Scientific publications

2025

• Refining the modeling strategy for anomalous electron transport in fluid simulations of Hall thrusters via insights from PIC simulations
  
  • Petronio Federico
  • Alvarez Laguna Alejandro
  • Guillon Martin Jacques
  • Bourdon Anne
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2025, 32 (7), pp.073513. Modeling anomalous transport in fluid simulations is a fundamental challenge for developing efficient and robust fluid simulation tools for Hall thrusters. This paper investigates optimal strategies for modeling anomalous transport in such simulations. Using the particle-in-cell (PIC) benchmark (BM) setup of Charoy et al., we demonstrate that various terms in the electron momentum equation can be readily identified. In particular, we show that the assumption of expressing the rate of change of the electron momentum due to instability as proportional to the momentum itself does not hold under these simulation conditions. Subsequently, we present two fluid simulations that replicate the conditions of the PIC BM setup. The first employs the conventional empirical anomalous collision frequency approach. While this model provides generally satisfactory results, it fails to capture specific plasma characteristics. The second fluid model adopts a data-driven approach to represent the anomalous force terms in the momentum equation. This approach furnishes significantly improved results, suggesting that although the anomalous collisionality framework provides meaningful outcomes, it can be effectively replaced by more advanced techniques. (10.1063/5.0274535)
  DOI : 10.1063/5.0274535
• Fast gas heating and peculiarities of temperature measurements by optical emission spectroscopy in nanosecond surface dielectric barrier discharge
  
  • Zhang Bin
  • Kreyder Geoffrey
  • Popov Nikolay
  • Shcherbanev Sergey
  • Starikovskaia Svetlana
  Plasma Sources Science and Technology, IOP Publishing, 2025, 34 (9), pp.095010. The aim of this work is the experimental and theoretical study of nanosecond Surface dielectric barrier discharge (SDBD) parameters in atmospheric pressure air. Measurements of electric current and delivered energy, ICCD images of the discharge at all stages of its evolution, and gas heating in the discharge and near afterglow are performed. The paper presents the results of 2D numerical modeling of the nanosecond SDBD. The results of the calculations are compared with measured data on the dynamics of current, energy input and gas heating. Special attention is paid to the study of the spatial structure of the discharge, in particular, to the distribution of gas temperature and the second positive system emission intensity in the direction perpendicular to the surface of the dielectric. It is shown that the results of temperature measurements in SDBD using optical emission spectroscopy technique are severely influenced by this spatial structure. The parameters of a probe discharge of smaller amplitude, which is formed by a reflected pulse 500 ns after the main discharge, are also calculated. The possibility of using the second diagnostic pulse to measure the gas temperature in the afterglow discharge is discussed. (10.1088/1361-6595/ae00ef)
  DOI : 10.1088/1361-6595/ae00ef
• Survey of the edge radial electric field in L-mode TCV plasmas using Doppler backscattering
  
  • Rienäcker S
  • Hennequin P
  • Vermare L
  • Honoré C
  • Coda S
  • Labit B
  • Vincent Benjamin
  • Wang Y
  • Frassinetti L
  • Panico O
  Plasma Physics and Controlled Fusion, IOP Publishing, 2025, 67 (6), pp.065003. A Doppler backscattering (DBS) diagnostic has recently been installed on the Tokamak à Configuration Variable (TCV) to facilitate the study of edge turbulence and flow shear in a versatile experimental environment. The dual channel V-band DBS system is coupled to TCV’s quasi-optical diagnostic launcher, providing access to the upper low-field side region of the plasma cross-section. Verifications of the DBS measurements are presented. The DBS equilibrium v ⊥ profiles are found to compare favorably with gas puff imaging (GPI) measurements and to the E r inferred from the radial force balance of the carbon impurity. The radial structure of the edge E r × B equilibrium flow and its dependencies are investigated across a representative set of L-mode TCV discharges, by varying density, auxiliary heating and magnetic configuration. (10.1088/1361-6587/add0e0)
  DOI : 10.1088/1361-6587/add0e0
• Phase transition from turbulence to zonal flows in the Hasegawa–Wakatani system
  
  • Guillon P L
  • Gürcan Ö D
  Physics of Plasmas, American Institute of Physics, 2025, 32 (1). The transition between two-dimensional hydrodynamic turbulence and quasi-one-dimensional zonostrophic turbulence is examined in the modified Hasegawa–Wakatani system, which is considered as a minimal model of β-plane-like drift-wave turbulence with an intrinsic instability. Extensive parameter scans were performed across a wide range of values for the adiabaticity parameter C describing the strength of coupling between the two equations. A sharp transition from 2D isotropic turbulence to a quasi-1D system, dominated by zonal flows, is observed using the fraction of the kinetic energy of the zonal modes as the order parameter, at C≈0.1. It is shown that this transition exhibits a hysteresis loop around the transition point, where the adiabaticity parameter plays the role of the control parameter of its nonlinear self-organization. It was also observed that the radial particle flux scales with the adiabaticity parameter following two different power law dependencies in the two regimes. A simple quasi-linear saturation rule which accounts for the presence of zonal flows is proposed, and is shown to agree very well with the observed nonlinear fluxes. Motivated by the phenomenon of quasi-one dimensionalisation of the system at high C, a number of reduction schemes based on a limited number of modes were investigated and the results were compared to direct numerical simulations. In particular, it was observed that a minimal reduced model consisting of 2 poloidal and 2 radial modes was able to replicate the phase transition behavior, while any further reduction failed to capture it. (10.1063/5.0242282)
  DOI : 10.1063/5.0242282
• Milestone in predicting core plasma turbulence: successful multi-channel validation of the gyrokinetic code GENE
  
