E. Speth

TL;DR: The development of a large-area RF source for negative hydrogen ions, an official EFDA task agreement, is aiming at demonstrating ITER-relevant ion source parameters as mentioned in this paper, which implies a current density of 200?A?m?2 accelerated D? ions at a source filling pressure of?0.3?Pa and an electron-to-ion ratio of?1 from an extraction area similar to the positive-ion based sources at JET and ASDEX Upgrade and for pulse lengths of up to 1?h.

TL;DR: In this paper, negative hydrogen ion sources for neutral beam systems are linked with an optimization of negative ion formation in hydrogen plasmas, which requires knowledge of the plasma parameters, such as electron density and electron temperature, gas temperature, atomic and molecular hydrogen density, caesium densities (atoms and ions), and negative ion densities.

TL;DR: Wendelstein 7-AS was the first modular stellarator device to test some basic elements of stellarator optimization: a reduced Shafranov shift and improved stability properties resulted in β-values up to 3.4% as discussed by the authors.

TL;DR: In this paper, the characteristics of neutral-beam-heated ASDEX discharges exhibiting either low (L)- or high (H)-confinement are described, and the most important parameter for transition to the H-mode seems to be a high edge electron temperature: Te values of -600 eV only a few centimeters inside the separatrix with radial gradients of ~300 eV/cm.

TL;DR: Stabler et al. as discussed by the authors developed a radio frequency driven negative hydrogen ion source for the ITER neutral beam system, which is an intermediate step between the present small IPP RF sources (1/8 ITER size) and the full size ITER source.