Obliquely propagating large amplitude solitary waves in charge neutral plasmas
Directory of Open Access Journals (Sweden)
F. Verheest
2007-01-01
Full Text Available This paper deals in a consistent way with the implications, for the existence of large amplitude stationary structures in general plasmas, of assuming strict charge neutrality between electrons and ions. With the limit of pair plasmas in mind, electron inertia is retained. Combining in a fluid dynamic treatment the conservation of mass, momentum and energy with strict charge neutrality has indicated that nonlinear solitary waves (as e.g. oscillitons cannot exist in electron-ion plasmas, at no angle of propagation with respect to the static magnetic field. Specifically for oblique propagation, the proof has turned out to be more involved than for parallel or perpendicular modes. The only exception is pair plasmas that are able to support large charge neutral solitons, owing to the high degree of symmetry naturally inherent in such plasmas. The nonexistence, in particular, of oscillitons is attributed to the breakdown of the plasma approximation in dealing with Poisson's law, rather than to relativistic effects. It is hoped that future space observations will allow to discriminate between oscillitons and large wave packets, by focusing on the time variability (or not of the phase, since the amplitude or envelope graphs look very similar.
Obliquely Propagating Non-Monotonic Double Layer in a Hot Magnetized Plasma
International Nuclear Information System (INIS)
Kim, T.H.; Kim, S.S.; Hwang, J.H.; Kim, H.Y.
2005-01-01
Obliquely propagating non-monotonic double layer is investigated in a hot magnetized plasma, which consists of a positively charged hot ion fluid and trapped, as well as free electrons. A model equation (modified Korteweg-de Vries equation) is derived by the usual reductive perturbation method from a set of basic hydrodynamic equations. A time stationary obliquely propagating non-monotonic double layer solution is obtained in a hot magnetized-plasma. This solution is an analytic extension of the monotonic double layer and the solitary hole. The effects of obliqueness, external magnetic field and ion temperature on the properties of the non-monotonic double layer are discussed
Oblique Propagation of Fast Surface Waves in a Low-Beta Hall-Magnetohydrodynamics Plasma Slab
International Nuclear Information System (INIS)
Zhelyazkov, I.; Mann, G.
1999-01-01
The oblique propagation of fast sausage and kink magnetohydrodynamics (MHD) surface waves in an ideal magnetized plasma slab in the low-beta plasma limit is studied considering the Hall term in the generalized Ohm's law. It is found that the combined action of the Hall effect and oblique wave propagation makes possible the existence of multivalued solutions to the wave dispersion relations - some of them corresponding to positive values of the transfer wave number, k y , undergo a 'propagation stop' at specific (numerically found) full wave numbers. It is also shown that with growing wave number the waves change their nature - from bulk modes to pseudosurface or pure surface waves. (author)
International Nuclear Information System (INIS)
Ohnuma, T.; Watanabe, T.; Sanuki, H.
1981-08-01
Propagation characteristics and refractive effects of an oblique electron thermal mode without boundary effects below the electron plasma frequency are studied experimentally and theoretically in an inhomogeneous magnetized plasma. The behavior of this mode observed experimentally was confirmed by the theoretical analysis based on a new type of ray theory. (author)
Obliquely propagating cnoidal waves in a magnetized dusty plasma with variable dust charge
International Nuclear Information System (INIS)
Yadav, L. L.; Sayal, V. K.
2009-01-01
We have studied obliquely propagating dust-acoustic nonlinear periodic waves, namely, dust-acoustic cnoidal waves, in a magnetized dusty plasma consisting of electrons, ions, and dust grains with variable dust charge. Using reductive perturbation method and appropriate boundary conditions for nonlinear periodic waves, we have derived Korteweg-de Vries (KdV) equation for the plasma. It is found that the contribution to the dispersion due to the deviation from plasma approximation is dominant for small angles of obliqueness, while for large angles of obliqueness, the dispersion due to magnetic force becomes important. The cnoidal wave solution of the KdV equation is obtained. It is found that the frequency of the cnoidal wave depends on its amplitude. The effects of the magnetic field, the angle of obliqueness, the density of electrons, the dust-charge variation and the ion-temperature on the characteristics of the dust-acoustic cnoidal wave are also discussed. It is found that in the limiting case the cnoidal wave solution reduces to dust-acoustic soliton solution.
International Nuclear Information System (INIS)
Kadijani, M Nouri; Abbasi, H; Pajouh, H Hakimi
2011-01-01
The effect of superthermal electrons, modeled by a Lorentzian velocity distribution function, on the oblique propagation characteristics of linear and nonlinear ion-acoustic waves in an electron-ion plasma in the presence of a uniform external magnetic field is investigated. First, the linear dispersion relations of the fast and slow modes are obtained. It is shown that the superthermal electrons make both modes propagate with smaller phase velocities. Then, the Korteweg-de Vries equation describing the propagation of nonlinear slow and fast ion-acoustic waves is derived. It is shown that the presence of superthermal electrons has a significant influence on the nature of magnetized ion-acoustic solitons. That is, for a larger population of the superthermal electrons, the soliton velocity of both modes in the laboratory frame significantly decreases and the soliton are slimmer, and on approaching the Maxwellian limit, the width becomes maximum.
Ion acoustic solitary waves in a dusty plasma obliquely propagating to an external magnetic field
International Nuclear Information System (INIS)
Choi, Cheong Rim; Ryu, Chang-Mo; Lee, Nam C.; Lee, D.-Y.
2005-01-01
The nonlinear ion acoustic solitary wave in a magnetized dusty plasma, obliquely propagating to the embedding external magnetic field, is revisited. It is found that when the charge density of dust particles is high, the Sagdeev potential needs to be expanded up to δn 4 near n=1. In this case, it is shown that there could exist rarefactive ion acoustic solitary waves as well as the kink-type double layer solutions, in addition to the conventional hump-type ones found in the δn 3 expansion. The amplitude variations of ion acoustic solitary waves in a magnetized dusty plasma are also examined with respect to the change of the dust charge density and the wave directional angle
Adnan, Muhammad; Qamar, Anisa; Mahmood, Shahzad; Kourakis, Ioannis
2017-03-01
The dynamical characteristics of large amplitude ion-acoustic waves are investigated in a magnetized plasma comprising ions presenting space asymmetry in the equation of state and non-Maxwellian electrons. The anisotropic ion pressure is defined using the double adiabatic Chew-Golberger-Low theory. An excess in the superthermal component of the electron population is assumed, in agreement with long-tailed (energetic electron) distribution observations in space plasmas; this is modeled via a kappa-type distribution function. Large electrostatic excitations are assumed to propagate in a direction oblique to the external magnetic field. In the linear (small amplitude) regime, two electrostatic modes are shown to exist. The properties of arbitrary amplitude (nonlinear) obliquely propagating ion-acoustic solitary excitations are thus investigated via a pseudomechanical energy balance analogy, by adopting a Sagdeev potential approach. The combined effect of the ion pressure anisotropy and excess superthermal electrons is shown to alter the parameter region where solitary waves can exist. An excess in the suprathermal particles is thus shown to be associated with solitary waves, which are narrower, faster, and of larger amplitude. Ion pressure anisotropy, on the other hand, affects the amplitude of the solitary waves, which become weaker (in strength), wider (in spatial extension), and thus slower in comparison with the cold ion case.
Obliquely propagating dust-density waves
International Nuclear Information System (INIS)
Piel, A.; Arp, O.; Klindworth, M.; Melzer, A.
2008-01-01
Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and another mode propagating obliquely at the boundary between the dusty plasma and the space charge sheath. The dominance of oblique modes can be described in the frame of a fluid model. It is shown that the results fom the fluid model agree remarkably well with a kinetic electrostatic model of Rosenberg [J. Vac. Sci. Technol. A 14, 631 (1996)]. In the experiment, the instability is quenched by increasing the gas pressure or decreasing the dust density. The critical pressure and dust density are well described by the models
Sarker, M.; Hossen, M. R.; Shah, M. G.; Hosen, B.; Mamun, A. A.
2018-06-01
A theoretical investigation is carried out to understand the basic features of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an external magnetic field in an electron-positron-ion plasma that consists of cold magnetized positively charged heavy ion fluids and superthermal distributed electrons and positrons. In the nonlinear regime, the Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations describing the propagation of HIA waves are derived. The latter admits a solitary wave solution with both positive and negative potentials (for K-dV equation) and only positive potential (for mK-dV equation) in the weak amplitude limit. It is observed that the effects of external magnetic field (obliqueness), superthermal electrons and positrons, different plasma species concentration, heavy ion dynamics, and temperature ratio significantly modify the basic features of HIA solitary waves. The application of the results in a magnetized EPI plasma, which occurs in many astrophysical objects (e.g. pulsars, cluster explosions, and active galactic nuclei) is briefly discussed.
International Nuclear Information System (INIS)
Mamun, A.A.; Hassan, M.H.A.
1999-05-01
Effects of dust grain charge fluctuation, obliqueness and external magnetic field on finite amplitude dust-acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge fluctuating dust grains, have been investigated by the reductive perturbation method. It has been shown that such a magnetized dusty plasma system may support dust-acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self-consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust-acoustic solitary potential significantly. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)
Ion stochastic heating by obliquely propagating magnetosonic waves
International Nuclear Information System (INIS)
Gao Xinliang; Lu Quanming; Wu Mingyu; Wang Shui
2012-01-01
The ion motions in obliquely propagating Alfven waves with sufficiently large amplitudes have already been studied by Chen et al.[Phys. Plasmas 8, 4713 (2001)], and it was found that the ion motions are stochastic when the wave frequency is at a fraction of the ion gyro-frequency. In this paper, with test particle simulations, we investigate the ion motions in obliquely propagating magnetosonic waves and find that the ion motions also become stochastic when the amplitude of the magnetosonic waves is sufficiently large due to the resonance at sub-cyclotron frequencies. Similar to the Alfven wave, the increase of the propagating angle, wave frequency, and the number of the wave modes can lower the stochastic threshold of the ion motions. However, because the magnetosonic waves become more and more compressive with the increase of the propagating angle, the decrease of the stochastic threshold with the increase of the propagating angle is more obvious in the magnetosonic waves than that in the Alfven waves.
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Remya, B.; Reddy, R. V.; Lakhina, G. S. [Indian Institute of Geomagnetism, Kalamboli Highway, New Panvel, Navi Mumbai, Maharashtra (India); Tsurutani, B. T.; Falkowski, B. J. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Echer, E. [Instituto Nacional de Pesquisas Espaciais (INPE), Avenida Astronautas, 1758, P.O. Box 515, Sao Jose dos Campos, SP (Brazil); Glassmeier, K.-H., E-mail: remyaphysics@gmail.com [Institute for Geophysics and Extraterrestrial Physics (IGEP), Mendelssohnstr.3, D-38106, Braunschweig (Germany)
2014-09-20
During 1999 August 18, both Cassini and WIND were in the Earth's magnetosheath and detected transverse electromagnetic waves instead of the more typical mirror-mode emissions. The Cassini wave amplitudes were as large as ∼14 nT (peak to peak) in a ∼55 nT ambient magnetic field B {sub 0}. A new method of analysis is applied to study these waves. The general wave characteristics found were as follows. They were left-hand polarized and had frequencies in the spacecraft frame (f {sub scf}) below the proton cyclotron frequency (f{sub p} ). Waves that were either right-hand polarized or had f {sub scf} > f{sub p} are shown to be consistent with Doppler-shifted left-hand waves with frequencies in the plasma frame f{sub pf} < f{sub p} . Thus, almost all waves studied are consistent with their being electromagnetic proton cyclotron waves. Most of the waves (∼55%) were found to be propagating along B {sub 0} (θ{sub kB{sub 0}}<30{sup ∘}), as expected from theory. However, a significant fraction of the waves were found to be propagating oblique to B {sub 0}. These waves were also circularly polarized. This feature and the compressive ([B {sub max} – B {sub min}]/B {sub max}, where B {sub max} and B {sub min} are the maximum and minimum field magnitudes) nature (ranging from 0.27 to 1.0) of the waves are noted but not well understood at this time. The proton cyclotron waves were shown to be quasi-coherent, theoretically allowing for rapid pitch-angle transport of resonant protons. Because Cassini traversed the entire subsolar magnetosheath and WIND was in the dusk-side flank of the magnetosheath, it is surmised that the entire region was filled with these waves. In agreement with past theory, it was the exceptionally low plasma β (0.35) that led to the dominance of the proton cyclotron wave generation during this interval. A high-speed solar wind stream ((V{sub sw} ) = 598 km s{sup –1}) was the source of this low-β plasma.
International Nuclear Information System (INIS)
Esfandyari-Kalejahi, A.; Akbari-Moghanjoughi, M.; Mehdipoor, M.
2009-01-01
Ion-acoustic (IA) solitary waves are investigated in a magnetized three-component plasma consisting of cold ions, isothermal hot electrons, and positrons. The basic set of fluid equations is reduced to the Korteweg de Vries equation using the standard reductive perturbation (multiple-scale) technique. Theoretical and numerical analyses confirm significant effects of the presence of positrons and the dependence of the electron to positron temperature ratio on the amplitude and the width of IA solitary waves. It is shown that the rarefactive and compressive IA solitary excitations can propagate when the propagation angle θ satisfies 0≤θ 0 , whereas their width depends strictly on B 0 . The numerical analysis has been done based on the typical numerical data from a pulsar magnetosphere.
Wafer scale oblique angle plasma etching
Burckel, David Bruce; Jarecki, Jr., Robert L.; Finnegan, Patrick Sean
2017-05-23
Wafer scale oblique angle etching of a semiconductor substrate is performed in a conventional plasma etch chamber by using a fixture that supports a multiple number of separate Faraday cages. Each cage is formed to include an angled grid surface and is positioned such that it will be positioned over a separate one of the die locations on the wafer surface when the fixture is placed over the wafer. The presence of the Faraday cages influences the local electric field surrounding each wafer die, re-shaping the local field to be disposed in alignment with the angled grid surface. The re-shaped plasma causes the reactive ions to follow a linear trajectory through the plasma sheath and angled grid surface, ultimately impinging the wafer surface at an angle. The selected geometry of the Faraday cage angled grid surface thus determines the angle at with the reactive ions will impinge the wafer.
An Obliquely Propagating Electromagnetic Drift Instability in the Lower Hybrid Frequency Range
International Nuclear Information System (INIS)
Hantao Ji; Russell Kulsrud; William Fox; Masaaki Yamada
2005-01-01
By employing a local two-fluid theory, we investigate an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field current or relative drifts between electrons and ions. The theory self-consistently takes into account local cross-field current and accompanying pressure gradients. It is found that the instability is caused by reactive coupling between the backward propagating whistler (fast) waves in the moving electron frame, and the forward propagating sound (slow) waves in the ion frame when the relative drifts are large. The unstable waves we consider propagate obliquely to the unperturbed magnetic field and have mixed polarization with significant electromagnetic components. A physical picture of the instability emerges in the limit of large wave number characteristic of the local approximation. The primary positive feedback mechanism is based on reinforcement of initial electron density perturbations by compression of electron fluid via induced Lorentz force. The resultant waves are qualitatively consistent with the measured electromagnetic fluctuations in reconnecting current sheet in a laboratory plasma
Pandey, R. S.; Singh, Vikrant; Rani, Anju; Varughese, George; Singh, K. M.
2018-05-01
In the present paper Oblique propagating electromagnetic ion-cyclotron wave has been analyzed for anisotropic multi ion plasma (H+, He+, O+ ions) in earth magnetosphere for the Dione shell of L=7 i.e., the outer radiation belt of the magnetosphere for Loss-cone distribution function with a spectral index j in the presence of A.C. electric field. Detail for particle trajectories and dispersion relation has been derived by using the method of characteristic solution on the basis of wave particle interaction and transformation of energy. Results for the growth rate have been calculated numerically for various parameters and have been compared for different ions present in magnetosphere. It has been found that for studying the wave over wider spectrum, anisotropy for different values of j should be taken. The effect of frequency of A.C. electric field and angle which propagation vector make with magnetic field, on growth rate has been explained.
MAVEN Observation of an Obliquely Propagating Low-Frequency Wave Upstream of Mars
Ruhunusiri, Suranga; Halekas, J. S.; Connerney, J. E. P.; Espley, J. R.; McFadden, J. P.; Mazelle, C.; Brain, D.; Collinson, G.; Harada, Y.; Larson, D. E.;
2016-01-01
We report Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observations of a large amplitude low-frequency plasma wave that propagated oblique to the ambient magnetic field upstream of Mars along with a non-solar-wind plasma component that had a flow velocity perpendicular to the magnetic field. We consider nine possibilities for this wave that include various combinations of its propagation direction, polarization in the solar wind frame, and ion source responsible for its generation. Using the observed wave parameters and the measured plasma parameters as constraints, we uniquely identify the wave by systematically discarding these possibilities. We determine that the wave is a right-hand polarized wave that propagated upstream in the solar wind frame. We find two possibilities for the ion source that can be responsible for this wave generation. They are either newly born pickup protons or reflected solar wind protons from the bow shock.We determine that the observed non-solar-wind component is not responsible for the wave generation, and it is likely that the non-solar-wind component was merely perturbed by the passage of the wave.
Effect of kappa distribution on the damping rate of the obliquely propagating magnetosonic mode
Imran, Ali KHAN; G, MURTAZA
2018-03-01
Data from spacecrafts suggest that space plasma has an abundance of suprathermal particles which are controlled by the spectral index κ when modeled on kappa particle velocity distribution. In this paper, considering homogeneous plasma, the effect of integer values of κ on the damping rate of an obliquely propagating magnetosonic (MS) wave is studied. The frequency of the MS wave is assumed to be less than ion cyclotron frequency, i.e., ω \\ll {ω }{{i}}. Under this assumption, the dispersion relation is investigated both numerically and analytically, and it is found that the real frequency of the wave is not a sensitive function of κ, but the imaginary part of the frequency is. It is also shown that for those values of κ where a large number of resonant particles participate in wave-particle interaction, the wave is heavily damped, as expected. The possible application of the results to the solar wind is discussed.
Topics in the Analysis of Shear-Wave Propagation in Oblique-Plate Impact Tests
National Research Council Canada - National Science Library
Scheidler, Mike
2007-01-01
This report addresses several topics in the theoretical analysis of shock waves, acceleration waves, and centered simple waves, with emphasis on the propagation of shear waves generated in oblique-plate impact tests...
Electromagnetic wave propagation in relativistic magnetized plasmas
International Nuclear Information System (INIS)
Weiss, I.
1985-01-01
An improved mathematical technique and a new code for deriving the conductivity tensor for collisionless plasmas have been developed. The method is applicable to a very general case, including both hot (relativistic) and cold magnetized plasmas, with only isotropic equilibrium distributions being considered here. The usual derivation starts from the relativistic Vlasov equation and leads to an integration over an infinite sum of Bessel functions which has to be done numerically. In the new solution the integration is carried out over a product of two Bessel functions only. This reduces the computing time very significantly. An added advantage over existing codes is our capability to perform the computations for waves propagating obliquely to the magnetic field. Both improvements greatly facilitate investigations of properties of the plasma under conditions hitherto unexplored
Influence of vertically and obliquely propagating gravity waves on the polar summer mesosphere
Thurairajah, B.; Siskind, D. E.; Bailey, S. M.
2017-12-01
Polar Mesospheric Clouds (PMCs) are sensitive to changes in temperature of the cold polar summer mesosphere, which in turn are modulated by gravity waves (GWs). In this study we investigate the link between PMCs and GWs that propagate both vertically (i.e. wave propagation is directly above the source region) and obliquely (lateral or non-vertical propagation upward but away from the source region). Several observational studies have analyzed the link between PMCs and vertically propagating GWs and have reported both positive and negative correlations. Moreover, while modelling studies have noted the possibility of oblique propagation of GWs from the low-latitude stratosphere to the high-latitude mesosphere, observational studies of the influence of these waves on the polar summer mesosphere are sparse. We present a comprehensive analysis of the influence of vertically and obliquely propagating GWs on the northern hemisphere (NH) polar summer mesosphere using data from 8 PMC seasons. Temperature data from the SOFIE experiment on the AIM satellite and SABER instrument on the TIMED satellite are used to derive GW parameters. SOFIE PMC data in terms of Ice Water Content (IWC) are used to quantify the changes in the polar summer mesosphere. At high latitudes, preliminary analysis of vertically propagating waves indicate a weak but positive correlation between GWs at 50 km and GWs at the PMC altitude of 84 km. Overall there is a negative correlation between GWs at 50 km and IWC and a positive correlation between GWs at 84 km and IWC. These results and the presence of a slanted structure (slanted from the low-latitude stratosphere to the high-latitude mesosphere) in GW momentum flux suggest the possibility of a significant influence of obliquely propagating GWs on the polar summer mesosphere
Propagation and oblique collision of electron-acoustic solitons in ...
Indian Academy of Sciences (India)
Critical plasma parameter is found to distinguish the types of solitons and their interaction phase-shifts. It is shown that, depending on the critical quantum diffraction parameter cr, both compressive and rarefactive solitary excitations may exist in this plasma and their collision phase-shifts can be either positive or negative ...
Reflection of oblique electron thermal modes in an inhomogeneous plasma
International Nuclear Information System (INIS)
Ohnuma, T.; Watanabe, T.; Sanuki, H.
1980-04-01
In an inhomogeneous magnetoplasma, reflection of an oblique electron thermal mode radiated from a local source is investigated experimentally and theoretically near the electron plasma frequency layer. The experimental observation of reflection in the lower plasma density region than the f sub(p)-layer is found to be in qualitative accord with the theoretical reflection, which is obtained from a kinetic theory in an inhomogeneous magnetoplasma. The reflection of the thermal mode is also compared with that of an electromagnetic mode at the f sub(p)-layer. (author)
Oblique non-neutral solitary Alfven modes in weakly nonlinear pair plasmas
International Nuclear Information System (INIS)
Verheest, Frank; Lakhina, G S
2005-01-01
The equal charge-to-mass ratio for both species in pair plasmas induces a decoupling of the linear eigenmodes between waves that are charge neutral or non-neutral, also at oblique propagation with respect to a static magnetic field. While the charge-neutral linear modes have been studied in greater detail, including their weakly and strongly nonlinear counterparts, the non-neutral mode has received less attention. Here the nonlinear evolution of a solitary non-neutral mode at oblique propagation is investigated in an electron-positron plasma. Employing the framework of reductive perturbation analysis, a modified Korteweg-de Vries equation (with cubic nonlinearity) for the lowest-order wave magnetic field is obtained. In the linear approximation, the non-neutral mode has its magnetic component orthogonal to the plane spanned by the directions of wave propagation and of the static magnetic field. The linear polarization is not maintained at higher orders. The results may be relevant to the microstructure in pulsar radiation or to the subpulses
Oblique Interaction of Dust-ion Acoustic Solitons with Superthermal Electrons in a Magnetized Plasma
Parveen, Shahida; Mahmood, Shahzad; Adnan, Muhammad; Qamar, Anisa
2018-01-01
The oblique interaction between two dust-ion acoustic (DIA) solitons travelling in the opposite direction, in a collisionless magnetized plasma composed of dynamic ions, static dust (positive/negative) charged particles and interialess kappa distributed electrons is investigated. By employing extended Poincaré-Lighthill-Kuo (PLK) method, Korteweg-de Vries (KdV) equations are derived for the right and left moving low amplitude DIA solitons. Their trajectories and corresponding phase shifts before and after their interaction are also obtained. It is found that in negatively charged dusty plasma above the critical dust charged to ion density ratio the positive polarity pulse is formed, while below the critical dust charged density ratio the negative polarity pulse of DIA soliton exist. However it is found that only positive polarity pulse of DIA solitons exist for the positively charged dust particles case in a magnetized nonthermal plasma. The nonlinearity coefficient in the KdV equation vanishes for the negatively charged dusty plasma case for a particular set of parameters. Therefore, at critical plasma density composition for negatively charged dust particles case, the modified Korteweg-de Vries (mKdV) equations having cubic nonlinearity coefficient of the DIA solitons, and their corresponding phase shifts are derived for the left and right moving solitons. The effects of the system parameters including the obliqueness of solitons propagation with respect to magnetic field direction, superthermality of electrons and concentration of positively/negatively static dust charged particles on the phase shifts of the colliding solitons are also discussed and presented numerically. The results are applicable to space magnetized dusty plasma regimes.
The properties of fast and slow oblique solitons in a magnetized plasma
McKenzie, J. F.; Doyle, T. B.
2002-01-01
This work builds on a recent treatment by McKenzie and Doyle [Phys. Plasmas 8, 4367 (2001)], on oblique solitons in a cold magnetized plasma, to include the effects of plasma thermal pressure. Conservation of total momentum in the direction of wave propagation immediately shows that if the flow is supersonic, compressive (rarefactive) changes in the magnetic pressure induce decelerations (accelerations) in the flow speed, whereas if the flow is subsonic, compressive (rarefactive) changes in the magnetic pressure induce accelerations (decelerations) in the flow speed. Such behavior is characteristic of a Bernoulli-type plasma momentum flux which exhibits a minimum at the plasma sonic point. The plasma energy flux (kinetic plus enthalpy) also shows similar Bernoulli-type behavior. This transonic effect is manifest in the spatial structure equation for the flow speed (in the direction of propagation) which shows that soliton structures may exist if the wave speed lies either (i) in the range between the fast and Alfven speeds or (ii) between the sound and slow mode speed. These conditions follow from the requirement that a defined, characteristic "soliton parameter" m exceeds unity. It is in this latter slow soliton regime that the effects of plasma pressure are most keenly felt. The equilibrium points of the structure equation define the center of the wave. The structure of both fast and slow solitons is elucidated through the properties of the energy integral function of the structure equation. In particular, the slow soliton, which owes its existence to plasma pressure, may have either a compressive or rarefactive nature, and exhibits a rich structure, which is revealed through the spatial structure of the longitudinal speed and its corresponding transverse velocity hodograph.
The properties of fast and slow oblique solitons in a magnetized plasma
International Nuclear Information System (INIS)
McKenzie, J.F.; Doyle, T.B.
2002-01-01
This work builds on a recent treatment by McKenzie and Doyle [Phys. Plasmas 8, 4367 (2001)], on oblique solitons in a cold magnetized plasma, to include the effects of plasma thermal pressure. Conservation of total momentum in the direction of wave propagation immediately shows that if the flow is supersonic, compressive (rarefactive) changes in the magnetic pressure induce decelerations (accelerations) in the flow speed, whereas if the flow is subsonic, compressive (rarefactive) changes in the magnetic pressure induce accelerations (decelerations) in the flow speed. Such behavior is characteristic of a Bernoulli-type plasma momentum flux which exhibits a minimum at the plasma sonic point. The plasma energy flux (kinetic plus enthalpy) also shows similar Bernoulli-type behavior. This transonic effect is manifest in the spatial structure equation for the flow speed (in the direction of propagation) which shows that soliton structures may exist if the wave speed lies either (i) in the range between the fast and Alfven speeds or (ii) between the sound and slow mode speed. These conditions follow from the requirement that a defined, characteristic 'soliton parameter' m exceeds unity. It is in this latter slow soliton regime that the effects of plasma pressure are most keenly felt. The equilibrium points of the structure equation define the center of the wave. The structure of both fast and slow solitons is elucidated through the properties of the energy integral function of the structure equation. In particular, the slow soliton, which owes its existence to plasma pressure, may have either a compressive or rarefactive nature, and exhibits a rich structure, which is revealed through the spatial structure of the longitudinal speed and its corresponding transverse velocity hodograph
Energy Technology Data Exchange (ETDEWEB)
Alinejad, H. [Department of Physics, Faculty of Basic Science, Babol University of Technology, Babol 47148-71167 (Iran, Islamic Republic of)
2012-05-15
The linear and nonlinear propagation of ion-acoustic waves are investigated in a magnetized electron-positron-ion (e-p-i) plasma with nonthermal electrons. In the linear regime, the propagation of two possible modes and their evolution are studied via a dispersion relation. In the cases of parallel and perpendicular propagation, it is shown that these two possible modes are always stable. Then, the Korteweg-de Vries equation describing the dynamics of ion-acoustic solitary waves is derived from a weakly nonlinear analysis. The influence on the solitary wave characteristics of relevant physical parameters such as nonthermal electrons, magnetic field, obliqueness, positron concentration, and temperature ratio is examined. It is observed that the increasing nonthermal electrons parameter makes the solitary structures much taller and narrower. Also, it is revealed that the magnetic field strength makes the solitary waves more spiky. The present investigation contributes to the physics of the nonlinear electrostatic ion-acoustic waves in space and laboratory e-p-i plasmas in which wave damping produces an electron tail.
Directory of Open Access Journals (Sweden)
R. Kaur
2017-03-01
Full Text Available In this paper whistler mode waves have been investigated in magnetosphere of Saturn. The derivation for perturbed distribution function, dispersion relation and growth rate have been determined by using the method of characteristic and kinetic approach. Analytical expressions for growth rate and real frequency of whistlers propagating oblique to magnetic field direction are attained. Calculations have been performed at 6 radial distances in plasma sheet region of Saturn’s magnetosphere as per data provided by Cassini. Work has been extended for bi-Maxwellian as well as Loss-cone distribution function. Parametric analysis show that temperature anisotropy, increase in number density, energy density and angle of propagation increases the growth rate of whistler waves along with significant shift in wave number. In case of Loss-cone distribution, increase in growth rate of whistlers is significantly more than for bi-Maxwellian distribution function. Generation of second harmonics can also be seen in the graphs plotted. It is concluded that parallel DC field stabilizes the wave and temperature anisotropy, angle of propagation, number density and energy density of electrons enhances the growth rate. Thus the results are of importance in analyzing observed VLF emissions over wide spectrum of frequency range in Saturnian magnetosphere. The analytical model developed can also be used to study various types of instabilities in planetary magnetospheres.
Hematizadeh, Ayoob; Jazayeri, Seyed Masud; Ghafary, Bijan
2018-02-01
A scheme for excitation of terahertz (THz) radiation is presented by photo mixing of two super-Gaussian laser beams in a rippled density collisional magnetized plasma. Lasers having different frequencies and wave numbers but the same electric fields create a ponderomotive force on the electrons of plasma in the beating frequency. Super-Gaussian laser beam has the exclusive features such as steep gradient in laser intensity distribution, wider cross-section in comparison with Gaussian profiles, which make stronger ponderomotive force and higher THz radiation. The magnetic field is considered oblique to laser beams propagation direction; in this case, depending on the phase matching conditions different mode waves can propagate in plasma. It is found that amplitude and efficiency of the emitted THz radiation not only are sensitive to the beating frequency, collision frequency, and magnetic field strength but to the angle between laser beams and static magnetic field. The efficiency of THz radiation can be optimized in a certain angle.
Oblique propagation of nonlinear hydromagnetic waves: One- and two-dimensional behavior
International Nuclear Information System (INIS)
Malara, F.; Elaoufir, J.
1991-01-01
The one- and two-dimensional behavior of obliquely propagating hydromagnetic waves is analyzed by means of analytical theory and numerical simulations. It is shown that the nonlinear evolution of a one-dimensional MHD wave leads to the formation of a rotational discontinuity and a compressive steepened quasi-linearly polarized pulse whose structure is similar to that of a finite amplitude magnetosonic simple wave. For small propagation angles, the pulse mode (fast or slow) depends on the value of β with respect to unity while for large propagation angles the wave mode is fixed by the sign of the initial density-field correlation. The two-dimensional evolution shows that an MHD wave is unstable against a small-amplitude long-wavelength modulation in the direction transverse to the wave propagation direction. A two-dimensional magnetosonic wave solution is found, in which the density fluctuation is driven by the corresponding total pressure fluctuation, exactly as in the one-dimensional simple wave. Along with the steepening effect, the wave experiences both wave front deformation and a self-focusing effect which may eventually lead to the collapse of the wave. The results compare well with observations of MHD waves in the Earth's foreshock and at comets
Mahmood, S.; Sadiq, Safeer; Haque, Q.; Ali, Munazza Z.
2016-06-01
The obliquely propagating arbitrary amplitude electrostatic wave is studied in a dense magnetized plasma having singly and doubly charged helium ions with nonrelativistic and ultrarelativistic degenerate electrons pressures. The Fermi temperature for ultrarelativistic degenerate electrons described by N. M. Vernet [(Cambridge University Press, Cambridge, 2007), p. 57] is used to define ion acoustic speed in ultra-dense plasmas. The pseudo-potential approach is used to solve the fully nonlinear set of dynamic equations for obliquely propagating electrostatic waves in a dense magnetized plasma containing helium ions. The upper and lower Mach number ranges for the existence of electrostatic solitons are found which depends on the obliqueness of the wave propagation with respect to applied magnetic field and charge number of the helium ions. It is found that only compressive (hump) soliton structures are formed in all the cases and only subsonic solitons are formed for a singly charged helium ions plasma case with nonrelativistic degenerate electrons. Both subsonic and supersonic soliton hump structures are formed for doubly charged helium ions with nonrelativistic degenerate electrons and ultrarelativistic degenerate electrons plasma case containing singly as well as doubly charged helium ions. The effect of propagation direction on the soliton amplitude and width of the electrostatic waves is also presented. The numerical plots are also shown for illustration using dense plasma parameters of a compact star (white dwarf) from literature.
Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma
International Nuclear Information System (INIS)
Panwar, A.; Ryu, C. M.; Bains, A. S.
2014-01-01
A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c ,κ h , cold to hot electron temperature ratio σ, angle of propagation and ion cyclotron frequency ω ci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present
Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields
Directory of Open Access Journals (Sweden)
M. D. Sciffer
2004-04-01
Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes.
Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation
Electron Beam Propagation in a Plasma
Directory of Open Access Journals (Sweden)
Kyoung W. Min
1988-06-01
Full Text Available Electron beam propagation in a fully ionized plasma has been studied using a one-dimensional particle simulation model. We compare the results of electrostatic simulations to those of electromagnetic simulations. The electrostatic results show the essential features of beam-plasma instability which accelerates ambient plasmas. The results also show the heating of ambient plasmas and the trapping of plasmas due to the locally generated electric field. The level of the radiation generated by the same non-relativistic beam is slightly higher than the noise level. We discuss the results in context of the heating of coronal plasma during solar flares.
Omura, Y.; Hsieh, Y. K.; Foster, J. C.; Erickson, P. J.; Kletzing, C.; Baker, D. N.
2017-12-01
A recent test particle simulation of obliquely propagating whistler mode wave-particle interaction [Hsieh and Omura, 2017] shows that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. An electron moving with a parallel velocity equal to the parallel phase velocity of an obliquely propagating wave basically see a stationary wave phase. Since the electron position is displaced from its gyrocenter by a distance ρ*sin(φ), where ρ is the gyroradius and φ is the gyrophase, the wave phase is modulated with the gyromotion, and the stationary wave fields as seen by the electron are expanded as series of Bessel functions Jn with phase variations n*φ. The J1 components of the wave electric and magnetic fields rotate in the right-hand direction with the gyrofrequency, and they can be in resonance with the electron undergoing the gyromotion, resulting in effective electron acceleration and pitch angle scattering. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [Foster et al., 2017], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes.References:[1] Hsieh, Y.-K., and Y. Omura (2017), Nonlinear dynamics of electrons interacting with oblique whistler mode chorus in the magnetosphere, J. Geophys. Res. Space Physics, 122, 675-694, doi:10.1002/2016JA023255.[2] Foster, J. C., P. J. Erickson, Y. Omura, D. N. Baker, C. A. Kletzing, and S. G. Claudepierre (2017), Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear
Modulational instability of the obliquely modulated ion acoustic waves in a warm ion plasma
International Nuclear Information System (INIS)
Saxena, M.K.; Arora, A.K.; Sharma, S.R.
1981-01-01
Using KBM. perturbation technique, it is shown that the modulationally unstable domain in the (kappa - phi) plane for the obliquely modulated ion acoustic waves is appreciably modified due to the finite ion temperature. It is also shown that in a collisionless plasma having small TAUsub(i)/TAUsub(e) ( 0 approximately 0.1) may exceed the Landau damping rate provided the modulation is sufficiently oblique. (author)
Oblique Modulation of Ion-Acoustic Waves in a Warm Plasma
International Nuclear Information System (INIS)
Xue Jukui; Tang Rongan
2003-01-01
The stability of oblique modulation of ion-acoustic waves in an unmagnetized warm plasma is studied. A nonlinear Schroedinger equation governing the slow modulation of the wave amplitude is derived. The effect of temperature on the oblique modulational instability of the ion-acoustic wave is investigated. It is found that the ion temperature significantly changes the domain of the modulational instability in the k-θ plane
Study of the state of the plasma produced by oblique-incident laser
International Nuclear Information System (INIS)
Sheng Jiatian; Zhang Guoping; Liu Wei; Ye Chunfu; Hu Shengyong
1997-01-01
The plasma state and the gain region produced by the oblique-incidence laser on Ge target are studied and are compared with that produced by the vertical one. As a result of study, the absorption efficiency of the pumping energy turns far smaller, the plasma state changes remarkable and the gain region becomes much narrower when incident angle is greater than 30 degree
Submillimeter wave propagation in tokamak plasmas
International Nuclear Information System (INIS)
Ma, C.H.; Hutchinson, D.P.; Staats, P.A.; Vander Sluis, K.L.; Mansfield, D.K.; Park, H.; Johnson, L.C.
1985-01-01
The propagation of submillimeter-waves (smm) in tokamak plasmas has been investigated both theoretically and experimentally to ensure successful measurements of electron density and plasma current distributions in tokamak devices. Theoretical analyses have been carried out to study the polarization of the smm waves in TFTR and ISX-B tokamaks. A multichord smm wave interferometer/polarimeter system has been employed to simultaneously measure the line electron density and poloidal field-induced Faraday rotation in the ISX-B tokamak. The experimental study on TFTR is under way. Computer codes have been developed and have been used to study the wave propagation and to reconstruct the distributions of plasma current and density from the measured data. The results are compared with other measurements
Submillimeter wave propagation in tokamak plasmas
International Nuclear Information System (INIS)
Ma, C.H.; Hutchinson, D.P.; Staats, P.A.; Vander Sluis, K.L.; Mansfield, D.K.; Park, H.; Johnson, L.C.
1986-01-01
Propagation of submillimeter waves (smm) in tokamak plasma was investigated both theoretically and experimentally to ensure successful measurements of electron density and plasma current distributions in tokamak devices. Theoretical analyses were carried out to study the polarization of the smm waves in TFTR and ISX-B tokamaks. A multichord smm wave interferometer/polarimeter system was employed to simultaneously measure the line electron density and poloidal field-induced Faraday rotation in the ISX-B tokamak. The experimental study on TFTR is under way. Computer codes were developed and have been used to study the wave propagation and to reconstruct the distributions of plasma current and density from the measured data. The results are compared with other measurements. 5 references, 2 figures
Plasmas fluxes to surfaces for an oblique magnetic field
International Nuclear Information System (INIS)
Pitcher, C.S.; Stangeby, P.C.; Elder, J.D.; Bell, M.G.; Kilpatrick, S.J.; Manos, D.M.; Medley, S.S.; Owens, D.K.; Ramsey, A.T.; Ulrickson, M.
1992-07-01
The poloidal and toroidal spatial distributions of D α , He I and C II emission have been obtained in the vicinity of the TFTR bumper limiter and are compared with models of ion flow to the surface. The distributions are found not to agree with a model (the ''Cosine'' model) which determines the incident flux density using only the parallel fluxes in the scrape-off layer and the projected area of the surface perpendicular to the field lines. In particular, the Cosine model is not able to explain the significant fluxes observed at locations on the surface which are oblique to the magnetic field. It is further shown that these fluxes cannot be explained by the finite Larmor radius of impinging ions. Finally, it is demonstrated, with the use of Monte Carlo codes, that the distributions can be explained by including both parallel and cross-field transport onto the limiter surface
Harmonic surface wave propagation in plasma
International Nuclear Information System (INIS)
Shivarova, A.; Stoychev, T.
1980-01-01
Second order harmonic surface waves generated by one fundamental high-frequency surface wave are investigated experimentally in gas discharge plasma. Two types of harmonic waves of equal frequency, associated with the linear dispersion relation and the synchronism conditions relatively propagate. The experimental conditions and the different space damping rates of the waves ensure the existence of different spatial regions (consecutively arranged along the plasma column) of a dominant propagation of each one of these two waves. Experimental data are obtained both for the wavenumbers and the space damping rates by relatively precise methods for wave investigations such as the methods of time-space diagrams and of phase shift measurements. The results are explained by the theoretical model for nonlinear mixing of dispersive waves. (author)
Acoustic propagation mode in a cylindrical plasma
International Nuclear Information System (INIS)
Ishida, Yoshio; Idehara, Toshitaka; Inada, Hideyo
1975-01-01
The sound velocity in a cylindrical plasma produced by a high frequency discharge is measured by an interferometer system. The result shows that the acoustic wave guide effect does exist in a neutral gas and in a plasma. It is found that the wave propagates in the mode m=2 in a rigid boundary above the cut-off frequency fsub(c) and in the mode m=0 below fsub(c). Because the mode m=0 is identical to a plane wave, the sound velocity in free space can be evaluated exactly. In the mode m=2, the sound velocity approaches the free space value, when the frequency increases sufficiently. (auth.)
Wave propagation on a plasma media
International Nuclear Information System (INIS)
Torres-Silva, H.; Villarroel-Gonzalez, C.; Reggiani, N.; Sakanaka, P.H.
1995-01-01
Chiral-media and ferrite media have been studied over the last decade for many applications. Chiral-media have been examined as coating for reducing radar cross section, for antennas and arrays, for antenna radomes in waveguides and for microstrip substrate. Here, we examine a chiral-plasma medium, where the plasma part of the composite medium is non-reciprocal due to the external magnetic field, to find the general dispersion relation giving the ω against K behavior, vector phasor Helmholtz based equations are derived. We determine the modal eigenvalue properties in the chiral-plasma medium, which is doubly anisotropic. For the case of waves which propagate parallel to the magnetic field is a cold magnetized chiro-plasma. We compare our results with the typical results obtained for a cold plasma. Also we obtain the chiral-Faraday rotation which can be compared with the typical Faraday rotation for a pair of right-and left-handed circularly polarized waves. (author). 5 refs., 2 figs
Hizanidis, Kyriakos; Vlahos, L.; Polymilis, C.
1989-01-01
The relativistic motion of an ensemble of electrons in an intense monochromatic electromagnetic wave propagating obliquely in a uniform external magnetic field is studied. The problem is formulated from the viewpoint of Hamiltonian theory and the Fokker-Planck-Kolmogorov approach analyzed by Hizanidis (1989), leading to a one-dimensional diffusive acceleration along paths of constant zeroth-order generalized Hamiltonian. For values of the wave amplitude and the propagating angle inside the analytically predicted stochastic region, the numerical results suggest that the diffusion probes proceeds in stages. In the first stage, the electrons are accelerated to relatively high energies by sampling the first few overlapping resonances one by one. During that stage, the ensemble-average square deviation of the variable involved scales quadratically with time. During the second stage, they scale linearly with time. For much longer times, deviation from linear scaling slowly sets in.
Bandgap characteristics of 2D plasma photonic crystal with oblique incidence: TM case
International Nuclear Information System (INIS)
Xie Ying-Tao; Yang Li-Xia
2011-01-01
A novel periodic boundary condition (PBC), that is the constant transverse wavenumber (CTW) method, is introduced to solve the time delay in the transverse plane with oblique incidence. Based on the novel PBC, the FDTD/PBC algorithm is proposed to study periodic structure consisting of plasma and vacuum. Then the reflection coefficient for the plasma slab from the FDTD/PBC algorithm is compared with the analytic results to show the validity of our technique. Finally, the reflection coefficients for the plasma photonic crystals are calculated using the FDTD/PBC algorithm to study the variation of bandgap characteristics with the incident angle and the plasma parameters. Thus it has provided the guiding sense for the actual manufacturing plasma photonic crystal. (general)
Oblique Propagation and Dissipation of Alfvén Waves in Coronal ...
Indian Academy of Sciences (India)
velocity and energy flux density as the propagation angle of Alfvén waves increases inside the coronal holes. For any propagation angle, the energy flux density and damping length scale also show a decrement in the source region of the solar wind (<1.05 R⊙) where these may be one of the pri- mary energy sources ...
Counterstreaming magnetized plasmas. II. Perpendicular wave propagation
International Nuclear Information System (INIS)
Tautz, R.C.; Schlickeiser, R.
