Publications

2011

• Compressible Kelvin-Helmholtz instability in supermagnetosonic regimes
  
  • Palermo F.
  • Faganello M.
  • Califano F.
  • Pegoraro F.
  • Le Contel Olivier
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.4223. We investigate the transition from submagnetosonic to supermagnetosonic regimes in the presence of a sheared flow and density variations typically observed between the solar wind and the Earth's magnetosphere. In particular, we show the possibility of generating quasi-perpendicular magnetosonic shock structures under typical conditions that can be realized at the magnetosphere flanks. Here the Kelvin-Helmholtz instability generates rolled-up, large- scale vortices that propagate along the flanks of the magnetosphere. The shocks are generated by those vortices for which the magnetosonic Mach number turns out to be of the order of unity or larger. (10.1029/2010JA016400)
  DOI : 10.1029/2010JA016400
• Ion acceleration in antiparallel collisionless magnetic reconnection: Kinetic and fluid aspects
  
  • Aunai Nicolas
  • Belmont Gérard
  • Smets Roch
  Comptes Rendus. Physique, Académie des sciences (Paris), 2011, 12, pp.141-150. Not Available (10.1016/j.crhy.2010.11.004)
  DOI : 10.1016/j.crhy.2010.11.004
• Evolution of micro-turbulence characteristics with collisionality at the tokamak core-edge interface
  
  • Vermare Laure
  • Hennequin Pascale
  • Gürcan Özgür D.
  • Honoré Cyrille
  • Berionni Vincent
  • Bourdelle C.
  • Casati A.
  • Clairet F.
  • Garbet X.
  • Giacalone J-C.
  • Sabot R.
  • Tore Supra Team
  , 2011, oral.
• A generalization of the rocket formula and its application to advanced space propulsion systems
  
  • Nasi L.
  • Raimbault Jean-Luc
  Acta Astronautica, Elsevier, 2011, 68 (1-2), pp.34-38. A generalized rocket formula is derived from a first principles approach. The resulting expression of the thrust is applied to advanced space propulsion systems and a possible link between the asymptotic propellant velocity and the velocity at thruster exit is given. An estimation of the thrust modification due to spacecraftplume interactions is also considered. (10.1016/j.actaastro.2010.07.015)
  DOI : 10.1016/j.actaastro.2010.07.015
• Oxidation of NO into NO<SUB>2</SUB> by surface adsorbed O atoms
  
  • Guaitella Olivier
  • Hübner M.
  • Marinov Daniil
  • Guerra V.
  • Pintassilgo C.D.
  • Welzel S.
  • Röpcke J.
  • Rousseau Antoine
  Contributions to Plasma Physics, Wiley-VCH Verlag, 2011, 51 (2-3), pp.176-181. Plasma-surface interactions are increasingly recognised as a key factor in explaining molecule production and conversion processes. In order to scrutinise such effects well-defined surface and gas phase conditions are required. Hence, the inner surface of a Pyrex tube was treated by a capacitively coupled RF plasma at low pressure. The post-plasma oxidation of gas mixtures containing 1 % NO into NO<SUB>2</SUB> has been studied by means of quantum cascade laser absorption spectroscopy in the mid-infrared spectral range. The plasma pre-treatment experiments with oxygen containing precursors suggest O atom adsorption on the Pyrex tube with a surface density of 2.7 x 1014 cm2. A simple kinetic model was developed and shows good agreement with the measured NO and NO<SUB>2</SUB> gas phase concentrations. In the model a fraction of the surface is considered to be covered with chemisorption sites where atoms and molecules can be adsorbed, whereas they can be removed only by recombination (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) (10.1002/ctpp.201000068)
  DOI : 10.1002/ctpp.201000068
• Collective Light Scattering for the Study of Fluctuations in Magnetized Plasmas: The Hall Thruster Case Study
  
