Validation of deuterium neutral density measurements in NSTX-U using the Monte Carlo neutral transport code DEGAS 2
Abstract
In NSTX-U, deuterium neutral density nD profiles are inferred at the outboard midplane from deuterium Balmer- α (D- α) emission measured with a filtered camera (Edge Neutral Density Diagnostic, ENDD). nD measurements obtained from D- α emissivity are validated using the Monte Carlo neutral transport code DEGAS 2. Contributions to emissivity due to electron impact excitation and molecular processes are estimated with DEGAS 2 towards assessing the direct use of ENDD for nD estimates. Experimental measurements and DEGAS 2 simulations were compared over a database of L-mode discharges, showing good agreement in D- α emissivity profiles. D- α emissivity generally peaked at larger radii in simulations, while far-SOL emission was under predicted. A scan in far SOL plasma parameters in DEGAS 2 showed that a small increase in Te, ne improved the agreement with experimental profiles, pointing to the possible importance of intermittent transport. One-way coupling of DEGAS 2 with UEDGE fluid simulations is underway to study fueling and neutral penetration in NSTX-U discharges.
Prepared for USDOE SC-FES under Contracts: DE-AC52-07NA27344 (LLNL), DE-AC02-09CH11466 (PPPL), DE-FG02-99ER54524 (Columbia U.).- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- 2019
- Bibcode:
- 2019APS..DPPG10143S