2006-01-01
The properties of longitudinal and transverse oscillations in magnetized symmetric counterstreaming Maxwellian plasmas with equal thermal velocities for waves propagating perpendicular to the stream direction are investigated on the basis of Maxwell equations and the nonrelativistic Vlasov equation. With the constraint of vanishing particle flux in the stream direction, three distinct dispersion relations are known, which are the ordinary-wave mode, the Bernstein wave mode, and the extraordinary electromagnetic wave mode, where the latter two are only approximations. In this article, all three dispersion relations are evaluated for a counterstreaming Maxwellian distribution function in terms of the hypergeometric function 2 F 2 . The growth rates for the ordinary-wave mode are compared to earlier results by Bornatici and Lee [Phys. Fluids 13, 3007 (1970)], who derived approximate results, whereas in this article the exact dispersion relation is solved numerically. The original results are therefore improved and show differences of up to 21% to the results obtained in this article
Energy Technology Data Exchange (ETDEWEB)
Merritt, Elizabeth C., E-mail: emerritt@lanl.gov; Adams, Colin S. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); University of New Mexico, Albuquerque, New Mexico 87131 (United States); Moser, Auna L.; Hsu, Scott C., E-mail: scotthsu@lanl.gov; Dunn, John P.; Miguel Holgado, A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Gilmore, Mark A. [University of New Mexico, Albuquerque, New Mexico 87131 (United States)
2014-05-15
We report spatially resolved measurements of the oblique merging of two supersonic laboratory plasma jets. The jets are formed and launched by pulsed-power-driven railguns using injected argon, and have electron density ∼10{sup 14} cm{sup −3}, electron temperature ≈1.4 eV, ionization fraction near unity, and velocity ≈40 km/s just prior to merging. The jet merging produces a few-cm-thick stagnation layer, as observed in both fast-framing camera images and multi-chord interferometer data, consistent with collisional shock formation [E. C. Merritt et al., Phys. Rev. Lett. 111, 085003 (2013)].
HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere
Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.
2014-12-01
In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.
EM wave propagation analysis in plasma covered radar absorbing material
Singh, Hema; Rawat, Harish Singh
2017-01-01
This book focuses on EM propagation characteristics within multilayered plasma-dielectric-metallic media. The method used for analysis is impedance transformation method. Plasma covered radar absorbing material is approximated as a multi-layered dielectric medium. The plasma is considered to be bounded homogeneous/inhomogeneous medium. The reflection coefficient and hence return loss is analytically derived. The role of plasma parameters, such as electron density, collision frequency, plasma thickness, and plasma density profile in the absorption behavior of multi-layered plasma-RAM structure is described. This book provides a clearer picture of EM propagation within plasma. The reader will get an insight of plasma parameters that play significant role in deciding the absorption characteristics of plasma covered surfaces.
Numerical study of plasma-wall transition in an oblique magnetic field
International Nuclear Information System (INIS)
Valsaque, Fabrice; Manfredi, Giovanni
2001-01-01
The interaction of a plasma with a fixed wall is investigated numerically. The ions are described by a kinetic model, while the electrons are assumed to be at thermal equilibrium. Finite Debye length effects are taken into account. An Eulerian code is used for the ion dynamics, which enables us to obtain a fine resolution of both position and velocity space. First, we analyse the effect of ionization and collisions, which bring the ion flow to supersonic velocity at the entrance of the Debye sheath (Bohm's criterion). Second, we consider a collisionless sheath with an oblique magnetic field. A magnetic presheath, which has a width of several ion gyroradii, is located between the Debye sheath and the bulk plasma. We perform a systematic numerical study of these sheaths for different incidences of the magnetic field
Experimental analysis of an oblique turbulent flame front propagating in a stratified flow
Energy Technology Data Exchange (ETDEWEB)
Galizzi, C.; Escudie, D. [Universite de Lyon, CNRS, CETHIL, INSA-Lyon, UMR5008, F-69621 Cedex (France)
2010-12-15
This paper details the experimental study of a turbulent V-shaped flame expanding in a nonhomogeneous premixed flow. Its aim is to characterize the effects of stratification on turbulent flame characteristics. The setup consists of a stationary V-shaped flame stabilized on a rod and expanding freely in a lean premixed methane-air flow. One of the two oblique fronts interacts with a stratified slice, which has an equivalence ratio close to one and a thickness greater than that of the flame front. Several techniques such as PIV and CH{sup *} chemiluminescence are used to investigate the instantaneous fields, while laser Doppler anemometry and thermocouples are combined with a concentration probe to provide information on the mean fields. First, in order to provide a reference, the homogeneous turbulent case is studied. Next, the stratified turbulent premixed flame is investigated. Results show significant modifications of the whole flame and of the velocity field upstream of the flame front. The analysis of the geometric properties of the stratified flame indicates an increase in flame brush thickness, closely related to the local equivalence ratio. (author)
A Study of Stress Wave Propagation in Thin Plate Loaded by an Oblique Impact
Czech Academy of Sciences Publication Activity Database
Trnka, Jan; Kolman, Radek; Dvořáková, Pavla; Veselý, Eduard
2009-01-01
Roč. 3, č. 3 (2009), s. 322-331 ISSN 1970-8734 R&D Projects: GA ČR GA101/07/0588; GA ČR GA101/06/0914 Institutional research plan: CEZ:AV0Z20760514 Keywords : Stress wave propagation * Thin-wall structures * Double-pulse holointerferometry * Finite Element Method Subject RIV: BH - Optics, Masers, Lasers
Laser beam trapping and propagation in cylindrical plasma columns
International Nuclear Information System (INIS)
Feit, M.D.; Fleck, J.A. Jr.
1976-01-01
An analysis of the scheme to heat magnetically confined plasma columns to kilovolt temperatures with a laser beam requires consideration of two propagation problems. The first question to be answered is whether stable beam trapping is possible. Since the laser beam creates its own density profile by heating the plasma, the propagation of the beam becomes a nonlinear phenomenon, but not necessarily a stable one. In addition, the electron density at a given time depends on the preceding history of both the medium and the laser pulse. A self-consistent time dependent treatment of the beam propagation and the medium hydrodynamics is consequently required to predict the behavior of the laser beam. Such calculations have been carried out and indicate that propagation of a laser beam in an initially uniform plasma can form a stable filament which alternately focuses and defocuses. An additional question that is discussed is whether diffractive losses associated with long propagation paths are significant
Propagation and scattering of waves in dusty plasmas
International Nuclear Information System (INIS)
Vladimirov, S.V.
1994-01-01
Wave propagation and scattering in dusty plasmas with variable charges on dust particles are considered. New kinetic theory including instant charge of a dust particle as a new independent variable is further developed. (author). 9 refs
Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab
International Nuclear Information System (INIS)
Angus, J. R.; Krasheninnikov, S. I.; Smolyakov, A. I.
2010-01-01
The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth δ a when δ a a >>L, the heating is shown to decay with 1/δ a 3 . The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.
Propagation of electromagnetic waves in a weakly ionized dusty plasma
International Nuclear Information System (INIS)
Jia, Jieshu; Yuan, Chengxun; Gao, Ruilin; Wang, Ying; Liu, Yaoze; Gao, Junying; Zhou, Zhongxiang; Sun, Xiudong; Li, Hui; Wu, Jian; Pu, Shaozhi
2015-01-01
Propagation properties of electromagnetic (EM) waves in weakly ionized dusty plasmas are the subject of this study. Dielectric relation for EM waves propagating at a weakly ionized dusty plasma is derived based on the Boltzmann distribution law while considering the collision and charging effects of dust grains. The propagation properties of EM energy in dusty plasma of rocket exhaust are numerically calculated and studied, utilizing the parameters of rocket exhaust plasma. Results indicate that increase of dust radius and density enhance the reflection and absorption coefficient. High dust radius and density make the wave hardly transmit through the dusty plasmas. Interaction enhancements between wave and dusty plasmas are developed through effective collision frequency improvements. Numerical results coincide with observed results by indicating that GHz band wave communication is effected by dusty plasma as the presence of dust grains significantly affect propagation of EM waves in the dusty plasmas. The results are helpful to analyze the effect of dust in plasmas and also provide a theoretical basis for the experiments. (paper)
Laser propagation and compton scattering in parabolic plasma channel
Dongguo, L; Yokoya, K; Hirose, T
2003-01-01
A Gaussian laser beam propagating in a parabolic plasma channel is discussed in this paper. For a weak laser, plasma density perturbation induced by interaction between the laser field and plasma is very small, the refractive index can be assumed to be constant with respect to time variable. For a parabolic plasma channel, through the static propagation equation, we obtain an analytical solution of the profile function of the Gaussian laser beam for an unmatched case and give the general condition for the matched case. As the laser intensity increases, an effect due to strong laser fields is included. We discuss how to design and select the distribution of plasma density for a certain experiment in which a plasma channel is utilized to guide a laser beam. The number of scattered photons (X-rays) generated through Compton backscattering in a plasma channel is discussed. (author)
Propagation of strong electromagnetic beams in inhomogeneous plasmas
Energy Technology Data Exchange (ETDEWEB)
Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Ist. di Fisica Generale)
1980-09-01
We study some simple aspects of nonlinear propagation of relativistically strong electromagnetic beams in inhomogeneous plasmas, especially in connection with effects of beam self-trapping in extended extragalactic radio sources. The two effects of (i) long scale longitudinal and radial inhomogeneities inherent to the plasma and (ii) radial inhomogeneities produced by the ponderomotive force of the beam itself are investigated.
Propagation of waves in a multicomponent plasma having charged ...
Indian Academy of Sciences (India)
Propagation of waves in a multicomponent plasma having charged dust particles has been investigated by various authors in recent times as the presence of charged dust grains give rise to a new kind of modes called dust modes and it has wide applications in magneto- sphere and space plasma [1–3]. In fact, Rao et al [4] ...
Experimental studies on the plasma bullet propagation and its inhibition
International Nuclear Information System (INIS)
Karakas, Erdinc; Laroussi, Mounir
2010-01-01
Plasma bullets generated by atmospheric pressure low temperature plasma jets have recently been an active research topic due to their unique properties and their enhanced plasma chemistry. In this paper, experimental insights into the plasma bullet lifetime and its velocity are reported. Data obtained from intensified charge-coupled device camera and time-resolved optical emission spectroscopy (OES) elucidated the existence of a weakly ionized channel between the plasma bullet and its source (such as the plasma pencil). Factors responsible for the inhibition of the propagation of the bullet, such as low helium mole fraction, the magnitude of the applied voltage, and the secondary discharge ignition time, are also revealed. A new technique is discussed to accurately measure the plasma bullet velocity, using time-resolved OES. This new technique shows that during its lifetime the plasma bullet goes through launching, propagation, and ending phases. In addition, it is noted that the plasma bullet exhibits an unstable behavior at the early beginning and late ending of the propagation.
International Nuclear Information System (INIS)
Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.
2016-01-01
The experimental observation of the self–excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion–dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.
Energy Technology Data Exchange (ETDEWEB)
Choudhary, Mangilal, E-mail: mangilal@ipr.res.in [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India); Mukherjee, S.; Bandyopadhyay, P. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)
2016-08-15
The experimental observation of the self–excited dust acoustic waves (DAWs) and its propagation characteristics in the absence and presence of a floating cylindrical object is investigated. The experiments are carried out in a direct current (DC) glow discharge dusty plasma in a background of argon gas. Dust particles are found levitated at the interface of plasma and cathode sheath region. The DAWs are spontaneously excited in the dust medium and found to propagate in the direction of ion drift (along the gravity) above a threshold discharge current at low pressure. Excitation of such a low frequency wave is a result of the ion–dust streaming instability in the dust cloud. Characteristics of the propagating dust acoustic wave get modified in the presence of a floating cylindrical object of radius larger than that of the dust Debye length. Instead of propagation in the vertical direction, the DAWs are found to propagate obliquely in the presence of the floating object (kept either vertically or horizontally). In addition, a horizontally aligned floating object forms a wave structure in the cone shaped dust cloud in the sheath region. Such changes in the propagation characteristics of DAWs are explained on the basis of modified potential (or electric field) distribution, which is a consequence of coupling of sheaths formed around the cylindrical object and the cathode.
Nonlinear propagation of Alfven waves in cometary plasmas
International Nuclear Information System (INIS)
Lakhina, G.S.; Shukla, P.K.
1987-07-01
Large amplitude Alfven waves propagating along the guide magnetic field in a three-component plasma are shown to be modulationally unstable due to their nonlinear interaction with nonresonant electrostatic density fluctuations. A new class of subsonic Alfven soliton solutions are found to exist in the three-component plasma. The Alfven solitons can be relevant in explaining the properties of hydromagnetic turbulence near the comets. (author). 15 refs
Integrable, oblique travelling waves in quasi-charge-neutral two-fluid plasmas
Directory of Open Access Journals (Sweden)
G. M. Webb
2008-02-01
Full Text Available A Hamiltonian description of oblique travelling waves in a two-fluid, charge-neutral, electron-proton plasma reveals that the transverse momentum equations for the electron and proton fluids are exactly integrable in cases where the total transverse momentum flux integrals, P_{y}^{(d} and P_{z}^{(d}, are both zero in the de Hoffman Teller (dHT frame. In this frame, the transverse electric fields are zero, which simplifies the transverse momentum equations for the two fluids. The integrable travelling waves for the case P_{y}^{(d}=P_{z}^{(d}=0, are investigated based on the Hamiltonian trajectories in phase space, and also on the longitudinal structure equation for the common longitudinal fluid velocity component u_{x} of the electron and proton fluids. Numerical examples of a variety of travelling waves in a cold plasma, including oscillitons, are used to illustrate the physics. The transverse, electron and proton velocity components u_{jy} and u_{jz} (j=e, p of the waves exhibit complex, rosette type patterns over several periods for u_{x}. The role of separatrices in the phase space, the rotational integral and the longitudinal structure equation on the different wave forms are discussed.
Bursts of electron waves modulated by oblique ion waves
International Nuclear Information System (INIS)
Boswell, R.W.
1984-01-01
Experimental evidence is presented which shows small packets of electron plasma waves modulated by large amplitude obliquely propagating non-linear ion plasma waves. Very often the whole system is modulated by an oscillation near the ion gyro frequency or its harmonics. The ion waves seem to be similar to those measured in the current carrying auroral plasma. These results suggest that the generation of ion and electron waves in the auroral plasma may be correlated
Radio propagation through the turbulent interstellar plasma
International Nuclear Information System (INIS)
Rickett, B.J.
1990-01-01
The current understanding of interstellar scattering is reviewed, and its impact on radio astronomy is examined. The features of interstellar plasma turbulence are also discussed. It is concluded that methods involving the investigation of the flux variability of pulsars and extragalactic sources and the VLBI visibility curves constitute new techniques for probing the ISM. However, scattering causes a seeing limitation in radio observations. It is now clear that variation due to RISS (refractive interstellar scintillations) is likely to be important for several classes of variable sources, especially low-frequency variables and centimeter-wave flickering. 168 refs
Influence of Plasma Pressure Fluctuation on RF Wave Propagation
International Nuclear Information System (INIS)
Liu Zhiwei; Bao Weimin; Li Xiaoping; Liu Donglin; Zhou Hui
2016-01-01
Pressure fluctuations in the plasma sheath from spacecraft reentry affect radio-frequency (RF) wave propagation. The influence of these fluctuations on wave propagation and wave properties is studied using methods derived by synthesizing the compressible turbulent flow theory, plasma theory, and electromagnetic wave theory. We study these influences on wave propagation at GPS and Ka frequencies during typical reentry by adopting stratified modeling. We analyzed the variations in reflection and transmission properties induced by pressure fluctuations. Our results show that, at the GPS frequency, if the waves are not totally reflected then the pressure fluctuations can remarkably affect reflection, transmission, and absorption properties. In extreme situations, the fluctuations can even cause blackout. At the Ka frequency, the influences are obvious when the waves are not totally transmitted. The influences are more pronounced at the GPS frequency than at the Ka frequency. This suggests that the latter can mitigate blackout by reducing both the reflection and the absorption of waves, as well as the influences of plasma fluctuations on wave propagation. Given that communication links with the reentry vehicles are susceptible to plasma pressure fluctuations, the influences on link budgets should be taken into consideration. (paper)
Wave Propagation in an Ion Beam-Plasma System
DEFF Research Database (Denmark)
Jensen, T. D.; Michelsen, Poul; Juul Rasmussen, Jens
1979-01-01
The spatial evolution of a velocity- or density-modulated ion beam is calculated for stable and unstable ion beam plasma systems, using the linearized Vlasov-Poisson equations. The propagation properties are found to be strongly dependent on the form of modulation. In the case of velocity...
Propagation of a plasma streamer in catalyst pores
Zhang, Quan-Zhi; Bogaerts, Annemie
2018-03-01
Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.
Chen, Wei; Guo, Li-xin; Li, Jiang-ting
2017-04-01
This study analyzes the scattering characteristics of obliquely incident electromagnetic (EM) waves in a time-varying plasma sheath. The finite-difference time-domain algorithm is applied. According to the empirical formula of the collision frequency in a plasma sheath, the plasma frequency, temperature, and pressure are assumed to vary with time in the form of exponential rise. Some scattering problems of EM waves are discussed by calculating the radar cross section (RCS) of the time-varying plasma. The laws of the RCS varying with time are summarized at the L and S wave bands.
Wave propagation in a quasi-chemical equilibrium plasma
Fang, T.-M.; Baum, H. R.
1975-01-01
Wave propagation in a quasi-chemical equilibrium plasma is studied. The plasma is infinite and without external fields. The chemical reactions are assumed to result from the ionization and recombination processes. When the gas is near equilibrium, the dominant role describing the evolution of a reacting plasma is played by the global conservation equations. These equations are first derived and then used to study the small amplitude wave motion for a near-equilibrium situation. Nontrivial damping effects have been obtained by including the conduction current terms.
Radiation transport modelling for the interpretation of oblique ECE measurements
Directory of Open Access Journals (Sweden)
Denk Severin S.
2017-01-01
Since radiation transport modelling is required for the interpretation of oblique ECE diagnostics we present in this paper an extended forward model that supports oblique lines of sight. To account for the refraction of the line of sight, ray tracing in the cold plasma approximation was added to the model. Furthermore, an absorption coefficient valid for arbitrary propagation was implemented. Using the revised model it is shown that for the oblique ECE Imaging diagnostic at ASDEX Upgrade there can be a significant difference between the cold resonance position and the point from which most of the observed radiation originates.
Study on the electromagnetic waves propagation characteristics in partially ionized plasma slabs
Directory of Open Access Journals (Sweden)
Zhi-Bin Wang
2016-05-01
Full Text Available Propagation characteristics of electromagnetic (EM waves in partially ionized plasma slabs are studied in this paper. Such features are significant to applications in plasma antennas, blackout of re-entry flying vehicles, wave energy injection to plasmas, and etc. We in this paper developed a theoretical model of EM wave propagation perpendicular to a plasma slab with a one-dimensional density inhomogeneity along propagation direction to investigate essential characteristics of EM wave propagation in nonuniform plasmas. Particularly, the EM wave propagation in sub-wavelength plasma slabs, where the geometric optics approximation fails, is studied and in comparison with thicker slabs where the geometric optics approximation applies. The influences of both plasma and collisional frequencies, as well as the width of the plasma slab, on the EM wave propagation characteristics are discussed. The results can help the further understanding of propagation behaviours of EM waves in nonuniform plasma, and applications of the interactions between EM waves and plasmas.
Guided propagation of Alfven waves in a toroidal plasma
International Nuclear Information System (INIS)
Borg, G.G.; Brennan, M.H.; Cross, R.C.; Giannone, L.; Donnelly, I.J.
1985-01-01
Experimental results are presented which show that the Alfven wave is strongly guided by magnetic fields. The experiment was conducted in a Tokamak plasma using a small dipole loop antenna to generate a localised Alfven ray. The ray was observed, with magnetic probes, to propagate as a localised disturbance along the curved lines of the steady magnetic field without significant refraction due to the effects of finite frequency, resistivity or magnetic field gradients. These results agree with theoretical predictions and demonstrate that a localised Alfven wave may be excited, and may propagate, independently of the fast wave, as expected. The implication of these results for the Alfven wave heating scheme is discussed. (author)
Guided propagation of Alfven waves in a toroidal plasma
Energy Technology Data Exchange (ETDEWEB)
Borg, G G; Brennan, M H; Cross, R C; Giannone, L.; Donnelly, I J
1985-10-01
Experimental results are presented which show that the Alfven wave is strongly guided by magnetic fields. The experiment was conducted in a Tokamak plasma using a small dipole loop antenna to generate a localised Alfven ray. The ray was observed, with magnetic probes, to propagate as a localised disturbance along the curved lines of the steady magnetic field without significant refraction due to the effects of finite frequency, resistivity or magnetic field gradients. These results agree with theoretical predictions and demonstrate that a localised Alfven wave may be excited, and may propagate, independently of the fast wave, as expected. The implication of these results for the Alfven wave heating scheme is discussed.
Propagation of highly aberrated laser beams in nonquadratic plasma waveguides
International Nuclear Information System (INIS)
Feit, M.D.; Fleck, J.A. Jr.; Morris, J.R.
1977-01-01
The propagation of a laser beam in a plasma column several meters long with a realistic electron density distribution is examined. The electron density distribution is based on laser-beam heating at z=0, but is otherwise uncoupled to the laser beam. The aberrated nature of the resulting lenslike medium leads to essentially aperiodic beam properties, which contrast with the completely periodic properties of Gaussian beams propagating in quadratic lenslike media. The beam is nonetheless stably trapped. These aberrated-beam properties also help to stabilize the beam against axial variations in refractive index
Alfven wave propagation in a partially ionized plasma
International Nuclear Information System (INIS)
Watts, Christopher; Hanna, Jeremy
2004-01-01
Results from a laboratory study of the dispersion relation of Alfven waves propagating through a partially ionized plasma are presented. The plasma is generated using a helicon source, creating a high density, current-free discharge, where the source can be adjusted to one of several modes with varying neutral fraction. Depending on the neutral fraction, the measured dispersion curve of shear Alfven waves can change significantly. Measurement results are compared with theoretical predictions of the effect of neutral particles on Alfven wave propagation. In fitting the theory, the neutral fraction is independently estimated using two simple particle transport models, one collisionless, the other collisional. The two models predict comparable neutral fractions, and agree well with the neutral fraction required for the Alfven dispersion theory
Propagation of intense laser pulses in an underdense plasma
International Nuclear Information System (INIS)
Monot, P.; Auguste, T.; Gibbon, P.; Jakober, F.; Mainfray, G.
1994-01-01
Experiments carried out with a laser beam focused into a vacuum chamber onto a 3-mm long, pulsed hydrogen jet, at powers close to the critical power required for relativistic self focusing, have shown that an underdense plasma is able to significantly reduce the divergence of an intense laser pulse. The propagation mode is in good agreement with theoretical predictions of relativistic self focusing. 2 figs., 8 refs
Laser propagation and soliton generation in strongly magnetized plasmas
Energy Technology Data Exchange (ETDEWEB)
Feng, W.; Li, J. Q.; Kishimoto, Y. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
2016-03-15
The propagation characteristics of various laser modes with different polarization, as well as the soliton generation in strongly magnetized plasmas are studied numerically through one-dimensional (1D) particle-in-cell (PIC) simulations and analytically by solving the laser wave equation. PIC simulations show that the laser heating efficiency substantially depends on the magnetic field strength, the propagation modes of the laser pulse and their intensities. Generally, large amplitude laser can efficiently heat the plasma with strong magnetic field. Theoretical analyses on the linear propagation of the laser pulse in both under-dense and over-dense magnetized plasmas are well confirmed by the numerical observations. Most interestingly, it is found that a standing or moving soliton with frequency lower than the laser frequency is generated in certain magnetic field strength and laser intensity range, which can greatly enhance the laser heating efficiency. The range of magnetic field strength for the right-hand circularly polarized (RCP) soliton formation with high and low frequencies is identified by solving the soliton equations including the contribution of ion's motion and the finite temperature effects under the quasi-neutral approximation. In the limit of immobile ions, the RCP soliton tends to be peaked and stronger as the magnetic field increases, while the enhanced soliton becomes broader as the temperature increases. These findings in 1D model are well validated by 2D simulations.
How much laser power can propagate through fusion plasma?
International Nuclear Information System (INIS)
Lushnikov, Pavel M; Rose, Harvey A
2006-01-01
Propagation of intense laser beams is crucial for inertial confinement fusion, which requires precise beam control to achieve the compression and heating necessary to ignite the fusion reaction. The National Ignition Facility (NIF), where fusion will be attempted, is now under construction. Control of intense beam propagation may be ruined by laser beam self-focusing. We have identified the maximum laser beam power that can propagate through fusion plasma without significant self-focusing and have found excellent agreement with recent experimental data. This maximum is determined by the collective forward stimulated Brillouin scattering instability which suggests a way to increase the maximum power by appropriate choice of plasma composition with implication for NIF designs. Our theory also leads to the prediction of anti-correlation between beam spray and backscatter and therefore raises the possibility of indirect control of backscatter through manipulation of plasma ionization state or acoustic damping. We find a simple expression for laser intensity at onset of enhanced beam angular divergence (beam spray)
International Nuclear Information System (INIS)
Yang Min; Li Xiaoping; Xie Kai; Liu Donglin; Liu Yanming
2013-01-01
A large volume uniform plasma generator is proposed for the experiments of electromagnetic (EM) wave propagation in plasma, to reproduce a “black out” phenomenon with long duration in an environment of the ordinary laboratory. The plasma generator achieves a controllable approximate uniform plasma in volume of 260 mm× 260 mm× 180 mm without the magnetic confinement. The plasma is produced by the glow discharge, and the special discharge structure is built to bring a steady approximate uniform plasma environment in the electromagnetic wave propagation path without any other barriers. In addition, the electron density and luminosity distributions of plasma under different discharge conditions were diagnosed and experimentally investigated. Both the electron density and the plasma uniformity are directly proportional to the input power and in roughly reverse proportion to the gas pressure in the chamber. Furthermore, the experiments of electromagnetic wave propagation in plasma are conducted in this plasma generator. Blackout phenomena at GPS signal are observed under this system and the measured attenuation curve is of reasonable agreement with the theoretical one, which suggests the effectiveness of the proposed method.
Wave propagation in plasma-filled wave-guide
International Nuclear Information System (INIS)
Leprince, Philippe
1966-01-01
This research thesis reports the study of wave propagation along a plasma column without external magnetic field. The author first present and comment various theoretical results, and dispersion curves plotted for the main modes (particularly, the bipolar mode). He tries to define fundamental magnitudes which characterise a plasma-filled wave-guide. He reports the comparison of some experimental results with the previous theoretical results. Based on the study of the bipolar mode, the author develops a method of measurement of plasma column density. In the last part, the author reports the study of the resonance of a plasma-containing cavity. Several resonances are highlighted and new dispersion curves are plotted by using a varying length cavity. He also addresses the coupling of plasma modes with guide modes, and thus indicates the shape of Brillouin diagrams for a plasma-filled wave-guide. Moreover, some phenomena highlighted during plasma column density measurements by using the cavity method could then be explained [fr
Linear wave propagation in a hot axisymmetric toroidal plasma
International Nuclear Information System (INIS)
Jaun, A.
1995-03-01
Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell's equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models' resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs
Linear wave propagation in a hot axisymmetric toroidal plasma
Energy Technology Data Exchange (ETDEWEB)
Jaun, A [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1995-03-01
Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell`s equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models` resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs.
International Nuclear Information System (INIS)
Bourdier, A.
1983-03-01
We present a method which simplifies the investigation of the form of an oblique incident wave on a plasma. The electric field vector of the wave is assumed to be in the plane of incidence. Our method consists in introducing a new frame in which the wave is normally incident. To do so, we use a LORENTZ transformation. This way, we reduce a two-dimensional problem to a one-dimensional one. In the new frame, relativistic terms due to the drift-velocity of the plasma are taken into consideration. The solution we obtain is complementary to GINSBURG's; it is accurate for small angles of incidences. We also describe another resonance taking place at four times the critical density (N 0 = 4 Nsub(c)) [fr
Mishra, Rinku; Dey, M.
2018-04-01
An analytical model is developed that explains the propagation of a high frequency electrostatic surface wave along the interface of a plasma system where semi-infinite electron-ion plasma is interfaced with semi-infinite dusty plasma. The model emphasizes that the source of such high frequency waves is inherent in the presence of ion acoustic and dust ion acoustic/dust acoustic volume waves in electron-ion plasma and dusty plasma region. Wave dispersion relation is obtained for two distinct cases and the role of plasma parameters on wave dispersion is analyzed in short and long wavelength limits. The normalized surface wave frequency is seen to grow linearly for lower wave number but becomes constant for higher wave numbers in both the cases. It is observed that the normalized frequency depends on ion plasma frequencies when dust oscillation frequency is neglected.
Nonlinear Theory of Nonparaxial Laser Pulse Propagation in Plasma Channels
International Nuclear Information System (INIS)
Esarey, E.; Schroeder, C. B.; Shadwick, B. A.; Wurtele, J. S.; Leemans, W. P.
2000-01-01
Nonparaxial propagation of ultrashort, high-power laser pulses in plasma channels is examined. In the adiabatic limit, pulse energy conservation, nonlinear group velocity, damped betatron oscillations, self-steepening, self-phase modulation, and shock formation are analyzed. In the nonadiabatic limit, the coupling of forward Raman scattering (FRS) and the self-modulation instability (SMI) is analyzed and growth rates are derived, including regimes of reduced growth. The SMI is found to dominate FRS in most regimes of interest. (c) 2000 The American Physical Society
Propagation of dust electro-acoustic modes in dusty plasma
International Nuclear Information System (INIS)
Avinash, K.
2001-01-01
The propagation of the dust electro-acoustic (DEA) mode in dusty plasma with different electron and ion temperatures T e and T i and different ion species is studied. The critical ratio of the dust space charge to the ion space charge ε for the excitation of DEA mode is found to decrease with increasing T e /T i and increase with m i /m e (m i and m e are the ion and electron masses). Thus experiments with hydrogen plasma where electrons are sufficiently hotter than ions and where the reduction in the dust charge with ε is more than 50% are essential for the observation of self-shielding and the DEA mode
Parametric Excitations of Fast Plasma Waves by Counter-propagating Laser Beams
International Nuclear Information System (INIS)
Shvets, G.; Fisch, N.J.
2001-01-01
Short- and long-wavelength plasma waves can become strongly coupled in the presence of two counter-propagating laser pump pulses detuned by twice the cold plasma frequency. What makes this four-wave interaction important is that the growth rate of the plasma waves occurs much faster than in the more obvious co-propagating geometry
Propagation and collision of soliton rings in quantum semiconductor plasmas
International Nuclear Information System (INIS)
El-Shamy, E.F.; Gohman, F.S.
2014-01-01
The intrinsic localization of electrostatic wave energies in quantum semiconductor plasmas can be described by solitary pulses. The collision properties of these pulses are investigated. In the present study, the fundamental model includes the quantum term, degenerate pressure of the plasma species, and the electron/hole exchange–correlation effects. In cylindrical geometry, using the extended Poincaré–Lighthill–Kuo (PLK) method, the Korteweg–de Vries (KdV) equations and the analytical phase shifts after the collision of two soliton rings are derived. Typical values for GaSb and GaN semiconductors are used to estimate the basic features of soliton rings. It is found that the pulses of GaSb semiconductor carry more energies than the pulses of GaN semiconductor. In addition, the degenerate pressure terms of electrons and holes have strong impact on the phase shift. The present theory may be useful to analyze the collision of localized coherent electrostatic waves in quantum semiconductor plasmas. - Highlights: • The propagation and the collision of pulses in quantum semiconductor plasmas are studied. • Numerical calculations reveal that pulses may exist only in dark soliton rings for electron–hole quantum plasmas. • Typical values for GaSb and GaN semiconductors are used to estimate the basic features of soliton rings. • It is found that the pulses of GaSb semiconductor carry more energies than the pulses of GaN semiconductor. • The degenerate pressure terms of electrons and holes have strong impact on the phase shift
Propagation characteristics of electromagnetic waves in dusty plasma with full ionization
Dan, Li; Guo, Li-Xin; Li, Jiang-Ting
2018-01-01
This study investigates the propagation characteristics of electromagnetic (EM) waves in fully ionized dusty plasmas. The propagation characteristics of fully ionized plasma with and without dust under the Fokker-Planck-Landau (FPL) and Bhatnagar-Gross-Krook (BGK) models are compared to those of weakly ionized plasmas by using the propagation matrix method. It is shown that the FPL model is suitable for the analysis of the propagation characteristics of weakly collisional and fully ionized dusty plasmas, as is the BGK model. The influence of varying the dust parameters on the propagation properties of EM waves in the fully ionized dusty plasma was analyzed using the FPL model. The simulation results indicated that the densities and average radii of dust grains influence the reflection and transmission coefficients of fully ionized dusty plasma slabs. These results may be utilized to analyze the effects of interaction between EM waves and dusty plasmas, such as those associated with hypersonic vehicles.
FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma
Wang, Maoyan; Zhang, Meng; Li, Guiping; Jiang, Baojun; Zhang, Xiaochuan; Xu, Jun
2016-08-01
The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz (THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation (ADE) in the finite difference time domain (FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated. Finally, some potential applications for Terahertz waves in information and communication are analyzed. supported by National Natural Science Foundation of China (Nos. 41104097, 11504252, 61201007, 41304119), the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J041), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120185120012)
Plasma simulation with the Differential Algebraic Cubic Interpolated Propagation scheme
Energy Technology Data Exchange (ETDEWEB)
Utsumi, Takayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1998-03-01
A computer code based on the Differential Algebraic Cubic Interpolated Propagation scheme has been developed for the numerical solution of the Boltzmann equation for a one-dimensional plasma with immobile ions. The scheme advects the distribution function and its first derivatives in the phase space for one time step by using a numerical integration method for ordinary differential equations, and reconstructs the profile in phase space by using a cubic polynomial within a grid cell. The method gives stable and accurate results, and is efficient. It is successfully applied to a number of equations; the Vlasov equation, the Boltzmann equation with the Fokker-Planck or the Bhatnagar-Gross-Krook (BGK) collision term and the relativistic Vlasov equation. The method can be generalized in a straightforward way to treat cases such as problems with nonperiodic boundary conditions and higher dimensional problems. (author)
Simulation of crack propagation in rock in plasma blasting technology
Ikkurthi, V. R.; Tahiliani, K.; Chaturvedi, S.
Plasma Blasting Technology (PBT) involves the production of a pulsed electrical discharge by inserting a blasting probe in a water-filled cavity drilled in a rock, which produces shocks or pressure waves in the water. These pulses then propagate into the rock, leading to fracture. In this paper, we present the results of two-dimensional hydrodynamic simulations using the SHALE code to study crack propagation in rock. Three separate issues have been examined. Firstly, assuming that a constant pressure P is maintained in the cavity for a time τ , we have determined the P- τ curve that just cracks a given rock into at least two large-sized parts. This study shows that there exists an optimal pressure level for cracking a given rock-type and geometry. Secondly, we have varied the volume of water in which the initial energy E is deposited, which corresponds to different initial peak pressures Ppeak. We have determined the E- Ppeak curve that just breaks the rock into four large-sized parts. It is found that there must be an optimal Ppeak that lowers the energy consumption, but with acceptable probe damage. Thirdly, we have attempted to identify the dominant mechanism of rock fracture. We also highlight some numerical errors that must be kept in mind in such simulations.
Model of a source-driven plasma interacting with a wall in an oblique magnetic field
International Nuclear Information System (INIS)
Ahedo, E.; Carralero, D.
2009-01-01
A fluid model of a magnetized source-driven plasma is discussed for regimes with (Debye length)<<(ion Larmor radius)<<(plasma size and collisional mean-free path). Plasma collection by the wall is determined in terms of angle of incidence, magnetic strength, and plasma collisionality. For nonparallel incidence, a three-scale asymptotic analysis reveals a three-region matched structure consisting of a magnetically aligned bulk region, the Chodura layer, and the Debye sheath. Sonic Chodura and Bohm conditions define the singular region transitions. For near-parallel incidence, a separate analysis demonstrates the presence of a diffusive-collisional bulk region followed by a thin collisionless layer, which differs partially from the Chodura layer. A parametric analysis unveils the presence of four regimes depending on plasma collisionality: (1) a collisionless regime, with the magnetically channeled bulk region governed by plasma production; (2) a resistive semicollisional regime, where collisions retard the plasma transport in the bulk region; (3) a diffusive semicollisional regime, where the ExB drift dominates the ion flux in the bulk region; and (4) a collisional regime, where collisions cancel out magnetic effects. At grazing incidence, plasma collection is found to vary nonmonotonically with plasma collisionality. Nonzero Debye-length effects are discussed briefly.
International Nuclear Information System (INIS)
Ozak, N.; Ofman, L.; Viñas, A.-F.
2015-01-01
Remote sensing observations of coronal holes show that heavy ions are hotter than protons and their temperature is anisotropic. In-situ observations of fast solar wind streams provide direct evidence for turbulent Alfvén wave spectrum, left-hand polarized ion-cyclotron waves, and He ++ - proton drift in the solar wind plasma, which can produce temperature anisotropies by resonant absorption and perpendicular heating of the ions. Furthermore, the solar wind is expected to be inhomogeneous on decreasing scales approaching the Sun. We study the heating of solar wind ions in inhomogeneous plasma with a 2.5D hybrid code. We include the expansion of the solar wind in an inhomogeneous plasma background, combined with the effects of a turbulent wave spectrum of Alfvénic fluctuations and initial ion-proton drifts. We study the influence of these effects on the perpendicular ion heating and cooling and on the spectrum of the magnetic fluctuations in the inhomogeneous background wind. We find that inhomogeneities in the plasma lead to enhanced heating compared to the homogenous solar wind, and the generation of significant power of oblique waves in the solar wind plasma. The cooling effect due to the expansion is not significant for super-Alfvénic drifts, and is diminished further when we include an inhomogeneous background density. We reproduce the ion temperature anisotropy seen in observations and previous models, which is present regardless of the perpendicular cooling due to solar wind expansion. We conclude that small scale inhomogeneities in the inner heliosphere can significantly affect resonant wave ion heating
Propagation of an asymmetric relativistic laser pulse in plasma
International Nuclear Information System (INIS)
Garuchava, D.P.; Murusidze, I.G.; Suramlishvili, G.I.; Tsintsadze, N.L.; Tskhakaya, D.D.
1997-01-01
The interaction of a relativistically intense asymmetric laser pulse with a plasma has been studied. The asymmetric shape of the pulse implies that the rise time of the leading edge of the pulse is much greater than the fall time of the trailing edge. The numerical simulation of the propagation of such a pulse through an underdense plasma has shown that relativistic self-focusing enhances the effect of ponderomotive self-channeling. The radial ponderomotive force totally expels the electrons from the axis creating a density channel, that is, cavitation occurs. A very short fall time of the trailing edge (τ l ω p <1) causes a rapid increase in the amplitude of a laser driven longitudinal electric field to values of a few GV/cm at the back of the pulse. The numerical simulation also has shown that the channel as well as the large-amplitude longitudinal field can be sustained in the range immediately behind the pulse, thus creating favorable conditions to accelerate a trailing bunch of electrons to extremely high energies. According to our model, the accelerating electric field can reach the value 10 GV/cm. copyright 1997 The American Physical Society
Propagation of a hybrid inferior wave in axisymmetrical plasma
International Nuclear Information System (INIS)
Fivaz, M.; Appert, K.; Krlin, L.
1990-05-01
The linear propagation of hybrid inferior waves in an axisymmetrical plasma (magnetohydrodynamic equilibrium of the Soloviev type) has been numerically simulated. The evolution of k // (component of the wave vector k parallel to the magnetic field B), important for current drive modelling, has been studied as a function of the geometric parameters of the equilibrium: aspect ratio, ellipticity and triangularity. The results show that k // depends abruptly on the parameters; the engendered structures are very rich. Two mechanisms by which k // increases have been shown: the 'resonance' occurring in small bands of the space of the parameters and which is associated with trajectories in (R,Z) near stabilization; a stochastic evolution resembling diffusion in equlibriums of very high triangularity. However, a strong increase of k // of a part of the waves, susceptible of engendering a current in the plasma, has only been observed in a minority of cases. In literature current drive experiments have been reported which work and whose parameters are a priori such that our model cannot be expected to show the desired growth of k // . Consequently, our model, which is similar to normally used models, does not explain the current drive. 5 refs., 16 figs
Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott
2014-10-01
We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.
Energy Technology Data Exchange (ETDEWEB)
Light, Max Eugene [Los Alamos National Laboratory
2017-04-13
This report outlines the theory underlying electromagnetic (EM) wave propagation in an unmagnetized, inhomogeneous plasma. The inhomogeneity is given by a spatially nonuniform plasma electron density n_{e}(r), which will modify the wave propagation in the direction of the gradient rn_{e}(r).
Chen, Zi-Yu; Li, Xiao-Ya; Li, Bo-Yuan; Chen, Min; Liu, Feng
2018-02-19
The production of intense isolated attosecond pulse is a major goal in ultrafast research. Recent advances in high harmonic generation from relativistic plasma mirrors under oblique incidence interactions gave rise to photon-rich attosecond pulses with circular or elliptical polarization. However, to achieve an isolated elliptical attosecond pulse via polarization gating using currently available long driving pulses remains a challenge, because polarization gating of high harmonics from relativistic plasmas is assumed only possible at normal or near-normal incidence. Here we numerically demonstrate a scheme around this problem. We show that via control of plasma dynamics by managing laser polarization, it is possible to gate an intense single attosecond pulse with high ellipticity extending to the soft X-ray regime at oblique incidence. This approach thus paves the way towards a powerful tool enabling high-time-resolution probe of dynamics of chiral systems and magnetic materials with current laser technology.
Numerical analysis of plasma-wall interaction for an oblique magnetic field
International Nuclear Information System (INIS)
Chodura, R.
1982-01-01
A numerical code is used to calculate energy and incidence angle of plasma ions and electrons impinging on an absorbing wall. Plasma particles coming from a plasma of given density and temperature traverse a transition layer with an electric space charge field perpendicular to the wall and a given magnetic field of arbitrary angle before being adsorbed in the wall. The 1d electrostatic particle code determines the electric field and the change of particle velocity distributions in the transition layer. When the incidence angle psi of the magnetic field is varied from 0 0 (normal) to 90 0 (tangential), the impact energies W of ions and electrons at the wall stay nearly unchanged. Electrons reach the wall according to an isotropic Maxwellian distribution except for large angles psi where only electrons travelling along the magnetic field have a chance to escape the plasma. Ions hit the wall at increasing angles theta for increasing psi. The incidence angle of cold ions (Tsub(i0) = 0) is always steeper than that of the magnetic field. For nearly grazing incidence angle of the magnetic field psi →90 0 the ion incidence angle theta becomes grazing as well. After the distribution function is determined the sputtering yield of wall incident ions is calculated for different magnetic field angles psi showing maximum yield for psi near to 90 0 . (orig.)
Propagation of an intense laser beam in a tapered plasma channel
International Nuclear Information System (INIS)
Jha, Pallavi; Singh, Ram Gopal; Upadhyaya, Ajay K.; Mishra, Rohit K.
2008-01-01
Propagation characteristics and modulation instability of an intense laser beam propagating in an axially tapered plasma channel, having a parabolic radial density profile, are studied. Using the source-dependent expansion technique, the evolution equation for the laser spot is set up and conditions for propagation of the laser beam with a constant spot size (matched beam) are obtained. Further, the dispersion relation and growth rate of modulation instability of the laser pulse as it propagates through linearly and quadratically tapered plasma channels, have been obtained
International Nuclear Information System (INIS)
Di Sigalotti, Leonardo G.; Sira, Eloy; Tremola, Ciro
2002-01-01
The propagation of acoustic and thermal waves in a heat conducting, hydrogen plasma, in which photoionization and photorecombination [H + +e - H+hν(χ)] processes are progressing, is re-examined here using linear analysis. The resulting dispersion equation is solved analytically and the results are compared with previous solutions for the same plasma model. In particular, it is found that wave propagation in a slightly and highly ionized hydrogen plasma is affected by crossing between acoustic and thermal modes. At temperatures where the plasma is partially ionized, waves of all frequencies propagate without the occurrence of mode crossing. These results disagree with those reported in previous work, thereby leading to a different physical interpretation of the propagation of small linear disturbances in a conducting, ionizing-recombining, hydrogen plasma
The nonlinear distortion of propagation cones of lower hybrid wave in an inhomogeneous plasma
International Nuclear Information System (INIS)
Sanuki, Heiji; Ogino, Tatsuki.
1976-12-01
Nonlinear propagation of externally driven waves in the lower hybrid frequency range in an inhomogeneous plasma are investigated. The results of finite temperature, inhomogeneity of the plasma and density depression due to the ponderomotive force are emphasized since these effects are responsible for the propagation characteristics of the waves. The results shows that the waves are localized in a spatial wave packet that propagates into the plasma center along the conical trajectory which makes a small angle with respect to the confining magnetic field. (auth.)
The density and velocity of plasma bullets propagating along one dielectric tube
Directory of Open Access Journals (Sweden)
Longfei Ji
2015-08-01
Full Text Available This study shows that the propagation of plasma bullets along one dielectric tube is strongly affected by many discharge parameters, such as the waveform of applied voltage (AC or pulsed DC, peak voltage, He flow rate, and the frequency of AC voltage. Analysis indicates that the density and velocity of plasma bullets are mainly determined by the electric field at the front of plasma bullets. These discharge parameters may significantly influence the distribution of plasma potential along the tube, thus control the electric field at the front of plasma bullets and their propagation. An increase in the pulsed DC voltage with its rise time of <40-50 ns can lead to an obvious improvement in the electric field at the front of plasma bullets, resulting in generation of a plasma in the high density gas and a fast propagation of plasma bullets. He flowing through the tube can contribute to the surface diffusion of charged species, and greatly increase the electric field at the front of plasma bullets. During the propagation of plasma bullets, their density is decreased due to the surface recombination of charged species, such as electrons and ions.
