The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device... more The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show
2009 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, 2009
The University of Provence instrumentation department offers a high level of graduate and post gr... more The University of Provence instrumentation department offers a high level of graduate and post graduate engineering programs. Its mission is to form technician experts and engineers with a deep knowledge in their discipline: metrology, instrumentation, tests, Research and Development, automatisms and industrial process control.
A linear magnetic plasma instability is studied using the spatio-temporal evolution of ion veloci... more A linear magnetic plasma instability is studied using the spatio-temporal evolution of ion velocity distribution functions (IVDF) using a time resolved laser induced fluorescence (LIF) diagnostic . Langmuir probes measurements indicate a rotation of the plasma column with spiral arms outside the ionization zone. IVDF inside the ionization zone show, in first approximation, a tangential rotation velocity smaller than the spiral arms rotation velocity in spiral arms, and a radial velocity elsewhere.
Le magnétoplasma produit par le dispositif Mistral présente des régimes instables, réguliers ou t... more Le magnétoplasma produit par le dispositif Mistral présente des régimes instables, réguliers ou tur-bulents. Le transport anormal associé á et etudié en détail cesdernì eres année a la fois par des sonde electriques [1] et par imagerie ultra-rapide. Le contrôle du transport anormal á eté réalisé en appliquant aux régimes faiblement turbulents les techniques classiques de contrôle du chaos temporel, réduisant d'une façon notable le transport anormaì a travers le champ magnétique [2]. Cependant, les modes instables analysés on eté le plus souvent improprement caractérisés comme des ondes de dérive diamagnétiques nonlinéaires [3]. Nous avons montré récemment que, dans la plupart des ca etudiés, ces instabilités se produisen a des fréquences supérieure a la fréquence cyclotronique ionique et que, par conséquent, il ne peut pas s'agir d'ondes de dérive. Le travail présenté ici associe aux mesures par sondes une nouvelle technique optique, la Fluorescence Induite par Laser, qu...
The aim of this talk is to present new data obtained in a multipolar plasma with a laser induced ... more The aim of this talk is to present new data obtained in a multipolar plasma with a laser induced fluorescence (LIF) diagnostic having a sufficiently good spacial resolution to avoid the need of a deconvolution of the results. These new observations have been realized by recording the ion velocity lines in the space phase instead of recording each ion distribution function separately. The electrostatic potential has been determined from the velocity corresponding to the maximum of the ion distribution function recorded at the measured space point. Ours results point out that there is no heating of the ions inside the sheath and then answer no to the question of possible oscillations or instabilities of the sheath.
The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device... more The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show that a train of soliton propagates easier in the device if a weak backward ion flux plasma having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, the closer to the grid the soliton separation occurs. The other contribution of the LIF concerns the bump observed in front of the first soliton edge which was generally identified as precursors ions : in fact this bump results from a collective motion of the argon ions.
2009 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, 2009
The laser-induced fluorescence (LIF) diagnostic is a powerful non-intrusive tool to obtain veloci... more The laser-induced fluorescence (LIF) diagnostic is a powerful non-intrusive tool to obtain velocity distribution function of ions or atoms, with a good time (≈ μs) and space (≈ 0.1 mm) resolution. LIF uses the optical pumping of an ion or atom transition by a laser frequency shifted by Doppler effect: if ωL is the laser frequency, ω0 the ion or atom transition frequency at rest, and V the ion or atom velocity along the laser beam v = 2πc ωL-ω0/ωL. The level of LIF emitted by ions or atoms inside the probed volume is recorded, and by scanning the laser frequency we obtain a fluorescence signal proportional to the number of pumped ions or atoms, i.e. at the resonant velocity and consequently the velocity distribution function along the laser beam for the probed species.
