The importance of thermal dissociation in CO2 microwave discharges investigated by power pulsing and rotational Raman scattering

TitleThe importance of thermal dissociation in CO2 microwave discharges investigated by power pulsing and rotational Raman scattering
Publication TypeJournal Article
Year of Publication2019
AuthorsD.CM van den Bekerom, J.M Palomares-Linares, T. Verreycken, E.M van Veldhuizen, S. Nijdam, G. Berden, W.A Bongers, M.CM van de Sanden, G.J van Rooij
JournalPlasma Sources Science and Technology
Volume28
Issue5
Pagination055015
Abstract

The input power of a CO2 microwave plasma is modulated at kHz rate in scans of duty cycle at constant average power to investigate gas heating dynamics and its relation to dissociation efficiency. Rotational temperature profiles obtained from rotational Raman scattering reveal peak temperatures of up to 3000 K, while the edge temperature remains cold (500 K). During the plasma 'OFF'-period, the gas cools down convectively, but remains overall too hot to allow for strong overpopulation of vibrational modes (2200 K in the core). Fast optical imaging monitors plasma volume variations and shows that power density scales with peak power. As dissociation scales with observed peak rotational temperature, it is concluded that thermal processes dominate. A simple 0D model is constructed which explains how higher power density favors dissociation over radial energy transport. Thermal decomposition is reviewed in relation to quenching oxygen radicals with vibrationally excited CO2, to reflect on earlier reported record efficiencies of 90%.

DOI10.1088/1361-6595/aaf519
Division

MaSF

Department

NFC

PIDd479f828f6ef5a525b2952aaa0033acb
Alternate TitlePlasma Sources Sci. Technol.
LabelOA
Attachment: 

Go back one page.