  • Tsikata Sedina
  • Honoré Cyrille
  • Grésillon D.
  • Lemoine N.
  Contributions to Plasma Physics, Wiley-VCH Verlag, 2011, 51 (2-3), pp.119-125. Collective light scattering (CLS) has been recently extended to the observation of Hall effect thruster plasmas. A better understanding of the physics of Hall thrusters is key to improving thruster operation and lifetimes. In particular, the origins of thruster phenomena such as anomalous electron transport need to be determined. A high-performance CLS diagnostic has therefore been developed for identifying and measuring electron density fluctuations in the thruster, at millimetric length scales and MHz frequencies. Such modes are believed to play a role in anomalous transport, and experiments so far performed have provided information on their dispersion relations, amplitude and directivity. This work describes the technical aspects of the optical bench and the range of accessible experiments (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) (10.1002/ctpp.201000057)
  DOI : 10.1002/ctpp.201000057
• Electron-cylotron maser radiation from electron holes: upward current region
  
  • Treumann R. A.
  • Baumjohann W.
  • Pottelette R.
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.1885-1904. Electron holes are suggested to be an important source for generation of electron-cyclotron maser radiation. We demonstrate that electron holes generated in a ring-horseshoe distribution in the auroral-kilometric radiation source region have the capacity to emit band-limited radiation. The radiation is calculated in the proper frame of a circular model hole and shown to be strictly perpendicular in this frame. Its bandwidth under auroral conditions is of the order of ~1 kHz, which is a reasonable value. It is also shown that much of the drift of fine structure in the radiation can be interpreted as Doppler shift. Estimates based on data are in good agreement with theory. Growth and absorption rates have been obtained for the emitted radiation. However, the growth rate of a single hole obtained under conservative conditions is small, too small for reproducing the observed fine structure flux. Trapping of radiation inside the hole for the hole's lifetime helps amplifying the radiation additionally but introduces other problems. This entire set of questions is discussed at length and compared to radiation from the global horseshoe distribution. The interior of the hole produces a weak absorption at slightly higher frequency than emission. The absorptivity is roughly two orders of magnitude below the growth rate of the radiation thus being weak even when the emission and absorption bands overlap. Transforming to the stationary observer's frame it is found that the radiation becomes oblique against the magnetic field. For approaching holes the radiated frequencies may even exceed the local electron cyclotron frequency. (10.5194/angeo-29-1885-2011)
  DOI : 10.5194/angeo-29-1885-2011
• Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources
  
  • Kuppel S.
  • Matsushita D.
  • Hatayama A.
  • Bacal M.
  Journal of Applied Physics, American Institute of Physics, 2011, 109 (1), pp.013305. This numerical study focuses on the physical mechanisms involved in the extraction of volume-produced H&#8722; ions from a steady state laboratory negative hydrogen ion source with one opening in the plasma electrode (PE) on which a dc-bias voltage is applied. A weak magnetic field is applied in the source plasma transversely to the extracted beam. The goal is to highlight the combined effects of the weak magnetic field and the PE bias voltage (upon the extraction process of H&#8722; ions and electrons). To do so, we focus on the behavior of electrons and volume-produced negative ions within a two-dimensional model using the particle-in-cell method. No collision processes are taken into account, except for electron diffusion across the magnetic field using a simple random-walk model at each time step of the simulation. The results show first that applying the magnetic field (without PE bias) enhances H&#8722; ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H&#8722; ion current has a maximum when the PE bias is equal to the plasma potential, while the extracted electron current is significantly reduced by applying the PE bias. The underlying mechanism leading to the above results is the gradual opening by the PE bias of the equipotential lines towards the parts of the extraction region facing the PE. The shape of these lines is due originally to the electron trapping by the magnetic field. (10.1063/1.3530454)
  DOI : 10.1063/1.3530454
• Kelvin-Helmholtz waves under southward interplanetary magnetic field
  
