Papers by Jean-Pierre Boeuf
ADI-FDTD modeling of microwave plasma discharges in air towards fully three-dimensional simulations
Computer Physics Communications, 2015
ABSTRACT Plasma formation and propagation during microwave breakdown has been extensively studied... more ABSTRACT Plasma formation and propagation during microwave breakdown has been extensively studied during the last decades. Numerical modeling of the strong coupling between the high frequency electromagnetic waves and the plasma is still a challenging topic due to the different time and space scales involved. In this article, an Alternative Direction Implicit (ADI) formulation of the Finite Difference Time Domain method for solving the Maxwell’s equations coupled with a simplified plasma model via the electric current is being proposed, leading to a significant reduction of the computational cost as the CFL criterion for stability of the FDTD method is being removed. An energy estimate has been used to prove the unconditional stability of the ADI-FDTD leapfrog scheme as well as its coupled formulation. The computational efficiency and accuracy of this approach has been studied in a simplified case. The proposed method is applied and validated in two dimensional microwave breakdown in air while its computational efficiency allows for fully three dimensional simulations, an important step for understanding the complex nature and evolution of a microwave plasma discharge and its possible applicability as an aerodynamic flow control method.
Numerical modelling of plasma for flow control in aerospace applications
ABSTRACT A crucial aspect for supersonic flights is the strong shock wave that forms in front of ... more ABSTRACT A crucial aspect for supersonic flights is the strong shock wave that forms in front of the air vehicle. By modifying the supersonic incoming flow, one can adjust this wave -which is the most contributing factor of the drag coefficient of an aircraft- and have consequently positive effects on the fuel consumption and on the noise produced by the object due to the sonic boom. Lately, plasma associated flow control actuators have been in the center of flow control research and especially of supersonic applications.
Journal of applied physics, 2002
The space and time variations of the light emission in a macroscopic Plasma Display Panel (PDP) d... more The space and time variations of the light emission in a macroscopic Plasma Display Panel (PDP) discharge cell have been studied with an Image-Intensified Charge-Coupled Device (ICCD). The discharge cell is similar to a real PDP cell with a coplanar electrode configuration. The cell dimensions are on the order of 100 times larger than those of a real PDP cell and the operating pressure is about 100 times smaller. Different xenon-neon gas mixtures have been investigated. Optical filters have been used to measure infrared emission from xenon excited states 823.1 nm and 828.0 nm, and visible emission from neon at 640.2 nm.
The use of magnetic fields is quite common in low-pressure, low-temperature, gas-discharge device... more The use of magnetic fields is quite common in low-pressure, low-temperature, gas-discharge devices for industrial applications. However, transport in such devices is still not very well clarified, mainly due to the presence of walls playing a crucial role and to the variety of configurations studied. The latter often obstruct the underlying basic physical phenomena and make the different studies valid only for very specific configurations. This work presents a numerical study of particle transport in low-pressure (0.3 Pa) plasmas across a localized transverse magnetic field (magnetic barrier) by means of the 2D3V particle-in-cell with Monte Carlo collisions method. The problem is treated as generally as possible while trying to reveal the basic physics, using very simplified chemistry and considering a simple rectangular configuration. The conditions chosen for the magnetic field are common to many applications-magnetized electrons and almost unmagnetized ions. Two basic configurations with different magnetic field directions are analyzed in detail: magnetic field perpendicular to the simulation plane and along the simulation plane. An extensive parametric study is carried out in order to obtain the main trends and scaling laws for particle transport with respect to different parameters: plasma density, magnetic barrier size and magnetic field magnitude. The total current of electrons crossing the barrier is found to scale linearly with the plasma density, which extends the validity of the obtained results to a wide range of plasma density values.
New insights in the physics of DBD plasma actuators for flow control
Modeling the effect of the cathode geometry in a DC glow discharge ion source for mass spectrometry
... the disk cathode geo metry. Ions produced near the axis on the anode side of the field revers... more ... the disk cathode geo metry. Ions produced near the axis on the anode side of the field reversal will be drawn toward the anode plane P and the radial electric fieldwill tend to confine them near the axis. Recall that none of the ...