Effect of an Energy Reservoir on the Atmospheric Propagation of Laser-Plasma Filaments
Eisenmann, Shmuel; Peñano, Joseph; Sprangle, Phillip; Zigler, Arie
2008-04-01
The ability to select and stabilize a single filament during propagation of an ultrashort, high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present the first detailed measurements and numerical 3-D simulations of the longitudinal plasma density variation in a laser-plasma filament after it passes through an iris that blocks the surrounding energy reservoir. Since no compensation is available from the surrounding background energy, filament propagation is terminated after a few centimeters. For this experiment, simulations indicate that filament propagation is terminated by plasma defocusing and ionization loss, which reduces the pulse power below the effective self-focusing power. With no blockage, a plasma filament length of over a few meters was observed.
Effect of an Energy Reservoir on the Atmospheric Propagation of Laser-Plasma Filaments
International Nuclear Information System (INIS)
Eisenmann, Shmuel; Penano, Joseph; Sprangle, Phillip; Zigler, Arie
2008-01-01
The ability to select and stabilize a single filament during propagation of an ultrashort, high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present the first detailed measurements and numerical 3-D simulations of the longitudinal plasma density variation in a laser-plasma filament after it passes through an iris that blocks the surrounding energy reservoir. Since no compensation is available from the surrounding background energy, filament propagation is terminated after a few centimeters. For this experiment, simulations indicate that filament propagation is terminated by plasma defocusing and ionization loss, which reduces the pulse power below the effective self-focusing power. With no blockage, a plasma filament length of over a few meters was observed
Propagation of Gaussian laser beam in cold plasma of Drude model
International Nuclear Information System (INIS)
Wang Ying; Yuan Chengxun; Zhou Zhongxiang; Li Lei; Du Yanwei
2011-01-01
The propagation characters of Gaussian laser beam in plasmas of Drude model have been investigated by complex eikonal function assumption. The dielectric constant of Drude model is representative and applicable in describing the cold unmagnetized plasmas. The dynamics of ponderomotive nonlinearity, spatial diffraction, and collision attenuation is considered. The derived coupling equations determine the variations of laser beam and irradiation attenuation. The modified laser beam-width parameter F, the dimensionless axis irradiation intensity I, and the spatial electron density distribution n/n 0 have been studied in connection with collision frequency, initial laser intensity and beam-width, and electron temperature of plasma. The variations of laser beam and plasma density due to different selections of parameters are reasonably explained, and results indicate the feasible modification of the propagating characters of laser beam in plasmas, which possesses significance to fast ignition, extended propagation, and other applications.
Ballistic propagation of turbulence front in tokamak edge plasmas
International Nuclear Information System (INIS)
Sugita, Satoru; Itoh, Kimitaka; Itoh, Sanae-I; Yagi, Masatoshi; Fuhr, Guillaume; Beyer, Peter; Benkadda, Sadruddin
2012-01-01
The flux-driven nonlinear simulation of resistive ballooning mode turbulence with tokamak edge geometry is performed to study the non-steady component in the edge turbulence. The large-scale and dynamical events in transport are investigated in a situation where the mean flow is suppressed. Two types of dynamics are observed. One is the radial propagation of the pulse of pressure gradient, the other is the appearance/disappearance of radially elongated global structure of turbulent heat flux. The ballistic propagation is observed in the pulse of pressure gradient, which is associated with the front of turbulent heat flux. We focus on this ballistic propagation phenomenon. Both of the bump of pressure gradient and the front of heat flux propagate inward and outward direction. It is confirmed that the strong fluctuation propagates with the pulse front. It is observed that the number of pulses going outward is close to those going inward. This ballistic phenomenon does not contradict to the turbulence spreading theory. Statistical characteristics of the ballistic propagation of pulses are evaluated and compared with scaling laws which is given by the turbulence spreading theory. It is found that they give qualitatively good agreement. (paper)
Unstable propagation of a Gaussian laser beam in a plasma waveguide
International Nuclear Information System (INIS)
Feit, M.D.; Maiden, D.E.
1976-01-01
Laser heating of long magnetically confined plasma columns to fusion temperatures requires propagation of a trapped laser beam over considerable distances. The present paper employs the parabolic approximation to the wave equation to analyze the propagation of a Gaussian beam through a plasma with a parabolic transverse density profile. Although propagation is stable in the axially uniform case, exhibiting alternate focusing and defocusing of the beam, it is unstable to small axial perturbations of certain wavelengths. In particular, an exponentially growing beam radius results from perturbations at wavelengths near that associated with the alternate focusing and defocusing mentioned above
Propagation of a nonrelativistic electron beam in a plasma in a magnetic field
International Nuclear Information System (INIS)
Okuda, H.; Horton, R.; Ono, M.; Ashour-Abdalla, M.
1986-10-01
Propagation of a nonrelativistic electron beam in a plasma in a strong magnetic field has been studied using electrostatic one-dimensional particle simulation models. Electron beams of finite pulse length and of continuous injection are followed in time to study the effects of beam-plasma interaction on the beam propagation. For the case of pulsed beam propagation, it is found that the beam distribution rapidly spreads in velocity space generating a plateaulike distribution with a high energy tail extending beyond the initial beam velocity
Bowen, LI; Zhibin, WANG; Qiuyue, NIE; Xiaogang, WANG; Fanrong, KONG; Zhenyu, WANG
2018-01-01
Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of electromagnetic waves, particularly in the sub-wavelength regime. To investigate the collisional effect in such plasmas, we introduce a simplified plasma slab model with a thickness on the order of the wavelength of the incident electromagnetic wave. The scattering matrix method (SMM) is applied to solve the wave equation in the plasma slab with significant nonuniformity. Results show that the collisions between the electrons and the neutral particles, as well as the incident angle and the plasma thickness, can disturb the transmission and reduce reflection significantly.
Proton-beam propagation through wall-confined plasma channel stabilized against sausage instability
International Nuclear Information System (INIS)
Nakahama, Masao; Nemoto, Masahiro; Masugata, Katsumi; Ito, Michiaki; Matsui, Masao; Yatsui, Kiyoshi
1986-01-01
Experimental results are presented of proton-beam (energy ∼ 650 keV) propagation through wall-confined plasma channel that is stabilized against sausage instability by an externally-applied longitudinal magnetic field. Significant improvement of beam-propagation efficiency has been obtained of ∼ 70 % compared with the previous experiment of ∼ 55 % without the magnetic field. The propagation can also be available up to ∼ 30 % even in a non-propagation region in a non-stabilized channel. (author)
International Nuclear Information System (INIS)
Zhang, Shan; Hong, Xue-Ren; Wang, Hong-Yu; Xie, Bai-Song
2011-01-01
Nonparaxial and nonlinear propagation of a short intense laser beam in a parabolic plasma channel is analyzed by means of the variational method and nonlinear dynamics. The beam propagation properties are classified by five kinds of behaviors. In particularly, the electromagnetic solitary wave for finite pulse laser is found beside the other four propagation cases including beam periodically oscillating with defocussing and focusing amplitude, constant spot size, beam catastrophic focusing. It is also found that the laser pulse can be allowed to propagate in the plasma channel only when a certain relation for laser parameters and plasma channel parameters is satisfied. For the solitary wave, it may provide an effective way to obtain ultra-short laser pulse.
Propagation of electromagnetic waves in a weak collisional and fully ionized dusty plasma
Energy Technology Data Exchange (ETDEWEB)
Jia, Jieshu; Yuan, Chengxun, E-mail: yuancx@hit.edu.cn; Gao, Ruilin; Wang, Ying; Zhou, Zhong-Xiang [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Liu, Sha; Yue, Feng [Shanghai Institute of Spaceflight Control Technology, Shanghai 200233 (China); Wu, Jian [China Research Institute of Radio wave Propagation, Beijing 102206 (China); Li, Hui [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); China Research Institute of Radio wave Propagation, Beijing 102206 (China)
2016-04-15
The propagation properties of electromagnetic (EM) waves in fully ionized dusty plasmas is the subject of this study. The dielectric relationships for EM waves propagating in a fully ionized dusty plasma was derived from the Boltzmann distribution law, taking into consideration the collision and charging effects of the dust grains. The propagation properties of the EM waves in a dusty plasma were numerically calculated and studied. The study results indicated that the dusty grains with an increased radius and charge were more likely to impede the penetration of EM waves. Dust grains with large radii and high charge cause the attenuation of the EM wave in the dusty plasma. The different density of the dust in the plasma appeared to have no obvious effect on the transmission of the EM waves. The propagation of the EM waves in a weakly ionized dusty plasma varies from that in a fully ionized dusty plasma. The results are helpful to analyze the effects of dust in dusty plasmas and also provide a theoretical basis for future studies.
2D full wave simulation on electromagnetic wave propagation in toroidal plasma
International Nuclear Information System (INIS)
Hojo, Hitoshi; Uruta, Go; Nakayama, Kazunori; Mase, Atsushi
2002-01-01
Global full-wave simulation on electromagnetic wave propagation in toroidal plasma with an external magnetic field imaging a tokamak configuration is performed in two dimensions. The temporal behavior of an electromagnetic wave launched into plasma from a wave-guiding region is obtained. (author)
Propagation of electromagnetic waves in a weak collisional and fully ionized dusty plasma
International Nuclear Information System (INIS)
Jia, Jieshu; Yuan, Chengxun; Gao, Ruilin; Wang, Ying; Zhou, Zhong-Xiang; Liu, Sha; Yue, Feng; Wu, Jian; Li, Hui
2016-01-01
The propagation properties of electromagnetic (EM) waves in fully ionized dusty plasmas is the subject of this study. The dielectric relationships for EM waves propagating in a fully ionized dusty plasma was derived from the Boltzmann distribution law, taking into consideration the collision and charging effects of the dust grains. The propagation properties of the EM waves in a dusty plasma were numerically calculated and studied. The study results indicated that the dusty grains with an increased radius and charge were more likely to impede the penetration of EM waves. Dust grains with large radii and high charge cause the attenuation of the EM wave in the dusty plasma. The different density of the dust in the plasma appeared to have no obvious effect on the transmission of the EM waves. The propagation of the EM waves in a weakly ionized dusty plasma varies from that in a fully ionized dusty plasma. The results are helpful to analyze the effects of dust in dusty plasmas and also provide a theoretical basis for future studies.
International Nuclear Information System (INIS)
Wang Ying; Yuan Chengxun; Gao Ruilin; Zhou Zhongxiang
2012-01-01
Theoretical investigations of a Gaussian laser beam propagating in relativistic plasmas have been performed with the WKB method and complex eikonal function. We consider the relativistic nonlinearity induced by intense laser beam, and present the relativistically generalized forms of the plasma frequency and electron collision frequency in plasmas. The coupled differential equations describing the propagation variations of laser beam are derived and numerically solved. The obtained simulation results present the similar variation tendency with experiments. By changing the plasma density, we theoretically analyze the feasibility of using a plasmas slab of a fixed thickness to compress the laser beam-width and acquire the focused laser intensity. The present work complements the relativistic correction of the electron collision frequency with reasonable derivations, promotes the theoretical approaching to experiments and provides effective instructions to the practical laser-plasma interactions.
Revisiting the thermal effect on shock wave propagation in weakly ionized plasmas
International Nuclear Information System (INIS)
Zhou, Qianhong; Dong, Zhiwei; Yang, Wei
2016-01-01
Many researchers have investigated shock propagation in weakly ionized plasmas and observed the following anomalous effects: shock acceleration, shock recovery, shock weakening, shock spreading, and splitting. It was generally accepted that the thermal effect can explain most of the experimental results. However, little attention was paid to the shock recovery. In this paper, the shock wave propagation in weakly ionized plasmas is studied by fluid simulation. It is found that the shock acceleration, weakening, and splitting appear after it enters the plasma (thermal) region. The shock splits into two parts right after it leaves the thermal region. The distance between the splitted shocks keeps decreasing until they recover to one. This paper can explain a whole set of features of the shock wave propagation in weakly ionized plasmas. It is also found that both the shock curvature and the splitting present the same photoacoustic deflection (PAD) signals, so they cannot be distinguished by the PAD experiments.
Propagation characteristics of a Gaussian laser beam in plasma with modulated collision frequency
International Nuclear Information System (INIS)
Wang Ying; Yuan Chengxun; Zhou Zhongxiang; Gao Ruilin; Li Lei; Du Yanwei
2012-01-01
The propagation characteristics of a Gaussian laser beam in cold plasma with the electron collision frequency modulated by laser intensity are presented. The nonlinear dynamics of the ponderomotive force, which induce nonlinear self-focusing as opposed to spatial diffraction, are considered. The effective dielectric function of the Drude model and complex eikonal function are adopted in deriving coupled differential equations of the varying laser beam parameters. In the framework of ponderomotive nonlinearity, the frequency of electron collision in plasmas, which is proportional to the spatial electron density, is strongly interrelated with the laser beam propagation characteristics. Hence, the propagation properties of the laser beam and the modulated electron collision frequency distribution in plasma were studied and explained in depth. Employing this self-consistent method, the obtained simulation results approach practical conditions, which is of significance to the study of laser–plasma interactions.
Field experiments and laboratory study of plasma turbulence and effects on EM wave propagation
International Nuclear Information System (INIS)
Lee, M.C.; Kuo, S.P.
1990-01-01
Both active experiments in space and laboratory experiments with plasma chambers have been planned to investigate plasma turbulence and effects on electromagnetic wave propagation. Plasma turbulence can be generated by intense waves or occur inherently with the production of plasmas. The turbulence effects to be singled out for investigation include nonlinear mode conversion process and turbulence scattering of electromagnetic waves by plasma density fluctuations. The authors have shown theoretically that plasma density fluctuations can render the nonlinear mode conversion of electromagnetic waves into lower hybrid waves, leading to anomalous absorption of waves in magnetoplasmas. The observed spectral broadening of VLF waves is the evidence of the occurrence of this process. Since the density fluctuations may have a broad range of scale lengths, this process is effective in weakening the electromagnetic waves in a wideband. In addition, plasma density fluctuations can scatter waves and diversify the electromagnetic energy. Schemes of generating plasma turbulence and the diagnoses of plasma effects are discussed
Propagation and absorption of electromagnetic waves in fully relativistic plasmas
International Nuclear Information System (INIS)
Batchelor, D.B.; Goldfinger, R.C.; Weitzner, H.
1983-01-01
Electron cyclotron heating calculations were made for plasmas with electron temperatures above 10 keV. It was assumed that n/sub parallel/ = 0 so that Doppler broadening is not present and relativistic effects are maximum. The plasma distribution function is assumed to be an isotropic relativistic Maxwellian
Propagation velocities of laser-produced plasmas from copper wire targets and water droplets
Song, Kyo-Dong; Alexander, Dennis R.
1994-01-01
Experiments were performed to determine the plasma propagation velocities resulting from KrF laser irradiation of copper wire target (75 microns diameter) and water droplets (75 microns diameter) at irradiance levels ranging from 25 to 150 GW/sq cm. Plasma propagation velocities were measured using a streak camera system oriented orthogonally to the high-energy laser propagation axis. Plasma velocities were studied as a function of position in the focused beam. Results show that both the shape of the plasma formation and material removal from the copper wire are different and depend on whether the targets are focused or slightly defocused (approximately = 0.5 mm movement in the beam axis). Plasma formation and its position relative to the target is an important factor in determining the practical focal point during high-energy laser interaction with materials. At irradiance of 100 GW/sq cm, the air plasma has two weak-velocity components which propagate toward and away from the incident laser while a strong-velocity component propagates away from the laser beam as a detonation wave. Comparison of the measured breakdown velocities (in the range of 2.22-2.27 x 10(exp 5) m/s) for air and the value calculated by the nonlinear breakdown wave theory at irradiance of 100 GW/sq cm showed a quantitative agreement within approximately 50% while the linear theory and Gaussian pulse theory failed. The detonation wave velocities of plasma generated from water droplets and copper wire targets for different focused cases were measured and analyzed theoretically. The propagation velocities of laser-induced plasma liquid droplets obtained by previous research are compared with current work.
Time domain phenomena of wave propagation in rapidly created plasma of periodic distribution
International Nuclear Information System (INIS)
Kuo, S P
2007-01-01
Theories, experiments and numerical simulations on the interaction of electromagnetic waves with rapidly created unmagnetized plasmas are presented. In the case that plasma is created uniformly, the frequency of a propagating electromagnetic wave is upshifted. An opposite propagation wave of the same frequency is also generated. In addition, a static current supporting a wiggler magnetic field is also produced in the plasma. When a spatially periodic structure is introduced to the rapidly created plasma, the theory and numerical simulation results show that both frequency-upshifted and downshifted waves are generated. If the plasma has a large but finite dimension in the incident wave propagation direction and is created rapidly rather than instantaneously, the frequency downshifted waves are found to be trapped by the plasma when the plasma frequency is larger than the wave frequency. The wave trapping results in accumulating the frequency-downshifted waves during the finite transient period of plasma creation. Indeed, in the experimental observations the frequency downshifted signals were detected repetitively with considerably enhanced spectral intensities, confirming the results of the numerical simulations. The missing of frequency upshifted signals in the experimental observations is explained by the modal field distributions in the periodic structure, indicating that the frequency upshifted modes experience heavier collisional damping of the plasma than the frequency downshifted modes
International Nuclear Information System (INIS)
Williams, R.L.; Johnson, J.A. III
1993-01-01
The feasibility of using an ionizing shock wave to produce high density plasmas suitable for the propagation large amplitude relativistic plasma waves is being investigated. A 20 kv arc driven shock tube of coaxial geometry produces a hypersonic shock wave (10 p > 10 17 cm -3 ). The shock can be made to reflect off the end of the tube, collide with its wake, and thus increase the plasma density further. After reflecting, the plasma is at rest. The shock speed is measured using piezoelectric pressure probes and the ion density is measured using laser induced fluorescence (LIF) techniques on argon 488.0 nm and 422.8 nm lines. The future plans are to excite large amplitude relativistic plasma waves in this plasma by either injecting a short pulse laser (Laser Wake Field Scheme), two beating lasers (Plasma Beat Wave Scheme), or a short bunch of relativistic electrons (Plasma Wake Field Scheme). Results of recent computational and theoretical studies, as well as initial experimental measurements on the plasma using LIF, are reported. Implications for the application of high density plasmas produced in this way to such novel schemes as the plasma wave accelerator, photon accelerator, plasma wave undulator, and also plasma lens, are discussed. The effect of plasma turbulence is also discussed
Wave propagation near the lower hybrid resonance in toroidal plasmas
International Nuclear Information System (INIS)
Ohkubo, K.; Ohasa, K.; Matsuura, K.
1975-10-01
Dielectric tensor and equipotential curves (ray trajectories) of an electrostatic wave near the lower hybrid resonance are investigated for the toroidal plasma with a shear magnetic field. The ray trajectories start from the vicinity of the plasma surface, and rotate in a spiral form around the magnetic axis, and then reach the lower or upper parts of lower hybrid resonance layer. The numerical computations are performed on the parameters of JIPP T-II device with two dimensional inhomogeneity. (auth.)
Instability Versus Equilibrium Propagation of Laser Beam in Plasma
Lushnikov, Pavel M.; Rose, Harvey A.
2003-01-01
We obtain, for the first time, an analytic theory of the forward stimulated Brillouin scattering instability of a spatially and temporally incoherent laser beam, that controls the transition between statistical equilibrium and non-equilibrium (unstable) self-focusing regimes of beam propagation. The stability boundary may be used as a comprehensive guide for inertial confinement fusion designs. Well into the stable regime, an analytic expression for the angular diffusion coefficient is obtain...
The acceleration and propagation of energetic particles in turbulent cosmic plasmas
International Nuclear Information System (INIS)
Achterberg, A.
1981-01-01
This thesis concentrates on the acceleration and propagation of energetic particles in turbulent cosmic plasmas. The stochastic acceleration of relativistic electrons by long-wavelength weak magnetohydrodynamic turbulence is considered and a model is discussed that allows the determination of both the electron energy spectrum and the wavenumber spectrum of the magnetohydrodynamic turbulence in a consistent way. The question of second phase acceleration in large solar flares and the precise form of the force exerted on the background plasma when Alfven waves are generated by fast particles are considered. The energy balance in the shock wave acceleration, the propagation of energetic particles in a high β plasma (β>10 2 ) and sheared flow as a possible source of plasma turbulence for a magnetized plasma with field-aligned flow, are discussed. (Auth./C.F.)
On the rogue wave propagation in ion pair superthermal plasma
Energy Technology Data Exchange (ETDEWEB)
Abdelwahed, H. G., E-mail: hgomaa-eg@yahoo.com, E-mail: hgomaa-eg@mans.edu.eg; Zahran, M. A. [Physics Department, College of Sciences and Humanities Studies Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj (Saudi Arabia); Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt); El-Shewy, E. K., E-mail: emadshewy@yahoo.com; Elwakil, S. A. [Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt)
2016-02-15
Effects of superthermal electron on the features of nonlinear acoustic waves in unmagnetized collisionless ion pair plasma with superthermal electrons have been examined. The system equations are reduced in the form of the nonlinear Schrodinger equation. The rogue wave characteristics dependences on the ionic density ratio (ν = n{sub –0}/n{sub +0}), ionic mass ratio (Q = m{sub +}/m{sub −}), and superthermality index (κ) are investigated. It is worth mentioning that the results present in this work could be applicable in the Earth's ionosphere plasmas.
Magnetic Field Effects and Electromagnetic Wave Propagation in Highly Collisional Plasmas.
Bozeman, Steven Paul
The homogeneity and size of radio frequency (RF) and microwave driven plasmas are often limited by insufficient penetration of the electromagnetic radiation. To investigate increasing the skin depth of the radiation, we consider the propagation of electromagnetic waves in a weakly ionized plasma immersed in a steady magnetic field where the dominant collision processes are electron-neutral and ion-neutral collisions. Retaining both the electron and ion dynamics, we have adapted the theory for cold collisionless plasmas to include the effects of these collisions and obtained the dispersion relation at arbitrary frequency omega for plane waves propagating at arbitrary angles with respect to the magnetic field. We discuss in particular the cases of magnetic field enhanced wave penetration for parallel and perpendicular propagation, examining the experimental parameters which lead to electromagnetic wave propagation beyond the collisional skin depth. Our theory predicts that the most favorable scaling of skin depth with magnetic field occurs for waves propagating nearly parallel to B and for omega << Omega_{rm e} where Omega_{rm e} is the electron cyclotron frequency. The scaling is less favorable for propagation perpendicular to B, but the skin depth does increase for this case as well. Still, to achieve optimal wave penetration, we find that one must design the plasma configuration and antenna geometry so that one generates primarily the appropriate angles of propagation. We have measured plasma wave amplitudes and phases using an RF magnetic probe and densities using Stark line broadening. These measurements were performed in inductively coupled plasmas (ICP's) driven with a standard helical coil, a reverse turn (Stix) coil, and a flat spiral coil. Density measurements were also made in a microwave generated plasma. The RF magnetic probe measurements of wave propagation in a conventional ICP with wave propagation approximately perpendicular to B show an increase in
Supersonic propagation of ionization waves in an underdense, laser-produced plasma
International Nuclear Information System (INIS)
Constantin, C.; Back, C.A.; Fournier, K.B.; Gregori, G.; Landen, O.L.; Glenzer, S.H.; Dewald, E.L.; Miller, M.C.
2005-01-01
A laser-driven supersonic ionization wave propagating through a millimeter-scale plasma of subcritical density up to 2-3 keV electron temperatures was observed. Propagation velocities initially ten times the sound speed were measured by means of time-resolved x-ray imaging diagnostics. The measured ionization wave trajectory is modeled analytically and by a two-dimensional radiation-hydrodynamics code. The comparison to the modeling suggests that nonlocal heat transport effects may contribute to the attenuation of the heat-wave propagation
Investigation of radial propagation of electrostatic fluctuations in the IR-T1 tokamak plasma edge
Energy Technology Data Exchange (ETDEWEB)
Shariatzadeh, R; Ghoranneviss, M; Salem, M K [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University (IAU), PO Box 14665-678, Tehran (Iran, Islamic Republic of); Emami, M, E-mail: rezashariatzadeh@gmail.com [Laser and Optics Research School, NSTRI, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)
2011-01-15
The radial propagation of electrostatic fluctuation is considered extremely important for understanding cross-field anomalous transport. In this paper, two arrays of Langmuir probes are used to analyze electrostatic fluctuations in the edge of IR-T1 tokamak plasma in both the radial and the poloidal directions. The propagation characteristics of the floating potential fluctuations are analyzed by the two-point correlation technique. The wavenumber spectrum shows that there is a net radially outward propagation of turbulent fluctuations in the edge and scrape-off layer (SOL) regions. Hence, edge turbulence presumably originates from core fluctuations.
Investigation of radial propagation of electrostatic fluctuations in the IR-T1 tokamak plasma edge
International Nuclear Information System (INIS)
Shariatzadeh, R; Ghoranneviss, M; Salem, M K; Emami, M
2011-01-01
The radial propagation of electrostatic fluctuation is considered extremely important for understanding cross-field anomalous transport. In this paper, two arrays of Langmuir probes are used to analyze electrostatic fluctuations in the edge of IR-T1 tokamak plasma in both the radial and the poloidal directions. The propagation characteristics of the floating potential fluctuations are analyzed by the two-point correlation technique. The wavenumber spectrum shows that there is a net radially outward propagation of turbulent fluctuations in the edge and scrape-off layer (SOL) regions. Hence, edge turbulence presumably originates from core fluctuations.
Propagation of a TE surface mode in a relativistic electron beam–quantum plasma system
International Nuclear Information System (INIS)
Abdel Aziz, M.
2012-01-01
The dispersion properties of a transverse electric (TE) surface waves propagating along the interface between a magneto-quantum plasma–relativistic beam system and vacuum are studied by using the quantum hydrodynamic model. The general dispersion relations are derived and analyzed in some special cases of interest. Moreover, the effects of density gradients for the beam and plasma on the dispersion properties of surface waves are investigated. The kind of dispersion relations depends strongly on the ambient magnetic field B o via the gyro-frequency ω c , the quantum parameters, and the width of the plasma layer as well as the relativistic factor for the electron beam. It is found that the quantum effects play a crucial role to facilitate the propagation of TE surface waves. -- Highlights: ► Propagation of TE surface waves on bounded magneto-quantum plasma by relativistic beam is studied. ► The quantum plasma consists of transitional layer adjacent to uniform layer. ► Influence of quantum effects on the propagation of TE surface waves are taken into account. ► Effects of homogeneity and inhomogeneity for beam on TE surface waves are considered. ► It is found that quantum effects facilitate the propagation of TE surface modes.
Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams
International Nuclear Information System (INIS)
Gennady Shvets; Nathaniel J. Fisch; Alexander Pukhov
2001-01-01
Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined
Qualitative models of magnetic field accelerated propagation in a plasma due to the Hall effect
International Nuclear Information System (INIS)
Kukushkin, A.B.; Cherepanov, K.V.
2000-01-01
Two qualitatively new models of accelerated magnetic field propagation (relative to normal diffusion) in a plasma due to the Hall effect are developed within the frames of the electron magnetic hydrodynamics. The first model is based on a simple hydrodynamic approach, which, in particular, reproduces the number of known theoretical results. The second one makes it possible to obtain exact analytical description of the basic characteristics of the magnetic field accelerated propagation in a inhomogeneous iso-thermic plasma, namely, the magnetic field front and its effective width [ru
Defocusing of an ion beam propagating in background plasma due to two-stream instability
Energy Technology Data Exchange (ETDEWEB)
Tokluoglu, Erinc; Kaganovich, Igor D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2015-04-15
The current and charge neutralization of charged particle beams by background plasma enable ballistic beam propagation and have a wide range of applications in inertial fusion and high energy density physics. However, the beam-plasma interaction can result in the development of collective instabilities that may have deleterious effects on ballistic propagation of an ion beam. In the case of fast, light-ion beams, non-linear fields created by instabilities can lead to significant defocusing of the beam. We study an ion beam pulse propagating in a background plasma, which is subjected to two-stream instability between the beam ions and plasma electrons, using PIC code LSP. The defocusing effects of the instability on the beam can be much more pronounced in small radius beams. We show through simulations that a beamlet produced from an ion beam passed through an aperture can be used as a diagnostic tool to identify the presence of the two-stream instability and quantify its defocusing effects. The effect can be observed on the Neutralized Drift Compression Experiment-II facility by measuring the spot size of the extracted beamlet propagating through several meters of plasma.
Atmospheric pressure He-air plasma jet: Breakdown process and propagation phenomenon
International Nuclear Information System (INIS)
Begum, Asma; Laroussi, Mounir; Pervez, Mohammad Rasel
2013-01-01
In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 10 11 cm -3 and it reaches to the maximum of 10 12 cm -3 .
International Nuclear Information System (INIS)
Korenev, S.A.; Rubin, N.B.; Khodataev, K.V.
1982-01-01
The results of the experimental studies of the intense relativistic electron beam (IREB) propagation with ν/γ approximately 0.1, and γ approximately 1.6 (γ is an electron beam relativistic factor) in a collisionless plasma of small density over the 180 cm length are presented. Plasma is generated with the incomplete discharge over dielectric surface at the residual gas pressure of P approximately 10 -5 Torr. It is shown that the transportation efficiency may be essentially high, if the electron concentration in plasma satisfies the equilibrium conditions and if it is less or equal to the electron concentration in a beam. At concentration less than optimum one, the transportation efficiency decreases due to violations of equilibrium conditions. At high concentration the transportation efficiency also decreased due to the scattering and breaking on excited small-scale and plasma oscillations. The IREB propagation occurs without essential time delay under optimum conditions
Wave propagation in a bounded plasma with striction nonlinearity taken into account
International Nuclear Information System (INIS)
Brazhnik, V.A.; Grishaev, V.I.; Demchenko, V.V.; Pavlov, S.S.; Panchenko, V.I.; AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur)
1981-01-01
Electromagnetic wave propagation in plasma is analyzed with striction nonlinearity taken into account. The reflection of a circularly polarized wave falling on a layer of homogeneous magnetoactive plasma is analytically investigated under conditions of linear skinning. The large amplitude TE-type wave propagation along the layer of isotropic plasma is numerically determined. It is shown that the distribution of the electric field amplitude essentially differs from the one predicted from the linear theory. Some periodic distributions across the layer become possible, in particular numerical modelling makes it possible to study the evolution of solitons generated by a monochromatic pump field in an inhomogeneous plasma layer bounded by ideally conducting surfaces. It is shown that generated solitons interact with those reflected from the boundary without any change of their form [ru
Excitation of accelerating plasma waves by counter-propagating laser beams
International Nuclear Information System (INIS)
Shvets, Gennady; Fisch, Nathaniel J.; Pukhov, Alexander
2002-01-01
The conventional approach to exciting high phase velocity waves in plasmas is to employ a laser pulse moving in the direction of the desired particle acceleration. Photon downshifting then causes momentum transfer to the plasma and wave excitation. Novel approaches to plasma wake excitation, colliding-beam accelerator (CBA), which involve photon exchange between the long and short counter-propagating laser beams, are described. Depending on the frequency detuning Δω between beams and duration τ L of the short pulse, there are two approaches to CBA. First approach assumes (τ L ≅2/ω p ). Photons exchanged between the beams deposit their recoil momentum in the plasma driving the plasma wake. Frequency detuning between the beams determines the direction of the photon exchange, thereby controlling the phase of the plasma wake. This phase control can be used for reversing the slippage of the accelerated particles with respect to the wake. A variation on the same theme, super-beatwave accelerator, is also described. In the second approach, a short pulse with τ L >>ω p -1 detuned by Δω∼2ω p from the counter-propagating beam is employed. While parametric excitation of plasma waves by the electromagnetic beatwave at 2ω p of two co-propagating lasers was first predicted by Rosenbluth and Liu [M. N. Rosenbluth and C. S. Liu, Phys. Rev. Lett. 29, 701 (1972)], it is demonstrated that the two excitation beams can be counter-propagating. The advantages of using this geometry (higher instability growth rate, insensitivity to plasma inhomogeneity) are explained, and supporting numerical simulations presented
Propagation of a laser beam in a time-varying waveguide. [plasma heating for controlled fusion
Chapman, J. M.; Kevorkian, J.
1978-01-01
The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is reported. For the case of an axially uniform waveguide it is found that the basic characteristics of alternating focusing and defocusing beams are maintained. However, the intensity distribution is changed at the foci and outer-beam regions. The features of paraxial beam propagation are discussed with reference to axially varying waveguides. Laser plasma coupling is considered noting the case where laser heating produces a density distribution radially parabolic near the axis and the energy absorbed over the focal length of the plasma is small. It is found that: (1) beam-propagation stability is governed by the relative magnitude of the density fluctuations existing in the axial variation of the waveguides due to laser heating, and (2) for beam propagation in a time-varying waveguide, the global instability of the propagation is a function of the initial fluctuation growth rate as compared to the initial time rate of change in the radial curvature of the waveguide.
Propagation of microwave radiation through an inhomogeneous plasma layer in a magnetic field
Balakirev, B. A.; Bityurin, V. A.; Bocharov, A. N.; Brovkin, V. G.; Vedenin, P. V.; Mashek, I. Ch; Pashchina, A. S.; Pervov, A. Yu; Petrovskiy, V. P.; Ryazanskiy, N. M.; Shkatov, O. Yu
2018-01-01
The problem of reliable microwave communication through a plasma sheath has its origin from the beginning of space flights. During reentry of spacecraft, the plasma layer can interrupt the communication. At sufficiently high plasma density, the plasma layer either reflects or attenuates radio wave communications to and from the vehicle. In this work, we present a simple analytical one-dimensional algorithm to study the propagation of electromagnetic (EM) waves through a nonuniform plasma layer in a static nonuniform magnetic field. The experimental study of the EM wave transmission and reflection through plasma layer was carried out on the (i) microwave set and (ii) on the unit using a high-voltage pulsed discharge.
EM Modelling of RF Propagation Through Plasma Plumes
Pandolfo, L.; Bandinelli, M.; Araque Quijano, J. L.; Vecchi, G.; Pawlak, H.; Marliani, F.
2012-05-01
Electric propulsion is a commercially attractive solution for attitude and position control of geostationary satellites. Hall-effect ion thrusters generate a localized plasma flow in the surrounding of the satellite, whose impact on the communication system needs to be qualitatively and quantitatively assessed. An electromagnetic modelling tool has been developed and integrated into the Antenna Design Framework- ElectroMagnetic Satellite (ADF-EMS). The system is able to guide the user from the plume definition phases through plume installation and simulation. A validation activity has been carried out and the system has been applied to the plume modulation analysis of SGEO/Hispasat mission.
Propagation of dust-acoustic waves in weakly ionized plasmas with ...
Indian Academy of Sciences (India)
63, No. 5. — journal of. November 2004 physics pp. 1021–1030. Propagation of dust-acoustic waves in weakly ionized plasmas with dust-charge fluctuation∗. K K MONDAL. Department of Physics ... has essentially to be considered because inertia is provided by the mass of the dust particles. Moreover, the phase velocity ...
Diffusion and drift regimes of plasma ionization wave propagation in a microwave field
International Nuclear Information System (INIS)
Khodataev, K.V.; Gorelik, B.R.
1997-01-01
Investigation into diffusion and drift modes of a plasma ionization wave propagation in the microwave field are conducted within the framework of a one-dimensional model with regard to gas ionization by electron shock in an electrical field, adhesion, mobility and diffusion of electrons
Heating and ionization in MHD shock waves propagating into partially ionized plasma
International Nuclear Information System (INIS)
Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.
1975-09-01
A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)
Ion-acoustic wave propagation in plasmas with ion beams having a finite cross section--
International Nuclear Information System (INIS)
Huld, T.A.; Pe'cseli, H.L.; Rasmussen, J.J.
1990-01-01
The propagation of a low-density-modulated ion beam with finite cross section in a homogeneous plasma is considered. Analytical expressions describing a Cerenkov-like radiation pattern are obtained. An experimental setup is described that is suitable for investigating these phenomena. The results are in qualitive agreement with the analytical expressions
International Nuclear Information System (INIS)
Shvets, G.; Tushentsov, M.; Tokman, M.D.; Kryachko, A.
2005-01-01
Propagation of electromagnetic waves in magnetized plasma near the electron cyclotron frequency can be strongly modified by adding a weak magnetic undulator. For example, both right- and left-hand circularly polarized waves can propagate along the magnetic field without experiencing resonant absorption. This effect of entirely eliminating electron cyclotron heating is referred to as the undulator-induced transparency (UIT) of the plasma, and is the classical equivalent of the well-known quantum mechanical effect of electromagnetically induced transparency. The basics of UIT are reviewed, and various ways in which UIT can be utilized to achieve exotic propagation properties of electromagnetic waves in plasmas are discussed. For example, UIT can dramatically slow down the waves' group velocity, resulting in the extreme compression of the wave energy in the plasma. Compressed waves are polarized along the propagation direction, and can be used for synchronous electron or ion acceleration. Strong coupling between the two wave helicities are explored to impart the waves with high group velocities ∂ω/∂k for vanishing wave numbers k. Cross-helicity coupling for realistic density and magnetic field profiles are examined using a linearized fluid code, particle-in-cell simulations, and ray-tracing WKB calculations
Heating and ionization in MHD shock wave propagating into partially ionized plasma
International Nuclear Information System (INIS)
Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.
1975-09-01
A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)
Enhanced propagation for relativistic laser pulses in inhomogeneous plasmas using hollow channels.
Fuchs, J; d'Humières, E; Sentoku, Y; Antici, P; Atzeni, S; Bandulet, H; Depierreux, S; Labaune, C; Schiavi, A
2010-11-26
The influence of long (several millimeters) and hollow channels, bored in inhomogeneous ionized plasma by using a long pulse laser beam, on the propagation of short, ultraintense laser pulses has been studied. Compared to the case without a channel, propagation in channels significantly improves beam transmission and maintains a beam quality close to propagation in vacuum. In addition, the growth of the forward-Raman instability is strongly reduced. These results are beneficial for the direct scheme of the fast ignitor concept of inertial confinement fusion as we demonstrate, in fast-ignition-relevant conditions, that with such channels laser energy can be carried through increasingly dense plasmas close to the fuel core with minimal losses.
International Nuclear Information System (INIS)
Shvets, G.; Fisch, N.J.; Pukhov, A.
1999-01-01
The interaction of counter-propagating laser pulses in a plasma is considered. When the frequencies of the two lasers are close, nonlinear modification of the refraction index results in the mutual focusing of the two beams. A short (of order the plasma period) laser pulse can be nonlinearly focused by a long counter-propagating beam which extends over the entire guiding length. It is also demonstrated that a short ( p ) laser pulse can be superradiantly amplified by a counter-propagating long low-intensity pump while remaining ultra-short. Particle-in-Cell simulations indicate that pump depletion can be as high as 40%. This implies that the long pump is efficiently compressed in time without frequency chirping and pulse stretching, making the superradiant amplification an interesting alternative to the conventional method of producing ultra-intense pulses by the chirped-pulse amplification. copyright 1999 American Institute of Physics
On filament structure and propagation within a commercial plasma globe
International Nuclear Information System (INIS)
Burin, M. J.; Simmons, G. G.; Ceja, H. G.; Zweben, S. J.; Nagy, A.; Brunkhorst, C.
2015-01-01
The filamentary discharge seen within commercial plasma globes is commonly enjoyed yet not well understood. Here, we investigate the discharge properties of a plasma globe using a variable high voltage amplifier. We find that increasing voltage magnitude increases the number of filaments while leaving their individual structure basically unchanged, a result typical of dielectric barrier discharges. The frequency of the voltage also affects filament population but more significantly changes filament structure, with more diffuse filaments seen at lower frequencies. Voltage polarity is observed to be important, especially at lower frequencies, where for negative-gradient voltages the discharge is more diffuse, not filamentary. At late stages of the discharge circular structures appear and expand on the glass boundaries. We find no trend of discharge speed with respect to voltage variables, though this may be due to manufacturer sample-to-sample variation. Each voltage cycle the discharge expands outward at ∼10–15 km/s, a speed significantly higher than the estimated electron drift yet considerably lower than that observed for most streamers. We discuss the physics of these observations and their relation to similar discharges that can be found within nature and industry
Nonstationary propagation of a gaussian electromagnetic pulse in a decaying/growth plasma
International Nuclear Information System (INIS)
Kaushik, S.C.; Sen, R.
1975-01-01
The propagation of a gaussian electromagnetic pulse in a growing/decaying (time-dependent) plasma has been studied when the duration of the pulse is comparable with the decay/growing time of the plasma. Because of the different group velocities of the front and tail portions of the pulse, the pulse is compressed/broadened in a time-dependent plasma. The effect of absorption on the compression/broadening is found to be negligible. However, the peak value of the pulse is suppressed by attenuation. (author)
Propagation of a nonrelativistic electron beam in a plasma in a magnetic field
International Nuclear Information System (INIS)
Okuda, H.; Horton, R.; Ono, M.; Ashour-Abdalla, M.
1987-01-01
Propagation of a nonrelativistic electron beam in a plasma in a strong magnetic field has been studied using electrostatic one-dimensional particle simulation models. Electron beams of finite pulse length and of continuous injection are followed in time to study the effects of beam--plasma interaction on the beam propagation. For the case of pulsed beam propagation, it is found that the beam distribution rapidly spreads in velocity space generating a plateaulike distribution with a high energy tail extending beyond the initial beam velocity. This rapid diffusion takes place within a several amplification length of the beam--plasma instability given by (ω/sub p/ω 2 /sub b/) -1 /sup // 3 V 0 , where ω/sub p/, ω/sub b/, and V 0 are the target plasma, beam--plasma frequencies, and the beam drift speed. This plateaulike distribution, however, becomes unstable as the high energy tail electrons free-stream, generating a secondary beam. A similar process is observed to take place for the case of continuous beam injection when the beam density is small compared with the total density n/sub b//n/sub t/<1. In particular, the electron velocity distribution is found monotonically decreasing in energy, having a high energy tail whose energy reaches twice the initial beam energy. Such an electron distribution is also seen in laboratory experiments and in computer simulations performed for a uniform, periodic system
International Nuclear Information System (INIS)
Matsuda, Y.; Crawford, F.W.
1975-01-01
An economical low-noise plasma simulation model originated by Denavit is applied to a series of problems associated with electrostatic wave propagation in a one-dimensional, collisionless, Maxwellian plasma, in the absence of magnetic field. The model is described and tested, first in the absence of an applied signal, and then with a small amplitude perturbation. These tests serve to establish the low-noise features of the model, and to verify the theoretical linear dispersion relation at wave energy levels as low as 10 -6 of the plasma thermal energy: Better quantitative results are obtained, for comparable computing time, than can be obtained by conventional particle simulation models, or direct solution of the Vlasov equation. The method is then used to study propagation of an essentially monochromatic plane wave. Results on amplitude oscillation and nonlinear frequency shift are compared with available theories
Perfectly matched layers for radio wave propagation in inhomogeneous magnetized plasmas
International Nuclear Information System (INIS)
Gondarenko, Natalia A.; Guzdar, Parvez N.; Ossakow, Sidney L.; Bernhardt, Paul A.
2004-01-01
We present 1D and 2D numerical models of the propagation of high-frequency (HF) radio waves in inhomogeneous magnetized plasmas. The simulations allow one to describe the process of linear conversion of HF electromagnetic waves into electrostatic waves. The waves, launched from the lower boundary normally or at a specified angle on a layer of a magnetoactive plasma, can undergo linear conversion of the incident O-mode into a Z-mode at appropriate locations in an inhomogeneous prescribed plasma density. The numerical scheme for solving 2D HF wave propagation equations is described. The model employed the Maxwellian perfectly matched layers (PML) technique for approximating nonreflecting boundary conditions. Our numerical studies demonstrate the effectiveness of the PML technique for transparent boundary conditions for an open-domain problem
Quantum effects on propagation of bulk and surface waves in a thin quantum plasma film
International Nuclear Information System (INIS)
Moradi, Afshin
2015-01-01
The propagation of bulk and surface plasma waves in a thin quantum plasma film is investigated, taking into account the quantum effects. The generalized bulk and surface plasma dispersion relation due to quantum effects is derived, using the quantum hydrodynamic dielectric function and applying appropriate additional boundary conditions. The quantum mechanical and film geometric effects on the bulk and surface modes are discussed. It is found that quantum effects become important for a thin film of small thickness. - Highlights: • New bulk and surface plasma dispersion relations due to quantum effects are derived, in a thin quantum plasma film. • It is found that quantum effects become important for a thin quantum film of small thickness
Magnetic field propagation in a two ion species planar plasma opening switch
International Nuclear Information System (INIS)
Strauss, H. R.; Doron, R.; Arad, R.; Rubinstein, B.; Maron, Y.; Fruchtman, A.
2007-01-01
Three fluid plasma evolution equations are applied to the problem of magnetic field propagation in a planar plasma opening switch. For certain initial conditions in which Hall parameter H∼1, magnetic field penetration due to the Hall field, initially, as expected, either opposes or adds to the hydromagnetic pushing, depending on the polarity of the magnetic field relative to the density gradient. Later, however, the plasma pushing by the magnetic field is found in the case studied here to modify the plasma density in a way that the density gradient tends to align with the magnetic field gradient, effectively turning off the Hall effect. The penetration of the magnetic field then ceases and plasma pushing becomes the dominant process
Fluid simulation for two laser beams co-propagating in underdense plasma
International Nuclear Information System (INIS)
Mahdy, A.I.
