title: Determination of discharge parameters via OES at the Linac4 H⁻ ion source.
abstract: Optical emission spectroscopy (OES) measurements of the atomic Balmer series and the molecular Fulcher transition have been carried out at the Linac4 ion source in order to determine plasma parameters. As the spectroscopic system was only relatively calibrated, the data evaluation only yielded rough estimates of the plasma parameters (T(e) ≈ 1.2 eV, n(e) ≈ 1 × 10(19) m(-3), and n(H/)n(H2) ≈ 0.5 at standard operational parameters). The analysis of the Fulcher transition revealed a non-thermal "hockey-stick" rotational population of the hydrogen molecules. At varying RF power, the measurements at the on-axis line of sight (LOS) showed a peak in the rotational temperatures between 25 and 40 kW of RF power, whereas a steady decrease with power was observed at a tilted LOS, indicating the presence of strong plasma parameter gradients.
authors.affiliation: AG Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Briefi
authors.affiliation: Linac4 Ion Source Team, CERN-ABP, 1211 Geneva 23, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Fink
authors.affiliation: Linac4 Ion Source Team, CERN-ABP, 1211 Geneva 23, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Mattei
authors.affiliation: Linac4 Ion Source Team, CERN-ABP, 1211 Geneva 23, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Lettry
authors.affiliation: AG Experimentelle Plasmaphysik, Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Fantz