LXCat is an open‐access platform (http://www.lxcat.net) for curating data needed for modeling the electron and ion components of technological plasmas. The data types presently supported on LXCat are scattering cross sections and swarm/transport parameters, ion‐neutral interaction potentials, and optical oscillator strengths. Twenty‐four databases contributed by different groups around the world can be accessed on LXCat. New contributors are welcome; the database contributors retain ownership and are responsible for the contents and maintenance of the individual databases. This article summarizes the present status of the project.

Laser scattering provides a very direct method for measuring the local densities and temperatures inside a plasma. We present new experimental results of laser scattering on an argon atmospheric pressure microwave plasma jet operating in an air environment. The plasma is very small so a high spatial resolution is required to study the effect of the penetration of air molecules into the plasma. The scattering signal has three overlapping contributions: Rayleigh scattering from heavy particles, Thomson scattering from free electrons and Raman scattering from molecules. The Rayleigh scattering signal is filtered out optically with a triple grating spectrometer. The disentanglement of the Thomson and Raman signals is done with a newly designed fitting method. With a single measurement we determine profiles of the electron temperature, electron density, gas temperature, partial air pressure and the N 2 /O 2 ratio, with a spatial resolution of 50 µm, and including absolute calibration.

Technologies based on non-equilibrium, low-temperature plasmas are ubiquitous in today’s society. Plasma modeling plays an essential role in their understanding, development and optimization. An accurate description of electron and ion collisions with neutrals and their transport is required to correctly describe plasma properties as a function of external parameters. LXCat is an open-access, web-based platform for storing, exchanging and manipulating data needed for modeling the electron and ion components of non-equilibrium, low-temperature plasmas. The data types supported by LXCat are electron- and ion-scattering cross-sections with neutrals (total and differential), interaction potentials, oscillator strengths, and electron- and ion-swarm/transport parameters. Online tools allow users to identify and compare the data through plotting routines, and use the data to generate swarm parameters and reaction rates with the integrated electron Boltzmann solver. In this review, the historical evolution of the project and some perspectives on its future are discussed together with a tutorial review for using data from LXCat.

In this paper, we review the main challenges related to laser Thomson scattering on low temperature plasmas. The main features of the triple grating spectrometer used to discriminate Thomson and Raman scattering signals from Rayleigh scattering and stray light are presented. The main parameters influencing the detection limit of Thomson scattering are reviewed. Laser stray light and plasma emission are two limiting factors, but Raman scattering from molecules inside the plasma will further decrease it.In the case of non-thermal plasmas at high pressure, Thomson scattering is the only technique which allows us to obtain the electron density without any prior knowledge of the plasma properties. Moreover, very high 3D spatial and temporal resolutions can easily be achieved. However, special care still needs to be taken to verify that Thomson scattering is non intrusive. The mechanisms that will lead to possible measurement errors are discussed. The wavelength-resolved scattering signal also allows us to get direct information about the electron energy distribution function in the case of incoherent light scattering.Finally, we discuss some recent applications of Thomson scattering on atmospheric pressure plasma jets, but also in the field of electron collision kinetics. Thomson scattering can be applied on atomic but also molecular plasmas. In the latter case, one needs to take into account the possible contribution of rotational Raman scattering.

This work presents the results of Thomson scattering measurements, optical emission spectroscopy and laser absorption spectroscopy applied to a high pressure nanosecond pulsed helium microdischarge. All data are recorded with high temporal resolution, giving an insight into the processes determining the discharge dynamics. From Thomson scattering measurements, the electron velocity distribution function is determined. Photoionization of helium Rydberg molecules presents a complication for the direct measurement of the electron density by Thomson scattering. Laser pulse energy variation measurements however allow to obtain absolute Rydberg state densities to be obtained. For the first time, the electron velocity distribution function and total Rydberg molecules density for a highpressure pure helium discharge are reported in this paper. These measurements provide new insights into high pressure pure helium discharge chemical pathways.

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In this paper, we discuss the experimental results presented in Schregel et al (2016 Plasma Sources Sci. Technol. 25 054003) on a high pressure micro-discharge operated in helium and driven by nanosecond voltage pulses. A simple global plasma chemistry model is developed to describe the ions, excited atomic and molecular species dynamics in the ignition and early afterglow regimes. The existing experimental data on high pressure helium kinetics is reviewed and critically discussed. It is highlighted that several inconsistencies in the branching ratio of neutral assisted associative and dissociative processes currently exist in the literature and need further clarification.The model allows to pinpoint the mechanisms responsible for the large amounts of Rydberg molecules produced in the discharge and for the helium triplet metastable state in the afterglow. The main losses of electrons are also identified. The fast quenching of excited He (n > 3) states appears to be a significant source of Rydberg molecules which has been previously neglected. The plasma model finally draws a simplified, but still accurate description of high pressure helium discharges based on available experimental data for ion and neutral helium species.

The optical emission spectra of high pressure CO2 microwave plasmas are usually dominated by the C2 Swan bands. In this paper, the use of the C2 Swan bands for estimating the gas temperature in CO2 microwave plasmas is assessed. State by state fitting is employed to check the correctness of assuming a Boltzmann distribution for the rotational and vibrational distribution functions and, within statistical and systematic uncertainties, the C2 Swan band can be fitted accurately with a single temperature for rotational and vibrational levels. The processes leading to the production of the C2 molecule and particularly its d 3 Π g state are briefly reviewed as well as collisional relaxation times of the latter. It is concluded that its rotational temperature can be associated to the gas temperature of the CO2 microwave plasma and the results are moreover cross-checked by adding a small amount of N2 in the discharge and measuring the CN violet band system. The 2.45 GHz plasma source is analyzed in the pressure range 180–925 mbar, for input microwave powers ranging from 0.9 to 3 kW and with gas flow rates of 5–100 l min−1. An intense C2 Swan bands emission spectrum can be measured only when the plasma is operated in contracted regime. A unique temperature of about 6000 ± 500 K is obtained for all investigated conditions. A spectroscopic database is constructed using the recent compilation and calculations by Brooke et al (2013 J. Quant. Spectrosc. Radiat. Transfer 124 11–20) of the line strengths and molecular constants for the C2 (d 3 Π g −a 3 Π u ) Swan bands system and made available as supplementary material in a format compatible with the open source MassiveOES software.