Paper PS-ThP24
A System of Radical Probes for Plasma Characterization

Thursday, November 10, 2016, 6:00 pm, Room Hall D

The current state-of-the-art methods to identify presence of radical species in vacuum chambers are optical methods, which suffer from the lack of spatial resolution and require expensive optical equipment. Center for Plasma Material Interactions (CPMI) at the University of Illinois aims to develop a probe array (catalytic probe) to measure concentration of reactive gas spices in low temperature plasma with high temporal and spatial resolution. Radical probes as plasma diagnostic device will be used to determine plasma parameters in helicon plasma source. The basic principle and advantage of a probe array is that is has several sensitive elements capable to distinguish between different gas species. The sensitive element has a size of several millimetres with a nanostructured chemically sensitive to specific reactive gas species surface. The nanostructured surface is positioned right on top of a thermocouple [1]. The nanostructured probe surface provides efficient recombination of active species with subsequent energy release as a heat. The system consists of additional two probes, first to obtain the overall heat flux on probe array, and the second is a reference probe with surface chemically active to all gases. The thermocouple detects the heat released after recombination and gives immediate voltage signal output. The array of several probes is capable to distinguish between different gas species with sub centimeter spatial resolution. The probes give accurate results in a broad range of reactive species concentrations from about 10¹⁹ to 10²² m^{− 3}.

Reference:

[1] M Mozetič, M Drobnič, A Pregelj, K Zupan, Determination of density of hydrogen atoms in the ground state, Vacuum, Volume 47, Issues 6–8, June–August 1996, Pages 943-945, ISSN 0042-207X