2004-09-01
2D simulations code was constructed in order simulate the interactions of two co-propagating laser beams with underdense plasma. Simulations results at different laser intensities and separation-distances between the beams centroids were presented. In the results the effects of the laser intensities on the self-focusing and merging of the propagating beams were shown. In addition, the influence of increasing the separation-distance on the beams stability and trajectories were studied. A comparison with previous simulations at similar conditions was carried out in order to evaluate the numerical technique used to solve the basic equations. (author)
Atmospheric pressure He-air plasma jet: Breakdown process and propagation phenomenon
Energy Technology Data Exchange (ETDEWEB)
Begum, Asma [Independent University, Bangladesh, School of Engineering and Computer Science, Bashundhara, Dhaka (Bangladesh); Laroussi, Mounir [Old Dominion University, Department of Electrical and Computer Engineering, Norfolk, Virginia (United States); Pervez, Mohammad Rasel [Master Mind College, Department of Physics, Dhanmondi, Dhaka (Bangladesh)
2013-06-15
In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 10{sup 11} cm{sup -3} and it reaches to the maximum of 10{sup 12} cm{sup -3}.
Propagation of thermal and hydromagnetic waves in an ionizing-recombining hydrogen plasma
International Nuclear Information System (INIS)
Di Sigalotti, Leonardo G.; Sira, Eloy; Rendon, Otto; Tremola, Ciro; Mendoza-Briceno, Cesar A.
2004-01-01
The propagation of thermal and magnetohydrodynamic (MHD) waves in a heat-conducting, hydrogen plasma, threaded by an external uniform magnetic field (B) and in which photoionization and photorecombination [H + +e - H+hν(χ)] processes are progressing, is investigated here using linear analysis. The resulting dispersion equation is solved analytically for varied strength (β<<1 and ∼1) and orientation of the magnetic field, where β denotes the ratio of plasma to magnetic pressures. Application of this model to the interstellar medium shows that heat conduction governs the propagation of thermal waves only at relatively high frequencies regardless of the plasma temperature, strength, and orientation of the magnetic field. When the direction of wave propagation is held perpendicular to B (i.e., k perpendicular B), the magnetosonic phase velocity is closely Alfvenic for β<<1, while for β∼1 both the hydrostatic and magnetic pressures determine the wave velocity. As long as k parallel B, the fast (transverse) magnetosonic wave becomes an Alfven wave for all frequencies independent of the plasma temperature and field strength, while the slow (longitudinal) magnetosonic wave becomes a pure sound wave. Amplification of thermal and MHD waves always occur at low frequencies and preferentially at temperatures for which the plasma is either weakly or partially ionized. Compared to previous analysis for the same hydrogen plasma model with B=0, the presence of the magnetic field makes the functional dependence of the physical quantities span a longer range of frequencies, which becomes progressively longer as the field strength is increased
On electromagnetic wave propagation through a plasma sheath produced by a moving ionization source
International Nuclear Information System (INIS)
Semenova, V.I.
1977-01-01
Features of the interaction of electromagnetic waves are considered with a nonstationary plasma layer of a finite thickness, produced in an immovable gas by a movable ionization source. It is shown that a static magnetic field excited on the ionization front in build-up of electrons produced in the incident wave field reemits the energy to the electromagnetic wave during the plasma relaxation caused by recombination processes. As a result the electromagnetic wave of a finite amplitude may propagate behind the nonstationary layer of an ''opaque'' (ωsub(p)sup(2)>>ωsub(urc)sup((0))sup(2)) plasma as distinct from the layer of a movable stationary plasma with the same parameters
Nonlinear propagation of ultra-low-frequency electronic modes in a magnetized dusty plasma
International Nuclear Information System (INIS)
Mamun, A.A.
1999-07-01
A theoretical investigation has been made of nonlinear propagation of ultra-low-frequency electromagnetic waves in a magnetized two fluid (negatively charged dust and positively charged ion fluids) dusty plasma. These are modified Alfven waves for small value of θ and are modified magnetosonic waves for large θ, where θ is the angle between the directions of the external magnetic field and the wave propagation. A nonlinear evolution equation for the wave magnetic field, which is known as Korteweg de Vries (K-dV) equation and which admits a stationary solitary wave solution, is derived by the reductive perturbation method. The effects of external magnetic field and dust characteristics on the amplitude and the width of these solitary structures are examined. The implications of these results to some space and astrophysical plasma systems, especially to planetary ring-systems, are briefly mentioned. (author)
International Nuclear Information System (INIS)
Xia Xiongping; Qin Zhen; Xu Bin; Cai Zebin
2011-01-01
Dielectric constant and laser beam propagation in an underdense collisional plasma are investigated, using the wave and dielectric function equations, for their dependence on the electron temperature. Simulation results show that, due to the influence of the ponderomotive force there is a nonlinear variation of electron temperature in an underdense collisional plasma, and this leads to a complicated and interesting nonlinear variation of dielectric constant; this nonlinear variation of dielectric constant directly affects the beam propagation and gives rise to laser beam self-focusing in some spatial-temporal regions; in particular, the beam width and the beam intensity present an oscillatory variation in the self-focusing region. The influence of several parameters on the dielectric function and beam self-focusing is discussed.
Ion-beam plasma and propagation of intense compensated ion beams
International Nuclear Information System (INIS)
Gabovich, M.D.
1977-01-01
Discussed are the results of investigation of plasma properties recieved by neutralization of intensive ion beam space charge. Considered is the process of ion beam compensation by charges, formed as a result of gas ionization by this beam or by externally introduced ones. Emphasis is placed on collective phenomena in ion-beam plasma, in particular on non-linear effects limiting amplitude of oscillations. It is shown, that not only dinamic decompensation but the Coulomb collisions of ions with electrons as well as other collective oscillations significantly affects the propagation of compensated ion beams. All the processes are to be taken into account at solving the problem of obtaining ''superdense'' compensated beams
Ion-beam plasma and propagation of intense compensated ion beams
Energy Technology Data Exchange (ETDEWEB)
Gabovich, M D [AN Ukrainskoj SSR, Kiev. Inst. Fiziki
1977-02-01
Discussed are the results of investigation of plasma properties received by neutralization of intense ion beam space charge. Considered is the process of ion beam compensation by charges, formed as a result of gas ionization by this beam or by externally introduced ones. Emphasis is placed on collective phenomena in ion-beam plasma, in particular on non-linear effects limiting amplitude of oscillations. It is shown that not only dynamic decompensation but the Coulomb collisions of ions with electrons as well as other collective oscillations significantly affects the propagation of compensated ion beams. All the processes are to be taken into account in solving the problem of obtaining ''superdense'' compensated beams.
Flame propagation in two-dimensional solids: Particle-resolved studies with complex plasmas
Yurchenko, S. O.; Yakovlev, E. V.; Couëdel, L.; Kryuchkov, N. P.; Lipaev, A. M.; Naumkin, V. N.; Kislov, A. Yu.; Ovcharov, P. V.; Zaytsev, K. I.; Vorob'ev, E. V.; Morfill, G. E.; Ivlev, A. V.
2017-10-01
Using two-dimensional (2D) complex plasmas as an experimental model system, particle-resolved studies of flame propagation in classical 2D solids are carried out. Combining experiments, theory, and molecular dynamics simulations, we demonstrate that the mode-coupling instability operating in 2D complex plasmas reveals all essential features of combustion, such as an activated heat release, two-zone structure of the self-similar temperature profile ("flame front"), as well as thermal expansion of the medium and temperature saturation behind the front. The presented results are of relevance for various fields ranging from combustion and thermochemistry, to chemical physics and synthesis of materials.
Excitation and propagation of modified fluctuation in a toroidal plasma in KT-5C device
International Nuclear Information System (INIS)
Sun Xuan; Wang Zhijiang; Lu Ronghua; Wen Yizhi; Wan Shude; Yu Changxuan; Liu Wandong; Wang Cheng; Pan Gesheng; Wang Wenhao; Wang Jun
2002-01-01
Understanding the propagation of the turbulent perturbation in the tokamak edge plasma is an important issue to actively modify or control the turbulence, reduce the anomalous transport and improve plasma confinement. To realize active modification of the edge perturbation, a high dynamic output, broad-band, low-cost power amplifier is set up, and used to drive the active probes in the experiments on KT-5C Tokamak. By using small-size magnetic probes together with Langmiur probes. It is observed that the modified perturbation by the active probes with sufficiently driving power may spread with electrostatic mode, and electromagnetic mode as well
International Nuclear Information System (INIS)
Nowak, S.; Orefice, A.
1994-01-01
In today's high frequency systems employed for plasma diagnostics, power heating, and current drive the behavior of the wave beams is appreciably affected by the self-diffraction phenomena due to their narrow collimation. In the present article the three-dimensional propagation of Gaussian beams in inhomogeneous and anisotropic media is analyzed, starting from a properly formulated dispersion relation. Particular attention is paid, in the case of electromagnetic electron cyclotron (EC) waves, to the toroidal geometry characterizing tokamak plasmas, to the power density evolution on the advancing wave fronts, and to the absorption features occurring when a beam crosses an EC resonant layer
Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.
Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H
2008-02-01
We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.
International Nuclear Information System (INIS)
Hafeez-Ur-Rehman; Mahmood, S.; Shah, Asif; Haque, Q.
2011-01-01
Two dimensional (2D) solitons are studied in a plasma system comprising of relativistically streaming ions, kappa distributed electrons, and positrons. Kadomtsev-Petviashvili (KP) equation is derived through the reductive perturbation technique. Analytical solution of the KP equation has been studied numerically and graphically. It is noticed that kappa parameters of electrons and positrons as well as the ions relativistic streaming factor have an emphatic influence on the structural as well as propagation characteristics of two dimensional solitons in the considered plasma system. Our results may be helpful in the understanding of soliton propagation in astrophysical and laboratory plasmas, specifically the interaction of pulsar relativistic wind with supernova ejecta and the transfer of energy to plasma by intense electric field of laser beams producing highly energetic superthermal and relativistic particles [L. Arons, Astrophys. Space Sci. Lib. 357, 373 (2009); P. Blasi and E. Amato, Astrophys. Space Sci. Proc. 2011, 623; and A. Shah and R. Saeed, Plasma Phys. Controlled Fusion 53, 095006 (2011)].
Hua, Weizhuo; Koji, Fukagata
2017-11-01
A numerical study has been conducted to understand the streamer formation and propagation of nanosecond pulsed surface dielectric barrier discharge of positive polarity. First we compared the result of different grid configuration to investigate the influence of x and y direction grid spacing on the streamer propagation. The streamer propagation is sensitive to y grid spacing especially at the dielectric surface. The streamer propagation velocity can reach 0.2 cm/ns when the voltage magnitude is 12 kV. A narrow gap was found between the streamer and dielectric barrier, where the plasma density is several orders of magnitude smaller than the streamer region. Analyses on the ion transport in the gap and streamer regions show the different ion transport mechanisms in the two different region. In the gap region, the diffusion of electron toward the dielectric layer decreases the seed electron in the beginning of voltage pulse, resulting that ionization avalanche does not occur. The streamer region is not significantly affected by the diffusion flux toward the dielectric layer, so that ionization avalanche takes place and leads to dramatic increase of plasma density.
International Nuclear Information System (INIS)
Akiyama, H.; Hayler, M.O.; Kristiansen, M.
1985-01-01
The dispersion relations for the compressional Alfven waves in a two-ion species plasma of deuterium and hydrogen are calculated for a configuration which includes a vacuum layer between the cylindrical plasma and the conducting wall. The presence of the vacuum layer strongly affects the propagation of the compressional Alfven wave, permitting some branches to propagate and penetrate the plasma column over most frequencies in the ion-cyclotron range. Basic Alfven-wave propagation and heating experiments in two-ion species consequently should be possible using tokamak and mirror devices with minor radii smaller than the Alfven wavelength
Excitation and propagation of the fast wave in a two component non uniform plasma
International Nuclear Information System (INIS)
Lapierre, Y.
1980-09-01
The purpose of this study is to compute the coupling of antennas in presence of plasma, and to derive the electric field distribution taking into account inhomogeneity in the magnetic field and in the density. The only calculations which have been down, up to now, were made under two kinds of assumptions: very low damping or very strong radial damping. Our calculation takes into account the mode conversion as it affects wave propagation. This might be of great importance for large machines
Study of ICRF wave propagation and plasma coupling efficiency in a linear magnetic mirror device
International Nuclear Information System (INIS)
Peng, S.Y.
1991-07-01
Ion Cyclotron Range of Frequency (ICRF) wave propagation in an inhomogeneous axial magnetic field in a cylindrical plasma-vacuum system has historically been inadequately modelled. Previous works either sacrifice the cylindrical geometry in favor of a simpler slab geometry, concentrate on the resonance region, use a single mode to represent the entire field structure, or examine only radial propagation. This thesis performs both analytical and computational studies to model the ICRF wave-plasma coupling and propagation problem. Experimental analysis is also conducted to compare experimental results with theoretical predictions. Both theoretical as well as experimental analysis are undertaken as part of the thesis. The theoretical studies simulate the propagation of ICRF waves in an axially inhomogeneous magnetic field and in cylindrical geometry. Two theoretical analysis are undertaken - an analytical study and a computational study. The analytical study treats the inhomogeneous magnetic field by transforming the (r,z) coordinate into another coordinate system (ρ,ξ) that allows the solution of the fields with much simpler boundaries. The plasma fields are then Fourier transformed into two coupled convolution-integral equations which are then differenced and solved for both the perpendicular mode number α as well as the complete EM fields. The computational study involves a multiple eigenmode computational analysis of the fields that exist within the plasma-vacuum system. The inhomogeneous axial field is treated by dividing the geometry into a series of transverse axial slices and using a constant dielectric tensor in each individual slice. The slices are then connected by longitudinal boundary conditions
Parametric instabilities of parallel propagating incoherent Alfven waves in a finite ion beta plasma
International Nuclear Information System (INIS)
Nariyuki, Y.; Hada, T.; Tsubouchi, K.
2007-01-01
Large amplitude, low-frequency Alfven waves constitute one of the most essential elements of magnetohydrodynamic (MHD) turbulence in the fast solar wind. Due to small collisionless dissipation rates, the waves can propagate long distances and efficiently convey such macroscopic quantities as momentum, energy, and helicity. Since loading of such quantities is completed when the waves damp away, it is important to examine how the waves can dissipate in the solar wind. Among various possible dissipation processes of the Alfven waves, parametric instabilities have been believed to be important. In this paper, we numerically discuss the parametric instabilities of coherent/incoherent Alfven waves in a finite ion beta plasma using a one-dimensional hybrid (superparticle ions plus an electron massless fluid) simulation, in order to explain local production of sunward propagating Alfven waves, as suggested by Helios/Ulysses observation results. Parameter studies clarify the dependence of parametric instabilities of coherent/incoherent Alfven waves on the ion and electron beta ratio. Parametric instabilities of coherent Alfven waves in a finite ion beta plasma are vastly different from those in the cold ions (i.e., MHD and/or Hall-MHD systems), even if the collisionless damping of the Alfven waves are neglected. Further, ''nonlinearly driven'' modulational instability is important for the dissipation of incoherent Alfven waves in a finite ion beta plasma regardless of their polarization, since the ion kinetic effects let both the right-hand and left-hand polarized waves become unstable to the modulational instability. The present results suggest that, although the antisunward propagating dispersive Alfven waves are efficiently dissipated through the parametric instabilities in a finite ion beta plasma, these instabilities hardly produce the sunward propagating waves
Surface wave propagation in an ideal Hall-magnetohydrodynamic plasma jet in flowing environment
International Nuclear Information System (INIS)
Sikka, Himanshu; Kumar, Nagendra; Zhelyazkov, Ivan
2004-01-01
The behavior of the Hall-magnetohydrodynamic (Hall-MHD) sausage and kink waves is studied in the presence of steady flow. The influence of the flow both inside and outside the plasma slab is taken into account. The plasma in the environment is considered to be cold and moves with the different flow velocity outside the slab. In the limit of parallel propagation, dispersion relation is derived to discuss the propagation of both the modes. Numerical results for the propagation characteristics are obtained for different Alfvenic Mach number ratios inside and outside the slab. It is found that the dispersion curves for both surface modes, namely, the sausage and kink ones in cold plasma show complexities in their behavior in terms of multivalued portions of the curves. These multivalued portions correspond to the different normalized phase velocities for the same value of Alfvenic Mach number. In contrast to the conventional MHD surface waves which are assumed to be pure surface waves or pseudosurface waves, surface waves are obtained which are bulk waves for very small dimensionless wave numbers, then turn to leaky waves and finally transform to pure surface waves for values of dimensionless wave number greater than one
Preliminary considerations concerning neutral plasma beam propagation across a magnetic field
International Nuclear Information System (INIS)
Shanahan, W.R.; Faehl, R.J.; Godfrey, B.B.
1979-08-01
A plan to address physical questions of interest for exoatmospheric military applications of intense neutralized plasma beams is described. After a brief review of earlier work relevant to this matter and a detailed explanation of why such work cannot answer questions of present interest, a plan employing interactive application of several numerical and analytic techniques to treat relevant phenomena occurring on the various rather disparate time and length scales involved is suggested. The first part of the study would determine the macroscopic features of beam propagation through calculations effected with a magnetohydrodynamical numerical code. Classical transport coefficients would be employed in this initial phase. Using information thus gained concerning gross charge and current distributions, particle-in-cell simulations would be initialized to study those microscopic, phase-space-dependent phenomena which can alter the phenomonological transport coefficients appearing in the fluid description. Insight thereby gained concerning anomaous, collectively induced transport effects would then be applied to yield a refined, accurate description of the macroscopic aspects of neutral plasma beam propagation. Personnel and computational resources available at the Los Alamos Scientific Laboratory are described. Results of a very preliminary particle-in-cell simulation of a neutral plasma beam propagating across a magnetic field are presented
Generation and Micro-scale Effects of Electrostatic Waves in an Oblique Shock
Goodrich, K.; Ergun, R.; Schwartz, S. J.; Newman, D.; Johlander, A.; Argall, M. R.; Wilder, F. D.; Torbert, R. B.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Strangeway, R. J.; Russell, C. T.; Giles, B. L.; Gershman, D. J.; Burch, J. L.
2017-12-01
We present an analysis of large amplitude (>100 mV/m), high frequency (≤1 kHz), electrostatic waves observed by MMS during an oblique bow shock crossing event. The observed waves primarily consist of electrostatic solitary waves (ESWs) and oblique ion plasma waves (IPWs). ESWs typically include nonlinear structures such as double layers, ion phase-space holes, and electron phase-space holes. Oblique IPWs are observed to be similar to ion acoustic waves, but can propagate up to 70° from the ambient magnetic field direction. Both wave-modes, particularly IPWs, are observed to have very short wavelengths ( 100 m) and are highly localized. While such wave-modes have been previously observed in the terrestrial bow shock, instrumental constraints have limited detailed insight into their generation and their effect on their plasma shock environment. Analysis of this oblique shock event shows evidence that ESWs and oblique IPWs can be generated through field-aligned currents associated with magnetic turbulence and through a counterstreaming ion instability respectively. We also present evidence that this wave activity can facilitate momentum exchange between ion populations, resulting in deceleration of incoming solar wind, and localized electron heating.
Propagation Characteristics of High-Power Vortex Laguerre-Gaussian Laser Beams in Plasma
Directory of Open Access Journals (Sweden)
Zhili Lin
2018-04-01
Full Text Available The propagation characteristics of high-power laser beams in plasma is an important research topic and has many potential applications in fields such as laser machining, laser-driven accelerators and laser-driven inertial confined fusion. The dynamic evolution of high-power Laguerre-Gaussian (LG beams in plasma is numerically investigated by using the finite-difference time-domain (FDTD method based on the nonlinear Drude model, with both plasma frequency and collision frequency modulated by the light intensity of laser beam. The numerical algorithms and implementation techniques of FDTD method are presented for numerically simulating the nonlinear permittivity model of plasma and generating the LG beams with predefined parameters. The simulation results show that the plasma has different field modulation effects on the two exemplified LG beams with different cross-sectional patterns. The self-focusing and stochastic absorption phenomena of high-power laser beam in plasma are also demonstrated. This research also provides a new means for the field modulation of laser beams by plasma.
International Nuclear Information System (INIS)
Lazar, M.; Schlickeiser, R.
2006-01-01
The properties of transverse waves parallel propagating in magnetized plasmas with arbitrary composition and thermally anisotropic, are investigated on the basis of relativistic Vlasov-Maxwell equations. The transverse dispersion relations for plasmas with arbitrary distribution functions are derived. These dispersion relations describe the linear response of the system to the initial perturbations and thus define all existing linear (transverse) plasma modes in the system. By analytic continuation the dispersion relations in the whole complex frequency plane are constructed. Further analysis is restricted to the important case of anisotropic bi-Maxwellian equilibrium plasma distribution functions. Explicit forms of the relativistically correct transverse dispersion relations are derived that hold for any values of the plasma temperatures and the temperature anisotropy. In the limit of nonrelativistic plasma temperatures the dispersion relations are expressed in terms of plasma dispersion function, however, the dependence on frequency and wave numbers is markedly different from the standard noncovariant nonrelativistic analysis. Only in the strictly unphysical formal limit of an infinitely large speed of light, c→∞, does the nonrelativistic dispersion relations reduce to the standard noncovariant dispersion relations
Xiao, W W; Evans, T E; Tynan, G R; Yoon, S W; Jeon, Y M; Ko, W H; Nam, Y U; Oh, Y K
2017-11-17
The propagation dynamics of resonant magnetic perturbation fields in KSTAR H-mode plasmas with injection of small edge perturbations produced by a supersonic molecular beam injection is reported for the first time. The results show that the perturbation field first excites a plasma response on the q=3 magnetic surface and then propagates inward to the q=2 surface with a radially averaged propagation velocity of resonant magnetic perturbations field equal to 32.5 m/ s. As a result, the perturbation field brakes the toroidal rotation on the q=3 surface first causing a momentum transport perturbation that propagates both inward and outward. A higher density fluctuation level is observed. The propagation velocity of the resonant magnetic perturbations field is larger than the radial propagation velocity of the perturbation in the toroidal rotation.
Control of radial propagation and polarity in a plasma jet in surrounding Ar
Gong, W.
2018-01-08
In recent years, the use of shielding gas to prevent the diffusion of the ambient air, particularly oxygen and nitrogen species, into the effluent of the atmospheric pressure plasma jet, and thus control the nature of chemical species used in the plasma treatment has increased. In this paper, the radial propagation of a plasma jet in ambient Ar is examined to find the key determinants of the polarity of plasma jets. The dynamics of the discharge reveal that the radial diffusion discharge is a special phenomenon observed only at the falling edge of the pulses. The radial transport of electrons, which is driven by the radial component of the applied electric field at the falling edge of the pulse, is shown to play an important role in increasing the seed electron density in the surrounding Ar. This result suggests a method to provide seed electrons at atmospheric pressure with a negative discharge. The polarity of the plasma jet is found to be determined by the pulse width rather than the polarity of the applied voltage, as it dictates the relative difference in the intensity of the two discharges in a single pulse, where the stronger discharge in a pulse dominates the behavior of the plasma jet. Accordingly, a method to control the polarity of a plasma jet through varying the pulse width is developed. Since plasma jets of different polarities differ remarkably in terms of their characteristics, the method to control the polarity reported in this paper will be of use for such applications as plasma-enhanced processing of materials and plasma biomedicine.
Control of radial propagation and polarity in a plasma jet in surrounding Ar
Gong, W.; Yue, Y.; Ma, F.; Yu, F.; Wan, J.; Nie, L.; Bazaka, K.; Xian, Y.; Lu, X.; Ostrikov, K.
2018-01-01
In recent years, the use of shielding gas to prevent the diffusion of the ambient air, particularly oxygen and nitrogen species, into the effluent of the atmospheric pressure plasma jet, and thus control the nature of chemical species used in the plasma treatment has increased. In this paper, the radial propagation of a plasma jet in ambient Ar is examined to find the key determinants of the polarity of plasma jets. The dynamics of the discharge reveal that the radial diffusion discharge is a special phenomenon observed only at the falling edge of the pulses. The radial transport of electrons, which is driven by the radial component of the applied electric field at the falling edge of the pulse, is shown to play an important role in increasing the seed electron density in the surrounding Ar. This result suggests a method to provide seed electrons at atmospheric pressure with a negative discharge. The polarity of the plasma jet is found to be determined by the pulse width rather than the polarity of the applied voltage, as it dictates the relative difference in the intensity of the two discharges in a single pulse, where the stronger discharge in a pulse dominates the behavior of the plasma jet. Accordingly, a method to control the polarity of a plasma jet through varying the pulse width is developed. Since plasma jets of different polarities differ remarkably in terms of their characteristics, the method to control the polarity reported in this paper will be of use for such applications as plasma-enhanced processing of materials and plasma biomedicine.
Propagation and damping of mode converted ion-Bernstein waves in toroidal plasmas
International Nuclear Information System (INIS)
Ram, A.K.; Bers, A.
1991-01-01
In the heating of tokamak plasmas by waves in the ion-cyclotron range of frequencies, the fast Alfven waves launched at the plasma edge can mode convert to the ion-Bernstein waves (IBW). The propagation and damping of these mode converted waves was studied using a ray tracing code that follows the fast phase and the amplitude of the electromagnetic field along the IBW ray trajectories in a toroidal plasma. A simple analytical model is developed that describes the numerically observed features of propagation and damping of the IBW's. It is found that along the ray trajectory of the IBW there is an upshift of the poloidal mode numbers, which can lead to the electron Landau damping of the wave. This damping is dependent on the strength of the toroidal plasma current. From the properties of the upshift of the poloidal mode numbers, it is concluded that the mode converted ion-Bernstein waves are not suitable candidates for electron current drive
Intense microwave pulse propagation through gas breakdown plasmas in a waveguide
International Nuclear Information System (INIS)
Byrne, D.P.
1986-01-01
High-power microwave pulse-compression techniques are used to generate 2.856 GHz pulses which are propagated in a TE 10 mode through a gas filled section of waveguide, where the pulses interact with self-generated gas-breakdown plasmas. Pulse envelopes transmitted through the plasmas, with duration varying from 2 ns to greater than 1 μs, and peak powers of a few kW to nearly 100 MW, are measured as a function of incident pulse and gas pressure for air, nitrogen, and helium. In addition, the spatial and temporal development of the optical radiation emitted by the breakdown plasmas are measured. For transmitted pulse durations ≥ 100 ns, good agreement is found with both theory and existing measurements. For transmitted pulse duration as short as 2 ns (less than 10 rf cycles), a two-dimensional model is used in which the electrons in the plasma are treated as a fluid whose interactions with the microwave pulse are governed by a self-consistent set of fluid equations and Maxwell's equations for the electromagnetic field. The predictions of this model for air are compared with the experimental results over a pressure range of 0.8 torr to 300 torr. Good agreement is obtained above about 1 torr pressure, demonstrating that microwave pulse propagation above the breakdown threshold can be accurately modeled on this time scale. 63 refs., 44 figs., 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Lee, Myoung-Jae [Department of Physics, Hanyang University, Seoul 04763 (Korea, Republic of); Research Institute for Natural Sciences, Hanyang University, Seoul 04763 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588 (Korea, Republic of); Department of Electrical and Computer Engineering, MC 0407, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0407 (United States)
2017-02-12
High frequency electrostatic wave propagation in a dense and semi-bounded electron quantum plasma is investigated with consideration of the Bohm potential. The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. We found that the quantum effect enhances the frequency of the wave especially in the high wave number regime. However, the frequency of surface wave is found to be always lower than that of the bulk wave for the same quantum wave number. The group velocity of the surface wave for various quantum wave number is also obtained. - Highlights: • High frequency electrostatic wave propagation is investigated in a dense semi-bounded quantum plasma. • The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. • The quantum effect enhances the frequency of the wave especially in the high wave number regime. • The frequency of surface wave is found to be always lower than that of the bulk wave. • The group velocity of the surface wave for various quantum wave number is also obtained.
International Nuclear Information System (INIS)
Kopainsky, J.
1975-01-01
In weakly ionized plasmas the scattering of electromagnetic waves on free electrons (Thompson scattering) can be neglected as compared with the scattering on bound electrons (Rayleigh scattering). If the scattering process can be described by a fluid dynamical model it is caused by sound waves which are generated or annihilated by the incident electromagnetic wave. The propagation of sound waves results in a shift of the scattered line whereas their absorption within the plasma produces the broadening of the scattered line. The theory of propagation of sound in weakly ionized plasmas is developed and extended to Rayleigh scattering. The results are applied to laser scattering in a weakly ionized hydrogen plasma. (Auth.)
Turbulence simulations of blob formation and radial propagation in toroidally magnetized plasmas
DEFF Research Database (Denmark)
Garcia, O.E.; Naulin, V.; Nielsen, A.H.
2006-01-01
the presence of long- range correlations in the particle density fluctuations. Finally, conditional statistics of the particle flux demonstrates the intermittency of the turbulent plasma transport and the quasi-periodic apparency of blob structures due to bursting in the global turbulence level....... of particles and heat, which is coupled to a scrape-off layer with linear damping terms for all dependent variables corresponding to transport along open magnetic field lines. The formation of blob structures is related to profile variations caused by bursting in the global turbulence level, which is due...... to a dynamical regulation by self- sustained differential rotation of the plasma layer. Radial propagation of the blob structures follows from a vertical charge polarization due to magnetic guiding centre drifts in the toroidally magnetized plasma. Statistical analysis of the particle density, radial electric...
Ideal laser-beam propagation through high-temperature ignition Hohlraum plasmas.
Froula, D H; Divol, L; Meezan, N B; Dixit, S; Moody, J D; Neumayer, P; Pollock, B B; Ross, J S; Glenzer, S H
2007-02-23
We demonstrate that a blue (3omega, 351 nm) laser beam with an intensity of 2 x 10(15) W cm(-2) propagates nearly within the original beam cone through a millimeter scale, T(e)=3.5 keV high density (n(e)=5 x 10(20) cm(-3)) plasma. The beam produced less than 1% total backscatter at these high temperatures and densities; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds.
Subwavelength image manipulation through oblique and herringbone layered acoustic systems
International Nuclear Information System (INIS)
Li, Chunhui; Jia, Han; Ke, Manzhu; Li, Yixiang; Liu, Zhengyou
2014-01-01
In this paper, an oblique and a herringbone layered acoustic structure are experimentally and theoretically demonstrated to manipulate acoustic subwavelength images. An imaging resolution of less than one tenth of a wavelength is achieved with both optimized systems, and lateral image shift has been realized by an oblique layered system. The thicknesses of both the oblique and the herringbone layered acoustic systems are largely reduced through utilizing the oblique or herringbone wave propagation path instead of the vertical wave propagation path in the rectangular layered planar acoustic system. With smaller size and subwavelength image manipulation, the acoustic systems are more favourable for practical application. (paper)
Ionospheric heating with oblique high-frequency waves
International Nuclear Information System (INIS)
Field, E.C. Jr.; Bloom, R.M.; Kossey, P.A.
1990-01-01
This paper presents calculations of ionospheric electron temperature and density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) radio waves. The analysis takes into account focusing at caustics, the consequent Joule heating of the surrounding plasma, heat conduction, diffusion, and recombination processes, these being the effects of a powerful oblique modifying wave. It neglects whatever plasma instabilities might occur. The authors then seek effects on a secondary test wave that is propagated along the same path as the first. The calculations predict ground-level field strength reductions of several decibels in the test wave for modifying waves having effective radiated power (ERP) in the 85- to 90-dBW range. These field strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. The location of the signal change is sensitive to the frequency and the model ionosphere assumed; so future experiments should employ the widest possible range of frequencies and propagation conditions. An ERP of 90 dBW seems to be a sort of threshold that, if exceeded, might result in substantial rather than small signal changes. The conclusions are based solely on Joule heating and subsequent refraction of waves passing through caustic regions
On the propagation of hydromagnetic waves in a plasma of thermal and suprathermal components
Kumar, Nagendra; Sikka, Himanshu
2007-12-01
The propagation of MHD waves is studied when two ideal fluids, thermal and suprathermal gases, coupled by magnetic field are moving with the steady flow velocity. The fluids move independently in a direction perpendicular to the magnetic field but gets coupled along the field. Due to the presence of flow in suprathermal and thermal fluids there appears forward and backward waves. All the forward and backward modes propagate in such a way that their rate of change of phase speed with the thermal Mach number is same. It is also found that besides the usual hydromagnetic modes there appears a suprathermal mode which propagates with faster speed. Surface waves are also examined on an interface formed with composite plasma (suprathermal and thermal gases) on one side and the other is a non-magnetized plasma. In this case, the modes obtained are two or three depending on whether the sound velocity in thermal gas is equal to or greater than the sound velocity in suprathermal gas. The results lead to the conclusion that the interaction of thermal and suprathermal components may lead to the occurrence of an additional mode called suprathermal mode whose phase velocity is higher than all the other modes.
International Nuclear Information System (INIS)
Singh, Nagendra; Hwang, K.S.
1988-01-01
The propagation of electron beams injected from a spacecraft into an ambient plasma and the associated potential structures are investigated by one-dimensional Vlasov simulations. For moderate beams, for which the time average spacecraft potential (Φ sa ) lies in the range T e much-lt eΦ sa approx-lt W B , where T e is the electron temperature in energy units and W B is the average beam energy, a double layer forms near the beam head which propagates into the ambient plasma much more slowly than the initial beam velocity. The double layer formation is being reported for the first time. For weak beams, for which |eΦ sa | approx-lt T e , the beam propagates with the initial beam velocity, and no double layer formation occurs. On the other hand, for strong beams for which eΦ sa > W B , the bulk of the beam is returned to the spacecraft, and the main feature of the potential structure is a sheath formation with an intense electric field limited to distances d near the spacecraft surface. These features of the potential structures are compared with those seen in laboratory and space experiments on electron beam injections
Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment
Energy Technology Data Exchange (ETDEWEB)
Joulaei, A. [Max-Planck Institute for Physics, Munich (Germany); University of Mazandaran (Iran, Islamic Republic of); Moody, J. [Max-Planck Institute for Physics, Munich (Germany); Berti, N.; Kasparian, J. [University of Geneva (Switzerland); Mirzanejhad, S. [University of Mazandaran (Iran, Islamic Republic of); Muggli, P. [Max-Planck Institute for Physics, Munich (Germany)
2016-09-01
We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment. - Highlights: • Discussion the AWAKE plasma source based on photoionization of rubidium vapor with a TW/cm^2 Intensity laser with a spectrum across valence ground state transition resonances. • Examines the propagation of the AWAKE ionization laser through rubidium vapor at design density on a small scale and reduced intensity with a linear numerical model compared to experimental results. • Discusses physics of pulse propagation through the vapor at high intensity regime where strong ionization occurs within the laser pulse.
International Nuclear Information System (INIS)
Valeo, E.J.; Phillips, C.K.; Bonoli, P.T.; Wright, J.C.; Brambilla, M.
2007-01-01
The generation of energetic tails in the electron distribution function is intrinsic to lower-hybrid (LH) heating and current drive in weakly collisional magnetically confined plasma. The effects of these deformations on the RF deposition profile have previously been examined within the ray approximation. Recently, the calculation of full-wave propagation of LH waves in a thermal plasma has been accomplished using an adaptation of the TORIC code. Here, initial results are presented from TORIC simulations of LH propagation in a toroidal plasma with non-thermal electrons. The required efficient computation of the hot plasma dielectric tensor is accomplished using a technique previously demonstrated in full-wave simulations of ICRF propagation in plasma with non-thermal ions
Free-electron laser with a plasma wave wiggler propagating through a magnetized plasma channel
International Nuclear Information System (INIS)
Jafari, S; Jafarinia, F; Mehdian, H
2013-01-01
A plasma eigenmode has been employed as a wiggler in a magnetized plasma channel for the generation of laser radiation in a free-electron laser. The short wavelength of the plasma wave allows a higher radiation frequency to be obtained than from conventional wiggler free-electron lasers. The plasma can significantly slow down the radiation mode, thereby relaxing the beam energy requirement considerably. In addition, it allows a beam current in excess of the vacuum current limit via charge neutralization. This configuration has a higher tunability by controlling the plasma density in addition to the γ-tunability of the standard FEL. The laser gain has been calculated and numerical computations of the electron trajectories and gain are presented. Four groups (I–IV) of electron orbits have been found. It has been shown that by increasing the cyclotron frequency, the gain for orbits of group I and group III increases, while a decrease in gain has been obtained for orbits of group II and group IV. Similarly, the effect of plasma density on gain has been exhibited. The results indicate that with increasing plasma density, the orbits of all groups shift to higher cyclotron frequencies. The effects of beam self-fields on gain have also been demonstrated. It has been found that in the presence of beam self-fields the sensitivity of the gain increases substantially in the vicinity of gyroresonance. Here, the gain enhancement and reduction are due to the paramagnetic and diamagnetic effects of the self-magnetic field, respectively. (paper)
Urunkar, T. U.; Valkunde, A. T.; Vhanmore, B. D.; Gavade, K. M.; Patil, S. D.; Takale, M. V.
2018-05-01
It is quite known that critical power of the laser plays vital role in the propagation of Gaussian laser beam in collisionless plasma. The nonlinearity in dielectric constant considered herein is due to the ponderomotive force. In the present analysis, the interval of critical beam power has been explored to sustain the competition between diffraction and self-focusing of Gaussian laser beam during propagation in collisionless magnetized plasma. Differential equation for beam-width parameter has been established by using WKB and paraxial approximations under parabolic equation approach. The effect of critical power on the propagation of Gaussian laser beam has been presented graphically and discussed.
Attenuation Effects of Plasma on Ka-Band Wave Propagation in Various Gas and Pressure Environments
Directory of Open Access Journals (Sweden)
Joo Hwan Lee
2018-01-01
Full Text Available This work demonstrates attenuation effects of plasma on waves propagating in the 26.5–40 GHz range. The effect is investigated via experiments measuring the transmission between two Ka-band horn antennas set 30 cm apart. A dielectric-barrier-discharge (DBD plasma generator with a size of 200 mm × 100 mm × 70 mm and consisting of 20 layers of electrodes is placed between the two antennas. The DBD generator is placed in a 400 mm × 300 mm × 400 mm acrylic chamber so that the experiments can be performed for plasma generated under various conditions of gas and pressure, for instance, in air, Ar, and He environments at 0.001, 0.05, and 1 atm of pressure. Attenuation is calculated by the difference in the transmission level, with and without plasma, which is generated with a bias voltage of 20 kV in the 0.1–1.4 kHz range. Results show that the attenuation varies from 0.05 dB/m to 9.0 dB/m depending on the environment. Noble gas environments show higher levels of attenuation than air, and He is lossier than Ar. In all gas environments, attenuation increases as pressure increases. Finally, electromagnetic models of plasmas generated in various conditions are provided.
Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow
International Nuclear Information System (INIS)
Pinchuk, M; Kurakina, N; Spodobin, V; Stepanova, O
2017-01-01
The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow. (paper)
Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow
Pinchuk, M.; Stepanova, O.; Kurakina, N.; Spodobin, V.
2017-05-01
The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow.
Directory of Open Access Journals (Sweden)
Bogdan Butoi
2017-12-01
Full Text Available This work is focused on the structural and morphological investigations of polyaniline and poly(o-anisidine polymers generated in a direct current glow discharge plasma, in the vapors of the monomers, without a buffer gas, using an oblique angle-positioned substrate configuration. By atomic force microscopy and scanning electron microscopy we identified the formation of worm-like interlinked structures on the surface of the polyaniline layers, the layers being compact in the bulk. The poly(o-anisidine layers are flat with no kind of structures on their surfaces. By Fourier transform infrared spectroscopy we identified the main IR bands characteristic of polyaniline and poly(o-anisidine, confirming that the polyaniline chemical structure is in the emeraldine form. The IR band from 1070 cm−1 was attributed to the emeraldine salt form of polyaniline as an indication of its doping with H+. The appearance of the IR band at 1155 cm−1 also indicates the conducting protonated of polyaniline. The X-ray diffraction revealed the formation of crystalline domains embedded in an amorphous matrix within the polyaniline layers. The interchain separation length of 3.59 Å is also an indicator of the conductive character of the polymers. The X-ray diffraction pattern of poly(o-anisidine highlights the semi-crystalline nature of the layers. The electrical conductivities of polyaniline and poly(o-anisidine layers and their dependence with temperature are also investigated.
Simulation of laser propagation in a plasma with a frequency wave equation
International Nuclear Information System (INIS)
Desroziers, S.; Nataf, F.; Sentis, R.
2008-01-01
The aim of this work is to perform numerical simulations of the propagation of a laser in a plasma. At each time step, one has to solve a Helmholtz equation in a domain which consists in some hundreds of millions of cells. To solve this huge linear system, we use an iterative Krylov method preconditioned by a separable matrix. The corresponding linear system is solved with a block cyclic reduction method. Some enlightenments on the parallel implementation are also given. Lastly, numerical results are presented including some features concerning the scalability of the numerical method on a parallel architecture. (authors)
Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment
Joulaei, Atefeh; Berti, Nicolas; Kasparian, Jerome; Mirzanejhad, Saeed; Muggli, Patric
2016-01-01
We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment.
Pure air-plasma bullets propagating inside microcapillaries and in ambient air
Lacoste, Deanna; Bourdon, Anne; Kuribara, Koichi; Urabe, Keiichiro; Stauss, Sven; Terashima, Kazuo
2014-01-01
This paper reports on the characterization of air-plasma bullets in microcapillary tubes and in ambient air, obtained without the use of inert or noble gases. The bullets were produced by nanosecond repetitively pulsed discharges, applied in a dielectric barrier discharge configuration. The anode was a tungsten wire with a diameter of 50 μm, centered in the microcapillary, while the cathode was a silver ring, fixed on the outer surface of the fused silica tube. The effects of the applied voltage and the inner diameter of the microcapillary tube on the plasma behavior were investigated. Inside the tubes, while the topology of the bullets seems to be strongly dependent on the diameter, their velocity is only a function of the amplitude of the applied voltage. In ambient air, the propagation of air bullets with a velocity of about 1.25 ×105 m s-1 is observed.
Nonlinear propagation of intense electromagnetic waves in weakly-ionized plasmas
International Nuclear Information System (INIS)
Shukla, P.K.
1993-01-01
The nonlinear propagation of intense electromagnetic waves in weakly-ionized plasmas is considered. Stimulated scattering mechanisms involving electromagnetic and acoustic waves in an unmagnetized plasma are investigated. The growth rate and threshold for three-wave decay interactions as well as modulational and filamentation instabilities are presented. Furthermore, the electromagnetic wave modulation theory is generalized for weakly ionized collisional magnetoplasmas. Here, the radiation envelope is generally governed by a nonlinear Schroedinger equation. Accounting for the dependence of the attachment frequency on the radiation intensity, ponderomotive force, as well as the differential Joule heating nonlinearity, the authors derive the equations for the nonthermal electron density and temperature perturbations. The various nonlinear terms in the electron motion are compared. The problems of self-focusing and wave localization are discussed. The relevance of the investigation to ionospheric modification by powerful electromagnetic waves is pointed out
Pure air-plasma bullets propagating inside microcapillaries and in ambient air
Lacoste, Deanna
2014-11-04
This paper reports on the characterization of air-plasma bullets in microcapillary tubes and in ambient air, obtained without the use of inert or noble gases. The bullets were produced by nanosecond repetitively pulsed discharges, applied in a dielectric barrier discharge configuration. The anode was a tungsten wire with a diameter of 50 μm, centered in the microcapillary, while the cathode was a silver ring, fixed on the outer surface of the fused silica tube. The effects of the applied voltage and the inner diameter of the microcapillary tube on the plasma behavior were investigated. Inside the tubes, while the topology of the bullets seems to be strongly dependent on the diameter, their velocity is only a function of the amplitude of the applied voltage. In ambient air, the propagation of air bullets with a velocity of about 1.25 ×105 m s-1 is observed.
Electron Acceleration and the Propagation of Ultrashort High-Intensity Laser Pulses in Plasmas
International Nuclear Information System (INIS)
Wang, Xiaofang; Krishnan, Mohan; Saleh, Ned; Wang, Haiwen; Umstadter, Donald
2000-01-01
Reported are interactions of high-intensity laser pulses (λ=810 nm and I≤3x10 18 W /cm 2 ) with plasmas in a new parameter regime, in which the pulse duration (τ=29 fs ) corresponds to 0.6-2.6 plasma periods. Relativistic filamentation is observed to cause laser-beam breakup and scattering of the beam out of the vacuum propagation angle. A beam of megaelectronvolt electrons with divergence angle as small as 1 degree sign is generated in the forward direction, which is correlated to the growth of the relativistic filamentation. Raman scattering, however, is found to be much less than previous long-pulse results. (c) 2000 The American Physical Society
Propagation of a surface electromagnetic wave in a plasma with allowance for electron heating
International Nuclear Information System (INIS)
Boev, A.G.; Prokopov, A.V.
