SMuK 2021 – scientific programme

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P: Fachverband Plasmaphysik

P 5: Poster I

P 5.10: Poster

Tuesday, August 31, 2021, 14:00–16:00, P

Terahertz time-domain spectroscopy as a novel plasma diagnostic — •Jente Wubs, Klaus-Dieter Weltmann, and Jean-Pierre van Helden — Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany

In non-thermal plasmas, electrons determine, to a large extent, the plasma chemical behaviour, meaning that electron density measurements are crucial for understanding plasma chemical phenomena. In the case of low-pressure plasmas, Langmuir probes are commonly used for determining electron-related plasma parameters. However, at atmospheric pressure, these probes can no longer be reliably used due to their perturbative characteristics. Terahertz time-domain spectroscopy (THz-TDS) is a novel diagnostic technique for spectroscopic investigations of plasma densities, independent of the pressure. This technique requires ultrafast femtosecond laser pulses for the generation and detection of a broadband electromagnetic signal in the THz range. The signal is sampled in the time-domain using the principle of asynchronous optical sampling (ASOPS) and is subsequently Fourier transformed to obtain spectral information, with a resolution of 1 GHz. This approach allows for electron density measurements with high temporal resolution, whilst simultaneously yielding information on molecular densities within the plasma. This contribution explains the working principle of ASOPS-based THz-TDS. In addition, an exploratory characterisation of the experimental setup will be presented, including an overview of the possibilities and limitations for measuring with spatial resolution.