  • Höfler Klara
  • Görler Tobias
  • Happel Tim
  • Lechte Carsten
  • Molina Pedro
  • Bergmann Michael
  • Bielajew Rachel
  • Conway Garrard
  • David Pierre
  • Denk Severin
  • Fischer Rainer
  • Hennequin Pascale
  • Jenko Frank
  • Mcdermott Rachael
  • White Anne
  • Stroth Ulrich
  Nature Communications, Nature Publishing Group, 2025, 16 (1), pp.2558. On the basis of several recent breakthroughs in fusion research, many activities have been launched around the world to develop fusion power plants on the fastest possible time scale. In this context, high-fidelity simulations of the plasma behavior on large supercomputers provide one of the main pathways to accelerating progress by guiding crucial design decisions. When it comes to determining the energy confinement time of a magnetic confinement fusion device, which is a key quantity of interest, gyrokinetic turbulence simulations are considered the approach of choice – but the question, whether they are really able to reliably predict the plasma behavior is still open. The present study addresses this important issue by means of careful comparisons between state-of-the-art gyrokinetic turbulence simulations with the GENE code and experimental observations in the ASDEX Upgrade tokamak for an unprecedented number of simultaneous plasma observables. (10.1038/s41467-025-56997-2)
  DOI : 10.1038/s41467-025-56997-2
• Nutritional and growth enhancement of alfalfa sprouts through cold plasma and UV seed treatments
  
  • Benabderrahim Mohamed Ali
  • Hannachi Hédia
  • Elfalleh Walid
  • Dufour Thierry
  Italian Journal of Food Science, Codon Publications, 2025, 37 (3), pp.160-173. Employing eco-friendly techniques like cold plasma (CP) and ultraviolet (UV) radiation provides innovative approaches to enhance the sprout quality and productivity of alfalfa. This study explores the effects of CP and UV radiation on the germination, growth, and phytochemical profiles of alfalfa sprouts. CP significantly accelerated germination time, reducing median germination time by 8 hours compared to the control, and enhanced photosynthetic pigments, leading to higher biomass (25.87 mg/sprout fresh weight and 1.45 mg/sprout dry weight). UV treatments, particularly UV-C, increased chlorophyll and total flavonoid content. Overall, CP effectively promotes alfalfa germination and growth, while UV treatments improve specific phytochemicals. (10.15586/ijfs.v37i3.2982)
  DOI : 10.15586/ijfs.v37i3.2982
• The Solar Orbiter merged magnetic field
  
  • Kretzschmar M.
  • Brochot J.-Y.
  • Horbury T. S.
  • Rackovic K.
  • Maksimovic M.
  • Alexandrova O.
  • Bonnin X.
  • Jannet G.
  • O’brien H.
  • Crabtree A.
  • Morris J.
  • Krasnoselskikh Vladimir
  • Dudok de Wit Thierry
  • Le Contel O.
  • Chust T.
  • de Gelis P.-M.
  • da Silva Gonçalves L.
  • Fauchon-Jones E.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2025, 699, pp.A236. Context. In situ studies of the solar wind require precise magnetic field measurements at all frequencies. The Solar Orbiter mission carries two magnetometers to measure the solar wind magnetic field: the fluxgate magnetometer (MAG), which is best suited for frequencies from DC to a few Hertz, and the search coil magnetometer (SCM), which is best suited for frequencies above a few Hertz. Aims: The aim of this paper is to produce a merged magnetic field data product that takes the best of both instruments and provides the community with high quality, easy to use magnetic field data over a wide range of frequencies. Methods: We first compared the two instruments in their overlapping frequency range, then we performed the merging in Fourier space using a weighted function determined by the sensitivity of the two sensors. Results: The two instruments are found to give consistent results in their overlapping frequency range. SCM has a lower gain than MAG by 14% around 1 Hz and MAG is delayed by about 20 ms with respect to SCM, and the merged magnetic field takes care of these discrepancies. It is basically identical to MAG data below 2 Hz and to SCM data above about 15 Hz (with amplitude increased by 14%). We show that the merged magnetic field is suitable to analyse waves and turbulence over a broad frequency range, in particular by confirming that ion cyclotron waves can lower the level of energy at the sub ionic scales. The merged magnetic field is distributed as daily files containing the magnetic field at either 256 or 4096 Hz, and either in the radial-tangential-normal co-ordinates or in the spacecraft reference frame co-ordinates. (10.1051/0004-6361/202554731)
  DOI : 10.1051/0004-6361/202554731