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212 results on '"Minea, T."'

3. On the electron energy distribution function in the high power impulse magnetron sputtering discharge

Author

Rudolph, Martin, Revel, A., Lundin, D., Hajihoseini, H., Brenning, N., Raadu, M. A., Anders, A., Minea, T. M., and Gudmundsson, J. T.

Subjects
Physics - Plasma Physics, Physics - Applied Physics
Abstract

We apply the Ionization Region Model (IRM) and the Orsay Boltzmann equation for ELectrons coupled with Ionization and eXcited states kinetics (OBELIX) model to study the electron kinetics of a high power impulse magnetron sputtering (HiPIMS) discharge. In the IRM the bulk (cold) electrons are assumed to exhibit a Maxwellian energy distribution and the secondary (hot) electrons, emitted from the target surface upon ion bombardment, are treated as a high energy tail, while in the OBELIX the electron energy distribution is calculated self-consistently using an isotropic Boltzmann equation. The two models are merged in the sense that the output from the IRM is used as an input for OBELIX. The temporal evolutions of the particle densities are found to agree very well between the two models. Furthermore, a very good agreement is demonstrated between the bi-Maxwellian electron energy distribution assumed by the IRM and the electron energy distribution calculated by the OBELIX model. It can therefore be concluded that assuming a bi-Maxwellian electron energy distribution, constituting a cold bulk electron group and a hot secondary electron group, is a good approximation for modeling the HiPIMS discharge.

Published
2021
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5. R&D around a photoneutralizer-based NBI system (Siphore) in view of a DEMO Tokamak steady state fusion reactor

Author

Simonin, A., Achard, Jocelyn, Achkasov, K., Béchu, S., Baudouin, C., Baulaigue, O., Blondel, C., Boeuf, J. P., Cartry, Gilles, Chaibi, W., Drag, C., de Esch, H. P. L., Fiorucci, D., Fubiani, G., Furno, I., Futtersack, R., Garibaldi, P., Gicquel, A., Grand, C., Guittienne, Ph, Hagelaar, G., Howling, A., Jacquier, R., Kirkpatrick, M. J., Lemoine, D., Lepetit, B., Minea, T., Odic, E., Revel, A., Soliman, B. A., and Teste, P.

Subjects
Physics - Plasma Physics
Abstract

Since the signature of the ITER treaty in 2006, a new research programme targeting the emergence of a new generation of Neutral Beam (NB) system for the future fusion reactor (DEMO Tokamak) has been underway between several laboratories in Europe. The specifications required to operate a NB system on DEMO are very demanding: the system has to provide plasma heating, current drive and plasma control at a very high level of power (up to 150 MW) and energy (1 or 2 MeV), including high performances in term of wall-plug efficiency ($\eta$ > 60%), high availability and reliability. To this aim, a novel NB concept based on the photodetachment of the energetic negative ion beam is under study. The keystone of this new concept is the achievement of a photoneutralizer where a high power photon flux (~3 MW) generated within a Fabry Perot cavity will overlap, cross and partially photodetach the intense negative ion beam accelerated at high energy (1 or 2 MeV). The aspect ratio of the beam-line (source, accelerator, etc.) is specifically designed to maximize the overlap of the photon beam with the ion beam. It is shown that such a photoneutralized based NB system would have the capability to provide several tens of MW of D 0 per beam line with a wall-plug efficiency higher than 60%. A feasibility study of the concept has been launched between different laboratories to address the different physics aspects, i.e., negative ion source, plasma modelling, ion accelerator simulation, photoneutralization and high voltage holding under vacuum. The paper describes the present status of the project and the main achievements of the developments in laboratories.

Published
2019
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7. On the polytropic coefficient of negative ions for modeling the sheath and presheath of electronegative plasmas.

Author

Schiesko, L., Lishev, St., Revel, A., Carbone, E., and Minea, T.

