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.
TEQ is not completely converged for this case. Plasma pressure and q profiles are not completely reproduced by the TEQ code.
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:
- MMM95 model through the FMCFM interface is used for anomalous transport computations in the core region;
- Computational domain is extended to the magnetic axis;
- Realistic initial conditions for temperatures and plasma densities are used;
- New radiation model is included
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.
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).
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
In these single particle simulations, the computation time with the FMCFM interface (fm_use=1)
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.
Four equilibria that represent plasma current scan has been provided by Rich Groebner. The readme file that came with the eqdsk files describes these discharges as follows
Jan 22, 2010 This directory contains DIII-D eqdsks from and experiment performed March 4, 2008. This experiment had discharges which covered a range of plasma currents, toroidal fields and plasma triangularities. The following discharges were part of a four point current scan (0.5-1.5 MA) at a constant toroidal magnetic field (2.1T) and at a constant shape (average triangularity 0.55). These discharges were run at an approximately constant normalized toroidal beta (beta_n ~ 2.1-2.4). The pedestal temperature and density were not constant in the scan. The list of shots and currents for the eqdsks in this directory. These are the eqdsks that were used for the ONETWO analysis as part of the profiles.py analysis, used to generate beam pressure profiles in the analysis. The g-eqdsks are from: /u/groebner/analysis/exps/2008/theory_test/python4. The a-eqdsks were obtained from mdsplus with the writea.pro IDL procedure. These eqdsks were earh run at the time of a specific Thomson laser pulse. The fitting model used for the eqdsks allows for a finite edge current, but the current density and pressure profiles should not be taken as anywhere close to the experimental values. These eqdsks were used for purposes of mapping experimental data on magnetic flux coordinates. shot # Ip (MA) EFIT runid EFIT time 132016 1.50 EFIT04 3023 132014 1.17 EFIT04 3023 132017 0.85 EFIT04 2998 132018 0.51 EFIT04 1948 Results from this experiment have been discussed in" Snyder et al., Phys of Plasmas 16 (2008) 056118 Groebner et al., NF 49 (2009) 085037
The discharges are analyzed with the TEQ equilibrium solver in the Caltrans code. Results of the analysis are to be published on the DIII-D analysis webpage. The TEQ code shows relatively high residuals for the GS solution in the near separatrix region. These discrepancies between the EFIT and TEQ solutions need to be addressed in future.