He(23 S 1) and He2(a 3Σu +) metastables densities measured in an RF-driven helium plasma using broadband absorption spectroscopy

Nayak, Gaurav; Sadeghi, N.; Bruggeman, Peter

doi:10.1088/1361-6595/ab3691

Cited by 18 publications

(39 citation statements)

References 64 publications

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“…Both, atomic and molecular metastable species are an important source of ionization, for example, due to efficient Penning ionization of impurities. Recently, Nayak et al [ 33 ] measured metastable excimer densities of around 2.5 × 10 18 m −3 in the sheaths of a capacitively coupled helium plasma. Additionally, Schregel et al [ 34 ] demonstrated the presence of even higher excited Rydberg states in a pulsed helium atmospheric pressure discharge and assumed them to be an important energy source in the afterglow.…”

Section: Resultsmentioning

confidence: 99%

Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

Golda

Biskup

Layes

et al. 2020

Plasma Processes & Polymers

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Due to elevated pressure, cold atmospheric pressure plasmas generate excimer species, which can emit highly energetic photons, thus transferring energy inside the discharge and to treated substrates. However, they are difficult to assess, as they are absorbed by air or window material. Here, we present a method to measure vacuum ultraviolet photons using a monochromator with an aerodynamic window. The emission spectra of a radiofrequency‐excited atmospheric plasma jet were analyzed for typical gas mixtures. The data indicate that helium excimers contribute notably to the excitation of molecular and atomic species. The emission intensities do not follow densities of ground‐state species, underlining the variety of excitation channels and the change of the electron energy distribution function under changing gas composition.

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Section: Resultsmentioning

confidence: 99%

Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

Golda

Biskup

Layes

et al. 2020

Plasma Processes & Polymers

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“…The plasma reactor used in this study generates an RF-driven capacitively coupled glow discharge in a water-cooled parallel plate electrode type configuration. A detailed description of the reactor is provided in 31,32 . The reactor is designed to facilitate access for optical diagnostics along the length of the plasma (19.1 mm) and within the inter-electrode spacing of 2 mm.…”

Section: A Experimental Setupmentioning

confidence: 99%

“…The absolute densities of Ar atoms in metastable and resonant states across the plasma gap were determined by employing broadband absorption spectroscopy. The optical configuration for the spectrally resolved measurements is similar as used in 31 and is shown in Fig. 4.…”

Section: E Broadband Absorption Spectroscopymentioning

confidence: 99%

“…The spatial resolution was 40 µm. For the determination of the spatial resolution within the plasma gap, the readers are referred to the procedure described in 31 .…”

Section: E Broadband Absorption Spectroscopymentioning

confidence: 99%

“…The different excited states and corresponding transitions investigated in this study are compiled in Table II The detailed procedure for obtaining the absorption spectrum using broadband absorption spectroscopy is reported in 31,[48][49][50] . In brief, the experimental fractional absorption A(λ ) can be calculated as follows: 49…”

Section: G Absolute Densities Of Atoms In Resonant and Metastable Statesmentioning

confidence: 99%

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Characterization of an RF-driven argon plasma at atmospheric pressure using broadband absorption and optical emission spectroscopy

Nayak

Simeni

Rosato

et al. 2020

Journal of Applied Physics

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Atmospheric pressure plasmas in argon are of particular interest due to the production of highly excited and reactive species enabling numerous plasma-aided applications. In this contribution, we report on absolute optical emission and absorption spectroscopy of a radio frequency (RF) driven capacitively coupled argon glow discharge operated in a parallel-plate configuration. This enabled the study of all key parameters including electron density and temperature, gas temperature, and absolute densities of atoms in highly electronically excited states. The space and time-averaged electron density and temperature were determined from the measurement of the absolute intensity of the electron-atom bremsstrahlung in the visible range. Considering the non-Maxwellian electron energy distribution function, an electron temperature (T e ) of 2.1 eV and an electron density (n e ) of 1.1 × 10 19 m −3 were obtained. The time-averaged and spatially resolved absolute densities of atoms in the metastable (1s 5 and 1s 3 ) and resonant (1s 4 and 1s 2 ) states of argon in pure Ar and Ar/He mixture were obtained by broadband absorption spectroscopy. The 1s 5 metastable atoms had the largest density near the sheath region with a maximum value of 8 × 10 17 m −3 , while all other 1s states had densities of at most 2 × 10 17 m −3 . The dominant production and loss mechanisms of these atoms were discussed, in particular, the role of radiation trapping. We conclude with a comparison of the plasma properties of the argon RF glow discharges with the more common He equivalent and highlight their differences.

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Influence of pulse modulation frequency on helium RF atmospheric pressure plasma jet characteristics

Mahreen

Prakash

Kar

et al. 2022

Contributions to Plasma Physics

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This work investigates the influence of pulse modulation frequency ranging from 50 Hz–10 kHz on the helium RF atmospheric pressure plasma jet's fundamental characteristics. The impact of modulation frequency on plasma jet discharge behaviour, geometrical variation, reactive species emission, and plasma parameters (gas temperature Tg, electron excitation temperature Texc, and electron density (ne)) are studied using various diagnostics such as optical imaging, emission spectra, and thermal diagnostic. From the experiments, it is observed that operating the plasma jet at low pulse modulation frequencies (around 50 Hz) provides enhanced plasma dimensions, higher electron densities and greater optical emission from reactive species (viz., He I, O, OH, N2+, etc.) as compared to the higher modulation frequencies. Besides the low power consumption, three times less gas temperature of the modulated plasma jet than the continuous wave mode makes it more advantageous for the applications. Moreover, the influence of duty cycle (D) and applied RF power (P) on the plasma jet characteristics are also discussed. It is found that 10–40% duty cycle operation provides the most favourable attributes. More importantly, the concern of shorter plasma length in RF plasma jets is overcome by operating at 10–20% duty cycle with increased applied power. This work thoroughly characterizes helium atmospheric pressure RF plasma jet with a wide range of pulse mode operating parameters, which could help to select appropriate operating conditions for various industrial and biomedical applications.

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He(2³ S ₁) and He₂(a ³Σ_u ⁺) metastables densities measured in an RF-driven helium plasma using broadband absorption spectroscopy

Cited by 18 publications

References 64 publications

Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

Characterization of an RF-driven argon plasma at atmospheric pressure using broadband absorption and optical emission spectroscopy

Influence of pulse modulation frequency on helium RF atmospheric pressure plasma jet characteristics

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