Hannover 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
P: Fachverband Plasmaphysik
P 18: Poster: Diagnostics
P 18.1: Poster
Donnerstag, 11. März 2010, 16:00–18:00, Lichthof
Improved chopping of a lithium beam for plasma edge diagnostic at ASDEX Upgrade. — •Matthias Willensdorfer1, Elisabeth Wolfrum2, Josef Schweinzer2, Friedrich Aumayr1, and the ASDEX Upgrade Team2 — 1lnstitut fur Angewandte Physik, Technische Universität Wien, EURATOM-ÖAW Ass., Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria — 2Max-Planck-Institut für Plasmaphysik, EURATOM Ass., Boltzmannstr. 2, D-85748 Garching, Germany
The lithium beam diagnostic at ASDEX Upgrade routinely delivers electron density edge profiles by lithium beam impact excitation spectroscopy (Li-IXS). An accurate background subtraction requires a periodically chopped lithium beam. A new improved chopping system was developed and installed. The new chopping system involves a voltage modulation for the extractor electrode and one for the deflection plates.
The modulation of the extractor electrode reduced the unused portion of lithium ions. An improved stability of the beam with respect to its position was found. Furthermore the data suggested an extended emitter lifetime and less sparks. The extractor chopping also surprised with its insensitivity to sparks.
The deflection chopping experiments demonstrated that beam chopping in the kHz range is possible. The significantly higher modulation frequency of the deflection chopping revealed a slightly lower observed electron density in the outer region (ρp > 1.05) during edge localized modes (ELMs) due to the improved background subtraction. A better accuracy could also be achieved during other fast transient phenomena.