Method to obtain the electric field and the ionization frequency from laser induced fluorescence measurements
Laser induced fluorescence (LIF) diagnostic provides a means to measure an ion velocity distribut... more Laser induced fluorescence (LIF) diagnostic provides a means to measure an ion velocity distribution function (VDF) by Doppler effect with excellent resolution in velocity. This diagnostic has a wide range of applications in low pressure plasma physics and has been used for the past twenty years to study many plasma sources. Most commonly, authors only deduce from the LIF measurements mean ion velocities or accelerating potentials from these mean velocities. However, LIF provides at each measurement position a full VDF which contains much more information than the average velocity. We propose in this paper a new method capable of evaluating the spatial profiles of electric field and ionization frequency. This method consists of establishing a relationship between these quantities and the moments of the measured VDF. We first validate the method by means of numerical simulations and then apply it to two different plasmas: an ICP argon reactor and a Hall effect thruster.
Large gap plasma display cell with auxiliary electrodes: macro-cell experiments and two-dimensional modelling
ABSTRACT
Imaging of a macroscopic plasma display panel cell
In this paper, we present results from the imaging of a macroscopic plasma display discharge cell... more In this paper, we present results from the imaging of a macroscopic plasma display discharge cell obtained with an intensified charge coupled device using infrared optical filters. The macro-cell geometry is identical to that of a plasma display panel (PDP) cell with a coplanar electrode configuration, but the macro-cell dimensions are about 60 times larger than those of a real cell and the operating pressure is 60 times lower. The similarity laws are not expected to be fully valid, but the macro-cell provides a very good insight in the physics of a PDP cell and can help optimizing the discharge efficiency and validate the models
Empirical electron cross-field mobility in a Hall effect thruster
Applied Physics Letters, 2009
Electron transport across the magnetic field in Hall effect thrusters is still an open question. ... more Electron transport across the magnetic field in Hall effect thrusters is still an open question. Models have so far assumed 1/B2 or 1/B scaling laws for the ``anomalous'' electron mobility, adjusted to reproduce the integrated performance parameters of the thruster. We show that models based on such mobility laws predict very different ion velocity distribution functions (IVDF) than measured by
Physics and modelling of microwave streamers at atmospheric pressure
... In this paper, we describe the physics of microwave streamer formation and elongation on the ... more ... In this paper, we describe the physics of microwave streamer formation and elongation on the basis of solutions of the Maxwell equations coupled with a quasineutral model description of the plasma. ... 0021-8979/2011/110(11)/113306/8/$30.00 ...
We have developed a two-dimensional hybrid fluid -particle-in-cell Monte Carlo collisions ͑PIC-MC... more We have developed a two-dimensional hybrid fluid -particle-in-cell Monte Carlo collisions ͑PIC-MCC͒ model to study the plume of a stationary plasma thruster. The model is based on a fluid description of the electrons ͑the electron density follows a Boltzmann distribution͒ and a particle description of the ion and neutral transport. Collisions between heavy species are taken into account with a Monte Carlo method. The electric field is obtained from Poisson's equation or from the quasineutrality assumption. We first show that the results from the PIC-MCC model are close to the results of a more time-consuming direct simulation Monte Carlo approach. We then compare the model predictions of the plume density and ion energy distribution with experimental measurements. Finally, we present a brief discussion on the assumptions of the model and on its ability to give reliable predictions on important issues such as the flux of ions backscattered to the satellite.
Panel performance of RF PDP
We present a study of the principle and operation of a two-stage Hall effect thruster, the SPT-MA... more We present a study of the principle and operation of a two-stage Hall effect thruster, the SPT-MAG, using a two-dimensional quasineutral hybrid model coupled with a Monte Carlo simulation of electron transport. The purpose of the two-stage design is the separation of ion production and acceleration in two separate chambers, the ionization stage and the acceleration stage, with separate control of acceleration voltage and total ionization. The originality of the SPT-MAG lies in the magnetic field configuration in the ionization chamber. Electrons are confined by this magnetic field while ions are supposed to be trapped in the electric potential well supposedly resulting from the magnetic configuration, and guided toward the acceleration stage. The acceleration stage is similar to the channel of a conventional Hall effect thruster. The purpose of this paper is to clarify the physics of the SPT-MAG and to understand the formation of the positive ion trap in the ionization chamber. Using a hybrid model and a Monte Carlo simulation we show that under typical operating conditions most of the ionization in the chamber is due to high energy electrons accelerated in the channel and entering the chamber rather than to electrons accelerated by the voltage applied in the ionization chamber. We also raise the question of the possible role of an additional emissive cathode inside the ionization chamber. The model predicts that an electric potential well guiding the ions to the channel entrance forms in the chamber only if the intermediate electrode inside the chamber is an emissive cathode ͑which is not the case in recent configurations used for this thruster͒.
