Integrated Modeling of Tokamak Plasmas

Rich has sent an updated EFIT equilibrium for the DIII-D discharge 132014.03000. It has resolution of 129×129, kinetic equilibrium option enable and low EFIT error parameter. The TEQ code shows significantly lower residual in the near separatrix region as well.

Note that the plasma pressure profiles looks significantly different comparing to the lower resolution case at 3.023 sec (left figure below shows the derivate of the plasma pressure at 3.000 sec and right figure shows the derivative of the plasma pressure at 3.023 sec):

EFIT grid has been set to 129×129, number of iterations has been increased to 50, the namelist value for error has been decreased from 1.e-3 to 1.e-4. The resulting layout looks very similar. However, the normalized beta is reduced by about 3%. Analysis with TEQ still indicates relatively high residual error near the separatrix. This error might be related to different input options that might be associated with different account for the bootstrap current. There are differences in FF’ and q profiles that might be more difficult to understand. Some of equilibrium profiles are shown below. Left column shows profiles obtained with the new EFIT (129×129) run, while the left column shows profiles obtained with the old EFIT (65×65) run.

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.

Problems identified in the case XGC-A02 remains at longer times (30 ion transit times in the case XGC-A02 vs 6 ion transit times in the case XGC-A01). The diffusivity remain rather high in the plasma core. Particles accumulate in the SOL region. It looks that the later problem has been introduced during recent code update and relates to the interpolation of tbl_* diffusivities used in the outer region of plasma and FMCFM diffivities in the plasma core.

Relatively large diffusivity in the plasma core is observed in this case. There is a density increase in the separatrix-SOL region that need to be understood. It is possible that longer simulation is necessary to relax the plasma profiles in the core.

This case is modified from the case XGC-A00 with the following changes:

1. MMM95 model through the FMCFM interface is used for anomalous transport computations in the core region;
2. Computational domain is extended to the magnetic axis;
3. Realistic initial conditions for temperatures and plasma densities are used;
4. New radiation model is included

input-xgc-a01

This simulation that is based on input file used in the study of the neoclassical scaling of the H-mode pedestal width. The initial conditions for the plasma temperatures and density is set by analytical expressions with the plasma density of at the inner boundary of the computation domain. The computation domain is set from 0.85 to 1.05 of the normalized poloidal flux. Simple model for the anomalous transport is used (fm_use=0).