1978-01-01
Considered is propagation of a surface high-frequency wave in a semibounded plasma, which electron component is heated within the wave field. Dissipative effects are considered small, that is possible if wave frequency is much higher than the collision frequency and phase velocity of wave considerably exceeds electron heat velocity. Under conditions of anomalous skin-effect the distributions of electron temperature and wave damping have been found. It is established, that higher electron temperature on the boundary results in a higher decrease of temperature inside a plasma, far from the boundary temperature decreases exponentially; damping coefficient under anomalous skin-effect conditions is characterized by a stronger dependence not only on the wave amplitude, but as well as on gas pressure and wave frequency in comparison with normal conditions
Manning, Robert M.
2009-01-01
Based on a theoretical model of the propagation of electromagnetic waves through a hypersonically induced plasma, it has been demonstrated that the classical radiofrequency communications blackout that is experienced during atmospheric reentry can be mitigated through the appropriate control of an external magnetic field of nominal magnitude. The model is based on the kinetic equation treatment of Vlasov and involves an analytical solution for the electric and magnetic fields within the plasma allowing for a description of the attendant transmission, reflection and absorption coefficients. The ability to transmit through the magnetized plasma is due to the magnetic windows that are created within the plasma via the well-known whistler modes of propagation. The case of 2 GHz transmission through a re-entry plasma is considered. The coefficients are found to be highly sensitive to the prevailing electron density and will thus require a dynamic control mechanism to vary the magnetic field as the plasma evolves through the re-entry phase.
The effect of target materials on the propagation of atmospheric-pressure plasma jets
Ji, Longfei; Yan, Wen; Xia, Yang; Liu, Dongping
2018-05-01
The current study is focused on the effect of target materials (quartz plate, copper sheet, and quartz plate with a grounded copper sheet on the back) on the propagation of atmospheric-pressure helium plasma jets. The dynamics of ionization waves (IWs) and the relative amount of reactive oxygen species (OH and O) in the IW front were compared by using spatial and temporal images and relative optical emission spectroscopy. Our measurements show that the targets can significantly affect the propagation and intensity of the IWs. In addition, strong OH emission lines were detected when the IWs impinged upon the damp surface. Numerical simulations have been carried out to explain the experimental observation. The propagation velocity of IWs predicted by the simulation was in good agreement with the experimental results. Simulation results suggest that the density and velocity of IWs mainly depend on the electric field between the high voltage electrode tip and the target. Analysis indicates that the targets could change the electric field distribution between the high voltage electrode and targets and thus affect the dynamics and the density of the IWs, the generation of reactive oxygen species, and the corresponding sterilization efficiency.
Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas
International Nuclear Information System (INIS)
Banerjee, A.K.; Alam, M.N.; Mamun, A.A.
2001-01-01
Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust- magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfven mode these effects play no role, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role. (author)
Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas
International Nuclear Information System (INIS)
Mamun, A.A.
1999-07-01
Obliquely propagating ultra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfven mode propagating parallel to the external magnetic field and dust-magnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that these effects of self-gravitational field and dust/ion fluid temperature play no role in parallel propagating dust-Alfven mode, but in obliquely propagating dust-Alfven mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays a destabilizing role whereas the effect of dust/ion fluid temperature plays a stabilizing role. (author)
Theory and Modeling of Petawatt Laser Pulse Propagation in Low Density Plasmas
International Nuclear Information System (INIS)
Shadwick, Bradley A.; Kalmykov, S. Y.
2016-01-01
Report describing accomplishments in all-optical control of self-injection in laser-plasma accelerators and in developing advanced numerical models of laser-plasma interactions. All-optical approaches to controlling electron self-injection and beam formation in laser-plasma accelerators (LPAs) were explored. It was demonstrated that control over the laser pulse evolution is the key ingredient in the generation of low-background, low-phase-space-volume electron beams. To this end, preserving a smooth laser pulse envelope throughout the acceleration process can be achieved through tuning the phase and amplitude of the incident pulse. A negative frequency chirp compensates the frequency red-shift accumulated due to wake excitation, preventing evolution of the pulse into a relativistic optical shock. This reduces the ponderomotive force exerted on quiescent plasma electrons, suppressing expansion of the bubble and continuous injection of background electrons, thereby reducing the charge in the low-energy tail by an order of magnitude. Slowly raising the density in the pulse propagation direction locks electrons in the accelerating phase, boosting their energy, keeping continuous injection at a low level, tripling the brightness of the quasi-monoenergetic component. Additionally, propagating the negatively chirped pulse in a plasma channel suppresses diffraction of the pulse leading edge, further reducing continuous injection. As a side effect, oscillations of the pulse tail may be enhanced, leading to production of low-background, polychromatic electron beams. Such beams, consisting of quasi-monoenergetic components with controllable energy and energy separation, may be useful as drivers of polychromatic x-rays based on Thomson backscattering. These all-optical methods of electron beam quality control are critically important for the development of future compact, high-repetition-rate, GeV-scale LPA using 10 TW-class, ultra-high bandwidth pulses and mm-scale, dense
Theory and Modeling of Petawatt Laser Pulse Propagation in Low Density Plasmas
Energy Technology Data Exchange (ETDEWEB)
Shadwick, Bradley A. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy; Kalmykov, S. Y. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy
2016-12-08
Report describing accomplishments in all-optical control of self-injection in laser-plasma accelerators and in developing advanced numerical models of laser-plasma interactions. All-optical approaches to controlling electron self-injection and beam formation in laser-plasma accelerators (LPAs) were explored. It was demonstrated that control over the laser pulse evolution is the key ingredient in the generation of low-background, low-phase-space-volume electron beams. To this end, preserving a smooth laser pulse envelope throughout the acceleration process can be achieved through tuning the phase and amplitude of the incident pulse. A negative frequency chirp compensates the frequency red-shift accumulated due to wake excitation, preventing evolution of the pulse into a relativistic optical shock. This reduces the ponderomotive force exerted on quiescent plasma electrons, suppressing expansion of the bubble and continuous injection of background electrons, thereby reducing the charge in the low-energy tail by an order of magnitude. Slowly raising the density in the pulse propagation direction locks electrons in the accelerating phase, boosting their energy, keeping continuous injection at a low level, tripling the brightness of the quasi-monoenergetic component. Additionally, propagating the negatively chirped pulse in a plasma channel suppresses diffraction of the pulse leading edge, further reducing continuous injection. As a side effect, oscillations of the pulse tail may be enhanced, leading to production of low-background, polychromatic electron beams. Such beams, consisting of quasi-monoenergetic components with controllable energy and energy separation, may be useful as drivers of polychromatic x-rays based on Thomson backscattering. These all-optical methods of electron beam quality control are critically important for the development of future compact, high-repetition-rate, GeV-scale LPA using 10 TW-class, ultra-high bandwidth pulses and mm-scale, dense
Energy Technology Data Exchange (ETDEWEB)
Wu, S.; Wang, Z.; Huang, Q.; Tan, X.; Lu, X. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Ostrikov, K. [CSIRO Materials Science and Engineering, PO Box 218, Lindfield NSW 2070 (Australia); School of Physics, University of Sydney, Sydney NSW 2006 (Australia); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)
2013-02-15
Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generated by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.
A versatile ray-tracing code for studying rf wave propagation in toroidal magnetized plasmas
International Nuclear Information System (INIS)
Peysson, Y; Decker, J; Morini, L
2012-01-01
A new ray-tracing code named C3PO has been developed to study the propagation of arbitrary electromagnetic radio-frequency (rf) waves in magnetized toroidal plasmas. Its structure is designed for maximum flexibility regarding the choice of coordinate system and dielectric model. The versatility of this code makes it particularly suitable for integrated modeling systems. Using a coordinate system that reflects the nested structure of magnetic flux surfaces in tokamaks, fast and accurate calculations inside the plasma separatrix can be performed using analytical derivatives of a spline-Fourier interpolation of the axisymmetric toroidal MHD equilibrium. Applications to reverse field pinch magnetic configuration are also included. The effects of 3D perturbations of the axisymmetric toroidal MHD equilibrium, due to the discreteness of the magnetic coil system or plasma fluctuations in an original quasi-optical approach, are also studied. Using a Runge–Kutta–Fehlberg method for solving the set of ordinary differential equations, the ray-tracing code is extensively benchmarked against analytical models and other codes for lower hybrid and electron cyclotron waves. (paper)
International Nuclear Information System (INIS)
Foroutan, G.; Khalilpour, H.; Moslehi-Fard, M.; Li, B.; Robinson, P. A.
2008-01-01
The effects of plasma inhomogeneities on the propagation of a cloud of hot electrons through a cold background plasma and generation of Langmuir waves are investigated using numerical simulations of the quasilinear equations. It is found that in a plasma with decreasing density the quasilinear relaxation of the electron distribution in velocity space is accelerated and the levels of the generated Langmuir waves are enhanced. The magnitude of the induced emission rate is increased and its maximum value moves to lower velocities. Due to density gradient the height of plateau shows an increase at small distances and a corresponding decrease at large distances. It is also found that in a plasma with decreasing temperature, the relaxation of the beam is retarded, the spectral density of Langmuir waves is broadened, and the height of the plateau decreases below its value in a uniform plasma. In the presence of both density and temperature gradients, at given position, the height and upper boundary of the plateau and the level of Langmuir waves are all increased at small velocities. The spatial expansion of the beam is increased by the plasma inhomogeneities, but its average velocity of propagation decreases. Initially, at a given position, the velocity at the upper boundary of the plateau is smaller in the presence of the density gradient than in the uniform plasma but the reverse is true at longer times. Due to temperature gradient, at large times and small distances, the upper boundary of the plateau is increased above its value in the uniform plasma. Because of fast relaxation, the value of the lower boundary of the plateau in the plasma with decreasing density is always less than its value in the uniform plasma. It is found that the local velocity of the beam decreases when the density gradient is present. The local velocity spread of the beam remains unchanged during the propagation of the beam in the uniform plasma, but increases in the presence of inhomogeneities.
Claverie, A; Deroy, J; Boustie, M; Avrillaud, G; Chuvatin, A; Mazanchenko, E; Demol, G; Dramane, B
2014-06-01
High power pulsed electrical discharges into liquids are investigated for new industrial applications based on the efficiency of controlled shock waves. We present here new experimental data obtained by combination of detailed high speed imaging equipments. It allows the visualization of the very first instants of plasma discharge formation, and then the pulsations of the gaseous bubble with an accurate timing of events. The time history of the expansion/compression of this bubble leads to an estimation of the energy effectively transferred to water during the discharge. Finally, the consecutive shock generation driven by this pulsating bubble is optically monitored by shadowgraphs and schlieren setup. These data provide essential information about the geometrical pattern and chronometry associated with the shock wave generation and propagation.
DEFF Research Database (Denmark)
Xu, G.S.; Naulin, Volker; Fundamenski, W.
2010-01-01
Drift-Alfvén vortex filaments associated with electromagnetic turbulence were recently identified in reversed field pinch devices. Similar propagating filamentary structures were observed in the Earth magnetosheath, magnetospheric cusp and Saturn’s magnetosheath by spacecrafts. The characteristics...... energy, magnetic momentum, and angular momentum. The perpendicular vortex motions and the kinetic shear Alfvén waves are coupled through the parallel current and Ampere’s law, leading to field line bending. On the timescale of interchange motion τ⊥, a thermal expansion force in the direction of curvature......, heat, and momentum in the fusion plasmas can be interpreted in terms of the ballistic motion of these solitary electromagnetic filamentary structures....
Deshpande, K.; Zettergren, M. D.; Datta-Barua, S.
2017-12-01
Fluctuations in the Global Navigation Satellite Systems (GNSS) signals observed as amplitude and phase scintillations are produced by plasma density structures in the ionosphere. Phase scintillation events in particular occur due to structures at Fresnel scales, typically about 250 meters at ionospheric heights and GNSS frequency. Likely processes contributing to small-scale density structuring in auroral and polar regions include ionospheric gradient-drift instability (GDI) and Kelvin-Helmholtz instability (KHI), which result, generally, from magnetosphere-ionosphere interactions (e.g. reconnection) associated with cusp and auroral zone regions. Scintillation signals, ostensibly from either GDI or KHI, are frequently observed in the high latitude ionosphere and are potentially useful diagnostics of how energy from the transient forcing in the cusp or polar cap region cascades, via instabilities, to small scales. However, extracting quantitative details of instabilities leading to scintillation using GNSS data drastically benefits from both a model of the irregularities and a model of GNSS signal propagation through irregular media. This work uses a physics-based model of the generation of plasma density irregularities (GEMINI - Geospace Environment Model of Ion-Neutral Interactions) coupled to an ionospheric radio wave propagation model (SIGMA - Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere) to explore the cascade of density structures from medium to small (sub-kilometer) scales. Specifically, GEMINI-SIGMA is used to simulate expected scintillation from different instabilities during various stages of evolution to determine features of the scintillation that may be useful to studying ionospheric density structures. Furthermore we relate the instabilities producing GNSS scintillations to the transient space and time-dependent magnetospheric phenomena and further predict characteristics of scintillation in different geophysical
International Nuclear Information System (INIS)
Segre, S. E.
2001-01-01
The known analytic expressions for the evolution of the polarization of electromagnetic waves propagating in a plasma with uniformly sheared magnetic field are extended to the case where the shear is not constant. Exact analytic expressions are found for the case when the space variations of the medium are such that the magnetic field components and the plasma density satisfy a particular condition (eq. 13), possibly in a convenient reference frame of polarization space [it
ALCBEAM - Neutral beam formation and propagation code for beam-based plasma diagnostics
Bespamyatnov, I. O.; Rowan, W. L.; Liao, K. T.
2012-03-01
ALCBEAM is a new three-dimensional neutral beam formation and propagation code. It was developed to support the beam-based diagnostics installed on the Alcator C-Mod tokamak. The purpose of the code is to provide reliable estimates of the local beam equilibrium parameters: such as beam energy fractions, density profiles and excitation populations. The code effectively unifies the ion beam formation, extraction and neutralization processes with beam attenuation and excitation in plasma and neutral gas and beam stopping by the beam apertures. This paper describes the physical processes interpreted and utilized by the code, along with exploited computational methods. The description is concluded by an example simulation of beam penetration into plasma of Alcator C-Mod. The code is successfully being used in Alcator C-Mod tokamak and expected to be valuable in the support of beam-based diagnostics in most other tokamak environments. Program summaryProgram title: ALCBEAM Catalogue identifier: AEKU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKU_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 66 459 No. of bytes in distributed program, including test data, etc.: 7 841 051 Distribution format: tar.gz Programming language: IDL Computer: Workstation, PC Operating system: Linux RAM: 1 GB Classification: 19.2 Nature of problem: Neutral beams are commonly used to heat and/or diagnose high-temperature magnetically-confined laboratory plasmas. An accurate neutral beam characterization is required for beam-based measurements of plasma properties. Beam parameters such as density distribution, energy composition, and atomic excited populations of the beam atoms need to be known. Solution method: A neutral beam is initially formed as an ion beam which is extracted from
Propagation Diagnostic Simulations Using High-Resolution Equatorial Plasma Bubble Simulations
Rino, C. L.; Carrano, C. S.; Yokoyama, T.
2017-12-01
In a recent paper, under review, equatorial-plasma-bubble (EPB) simulations were used to conduct a comparative analysis of the EPB spectra characteristics with high-resolution in-situ measurements from the C/NOFS satellite. EPB realizations sampled in planes perpendicular to magnetic field lines provided well-defined EPB structure at altitudes penetrating both high and low-density regions. The average C/NOFS structure in highly disturbed regions showed nearly identical two-component inverse-power-law spectral characteristics as the measured EPB structure. This paper describes the results of PWE simulations using the same two-dimensional cross-field EPB realizations. New Irregularity Parameter Estimation (IPE) diagnostics, which are based on two-dimensional equivalent-phase-screen theory [A theory of scintillation for two-component power law irregularity spectra: Overview and numerical results, by Charles Carrano and Charles Rino, DOI: 10.1002/2015RS005903], have been successfully applied to extract two-component inverse-power-law parameters from measured intensity spectra. The EPB simulations [Low and Midlatitude Ionospheric Plasma DensityIrregularities and Their Effects on Geomagnetic Field, by Tatsuhiro Yokoyama and Claudia Stolle, DOI 10.1007/s11214-016-0295-7] have sufficient resolution to populate the structure scales (tens of km to hundreds of meters) that cause strong scintillation at GPS frequencies. The simulations provide an ideal geometry whereby the ramifications of varying structure along the propagation path can be investigated. It is well known path-integrated one-dimensional spectra increase the one-dimensional index by one. The relation requires decorrelation along the propagation path. Correlated structure would be interpreted as stochastic total-electron-content (TEC). The simulations are performed with unmodified structure. Because the EPB structure is confined to the central region of the sample planes, edge effects are minimized. Consequently
Uncertainty propagation in modeling of plasma-assisted hydrogen production from biogas
Zaherisarabi, Shadi; Venkattraman, Ayyaswamy
2016-10-01
With the growing concern of global warming and the resulting emphasis on decreasing greenhouse gas emissions, there is an ever-increasing need to utilize energy-production strategies that can decrease the burning of fossil fuels. In this context, hydrogen remains an attractive clean-energy fuel that can be oxidized to produce water as a by-product. In spite of being an abundant species, hydrogen is seldom found in a form that is directly usable for energy-production. While steam reforming of methane is one popular technique for hydrogen production, plasma-assisted conversion of biogas (carbon dioxide + methane) to hydrogen is an attractive alternative. Apart from producing hydrogen, the other advantage of using biogas as raw material is the fact that two potent greenhouse gases are consumed. In this regard, modeling is an important tool to understand and optimize plasma-assisted conversion of biogas. The primary goal of this work is to perform a comprehensive statistical study that quantifies the influence of uncertain rate constants thereby determining the key reaction pathways. A 0-D chemical kinetics solver in the OpenFOAM suite is used to perform a series of simulations to propagate the uncertainty in rate constants and the resulting mean and standard deviation of outcomes.
International Nuclear Information System (INIS)
Loupias, B.
2008-10-01
Plasma jets are often observed in the polar regions of Young Stellar Objects (YSO). For a better understanding of the whole processes at the origin of their formation and evolution, this research thesis aims at demonstrating the feasibility of a plasma jet generation by a power laser, and at investigating its characteristics. After a detailed description of Young Stellar Objects jets and an overview of theoretical models, the author describes some experiments performed with gas guns, pulsed machines and power lasers. He describes means of generation of a jet by laser interaction via strong shock propagation. He reports experimental work, describing the target, laser operating conditions and the determination of jet parameters: speed, temperature, density. Then, he introduces results obtained for plasma jet propagation in vacuum, describes their evolution with respect to initial conditions (target type, laser operating conditions), and identifies optimal conditions for generating a jet similar to that in astrophysical conditions. He considers their propagation in ambient medium like for YSO jets in interstellar medium. Two distinct cases are investigated: collision of two successive shocks in a gaseous medium, and propagation of a plasma jet in a gas jet
International Nuclear Information System (INIS)
Sebelin, E.; Peysson, Y.; Litaudon, X.; Moreau, D.
1997-09-01
In the context of complex Hilbert spaces is proved, around Lax-Milgram lemma, the existence and uniqueness of solutions associated to a class of stationary variational problems. This result is applied to the study of variational problems from the propagation equation of time-harmonic electromagnetic waves in confined tokamak plasmas. (author)
Energy Technology Data Exchange (ETDEWEB)
Sebelin, E.; Peysson, Y.; Litaudon, X.; Moreau, D. [Association Euratom-CEA, CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Miellou, J.C. [Besancon Univ., 25 (France). Laboratoire d`Analyse Numerique; Lafitte, O. [CEA Limeil, 94 - Villeneuve-Saint-Georges (France)
1997-09-01
In the context of complex Hilbert spaces is proved, around Lax-Milgram lemma, the existence and uniqueness of solutions associated to a class of stationary variational problems. This result is applied to the study of variational problems from the propagation equation of time-harmonic electromagnetic waves in confined tokamak plasmas. (author) 21 refs.
International Nuclear Information System (INIS)
Mahdy, A.I.
2005-12-01
A generalized Peaceman-Rachford (P-R) ADI form based on the regularized finite difference scheme is employed in order to study the interactions of two co-propagating laser beams in underdense plasmas. A numerical algorithm using the P-R ADI form is constructed for solution of coupled 2D time-dependent non-linear Schroedinger equations for quasineutral plasmas in paraxial approximation. The ability of the form to solve the equations is discussed, and its performance in simulating phenomena associated with the interactions in the presence of pondermotive nonlinearity and relativistic nonlinearity is examined. It is shown that the generalized P-R ADI form can accurately solve the coupled NLS equations. With simulation results, the form is shown to be suitable to simulate the interactions of two co-propagating laser beams with underdense plasma, and it can successively simulate the associated phenomena at varying conditions. (author)
Energy Technology Data Exchange (ETDEWEB)
Maneva, Y.; Lazar, M.; Poedts, S. [Centre for Mathematical Plasma Astrophysics, Celestijnenlaan 200B, 3001 Heverlee (Belgium); Viñas, A., E-mail: yana.maneva@wis.kuleuven.be [NASA Goddard Space Flight Center, Heliophysics Science Division, Greenbelt, MD 20771 (United States)
2016-11-20
The double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons, unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much faster and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma β and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.
Maneva, Y.; Lazar, M.; Vinas, A.; Poedts, S.
2016-01-01
The double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons,? unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much faster and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma ß and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.
International Nuclear Information System (INIS)
Nalesso, G.; Jacobson, A.R.
1984-01-01
Using a ten-chord interferometer, we have measured a field-aligned (k/sub parallel/roughly-equal2 m -1 ; k/sub perpendicular/> or approx. =25 m -1 ) plasma-density disturbance propagating along B with a speed in the ion acoustic range. The propagation is purely in the electron drift direction and is observed only when the drift parameter (electron drift speed/electron thermal speed)> or approx. =0.1. A novel spatial-filter technique resolves this localized mode, which otherwise would be hidden by more robust global disturbances present along the lines of sight
Energy Technology Data Exchange (ETDEWEB)
Bottiglioni, F; Coutant, J; Gadda, E; Prevot, F [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires
1966-12-01
A plasma column is created in a magnetic field by longitudinal diffusion from a low-pressure pulsed discharge in hydrogen. Depending on the discharge conditions, two regimes are obtained in which the gas pumping speed has a different effect upon the plasma density in the column. Calculations are presented which can explain this effect by a difference in the transverse diffusion coefficient. (authors) [French] On forme une colonne de plasma dans un champ magnetique par diffusion longitudinale a partir d'une decharge puisee dans l'hydrogene a basse pression. Selon les conditions de la decharge on observe deux regimes differents pour lesquels le pompage du gaz neutre a un effet different sur la densite resultante du plasma dans la colonne. On presente des calculs qui peuvent expliquer cet effet par une difference dans la diffusion transversale du plasma. (auteurs)
Energy Technology Data Exchange (ETDEWEB)
López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción 4070386 (Chile); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [Geospace Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Valdivia, Juan A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología (CEDENNA), Santiago 9170124 (Chile)
2015-09-15
We use a particle-in-cell simulation to study the propagation of localized structures in a magnetized electron-positron plasma with relativistic finite temperature. We use as initial condition for the simulation an envelope soliton solution of the nonlinear Schrödinger equation, derived from the relativistic two fluid equations in the strongly magnetized limit. This envelope soliton turns out not to be a stable solution for the simulation and splits in two localized structures propagating in opposite directions. However, these two localized structures exhibit a soliton-like behavior, as they keep their profile after they collide with each other due to the periodic boundary conditions. We also observe the formation of localized structures in the evolution of a spatially uniform circularly polarized Alfvén wave. In both cases, the localized structures propagate with an amplitude independent velocity.
International Nuclear Information System (INIS)
López, Rodrigo A.; Muñoz, Víctor; Viñas, Adolfo F.; Valdivia, Juan A.
2015-01-01
We use a particle-in-cell simulation to study the propagation of localized structures in a magnetized electron-positron plasma with relativistic finite temperature. We use as initial condition for the simulation an envelope soliton solution of the nonlinear Schrödinger equation, derived from the relativistic two fluid equations in the strongly magnetized limit. This envelope soliton turns out not to be a stable solution for the simulation and splits in two localized structures propagating in opposite directions. However, these two localized structures exhibit a soliton-like behavior, as they keep their profile after they collide with each other due to the periodic boundary conditions. We also observe the formation of localized structures in the evolution of a spatially uniform circularly polarized Alfvén wave. In both cases, the localized structures propagate with an amplitude independent velocity
Energy Technology Data Exchange (ETDEWEB)
Tian, Yuan; Han, Yiping, E-mail: yphan@xidian.edu.cn [School of Physics and Optoelectronic Engineering, Xidian University, Xi' an 710071 (China); Ai, Xia [National Key Laboratory of Science and Technology on Test physics and Numerical Mathematical, Beijing 100076 (China); Liu, Xiuxiang [Science and Technology on Space Physics Laboratory, Beijing 100076 (China)
2014-12-15
In this paper, we investigate the propagation of terahertz (THz) electromagnetic wave in an anisotropic magnetized plasma by JE convolution-finite difference time domain method. The anisotropic characteristic of the plasma, which leads to right-hand circularly polarized (RCP) and right-hand circularly polarized (LCP) waves, has been taken into account. The interaction between electromagnetic waves and magnetized plasma is illustrated by reflection and transmission coefficients for both RCP and LCP THz waves. The effects of both the magnetized plasma thickness and the external magnetized field are analyzed and numerical results demonstrate that the two factors could influence the THz wave greatly. It is worthy to note that besides the reflection and transmission coefficients in the frequency domain, the waveform of the electric field in the time domain varying with thicknesses and external magnetic fields for different polarized direction has been studied.
International Nuclear Information System (INIS)
Purohit, Gunjan; Rawat, Priyanka; Chauhan, Prashant; Mahmoud, Saleh T.
2015-01-01
This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled laser beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate
International Nuclear Information System (INIS)
Singh, Kh.I.; Das, G.C.
1993-01-01
Soliton propagations are studied in a relativistic multicomponent ion-beam plasma through the derivation of Korteweg-deVries (K-dV) and modified K-dV (mK-dV) equations. A generalization of the mK-dV equation involving higher order nonlinearities gives a transitive link between the K-dV and mK-dV equations for isothermal plasma, and the validity of this generalized equation throughout the whole range of negative ion concentrations is investigated through the derivation of Sagdeev potential. Parallel discussion of various K-dV solitons enlightening the experimental implications is also made. (author). 22 refs
International Nuclear Information System (INIS)
Dumont, R.J.; Phillips, C.K.; Smithe, D.N.
2003-01-01
Auxiliary heating supplied by externally launched electromagnetic waves is commonly used in toroidal magnetically confined fusion experiments for profile control via localized heating, current drive and perhaps flow shear. In these experiments, the confined plasma is often characterized by the presence of a significant population of non-thermal species arising from neutral beam injection, from acceleration of the particles by the applied waves, or from copious fusion reactions in future devices. Such non-thermal species may alter the wave propagation as well as the wave absorption dynamics in the plasma. Previous studies have treated the corresponding velocity distributions as either equivalent Maxwellians, or else have included realistic distributions only in the finite Larmor radius limit. In this work, the hot plasma dielectric response of the plasma has been generalized to treat arbitrary distribution functions in the non-relativistic limit. The generalized dielectric tensor has been incorporated into a one-dimensional full wave all-orders kinetic field code. Initial comparative studies of ion cyclotron range of frequency wave propagation and heating in plasmas with nonthermal species, represented by realistic distribution functions or by appropriately defined equivalent Maxwellians, have been completed for some specific experiments and are presented
Supersonic Heat Wave Propagation in Laser-Produced Underdense Plasma for Efficient X-Ray Generation
International Nuclear Information System (INIS)
Tanabe, M.; Nishimura, H.; Fujioka, S.; Nagai, K.; Iwamae, A.; Ohnishi, N.; Fournier, K.B.; Girard, F.; Primout, M.; Villette, B.; Tobin, M.; Mima, K.
2008-01-01
We have observed supersonic heat wave propagation in a low-density aerogel target (ρ ∼ 3.2 mg/cc) irradiated at the intensity of 4 x 10 14 W/cm 2 . The heat wave propagation was measured with a time-resolved x-ray imaging diagnostics, and the results were compared with simulations made with the two-dimensional radiation-hydrodynamic code, RAICHO. Propagation velocity of the ionization front gradually decreased as the wave propagates into the target. The reason of decrease is due to increase of laser absorption region as the front propagates and interplay of hydrodynamic motion and reflection of laser propagation. These features are well reported with the simulation
Spectral analysis of turbulence propagation mechanisms in solar wind and tokamaks plasmas
International Nuclear Information System (INIS)
Dong, Yue
2014-01-01
This thesis takes part in the study of spectral transfers in the turbulence of magnetized plasmas. We will be interested in turbulence in solar wind and tokamaks. Spacecraft measures, first principle simulations and simple dynamical systems will be used to understand the mechanisms behind spectral anisotropy and spectral transfers in these plasmas. The first part of this manuscript will introduce the common context of solar wind and tokamaks, what is specific to each of them and present some notions needed to understand the work presented here. The second part deals with turbulence in the solar wind. We will present first an observational study on the spectral variability of solar wind turbulence. Starting from the study of Grappin et al. (1990, 1991) on Helios mission data, we bring a new analysis taking into account a correct evaluation of large scale spectral break, provided by the higher frequency data of the Wind mission. This considerably modifies the result on the spectral index distribution of the magnetic and kinetic energy. A second observational study is presented on solar wind turbulence anisotropy using autocorrelation functions. Following the work of Matthaeus et al. (1990); Dasso et al. (2005), we bring a new insight on this statistical, in particular the question of normalisation choices used to build the autocorrelation function, and its consequence on the measured anisotropy. This allows us to bring a new element in the debate on the measured anisotropy depending on the choice of the referential either based on local or global mean magnetic field. Finally, we study for the first time in 3D the effects of the transverse expansion of solar wind on its turbulence. This work is based on a theoretical and numerical scheme developed by Grappin et al. (1993); Grappin and Velli (1996), but never used in 3D. Our main results deal with the evolution of spectral and polarization anisotropy due to the competition between non-linear and linear (Alfven coupling
International Nuclear Information System (INIS)
Karas, V.I.; Karas, I.V.; Levchenko, V.D.; Sigov, Yu.S.; Fainberg, Ya.B.
1997-01-01
Results of numerical simulations of the excitation of wake fields in high- and low-density plasmas are presented. The propagation of relativistic electron bunches in a plasma is described by a closed set of relativistic Vlasov equations for two spatial coordinates and three velocity coordinates for each plasma component and the nonlinear Maxwell equations for self-consistent electromagnetic fields. Numerical modeling shows that, under ordinary experimental conditions (when the length and radius of the bunch are much less than the skin depth), the radius of the bunches propagating in a plasma varies over a wide range. In this case, the dynamics of both the plasma and the bunches is nonlinear. The radial redistribution of the plasma ions in self-consistent fields leads to the formation of a plasma channel. Incorporating this phenomenon is important for studying the propagation of relativistic electron bunches in a plasma
Energy Technology Data Exchange (ETDEWEB)
Wang, S.; Chen, Z. Y.; Wang, X. H., E-mail: xhw@mail.xjtu.edu.cn; Li, D.; Yang, A. J.; Liu, D. X.; Rong, M. Z. [State Key Laboratory of Electrical Insulation and Power Equipment, Centre for Plasma Biomedicine, Xi' an Jiaotong University, Xi' an 710049 (China); Chen, H. L. [Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Kong, M. G. [State Key Laboratory of Electrical Insulation and Power Equipment, Centre for Plasma Biomedicine, Xi' an Jiaotong University, Xi' an 710049 (China); Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)
2015-11-28
Cold atmospheric-pressure plasmas have potential to be used for endoscope sterilization. In this study, a long quartz tube was used as the simulated endoscope channel, and an array of electrodes was warped one by one along the tube. Plasmas were generated in the inner channel of the tube, and their propagation characteristics in He+O{sub 2} feedstock gases were studied as a function of the oxygen concentration. It is found that each of the plasmas originates at the edge of an instantaneous cathode, and then it propagates bidirectionally. Interestingly, a plasma head with bright spots is formed in the hollow instantaneous cathode and moves towards its center part, and a plasma tail expands through the electrode gap and then forms a swallow tail in the instantaneous anode. The plasmas are in good axisymmetry when [O{sub 2}] ≤ 0.3%, but not for [O{sub 2}] ≥ 1%, and even behave in a stochastic manner when [O{sub 2}] = 3%. The antibacterial agents are charged species and reactive oxygen species, so their wall fluxes represent the “plasma dosage” for the sterilization. Such fluxes mainly act on the inner wall in the hollow electrode rather than that in the electrode gap, and they get to the maximum efficiency when the oxygen concentration is around 0.3%. It is estimated that one can reduce the electrode gap and enlarge the electrode width to achieve more homogenous and efficient antibacterial effect, which have benefits for sterilization applications.
Quantitative single shot and spatially resolved plasma wakefield diagnostics
Kasim, Muhammad Firmansyah; Ceurvorst, Luke; Levy, Matthew C; Ratan, Naren; Sadler, James; Bingham, Robert; Burrows, Philip N; Trines, Raoul; Wing, Matthew; Norreys, Peter
2015-01-01
Diagnosing plasma conditions can give great advantages in optimizing plasma wakefield accelerator experiments. One possible method is that of photon acceleration. By propagating a laser probe pulse through a plasma wakefield and extracting the imposed frequency modulation, one can obtain an image of the density modulation of the wakefield. In order to diagnose the wakefield parameters at a chosen point in the plasma, the probe pulse crosses the plasma at oblique angles relative to the wakefield. In this paper, mathematical expressions relating the frequency modulation of the laser pulse and the wakefield density profile of the plasma for oblique crossing angles are derived. Multidimensional particle-in-cell simulation results presented in this paper confirm that the frequency modulation profiles and the density modulation profiles agree to within 10%. Limitations to the accuracy of the measurement are discussed in this paper. This technique opens new possibilities to quantitatively diagnose the plasma wakefie...
International Nuclear Information System (INIS)
Kuo, S.P.; Ren, A.
1993-01-01
The main concern of the propagation of high power microwave pulse is the energy loss of the pulse before reaching the destination. The loss is caused by self-generated plasma. There are two processes which are responsible for the energy loss (so called tail erosion). They are collisional damping and cutoff reflection. In very high power region, the cutoff reflection is much more severe than the collisional damping. A frequency up-conversion process may help to avoid the cutoff reflection of powerful electromagnetic pulse propagating in a self-generated plasma. Both chamber experiments and numerical simulation are performed. When the field amplitude only slightly exceeds the breakdown threshold field of the background gas, the result shows that the carrier frequency ω of the pulse shifts upward during the growth of local plasma frequency ωpe 2 . Thus, the self-generated plasma remains underdense to the pulse. However, the spectrum of the pulse starts to break up into two major peaks when the amplitude of the pulse is further increased. The frequency of one of the peaks is lower than the original carrier frequency and that of the other peak is higher than the original carrier frequency. These phenomena are observed both experimentally and numerically. The frequency down shift result is believed to be caused by damping mechanisms. Good agreement between the experimental results and the numerical simulation is obtained
Zang, Qing; Bai, Xiangxing; Ma, Ping; Huang, Jie; Ma, Jing; Yu, Siyuan; Shi, Hongyan; Sun, Xiudong; Liu, Yang; Lu, Yueguang
2017-02-15
The optical communication method has potential for solving the blackout problem, which is a big challenge faced in the development of aerospace. Two laser transmission systems were set up to explore the influence of the plasma and the ablation particles on the propagation of the laser. The experimental results indicate that the laser can transmit through the plasma with little attenuation. When there are ablation particles of ZrB2-SiC-C added in the plasma, the intensity of the laser has fluctuations. The work introduced in this Letter can be regarded as basic research of the propagation characters of the laser through plasma sheaths.
El-Hanbaly, A. M.; El-Shewy, E. K.; Elgarayhi, A.; Kassem, A. I.
2015-11-01
The nonlinear properties of small amplitude electron-acoustic (EA) solitary and shock waves in a homogeneous system of unmagnetized collisionless plasma with nonextensive distribution for hot electrons have been investigated. A reductive perturbation method used to obtain the Kadomstev-Petviashvili-Burgers equation. Bifurcation analysis has been discussed for non-dissipative system in the absence of Burgers term and reveals different classes of the traveling wave solutions. The obtained solutions are related to periodic and soliton waves and their behavior are shown graphically. In the presence of the Burgers term, the EXP-function method is used to solve the Kadomstev-Petviashvili-Burgers equation and the obtained solution is related to shock wave. The obtained results may be helpful in better conception of waves propagation in various space plasma environments as well as in inertial confinement fusion laboratory plasmas.
International Nuclear Information System (INIS)
Startsev, Edward A.; Davidson, Ronald C.; Dorf, Mikhail
2009-01-01
When an ion beam with sharp edge propagates through a background plasma, its current is neutralized by the plasma return current everywhere except at the beam edge over a characteristic transverse distance Δx perpendicular ∼ (delta) pe , where (delta) pe = c/ω pe is the collisionless skin depth, and ω pe is the electron plasma frequency. Because the background plasma electrons neutralizing the ion beam current inside the beam are streaming relative to the background plasma electrons outside the beam, the background plasma can support a two-stream surface-mode excitation. Such surface modes have been studied previously assuming complete charge and current neutralization, and have been shown to be strongly unstable. In this paper we study the detailed stability properties of this two-stream surface mode for an electron flow velocity profile self-consistently driven by the ion beam. In particular, it is shown that the self-magnetic field generated inside the unneutralized current layer, which has not been taken into account previously, completely eliminates the instability
Energy Technology Data Exchange (ETDEWEB)
Skladnik-Sadowska, E.; Malinowski, K. [The Andrzej Soltan Institute for Nuclear Studies, IPJ, 05-400 Otwock-Swierk (Poland); Sadowski, M.J. [The Andrzej Soltan Institute for Nuclear Studies, IPJ, 05-400 Otwock-Swierk (Poland)] [Institute of Plasma Physics and Laser Microfusion, IPPLM, 01-497 Warsaw (Poland); Kubkowska, M.; Jakubowska, K.; Paduch, M.; Scholz, M. [Institute of Plasma Physics and Laser Microfusion, IPPLM, 01-497 Warsaw (Poland); Garkusha, I.E.; Ladygina, M.; Tereshin, V.I. [Institute of Plasma Physics, NSC KIPT, 61-108 Kharkov (Ukraine)
2011-07-01
The paper reports on optical spectroscopy of pulsed plasma streams during their free propagation within a vacuum chamber and their interaction with tungsten targets. Experiments were performed with the PF-1000 facility and particular attention was paid to improvements in spectroscopic diagnostics techniques. In contrary to preliminary studies, the recent spectroscopic measurements of the free plasma streams were carried out perpendicular to the z-axis and at a larger distance from the electrode outlet. The center of the observation quartz-window was located at z = 30 cm in order to observe first a pure deuterium-plasma stream, and later on some heavy impurities which might reach that distance with a delay induced by differences in their production and time-of-flight. The recorded spectral lines were identified by means of a Kurucz database. It was confirmed that at the pure D{sub 2}-filling the PF-1000 facility emits first the deuterium-plasma stream and one can observe intense deuterium Balmer lines, but at a distance z = 30 cm, after about 2 microseconds there appear many impurity lines originating mainly from the Cu-electrodes, i.e. Cu-lines. The second part of the experiment concerned the spectroscopic measurements of metal plasma 'pillow' produced by the plasma stream impinging upon a solid target made of pure tungsten. The described measurements enabled the most intense spectral lines to be identified. This document is composed of an abstract followed by the slides of the presentation
Kinetic Alfven waves and electron physics. II. Oblique slow shocks
International Nuclear Information System (INIS)
Yin, L.; Winske, D.; Daughton, W.
2007-01-01
One-dimensional (1D) particle-in-cell (PIC; kinetic ions and electrons) and hybrid (kinetic ions; adiabatic and massless fluid electrons) simulations of highly oblique slow shocks (θ Bn =84 deg. and β=0.1) [Yin et al., J. Geophys. Res., 110, A09217 (2005)] have shown that the dissipation from the ions is too weak to form a shock and that kinetic electron physics is required. The PIC simulations also showed that the downstream electron temperature becomes anisotropic (T e parallel )>T e perpendicular ), as observed in slow shocks in space. The electron anisotropy results, in part, from the electron acceleration/heating by parallel electric fields of obliquely propagating kinetic Alfven waves (KAWs) excited by ion-ion streaming, which cannot be modeled accurately in hybrid simulations. In the shock ramp, spiky structures occur in density and electron parallel temperature, where the ion parallel temperature decreases due to the reduction of the ion backstreaming speed. In this paper, KAW and electron physics in oblique slow shocks are further examined under lower electron beta conditions. It is found that as the electron beta is reduced, the resonant interaction between electrons and the wave parallel electric fields shifts to the tail of the electron velocity distribution, providing more efficient parallel heating. As a consequence, for β e =0.02, the electron physics is shown to influence the formation of a θ Bn =75 deg. shock. Electron effects are further enhanced at a more oblique shock angle (θ Bn =84 deg.) when both the growth rate and the range of unstable modes on the KAW branch increase. Small-scale electron and ion phase-space vortices in the shock ramp formed by electron-KAW interactions and the reduction of the ion backstreaming speed, respectively, are observed in the simulations and confirmed in homogeneous geometries in one and two spatial dimensions in the accompanying paper [Yin et al., Phys. Plasmas 14, 062104 (2007)]. Results from this study
Energy Technology Data Exchange (ETDEWEB)
Wang, Li; Hong, Xue-Ren, E-mail: hxr_nwnu@163.com; Sun, Jian-An, E-mail: sunja@nwnu.edu.cn; Tang, Rong-An; Yang, Yang; Zhou, Wei-Jun; Tian, Jian-Min; Duan, Wen-Shan
2017-07-12
The propagation of q-Gaussian laser beam in a preformed plasma channel is investigated by means of the variational method. A differential equation for the spot size has been obtained by including the effects of relativistic self-focusing, ponderomotive self-channeling and preformed channel focusing. The propagation behaviors and their corresponding physical conditions are identified. The comparison of the propagation between q-Gaussian and Gaussian laser beams is done by theoretical and numerical analysis. It is shown that, in the same channel, the focusing power of q-Gaussian laser beam is lower than that of Gaussian laser beam, i.e., the q-Gaussian laser beam is easier to focus than Gaussian laser beam. - Highlights: • Some behaviors for Gaussian laser are also found for q-Gaussian one. • The parameter regions corresponding to different laser behaviors are given. • Influence of q on the laser propagation behavior is obvious. • The q-Gaussian laser beam is easier to focus than the Gaussian one.
International Nuclear Information System (INIS)
Wang, Li; Hong, Xue-Ren; Sun, Jian-An; Tang, Rong-An; Yang, Yang; Zhou, Wei-Jun; Tian, Jian-Min; Duan, Wen-Shan
2017-01-01
The propagation of q-Gaussian laser beam in a preformed plasma channel is investigated by means of the variational method. A differential equation for the spot size has been obtained by including the effects of relativistic self-focusing, ponderomotive self-channeling and preformed channel focusing. The propagation behaviors and their corresponding physical conditions are identified. The comparison of the propagation between q-Gaussian and Gaussian laser beams is done by theoretical and numerical analysis. It is shown that, in the same channel, the focusing power of q-Gaussian laser beam is lower than that of Gaussian laser beam, i.e., the q-Gaussian laser beam is easier to focus than Gaussian laser beam. - Highlights: • Some behaviors for Gaussian laser are also found for q-Gaussian one. • The parameter regions corresponding to different laser behaviors are given. • Influence of q on the laser propagation behavior is obvious. • The q-Gaussian laser beam is easier to focus than the Gaussian one.
Energy Technology Data Exchange (ETDEWEB)
Yao, Jingfeng; Yuan, Chengxun, E-mail: yuancx@hit.edu.cn, E-mail: zhouzx@hit.edu.cn; Gao, Ruilin; Jia, Jieshu; Wang, Ying; Zhou, Zhongxiang, E-mail: yuancx@hit.edu.cn, E-mail: zhouzx@hit.edu.cn; Wang, Xiaoou [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Wu, Jian [National Key Laboratory of Electromagnetic Environment (LEME), China Research Institute of Radio Wave Propagation, Beijing 102206 (China); Li, Hui [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); National Key Laboratory of Electromagnetic Environment (LEME), China Research Institute of Radio Wave Propagation, Beijing 102206 (China)
2016-08-15
This study focuses on the transmission of normal-incidence electromagnetic waves in one-dimensional plasma photonic crystals. Using the Maxwell's equations in a medium, a method that is based on the concept of impendence is employed to perform the simulation. The accuracy of the method was evaluated by simulating a one-layer plasma and conventional photonic crystal. In frequency-domain, the transmission and reflection coefficients in the unmagnetized plasma photonic crystal were calculated, and the influence factors on plasma photonic crystals including dielectric constants of dielectric, spatial period, filling factor, plasma frequency, and collision frequency were studied.
International Nuclear Information System (INIS)
Bulanov, S.V.; Esirkepov, T.Z.; Naumova, N.M.
