XGC-A03: Gradients for initial temperature profiles in the plasma core are increased

There are two changes comparing to the case XGC-A02:

  1. Gradients for initial temperature profiles in the plasma core are increased in order to see profile change at earlier times;
  2. The parameter neu_grid_min_psi is used in the namelist and is set to 0.75 in order to extend the region where the neutral distribution is computed.