Erlangen 2018 – scientific programme
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P: Fachverband Plasmaphysik
P 16: Low Pressure Plasmas II
P 16.5: Talk
Wednesday, March 7, 2018, 15:15–15:30, KI 1.174
Plasma characteristics of CERN’s Linac4 H− ion source investigated by OES and PIC modelling — •Stefan Briefi1,2, Stefano Mattei3, David Rauner1,2, Jacques Lettry3, and Ursel Fantz1,2 — 1Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching — 2AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg — 3CERN, 1211 Geneva 23, Switzerland
At CERN an upgrade of the LHC injector chain is currently being implemented what includes the installation of a linear accelerator based on negative hydrogen ions, the Linac4. The ion source of Linac4 relies on the generation of H− ions in an inductively coupled low pressure hydrogen plasma (RF frequency 2 MHz, maximum RF power 100 kW). A dedicated optimization of the H− yield with respect to operational parameters or design properties of the ion source requires a detailed knowledge of the plasma parameters. They have been determined by optical emission spectroscopy measurements in combination with a PIC model calculating self-consistently the spatially resolved plasma parameters as a result from the coupling of the RF field to the discharge. A detailed assessment of the H− production and destruction processes close to the extraction aperture enabled an explanation of the experimentally observed trends in the extracted H− currents. In the next step, the PIC model is going to be applied for predictive modelling for a further optimization of the ion source design. The gained insights are also highly valuable for a more detailed understanding of large scale RF-driven H− sources for the neutral beam injection systems for ITER because of the similarities of the underlying processes.