Aachen PK 2003 – wissenschaftliches Programm
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P: Plasmaphysik
P 16: Plasma Diagnostics
P 16.4: Vortrag
Donnerstag, 20. März 2003, 16:30–16:50, FO2
The Hα minimum at the transition from a recombining to an ionizing plasma — •Uwe Wenzel and Dennis Schröder — Max-Planck-Institut für Plasmaphysik, Bereich Plasmadiagnostik, 10117 Berlin, BRD
A hydrogen plasma in ionization balance has an Hα emission maximum at the norm temperature T*. Plasmas out of ionization balance are either ionizing or recombining depending on the temperature Te. In contrast to the ionization balance the Hα emission exhibits a minimum at the transition between these states. This effect is experimentally demonstrated in the plasma generator PSI-II. A hydrogen plasma is cooled down by puffing additional gas. As the measurements and the modelling show, the minimum occurs near T* at 1.3 eV. An interesting application can be made to analyze ELM (edge localized modes) pulses travelling through a recombining divertor plasma in a tokamak. By the short increase of Te the recombining plasma is switched into an ionizing state. Data from the ASDEX Upgrade tokamak is presented which shows an Hα response running through the minimum (inverse ELMs). A different composition of ELM pulses arriving in the inner and outer divertor is found.