Hannover 2020 – scientific programme

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P: Fachverband Plasmaphysik

P 16: Poster Session 3

P 16.10: Poster

Wednesday, March 11, 2020, 16:30–18:30, Empore Lichthof

First Steps towards TALIF Measurements of the H Atom Velocity Distribution Function and Density in Negative Ion Sources — •Frederik Merk, Christian Wimmer, Stefan Briefi, Emile Carbone, Ursel Fantz, and the NNBI-Team — Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany

H⁻ (and D⁻) ion sources are required for neutral beam injection on the ITER fusion device. The test facility BATMAN Upgrade (BUG) is used to investigate the physics of these sources. H⁻ ions are produced in a low-temperature, low-pressure plasma environment by surface-conversion of H or H_x⁺ at a (caesiated) low work function surface. As the dominant process is the H atom conversion, the H⁻ conversion yield depends on the flux of H atoms onto the surface. This flux is determined by the H atom velocity distribution function and the corresponding density. In order to determine reliable values for both parameters a TALIF (two-photon absorption laser induced fluorescence) system will be installed at the test facility. For the installation of the diagnostic under the harsh environment of the ion source (100 kW rf power, 45 kV high voltage), a stepwise approach is chosen. First, the TALIF implementation scheme and calibration is tested for O atoms in a small plasma torch. Then, a TALIF system for H is installed in a controlled environment on a small H₂ ICP experiment. Finally, the optimized diagnostic system is transferred to BUG, which will be the first time that such a system is installed at a H⁻ ion source. The design and the current status of the TALIF system is presented.