Subjects
ANIONS, LOW temperature plasmas, PLASMA chemistry, CATIONS, PLASMA sheaths
Abstract

The fluid description is widely used for the multi-dimensional modeling of low temperature plasmas with complex chemistries due to their relative low computational cost. It relies, however, on a series of simplifying assumptions and some truncation of the moment equations for describing the non-equilibrium between the electrons, positive ions, negative ions, and the neutrals. In this paper, the classical assumption of isothermal negative ions is revisited for electronegative plasmas and, more particularly, for the fluid modeling of the transition between the plasma and its sheath. To do so, and in contrast to previous studies, the energy balance equation for the negative ions is also computed, and it allows us to derive the polytropic coefficient γ of the negative ions in addition to one of the positive ions. Strong variations in the sheath and presheath of the negative ions temperature and their polytropic coefficient are observed. The polytropic coefficient is shown to be a strongly varying function of space having for consequence that the negative ions are isothermal only in a very narrow extension of the presheath. For the case considered in this paper, both positive and negative ion flows are nearly adiabatic at the sheath-edge and become adiabatic inside the sheath. This paper shows that classical fluid modeling assumptions need to be verified for each system under consideration, most particularly while modeling the transition from plasma to a wall. [ABSTRACT FROM AUTHOR]

Published
2023
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10. Beam Formation Studies on the CERN IS03b H Source

Author

Lettry, J, primary, Vnuchenko, A, additional, Bertolo, S, additional, Mastrostefano, C, additional, O’Neil, M, additional, di Lorenzo, F, additional, Coutron, Y, additional, Steyeart, D, additional, Riffaud, B, additional, Thiboud, J, additional, Guida, R, additional, Kapusniak, K, additional, Charvet, C, additional, Teissandier, B, additional, Moyret, P, additional, Roncarolo, F, additional, Bart Pedersen, S, additional, Duraffourg, M, additional, Vuitton, C, additional, Fantz, U, additional, Mochalskyy, S, additional, Wunderlich, D, additional, Lindqvist, M, additional, den Harder, N, additional, Mimo, A, additional, Briefi, S, additional, Hurlbatt, A, additional, Kalvas, T, additional, Minea, T, additional, and Revel, A, additional

Published
2022
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14. Particle injection methods in 3D-PIC MCC simulations applied to plasma grid biasing.

Author

Lindqvist, M., Wünderlich, D., Mochalskyy, S., den Harder, Niek, Revel, A., Minea, T., and Fantz, U.

Subjects
NEUTRAL beams, ION sources, PLASMA beam injection heating, ANIONS, FUSION reactor divertors, ELECTRONS
Abstract

In negative ion sources for the ITER Neutral Beam Injection system, the co-extraction of electrons is one of the main limiting factors. The current of co-extracted electrons can be decreased by applying a positive bias voltage to the Plasma Grid (PG) with respect to its source walls. Simulations using three-dimensional Particle-in-Cell Monte Carlo Collision (3D-PIC MCC) model are a powerful tool for studying the extraction region of such ion sources. However, the inclusion of both PG and source walls in the simulation domain is difficult due to numerical constraints. This study uses the 3D-PIC MCC code ONIX to explore the effects of particle injection models on plasma characteristics, using a flux injection model to regulate particle influx for a flat transition in potential from the bulk plasma to the simulation domain. Biasing of the PG above floating potential is possible using the flux injection scheme and results in a notable reduction in co-extracted electrons, corroborating with established experimental observations. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Linac4 H− source R&D: Cusp free ICP and magnetron discharge

Author

Lettry, J., primary, Bertolo, S., additional, Fantz, U., additional, Guida, R., additional, Kapusniak, K., additional, Di Lorenzo, F., additional, Machado, C., additional, Mastrostefano, C., additional, Minea, T., additional, O’Neil, M., additional, Neupert, H., additional, Noll, D., additional, Steyaert, D., additional, and Thaus, N., additional

Published
2018
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33. Beam Formation Studies on the CERN IS03b H$^-$ Source

Author

Lettry, J., Vnuchenko, A., Bertolo, S., Mastrostefano, C., O'Neil, M., Lorenzo, F., Coutron, Y., Steyeart, D., Riffaud, B., Thiboud, J., Guida, R., Kapusniak, K., Charvet, C., Teissandier, B., Moyret, P., Roncarolo, F., Bart Pedersen, S., Duraffourg, M., Vuitton, C., Fantz, U., Mochalskyy, S., Wünderlich, D., Lindqvist, M., Harder, N., Mimo, A., Briefi, S., Hurlbatt, A., Kalvas, T., Minea, T., and Revel, A.

