Diagnostic based modelling of radio-frequency driven atmospheric pressure plasmas

Abstract

Diagnostic based modelling (DBM) actively combines complementary advantages of numerical plasma simulations and relatively simple optical emission spectroscopy (OES). DBM is employed to determine absolute atomic oxygen ground state densities in a helium–oxygen radio-frequency driven atmospheric pressure plasma jet. A comparatively simple one-dimensional simulation yields detailed information on electron properties governing the population dynamics of excited states. Important characteristics of the electron dynamics are found to be largely insensitive to details of the chemical composition and to be in very good agreement with space and phase-resolved OES. Benchmarking the time and space resolved simulation allows us to subsequently derive effective excitation rates as the basis for DBM with simple space and time integrated OES. The population dynamics of the upper O 3p 3P (λ = 844 nm) atomic oxygen state is governed by direct electron impact excitation, dissociative excitation, radiation losses and collisional induced quenching. Absolute values for atomic oxygen densities are obtained through tracer comparison with the upper Ar 2p1 (λ = 750.4 nm) state. The presented results for the atomic oxygen density show excellent quantitative agreement with independent two-photon laser-induced fluorescence measurements.

Controlled production of atomic oxygen and nitrogen in a pulsed radio-frequency atmospheric-pressure plasma

“…Simulated spectra are fitted to the measurements to determine the gas temperature, by assuming that the rotational distribution is in thermal equilibrium with the neutral-gas temperature [42,43] as previously undertaken in high-pressure discharges for applications including, e.g. combustion [44], electric propulsion [45] and biomedicine [46][47][48]. Our spectrum simulation is based on molecular constants from [49] and line strength expressions from [50] for intermediate coupling of upper and lower state between Hund's case (a) and (b).…”

Interactions of a Non‐Thermal Atmospheric Pressure Plasma Effluent with PC‐3 Prostate Cancer Cells

“…[8][9][10][11] Thus far there is evidence that these plasmas may find applications in sterilisation, [1,2,[12][13][14][15] wound healing, [1,2,16] and cancer therapies. [3,[17][18][19][20][21][22][23] Low gas temperatures when operated in helium gas ($30-50 8C) [24,25] makes them highly suitable for such applications, as thermal damage to heat sensitive surfaces may be avoided. Of paramount importance to any future use of plasma devices in medicine are the end effects that such plasma sources induce in the liquid environment containing biological material.…”

Use of particle-in-cell simulations to improve the actinometry technique for determination of absolute atomic oxygen density

“…Work done by previous authors has shown that application of the actinometry method does not always yield results that reflect the true atomic oxygen number density in the plasma. The validity of actinometry for atomic oxygen has been investigated for various plasma sources: RF capacitive plasma [14,15,16], ECR source [17], DC glow discharge [18], microwave source [19,20], helicon source [21], inductive source [22], and micro-scale atmospheric pressure jet source [23]. Walkrup et al [14] investigated the validity of actinometry for atomic oxygen in RF capacitive plasmas containing both pure O 2 and O 2 /CF 2 mixtures by examining line emission intensity ratios.…”