Hannover 2020 – scientific programme

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P: Fachverband Plasmaphysik

P 3: Low-temperature plasma and applications 1

P 3.4: Talk

Monday, March 9, 2020, 15:00–15:15, b302

AC modulation technique for RFEA measurements — •Christian Lütke Stetzkamp, Tsanko Vaskov Tsankov, and Uwe Czarnetzki — Institute for Plasma and Atomic Physics, Ruhr University Bochum, D-44780 Bochum, Germany

Retarding field energy analyzers (RFEA) are an important diagnostic tool to measure the ion velocity distribution function (IVDF) in low-pressure plasmas. However, their dynamic range is usually limited to about one order of magnitude. RFEAs can in principle also measure the distribution function of the electrons that overcome the sheath potential and escape the plasma. However, in this case the capabilities of the devices are even more limited.

Here, a method is presented, that strongly increases the dynamic range of the RFEA measurements. It is based on an analog AC modulation technique that is similar to those used for Langmuir probe measurements. The modulated response signal is detected by a Lock-In amplifier to reduce the influence of noise on the measurement. First measurements show very promising results, in which a dynamic range of about 3 orders of magnitude is easily achieved. In this talk the method will be presented and its characteristics will be discussed.