1996-01-01
Particle-in-cell simulation has been performed to study the spatial-temporal evolution of the pulse propagating in an underdense plasma. The spectra both of the reflected and transmitted radiation are investigated. The spectrum structure of the reflected radiation is due to the backward stimulated Raman scattering meanwhile the transmitted radiation structure is mainly due to the nonlinear self-phase-modulation. The influence of the pulse shape on the transmitted radiation spectrum is revealed. The dependence of the main features of the spectrum and the self-consistent pulse distortion is found. The pulse distortion is accompanied by the relativistic electrons generation. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
Misguich, J.H.
1978-09-01
The physical meaning of perturbed trajectories in turbulent fields is analysed. Special care is devoted to the asymptotic description of average trajectories for long time intervals, as occuring in many recent plasma turbulence theories. Equivalence is proved between asymptotic average trajectories described as well (i) by the propagators V(t,t-tau) for retrodiction and Wsub(J)(t,t+tau) for prediction, and (ii) by the long time secular behavior of the solution of the equations of motion. This confirms the equivalence between perturbed orbit theories and renormalized theories, including non-Markovian contributions
APPARENT CROSS-FIELD SUPERSLOW PROPAGATION OF MAGNETOHYDRODYNAMIC WAVES IN SOLAR PLASMAS
Energy Technology Data Exchange (ETDEWEB)
Kaneko, T.; Yokoyama, T. [Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Goossens, M.; Doorsselaere, T. Van [Centre for Mathematical Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, Bus 2400, B-3001 Herverlee (Belgium); Soler, R.; Terradas, J. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain); Wright, A. N., E-mail: kaneko@eps.s.u-tokyo.ac.jp [School of Mathematics and Statistics, University of St Andrews, St Andrews, KY16 9SS (United Kingdom)
2015-10-20
In this paper we show that the phase-mixing of continuum Alfvén waves and/or continuum slow waves in the magnetic structures of the solar atmosphere as, e.g., coronal arcades, can create the illusion of wave propagation across the magnetic field. This phenomenon could be erroneously interpreted as fast magnetosonic waves. The cross-field propagation due to the phase-mixing of continuum waves is apparent because there is no real propagation of energy across the magnetic surfaces. We investigate the continuous Alfvén and slow spectra in two-dimensional (2D) Cartesian equilibrium models with a purely poloidal magnetic field. We show that apparent superslow propagation across the magnetic surfaces in solar coronal structures is a consequence of the existence of continuum Alfvén waves and continuum slow waves that naturally live on those structures and phase-mix as time evolves. The apparent cross-field phase velocity is related to the spatial variation of the local Alfvén/slow frequency across the magnetic surfaces and is slower than the Alfvén/sound velocities for typical coronal conditions. Understanding the nature of the apparent cross-field propagation is important for the correct analysis of numerical simulations and the correct interpretation of observations.
Hsu, S. C.; Moser, A. L.; Merritt, E. C.; Adams, C. S.
2015-11-01
Over the past 4 years on the Plasma Liner Experiment (PLX) at LANL, we have studied obliquely and head-on-merging supersonic plasma jets of an argon/impurity or hydrogen/impurity mixture. The jets are formed/launched by pulsed-power-driven railguns. In successive experimental campaigns, we characterized the (a) evolution of plasma parameters of a single plasma jet as it propagated up to ~ 1 m away from the railgun nozzle, (b) density profiles and 2D morphology of the stagnation layer and oblique shocks that formed between obliquely merging jets, and (c) collisionless interpenetration transitioning to collisional stagnation between head-on-merging jets. Key plasma diagnostics included a fast-framing CCD camera, an 8-chord visible interferometer, a survey spectrometer, and a photodiode array. This talk summarizes the primary results mentioned above, and highlights analyses of inferred post-shock temperatures based on observations of density gradients that we attribute to shock-layer thickness. We also briefly describe more recent PLX experiments on Rayleigh-Taylor-instability evolution with magnetic and viscous effects, and potential future collisionless shock experiments enabled by low-impurity, higher-velocity plasma jets formed by contoured-gap coaxial guns. Supported by DOE Fusion Energy Sciences and LANL LDRD.
Propagation of quasi-static wave and resonance cone in magnetized plasma
International Nuclear Information System (INIS)
Serbeto, A.P.B.
1980-08-01
The potential created by an oscillating punctual source in a magnetized homogeneous cold plasma, using quasistatic approximation is studied. The resonance cone structure in this plasma is theoretically obtained and it is verified that the conic field structure remains finite for an inhomogeneous cold plasma. The temperature effect in the resonance cone structure in layers where w->Ω e ,w->w PC and w->w nh for magnetized homogeneous electron plasma is studied. An approximated expression for dispersion relations is obtained, so that an analytical solution for the potential in these layers can be calculated. The theorem of energy conservation for quasistatic waves is developed. (M.C.K.) [pt
International Nuclear Information System (INIS)
Aleshkevich, Viktor A; Kartashev, Ya V; Vysloukh, Victor A
2000-01-01
The specific features of the propagation of soliton-like light beams through a fully ionised two-dimensional cold plasma are considered employing analytical and numerical methods commonly used in nonlinear optics. Exact soliton profiles for the lower and upper soliton branches are found numerically in the presence of optical bistability. It is shown that the interaction of incoherent soliton-like laser beams in such a plasma may result both in the destruction of one of the beams and in production of new ones. The regime of the modulation instability of a plane wave propagating through a cold laser-produced plasma is studied. (nonlinear optical phenomena)
Wave propagation through an electron cyclotron resonance layer
International Nuclear Information System (INIS)
Westerhof, E.
1997-01-01
The propagation of a wave beam through an electron cyclotron resonance layer is analysed in two-dimensional slab geometry in order to assess the deviation from cold plasma propagation due to resonant, warm plasma changes in wave dispersion. For quasi-perpendicular propagation, N ' 'parallel to'' ≅ v t /c, an O-mode beam is shown to exhibit a strong wiggle in the trajectory of the centre of the beam when passing through the fundamental electron cyclotron resonance. The effects are largest for low temperatures and close to perpendicular propagation. Predictions from standard dielectric wave energy fluxes are inconsistent with the trajectory of the beam. Qualitatively identical results are obtained for the X-mode second harmonic. In contrast, the X-mode at the fundamental resonance shows significant deviations form cold plasma propagation only for strongly oblique propagation and/or high temperatures. On the basis of the obtained results a practical suggestion is made for ray tracing near electron cyclotron resonance. (Author)
El-Taibany, W. F.; El-Siragy, N. M.; Behery, E. E.; Elbendary, A. A.; Taha, R. M.
2018-05-01
The propagation characteristics of dust acoustic waves (DAWs) in a dusty plasma consisting of variable size dust grains, hybrid Cairns-Tsallis-distributed electrons, and nonthermal ions are studied. The charging of the dust grains is described by the orbital-motion-limited theory and the size of the dust grains obeys the power law dust size distribution. To describe the nonlinear propagation of the DAWs, a Zakharov-Kuznetsov equation is derived using a reductive perturbation method. It is found that the nonthermal and nonextensive parameters influence the main properties of DAWs. Moreover, our results reveal that the rarefactive waves can propagate mainly in the proposed plasma model while compressive waves can be detected for a very small range of the distribution parameters of plasma species, and the DAWs are faster and wider for smaller size dust grains. Applications of the present results to dusty plasma observations are briefly discussed.
A numerical analysis of high power laser propagation in magnetized plasmas
International Nuclear Information System (INIS)
Druce, R.L.; Kristiansen, M.; Hagler, M.O.
1977-01-01
A computer code developed to predict laser-plasma interaction in cylindrical magnetized plasmas is described. Two problems of interest have been studied viz., the bleaching wave behaviour and a comparison with experimental results obtained in earlier investigations. The agreement with experiment is found to be fairly good. (A.K.)
Propagation and reflection of chirped pulses in the nonuniform ionospheric plasma
International Nuclear Information System (INIS)
Levitsky, S.M.
2009-01-01
By passing of a chirped pulse in a inhomogeneous ionospheric plasma this pulses due to the dispersion futures of the plasma becomes deformed and can be strongly compressed. The chirped pulse can be compressed also being reflected by the ionosphere. This can give some advantage using such pulses in the experiments of ionospheric zoning.
To the mechanism of modulated REB current increase during its propagation through plasma
International Nuclear Information System (INIS)
Kiselev, V.A.; Linnik, A.F.; Maslov, V.I.; Uskov, V.V.
2002-01-01
The mechanism of full current increase is investigated in this paper. This current arises at transporting of the short relativistic electron bunches in the plasma,formed by them at gas of large pressure. This phenomenon is determined by the electric field, arising at motion of the relativistic electron bunches, having an angular divergence, in the plasma
Preferential heating of oxygen 5{sup +} ions by finite-amplitude oblique Alfvén waves
Energy Technology Data Exchange (ETDEWEB)
Maneva, Yana G.; Poedts, Stefaan [Centre for mathematical Plasma Astrophysics, KU Leuven, B-3001 Leuven (Belgium); Viñas, Adolfo [NASA Goddard Space Flight Center, Heliophysics Science Division, Greenbelt, 20771 MD (United States); Araneda, Jaime [Departamento de Física, Universidad de Concepción, Casilla 160 - C, Concepción (Chile)
2016-03-25
Minor ions in the fast solar wind are known to have higher temperatures and to flow faster than protons in the interplanetary space. In this study we combine previous research on parametric instability theory and 2.5D hybrid simulations to study the onset of preferential heating of Oxygen 5{sup +} ions by large-scale finite-amplitude Alfvén waves in the collisionless fast solar wind. We consider initially non-drifting isotropic multi-species plasma, consisting of isothermal massless fluid electrons, kinetic protons and kinetic Oxygen 5{sup +} ions. The external energy source for the plasma heating and energization are oblique monochromatic Alfvén-cyclotron waves. The waves have been created by rotating the direction of initial parallel pump, which is a solution of the multi-fluid plasma dispersion relation. We consider propagation angles θ ≤ 30°. The obliquely propagating Alfvén pump waves lead to strong diffusion in the ion phase space, resulting in highly anisotropic heavy ion velocity distribution functions and proton beams. We discuss the application of the model to the problems of preferential heating of minor ions in the solar corona and the fast solar wind.
Study on intense relativistic electron beam propagation in a low density collisionless plasma
International Nuclear Information System (INIS)
Korenev, S.A.; Rubin, N.B.; Khodataev, K.V.
1982-01-01
The results of investigations into the increase in effectivity of transport of an intensive relativistic electron beam (IREB) in a collisionless plasma of low density are presented. The electron beam with the current of 1.5 kA, energy of 300 keV, radius of 1.5 cm is in ected into a plasma channel 180 cm long which is a metallic cylinder covered with a biniplast layer from inside 0.5 cm thickness on which there is a metallic net from the vacuum side. Plasma production is carried out during the supply of voltage pulse to the net. A condition of the optimum IREB distribution is found. It is sohwn that self-focusing IREB transport in plasma of low density can be effective if equilibrium conditions are carried out in plasma with the concentration of electrons less (or equal) to the concentration of electrons in a beam
Multispecies Weibel Instability for Intense Ion Beam Propagation Through Background Plasma
Davidson, Ronald C; Kaganovich, Igor D; Qin, Hong; Startsev, Edward
2005-01-01
In application of heavy ion beams to high energy density physics and fusion, background plasma is utilized to neutralize the beam space charge during drift compression and/or final focus of the ion beam. It is important to minimize the deleterious effects of collective instabilities on beam quality associated with beam-plasma interactions. Plasma electrons tend to neutralize both the space charge and current of the beam ions. It is shown that the presence of the return current greatly modifies the electromagnetic Weibel instability (also called the filamentation instability), i.e., the growth rate of the filamentation instability greatly increases if the background ions are much lighter than the beam ions and the plasma density is comparable to the ion beam density. This may preclude using underdense plasma of light gases in heavy ion beam applications. It is also shown that the return current may be subject to the fast electrostatic two-stream instability.
International Nuclear Information System (INIS)
Heidari, E; Aslaninejad, M; Eshraghi, H
2010-01-01
Using a set of relativistic equations for plasmas with warm electrons and cold ions, we have investigated the effects of trapped electrons in the propagation of an electrosound wave and discussed the possibility of the formation of electromagnetic solitons in a plasma. The effective potential energy and deviations of the electron and ion number densities in this relativistic model have been found. We have obtained the governing equations for the amplitude of the HF field with relativistic corrections. In order to show the destructive impact of the trapped electrons on the solitary wave, a relativistic effective potential and the governing equation have been found. It is shown that for certain values of the parameters the condition of localization of the HF amplitude is violated. In addition, it is shown that as the flow velocity of the plasma changes, the shape of the solitary wave shows two opposing behaviours, depending on whether the solitary wave velocity is larger than the flow velocity or smaller. Also, the existence of stationary solitary waves which are prohibited for nonrelativistic plasma has been predicted. Finally, we have obtained the Korteweg-de Vries equation showing the relativistic, trapping and nonlinearity effects.
International Nuclear Information System (INIS)
Golubovskii, Yu B; Kozakov, R V; Wilke, C; Behnke, J; Nekutchaev, V O
2004-01-01
Time and space resolved measurements of the plasma potential in axial and radial directions in S- and P-striations in neon are performed. The measurements in different radial positions were carried out with high spatial resolution by means of simultaneous displacement of electrodes relative to the stationary probe. The plasma potential was found to be a superposition of the potentials of ionization wave and plasma oscillations relative to the electrodes. A method of decomposition of the measured spatio-temporal structure of the potential in components associated with the plasma oscillations and ionization wave propagation is proposed. A biorthogonal decomposition of the spatio-temporal structure of the potential is performed. A comparison of the decomposition results obtained by the two methods is made. The experiments revealed a two-dimensional structure of the potential field in an ionization wave. Qualitative discussions of the reasons for the occurrence of this two-dimensional structure are presented based on the analysis of the kinetic equation and the equation for the potential
International Nuclear Information System (INIS)
Abe, Hirotada; Kajitani, Hiroyuki; Itatani, Ryohei.
1977-07-01
A particle simulation model which treats the wave excitation and propagation in the nonuniform density by the external source is developed and applied for study of the lower hybrid heating in a fusion device. As the linear theory predicts, the cold lower hybrid wave is observed to increase its perpendicular wave number as it propagates to the higher density region and to damp away near the turning point. When the wave amplitude is large or the wave energy is about a half of the initial kinetic energy at a surface of plasma, the following features are observed for the increase of the ion and electron kinetic energies. Ion perpendicular energy distributions are observed to be approximated by the two Maxwell distributions or to have the components of the high energy tail, whose parallel velocities satisfy the resonance condition: νparallel = (ω-IOTAΩ sub(iota))/kappa parallel, where ω and kappa parallel the frequency and the parallel wave number of the external source, IOTA is an integer, and Ω sub(iota) is the ion cyclotron frequency. An strong increase of the parallel kinetic energy of the electron is observed near the plasma surface. These are mainly due to the trapped electrons and the collisional heating. (auth.)
International Nuclear Information System (INIS)
Misguich, J.H.
2004-04-01
As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation
Energy Technology Data Exchange (ETDEWEB)
Misguich, J.H
2004-04-01
As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation.
Control of radial propagation and polarity in a plasma jet in surrounding Ar
Gong, W.; Yue, Y.; Ma, F.; Yu, F.; Wan, J.; Nie, L.; Bazaka, K.; Xian, Y.; Lu, X.; Ostrikov, K.
2018-01-01
In recent years, the use of shielding gas to prevent the diffusion of the ambient air, particularly oxygen and nitrogen species, into the effluent of the atmospheric pressure plasma jet, and thus control the nature of chemical species used
Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma
International Nuclear Information System (INIS)
Ogino, Yousuke; Sawada, Keisuke; Ohnishi, Naofumi
2008-01-01
Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies
A numerical analysis of high power laser propagation in magnetized plasmas
International Nuclear Information System (INIS)
Druce, R.L.; Kristiansen, M.; Hagler, M.O.
1977-01-01
The laser-plasma interaction is studied mathematically by partial differential equations describing plasma momentum, energy transfer and the wave equations for the laser beam. A computer code is developed to solve the equations. The code is used to study two problems of interest : a preliminary parameter study of bleaching wave behaviour and a comparison with experimental results obtained in previous laboratory investigations. Comparison of prediction by calculation with experiment is found to be good. (A.K.)
Nonlinear propagation of an elliptically shaped Gaussian laser beam in an overdense plasma
Energy Technology Data Exchange (ETDEWEB)
Nayyar, V P; Soni, V S [Punjabi Univ., Patiala (India). Dept. of Physics
1979-04-01
The self-focusing and self defocusing of an elliptically shaped high power laser beam in an extradense plasma is discussed. On account of the ponderomotive force induced by the spatial variation of irradiance in the transverse plane, an electron density gradient is created in the overdense plasma where the beam can penetrate. Self-focusing of the beam in the x and y directions for different critical powers has been extensively studied.
Propagation and diffusion of a plasma column in a magnetic field
International Nuclear Information System (INIS)
Bottiglioni, F.; Coutant, J.; Gadda, E.; Prevot, F.
1966-12-01
A plasma column is created in a magnetic field by longitudinal diffusion from a low-pressure pulsed discharge in hydrogen. Depending on the discharge conditions, two regimes are obtained in which the gas pumping speed has a different effect upon the plasma density in the column. Calculations are presented which can explain this effect by a difference in the transverse diffusion coefficient. (authors) [fr
Seepersad, Yohan
The state of plasma is widely known as a gas-phase phenomenon, but plasma in liquids have also received significant attention over the last century. Generating plasma in liquids however is theoretically challenging, and this problem is often overcome via liquid-gas phase transition preceding the actual plasma formation. In this sense, plasma forms in gas bubbles in the liquid. Recent work at the Drexel Plasma Institute has shown that nanosecond pulsed electric fields can initiate plasma in liquids without any initial cavitation phase, at voltages below theoretical direct-ionization thresholds. This unique regime is poorly understood and does not fit into any current descriptive mechanisms. As with all new phenomena, a complete fundamental description is paramount to understanding its usefulness to practical applications. The primary goals of this research were to qualitatively and quantitatively understand the phenomenon of nanosecond pulsed discharge in liquids as a means to characterizing properties that may open up niche application possibilities. Analysis of the plasma was based on experimental results from non-invasive, sub-nanosecond time-resolved optical diagnostics, including direct imaging, transmission imaging (Schlieren and shadow), and optical emission spectroscopy. The physical characteristics of the plasma were studied as a function of variations in the electric field amplitude and polarity, liquid permittivity, and pulse duration. It was found that the plasma size and emission intensity was dependent on the permittivity of the liquid, as well as the voltage polarity, and the structure and dynamics were explained by a 'cold-lightning' mechanism. The under-breakdown dynamics at the liquid-electrode interface were investigated by transmission imaging to provide evidence for a novel mechanism for initiation based on the electrostriction. This mechanism was proposed by collaborators on the project and developed alongside the experimental work in this
The propagation property of ion-acoustic soliton in an inhomogeneous plasma
International Nuclear Information System (INIS)
Zhu Jiazhen; Wang Gengguo.
1990-01-01
The propagation property of ion-acoustic soliton in a weakly inhomogeneous plamsa caused by ionization is studied. Finite ion temperature and ion-neutral collisions are considered the self consistent stationary distribution N(x), v(x) and the corresponding soliton solution are obtained, numerical results of soliton amplitude, speed and width dependent on position are given, which are reasonable and consistent with experiments
International Nuclear Information System (INIS)
Xu, Siyao; Yan, Huirong; Lazarian, A.
2016-01-01
We study the damping processes of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in a partially ionized medium. We start from the linear analysis of MHD waves, applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and the cutoff boundary of linear MHD waves is investigated. We find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow MHD turbulence, and offer a thorough discussion of their propagation and dissipation behavior. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and the solar chromosphere. The importance of neutral viscosity in damping the Alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. As a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified.
Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance
International Nuclear Information System (INIS)
Erfani, Rasool; Zare-Behtash, Hossein; Kontis, Konstantinos
2012-01-01
Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma. (paper)
Propagation of laser-generated plasma jet in an ambient medium
International Nuclear Information System (INIS)
Loupias, B; Falize, E; Vinci, T; Bouquet, S; Gregory, C D; Koenig, M; Ravasio, A; Pikuz, S; Waugh, J; Woolsey, N C; Nazarov, W; Michaut, C; Kuramitsu, Y; Seiichi, D; Sakawa, Y; Takabe, H; Schiavi, A; Atzeni, S
2009-01-01
In this work we present experimental research related to laboratory astrophysics using an intense laser. The goal of these experiments is to investigate some of the complex features of young stellar objects and astrophysical outflows, in particular the plasma jet interaction with the interstellar medium. The relevance of these experiments to astrophysics is measured through similarity criteria (scaling laws). These ensure the similarity between the astrophysical object and the laboratory provided that the dimensionless numbers are equivalent. Consequently, measurements of the plasma parameters are crucial to link laboratory research to astrophysics as they are needed for the determination of these dimensionless numbers. In this context, we designed experiments to generate plasma jets using an intense laser, and to study the evolution in vacuum and in an ambient medium.
Laser pulse propagation and enhanced energy coupling to fast electrons in dense plasma gradients
International Nuclear Information System (INIS)
Gray, R J; Carroll, D C; Yuan, X H; Brenner, C M; Coury, M; Quinn, M N; Tresca, O; McKenna, P; Burza, M; Wahlström, C-G; Lancaster, K L; Neely, D; Lin, X X; Li, Y T
2014-01-01
Laser energy absorption to fast electrons during the interaction of an ultra-intense (10 20 W cm −2 ), picosecond laser pulse with a solid is investigated, experimentally and numerically, as a function of the plasma density scale length at the irradiated surface. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient. (paper)
Propagation of Polarized Cosmic Microwave Background Radiation in an Anisotropic Magnetized Plasma
International Nuclear Information System (INIS)
Moskaliuk, S. S.
2010-01-01
The polarization plane of the cosmic microwave background radiation (CMBR) can be rotated either in a space-time with metric of anisotropic type and in a magnetized plasma or in the presence of a quintessential background with pseudoscalar coupling to electromagnetism. A unified treatment of these three phenomena is presented for cold anisotropic plasma at the pre-recombination epoch. It is argued that the generalized expressions derived in the present study may be relevant for direct searches of a possible rotation of the cosmic microwave background polarization.
Tokluoglu, Erinc K.; Kaganovich, Igor D.; Carlsson, Johan A.; Hara, Kentaro; Startsev, Edward A.
2018-05-01
Propagation of charged particle beams in background plasma as a method of space charge neutralization has been shown to achieve a high degree of charge and current neutralization and therefore enables nearly ballistic propagation and focusing of charged particle beams. Correspondingly, the use of plasmas for propagation of charged particle beams has important applications for transport and focusing of intense particle beams in inertial fusion and high energy density laboratory plasma physics. However, the streaming of beam ions through a background plasma can lead to the development of two-stream instability between the beam ions and the plasma electrons. The beam electric and magnetic fields enhanced by the two-stream instability can lead to defocusing of the ion beam. Using particle-in-cell simulations, we study the scaling of the instability-driven self-electromagnetic fields and consequent defocusing forces with the background plasma density and beam ion mass. We identify plasma parameters where the defocusing forces can be reduced.
An axially propagating two-stream instability in the Hall thruster plasma
Czech Academy of Sciences Publication Activity Database
Tsikata, S.; Cavalier, Jordan; Héron, A.; Honore, C.; Lemoine, N.; Gresillon, D.; Coulette, D.
2014-01-01
Roč. 21, č. 7 (2014), 072116-072116 ISSN 1070-664X Institutional support: RVO:61389021 Keywords : Collective Thomson scattering * Hall thruster * kinetic theory * electrostatic modes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.142, year: 2014 http://dx.doi.org/10.1063/1.4890025
International Nuclear Information System (INIS)
Jacquot, J; Colas, L; Clairet, F; Goniche, M; Hillairet, J; Lombard, G; Heuraux, S; Milanesio, D
2013-01-01
A novel method to simulate ion cyclotron wave coupling in the edge of a tokamak plasma with the finite element technique is presented. It is applied in the commercial software COMSOL Multiphysics. Its main features include the perfectly matched layer (PML) technique to emulate radiating boundary conditions beyond a critical cutoff layer for the fast wave (FW), full-wave propagation across the inhomogeneous cold peripheral plasma and a detailed description of the wave launcher geometry. The PML technique, while widely used in numerical simulations of wave propagation, has scarcely been used for magnetized plasmas, due to specificities of this gyrotropic material. A versatile PML formulation, valid for full dielectric tensors, is summarized and interpreted as wave propagation in an artificial medium. The behavior of this technique has been checked for plane waves on homogeneous plasmas. Wave reflection has been quantified and compared to analytical predictions. An incompatibility issue for adapting the PML for forward (FW) and backward (slow wave (SW)) propagating waves simultaneously has been evidenced. In a tokamak plasma, this critical issue is overcome by taking advantage of the inhomogeneous density profile to reflect the SW before it reaches the PML. The simulated coupling properties of a Tore Supra ion cyclotron resonance heating (ICRH) antenna have been compared to experimental values in a situation of good single-pass absorption. The necessary antenna elements to include in the geometry to recover the coupling properties obtained experimentally are also discussed. (paper)
Directory of Open Access Journals (Sweden)
Y. Narita
2004-07-01
Full Text Available We statistically study various properties of low-frequency waves such as frequencies, wave numbers, phase velocities, and polarization in the plasma rest frame in the terrestrial foreshock. Using Cluster observations the wave telescope or k-filtering is applied to investigate wave numbers and rest frame frequencies. We find that most of the foreshock waves propagate upstream along the magnetic field at phase velocity close to the Alfvén velocity. We identify that frequencies are around 0.1xΩcp and wave numbers are around 0.1xΩcp/VA, where Ωcp is the proton cyclotron frequency and VA is the Alfvén velocity. Our results confirm the conclusions drawn from ISEE observations and strongly support the existence of Alfvén waves in the foreshock.
Rankin, R.; Sydorenko, D.
2015-12-01
Results from a 3D global numerical model of Alfven wave propagation in a warm multi-species plasma in Earth's magnetosphere are presented. The model uses spherical coordinates, accounts for a non-dipole magnetic field, vertical structure of the ionosphere, and an air gap below the ionosphere. A realistic density model is used. Below the exobase altitude (2000 km) the densities and the temperatures of electrons, ions, and neutrals are obtained from the IRI and MSIS models. Above the exobase, ballistic (originating from the ionosphere and returning to ionosphere) and trapped (bouncing between two reflection points above the ionosphere) electron populations are considered similar to [Pierrard and Stegen (2008), JGR, v.113, A10209]. Plasma parameters at the exobase provided by the IRI are the boundary conditions for the ballistic electrons while the [Carpenter and Anderson (1992), JGR, v.97, p.1097] model of equatorial electron density defines parameters of the trapped electron population. In the simulations that are presented, Alfven waves with frequencies from 1 Hz to 0.01 Hz and finite azimuthal wavenumbers are excited in the magnetosphere and compared with Van Allen Probes data and ground-based observations from the CARISMA array of ground magnetometers. When short perpendicular scale waves reflect form the ionosphere, compressional Alfven waves are observed to propagate across the geomagnetic field in the ionospheric waveguide [e.g., Lysak (1999), JGR, v.104, p.10017]. Signals produced by the waves on the ground are discussed. The wave model is also applied to interpret recent Van Allen Probes observations of kinetic scale ULF waves that are associated with radiation belt electron dynamics and energetic particle injections.
Cosmic-ray shock acceleration in oblique MHD shocks
Webb, G. M.; Drury, L. OC.; Volk, H. J.
1986-01-01
A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.
Oblique whistler instability in the earth's foreshock
International Nuclear Information System (INIS)
Sentman, D.D.; Thomsen, M.F.; Gary, S.P.; Feldman, W.C.; Hoppe, M.M.
1983-01-01
The linear Vlasov stability properties of electron velocity distributions, similar to those observed in the upstream foreshock region in association with obliquely propagating whistler waves at approximately 1 Hz, are studied. These distributions are modeled by a sum of bi-Maxwellians with drift speeds parallel to the magnetic field B. We find such distributions to be stable to modes with wavevectors k parallel to B but unstable to whistler waves propagating obliquely to the magnetic field. The frequencies and wavelengths of these unstable modes agree well with those of whistlers observed upstream of the earth's bow shock. The free energy source driving the instability is a region of positive parallel slope partialf/sub e//partialv/sub parallel/>0 at large pitch angles (about 85 0 ) and intermediate energies (about 20 eV), probably corresponding to the solar wind electrons magnetostatically reflected from the magnetic ramp of the bow shock. The whistlers grow via electromagnetic Landau resonance with this free energy source
Energy Technology Data Exchange (ETDEWEB)
Maneva, Y. G.; Poedts, Stefaan [Centre for Mathematical Plasma Astrophysics, KU Leuven, B-3001 Leuven (Belgium); Viñas, Adolfo F.; Moya, Pablo S.; Wicks, Robert T., E-mail: yana.maneva@wis.kuleuven.be [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2015-11-20
We perform 2.5D hybrid simulations with massless fluid electrons and kinetic particle-in-cell ions to study the temporal evolution of ion temperatures, temperature anisotropies, and velocity distribution functions in relation to the dissipation and turbulent evolution of a broadband spectrum of parallel and obliquely propagating Alfvén-cyclotron waves. The purpose of this paper is to study the relative role of parallel versus oblique Alfvén-cyclotron waves in the observed heating and acceleration of alpha particles in the fast solar wind. We consider collisionless homogeneous multi-species plasma, consisting of isothermal electrons, isotropic protons, and a minor component of drifting α particles in a finite-β fast stream near the Earth. The kinetic ions are modeled by initially isotropic Maxwellian velocity distribution functions, which develop nonthermal features and temperature anisotropies when a broadband spectrum of low-frequency nonresonant, ω ≤ 0.34 Ω{sub p}, Alfvén-cyclotron waves is imposed at the beginning of the simulations. The initial plasma parameter values, such as ion density, temperatures, and relative drift speeds, are supplied by fast solar wind observations made by the Wind spacecraft at 1 AU. The imposed broadband wave spectra are left-hand polarized and resemble Wind measurements of Alfvénic turbulence in the solar wind. The imposed magnetic field fluctuations for all cases are within the inertial range of the solar wind turbulence and have a Kraichnan-type spectral slope α = −3/2. We vary the propagation angle from θ = 0° to θ = 30° and θ = 60°, and find that the heating of alpha particles is most efficient for the highly oblique waves propagating at 60°, whereas the protons exhibit perpendicular cooling at all propagation angles.
International Nuclear Information System (INIS)
Maneva, Y. G.; Poedts, Stefaan; Viñas, Adolfo F.; Moya, Pablo S.; Wicks, Robert T.
2015-01-01
We perform 2.5D hybrid simulations with massless fluid electrons and kinetic particle-in-cell ions to study the temporal evolution of ion temperatures, temperature anisotropies, and velocity distribution functions in relation to the dissipation and turbulent evolution of a broadband spectrum of parallel and obliquely propagating Alfvén-cyclotron waves. The purpose of this paper is to study the relative role of parallel versus oblique Alfvén-cyclotron waves in the observed heating and acceleration of alpha particles in the fast solar wind. We consider collisionless homogeneous multi-species plasma, consisting of isothermal electrons, isotropic protons, and a minor component of drifting α particles in a finite-β fast stream near the Earth. The kinetic ions are modeled by initially isotropic Maxwellian velocity distribution functions, which develop nonthermal features and temperature anisotropies when a broadband spectrum of low-frequency nonresonant, ω ≤ 0.34 Ω p , Alfvén-cyclotron waves is imposed at the beginning of the simulations. The initial plasma parameter values, such as ion density, temperatures, and relative drift speeds, are supplied by fast solar wind observations made by the Wind spacecraft at 1 AU. The imposed broadband wave spectra are left-hand polarized and resemble Wind measurements of Alfvénic turbulence in the solar wind. The imposed magnetic field fluctuations for all cases are within the inertial range of the solar wind turbulence and have a Kraichnan-type spectral slope α = −3/2. We vary the propagation angle from θ = 0° to θ = 30° and θ = 60°, and find that the heating of alpha particles is most efficient for the highly oblique waves propagating at 60°, whereas the protons exhibit perpendicular cooling at all propagation angles
Effect of ion composition on oblique magnetosonic waves
International Nuclear Information System (INIS)
Kondo, Yuichi; Toida, Mieko
2011-01-01
The effects of ion composition on oblique magnetosonic waves in a two-ion-species plasma are studied theoretically and numerically. First, it is analytically shown that the KdV equation for the low-frequency mode, the lower branch of magnetosonic waves, is valid for amplitudes ε max (l-) , where ε max (l-) is a measure of the upper limit of the amplitude of the rarefactive solitary pulse of the low-frequency mode and is given as a function of the propagation angle of the wave θ, the density ratio and cyclotron frequency ratio of two ion species. The value of ε max (l-) increases with decreasing θ. Next, with electromagnetic particle simulations, the nonlinear evolution of the low- and high-frequency modes is examined. It is demonstrated that shorter-wavelength low- and high-frequency-mode waves are generated from a long-wavelength low-frequency-mode pulse if its amplitude ε exceeds ε max (l-) . (author)
Mosavi, N.; Sequeira, H.; Copeland, D.; Menyuk, C.
2017-12-01
We investigate the evolution of a radio frequency (RF) X-band signal as it propagates through the solar corona turbulence in superior solar conjunction at low Sun-Earth-Probe (SEP) angles.Data that was obtained during several MESSENGER (MErcury Surface, Space ENivornment, GEochmeisty, and Ranging) conjunctions reveal a short-term and long-term effect. Amplitude scintillation is evident on a short time scale. Phase scintillations are stronger, but occur over a longer time scale. We examine different possible phenomena in the solar plasma that could be the source of the different time scales of the amplitude and phase scintillations. We propose a theoretical model in which the amplitude scintillations are due to local fluctuations of the index of refraction that scatter the RF signal. These rapidly varying fluctuations randomly attenuate the signal without affecting its phase. By contrast, we propose a model in which phase fluctuations are due to long ducts in the solar plasma, streaming from the sun, that trap some parts of the RF signal. These ducts act as waveguides, changing the phase velocity of the RF beam as it travels a zigzag path inside a duct. When the radiated wave exits from a duct, its phase is changed with respect to the signal that did not pass through the duct, which can lead to destructive interference and carrier suppression. The trapping of the wave is random in nature and can be either a fast or slow process. The predictions of this model are consistent with observations.
On the control of filamentation of intense laser beams propagating in underdense plasma
International Nuclear Information System (INIS)
Williams, E.A.
2006-01-01
In indirect drive inertial confinement fusion ignition designs, the laser energy is delivered into the hohlraum through the laser entrance holes (LEHs), which are sized as small as practicable to minimize x-ray radiation losses. On the other hand, deleterious laser plasma processes, such as filamentation and stimulated backscatter, typically increase with laser intensity. Ideally, therefore, the laser spot shape should be a close fit to the LEH, with uniform (envelope) intensity in the spot and minimal energy at larger radii spilling onto the LEH material. This keeps the laser intensity as low as possible, consistent with the area of the LEH aperture and the power requirements of the design. This can be achieved (at least for apertures significantly larger than the laser's aberrated focal spot) by the use of custom-designed phase plates. However, outfitting the 192-beam National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Tech. 26, 755 1994)] laser with multiple sets of phase plates optimized for a variety of different LEH aperture sizes is an expensive proposition. It is thus important to assess the impact on laser-plasma interaction processes of using phase plates with a smaller than optimum focal spot (or even no phase plates at all!) and then defocusing the beam to expand it to fill the LEH and lower its intensity. Significant effects are found from changes in the characteristic sizes of the laser speckle, from the lack of uniformity of the laser envelope out of the focal plane and on the efficacy of additional polarization smoothing and/or smoothing by spectral dispersion (SSD). These effects are quantified with analytic estimates and simulations using PF3D, our laser-plasma interaction code
International Nuclear Information System (INIS)
Najmudin, Z.; Krushelnick, K.; Tatarakis, M.; Clark, E.L.; Danson, C.N.; Malka, V.; Neely, D.; Santala, M.I.K.; Dangor, A.E.
2003-01-01
Experiments have been performed using high power laser pulses (up to 50 TW) focused into underdense helium plasmas (n e ≤5x10 19 cm -3 ). Using shadowgraphy, it is observed that the laser pulse can produce irregular density channels, which exhibit features such as long wavelength hosing and 'sausage-like' self-focusing instabilities. This phenomenon is a high intensity effect and the characteristic period of oscillation of these instabilities is typically found to correspond to the time required for ions to move radially out of the region of highest intensity
International Nuclear Information System (INIS)
Gyergyek, T.; Kovačič, J.
2015-01-01
A one-dimensional fluid model of the magnetized plasma-wall transition region in front of a floating electrode immersed in a magnetized plasma with oblique magnetic field is presented. The Boltzmann relation is assumed for the electrons, while the positive ions obey the ion continuity and momentum exchange equation. The ions are assumed to be isothermal. By comparison with a two-fluid model, it is shown that assuming the Boltzmann relation for the electrons implies that there is no creation or annihilation of the electrons. Consequently, there should not be any creation and annihilation of the positive ions either. The models that assume the Boltzmann relation for the electrons and a non-zero ion source term at the same time are therefore inconsistent, but such models have nevertheless been used extensively by many authors. So, in this work, an extensive comparison of the results obtained using the zero source term on one hand and three different non-zero source terms on the other hand is made. Four different ion source terms are considered in total: the zero source term and three different non-zero ion source terms. When the zero source term is used, the model becomes very sensitive to the boundary conditions, and in some cases, the solutions exhibit large amplitude oscillations. If any of the three non-zero ion source terms is used, those problems are eliminated, but also the consistency of the model is broken. The model equations are solved numerically in the entire magnetized plasma-wall transition region. For zero ion temperature, the model can be solved even if a very small ion velocity is selected as a boundary condition. For finite ion temperature, the system of equations becomes stiff, unless the ion velocity at the boundary is increased slightly above the ion thermal velocity. A simple method how to find a solution with a very small ion velocity at the boundary also for finite ion temperature in the entire magnetized plasma-wall transition region is
Collisional effects in the ion Weibel instability for two counter-propagating plasma streams
Energy Technology Data Exchange (ETDEWEB)
Ryutov, D. D.; Fiuza, F.; Huntington, C. M.; Ross, J. S.; Park, H.-S. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2014-03-15
Experiments directed towards the study of the collisionless interaction between two counter-streaming plasma flows generated by high-power lasers are designed in such a way as to make collisions between the ions of the two flows negligibly rare. This is reached by making flow velocities v as high as possible and thereby exploiting the 1/v{sup 4} dependence of the Rutherford cross-section. At the same time, the plasma temperature of each flow may be relatively low so that collisional mean-free paths for the intra-stream particle collisions may be much smaller than the characteristic spatial scale of the unstable modes required for the shock formation. The corresponding effects are studied in this paper for the case of the ion Weibel (filamentation) instability. Dispersion relations for the case of strong intra-stream collisions are derived. It is shown that the growth-rates become significantly smaller than those stemming from a collisionless model. The underlying physics is mostly related to the increase of the electron stabilizing term. Additional effects are an increased “stiffness” of the collisional ion gas and the ion viscous dissipation. A parameter domain where collisions are important is identified.
The role of plasma instabilities in the propagation of gamma-rays from distant Blazars
Energy Technology Data Exchange (ETDEWEB)
Saveliev, A.; Evoli, C.; Sigl, G. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2013-11-15
The observation in the GeV band of distant blazars has been recently used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Fields (EGMF). To support such claims one has to assume that the leptonic component of the electromagnetic cascade initiated by blazar gamma-rays is deflected away by strong enough EGMF, suppressing the signal in the Fermi window. Apart from magnetic fields, the development of such a cascade might be affected by plasma instabilities due to interactions with the ionized component of the Intergalactic Medium (IGM). In this paper we model the electromagnetic cascade through a Monte Carlo simulation in which both effects are taken into account separately, and we derive constraints on these scenarios from the combined Fermi-HESS data set. In the specific case of 1ES 0229+200 observations, we show that both explanations of the GeV flux suppression are compatible with the available data, specifically by assuming a magnetic field of B >or similar 10{sup -16} G or an IGM temperature of T
Kinetic effects in the propagation of ion-acoustic negative solitons in plasmas with negative ions
International Nuclear Information System (INIS)
Roberto, M.
1986-12-01
The existence of ion-acoustic negative (rarefactive) solitons in plasmas was experimentally verified and explained by means of the Korteweg-de Vries equation, obtained from a fluid model. The experimental results obtained in a double-plasma machine of the Institute for Space Research, however, have provided values of Mach number larger than predicted by this simple model. In order to improve the analysis of the phenomenon, Kinetic effects resultant from the occurrence of reflected electrons and trapped ions in the soliton potential were considered, using the theory of Sagdeev potential. For the description of the negative ion dynamics the fluid model treatment was preserved. It was verified that the effects of the finite temperature and trapping of the positive ions modify the results predicted by the simple KdV model in such a way that the Mach number is reduced as the ion temperature increases. It was shown that reflection of electrons is consistent with the large experimental values of Mach number. (Author) [pt
The launching and propagation of drift waves in a steady-state plasma
International Nuclear Information System (INIS)
Sandeman, J.; Elliott, J.A.; Sutcliffe, M.; Rusbridge, M.G.
1992-01-01
The UMIST linear quadrupole GOLUX is a steady-state device in which hydrogen plasma is continuously injected axially, at one end, from an external duoplasmatron source. The electron temperature in the drift wave region is about 1 eV, and the density about 10 15 m -3 . Self-excited intrinsic drift modes are observed in the shared flux region of GOLUX, forming a broad band between 30 and 50 kHz. Drift waves may also be launched into the system, by passing an AC current through the plasma between the two flag antennae. These coherent launched waves present a powerful means of studying drift wave phenomena. We obtain information about the launched wave by detecting both density and potential fluctuations, using a small cylindrical Langmuir probe and lock-in amplifier techniques. Scanning the probe in the longitudinal (z) direction yields the spatial variation of amplitude and phase with respect to the launching signal; the ratio of the wave potential, extrapolated back to the probe, to the launching current gives the launching impedance, a measure of the effectiveness of the launching process. (author) 5 refs., 6 figs
International Nuclear Information System (INIS)
Imbeaux, F.
1999-01-01
Control of the current density profile is a critical issue in view to obtain high fusion performances in tokamak plasmas? It is therefore important to be able to control the power deposition profile of the lower hybrid wave, which has the highest current drive efficiency among all other non-inductive additional methods. Propagation and absorption of this wave are investigated in the Tore Supra tokamak using a new hard x-ray tomographic system and a new ray-tracing/Fokker-Planck code. These tools are described in detail and allow to analyse the lower hybrid power deposition profile dependence as a function of various plasma parameters (density, magnetic field, current) and of the injected wave spectrum. A good agreement between the code and the measurements found when the central electron temperature is greater than about 3 keV, that is in regimes where the wave undergoes only a few reflections before being absorbed. The simulations are then used to interpret the experimental trends. The lower hybrid power deposition profile is in nearly all discharges localised at a normalised minor radius of 0.2-0.3, and is weakly sensitive to variations of plasma parameters. It is hence difficult to perform an efficient control of the current profile generated by the lower hybrid wave in Tore Supra. This goal may nevertheless be reached by using an original method, which uses an auxiliary lower hybrid wave injected by a vertical port of the torus. This method is investigated by means of the simulation code. (author)
Study of linear and non-linear waves propagation. Application to fluid mechanics and plasmas physics
International Nuclear Information System (INIS)
Forestier, A.
2002-01-01
This contribution's topic is the resolution of the hyperbolic system which describes a compressible flow in perfect or real situation. It is always in a compressible case and a turbulent model or a multicomponent isentropic turbulent model can be associated. Different schemes are tested as S α β scheme or TVD scheme. An extension to generalized geometry is purposed in 2D or 3D. For chemical aspects, the ZND theory is under control with connexion of second order method. In the same way, MHD or Turbulent problem are developed with computations for compressible situation. Implicit aspects are investigated that show the lost of knowledge in large CFL even if computation can be driven for all time step. At the end, for Plasma situations in which pressure effects can be neglected, there is a lost of hyperbolicity that requires investigation in generated problems. We don't present numerical simulations that are exhibited in an other paper. (author)
Wave trajectory and electron cyclotron heating in toroidal plasmas
International Nuclear Information System (INIS)
Maekawa, T.; Tanaka, S.; Terumichi, Y.; Hamada, Y.
1977-12-01
Wave trajectories propagating obliquely to magnetic field in toroidal plasmas are studied theoretically. Results show that the ordinary wave at appropriate incident angle is mode-converted to the extraordinary wave at first turning point and is further converted to the electron Bernstein wave during passing a loop or a hooked nail curve near second turning point and is cyclotron-damped away, resulting in local electron heating, before arriving at cyclotron resonance layer. (auth.)
Gyrokinetic approach to the propagation of electromagnetic waves in nonuniform bounded plasma slabs
International Nuclear Information System (INIS)
Sauter, O.; Vaclavik, J.