Strong optical pumping of ions can result after a few microseconds of resonance excitation in a l... more Strong optical pumping of ions can result after a few microseconds of resonance excitation in a laser beam. However, both Fokker-Planck diffusion and acceleration due to macroscopic electric fields can remove an ion from resonance by changing the ion velocity on a similar timescale. Therefore, the time dependence of Laser Induced Fluorescence can be influenced, in the first few microseconds, by particle acceleration and velocity-space diffusion. This technique which has been already used to measured Fokker-Planck diffusion, is extended to include the effect of an electric field by mixing the Lagrangian approach, which describe the conditional probability function that an ion initially in (u0,t0) diffuse to (u,t), and the Eulerian one, which describe the state densities temporal evolution. This new non linear optical tagging diagnostic for both electric fields and Fokker-Planck diffusion is verified by application to an electrostatic shock in a multipolar gaz discharge.
Experimental results obtained by laser-induced-fluorescence on metastable ion velocity distributi... more Experimental results obtained by laser-induced-fluorescence on metastable ion velocity distribution functions ͑MIVDF͒ in electrostatic presheaths and sheaths in argon plasmas produced by the thermoionic effect in a multipolar dc discharge are presented. The shape of the measured MIVDF are in qualitative agreement, for the presheath, with Emmert's model and exhibit: ͑1͒ a Maxwellian profile at the center of the device where the potential is zero; ͑2͒ a distribution function's shape made of three distinct parts at the entrance of the presheath. Inside the sheath the recorded MIVDF recovers a Maxwellian profile with a width unexpectedly related to the background neutral pressure. The velocity and potential profiles that can be deduced from the measured MIVDF show a strong influence of the primary electrons emitted by the filaments.
The plasma rotation in the axial magnetic field of the linear machine Mistral ͓A. Escarguel, Eur.... more The plasma rotation in the axial magnetic field of the linear machine Mistral ͓A. Escarguel, Eur. Phys. J. D 56, 209 ͑2010͔͒ is well described by the assumption that the electrons injected from the source exit radially from the central column and are subject to the Lorentz force. Electrons and ions rotate together by ambipolarity. The solution of the momentum equations foresees correctly the observed radial dependence of the ionic radial velocity measured by laser induced fluorescence. The resolution of these equations is also in good agreement with the measured dependence of the rotation frequency on the applied magnetic field and on the background pressure.
The spatial evolution of the 1s 5 metastable argon atom velocity distribution function is recorde... more The spatial evolution of the 1s 5 metastable argon atom velocity distribution function is recorded in the sheath and pre-sheath regions of a metallic wall using laser induced fluorescence (LIF) spectroscopy. Metastable argon atom temperature and fluid velocity are computed from measured data. Owing to the loss of metastable argon atom after a collision with the surface, the atom temperature seemingly decreases and the velocity increases when approaching the wall. These artifacts are carefully examined and explained in terms of changes in the metastable argon atom distribution function. In addition, the atom nonelastic reflection coefficient is computed from the ratio of outward to inward atom flux to the surface. This study indicates less than 1% of metastable atoms survive a collision with the metallic wall. V C 2012 American Institute of Physics.
The frequent situation where a strongly nonlinear rotating structure develops in a linear magneti... more The frequent situation where a strongly nonlinear rotating structure develops in a linear magnetized plasma column is investigated experimentally with emphasis on the ion velocity distribution function (IVDF). Most often, a mode m ¼ 2 appears exhibiting a large density and potential perturbation with angular frequency slightly above the ion cyclotron frequency. For the first time the spatiotemporal evolution of the IVDF is studied using time-resolved laser induced fluorescence to explore the ion's interaction with the nonlinear wave propagating inside the column and at the origin of plasma transport outside the limiter. The ion fluid exhibits an alternance from azimuthal to radial velocity due to the electric field inside the rotating structure. A fluid model also allows us to locally reconstruct the self-consistent electric field evolution which contradicts all existing theories.