  • Hwang K.-J.
  • Kuznetsova M. M.
  • Sahraoui Fouad
  • Goldstein M. L.
  • Lee E.
  • Parks G. K.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.8210. The Kelvin-Helmholtz waves have been observed along the Earth's low-latitude magnetopause and have been suggested to play a certain role in the entry of solar wind plasma into Earth's magnetosphere. In situ observations of the KH waves (KHW) and, in particular, a nonlinear stage of the KH instability, i.e., rolled-up KH vortices (KHVs), have been reported to occur preferentially for northward interplanetary magnetic field (IMF). Using Cluster data, we present the first in situ observation of nonlinearly developed KHW during southward IMF. The analysis reveals that there is a mixture of less-developed and more-developed KHW that shows inconsistent variations in scale size and the magnetic perturbations in the context of the expected evolution of KH structures. A coherence analysis implies that the observed KHW under southward IMF appear to be irregular and intermittent. These irregular and turbulent characteristics are more noticeable than previously reported KHW events that have been detected preferentially during northward IMF. This suggests that under southward IMF KHVs become easily irregular and temporally intermittent, which might explain the preferential in situ detection of KHVs when the IMF is northward. MHD simulation of the present event shows that during southward IMF dynamically active subsolar environments can cause KHV that evolve with considerable intermittency. The MHD simulations appear to reproduce well the qualitative features of the Cluster observations. (10.1029/2011JA016596)
  DOI : 10.1029/2011JA016596
• Three-dimensional spatial structures of solar wind turbulence from 10 000-km to 100-km scales
  
  • Narita Y.
  • Glassmeier K.-H.
  • Goldstein M. L.
  • Motschmann U.
  • Sahraoui Fouad
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.1731-1738. Using the four Cluster spacecraft, we have determined the three-dimensional wave-vector spectra of fluctuating magnetic fields in the solar wind. Three different solar wind intervals of Cluster data are investigated for this purpose, representing three different spatial scales: 10 000 km, 1000 km, and 100 km. The spectra are determined using the wave telescope technique (k-filtering technique) without assuming the validity of Taylor's frozen-in-flow hypothesis nor are any assumptions made as to the symmetry properties of the fluctuations. We find that the spectra are anisotropic on all the three scales and the power is extended primarily in the directions perpendicular to the mean magnetic field, as might be expected of two-dimensional turbulence, however, the analyzed fluctuations are not axisymmetric. The lack of axisymmetry invalidates some earlier techniques using single spacecraft observations that were used to estimate the percentage of magnetic energy residing in quasi-two-dimensional power. However, the dominance of two-dimensional turbulence is consistent with the relatively long mean free paths of cosmic rays in observed in the heliosphere. On the other hand, the spectra also exhibit secondary extended structures oblique from the mean magnetic field direction. We discuss possible origins of anisotropy and asymmetry of solar wind turbulence spectra. (10.5194/angeo-29-1731-2011)
  DOI : 10.5194/angeo-29-1731-2011
• On the dispersion features of whistler waves in almost pure ion plasmas
  
  • Lundin B. V.
  • Krafft C.
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.102114. It is shown that in a multi-ion plasma of moderate density enriched by a large amount of negatively charged ions and/or heavy particulates, the lower cutoff frequencies of the electron whistler and the Z-mode (extraordinary) waves tend to each other, approaching the ion plasma frequency omegapi. The evolution of the dispersion curves omega(k, theta) of both wave modes is studied as a function of the relative electron density, beginning from the case of a moderate density plasma with comparable values of electron gyro- and plasma frequencies and omegapi essentially exceeding the ions' gyrofrequencies. When the fraction of free electrons is very small the transparency frequency domain of the electron whistler mode becomes very narrow, being located in the vicinity of omegapi. If the negatively charged ions have the smallest specific charges among other ion species then, under similar conditions, the so-called crossover effect and the accompanying polarization sense reverse can occur at frequencies essentially greater than the ions' gyrofrequencies. The revealed effects are characteristic of plasmas with excess of electronegative gas molecules or dust particulates highly adhesive to electrons, i.e., almost pure ion plasmas and/or pair-ion plasmas with extra small fractions of free electrons. Moreover, it is found that the vanishingly small electron fraction providing the same value of the electron whistler ion cutoff frequency normalized to the ion plasma frequency is essentially less for pair fullerene C<SUB>60</SUB><SUP> /-</SUP> than for pair hydrogen H /- plasmas. The technique to determine omegapi using the evolution of the whistler wave magnetic field polarization ellipse is also described. (10.1063/1.3650075)
  DOI : 10.1063/1.3650075
• Energy budgets in collisionless magnetic reconnection: Ion heating and bulk acceleration
  
