Spatially resolved argon microplasma diagnostics by diode laser absorption

Miura, Naoto; Hopwood, Jeffrey

doi:10.1063/1.3531557

Cited by 22 publications

(26 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results showed a linear dependence of T G on p in both experiments (R 2 =0.999 for pure CO 2 and R 2 =0.970 for CO 2 in N 2 ), which was in agreement with previous studies of similar plasma sources [28]. However, as can be seen in the inset of Fig.…”

Section: Resultssupporting

confidence: 78%

Improved optogalvanic detection with voltage biased Langmuir probes

Persson

Berglund

Salehpour

2014

Journal of Applied Physics

View full text Add to dashboard Cite

Optogalvanic detectors show great potential for infrared spectroscopy, especially in cavity enhanced techniques where they, in contrast to ordinary absorption detectors, can perform intracavity measurements. This enables them to utilize the signal-to-noise ratio improvement gained from the extended effective path length inside an optical cavity, without losing signal strength due to the limited amount of light exiting through the rear mirror.However, if optogalvanic detectors are to become truly competitive, their intrinsic sensitivity and stability has to be improved. This, in turn, requires a better understanding of the mechanisms behind the generation of the optogalvanic signal. The study presented here focuses on an optogalvanic detector based on a miniaturized stripline split-ring resonator plasma source equipped with Langmuir probes for detecting the optogalvanic signal. In particular, the effect of applying a constant bias voltage to one of the probes is investigated, both with respect to the sensitivity and stability, and to the mechanism behind the generation of the signal. Experiments with different bias voltages at different pressures and gas composition have been conducted. In particular, two different gas compositions (pure CO 2 and 0.25% CO 2 in 99.75% N 2 ) at six different pressures (100 Pa to 600 Pa) have been studied. It has been shown that probe biasing effectively improves the performance of the detector, by increasing the amplitude of the signal linearly over one order of magnitude, and the stability by about 40% compared with previous studies. Furthermore, it has been shown that relatively straightforward plasma theory can be applied to interpret the mechanism behind the generation of the signal, although additional mechanisms, such as rovibrational excitation from electron-molecule collisions, become apparent in CO 2 plasmas with electron energies in the 1-6 eV range. With the achieved performance improvement and the more solid theoretical framework presented here, stripline split-ring resonator optogalvanic detectors can evolve into a compact, inexpensive and easy-to-operate alternative for future infrared spectrometers.

show abstract

Section: Resultssupporting

confidence: 78%

Improved optogalvanic detection with voltage biased Langmuir probes

Persson

Berglund

Salehpour

2014

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…By using a highly focused laser, the spatially resolved line-integrated density and gas temperature were estimated following a previously published method [30,32]. The line-integrated density of Ar(1s 5 ) was found from the total integrated absorption of laser photons as the wavelength of the laser was scanned through the transition wavelength.…”

Section: Ar(1s 5 ) Absorptionmentioning

confidence: 99%

“…A focused single-mode diode laser was passed through the cut-out shown in Figure 1 and scanned across the plasma in the T-line mode as seen in Figures 2c−2e. Due to length limitations, the details of the absorption setup are described elsewhere [30].…”

Section: Optical Diagnostic Setupmentioning

confidence: 99%

“…The DBD, however, is transient in nature and the low duty-cycle (∼1%) limits the time-averaged electron density to the order of 1 × 10 11 cm −3 [28,29]. Previously, we have studied microplasma sources based on a microstrip split-ring resonator (SRR) [10][11][12][13][14][30][31][32]. Measurements of this plasma have thus far suggested that no instabilities exist.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Instability control in microwave-frequency microplasma

Miura

Hopwood

2012

Eur. Phys. J. D

View full text Add to dashboard Cite

Abstract. Atmospheric argon microplasmas driven by 1.0 GHz power were studied by microwave circuit analyses and spatially-resolved optical diagnostics. These studies illuminate the mechanisms responsible for microplasma stability. A split-ring resonator (SRR) microplasma source is demonstrated to reflect excess microwave power, preventing the ionization overheating instability while limiting electron density to approximately 1 × 10 14 cm −3 and OH rotational temperature to 760 K at 0.76 W. Providing the SRR microplasma with an electrical path to ground, however, allows the microplasma to transition from the SRR mode to the so-called transmission line mode (T-line). This transition is due to matching of the microplasma and transmission line impedances. The higher power T-line mode supports a more intense microplasma with electron density of 1 × 10 15 cm −3 and OH rotational temperature of 1480 K with 15 W absorbed power. While the SRR mode is optimized for ignition and sustaining a stable nonequilibrium plasma, and T-line mode is better suited for driving a hot, high density microplasma. The estimated microwave discharge voltages were 15 V and 35 V in SRR mode and T-line mode, respectively, and the voltages are rather independent of input power. Microplasma stability is due to a combination of impedance mismatching and direct control of power, both inherent to microwave circuitry.

show abstract

“…In the work of Miura and Hopwood [132,133], spatially resolved DLA, by using the Ar 801.4 nm transition (1s5-2p8), was used to study a 900 MHz microstrip split-ring resonator microplasma in argon. Gas temperatures and the Ar 1s5 line-integrated densities were obtained from the atomic absorption lineshape at operating pressures of 100-760 Torr.…”

Section: Diode Laser Absorption (Dla)mentioning

confidence: 99%