Stuttgart 2012 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
P: Fachverband Plasmaphysik
P 16: Magnetischer Einschluss II/Plasmalichttechnik
P 16.4: Talk
Thursday, March 15, 2012, 11:40–11:55, V57.01
Expanding Structures in Magnetized Plasmas — •Timo Schröder1, Olaf Grulke1, Thomas Klinger1,2, Rod Boswell3, and Christine Charles3 — 1Max-Planck-Institut für Plasmaphysik, EURATOM Association, Greifswald — 2E.-M.-A. Universität, Greifswald — 3Australian National University, Canberra
Double layers (DL, i.e. localized boundary layers between two plasma regimes of significantly different plasma potential, ΔΦ > kBTe/e) result in strong electric fields. One can distinguish between current-carrying and current-free DLs. Especially the latter can form under various conditions. Although they have been observed in both space and laboratory plasmas the mechanism of their formation is still under debate. Laboratory experiments have shown that current-free DLs usually form due to an expanding magnetic field and/or an expanding device geometry. However, in early experiments Hairapetian and Stenzel (1988) observed an acceleration of ions in the ignition phase of a thermionic discharge due to a propagating DL. The present work uses rf discharges to investigate the mechanisms of the ion acceleration and the DL formation. Static DLs can already be observed in the plasma expansion created by a pulsed rf source. By using a fast valve it is possible to inject the working gas directly into the source region and the expansion chamber can be kept almost at base pressure. It is demonstrated that the combination of a short gas puff and a short rf pulse finally leads to a propagating DL. Measurements on its spatio-temporal dynamic and effect on the ion kinetics will be presented.