spot shape and the intensity variations within the spot. Upon analyzing synchrotron radiation with optimal runaway electron distribution, we find that the peak value of synchrotron radiation appears near θ p = 0.3  rad, which is larger than θ p of most runaway electrons.