Previous simulation used prescribed time-dependent equilibrium quantities that are based on the experimental equilibrium reconstruction. Using TEQ equilibrium solver in PTRANSP eliminates additional constrains on predicted profiles. The figure below shows the predicted and reconstructed q-profiles at 5.2 sec. The q-profile from experimental has a local minimum in the region of internal transport barrier. The predicted q-profile is significantly modified with the local minimum shifted towards magnetic axis.
The PTRANSP simulation 1554406A44 with the ten times ExB flow shear scaling factor (FACEXB=10) is completed. A notable effect on the electron and ion temperatures is observed. The temperatures are higher comparing to the previous simulations with FACEXB=0 (154406A41), FACEXB=1 (154406A30), and FACEXB=2 (154406A38). The main conclusion from these simulations is that the experimental level of ExB flow shear is low enough to have any significant effect on the anomalous transport.
The role of the ExB flow shear on the predicted temperature profiles for the DIII-D discharge 154406 is investigated using the FACEXB scaling factor. I noticed a very small change in the predicted temperatures when this factor is set to 0 (154406A41), 1 (154406A30), and 2 (154406A38). Another simulation (154406A44) with the FACEXB factor set to 10 is also started.
The boundary conditions have been moved from 0.8 to 0.9 in the simulation of the electron temperature profile for the DIII-D discharge 154406 (154406A40). The ion temperature is not evolved. The predicted temperature profile agree with the experimental profile at approximately the same level as in the simulation with the boundary condition set at 0.8 (154406A30).
The predicted electron temperature profile shown as a solid curve is compared with the experimental temperature profile shown as dashed curve.
The drift resistive inertial ballooning modes (DRIBM) are destabilized by the density gradients. These modes are strongly stabilized by plasma temperatures. They are usually unstable in the plasma edge region close to the separatrix. The DRIBM modes are expected to be stable in the plasma core region of H-mode discharges. However, PTRANSP analysis of the DIII-D discharge 154406 shows that these modes are unstable in the region from 0.3 to 0.7 of normalized minor radius:
Effective electron (left) and ion (right) thermal diffusivities computed using the MMM7.1 model in the modeling of DIII-D discharge 154406 by the PTRANSP code.
The DRIBM model includes contributions from other MHD modes in addition to the drift resistive ballooning modes that can be unstable in this region. However, the validation of predicted temperature profiles hints that these modes are probably should be stable and DRIBM predicts significantly larger level of transport than expected. Additional validation of DRIBM is necessary. In particular, the effects associated with the large poloidal beta or large plasma currents such as Shafranov shift stabilization in DRIBM might need to be revisited.
Predicted electron (left) and ion (right) temperature profiles in the PTRANSP simulation of the DIII-D discharge 154406 using the Weiland, ETG, and DRIBM components of the MMM7.1 model.
The temperature profiles are predicted using the Weiland and ETG components of the Muti-Mode Model (MMM7.1). The predicted temperature profiles are compared with the corresponding temperatures from interpretive simulations (154406A19). Four PTRANSP simulations are completed. These simulations are: (1) Only electron temperature is evolved (154406A28); (2) Only ion temperature is evolved (154406A29); (3) Electron and ion temperatures are evolved (154406A30); and (4) Electron and ion temperature as well as toroidal momentum are evolved (154406A31).
The electron temperature profile in the PTRANSP simulation 154406A28.
The ion temperature profile predicted in the PTRANSP simulation 154406A29.
The electron (left) and ion (right) temperature profiles predicted in the PTRANSP simulation 154406A30.
The electron (left) and ion (right) temperature profiles predicted in the PTRANSP simulation 154406A31.
It is somewhat unexpected that a that better agreement between predicted and experimental profiles is found in the simulations in which the electron and ion temperatures are evolved simultaneously. Neither simulation can accurately reproduce the location of internal transport barrier in the electron temperature profile. The reason is a rather significant electron thermal transport from both the Weiland component (TEM and ITG modes) and ETG component of MMM7.1 that destroys ITB from strong off-axis ECR heating.
The ECR heating profile (left) and electron thermal effective diffusivities (right) computed in the Weiland and ETG components of MMM7.1 in the predictive PTRANSP simulation 154406A28.