Model analysis of a double-stage Hall effect thruster with double-peaked magnetic field and intermediate electrode
A hybrid fluid-particle model has been used to study the properties of a double-stage Hall effect... more A hybrid fluid-particle model has been used to study the properties of a double-stage Hall effect thruster where the channel is divided into two regions of large magnetic field separated by a low-field region containing an intermediate, electron-emitting electrode. These two features are aimed at effectively separating the ionization region from the acceleration region in order to extend the thruster
Modeling of double stage Hall effect thruster
Hall effect thrusters (HETs) are ion sources used for satellite station keeping and orbit raising... more Hall effect thrusters (HETs) are ion sources used for satellite station keeping and orbit raising. In Single Stage HETs, the same electric field is responsible for electron heating and ion acceleration. We present a new HET concept where ionization and acceleration are separated in two different stages. This double stage HET allows for a more versatile operation and a separate control of thrust and specific impulse.
Multi-dipolar plasmas are sustained in large-volume chambers by a network of antennas located at ... more Multi-dipolar plasmas are sustained in large-volume chambers by a network of antennas located at the wall. Each antenna consists of a permanent magnet, trapping electrons in an axisymmetric dipole field, and a microwave applicator, heating the trapped electrons by cyclotron resonance (ECR). This paper presents a two-dimensional self-consistent model of a plasma sustained by one such antenna. The microwave fields and power absorption are calculated from the Maxwell equations coupled with a local electron momentum equation by an adaptation of the finite difference time domain method. The plasma is described by fluid equations for magnetized electrons and inertial ions, where quasi-neutrality is imposed through a semi-implicit numerical method based on Poisson's equation, which also yields the sheath potentials. Steady-state model results for argon show that below the critical plasma density (7.4×10 16 m −3 ) the microwave power is absorbed in a narrow region all along the ECR surface around the end of the antenna; beyond this density the main absorption occurs near the plasma edge. Although the electron temperature varies considerably across the magnetic field lines, the plasma potential is nearly uniform all around the antenna and is controlled by the maximum electron temperature.
Key words Stationary plasma thruster, Hall effect thruster, discharge modelling. PACS 52.75.Di, 5... more Key words Stationary plasma thruster, Hall effect thruster, discharge modelling. PACS 52.75.Di, 52.65.-y, 52.65.Ww
We present an overview of models of low pressure, non-thermal gas discharges as commonly used in ... more We present an overview of models of low pressure, non-thermal gas discharges as commonly used in plasma processing. Significant progress has been made in the past decade towards the goal of a self-consistent model of the electrical properties of discharges, whether d.c., r.f. or microwave discharges. These models are based on solutions of the charged particle transport equations coupled with Poisson's equation for the electric field, and provide the space and time distribution of charged particle densities, current densities and electric field or potential. Some of the most sophisticated models also provide the electron and ion velocity distribution functions in the discharge at any point in space or time. It is now possible to describe reasonably accurately the physical properties of a discharge (including the plasma, the electrode regions and the walls) for two-dimensional cylindrical geometries, even for complex electrode configurations involving e.g. a hollow cathode or anode. A survey of the available models is presented here and we illustrate the current state ofthe art by results from one-and two-dimensional models ofd.c., r.f. and transient discharges.
In an end-Hall source, an ion beam is extracted from a magnetized plasma and accelerated by the p... more In an end-Hall source, an ion beam is extracted from a magnetized plasma and accelerated by the plasma electric field without grids. The principle of end-Hall sources is similar to that of Hall effect thrusters (or closed-drift thrusters), but their design is optimized for processing applications (ion beam assisted deposition or substrate cleaning) rather than propulsion. The beam divergence is larger in end-Hall ion sources, and these sources can operate at low ion energies. Although end-Hall sources are commonly used in the surface processing industry, no detailed modeling of these sources is available, and their operation is quite empirical. In this paper, a self-consistent, two-dimensional, quasineutral model of an end-Hall ion source is developed and used in order to improve the understanding of the basic physics of these plasma sources and to quantify the parameters controlling the properties of the extracted ion beam.
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Papers by Jean-Pierre Boeuf