Maria Saba, Cristina Muja, Philippe Guillot, Thomas Maho
<div><p>Hospital and urban wastewaters constitute major reservoirs of multidrug-resistant bacteria (MRB), antibiotic resistance genes (ARGs), and persistent pharmaceutical contaminants, which are only partially removed by conventional treatment plants. As a result, these pollutants are frequently detected in treated effluents destined for environmental discharge or reuse, raising serious public health concerns-especially for agricultural irrigation. This study explores a novel immersed dielectric barrier discharge (DBD) plasma source engineered for point-of-use decontamination of wastewater at emission sites. The plasma device was thoroughly characterized by electrical, optical, and chemical diagnostics to elucidate its operating regimes and capacity to generate reactive oxygen and nitrogen species (RONS) at the plasma-liquid interface. Findings demonstrate that the composition of the carrier gas critically shapes the production and transfer of short-and long-lived oxidants into the liquid phase. These results provide quantitative insights that support the ongoing optimization of plasma-based advanced oxidation systems for decentralized water treatment. They further illustrate how the careful control of plasma and gas composition can enhance the formation and transfer of oxidants, contributing to the broader field of plasma-liquid applications for the mitigation of emerging contaminants.</p></div>
Iryna Litovko, Martin Rudolph, André Anders, Alexey Goncharov
The evaporation of droplets in an arc plasma flow under the action of an electron beam injected into the arc plasma and the condition of direct heating of microdroplets by beam electrons are considered. Analytical modeling shows that droplets ≤1 μm in size can be completely evaporated over time scales typical for cathodic arc deposition systems. It is shown that small microdroplets evaporate more intensively. The lower limit working points in terms of plasma electron density, and the electron energy and density of the injected energetic electrons required for droplet evaporation are found.
In this article, we present a detailed characterisation of a multicusp-assisted inductively coupled RF plasma source for plasma immersion ion implantation (PIII). Using laser-induced fluorescence (LIF) and RF-compensated Langmuir probe diagnostics, we measured ion temperature T i and drift velocity v z in argon plasmas near an immersed electrode. The multicusp configuration enhances plasma density at low pressure, enabling stable operation down to 0.8 mTorr. Timeaveraged measurements show no detectable perturbation near the pulsed electrode, indicating full plasma recovery between high-voltage pulses. LIF-derived potential profiles match Riemann's presheath theory, and ion velocity distributions reveal acceleration consistent with sheath dynamics. These results support the use of LIF for steady-state characterisation of the bulk and presheath regions in PIII systems.
We report numerical results regarding the minimum sustaining coil excitation current for a RF-RF hybrid torch operating at two different frequencies. The first coil is excited at a high-frequency, while the second coil is set at a medium frequency. The filling gas is argon, at atmospheric pressure. We use the modeling software COMSOL Multiphysics to describe the evolution of key parameters when: (i) the distance between the two coils changes, (ii) the power of the high frequency coil changes. We discuss the radial temperature profiles, the axial velocities and the heat convected at the end of the medium-frequency coil. The latter is compared with the total heat conduction to the plasma confinement tube wall.
Peter Donnel, Kevin Obrejan, Yanick Sarazin, Roméo Bigué, Emily Bourne, Guillaume Brochard, Ludovica de Gianni, Guilhem Dif-Pradalier, Xavier Garbet, Virginie Grandgirard, Philipp Krah, Yann Munschy, Protais Matthieu
Gyrokinetic codes are used to simulate transport in tokamak plasmas. In these codes, the distribution functions evolve self consistently with an electromagnetic field. To compute the temporal evolution of the electrostatic potential, a quasi-neutrality equation is solved. In some gyrokinetic codes, the quasi-neutrality solver assumes that the background densities and temperatures are constant in time and on flux surfaces. This assumption, which implicitly uses the so-called δF approach, can break up, in particular at the edge of the plasma which can display large and time evolving poloidal asymmetries.In this paper, a numerical solver of the quasi-neutrality equation accounting for time evolving poloidal asymmetries is presented. This solver is compatible with all electron models (adiabatic, kinetic or hybrid) and written for the long wavelength or the Padé approximations for the polarisation term. The impact of such an improvement is carefully reported on different types of simulations, illustrating when the δF approach forquasi-neutrality is valid and when it fails. A procedure to limit the numerical cost of updating the background profiles in the quasi-neutrality solver is also presented.