1994-05-01
A new code, SEMAL, has been developed which solves the linearized Vlasov-Maxwell wave equations to all orders in Larmor radii. Arbitrary density and temperature profiles as well as nonuniform magnetic fields are considered in slab geometry. The vacuum regions adjacent to the plasma slab are limited by perfect conducting walls and contain an antenna as an excitation source. The linear response is obtained by solving the system of one first-order and two second-order integro-differential equations using a non-polluting finite element discretization. The general equations in the Fourier space, derived in a new comprehensive way, and their inverse transform, using k y =0, are described as well as the convergence and non-polluting properties of the method. We present the results concerning the influence of alpha particles on ICRF heating schemes for ITER, where we show that small alphas concentration can alter the steady-state operation envisaged with ICRF fast wave current-drive. (author) 7 figs., 3 tabs., 28 refs
International Nuclear Information System (INIS)
Weng, S M; Murakami, M; Mulser, P; Sheng, Z M
2012-01-01
Relativistic laser pulse propagation into homogeneous plasmas has been investigated as a function of plasma density. At first, the propagation features are compared systematically between relativistic transparency (RT) and hole-boring (HB). Paramountly, a considerably broad intermediate regime, namely the incomplete HB regime, has been found between the RT regime and the HB regime for an extremely intense circularly polarized (CP) pulse. In this regime HB proceeds in collaboration with RT, resulting in a much faster propagation speed and a higher cut-off energy of fast ions than in the classic HB regime. Similarly to the classic HB regime, formulae are presented to model the laser propagation and the ion acceleration according to the modified momentum flux balance in this incomplete HB regime. The simulations give the density boundary between this incomplete HB regime and the classic HB regime for CP pulses, which is crucial for estimating the maximum mean ion energy and the maximum conversion efficiency that can be achieved by the classic HB acceleration at a given laser intensity. For linear polarization (LP) the propagation mechanism apparently undergoes a transition in time between these two regimes. A detailed comparison between LP and circular polarization is made for these phenomena. (paper)
Assessment Of An Oblique ECE Diagnostic For ITER
International Nuclear Information System (INIS)
Taylor, G.; Harvey, R.W.
2009-01-01
A systematic disagreement between the electron temperature measured by electron cyclotron emission (TECE) and laser Thomson scattering (TTS), that increases with TECE, is observed in JET and TFTR plasmas, such that TECE ∼1.2 TTS when TECE ∼10 keV. The disagreement is consistent with a non-Maxwellian distortion in the bulk electron momentum distribution. ITER is projected to operate with Te(0) ∼ 20-40 keV so the disagreement between TECE and TTS could be > 50%, with significant physics implications. The GENRAY ray tracing code predicts that a two-view ECE system, with perpendicular and moderately oblique viewing antennas, would be sufficient to reconstruct a two-temperature bulk distribution. If the electron momentum distribution remains Maxwellian the moderately oblique view could still be used to measure Te(R). A viewing dump will not be required for the oblique view and plasma refraction will be minimal. The oblique view has a similar radial resolution to the perpendicular view, but with some reduction in radial coverage. Oblique viewing angles of up to 20 o can be implemented without a major revision to the front end of the existing ITER ECE diagnostic design.
Energy Technology Data Exchange (ETDEWEB)
Jovanović, Dušan, E-mail: dusan.jovanovic@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Zemun (Serbia); Fedele, Renato, E-mail: renato.fedele@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II,” M.S. Angelo, Napoli (Italy); INFN Sezione di Napoli, Complesso Universitario di M.S. Angelo, Napoli (Italy); Belić, Milivoj, E-mail: milivoj.belic@qatar.tamu.edu [Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); De Nicola, Sergio, E-mail: sergio.denicola@spin.cnr.it [SPIN-CNR, Complesso Universitario di M.S. Angelo, Napoli (Italy)
2015-04-15
The interaction of a multi-petawatt, pancake-shaped laser pulse with an unmagnetized plasma is studied analytically and numerically in a regime with ultrarelativistic electron jitter velocities, in which the plasma electrons are almost completely expelled from the pulse region. The study is applied to a laser wakefield acceleration scheme with specifications that may be available in the next generation of Ti:Sa lasers and with the use of recently developed pulse compression techniques. A set of novel nonlinear equations is derived using a three-timescale description, with an intermediate timescale associated with the nonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. They describe, on an equal footing, both the strong and the moderate laser intensity regimes, pertinent to the core and to the edges of the pulse. These have fundamentally different dispersive properties since in the core the electrons are almost completely expelled by a very strong ponderomotive force, and the electromagnetic wave packet is imbedded in a vacuum channel, thus having (almost) linear properties. Conversely, at the pulse edges, the laser amplitude is smaller, and the wave is weakly nonlinear and dispersive. New nonlinear terms in the wave equation, introduced by the nonlinear phase, describe without the violation of imposed scaling laws a smooth transition to a nondispersive electromagnetic wave at very large intensities and a simultaneous saturation of the (initially cubic) nonlocal nonlinearity. The temporal evolution of the laser pulse is studied both analytically and by numerically solving the model equations in a two-dimensional geometry, with the spot diameter presently used in some laser acceleration experiments. The most stable initial pulse length is estimated to exceed ≳1.5–2 μm. Moderate stretching of the pulse in the direction of propagation is observed, followed by the development of a vacuum channel and of a very large
International Nuclear Information System (INIS)
Ghalambor Dezfuly, S.; Dorranian, D.
2012-01-01
In this manuscript, the effect of dust electrical charge, nonthermal ions, and external magnetic field on the shape and propagation of solitons in dusty plasma with two nonthermal ions is studied theoretically. Using the reductive perturbation theory, the Zakharov-Kuznetsov equation for propagation of dust acoustic waves is extracted. Results show that external magnetic field does not affect the amplitude of solitary wave but width of solitons are effectively depend on the magnitude of external magnetic field. With increasing the charge of dust particles the amplitude of solution will increase while their width will decrease. Increasing the nonthermal ions lead to opposite effect.
Directory of Open Access Journals (Sweden)
Y. Narita
2004-07-01
Full Text Available We statistically study various properties of low-frequency waves such as frequencies, wave numbers, phase velocities, and polarization in the plasma rest frame in the terrestrial foreshock. Using Cluster observations the wave telescope or k-filtering is applied to investigate wave numbers and rest frame frequencies. We find that most of the foreshock waves propagate upstream along the magnetic field at phase velocity close to the Alfvén velocity. We identify that frequencies are around 0.1xΩ_{cp} and wave numbers are around 0.1xΩ_{cp}/V_{A}, where Ω_{cp} is the proton cyclotron frequency and V_{A} is the Alfvén velocity. Our results confirm the conclusions drawn from ISEE observations and strongly support the existence of Alfvén waves in the foreshock.
International Nuclear Information System (INIS)
Deeba, F.; Ahmad, Zahoor; Murtaza, G.
2006-01-01
The electrostatic potentials (Debye and wake) and energy loss due to a charged projectile propagating through an unmagnetized collisionless dusty plasma are derived employing kappa and generalized (r,q) velocity distributions for the dust acoustic wave. It is found that these quantities in general differ from their Maxwellian counterparts and are sensitive to the values of spectral index, κ in the case of kappa distribution and to r, q in the case of generalized (r,q) distribution. The amplitudes of these quantities are less for small values of the spectral index (κ, r=0, q) but approach the Maxwellian in the limit κ→∞ (for kappa distribution) and for r=0, q→∞ [for generalized (r,q) distribution]. For any nonzero value of r, the potential and the energy loss grow beyond the Maxwellian results. The effect of kappa and generalized (r,q) distributions on potential and energy loss is also studied numerically and the results are compared with those of the Maxwellian distribution
Thermal self-focusing at oblique incidence
International Nuclear Information System (INIS)
Craxton, R.S.; McCrory, R.L.
1984-03-01
Thermal self-focusing at oblique incidence has been investigated in two-dimensional line-focus geometry using the Eulerian hydrodynamics simulation code SAGE. The laser beam interacts with a long-scale-length preformed plasma with an expontial density profiele. Questions to be addressed include: (1) What happens when a self-focusing channel reaches the turning point of the incident rays, and (2) Does the unabsorbed light return in the specular direction or back along the channel. A comparison is also made between thermal self-focusing at normal incidence in cylindrical and line-focus geometries: in cylindrical geometry the self-focusing mechanism is enhanced by the relative ease with which plasma may be expelled from a small cylindrical channel
Ion-acoustic double-layers in a magnetized plasma with nonthermal electrons
Energy Technology Data Exchange (ETDEWEB)
Rios, L. A. [Centro Brasileiro de Pesquisas Físicas and Instituto Nacional de Ciência e Tecnologia de Sistemas Complexos, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro (Brazil); Galvão, R. M. O. [Centro Brasileiro de Pesquisas Físicas and Instituto Nacional de Ciência e Tecnologia de Sistemas Complexos, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro (Brazil); Instituto de Física, Universidade de São Paulo, 05508-900 São Paulo (Brazil)
2013-11-15
In the present work we investigate the existence of obliquely propagating ion-acoustic double layers in magnetized two-electron plasmas. The fluid model is used to describe the ion dynamics, and the hot electron population is modeled via a κ distribution function, which has been proved to be appropriate for modeling non-Maxwellian plasmas. A quasineutral condition is assumed to investigate these nonlinear structures, which leads to the formation of double-layers propagating with slow ion-acoustic velocity. The problem is investigated numerically, and the influence of parameters such as nonthermality is discussed.
Energy Technology Data Exchange (ETDEWEB)
Etemadpour, R.; Dorranian, D., E-mail: doran@srbiau.ac.ir [Laser Laboratory, Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Sepehri Javan, N. [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)
2016-05-15
The nonlinear dynamics of a circularly polarized laser pulse propagating in the magnetized plasmas whose constituents are superthermal ions and mixed nonthermal high-energy tail electrons is studied theoretically. A nonlinear equation which describes the dynamics of the slowly varying amplitude is obtained using a relativistic two-fluid model. Based on this nonlinear equation and taking into account some nonlinear phenomena such as modulational instability, self-focusing and soliton formation are investigated. Effect of the magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons on these phenomena is considered. It is shown that the nonthermality and superthermality of particles can substantially change the nonlinearity of medium.
International Nuclear Information System (INIS)
Etemadpour, R.; Dorranian, D.; Sepehri Javan, N.
2016-01-01
The nonlinear dynamics of a circularly polarized laser pulse propagating in the magnetized plasmas whose constituents are superthermal ions and mixed nonthermal high-energy tail electrons is studied theoretically. A nonlinear equation which describes the dynamics of the slowly varying amplitude is obtained using a relativistic two-fluid model. Based on this nonlinear equation and taking into account some nonlinear phenomena such as modulational instability, self-focusing and soliton formation are investigated. Effect of the magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons on these phenomena is considered. It is shown that the nonthermality and superthermality of particles can substantially change the nonlinearity of medium.
Directory of Open Access Journals (Sweden)
A. N. Afanasiev
2009-10-01
Full Text Available This paper addresses the fine structure of solar decametric type II radio bursts in the form of drifting narrowband fibres on the dynamic spectrum. Observations show that this structure appears in those events where there is a coronal mass ejection (CME traveling in the near-solar space ahead of the shock wave responsible for the radio burst. The diversity in observed morphology of fibres and values of their parameters implies that the fibres may be caused by different formation mechanisms. The burst emission propagates through extremely inhomogeneous plasma of the CME, so one possible mechanism can be related to radio propagation effects. I suggest that the fibres in some events represent traces of radio emission caustics, which are formed due to regular refraction of radio waves on the large-scale inhomogeneous structure of the CME front. To support this hypothesis, I have modeled the propagation of radio waves through inhomogeneous plasma of the CME, taking into consideration the presence of electron density fluctuations in it. The calculations, which are based on the Monte Carlo technique, indicate that, in particular, the emission of the fibres should be harmonic. Moreover, the mechanism under consideration suggests that in solar observations from two different points in space, the observed sets of fibres can be shifted in frequency with respect to one another or can have a different structure. This potentially can be used for identifying fibres caused by the propagation effects.
Electromagnetic Fluctuations during Fast Reconnection in a Laboratory Plasma
International Nuclear Information System (INIS)
Hantao Ji; Stephen Terry; Masaaki Yamada; Russell Kulsrud; Aleksey Kuritsyn; Yang Ren
2003-01-01
Clear evidence for a positive correlation is established between the magnitude of magnetic fluctuations in the lower-hybrid frequency range and enhancement of reconnection rates in a well-controlled laboratory plasma. The fluctuations belong to the right-hand polarized whistler wave branch, propagating obliquely to the reconnecting magnetic field, with a phase velocity comparable to the relative drift velocity between electrons and ions. The short coherence length and large variation along the propagation direction indicate their strongly nonlinear nature in three dimensions
International Nuclear Information System (INIS)
Jacquot, Jonathan
2013-01-01
A correct understanding of the interactions between the edge plasma and the ion cyclotron (IC) waves (40-80 MHz) is needed to inject reliably large amount of power required for self-sustainable fusion plasmas. These thesis objectives were to model separately, with Comsol Multiphysics, but in compatible approaches the wave coupling and the radio-frequency (RF) sheath formation to anticipate development of a single code combining both. Modelling of fast wave coupling requires a detailed description of the antenna (2D or 3D) and of the plasma environment by a full wave approach for a cold plasma. Absorption of outgoing waves is emulated by perfectly matched layers, rendered compatible with a plasma dielectric tensor. Experimental trends for the coupling resistance of the antennas of Tore Supra are qualitatively reproduced but the coupling efficiency is overestimated. In parallel a novel self-consistent description, including RF sheaths, of the interplay between the cold wave propagation and DC biasing of the magnetized edge plasma of a tokamak was developed with the minimum set of physics ingredients. For Tore Supra antenna cases, the code coupled with TOPICA allowed to unveil qualitatively some unexpected observations on the latest design of Tore Supra Faraday screens whose electrical design was supposed to minimize RF sheaths. From simulations, a DC (Direct Current) current transport appears necessary to explain the radial structures of measurements. Cantilevered bars have been identified as the design element in the antenna structure enhancing the plasma potential. (author) [fr
Haixin, HU; Feng, HE; Ping, ZHU; Jiting, OUYANG
2018-05-01
A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.
Arc Motion in an Obliquely Imposed Alternating Magnetic Field
International Nuclear Information System (INIS)
Akiho, R; Takeda, K; Sugimoto, M
2012-01-01
The arc motion is theoretically investigated under an alternating magnetic field imposed obliquely to the arc. The arc is known to oscillate on a 2-D plane when the alternating magnetic field is imposed perpendicularly to the arc. If the alternating magnetic field is imposed obliquely to the arc, then it is expected that the arc oscillates not on the 2-D plane but in a 3-D space. For this study, 3-D simulation was performed on the motion of the plasma gas under an alternating magnetic field crossing obliquely to the arc. It was also assumed that a stream line of the plasma gas represented the arc profile. The momentum equation for the plasma gas was solved together with the continuity equation. Governing parameters for the gas motion are θ (crossing angle), v 0 (initial velocity of the plasma gas), and λ. Parameter λ is defined as λ = (I a B 0 )/Q 0 . Numerical results are reported under different operating conditions such as magnetic flux densities and the angles between the arc and the magnetic flux. If the crossing angle is larger than 4/π, the arc might be extinguished because of the drastic increase of the arc length.
Directory of Open Access Journals (Sweden)
T. R. Robinson
Full Text Available A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.
Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation
Recent progresses in relativistic beam-plasma instability theory
Directory of Open Access Journals (Sweden)
A. Bret
2010-11-01
Full Text Available Beam-plasma instabilities are a key physical process in many astrophysical phenomena. Within the fireball model of Gamma ray bursts, they first mediate a relativistic collisionless shock before they produce upstream the turbulence needed for the Fermi acceleration process. While non-relativistic systems are usually governed by flow-aligned unstable modes, relativistic ones are likely to be dominated by normally or even obliquely propagating waves. After reviewing the basis of the theory, results related to the relativistic kinetic regime of the poorly-known oblique unstable modes will be presented. Relevant systems besides the well-known electron beam-plasma interaction are presented, and it is shown how the concept of modes hierarchy yields a criterion to assess the proton to electron mass ratio in Particle in cell simulations.
Propagation and oblique collision of electron-acoustic solitons in ...
Indian Academy of Sciences (India)
1Faculty of Science, Department of Physics, Azarbaijan University of Tarbiat Moallem, 51745-406,. Tabriz, Iran. 2Islamic Azad University, Hadishahr Branch, Hadishahr, Iran. ∗. Corresponding author. E-mail: m_akbari@azaruniv.edu. MS received 3 September 2010; revised 17 January 2011; accepted 9 February 2011.
Colvin, J. D.; Matsukuma, H.; Brown, K. C.; Davis, J. F.; Kemp, G. E.; Koga, K.; Tanaka, N.; Yogo, A.; Zhang, Z.; Nishimura, H.; Fournier, K. B.
2018-03-01
This work was motivated by previous findings that the measured laser-driven heat front propagation velocity in under-dense TiO2/SiO2 foams is slower than the simulated one [Pérez et al., Phys. Plasmas 21, 023102 (2014)]. In attempting to test the hypothesis that these differences result from effects of the foam microstructure, we designed and conducted an experiment on the GEKKO laser using an x-ray streak camera to compare the heat front propagation velocity in "equivalent" gas and foam targets, that is, targets that have the same initial density, atomic weight, and average ionization state. We first discuss the design and the results of this comparison experiment. To supplement the x-ray streak camera data, we designed and conducted an experiment on the Trident laser using a new high-resolution, time-integrated, spatially resolved crystal spectrometer to image the Ti K-shell spectrum along the laser-propagation axis in an under-dense TiO2/SiO2 foam cylinder. We discuss the details of the design of this experiment, and present the measured Ti K-shell spectra compared to the spectra simulated with a detailed superconfiguration non-LTE atomic model for Ti incorporated into a 2D radiation hydrodynamic code. We show that there is indeed a microstructure effect on heat front propagation in under-dense foams, and that the measured heat front velocities in the TiO2/SiO2 foams are consistent with the analytical model of Gus'kov et al. [Phys. Plasmas 18, 103114 (2011)].
Nonlinear damping of oblique whistler mode waves through Landau resonance
Hsieh, Y.; Omura, Y.
2017-12-01
Nonlinear trapping of electrons through Landau resonance is a characteristic dynamics in oblique whistler-mode wave particle interactions. The resonance velocity of the Landau resonance at quasi-parallel propagation becomes very close to the parallel group velocity of whistler-mode wave at frequency around 0.5 Ωe, causing a long distance of resonant interaction and strong acceleration of resonant electrons [1]. We demonstrate these effective accelerations for electrons with high equatorial pitch angle ( > 60°) by test particle simulations with parameters for the Earth's inner magnetosphere at L=5. In the simulations, we focus on slightly oblique whistler mode waves with wave normal angle 10.1002/2016JA023255.
International Nuclear Information System (INIS)
Niemann, C.; Divol, L.; Froula, D.H.; Gregori, G.; Jones, O.; Kirkwood, R.K.; MacKinnon, A.J.; Meezan, N.B.; Moody, J.D.; Sorce, C.; Suter, L.J.; Glenzer, S.H.; Bahr, R.; Seka, W.
2005-01-01
We have established the intensity limits for propagation of a frequency-doubled (2ω, 527 nm) high intensity interaction beam through an underdense large-scale-length plasma. We observe good beam transmission at laser intensities at or below 2x10 14 W/cm 2 and a strong reduction at intensities up to 10 15 W/cm 2 due to the onset of parametric scattering instabilities. We show that temporal beam smoothing by spectral dispersion allows a factor of 2 higher intensities while keeping the beam spray constant, which establishes frequency-doubled light as an option for ignition and burn in inertial confinement fusion experiments
International Nuclear Information System (INIS)
Weitzner, H.
1990-06-01
This paper discusses the following topics: MHD plasma activity: equilibrium, stability and transport; statistical analysis; transport studies; edge physics studies; wave propagation analysis; basic plasma physics and fluid dynamics; space plasma; and numerical methods
Low-frequency electrostatic dust-modes in a nonuniform magnetized dusty plasma
International Nuclear Information System (INIS)
Paul, S.K.; Duha, S.S.; Mamun, A.A.
2004-07-01
A self-consistent and general description of obliquely propagating low frequency electrostatic dust-modes in a inhomogeneous, magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust-modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)
International Nuclear Information System (INIS)
Mamun, A.A.; Russel, S.M.; Mendoza-Briceno, C.A.; Alam, M.N.; Datta, T.K.; Das, A.K.
1999-05-01
A rigorous theoretical investigation has been made of multi-dimensional instability of obliquely propagating electrostatic solitary structures in a hot magnetized nonthermal dusty plasma which consists of a negatively charged hot dust fluid, Boltzmann distributed electrons, and nonthermally distributed ions. The Zakharov-Kuznetsov equation for the electrostatic solitary structures that exist in such a dusty plasma system is derived by the reductive perturbation method. The multi-dimensional instability of these solitary waves is also studied by the small-k (long wavelength plane wave) perturbation expansion method. The nature of these solitary structures, the instability criterion, and their growth rate depending on dust-temperature, external magnetic field, and obliqueness are discussed. The implications of these results to some space and astrophysical dusty plasma situations are briefly mentioned. (author)
Raman sidescatter instability in a nonuniform plasma
International Nuclear Information System (INIS)
Mostrom, M.A.
1977-01-01
In the various laser-fusion concepts, an intense electromagnetic wave (the laser) must propagate through an under-dense plasma region where it could decay, via the stimulated Raman instability, into a Langmuir plasma wave and a scattered electromagnetic wave. This process could, therefore, scatter a significant fraction of the laser energy before it could be deposited in the plasma. A density gradient, in the direction of laser incidence, localizes the instability to a narrow resonance zone where the local plasma wave frequency approximately equals the difference-frequency between the incident and scattered electromagnetic waves. The narrowness of this zone can strongly inhibit the growth of back- or oblique-scattered electromagnetic waves since they quickly propagate out of their resonance region; however, the density gradient has a much weaker effect on side-scattered waves (which propagate perpendicular to the density gradient) since they remain in their resonance zone until refraction bends them out or they exit through the side of the finite diameter laser beam. Thus, we place particular emphasis on evaluating, in a manner valid for the side scattered electromagnetic waves (which are at their turning point), the level of exponentiation at which the growth is linearly saturated due to convection of the waves out of their resonance zone. We also determine the general nature and propagation of the scattered electromagnetic waves and obtain approximate values for the resonance zone size and the time required for the above saturation
Propagation of Ion Solitary Pulses in Dense Astrophysical Electron-Positron-Ion Magnetoplasmas
Ata-Ur-Rahman; A. Khan, S.; Qamar, A.
2015-12-01
In this paper, we theoretically investigate the existence and propagation of low amplitude nonlinear ion waves in a dense plasma under the influence of a strong magnetic field. The plasma consists of ultra-relativistic and degenerate electrons and positrons and non-degenerate cold ions. Firstly, the appearance of two distinct linear modes and their evolution is studied by deriving a dispersion equation with the aid of Fourier analysis. Secondly, the dynamics of low amplitude ion solitary structures is investigated via a Korteweg-de Vries equation derived by employing a reductive perturbation method. The effects of various plasma parameters like positron concentration, strength of magnetic field, obliqueness of field, etc., are discussed in detail. At the end, analytical results are supplemented through numerical analysis by using typical representative parameters consistent with degenerate and ultra-relativistic magnetoplasmas of astrophysical regimes.
International Nuclear Information System (INIS)
Murakami, Hiroyuki; Kawata, Shigeo; Niu, Keishiro.
1983-01-01
The stability of current-carrying plasma channels, which have been proposed for transporting intense ion beams from the diodes to the target in LIB-fusion devices, is discussed. The growth rate of the most dangerous surface mode, that is, the axisymmetric sausage instabilities, are examined for plasma channels with or without radial fluid motion. The growth rate of the channel with radial fluid motion is shown to be far smaller than that of the channel with no fluid motion. It is concluded that a stable plasma channel can be formed by radial fluid motion. (author)
Energy Technology Data Exchange (ETDEWEB)
Ombrello, Timothy; Won, Sang Hee; Ju, Yiguang [Department of Mechanical and Aerospace Engineering, Engineering Quadrangle, Olden Street, Princeton, NJ 08544 (United States); Williams, Skip [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson AFB, OH 45433 (United States)
2010-10-15
The isolated effect of O{sub 2}(a{sup 1}{delta}{sub g}) on the propagation of C{sub 2}H{sub 4} lifted flames was studied at reduced pressures (3.61 kPa and 6.73 kPa). The O{sub 2}(a{sup 1}{delta}{sub g}) was produced in a microwave discharge plasma and was isolated from O and O{sub 3} by NO addition to the plasma afterglow in a flow residence time on the order of 1 s. The concentrations of O{sub 2}(a{sup 1}{delta}{sub g}) and O{sub 3} were measured quantitatively through absorption by sensitive off-axis integrated-cavity-output spectroscopy and one-pass line-of-sight absorption, respectively. Under these conditions, it was found that O{sub 2}(a{sup 1}{delta}{sub g}) enhanced the propagation speed of C{sub 2}H{sub 4} lifted flames. Comparison with the results of enhancement by O{sub 3} found in part I of this investigation provided an estimation of 2-3% of flame speed enhancement for 5500 ppm of O{sub 2}(a{sup 1}{delta}{sub g}) addition from the plasma. Numerical simulation results using the current kinetic model of O{sub 2}(a{sup 1}{delta}{sub g}) over-predicts the flame propagation enhancement found in the experiments. However, the inclusion of collisional quenching rate estimations of O{sub 2}(a{sup 1}{delta}{sub g}) by C{sub 2}H{sub 4} mitigated the over-prediction. The present isolated experimental results of the enhancement of a hydrocarbon fueled flame by O{sub 2}(a{sup 1}{delta}{sub g}), along with kinetic modeling results suggest that further studies of C{sub n}H{sub m} + O{sub 2}(a{sup 1}{delta}{sub g}) collisional and reactive quenching are required in order to correctly predict combustion enhancement by O{sub 2}(a{sup 1}{delta}{sub g}). The present experimental results will have a direct impact on the development of elementary reaction rates with O{sub 2}(a{sup 1}{delta}{sub g}) at flame conditions to establish detailed plasma-flame kinetic mechanisms. (author)
International Nuclear Information System (INIS)
Cotrino, J.; Gamero, A.; Sola, A.; Lao, C.
1989-01-01
During the first instant, previous to steady-state in a surface-wave-produced plasma, an ionization front advance front the launcher to the plasma column end. The velocity of the ionization front is much slower than the group velocity of the surface wave, this give a reflection of the incident signal on the moving ionization front. In this paper, the authors use this effect to calculate the surface wave group velocity
Document segmentation via oblique cuts
Svendsen, Jeremy; Branzan-Albu, Alexandra
2013-01-01
This paper presents a novel solution for the layout segmentation of graphical elements in Business Intelligence documents. We propose a generalization of the recursive X-Y cut algorithm, which allows for cutting along arbitrary oblique directions. An intermediate processing step consisting of line and solid region removal is also necessary due to presence of decorative elements. The output of the proposed segmentation is a hierarchical structure which allows for the identification of primitives in pie and bar charts. The algorithm was tested on a database composed of charts from business documents. Results are very promising.
Three-Dimensional Simulations of Oblique Asteroid Impacts into Water
Gisler, G. R.; Ferguson, J. M.; Heberling, T.; Plesko, C. S.; Weaver, R.
2016-12-01
Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, could be more damaging than storm surges from the strongest hurricanes. For asteroids less than 500 m in diameter that impact into deep water far from shores, the waves produced will be detectable over large distances, but probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 20 degrees to 60 degrees (where 90 degrees is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.
Energy Technology Data Exchange (ETDEWEB)
Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India); University of the Western Cape, Belville (South Africa); Devanandhan, S., E-mail: devanandhan@gmail.com [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India); Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Belville (South Africa)
2016-08-15
A theoretical investigation is carried out to study the obliquely propagating electron acoustic solitary waves having nonthermal hot electrons, cold and beam electrons, and ions in a magnetized plasma. We have employed reductive perturbation theory to derive the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation describing the nonlinear evolution of these waves. The two-dimensional plane wave solution of KdV-ZK equation is analyzed to study the effects of nonthermal and beam electrons on the characteristics of the solitons. Theoretical results predict negative potential solitary structures. We emphasize that the inclusion of finite temperature effects reduces the soliton amplitudes and the width of the solitons increases by an increase in the obliquity of the wave propagation. The numerical analysis is presented for the parameters corresponding to the observations of “burst a” event by Viking satellite on the auroral field lines.
Dust ion acoustic solitary waves in a magnetized dusty plasma with anisotropic ion pressure
International Nuclear Information System (INIS)
Choi, Cheong Rim; Ryu, Chang-Mo; Lee, D.-Y.; Lee, Nam C.; Kim, Y.-H.
2007-01-01
The influence of anisotropic ion pressure on the dust ion acoustic solitary wave (DIASW) and the double layer (DL) obliquely propagating to a magnetic field are investigated by using the Sagdeev potential. The anisotropic ion pressure is defined by applying the Chew-Goldberger-Low (CGL) theory, p-perpendicular=p-perpendicular 0 n and p-parallel=p-parallel 0 n 3 , where n is the normalized ion density. The solutions of DIASWs and DLs obliquely propagating to an external magnetic field are obtained in the small amplitude limit. It is found that the perpendicular component of anisotropic ion pressure works differently from that of the parallel component on the DIASWs in a magnetized dusty plasma, deviating from a straight extension of the isotropic pressure effect
Oblique Alfvén instabilities driven by compensated currents
Energy Technology Data Exchange (ETDEWEB)
Malovichko, P. [Main Astronomical Observatory, NASU, Kyiv (Ukraine); Voitenko, Y.; De Keyser, J., E-mail: voitenko@oma.be [Solar-Terrestrial Centre of Excellence, Space Physics Division, Belgian Institute for Space Aeronomy, Ringlaan-3-Avenue Circulaire, B-1180 Brussels (Belgium)
2014-01-10
Compensated-current systems created by energetic ion beams are widespread in space and astrophysical plasmas. The well-known examples are foreshock regions in the solar wind and around supernova remnants. We found a new oblique Alfvénic instability driven by compensated currents flowing along the background magnetic field. Because of the vastly different electron and ion gyroradii, oblique Alfvénic perturbations react differently on the currents carried by the hot ion beams and the return electron currents. Ultimately, this difference leads to a non-resonant aperiodic instability at perpendicular wavelengths close to the beam ion gyroradius. The instability growth rate increases with increasing beam current and temperature. In the solar wind upstream of Earth's bow shock, the instability growth time can drop below 10 proton cyclotron periods. Our results suggest that this instability can contribute to the turbulence and ion acceleration in space and astrophysical foreshocks.
Oblique Alfvén instabilities driven by compensated currents
International Nuclear Information System (INIS)
Malovichko, P.; Voitenko, Y.; De Keyser, J.
2014-01-01
Compensated-current systems created by energetic ion beams are widespread in space and astrophysical plasmas. The well-known examples are foreshock regions in the solar wind and around supernova remnants. We found a new oblique Alfvénic instability driven by compensated currents flowing along the background magnetic field. Because of the vastly different electron and ion gyroradii, oblique Alfvénic perturbations react differently on the currents carried by the hot ion beams and the return electron currents. Ultimately, this difference leads to a non-resonant aperiodic instability at perpendicular wavelengths close to the beam ion gyroradius. The instability growth rate increases with increasing beam current and temperature. In the solar wind upstream of Earth's bow shock, the instability growth time can drop below 10 proton cyclotron periods. Our results suggest that this instability can contribute to the turbulence and ion acceleration in space and astrophysical foreshocks.
International Nuclear Information System (INIS)
Kaur, Ravinder; Gill, Tarsem Singh; Mahajan, Ranju
2010-01-01
Laboratory as well as Particle in cell (PIC) simulation experiments reveal the strong flow of energetic electrons co-moving with laser beam in laser plasma interaction. Equation governing the evolution of complex envelope in slowly varying envelope approximation is nonlinear parabolic equation. A Lagrangian for the problem is set up and assuming a trial Gaussian profile, we solve the reduced Lagrangian problem for beam width and curvature. Besides self-focusing and self-modulation of laser beam, we observe that stability properties of such plasma system are studied about equilibrium values using this variational approach. We obtained an eigen value equation, which is cubic in nature and investigated the criterion for stability using Hurwitz conditions for laser beam plasma system.
International Nuclear Information System (INIS)
Friou, A.
2012-01-01
This thesis is divided in two parts: i) the laser channeling in hundreds of microns long under-dense plasmas (0.1 nc ≤ n ≤ nc, nc being the critical density) of a laser pulse of intensity 10 18-20 W/cm 2 and duration 1-10 ps; ii) the saturation mechanisms of stimulated Raman back-scattering of a laser pulse of intensity 10 14 to 10 16 W/cm 2 and duration of about 1 ps. A parametric study was performed to study the channeling of a very intense laser pulse, using a 2D PIC (Particle In Cell) code. Various kinds of channels were obtained depending on the laser and plasma parameters, thereby reproducing and enlarging previous studies. Moreover, the channeling velocity was measured and scaling laws were established for homogeneous plasmas. They are then applied to inhomogeneous plasmas, similar to those encountered in inertial confinement fusion (ICF). It is then possible to estimate the energy necessary to channel to the critical density, an important step for the fast ignition scheme of ICF. Raman saturation was studied using numerical simulations, in order to determine if it is due to dephasing or to the growth of sidebands, using different approaches. The first is to study Raman simulations (electromagnetic) performed with kinetic PIC and Vlasov codes. The second, is to study the evolution of a plasma initialized with a distribution function after the adiabatic theory, using a Vlasov code (electrostatic). In this case, we observe the growth of a sideband, with dominant wave number and growth rate in good agreement with kinetic simulations. The saturation of the plasma wave can be caused by both saturation mechanisms. [fr
Czech Academy of Sciences Publication Activity Database
Salvetr, P.; Kubatík, Tomáš František; Pignol, D.; Novák, P.
2017-01-01
Roč. 48, č. 2 (2017), s. 772-778 ISSN 1073-5615 Institutional support: RVO:61389021 Keywords : powder metallurgy * Spark plasma sintering Subject RIV: JJ - Other Materials OBOR OECD: Materials engineering Impact factor: 1.642, year: 2016
Schamel, Hans; Eliasson, Bengt
2016-05-01
Quantum statistics and electron trapping have a decisive influence on the propagation characteristics of coherent stationary electrostatic waves. The description of these strictly nonlinear structures, which are of electron hole type and violate linear Vlasov theory due to the particle trapping at any excitation amplitude, is obtained by a correct reduction of the three-dimensional Fermi-Dirac distribution function to one dimension and by a proper incorporation of trapping. For small but finite amplitudes, the holes become of cnoidal wave type and the electron density is shown to be described by a ϕ ( x ) 1 / 2 rather than a ϕ ( x ) expansion, where ϕ ( x ) is the electrostatic potential. The general coefficients are presented for a degenerate plasma as well as the quantum statistical analogue to these steady state coherent structures, including the shape of ϕ ( x ) and the nonlinear dispersion relation, which describes their phase velocity.
Philippov, Alexander A.; Spitkovsky, Anatoly
2018-03-01
We perform global particle-in-cell simulations of pulsar magnetospheres, including pair production, ion extraction from the surface, frame-dragging corrections, and high-energy photon emission and propagation. In the case of oblique rotators, the effects of general relativity increase the fraction of the open field lines that support active pair discharge. We find that the plasma density and particle energy flux in the pulsar wind are highly non-uniform with latitude. A significant fraction of the outgoing particle energy flux is carried by energetic ions, which are extracted from the stellar surface. Their energies may extend up to a large fraction of the open field line voltage, making them interesting candidates for ultra-high-energy cosmic rays. We show that pulsar gamma-ray radiation is dominated by synchrotron emission, produced by particles that are energized by relativistic magnetic reconnection close to the Y-point and in the equatorial current sheet. In most cases, the calculated light curves contain two strong peaks, which is in general agreement with Fermi observations. The radiative efficiency decreases with increasing pulsar inclination and increasing efficiency of pair production in the current sheet, which explains the observed scatter in L γ versus \\dot{E}. We find that the high-frequency cutoff in the spectra is regulated by the pair-loading of the current sheet. Our findings lay the foundation for quantitative interpretation of Fermi observations of gamma-ray pulsars.
Nonlinear electrostatic solitary waves in electron-positron plasmas
Lazarus, I. J.; Bharuthram, R.; Moolla, S.; Singh, S. V.; Lakhina, G. S.
2016-02-01
The generation of nonlinear electrostatic solitary waves (ESWs) is explored in a magnetized four component two-temperature electron-positron plasma. Fluid theory is used to derive a set of nonlinear equations for the ESWs, which propagate obliquely to an external magnetic field. The electric field structures are examined for various plasma parameters and are shown to yield sinusoidal, sawtooth and bipolar waveforms. It is found that an increase in the densities of the electrons and positrons strengthen the nonlinearity while the periodicity and nonlinearity of the wave increases as the cool-to-hot temperature ratio increases. Our results could be useful in understanding nonlinear propagation of waves in astrophysical environments and related laboratory experiments.
International Nuclear Information System (INIS)
Kalluri, D.K.
1996-01-01
The main effect of switching a medium (creating a temporal discontinuity in the properties of a medium) is the splitting of the source (incident) wave into new waves whose frequencies are different. Lightning induced effects in the ionosphere cause a temporary enhancement of ionization. Such transient plasmas have a time-varying plasma frequency ω p (t) with a rise time T r . If the period t 0 of a source wave existing before the transient effect begins is much larger than the rise time, the ionization change may be idealized as a sudden switching of the medium. The solution to this initial value problem with a step-change in the electron density profile is known and this profile will be considered as a reference profile. The topic of this paper is the solution of the initial value problem when t 0 is comparable to the rise time T r . The initial motivation for investigating the problem is given below. There is considerable interest in the ionospheric physics community to investigate the recently discovered Sprites phenomenon which are red emissions in the lower D region induced by the lightning discharges from a cloud to the ground. The preliminary indications are that the Sprite is a plasma with electron density enhanced by about 10 1 to 10 3 /cc in a rise time of about 100 micros
Kim, Jongsu; Kwon, Seung-Gab; Back, Seunghyun; Kang, Bongchul
2018-03-01
We present a novel laser-induced surface treatment process to rapidly control the spatial wettabilities of various functional solutions with submicron to micron resolutions. Ultrathin hydrophobic self-assembled monolayers (SAMs) that little absorb typical laser lights due to short penetration depth were selectively deactivated by instantaneous interaction with laser-induced metallic plasmas. The spatial region of the deactivated SAM, which corresponds to process resolution, is adjustable by controlling the spatial propagation of the plasma. This method leads to the parallel formation of hydrophilic functional solutions on glass substrates with a minimum resolution on the submicron scale. To show its feasibility in device engineering fields, this method was applied to the cost-effective fabrication of electronics and biosensors. Rapid self-patterning of electronic and biological functional solutions (silver nanoparticle solution and streptavidin protein solution) was successfully realized by selective deactivation of two different SAMs (tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) for electronics and the hetero-hybrid SAM (octadecyltrichlorosilane (OTS)/2-[methoxy(polyethyleneoxy)propyl] trichlorosilane (PEG)) for biosensors). As a result, this method can be exploited for the rapid and low-cost fabrication of various thin film devices such as electronics, biosensors, energy, displays, and photonics.
High-frequency emissions during the propagation of an electron beam in a high-density plasma
International Nuclear Information System (INIS)
Lalita and Tripathi, V.K.
1988-01-01
A relativistic annular electron beam passing through a high-density plasma excites Langmuir waves via Cerenkov interaction. The Langmuir waves are backscattered off ions via nonlinear ion Landau damping. At moderately high amplitudes these waves are parametrically up-converted by the beam into high-frequency electromagnetic radiation, as observed in some recent experiments. A nonlocal theory of this process is developed in a cylindrical geometry. It is seen that the growth rate of the Langmuir wave scales as one-third power of beam density. The growth rate of parametric instability scales as one-fourth power of beam density and the square root of beam thickness
International Nuclear Information System (INIS)
Cai Hongbo; Zhu Shaoping; Chen Mo; Wu Sizhong; He, X. T.; Mima, Kunioki
2011-01-01
An analytical fluid model is proposed for artificially collimating fast electron beams produced in the interaction of ultraintense laser pulses with specially engineered low-density-core-high-density-cladding structure targets. Since this theory clearly predicts the characteristics of the spontaneously generated magnetic field and its dependence on the plasma parameters of the targets transporting fast electrons, it is of substantial relevance to the target design for fast ignition. The theory also reveals that the rapid changing of the flow velocity of the background electrons in a transverse direction (perpendicular to the flow velocity) caused by the density jump dominates the generation of a spontaneous interface magnetic field for these kinds of targets. It is found that the spontaneously generated magnetic field reaches as high as 100 MG, which is large enough to collimate fast electron transport in overdense plasmas. This theory is also supported by numerical simulations performed using a two-dimensional particle-in-cell code. It is found that the simulation results agree well with the theoretical analysis.
Oblique photon expansion of QED structure functions
International Nuclear Information System (INIS)
Chahine, C.
1986-01-01
In the oblique photon expansion, the collinear part of photon emission is summed up to all orders in perturbation theory. The number of oblique or non-collinear photons is the expansion order. Unlike in perturbation theory, every term of the expansion is both infrared finite and gauge invariant. The zero oblique photon contribution to the electromagnetic structure tensor in QED is computed in detail. The behaviors of the structure functions F1 and F2 are discussed in the soft and ultra-soft limits
International Nuclear Information System (INIS)
Zigman, V.J.; Milic, B.S.
1995-01-01
The dependence of the attenuation of the longitudinal electron Langmuir waves (ω ∼ ω pe ), in collisional weakly ionized, non-magnetized, uniform and steady-state plasmas placed in external d.c. electric field, on the angle θ between the wave vector and the electron drift rvec u is studied on the ground of the kinetic theory and the linear perturbation technique. The collisionless and collisional contributions to the overall attenuation were evaluated separately, as it was shown previously that in certain instances the elastic e - n encounters (with collision frequency ν en , ν en much-lt ω pe ) may attenuate the Langmuir waves more efficiently than the Landau mechanism. More precisely, it was found that, for any fixed value of E 0 /n n , there exists a critical value of the ratio n n /X above which the collisional attenuation prevails
Magnetoresistive waves in plasmas
International Nuclear Information System (INIS)
Felber, F.S.; Hunter, R.O. Jr.; Pereira, N.R.; Tajima, T.
1982-01-01
The self-generated magnetic field of a current diffusing into a plasma between conductors can magnetically insulate the plasma. Propagation of magnetoresistive waves in plasmas is analyzed. Applications to plasma opening switches are discussed
A Model for Periodic Nonlinear Electric Field Structures in Space Plasmas
International Nuclear Information System (INIS)
Qureshi, M.N.S.; Shi Jiankui; Liu Zhenxing
2009-01-01
In this study, we present a physical model to explain the generation mechanism of nonlinear periodic waves with a large amplitude electric field structures propagating obliquely and exactly parallel to the magnetic field. The 'Sagdeev potential' from the MHD equations is derived and the nonlinear electric field waveforms are obtained when the Mach number, direction of propagation, and the initial electric field satisfy certain plasma conditions. For the parallel propagation, the amplitude of the electric field waves with ion-acoustic mode increases with the increase of initial electric field and Mach number but its frequency decreases with the increase of Mach number. The amplitude and frequency of the electric field waves with ion-cyclotron mode decrease with the increase of Mach number and become less spiky, and its amplitude increases with the increase of initial electric field. For the oblique propagation, only periodic electric field wave with an ion-cyclotron mode obtained, its amplitude and frequency increase with the increase of Mach number and become spiky. From our model the electric field structures show periodic, spiky, and saw-tooth behaviours corresponding to different plasma conditions.
Estrada, T.; Ascasíbar, E.; Blanco, E.; Cappa, A.; Castejón, F.; Hidalgo, C.; van Milligen, B. Ph.; Sánchez, E.
2015-06-01
The spatiotemporal evolution of the interaction between turbulence and flows has been studied close to the L-H transition threshold conditions in the edge of TJ-II plasmas. As in other devices the temporal dynamics of the interaction displays limit cycle oscillations (LCO) with a characteristic predator-prey relationship between flows and turbulence. At TJ-II, the turbulence-flow front is found to propagate radially outwards at the onset of the LCO and in some particular cases, after a short time interval without oscillations, a reversal in the front propagation velocity is observed. Associated to this velocity reversal, a change in the temporal ordering of the LCO is measured. However, the change in the temporal ordering is not related to an intrinsic change in the nature of the LCO. In all cases the turbulence increase leads the process and produces an increase in the E × B flow shear. Dedicated experiments have been carried out to investigate the physical mechanisms triggering the onset of the LCO. At TJ-II the LCO are preferentially observed close to the transition threshold conditions at specific magnetic configurations having a low order rational surface located at the inner side of the E × B flow shear location. The behaviour of different frequency modes has been analysed and interpreted in terms of a geodesic acoustic mode generated by the non-linear mode coupling of Alfvén eigenmodes that evolves towards a low frequency flow, plus a MHD mode linked to the low order rational surface, as precursors of the LCO.
Ionospheric Oblique Incidence Soundings by Satellites
National Oceanic and Atmospheric Administration, Department of Commerce — The oblique incidence sweep-frequency ionospheric sounding technique uses the same principle of operation as the vertical incidence sounder. The primary difference...
