Sensitivity of Line-Average Density to Separatrix Density and Particle Sources in Ohmic and L-mode Regimes

Predictions of plasma density profiles depend on separatrix density and neutral particle sources, such as gas puff, neutral beams, and pellets. The neutral particle density at the separatrix is not routinely measured but can be adjusted to match the line average density of the discharge. Hence, the core particle transport determines the required separatrix neutral density from the gas puff. A series of scans of the neutral particle source rates and separatrix density has been performed using the IPS-FASTRAN workflow [1,2] to predict plasma profiles of temperature and density. This reveals insights into the sensitivity of the core transport profile prediction to the boundary electron, neutral density, and neutral beam particle source. Prediction of the electron and ion temperature and electron density using the TGLF transport model with SAT2 [3] saturation model matched the measured profiles in 11 DIII-D L-mode discharges to within 7% using experimental boundary conditions at r/a=0.98 and adjusted boundary neutral density. To assess the impact of the predicted SOL opaqueness to neutral penetration in ITER, predicted profiles with zero-particle source rates have been investigated while scanning the separatrix density within the IPS-FASTRAN/TGLF-SAT2 [4] workflow. The electron density profile is predicted to be peaked, even without a particle source, due to the transport pinch effect.