  • Aunai Nicolas
  • Belmont Gérard
  • Smets Roch
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.122901. This paper investigates the energy transfer in the process of collisionless antiparallel magnetic reconnection. Using two-dimensional hybrid simulations, we measure the increase of the bulk and thermal kinetic energies and compare it to the loss of magnetic energy through a contour surrounding the ion decoupling region. It is shown, for both symmetric and asymmetric configurations, that the loss of magnetic energy is not equally partitioned between heating and acceleration. The heating is found to be dominant and the partition ratio depends on the asymptotic parameters, and future investigations will be needed to understand this dependence. (10.1063/1.3664320)
  DOI : 10.1063/1.3664320
• Landau and Non-Landau Linear Damping: Physics of the Dissipation
  
  • Belmont Gérard
  • Chust Thomas
  • Mottez Fabrice
  • Hess S.
  Transport Theory and Statistical Physics, Taylor & Francis, 2011, 40 (6-7), pp.419-424. The linear Landau effect is revisited by the means of numerical simulations and analytical calculations. The existence of non-Landau solutions to the Vlasov-Poisson system is emphasized and the consistency of these solutions with respect to the arguments based on energy is investigated. The present article briefly summarizes the content of two articles already published on the subject and introduces a discussion based on the exchanges that occurred at Marseille during the Vlasovia meeting. (10.1080/00411450.2011.651055)
  DOI : 10.1080/00411450.2011.651055
• Discharge resistance and power dissipation in the self-pulsing regime of micro-hollow cathode discharges
  
  • Lazzaroni Claudia
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2011, 20, pp.055004. Micro-hollow cathode discharges (MHCDs), driven by a dc voltage source, may operate in a self-pulsing regime during which the voltage and the current across the discharge are pulsed with a frequency of several tens of kilohertz. A model for the self-pulsing regime of MHCDs is proposed based on an equivalent electrical circuit of the whole device. The discharge itself is modeled by a non-linear resistance in series with an inductance, and it is placed in parallel with the capacitance of the electrodedielectricelectrode sandwich hosting the discharge micro-hole. The capacitance of the coaxial cable used to feed the device is also included. It is shown that a detailed comparison between theory and experiments allows the discharge non-linear resistance to be accurately determined. When the discharge current is maximum, this resistance is about 2500&#8201;&#937; at 50&#8201;Torr and decreases to about 750&#8201;&#937; at 150&#8201;Torr. The absorbed power is calculated throughout the self-pulsing cycle and may be above 100&#8201;W at the current peak, while the time-averaged power remains a fraction of a Watt. (10.1088/0963-0252/20/5/055004)
  DOI : 10.1088/0963-0252/20/5/055004
• On plasma- and UV-induced VOC oxidation on TiO<SUB>2</SUB> surface pre-treated by plasma exposure monitored by QCLAS
  
  • Marinov Daniil
  • Lopatik D.
  • Guaitella Olivier
  • Hübner M.
  • Rousseau Antoine
  • Roepcke J.
  , 2011.
• Magnetic reconnection in the Jovian tail: X-line evolution and consequent plasma sheet structures
  