Communications in Nonlinear Science and Numerical Simulation, 2003
ABSTRACT Many theoretical and experimental studies of solitons in plasma have been performed [Phy... more ABSTRACT Many theoretical and experimental studies of solitons in plasma have been performed [Phys. Fluids 16 (1973) 1668; Plasma Phys. 25 (1983) 943; IEEE Trans. Plasma Phys. PS 10 (1982) 180; Plasma Phys. 5 (1998) 4144] and most of the properties such as the relation between the amplitude, the velocity and the width, for soliton or soliton-dust interaction, have been obtained. The agreement between experiment and theoretical model is not always good [Phil. Mag. Ser. 39 (1895) 422; Phys. Rev. Lett. 17 (1966) 996; Phys. Rev. E 51 (1995) 4796]. The experimental observations typically involve Langmuir probes. However, the ion acoustic soliton propagation can be observed by laser induced fluorescence (LIF) in double plasma device. This direct observation of ion perturbation with LIF points out the importance of the optical pumping effect [Rev. Sci. Instrum. 72 (2001) 4372] in the measurement of fast velocity propagation of ion phenomena like solitons are. With the LIF we discovered that a train of soliton propagates easier in the device if a weak backward ion flux plasma, having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, as close to the grid the solitons separation occurs; the precursors ions is in fact a collective phenomenon.
A cylindrical column of magnetized plasma is produced by means of the hot cathode laboratory devi... more A cylindrical column of magnetized plasma is produced by means of the hot cathode laboratory device MISTRAL using various gases (Neon, Argon, Krypton). In usual experimental conditions, strongly nonlinear low frequency instabilities in the ion cyclotron range are recorded. A transition towards ion cyclotron turbulence appears to be triggered by a threshold value of the radial electric field. In order to investigate the characteristics of the instabilities and the phenomena responsible for the destabilization of the plasma column, detailed measurements are performed using various diagnostics (probe arrays, ultra-fast and intensified cameras, Laser Induced Fluorescence, spectroscopy, microwave resonance). The results are compared with both a theoretical model of the ion cyclotron instability and Particle in Cell simulation of the instability.
The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device... more The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show
2009 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, 2009
The University of Provence instrumentation department offers a high level of graduate and post gr... more The University of Provence instrumentation department offers a high level of graduate and post graduate engineering programs. Its mission is to form technician experts and engineers with a deep knowledge in their discipline: metrology, instrumentation, tests, Research and Development, automatisms and industrial process control.
A linear magnetic plasma instability is studied using the spatio-temporal evolution of ion veloci... more A linear magnetic plasma instability is studied using the spatio-temporal evolution of ion velocity distribution functions (IVDF) using a time resolved laser induced fluorescence (LIF) diagnostic . Langmuir probes measurements indicate a rotation of the plasma column with spiral arms outside the ionization zone. IVDF inside the ionization zone show, in first approximation, a tangential rotation velocity smaller than the spiral arms rotation velocity in spiral arms, and a radial velocity elsewhere.
Le magnétoplasma produit par le dispositif Mistral présente des régimes instables, réguliers ou t... more Le magnétoplasma produit par le dispositif Mistral présente des régimes instables, réguliers ou tur-bulents. Le transport anormal associé á et etudié en détail cesdernì eres année a la fois par des sonde electriques [1] et par imagerie ultra-rapide. Le contrôle du transport anormal á eté réalisé en appliquant aux régimes faiblement turbulents les techniques classiques de contrôle du chaos temporel, réduisant d'une façon notable le transport anormaì a travers le champ magnétique [2]. Cependant, les modes instables analysés on eté le plus souvent improprement caractérisés comme des ondes de dérive diamagnétiques nonlinéaires [3]. Nous avons montré récemment que, dans la plupart des ca etudiés, ces instabilités se produisen a des fréquences supérieure a la fréquence cyclotronique ionique et que, par conséquent, il ne peut pas s'agir d'ondes de dérive. Le travail présenté ici associe aux mesures par sondes une nouvelle technique optique, la Fluorescence Induite par Laser, qu...