Axel Richard, Pascal Brault, Nicolas Froloff, Olivier Aubry, Dunpin Hong, Hervé Rabat
This work establishes a protocol to study via Molecular Dynamics simulation the degradation of Per-and Polyfluoroalkyl Substances (PFAS) in water by hydroxyl radical. To achieve this, molecular dynamics simulations are carried out, using ReaxFF reactive interaction potential. Simulations are carried out under a temperature ramp for determining all possible products. Using this methodology, reaction pathways of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are identified.
Pierre David, Emiliano Fable, Chuanren Wu, Matthias Gehring, Michael Sieben, Berhnard Sieglin, Giovani Tardini, Wolfgang Treutterer
We present the latest updates of the flight simulator of ASDEX Upgrade (AUG), 'Fenix AUG'. Fenix AUG contains simplified models for both the plasma physics and the device operation. The updated version is split into three independent repositories and has been integrated into Docker containers for better management and deployment. The device models can now directly import their configuration from the AUG control system. Although the physics models can be fine tuned to each case, the default settings have been set up to run a large variety of experiments without the need of case-to-case adaptation. Together, the enhancements make Fenix AUG a versatile tool that can be applied to a wide range of applications 'out-of-the-box', such as: to compare simple physics models to the experiment, to assess new controllers within the framework of the existing ones, or, to verify that a planned discharge will follow expected trajectories and will not run into machine or safety limits. An example of each application is showcased to highlight some strengths and limitations of the simulator.
E. Fable, G. Tardini, L. Giannone, the ASDEX Upgrade Team
A new axisymmetric equilibrium solver has been written, called FEQIS (Flexible EQuIlibrium Solver), which purpose is to be used inside integrated modeling of tokamak plasmas. The FEQIS code solves the Grad-Shafranov equation and the "circuit" equations for the external coils and passive conducting structures that are toroidally connected. The code has been specifically equipped with flexibility in choice of circuit connections, and a stripped-down numerical scheme for the solution of the Grad-Shafranov equation through a structure of multi-level simplifications which can be tested against the required accuracy.
Jeanne Bourgeois, Maxime Lesur, Guillermo Cuerva Lazaro, Yusuke Kosuga
In magnetized plasmas, a radial gradient of parallel velocity, where parallel refers to the direction of magnetic field, can destabilise an electrostatic mode called Parallel Velocity Gradient (PVG). The theory of PVG has been mainly developed assuming a single species of ions. Here, the role of impurities is investigated based on a linear, local analysis, in a homogeneous, constant magnetic field. To further simplify the analysis, the plasma is assumed to contain only two ion species - main ions and one impurity species - while our methodology can be straightforwardly extended to more species. In the cold-ion limit, retaining polarization drift for both main ions and impurity ions, and assuming Boltzmann electrons, the system is described by 4 fluid equations closed by quasi-neutrality. The linearized equations can be reduced to 2 coupled equations: one for the electric potential, and one for the effective parallel velocity fluctuations, which is a linear combination of main ion and impurity parallel velocity fluctuations. This reduced system can be understood as a generalisation of the Hasegawa-Mima model. With finite radial gradient of impurity parallel flow, the linear dispersion relation then describes a new instability: the impurity-modified PVG (i-PVG). Instability condition is described in terms of either the main ion flow shear, or equivalently, an effective flow shear, which combines main ion and impurity flow shears. Impurities can have a stabilising or destabilising role, depending on the parameters, and in particular the direction of main flow shear against impurity flow shear. Assuming a reasonable value of perpendicular wavenumber, the maximum growth rate is estimated, depending on impurity mass, charge, and concentration. 17 pages, 12 figures