  • Kasahara S.
  • Kronberg E. A.
  • Krupp N.
  • Kimura T.
  • Tao C.
  • Badman S. V.
  • Retinò Alessandro
  • Fujimoto M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.11219. Magnetic reconnection in planetary magnetospheres plays important roles in energy and mass transfer in the steady state, and also possibly in transient large-scale disturbances. In this paper we report observations of a reconnection event in the Jovian magnetotail by the Galileo spacecraft on 17 June 1997. In addition to the tailward retreat of a main X-line, signatures of recurrent X-line formations are found by close examination of energetic particle anisotropies. Furthermore, detailed analyses of multi-instrumental data for this period provide various spatiotemporal features in the plasma sheet. A significant density decrease was detected in the central plasma sheet, indicative of the transition to lobe (open field line) reconnection from plasma sheet (closed field line) reconnection. When Galileo vertically swept through the plasma sheet, a velocity layer structure was observed. We also analyze a strong southward magnetic field which is similar to dipolarization fronts observed in the terrestrial magnetotail: the ion flow (450 km s<SUP>-1</SUP>) was observed behind the magnetic front, whose thickness of 10000-20000 km was of the order of ion inertial length. The electron anisotropy in this period suggests an anomalously high-speed electron jet, implying ion-electron decoupling behind the magnetic front. Particle energization was also seen associated with these structures. These observations suggest that X-line evolution and consequent plasma sheet structures are similar to those in the terrestrial magnetosphere, whereas their generality in the Jovian magnetosphere and influence on the magnetospheric/ionospheric dynamics including transient auroral events need to be further investigated with more events. (10.1029/2011JA016892)
  DOI : 10.1029/2011JA016892
• On plasma rotation with toroidal magnetic field ripple and no external momentum input
  
  • Fenzi C.
  • Garbet X.
  • Trier Elisée
  • Hennequin Pascale
  • Bourdelle C.
  • Aniel Thierry
  • Colledani G.
  • Devynck P.
  • Gil C.
  • Gürcan Özgür D.
  • Manenc L.
  • Schneider M.
  • Segui J.-L.
  • Tore Supra Team
  Nuclear Fusion, IOP Publishing, 2011, 51, pp.103038. Ripple-induced thermal loss effect on plasma rotation is investigated in a set of Ohmic L-mode plasmas performed in Tore Supra, and comparisons with neoclassical predictions including ripple are performed. Adjusting the size of the plasma, the ripple amplitude has been varied from 0.5% to 5.5% at the plasma boundary, keeping the edge safety factor constant. The toroidal flow dynamics is understood as being likely dominated by turbulence transport driven processes at low ripple amplitude, while the ripple-induced toroidal friction becomes dominant at high ripple. In the latter case, the velocity tends remarkably towards the neoclassical prediction (counter-current rotation). The radial electric field is not affected by the ripple variation and remains well described by its neoclassical prediction. Finally, the poloidal velocity is of the order of the neoclassical prediction at high ripple amplitude, but significantly departs from it at low ripple. (10.1088/0029-5515/51/10/103038)
  DOI : 10.1088/0029-5515/51/10/103038
• Observation and theoretical modeling of electron scale solar wind turbulence
  
  • Sahraoui Fouad
  • Goldstein M. L.
  • Abdul-Kader K.
  • Belmont Gérard
  • Rezeau Laurence
  • Robert Patrick
  • Canu Patrick
  Comptes Rendus. Physique, Académie des sciences (Paris), 2011, 12 (2), pp.132-140. Turbulence at MagnetoHydroDynamics (MHD) scales in the solar wind has been studied for more than three decades, using data analysis, theoretical and numerical modeling. However, smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to (in the spacecraft reference frame) and found evidence of energy dissipation around the Doppler-shifted electron gyroscale . Before its dissipation, the energy is shown to undergo two cascades: a Kolmogorov-like cascade with a scaling above the proton gyroscale, and a new cascade at the sub-proton and electron gyroscales. Above the spectrum has a steeper power law down to the noise level of the instrument. Solving numerically the linear MaxwellVlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfvén modes (KAW). New analyses of other data sets, where the Cluster separation (of about ) allowed us to explore the sub-proton scales using the k-filtering technique, and to confirm the 2D nature of the turbulence at those scales. (10.1016/j.crhy.2010.11.008)
  DOI : 10.1016/j.crhy.2010.11.008
• Turbulence propagation in heat flux-driven plasmas: implications for temperature profile structure
  
