Several single particle simulation has been run with different time step. The energy is preserved within 2% in the simulation for 200 ion transient times only when the time step is about 1e-3 of ion transient time (sml_dt=1.d-3). Figures below show energy as function of time
sml_dt=0.02
sml_dt=0.005
sml_dt=0.002
sml_dt=0.001
In these single particle simulations, the computation time with the FMCFM interface (fm_use=1)
real 20m15.682s
user 19m57.207s
sys 0m6.028s
is compared with the corresponding simulation without the FMCFM interface (fm_use=0)
Updated version of the XGC-0 code that includes recent additions from Gunyoung Park is used for this simulation. The new version of XGC- inludes:
New simple radiation model is based on ADPAK radiation data. The model assumes constant impurity density in the region where radiation cooling is applied;
Improved sheath potential model;
Diffusivities in the SOL region is set by tbl_ parameters rather than FMCFM models.
The electron temperature is slightly lower in the SOL region comparing to the electron temperature in the case XGC-222.
In order to give time for the radial electric field to develop, the use of MMM95 module through the FMCFM interface is delayed by 1000 time steps. Particle and thermal diffusivities from tbl namelist were used during the first 1000 time steps.
There are relatively small changes for the plasma density profile; electron temperature profile looks more realist.
Overall summary: There is insufficient flow shear stabilization for the particle transport in the inner pedestal region. The next thing to try is the updated sheath potential and radiation models provided by Gunyoung Park.
