Evaluation of a microplasma source based on a stripline split-ring resonator

Abstract

Abstract. In this paper, a stripline split-ring resonator microwave-induced plasma source, aimed for integration in complex systems, is presented and compared with a traditional microstrip design. Devices based on the two designs are evaluated using a plasma breakdown test setup for measuring the power required to ignite plasmas at different pressures. Moreover, the radiation efficiency of the devices is investigated with a Wheeler cap, and their electromagnetic compatibility is investigated in a variable electrical environment emulating an application. Finally, the basic properties of the plasma in the two designs are investigated in terms of electron temperature, plasma potential, and ion density. The study shows that, with a minor increase in plasma ignition power, the stripline design provides a more isolated and easy-to-integrate alternative to the conventional microstrip design. Moreover, the stripline devices showed a decreased antenna efficiency as compared to their microstrip counterparts, which is beneficial for plasma sources. Furthermore, the investigated stripline devices exhibited virtually no frequency shift in a varying electromagnetic environment, whereas the resonance frequency of their microstrip counterparts shifted up to 17.5%. With regards to the plasma parameters, the different designs showed only minor differences in electron temperature, whereas the ion density was higher with the stripline design.Keywords: Split-ring resonator, Microwave plasma, Microstrip, Stripline, Plasma, Wheeler cap, Langmuir probe

Improved optogalvanic detection with voltage biased Langmuir probes

“…The data in this region was postprocessed, to calculate the slopes of the U OG (U B ) and U P (U B ) curves above the plasma potential. Curve fitting was performed in Matlab, and, similarly, U PP0 and T e0 (where subscript 0 indicates the plasma parameters of the unperturbed plasma) were calculated from the I-V curves using similar theory as in [17]. However, the electron and ion densities, which too could have been estimated from the I-V curves, were omitted, since such a calculation would have required a reliable approximation of the effective surface area of the floating probe.…”

“…The source meter also measured the current through the plasma, I B , hence, enabling measurements of the plasma's I-V characteristics. The I-V curves were used to calculate the plasma potential, U PP , and electron temperature, T e , in the same way as in [17] assuming collisionless, un-magnetized plasma conditions [23].…”

“…Firstly, at its peak, OG detection often showed to be more sensitive than absorption measurements [15]. Although absorption detectors have evolved far since then, modern OG detectors, based on more stable and reliable technology, have demonstrated fast evolution and promising performance [16][17][18]. Secondly, and most interestingly, the fundamental differences between OG and absorption detectors make new spectrometer designs possible.…”

“…In previous work, we have demonstrated the use of a miniaturized stripline split-ring resonator (SSRR) as an OG detector for CO 2 [16][17][18]. The SSRR detector has been shown to be both more sensitive and reliable than current competitors, combining high reproducibility [16] with electromagnetic robustness [17].…”

“…The SSRR detector has been shown to be both more sensitive and reliable than current competitors, combining high reproducibility [16] with electromagnetic robustness [17]. Moreover, the volume of the sample cell of the SSRR is less than 100 µl, enabling analysis of extremely small samples [18].…”