Hannover 2020 – scientific programme

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P: Fachverband Plasmaphysik

P 19: Helmholtz Graduate School 4 and Magnetic confinement 4

P 19.2: Talk

Thursday, March 12, 2020, 11:25–11:50, b305

Influence of the magnetic filter field on the source and beam performance at the large negative ion source ELISE — •Isabella Mario, Dirk Wünderlich, Federica Bonomo, and Ursel Fantz — Max-Planck-Institut für Plasmaphysik, Garching, Germany

The neutral beam injection (NBI) system for ITER is based on RF sources for production of negative ions. The ELISE test facility (1/2 ITER source, 1m×1m beam) plays a key role in demonstrating the scalability of the source performance between the prototype source (1/8 ITER source) to the full size ITER NBI source. Ion source requirements have to be combined with beam power uniformity (>90% for ITER) to ensure an adequate beam transmission through the beamline. To minimize the destruction of negative ions by electron collisions in the plasma, the electron density and temperature close to the extraction area are reduced by a horizontal magnetic filter field. This, combined with electric fields and pressure gradients, gives rise to plasma drifts in the vertical direction, which affect the plasma properties and the beam profile. In this work the effect of the filter field on the plasma properties close to the extraction system and on the vertical beam profile at the ELISE test facility is presented. The aim is to study the global effect of the filter field on the source performance and beam uniformity. Plasma parameters such as positive and negative ion density and plasma potential are monitored 2 cm from the extraction apertures; several beam diagnostic tools provide accelerated beam current and divergences with a vertical spatial resolution of 4 to 5 cm.