SMuK 2021 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
P: Fachverband Plasmaphysik
P 17: Poster II
P 17.32: Poster
Friday, September 3, 2021, 14:00–16:00, P
3D Monte-Carlo PIC modeling of plasma grid biasing and the co-extraction of electrons in negative ion sources — •Max Lindqvist1, Dirk Wünderlich1, Alessandro Mimo1, Serhiy Mochalskyy1, Adrien Revel2, Tiberiu Minea2, and Ursel Fantz1 — 1Max-Planck-Institut für Plasmaphysik, Garching, Germany — 2Universite Paris-Saclay, CNRS, LPGP, Orsay, France
One of the factors limiting the performance of negative ion sources for the ITER Neutral Beam Injection (NBI) system is the co-extraction of e−. By varying the positive bias potential of the Plasma Grid (PG) with respect to the source walls, the amount and temporal instability of co-extracted e− is strongly decreased. This study investigates the mechanisms of this process by varying the bias of the PG using the already established 3D Monte-Carlo PIC code ONIX. The simulation domain covers the extraction region near one of the PG apertures in the ELISE ion source. In previous PIC simulations of this type, the boundary from the bulk plasma to the simulation domain is characterized by an artificial plasma sheath. Here, for the first time in a 3D PIC code for NBI sources, a flat potential transition is simulated, which allows for biasing the PG without extending the simulation domain to the source walls. Instead, the bias has been indirectly applied by varying the PG potential from −5 V (close to floating) to 1 V (e− attracting sheath) with respect to the plasma potential. In agreement with experimental results, the co-extracted e− current is decreased by over 50 %, caused by an increased flux of e− towards the top and bottom of the PG, following the magnetic field lines.