  • Wang Z.H.
  • Diamond P.H.
  • Gürcan Özgür D.
  • Garbet X.
  • Wang X.G.
  Nuclear Fusion, IOP Publishing, 2011, 51, pp.073009. Turbulence propagation and temperature profile evolution are studied in heat flux-driven plasmas. A simple model consisting of coupled non-linear reactiondiffusion equations for both turbulence and heat transport is proposed to elucidate several aspects of apparent non-local profile dynamics. Self-consistent E × B shear feedback on turbulence intensity growth and transport is also included in the model. Temperature profile evolution is studied in the presence of an intensity pulse propagating inwards but also interacting with an outward propagating heat pulse. It is found that as the heat flux Q increases, the intensity pulse speed first grows as √ Q and then decays as 1/Q, while the heat pulse speed finally saturates at the level given by neoclassical transport. Intensity pulse propagation can be effectively saturated at or above a critical heat flux, so that the formation of an internal transport barrier (ITB) can be triggered. This suggests that the ITB location is ultimately determined by both heat flux and edge turbulence conditions, and thus the ITB inhibits both the inward turbulence propagation and the outward turbulent heat transport. As a test of turbulence spreading dynamics, the intensity pulse propagation through gaps in turbulence excitation and its implications for profile response to off-axis heat deposition are also investigated. It is shown that the profile resilience phenomena can be recovered by taking into account intensity pulse propagation. (10.1088/0029-5515/51/7/073009)
  DOI : 10.1088/0029-5515/51/7/073009
• Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics
  
  • Kougblénou S
  • Lointier G
  • Décréau Pierrette
  • Trotignon Jean-Gabriel
  • Rauch Jean-Louis
  • Vallières Xavier
  • Canu Patrick
  • Masson A
  • Pickett J
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.2003–2018. The frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4–80 kHz, has been chosen so as to encompass the electron gyro-frequency, F ce , and the electron plasma frequency, F p , in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plas-masphere where F ce and F p are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency , F lh , in the 4–15 kHz band. This characteristic frequency , placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured F lh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where F ce is increasing and F p decreasing, such that F ce /F p increases from values below unity to values above unity. Measured F lh values thus give access, in turn, to the effective mass, M eff , indicative of plasma ion composition, and to the core plasma-sphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (M eff in the 1.0–1.4 range, N e in the 5 × 10 2 – 10 4 cm −3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, since Correspondence to: S. Kougblénou (sena.kougblenou@cnrs-orleans.fr) late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ∼200 passes per year) and offer multipoint observations previously unavailable in this region. (10.5194/angeo-29-2003-2011)
  DOI : 10.5194/angeo-29-2003-2011
• Physics of Radio-Frequency Plasmas
  
  • Chabert Pascal
  • Braithwaite Nicholas
  , 2011. Low-temperature radio frequency plasmas are essential in various sectors of advanced technology, from micro-engineering to spacecraft propulsion systems and efficient sources of light. The subject lies at the complex interfaces between physics, chemistry and engineering. Focusing mostly on physics, this book will interest graduate students and researchers in applied physics and electrical engineering. The book incorporates a cutting-edge perspective on RF plasmas. It also covers basic plasma physics including transport in bounded plasmas and electrical diagnostics. Its pedagogic style engages readers, helping them to develop physical arguments and mathematical analyses. Worked examples apply the theories covered to realistic scenarios, and over 100 in-text questions let readers put their newly acquired knowledge to use and gain confidence in applying physics to real laboratory situations.
• Gas sensing properties of multiwall carbon nanotubes decorated with rhodium nanoparticles
  
