Bremen 2017 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

P: Fachverband Plasmaphysik

P 8: Plasma Diagnostics II

P 8.3: Talk

Tuesday, March 14, 2017, 09:20–09:35, HS 1010

Phase resolved polarization measurements in a capacitively coupled rf-plasma in hydrogen — •Philipp Ahr, Tsanko V. Tsankov, Dirk Luggenhölscher, and Uwe Czarnetzki — Institute for Plasma and Atomic Physics, Ruhr University Bochum, 44801 Bochum, Germany

Anisotropy in the electron excitation in a plasma leads to a measurable polarization of the gas emitted light. The effect is strongest for lines with Δ j = 1. The electron beams in CCP offer such anisotropy in the excitation and provide new means for plasma diagnostics.

Here, the polarization ratio P of the Balmer-α line and of the molecular Fulcher-α band in hydrogen plasma is measured over the time by phase resolved optical emission spectroscopy (PROES). Due to the low dissociation degree the Balmer-α emission is mainly from dissociative excitation of the hydrogen atoms. The measurements are done for different values of the neutral gas pressure and the substrate bias. Different structures are observed in the space-time diagrams of the polarization. These are shown to be directly connected to the known electron dynamics in the plasma. However, also additional temporal structures in the polarization are obtained. A simple model is developed to estimate the observed polarization ratio in the discharge.