The aim of this talk is to present new data obtained in a multipolar plasma with a laser induced ... more The aim of this talk is to present new data obtained in a multipolar plasma with a laser induced fluorescence (LIF) diagnostic having a sufficiently good spacial resolution to avoid the need of a deconvolution of the results. These new observations have been realized by recording the ion velocity lines in the space phase instead of recording each ion distribution function separately. The electrostatic potential has been determined from the velocity corresponding to the maximum of the ion distribution function recorded at the measured space point. Ours results point out that there is no heating of the ions inside the sheath and then answer no to the question of possible oscillations or instabilities of the sheath.
The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device... more The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show that a train of soliton propagates easier in the device if a weak backward ion flux plasma having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, the closer to the grid the soliton separation occurs. The other contribution of the LIF concerns the bump observed in front of the first soliton edge which was generally identified as precursors ions : in fact this bump results from a collective motion of the argon ions.
2009 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, 2009
The laser-induced fluorescence (LIF) diagnostic is a powerful non-intrusive tool to obtain veloci... more The laser-induced fluorescence (LIF) diagnostic is a powerful non-intrusive tool to obtain velocity distribution function of ions or atoms, with a good time (≈ μs) and space (≈ 0.1 mm) resolution. LIF uses the optical pumping of an ion or atom transition by a laser frequency shifted by Doppler effect: if ωL is the laser frequency, ω0 the ion or atom transition frequency at rest, and V the ion or atom velocity along the laser beam v = 2πc ωL-ω0/ωL. The level of LIF emitted by ions or atoms inside the probed volume is recorded, and by scanning the laser frequency we obtain a fluorescence signal proportional to the number of pumped ions or atoms, i.e. at the resonant velocity and consequently the velocity distribution function along the laser beam for the probed species.
Strong optical pumping of ions can result after a few microseconds of resonance excitation in a l... more Strong optical pumping of ions can result after a few microseconds of resonance excitation in a laser beam. However, both Fokker-Planck diffusion and acceleration due to macroscopic electric fields can remove an ion from resonance by changing the ion velocity on a similar timescale. Therefore, the time dependence of Laser Induced Fluorescence can be influenced, in the first few microseconds, by particle acceleration and velocity-space diffusion. This technique which has been already used to measured Fokker-Planck diffusion, is extended to include the effect of an electric field by mixing the Lagrangian approach, which describe the conditional probability function that an ion initially in (u0,t0) diffuse to (u,t), and the Eulerian one, which describe the state densities temporal evolution. This new non linear optical tagging diagnostic for both electric fields and Fokker-Planck diffusion is verified by application to an electrostatic shock in a multipolar gaz discharge.
Experimental results obtained by laser-induced-fluorescence on metastable ion velocity distributi... more Experimental results obtained by laser-induced-fluorescence on metastable ion velocity distribution functions ͑MIVDF͒ in electrostatic presheaths and sheaths in argon plasmas produced by the thermoionic effect in a multipolar dc discharge are presented. The shape of the measured MIVDF are in qualitative agreement, for the presheath, with Emmert's model and exhibit: ͑1͒ a Maxwellian profile at the center of the device where the potential is zero; ͑2͒ a distribution function's shape made of three distinct parts at the entrance of the presheath. Inside the sheath the recorded MIVDF recovers a Maxwellian profile with a width unexpectedly related to the background neutral pressure. The velocity and potential profiles that can be deduced from the measured MIVDF show a strong influence of the primary electrons emitted by the filaments.
The plasma rotation in the axial magnetic field of the linear machine Mistral ͓A. Escarguel, Eur.... more The plasma rotation in the axial magnetic field of the linear machine Mistral ͓A. Escarguel, Eur. Phys. J. D 56, 209 ͑2010͔͒ is well described by the assumption that the electrons injected from the source exit radially from the central column and are subject to the Lorentz force. Electrons and ions rotate together by ambipolarity. The solution of the momentum equations foresees correctly the observed radial dependence of the ionic radial velocity measured by laser induced fluorescence. The resolution of these equations is also in good agreement with the measured dependence of the rotation frequency on the applied magnetic field and on the background pressure.