Subjects
History, Physics::Accelerator Physics, hiukkaskiihdyttimet, plasmafysiikka, Accelerators and Storage Rings, Computer Science Applications, Education
Abstract

An H- ion source is being operated at the new 160 MeV linear injector (Linac4) of the CERN accelerator complex. The source’s plasma is of the Radio Frequency Inductively Coupled Plasma type (RF-ICP), without magnetic cusp and runs with Cs-loss compensation [1]. Vertical downward oriented filter- and electron dump-dipolar magnetic fields expand over the plasma chamber, beam-formation, beam-extraction and electron dump regions and generate horizontal asymmetry and beam angular deflection partially compensated by mechanical alignment of the front-end. The H- beam is generated via volume and caesiated plasma surface modes, the latter inducing a radial asymmetry characterized by an increased current density close to the plasma electrode surface [2]. Asymmetries affecting the meniscus shape, or its current density have to be simulated via 3D Particle In Cell Monte Carlo (PIC-MC) solvers, such as the Orsay Negative Ion eXtraction code (ONIX) [3]. Validation of these simulations require dedicated measurements. This contribution describes experimental methods newly implemented at CERN’s ion source test stand and initial results for Optical and Beam Emission Spectroscopy (OES, BES), emittance and beam profile measurements. In a later stage, the gathered data sets can be compared to source plasma parameters and extracted beam parameters from PIC-MC simulations, once coupled to the Ion Beam Simulation (IBSimu) [4] beam transport code. The experimental parameter space includes RF-power, density of neutrals, position of the RF coil and extraction field. Beams of H-, D- and protons were produced; examples of measured data are presented in this contribution.

Published
2022

37. Development of a compact bushing for NBI

Author

de Esch, H. P. L., primary, Simonin, A., additional, Grand, C., additional, Lepetit, B., additional, Lemoine, D., additional, Márquez-Mijares, M., additional, Minea, T., additional, Caillault, L., additional, Seznec, B., additional, Jager, T., additional, Odic, E., additional, Kirkpatrick, M. J., additional, Teste, Ph., additional, Dessante, Ph., additional, and Almaksour, K., additional

Published
2017
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43. Target ion and neutral spread in high power impulse magnetron sputtering.

Author

Hajihoseini, H., Brenning, N., Rudolph, M., Raadu, M. A., Lundin, D., Fischer, J., Minea, T. M., and Gudmundsson, J. T.

Subjects
MAGNETRON sputtering, IONS
Abstract

In magnetron sputtering, only a fraction of the sputtered target material leaving the ionization region is directed toward the substrate. This fraction may be different for ions and neutrals of the target material as the neutrals and ions can exhibit a different spread as they travel from the target surface toward the substrate. This difference can be significant in high power impulse magnetron sputtering (HiPIMS) where a substantial fraction of the sputtered material is known to be ionized. Geometrical factors or transport parameters that account for the loss of produced film-forming species to the chamber walls are needed for experimental characterization and modeling of the magnetron sputtering discharge. Here, we experimentally determine transport parameters for ions and neutral atoms in a HiPIMS discharge with a titanium target for various magnet configurations. Transport parameters are determined to a typical substrate, with the same diameter (100 mm) as the cathode target, and located at a distance 70 mm from the target surface. As the magnet configuration and/or the discharge current are changed, the transport parameter for neutral atoms ξ tn remains roughly the same, while transport parameters for ions ξ ti vary greatly. Furthermore, the relative ion-to-neutral transport factors, ξ ti / ξ tn , that describe the relative deposited fractions of target material ions and neutrals onto the substrate, are determined to be in the range from 0.4 to 1.1. [ABSTRACT FROM AUTHOR]

Published
2023
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46. R&D around a photoneutralizer-based NBI system (Siphore) in view of a DEMO Tokamak steady state fusion reactor

Author

Simonin, A., primary, Achard, Jocelyn, additional, Achkasov, K., additional, Bechu, S., additional, Baudouin, C., additional, Baulaigue, O., additional, Blondel, C., additional, Boeuf, J.P., additional, Bresteau, D., additional, Cartry, G., additional, Chaibi, W., additional, Drag, C., additional, de Esch, H.P.L., additional, Fiorucci, D., additional, Fubiani, G., additional, Furno, I., additional, Futtersack, R., additional, Garibaldi, P., additional, Gicquel, A., additional, Grand, C., additional, Guittienne, Ph., additional, Hagelaar, G., additional, Howling, A., additional, Jacquier, R., additional, Kirkpatrick, M.J., additional, Lemoine, D., additional, Lepetit, B., additional, Minea, T., additional, Odic, E., additional, Revel, A., additional, Soliman, B.A., additional, and Teste, P., additional

Published
2015
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