Two input files are generated based on XGC-A07 input file: (1) XGC-A08: same equilibrium and same input file, but older version of the code; (2) XGC-A09: same equilibrium, newer version of the code, but older version of the flow shear suppression model. Left panels show results for the case XGC-A08 and right panels show results for the caseXGC-A09
Results clearly indicated that the problem has been introduced during the recent merge with the svn repository.
The FMCFM changes has been synchronized with the version of the XGC-0 code from the svn repository. Gunyoung committed his changes related to the impurity radial model and get_mid_r bug. Theory motivated coefficient for the flow shear suppression factor is used. The simulation uses high resolution equilibrium provided by Rich Groebner. There are significant changes in the plasma density dynamics. It is not clear if these changes relate to (1) model for flow shear suppression factor; (2) new equilibrium; (3) other changes to the code. In order to isolate the problem, two new simulations are submitted: (1) XGC-A08: same equilibrium and same input file, but older version of the code; (2) XGC-A09: same equilibrium, newer version of the code, but older version of the flow shear suppression model.
The fm_web flows shear stabilization factor is decreased from to . as result, the effect of flow shear stabilization is significantly reduced for the whole plasma profile.
New XGC-0 namelist parameter is implemented in order to control parameter that is responsible for flow shear stabilization factor. According to Glenn’s notes, the fm_wexb coefficient should depend on :
The tbl_diffusion_mode option is set to 3 to enable transition from FMCFM in the plasma core and old model in the SOL region. In addition, spacial variation is allowed in the SOL region by setting tbl_d_profile_on to 1. As result, the problem of accumulation of particles in the SOL region is resolved:
Rich Groebner has provided information about total heating powers in the DIII-D discharges that are considered from modeling with the XGC-0 code. According to Rich:
Neutral beam injection was the only auxiliary heating on these discharges... I have supplied powers averaged over the entire time of interest.
132014 8.12 MW
132016 7.35 MW
132017 8.49 MW
132018 7.09 MW
Rich has also provided the plasma density and temperature profiles.
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.
to 
. as result, the effect of flow shear stabilization is significantly reduced for the whole plasma profile.
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