The spatial evolution of the 1s 5 metastable argon atom velocity distribution function is recorde... more The spatial evolution of the 1s 5 metastable argon atom velocity distribution function is recorded in the sheath and pre-sheath regions of a metallic wall using laser induced fluorescence (LIF) spectroscopy. Metastable argon atom temperature and fluid velocity are computed from measured data. Owing to the loss of metastable argon atom after a collision with the surface, the atom temperature seemingly decreases and the velocity increases when approaching the wall. These artifacts are carefully examined and explained in terms of changes in the metastable argon atom distribution function. In addition, the atom nonelastic reflection coefficient is computed from the ratio of outward to inward atom flux to the surface. This study indicates less than 1% of metastable atoms survive a collision with the metallic wall. V C 2012 American Institute of Physics.
The frequent situation where a strongly nonlinear rotating structure develops in a linear magneti... more The frequent situation where a strongly nonlinear rotating structure develops in a linear magnetized plasma column is investigated experimentally with emphasis on the ion velocity distribution function (IVDF). Most often, a mode m ¼ 2 appears exhibiting a large density and potential perturbation with angular frequency slightly above the ion cyclotron frequency. For the first time the spatiotemporal evolution of the IVDF is studied using time-resolved laser induced fluorescence to explore the ion's interaction with the nonlinear wave propagating inside the column and at the origin of plasma transport outside the limiter. The ion fluid exhibits an alternance from azimuthal to radial velocity due to the electric field inside the rotating structure. A fluid model also allows us to locally reconstruct the self-consistent electric field evolution which contradicts all existing theories.
Communications in Nonlinear Science and Numerical Simulation, 2003
ABSTRACT Many theoretical and experimental studies of solitons in plasma have been performed [Phy... more ABSTRACT Many theoretical and experimental studies of solitons in plasma have been performed [Phys. Fluids 16 (1973) 1668; Plasma Phys. 25 (1983) 943; IEEE Trans. Plasma Phys. PS 10 (1982) 180; Plasma Phys. 5 (1998) 4144] and most of the properties such as the relation between the amplitude, the velocity and the width, for soliton or soliton-dust interaction, have been obtained. The agreement between experiment and theoretical model is not always good [Phil. Mag. Ser. 39 (1895) 422; Phys. Rev. Lett. 17 (1966) 996; Phys. Rev. E 51 (1995) 4796]. The experimental observations typically involve Langmuir probes. However, the ion acoustic soliton propagation can be observed by laser induced fluorescence (LIF) in double plasma device. This direct observation of ion perturbation with LIF points out the importance of the optical pumping effect [Rev. Sci. Instrum. 72 (2001) 4372] in the measurement of fast velocity propagation of ion phenomena like solitons are. With the LIF we discovered that a train of soliton propagates easier in the device if a weak backward ion flux plasma, having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, as close to the grid the solitons separation occurs; the precursors ions is in fact a collective phenomenon.
A cylindrical column of magnetized plasma is produced by means of the hot cathode laboratory devi... more A cylindrical column of magnetized plasma is produced by means of the hot cathode laboratory device MISTRAL using various gases (Neon, Argon, Krypton). In usual experimental conditions, strongly nonlinear low frequency instabilities in the ion cyclotron range are recorded. A transition towards ion cyclotron turbulence appears to be triggered by a threshold value of the radial electric field. In order to investigate the characteristics of the instabilities and the phenomena responsible for the destabilization of the plasma column, detailed measurements are performed using various diagnostics (probe arrays, ultra-fast and intensified cameras, Laser Induced Fluorescence, spectroscopy, microwave resonance). The results are compared with both a theoretical model of the ion cyclotron instability and Particle in Cell simulation of the instability.
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