  • Leghrib R
  • Dufour Thierry
  • Demoisson F
  • Claessens N
  • Reniers F
  • Llobet E
  Sensors and Actuators B: Chemical, Elsevier, 2011, B160, pp.974-980. In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O 2). The properties of these hybrid materials towards the room temperature detection of NO 2 , C 2 H 4 , CO, C 6 H 6 and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to avoid response saturation even at low gas/vapor concentrations. These desirable effects are attributed to the presence of oxygen during the CNT plasma treatment since oxygenated vacancies act both as active adsorption sites for gases and as anchoring sites for Rh nanoparticles (the presence of Rh nanoclusters is nearly doubled in Ar:O 2 treated samples as compared to Ar treated samples). The oxygen treatment also makes easier the charge transfer between Rh nanoparticles and carbon nanotubes upon gas adsorption. The method for treating and decorating multiwalled carbon nanotubes used here is simple, fast and scalable for producing gas sensitive nanohybrid materials with uniform and well-controlled properties. (10.1016/j.snb.2011.09.014)
  DOI : 10.1016/j.snb.2011.09.014
• Triple Q : A three channel quantum cascade laser absorption spectrometer for fast multiple species concentration measurements
  
  • Hübner M.
  • Welzel S.
  • Marinov Daniil
  • Guaitella Olivier
  • Glitsch S.
  • Rousseau Antoine
  • Röpcke J.
  Review of Scientific Instruments, American Institute of Physics, 2011, 82, pp.093102. A compact and transportable three channel quantum cascade laser system (TRIPLE Q) based on mid-infrared absorption spectroscopy has been developed for time-resolved plasma diagnostics. The TRIPLE Q spectrometer encompasses three independently controlled quantum cascade lasers (QCLs), which can be used for chemical sensing, particularly for gas phase analysis of plasmas. All three QCLs are operated in the intra-pulse mode with typical pulse lengths of the order of 150 ns. Using a multiplexed detection, a time resolution shorter than 1 &#956;s can be achieved. Hence, the spectrometer is well suited to study kinetic processes of multiple infrared active compounds in reactive plasmas. A special data processing and analysis technique has been established to account for time jitter effects of the infrared emission of the QCLs. The performance of the TRIPLE Q system has been validated in pulsed direct current plasmas containing N2O/air and NO2/air. (10.1063/1.3633952)
  DOI : 10.1063/1.3633952
• Control of Nanocrystalline Silicon Growth Phase and Deposition Rate through Voltage Waveform Tailoring during PECVD
  
  • Johnson E.V.
  • Pouliquen S.
  • Delattre Pierre-Alexandre
  • Booth Jean-Paul
  MRS Online Proceedings Library, Cambridge University Press, 2011, 1339, pp.mrss11-1339-s04-5. The use of Voltage Waveform Tailoring (VWT) that is the use of non-sinusoidal waveforms with a period equivalent to RF frequencies is shown to be effective in modifying the electric field distribution in a parallel plate, capacitively coupled laboratory plasma deposition reactor, and thus in changing the growth mode of silicon thin films from amorphous to nanocrystalline. The use of the VWT technique allows one to decouple the power injected into the plasma from the ion-bombardment energy at the film surface without changing any other deposition parameters, such as pressure or gas mixture. Material results are presented for an H2/SiH4 gas composition. A peaks type waveform increases the ion-bombardment energy at the RF electrode and reduces it at the substrate, resulting in more nanocrystalline growth. The use of a valleys-type waveform has the opposite effect, and results in more amorphous growth. We show the dependence of the process on silane dilution and pressure, including results on changes to the deposition rate when changing the excitation voltage waveform. (10.1557/opl.2011.993)
  DOI : 10.1557/opl.2011.993
• Successive Nanosecond Discharges in Water
  
  • Marinov Ilya
  • Guaitella Olivier
  • Rousseau Antoine
  • Starikovskaia Svetlana
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2011, 39 (11), pp.2672-2673. Successive discharges of alternating polarities in distilled water have been studied. Cathode-initiated discharges develop in two possible configurations: slow and weakly luminescent bushlike mode or fast and luminous treelike mode with well-pronounced branching. Under our experimental conditions, the two modes originate with approximately equal probability. Positive discharge demonstrates only one discharge morphology with two hemispherical weakly luminescent structures. Successive negative pulse results in the formation of one of the negative modes, bushlike or treelike. (10.1109/TPS.2011.2147337)
  DOI : 10.1109/TPS.2011.2147337