Propagation and scattering of high-intensity X-ray pulses in dense atomic gases and plasmas
International Nuclear Information System (INIS)
Weninger, Clemens
2015-10-01
scattering signal can thus be amplified by several orders of magnitude. To study stimulated X-ray emission a generalized one-dimensional Maxwell-Bloch model is developed. The radiation is propagated through the medium with the help of the Maxwell equations and the radiation is coupled to the atomic system via the polarization. The atomic system is treated in the density matrix formalism and the time evolution of the coherences determine the polarization of the medium.
Energy Technology Data Exchange (ETDEWEB)
Rafat, A., E-mail: rafat.plasma@gmail.com; Rahman, M. M.; Alam, M. S.; Mamun, A. A. [Jahangirnagar University, Department of Physics (Bangladesh)
2016-08-15
Obliquely propagating electron-acoustic solitary waves (EASWs) in a magnetized electron−positron−ion plasma (containing nonextensive hot electrons and positrons, inertial cold electrons, and immobile positive ions) are precisely investigated by deriving the Zakharov–Kuznetsov equation. It is found that the basic features (viz. polarity, amplitude, width, phase speed, etc.) of the EASWs are significantly modified by the effects of the external magnetic field, obliqueness of the system, nonextensivity of hot positrons and electrons, ratio of the hot electron temperature to the hot positron temperature, and ratio of the cold electron number density to the hot positron number density. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of EASWs in various astrophysical plasmas.
Thermal transport in oblique finned microminichannels
Fan, Yan; Singh, Pawan Kumar; Lee, Yong Jiun
2015-01-01
The main aim of this book is to introduce and give an overview of a novel, easy, and highly effective heat transfer augmentation technique for single-phase micro/minichannel heat sink. The specific objectives of the volume are to: Introduce a novel planar oblique fin microchannel and cylindrical oblique fin minichannel heat sink design using passive heat transfer enhancement techniques Investigate the thermal transport in both planar and cylindrical oblique fin structures through numerical simulation and systematic experimental studies. Evaluate the feasibility of employing the proposed solution in cooling non-uniform heat fluxes and hotspot suppression Conduct the similarity analysis and parametric study to obtain empirical correlations to evaluate the total heat transfer rate of the oblique fin heat sink Investigate the flow mechanism and optimize the dimensions of cylindrical oblique fin heat sink Investigate the influence of edge effect on flow and temperature uniformity in these oblique fin chan...
Sadeghi, Shahriar; Yassaghi, Ali
2016-04-01
Stratigraphy, detailed structural mapping and a crustal-scale cross section across the NW Zagros collision zone provide constraints on the spatial evolution of oblique convergence of the Arabian and Eurasian plates since the Late Cretaceous. The Zagros collision zone in NW Iran consists of the internal Sanandaj-Sirjan, Gaveh Rud and Ophiolite zones and the external Bisotoun, Radiolarite and High Zagros zones. The Main Zagros Thrust is the major structure of the Zagros suture zone. Two stages of oblique deformation are recognized in the external part of the NW Zagros in Iran. In the early stage, coexisting dextral strike-slip and reverse dominated domains in the Radiolarite zone developed in response to deformation partitioning due to oblique convergence. Dextral-reverse faults in the Bisotoun zone are also compatible with oblique convergence. In the late stage, deformation partitioning occurred during southeastward propagation of the Zagros orogeny towards its foreland resulting in synchronous development of orogen-parallel strike-slip and thrust faults. It is proposed that the first stage was related to Late Cretaceous oblique obduction, while the second stage resulted from Cenozoic collision. The Cenozoic orogen-parallel strike-slip component of Zagros oblique convergence is not confined to the Zagros suture zone (Main Recent Fault) but also occurred in the external part (Marekhil-Ravansar fault system). Thus, it is proposed that oblique convergence of Arabian and Eurasian plates in Zagros collision zone initiated with oblique obduction in the Late Cretaceous followed by oblique collision in the late Tertiary, consistent with global plate reconstructions.
Vertical and oblique HF sounding with a network of synchronised ionosondes
Czech Academy of Sciences Publication Activity Database
Verhulst, T.; Altadill, D.; Mielich, J.; Reinisch, B.; Galkin, I.; Mouzakis, A.; Belehaki, A.; Burešová, Dalia; Stankov, S.; Blanch, E.; Kouba, Daniel
2017-01-01
Roč. 60, č. 8 (2017), s. 1644-1656 ISSN 0273-1177 R&D Project s: GA ČR(CZ) GC15-07281J Institutional support: RVO:68378289 Keywords : travelling ionospheric disturbances * digisonde * oblique sounding * ionospheric electromagnetic wave propagation * ionospheric measurement Subject RIV: DG - Athmosphere Science s, Meteorology OBOR OECD: Meteorology and atmospheric science s Impact factor: 1.401, year: 2016 http://www. science direct.com/ science /article/pii/S0273117717304593
ALBERTO CARLOS DE QUEIROZ PINTO; VICTOR GALÁN SAÚCO; SISIR KUMAR MITRA; FRANCISCO RICARDO FERREIRA
2018-01-01
ABSTRACT This Chapter has the objectives to search, through the review of the available literature, important informations on the evolution of mango propagation regarding theoretical and practical aspects from cellular base of sexual propagation, nursery structures and organizations, substrate compositions and uses, importance of rootstock and scion selections, also it will be described the preparation and transport of the grafts (stem and bud) as well as the main asexual propagation methods...
Mombaerts, I.; Koornneef, L.; Everhard-Halm, Y. S.; Hughes, D. S.; Maillette de Buy Wenniger-Prick, L. J.
1995-01-01
We used superior oblique luxation and trochlear luxation as new surgical procedures to treat acquired Brown's syndrome and superior oblique muscle overaction. We studied nine patients (11 eyes) who underwent trochlear surgery between 1988 and 1993. Four patients had acquired Brown's syndrome and
International Nuclear Information System (INIS)
Singh, Dhananjay K.; Malik, Hitendra K.
2007-01-01
Soliton propagation at critical density of negative ions is studied for weakly inhomogeneous magnetized cold plasma having positive ions, negative ions, and electrons. A general phase velocity relation is obtained and possible modes are studied for different cases involving different constituents of the plasma. Two types of modes (fast and slow) are found to propagate for the equal mass of the positive and negative ions. However, a limit on the obliqueness of magnetic field is obtained for the propagation of slow mode. For both types of modes, a variable coefficient modified Korteweg-deVries equation with an additional term arisen due to the density gradient is realized, which admits solutions for compressive solitons and rarefactive solitons of the same amplitudes at critical negative ion density. The propagation characteristics of these solitons are studied under the effect of densities of ions, magnetic field, and its obliqueness. The amplitudes of fast and slow wave solitons show their opposite behavior with the negative ion concentration, which is consistent with the variation of phase velocities with the negative ion density
Energy Technology Data Exchange (ETDEWEB)
Etievant, C [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires
1963-12-15
The instabilities developing in a 'beam-plasma' system and in a 'double-beam' system in the presence of a magnetic field are discussed theoretically starting from the conductivity tensor expression for a multi-beam system. Oblique propagation is taken into account and this leads to the introduction of certain instability mechanisms which would not appear in the case of a propagation which is purely parallel or perpendicular to the magnetic field. Two experiments are described: a) Study of the collision of two counterstreaming electron beams: An instability has been observed experimentally which leads to the generation of a stationary cyclotron wave having a frequency of {omega}{sub ce}/2. A description is given of the measurement of the interaction frequency, of the wavelength and of the build-up time of the wave. b) Study of a 'beam-plasma' system: A description is given of the measurement of the spectra of excited waves and of the perturbation of the beam velocity distribution at the plasma-exit. This perturbation is very pronounced when 'plasma-plasma' interaction appears in the system. A study into cyclotron oscillations produced in the plasma by excitation due to the passage of the beam is also described in this report. (author) [French] Les instabilites se developpant dans un systeme 'faisceau-plasma' et dans un systeme 'faisceau-faisceau' en la presence d'un champ magnetique sont discutees theoriquement a partir de l'expression du tenseur de conductivite d'un systeme multi-faisceaux. La propagation oblique est prise en consideration, ce qui introduit certains mecanismes d'instabilite qui n'apparaitraient pas pour une propagation purement parallele ou perpendiculaire au champ magnetique. Deux experiences sont decrites: a) Etude de la collision de deux faisceaux d'electrons: Une instabilite conduisant a la generation d'une onde cyclotronique stationnaire a la frequence {omega}{sub ce}/2 a ete observee experimentalement. Les mesures de la frequence d
Ito, Kenichi; Nonaka, Koji; Ogaya, Shinya; Ogi, Atsushi; Matsunaka, Chiaki; Horie, Jun
2016-06-01
We aimed to characterize rectus abdominis, internal oblique, and external oblique muscle activity in healthy adults under expiratory resistance using surface electromyography. We randomly assigned 42 healthy adult subjects to 3 groups: 30%, 20%, and 10% maximal expiratory intraoral pressure (PEmax). After measuring 100% PEmax and muscle activity during 100% PEmax, the activity and maximum voluntary contraction of each muscle during the assigned experimental condition were measured. At 100% PEmax, the external oblique (pinternal oblique (pexternal oblique (pinternal oblique (pexternal oblique: pinternal oblique: p<0.01). The abdominal oblique muscles are the most active during forced expiration. Moreover, 30% PEmax is the minimum intensity required to achieve significant, albeit very slight, muscle activity during expiratory resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.
Optically sectioned imaging by oblique plane microscopy
Kumar, Sunil; Lin, Ziduo; Lyon, Alex R.; MacLeod, Ken T.; Dunsby, Chris
2011-03-01
Oblique Plane Microscopy (OPM) is a light sheet microscopy technique that combines oblique illumination with correction optics that tilt the focal plane of the collection system. OPM can be used to image conventionally mounted specimens on coverslips or tissue culture dishes and has low out-of-plane photobleaching and phototoxicity. No moving parts are required to achieve an optically sectioned image and so high speed optically sectioned imaging is possible. The first OPM results obtained using a high NA water immersion lens on a commercially available inverted microscope frame are presented, together with a measurement of the achievable optical resolution.
Directory of Open Access Journals (Sweden)
ALBERTO CARLOS DE QUEIROZ PINTO
2018-03-01
Full Text Available ABSTRACT This Chapter has the objectives to search, through the review of the available literature, important informations on the evolution of mango propagation regarding theoretical and practical aspects from cellular base of sexual propagation, nursery structures and organizations, substrate compositions and uses, importance of rootstock and scion selections, also it will be described the preparation and transport of the grafts (stem and bud as well as the main asexual propagation methods their uses and practices. Finally, pattern and quality of graft mangos and their commercialization aspects will be discussed in this Chapter.
International Nuclear Information System (INIS)
Tuite, M.J.; Asinger, D.; Orwin, J.F.
2001-01-01
Objective. To compare the accuracy for diagnosing rotator cuff tears of oblique coronal images supplemented with standard oblique sagittal images versus thinner-section angled oblique sagittal images.Design and patients. The study included 75 consecutive patients who had a shoulder MR scan followed by arthroscopy. MR images included oblique coronal, oblique sagittal (4 mm thick, 1 mm interslice gap), and angled oblique sagittal (3 mm/0.2 mm) images perpendicular to the lateral cuff. A musculoskeletal staff radiologist and fellow separately evaluated the cuff for tears on the oblique coronal images supplemented with either the oblique sagittal or the angled sagittal images.Results. For distinguishing a cuff tear from no tear, the staff radiologist had an accuracy of 0.76 (95% confidence interval: 0.67, 0.85) with the standard sagittal set, and 0.88 (0.80, 0.95) with the angled set (P=0.04). There was a nonsignificant improvement in accuracy for the fellow, calculated as 0.73 (0.63, 0.83) on the standard sagittal set and 0.76 (0.67, 0.85) on the angled set. Both readers also improved their diagnostic accuracy for partial-thickness tears with the angled set, although the improvement was statistically significant only for the staff radiologist.Conclusion. There is a slight improvement in accuracy for diagnosing rotator cuff tears, particularly partial-thickness tears, for the more experienced radiologist using thinner-section angled oblique sagittal images. These images may be useful as a supplemental sequence in patients where it is important to identify partial-thickness tears accurately. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Tuite, M J; Asinger, D; Orwin, J F [Dept. of Radiology, Univ. of Wisconsin Hospital and Clinics, Madison, WI (United States)
2001-05-01
Objective. To compare the accuracy for diagnosing rotator cuff tears of oblique coronal images supplemented with standard oblique sagittal images versus thinner-section angled oblique sagittal images.Design and patients. The study included 75 consecutive patients who had a shoulder MR scan followed by arthroscopy. MR images included oblique coronal, oblique sagittal (4 mm thick, 1 mm interslice gap), and angled oblique sagittal (3 mm/0.2 mm) images perpendicular to the lateral cuff. A musculoskeletal staff radiologist and fellow separately evaluated the cuff for tears on the oblique coronal images supplemented with either the oblique sagittal or the angled sagittal images.Results. For distinguishing a cuff tear from no tear, the staff radiologist had an accuracy of 0.76 (95% confidence interval: 0.67, 0.85) with the standard sagittal set, and 0.88 (0.80, 0.95) with the angled set (P=0.04). There was a nonsignificant improvement in accuracy for the fellow, calculated as 0.73 (0.63, 0.83) on the standard sagittal set and 0.76 (0.67, 0.85) on the angled set. Both readers also improved their diagnostic accuracy for partial-thickness tears with the angled set, although the improvement was statistically significant only for the staff radiologist.Conclusion. There is a slight improvement in accuracy for diagnosing rotator cuff tears, particularly partial-thickness tears, for the more experienced radiologist using thinner-section angled oblique sagittal images. These images may be useful as a supplemental sequence in patients where it is important to identify partial-thickness tears accurately. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Imbeaux, F
1999-09-22
Control of the current density profile is a critical issue in view to obtain high fusion performances in tokamak plasmas? It is therefore important to be able to control the power deposition profile of the lower hybrid wave, which has the highest current drive efficiency among all other non-inductive additional methods. Propagation and absorption of this wave are investigated in the Tore Supra tokamak using a new hard x-ray tomographic system and a new ray-tracing/Fokker-Planck code. These tools are described in detail and allow to analyse the lower hybrid power deposition profile dependence as a function of various plasma parameters (density, magnetic field, current) and of the injected wave spectrum. A good agreement between the code and the measurements found when the central electron temperature is greater than about 3 keV, that is in regimes where the wave undergoes only a few reflections before being absorbed. The simulations are then used to interpret the experimental trends. The lower hybrid power deposition profile is in nearly all discharges localised at a normalised minor radius of 0.2-0.3, and is weakly sensitive to variations of plasma parameters. It is hence difficult to perform an efficient control of the current profile generated by the lower hybrid wave in Tore Supra. This goal may nevertheless be reached by using an original method, which uses an auxiliary lower hybrid wave injected by a vertical port of the torus. This method is investigated by means of the simulation code. (author)
Linear coupling of electromagnetic and Jeans modes in self-gravitating plasma streams
International Nuclear Information System (INIS)
Yaroshenko, Victoria V.; Voitenko, Yuriy; Goossens, Marcel
2002-01-01
A new mechanism of linear coupling between electromagnetic (nonpotential) and gravitational disturbances is found for oblique propagation relatively to particle streams. The general dispersion law is derived and applied to the case of two countersteaming dust beams of equal strength and quiasiperpendicular propagation. It reveals a strong linear coupling between the low-frequency aperiodically unstable electromagnetic (AEM) and the Jeans (JM) modes. The coupling is of a mode conversion type, resulting in a frequency gap in the dispersion, and thus significantly modifies the instability criteria. It is shown that, in contrast to the electrostatic case, AEM and JM coupling in streaming self-gravitating plasmas can actually appear even if the plasma frequencies of the dust species greatly exceed the corresponding Jeans frequencies
Obliquity Modulation of the Incoming Solar Radiation
Liu, Han-Shou; Smith, David E. (Technical Monitor)
2001-01-01
Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.
Moore, M. R.; Howison, S. D.; Ockendon, J. R.; Oliver, J. M.
2012-01-01
A minor error in Howison et al. (J. Eng. Math. 48:321-337, 2004) obscured the fact that the points at which the free surface turns over in the solution of the Wagner model for the oblique impact of a two-dimensional body are directly related
Oblique-Flying-Wing Supersonic Transport Airplane
Van Der Velden, Alexander J. M.
1992-01-01
Oblique-flying-wing supersonic airplane proposed as possible alternative to B747B (or equivalent). Tranports passengers and cargo as fast as twice speed of sound at same cost as current subsonic transports. Flies at same holding speeds as present supersonic transports but requires only half takeoff distance.
A case of dorsal oblique fingertip amputation.
Takeda, Shinsuke; Tatebe, Masahiro; Morita, Akimasa; Yoneda, Hidemasa; Iwatsuki, Katsuyuki; Hirata, Hitoshi
2017-01-01
This study reports successful finger replantation in a patient with a dorsal oblique fingertip amputation. When repairing this unique type of injury, an evaluation of the remaining vessels is more useful for successful replantation than the anatomical zone classification. We propose that Kasai's classification is appropriate for guiding treatment.
A case of dorsal oblique fingertip amputation
Takeda, Shinsuke; Tatebe, Masahiro; Morita, Akimasa; Yoneda, Hidemasa; Iwatsuki, Katsuyuki; Hirata, Hitoshi
2017-01-01
Abstract This study reports successful finger replantation in a patient with a dorsal oblique fingertip amputation. When repairing this unique type of injury, an evaluation of the remaining vessels is more useful for successful replantation than the anatomical zone classification. We propose that Kasai?s classification is appropriate for guiding treatment.
Orientation Strategies for Aerial Oblique Images
Wiedemann, A.; Moré, J.
2012-07-01
Oblique aerial images become more and more distributed to fill the gap between vertical aerial images and mobile mapping systems. Different systems are on the market. For some applications, like texture mapping, precise orientation data are required. One point is the stable interior orientation, which can be achieved by stable camera systems, the other a precise exterior orientation. A sufficient exterior orientation can be achieved by a large effort in direct sensor orientation, whereas minor errors in the angles have a larger effect than in vertical imagery. The more appropriate approach is by determine the precise orientation parameters by photogrammetric methods using an adapted aerial triangulation. Due to the different points of view towards the object the traditional aerotriangulation matching tools fail, as they produce a bunch of blunders and require a lot of manual work to achieve a sufficient solution. In this paper some approaches are discussed and results are presented for the most promising approaches. We describe a single step approach with an aerotriangulation using all available images; a two step approach with an aerotriangulation only of the vertical images plus a mathematical transformation of the oblique images using the oblique cameras excentricity; and finally the extended functional model for a bundle block adjustment considering the mechanical connection between vertical and oblique images. Beside accuracy also other aspects like efficiency and required manual work have to be considered.
Oblique patterned etching of vertical silicon sidewalls
Bruce Burckel, D.; Finnegan, Patrick S.; David Henry, M.; Resnick, Paul J.; Jarecki, Robert L.
2016-04-01
A method for patterning on vertical silicon surfaces in high aspect ratio silicon topography is presented. A Faraday cage is used to direct energetic reactive ions obliquely through a patterned suspended membrane positioned over the topography. The technique is capable of forming high-fidelity pattern (100 nm) features, adding an additional fabrication capability to standard top-down fabrication approaches.
Simple Way of Generating Oblique Impact
Czech Academy of Sciences Publication Activity Database
Trnka, Jan; Dvořáková, Pavla; Veselý, Eduard
2007-01-01
Roč. 31, č. 2 (2007), s. 28-32 ISSN 0732-8818 Institutional research plan: CEZ:AV0Z20760514 Keywords : oblique impact * exploding wire * holography Subject RIV: JR - Other Machinery Impact factor: 0.400, year: 2007
International Nuclear Information System (INIS)
Gomez R, F.; Ondarza R, R.
2004-01-01
An analytic model is presented for the description of the motion of a charged particle in the interaction of an elliptically electromagnetic pulse polarized propagating along a static and homogeneous external magnetic field in a plasma starting from the force equation. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary and modulated width by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radioactive effects. (Author)
International Nuclear Information System (INIS)
Gomez R, F.; Ondarza R, R.
2004-01-01
An analytical model for the description of the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized propagating along of a static and homogeneous external magnetic field in a plasma starting from the force equation is presented. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary amplitude and modulated by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radiative effects. (Author)
Injury risk functions for frontal oblique collisions.
Andricevic, Nino; Junge, Mirko; Krampe, Jonas
2018-03-09
The objective of this article was the construction of injury risk functions (IRFs) for front row occupants in oblique frontal crashes and a comparison to IRF of nonoblique frontal crashes from the same data set. Crashes of modern vehicles from GIDAS (German In-Depth Accident Study) were used as the basis for the construction of a logistic injury risk model. Static deformation, measured via displaced voxels on the postcrash vehicles, was used to calculate the energy dissipated in the crash. This measure of accident severity was termed objective equivalent speed (oEES) because it does not depend on the accident reconstruction and thus eliminates reconstruction biases like impact direction and vehicle model year. Imputation from property damage cases was used to describe underrepresented low-severity crashes-a known shortcoming of GIDAS. Binary logistic regression was used to relate the stimuli (oEES) to the binary outcome variable (injured or not injured). IRFs for the oblique frontal impact and nonoblique frontal impact were computed for the Maximum Abbreviated Injury Scale (MAIS) 2+ and 3+ levels for adults (18-64 years). For a given stimulus, the probability of injury for a belted driver was higher in oblique crashes than in nonoblique frontal crashes. For the 25% injury risk at MAIS 2+ level, the corresponding stimulus for oblique crashes was 40 km/h but it was 64 km/h for nonoblique frontal crashes. The risk of obtaining MAIS 2+ injuries is significantly higher in oblique crashes than in nonoblique crashes. In the real world, most MAIS 2+ injuries occur in an oEES range from 30 to 60 km/h.
Inferior Oblique Overaction: Anterior Transposition Versus Myectomy.
Rajavi, Zhale; Feizi, Mohadeseh; Behradfar, Narges; Yaseri, Mehdi; Sayanjali, Shima; Motevaseli, Tahmine; Sabbaghi, Hamideh; Faghihi, Mohammad
2017-07-01
To compare the efficacy of inferior oblique myectomy and anterior transposition for correcting inferior oblique overaction (IOOA). This retrospective study was conducted on 56 patients with IOOA who had either myectomy or anterior transposition of the inferior oblique muscle from 2010 to 2015. The authors compared preoperative and postoperative inferior oblique muscle function grading (-4 to +4) as the main outcome measure and vertical and horizontal deviation, dissociated vertical deviation (DVD), and A- and V-pattern between the two surgical groups as secondary outcomes. A total of 99 eyes of 56 patients with a mean age of 5.9 ± 6.5 years were included (47 eyes in the myectomy group and 52 eyes in the anterior transposition group). There were no differences in preoperative best corrected visual acuity, amblyopia, spherical equivalent, and primary versus secondary IOOA between the two groups. Both surgical procedures were effective in reducing IOOA and satisfactory results were similar between the two groups: 61.7% and 67.3% in the myectomy and anterior transposition groups, respectively (P = .56). After adjustment for the preoperative DVD, there was no statistically significant difference between the two groups postoperatively. The preoperative hypertropia was 6 to 14 and 6 to 18 prism diopters (PD) in the myectomy and anterior transposition groups, respectively. After surgery, no patient had a vertical deviation greater than 5 PD. Both the inferior oblique myectomy and anterior transposition procedures are effective in reducing IOOA with similar satisfactory results. DVD and hypertropia were also corrected similarly by these two surgical procedures. [J Pediatr Ophthalmol Strabismus. 2017;54(4):232-237.]. Copyright 2017, SLACK Incorporated.
The optics of gyrotropic crystals in the field of two counter-propagating ultrasound waves
International Nuclear Information System (INIS)
Gevorgyan, A H; Harutyunyan, E M; Hovhannisyan, M A; Matinyan, G K
2014-01-01
We consider oblique light propagation through a layer of a gyrotropic crystal in the field of two counter-propagating ultrasound waves. The problem is solved by Ambartsumyan's layer addition modified method. The results of the reflection spectra for different values of the problem parameters are presented. The possibilities of such system applications are discussed.
Geshi, Nobuo
2009-04-01
Oblique development of the ring faults reflecting the structural heterogeneities inside the volcano formed many asymmetric structures of Miyakejima 2000 AD caldera. The asymmetry includes (a) offset location of the ring faults with respect to the associated shallow magma chamber, (b) unequal outward migration of the caldera wall 600 m at the southeastern rim but only 200 m at the northwestern rim, (c) development of tilted terrace only at the southeastern caldera margin, (d) eruption sites and fumaroles being confined to the southern part of the caldera. Geophysical data, including ground deformation and seismic activity, indicates the offset of the location of the magma chamber about 2 km south of the caldera center on the surface. The ring faults propagated from the deflating magma chamber obliquely about 30 degrees toward the summit. The oblique subsidence of the cylindrical block formed a wider instable zone, particularly in the southeastern side of the ring fault that enhanced the larger outward migration of the caldera rim and also caused the formation of the outer half-ring fault bordering the tilting slope at the southern part. Ascending pass of the buoyant magma along the tilted ring faults was concentrated in the southern half of the caldera and consequently the distributions of the eruption sites and fumaroles are localized in the southern-half part of the caldera. The structure of the Miyakejima 2000 caldera with complete development of the ring faults, its high roof aspect ratio and oblique subsidence is clearly distinguishable from trapdoor-type caldera. The oblique development of the ring faults can be controlled by the mechanical contrast between the solidified conduits and surrounding fragile volcanic edifice. Asymmetric development of the Miyakejima caldera shows that the collapsed calderas are potential indicators of the heterogeneous structures inside of the volcano, particularly in the case of small-size caldera.
Inferior oblique weakening surgery on ocular torsion in congenital superior oblique palsy
Directory of Open Access Journals (Sweden)
Jinho Lee
2015-06-01
Full Text Available AIM:To investigate changes in fundus excyclotorsion after inferior oblique myectomy or myotomy.METHODS:The records of 21 patients undergoing strabismus surgery by a single surgeon between 2009 and 2012 were examined. Only patients who had undergone an inferior oblique myectomy or myotomy, with or without horizontal rectus muscle surgery, were evaluated. Digital fundus photographs were obtained, and the angle formed by a horizontal line passing through the optic disc center and a reference line connecting the foveola and optic disc center was measured. Associated clinical factors examined include age at the time of surgery, presence or absence of a head tilt, degree of preoperative vertical deviation, torsional angle, inferior oblique muscle overaction/superior oblique muscle underaction, and surgery laterality. Whether the procedure was performed alone or in combination with a horizontal rectus muscle surgery was also examined.RESULTS:Mean preoperative torsional angle was 12.0±6.4°, which decreased to 6.9±5.7° after surgery (P<0.001, paired t-test. Torsional angle also decreased from 15.1±7.0° to 6.2±4.3° in the myectomy group (P<0.001, paired t-test but there were no significant changes in the myotomy group (P=0.093, Wilcoxon signed rank test. Multivariable linear regression analysis showed that preoperative torsional angle, degree of inferior oblique overaction, and age at surgery independently and significantly affected postoperative torsional angle.CONCLUSION:Mean torsional angle decreased after inferior oblique myectomy. Degree of preoperative torsional angle, inferior oblique overaction, and age at surgery influence postoperative torsional angle.
Mostafa, Attiat M; Kassem, Rehab R
2018-05-01
To compare the effect of, and the rate of subsequent development of iatrogenic antielevation syndrome after, unilateral versus bilateral inferior oblique graded recession-anteriorization to treat unilateral inferior oblique overaction. Thirty-four patients with unilateral inferior oblique overaction were included in a randomized prospective study. Patients were equally divided into 2 groups. Group UNI underwent unilateral, group BI bilateral, inferior oblique graded recession-anteriorization. A successful outcome was defined as orthotropia, or within 2 ∆ of a residual hypertropia, in the absence of signs of antielevation syndrome, residual inferior oblique overaction, V-pattern, dissociated vertical deviation, or ocular torticollis. A successful outcome was achieved in 11 (64.7%) and 13 (76.5%) patients in groups UNI and BI, respectively (p = 0.452). Antielevation syndrome was diagnosed as the cause of surgical failure in 6 (35.3%) and 2 (11.8%) patients, in groups UNI and BI, respectively (p = 0.106). The cause of surgical failure in the other 2 patients in group BI was due to persistence of ocular torticollis and hypertropia in a patient with superior oblique palsy and a residual V-pattern and hypertropia in the other patient. The differences between unilateral and bilateral inferior oblique graded recession-anteriorization are insignificant. Unilateral surgery has a higher tendency for the subsequent development of antielevation syndrome. Bilateral surgery may still become complicated by antielevation syndrome, although at a lower rate. In addition, bilateral surgery had a higher rate of undercorrection. Further studies on a larger sample are encouraged.
Characterization of Oblique Dual Frame Pairs
DEFF Research Database (Denmark)
Christensen, Ole; Eldar, Yonina
2006-01-01
Given a frame for a subspace W of a Hilbert space H, we consider all possible families of oblique dual frame vectors on an appropriately chosen subspace V. In place of the standard description, which involves computing the pseudoinverse of the frame operator, we develop an alternative characteriz...... for the case of shift-invariant spaces with a single generator. The theory is also adapted to the standard frame setting in which the original and dual frames are defined on the same space. Copyright (C) 2006 Hindawi Publishing Corporation. All rights reserved.......Given a frame for a subspace W of a Hilbert space H, we consider all possible families of oblique dual frame vectors on an appropriately chosen subspace V. In place of the standard description, which involves computing the pseudoinverse of the frame operator, we develop an alternative...
Magnetization reversal mechanisms under oblique magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Ntallis, N.; Efthimiadis, K.G., E-mail: kge@auth.gr
2017-03-01
In this work finite element micromagnetic simulations were performed in order to study the reversal mechanisms of spherical ferromagnetic particles with uniaxial magnetocrystalline anisotropy, when they are magnetized along an oblique direction with respect to the anisotropy axis. Magnetization loops are taken in different directions of external magnetic field, at different anisotropy constants and particle sizes. In the simulation results, the three reversal mechanisms (coherent, curling and domains) are observed and new phenomena arise due to the action of oblique magnetic fields. Moreover, the dependence of the critical fields with respect to the angle of the external field is presented. - Highlights: • Finite element micromagnetic simulation of the three different reversal mechanisms. • For the curling mechanism, the new phenomenon is the rotation of the vortex. • In the domain reversal mechanism, the formed domain wall is smaller than 180°. • In soft ferromagnetic particles a rearrangement of the magnetic domains is observed.
Flow control for oblique shock wave reflections
Giepman, R.H.M.
2016-01-01
Shock wave-boundary layer interactions are prevalent in many aerospace applications that involve transonic or supersonic flows. Such interactions may lead to boundary layer separation, flow unsteadiness and substantial losses in the total pressure. Flow control techniques can help to mitigate these adverse effects and stabilize the interaction. This thesis focuses on passive flow control techniques for oblique shock wave reflections on flat plates and presents experimental results for both la...
Nonlinear modulation of ion acoustic waves in a magnetized plasma
International Nuclear Information System (INIS)
Bharuthram, R.; Shukla, P.K.
1987-01-01
The quasistatic plasma slow response to coherent ion acoustic waves in a magnetized plasma is considered. A multidimensional cubic nonlinear Schroedinger equation is derived. It is found that the ion acoustic waves remain modulationally stable against oblique perturbations
Truncation correction for oblique filtering lines
International Nuclear Information System (INIS)
Hoppe, Stefan; Hornegger, Joachim; Lauritsch, Guenter; Dennerlein, Frank; Noo, Frederic
2008-01-01
State-of-the-art filtered backprojection (FBP) algorithms often define the filtering operation to be performed along oblique filtering lines in the detector. A limited scan field of view leads to the truncation of those filtering lines, which causes artifacts in the final reconstructed volume. In contrast to the case where filtering is performed solely along the detector rows, no methods are available for the case of oblique filtering lines. In this work, the authors present two novel truncation correction methods which effectively handle data truncation in this case. Method 1 (basic approach) handles data truncation in two successive preprocessing steps by applying a hybrid data extrapolation method, which is a combination of a water cylinder extrapolation and a Gaussian extrapolation. It is independent of any specific reconstruction algorithm. Method 2 (kink approach) uses similar concepts for data extrapolation as the basic approach but needs to be integrated into the reconstruction algorithm. Experiments are presented from simulated data of the FORBILD head phantom, acquired along a partial-circle-plus-arc trajectory. The theoretically exact M-line algorithm is used for reconstruction. Although the discussion is focused on theoretically exact algorithms, the proposed truncation correction methods can be applied to any FBP algorithm that exposes oblique filtering lines.
Non-aligned pulsar magnetosphere: an illustrative model for small obliquity
Energy Technology Data Exchange (ETDEWEB)
Mestel, L.; Wang, Y.M. (Sussex Univ., Brighton (UK). Astronomy Centre)
1982-02-01
The electromagnetic field outside a pulsar of small obliquity is approximated by Goldreich-Julian (GJ) conditions out to the light-cylinder and by an outgoing vacuum wave beyond, matched by the appropriate surface charge-current distribution. The energy supply for the wave requires current flow between the pulsar and the light-cylinder. As in the earlier proposal for the aligned rotator, the cold electrons carrying the current achieve relativistic energies near the light-cylinder; the consequent inertial and radiation damping forces enable the electrons to drift across the field-lines and so complete their circuits back to the pulsar. It is hypothesized that low-obliquity pulsars are essentially emitters of a plasma-modified low-frequency wave and of gamma-radiation near the light-cylinder. Illustrative models are constructed as perturbations about an analogous approximate model for the aligned case. The precessional torque component accompanying the braking component acts so as to reduce the obliquity. As long as the obliquity is not too large there is no prima facie objection to non-relativistic flow near the star. It is emphasized that fully self-consistent models will have a smooth rather than a sharp transition between the GJ and vacuum domains.
The non-aligned pulsar magnetosphere: an illustrative model for small obliquity
International Nuclear Information System (INIS)
Mestel, L.; Wang, Y.M.
1982-01-01
The electromagnetic field outside a pulsar of small obliquity is approximated by Goldreich-Julian (GJ) conditions out to the light-cylinder and by an outgoing vacuum wave beyond, matched by the appropriate surface charge-current distribution. The energy supply for the wave requires current flow between the pulsar and the light-cylinder. As in the earlier proposal for the aligned rotator, the cold electrons carrying the current achieve relativistic energies near the light-cylinder; the consequent inertial and radiation damping forces enable the electrons to drift across the field-lines and so complete their circuits back to the pulsar. It is hypothesized that low-obliquity pulsars are essentially emitters of a plasma-modified low-frequency wave and of gamma-radiation near the light-cylinder. Illustrative models are constructed as perturbations about an analogous approximate model for the aligned case. The precessional torque component accompanying the braking component acts so as to reduce the obliquity. As long as the obliquity is not too large there is no prima facie objection to non-relativistic flow near the star. It is emphasized that fully self-consistent models will have a smooth rather than a sharp transition between the GJ and vacuum domains. (author)
Cross effects on electron-cyclotron and lower-hybrid current drive in tokamak plasmas
International Nuclear Information System (INIS)
Fidone, I.; Giruzzi, G.; Krivenski, V.; Mazzucato, E.; Ziebell, L.F.
1986-11-01
Electron cyclotron resonance current drive in a tokamak plasma in the presence of a lower hybrid tail is investigated using a 2D Fokker-Planck code. For an extraordinary mode at oblique propagation and down-shifted frequency it is shown that the efficiency of electron cyclotron current drive becomes, i) substantially greater than the corresponding efficiency of a Maxwellian plasma at the same bulk temperature, ii) equal or greater than that of the lower hybrid waves, iii) comparable with the efficiency of a Maxwellian plasma at much higher temperature. This enhancement results from a beneficial cross-effect of the two waves on the formation of the current carrying electron tail. (5 fig; 17 refs)
Khan, Arif O
2012-06-01
In unilateral congenital superior oblique palsy, a large hypertropia is sometimes associated with ipsilateral contracture of the superior rectus muscle and apparent overaction of the contralateral superior oblique. Ipsilateral double elevator weakening is one surgical approach; however, this procedure could compromise supraduction. We report a series of three consecutive patients who underwent ipsilateral superior rectus and inferior oblique recessions for unilateral superior oblique palsy. Intraoperatively, all three patients were found to have a lax ipsilateral superior oblique tendon. Postoperatively, all three patients had satisfactory correction of the hypertropia and abnormal head position with minimal supraduction defect. This procedure seems to be an acceptable initial surgical option for treating congenital superior oblique muscle palsy with ipsilateral contracture of the superior rectus muscle, even when the ipsilateral superior oblique tendon is lax. Copyright © 2012 American Association for Pediatric Ophthalmology and Strabismus. Published by Mosby, Inc. All rights reserved.
Plasma waves in an inhomogeneous cylindrical plasma
International Nuclear Information System (INIS)
Pesic, S.S.
1976-01-01
The complete dispersion equation governing small amplitude plasma waves propagating in an inhomogeneous cylindrical plasma confined by a helical magnetic field is solved numerically. The efficiency of the wave energy thermalization in the lower hybrid frequency range is studied
International Nuclear Information System (INIS)
Wan, A.S.; Cauble, R.; Da Silva, L.B.; Libby, S.B.; Moreno, J.C.
1996-02-01
This report summarizes the major accomplishments of this three-year Laboratory Directed Research and Development (LDRD) Exploratory Research Project (ERP) entitled ''X-ray Laser Propagation and Coherence: Diagnosing Fast-evolving, High-density Laser Plasmas Using X-ray Lasers,'' tracking code 93-ERP-075. The most significant accomplishment of this project is the demonstration of a new laser plasma diagnostic: a soft x-ray Mach-Zehnder interferometer using a neonlike yttrium x-ray laser at 155 angstrom as the probe source. Detailed comparisons of absolute two-dimensional electron density profiles obtained from soft x-ray laser interferograms and profiles obtained from radiation hydrodynamics codes, such as LASNEX, will allow us to validate and benchmark complex numerical models used to study the physics of laser-plasma interactions. Thus the development of soft x-ray interferometry technique provides a mechanism to probe the deficiencies of the numerical models and is an important tool for, the high-energy density physics and science-based stockpile stewardship programs. The authors have used the soft x-ray interferometer to study a number of high-density, fast evolving, laser-produced plasmas, such as the dynamics of exploding foils and colliding plasmas. They are pursuing the application of the soft x-ray interferometer to study ICF-relevant plasmas, such as capsules and hohlraums, on the Nova 10-beam facility. They have also studied the development of enhanced-coherence, shorter-pulse-duration, and high-brightness x-ray lasers. The utilization of improved x-ray laser sources can ultimately enable them to obtain three-dimensional holographic images of laser-produced plasmas
International Nuclear Information System (INIS)
Vuković, Slobodan M; Miret, Juan J; Zapata-Rodriguez, Carlos J; Jakšić, Zoran
2012-01-01
We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal-dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal-dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.
Radio frequency sheaths in an oblique magnetic field
International Nuclear Information System (INIS)
Myra, J. R.; D'Ippolito, D. A.
2015-01-01
The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describes the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle θ, assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numerically to obtain the rectified (dc) voltage, the rf voltage across the sheath, and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general, the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall
Directory of Open Access Journals (Sweden)
S. S. Ghosh
2004-01-01
Full Text Available The presence of dynamic, large amplitude solitary waves in the auroral regions of space is well known. Since their velocities are of the order of the ion acoustic speed, they may well be considered as being generated from the nonlinear evolution of ion acoustic waves. However, they do not show the expected width-amplitude correlation for K-dV solitons. Recent POLAR observations have actually revealed that the low altitude rarefactive ion acoustic solitary waves are associated with an increase in the width with increasing amplitude. This indicates that a weakly nonlinear theory is not appropriate to describe the solitary structures in the auroral regions. In the present work, a fully nonlinear analysis based on Sagdeev pseudopotential technique has been adopted for both parallel and oblique propagation of rarefactive solitary waves in a two electron temperature multi-ion plasma. The large amplitude solutions have consistently shown an increase in the width with increasing amplitude. The width-amplitude variation profile of obliquely propagating rarefactive solitary waves in a magnetized plasma have been compared with the recent POLAR observations. The width-amplitude variation pattern is found to fit well with the analytical results. It indicates that a fully nonlinear theory of ion acoustic solitary waves may well explain the observed anomalous width variations of large amplitude structures in the auroral region.
Study of beam-plasma interactions in the presence of a magnetic field
International Nuclear Information System (INIS)
Etievant, C.
1963-12-01
The instabilities developing in a 'beam-plasma' system and in a 'double-beam' system in the presence of a magnetic field are discussed theoretically starting from the conductivity tensor expression for a multi-beam system. Oblique propagation is taken into account and this leads to the introduction of certain instability mechanisms which would not appear in the case of a propagation which is purely parallel or perpendicular to the magnetic field. Two experiments are described: a) Study of the collision of two counterstreaming electron beams: An instability has been observed experimentally which leads to the generation of a stationary cyclotron wave having a frequency of ω ce /2. A description is given of the measurement of the interaction frequency, of the wavelength and of the build-up time of the wave. b) Study of a 'beam-plasma' system: A description is given of the measurement of the spectra of excited waves and of the perturbation of the beam velocity distribution at the plasma-exit. This perturbation is very pronounced when 'plasma-plasma' interaction appears in the system. A study into cyclotron oscillations produced in the plasma by excitation due to the passage of the beam is also described in this report. (author) [fr
Obliquely Incident Solitary Wave onto a Vertical Wall
Yeh, Harry
2012-10-01
When a solitary wave impinges obliquely onto a reflective vertical wall, it can take the formation of a Mach reflection (a geometrically similar reflection from acoustics). The mathematical theory predicts that the wave at the reflection can amplify not twice, but as high as four times the incident wave amplitude. Nevertheless, this theoretical four-fold amplification has not been verified by numerical or laboratory experiments. We discuss the discrepancies between the theory and the experiments; then, improve the theory with higher-order corrections. The modified theory results in substantial improvement and is now in good agreement with the numerical as well as our laboratory results. Our laboratory experiments indicate that the wave amplitude along the reflective wall can reach 0.91 times the quiescent water depth, which is higher than the maximum of a freely propagating solitary wave. Hence, this maximum runup 0.91 h would be possible even if the amplitude of the incident solitary wave were as small as 0.24 h. This wave behavior could provide an explanation for local variability of tsunami runup as well as for sneaker waves.
Behavior of obliquely incident vector Bessel beams at planar interfaces
Salem, Mohamed
2013-01-01
We investigate the behavior of full-vector electromagnetic Bessel beams obliquely incident at an interface between two electrically different media. We employ a Fourier transform domain representation of Bessel beams to determine their behavior upon reflection and transmission. This transform, which is geometric in nature, consists of elliptical support curves with complex weighting associated with them. The behavior of the scattered field at an interface is highly complex, owing to its full-vector nature; nevertheless, this behavior has a straightforward representation in the transform domain geometry. The analysis shows that the reflected field forms a different vector Bessel beam, but in general, the transmitted field cannot be represented as a Bessel beam. Nevertheless, using this approach, we demonstrate a method to propagate a Bessel beam in the refractive medium by launching a non- Bessel beam at the interface. Several interesting phenomena related to the behavior of Bessel beams are illustrated, such as polarized reflection at Brewster\\'s angle incidence, and the Goos-Hänchen and Imbert-Federov shifts in the case of total reflection. © 2013 Optical Society of America.
Behavior of obliquely incident vector Bessel beams at planar interfaces
Salem, Mohamed; Bagci, Hakan
2013-01-01
We investigate the behavior of full-vector electromagnetic Bessel beams obliquely incident at an interface between two electrically different media. We employ a Fourier transform domain representation of Bessel beams to determine their behavior upon reflection and transmission. This transform, which is geometric in nature, consists of elliptical support curves with complex weighting associated with them. The behavior of the scattered field at an interface is highly complex, owing to its full-vector nature; nevertheless, this behavior has a straightforward representation in the transform domain geometry. The analysis shows that the reflected field forms a different vector Bessel beam, but in general, the transmitted field cannot be represented as a Bessel beam. Nevertheless, using this approach, we demonstrate a method to propagate a Bessel beam in the refractive medium by launching a non- Bessel beam at the interface. Several interesting phenomena related to the behavior of Bessel beams are illustrated, such as polarized reflection at Brewster's angle incidence, and the Goos-Hänchen and Imbert-Federov shifts in the case of total reflection. © 2013 Optical Society of America.
Bhakta, S.; Prajapati, R. P.; Dolai, B.
2017-08-01
The small amplitude quantum magnetohydrodynamic (QMHD) waves and linear firehose and mirror instabilities in uniformly rotating dense quantum plasma have been investigated using generalized polytropic pressure laws. The QMHD model and Chew-Goldberger-Low (CGL) set of equations are used to formulate the basic equations of the problem. The general dispersion relation is derived using normal mode analysis which is discussed in parallel, transverse, and oblique wave propagations. The fast, slow, and intermediate QMHD wave modes and linear firehose and mirror instabilities are analyzed for isotropic MHD and CGL quantum fluid plasmas. The firehose instability remains unaffected while the mirror instability is modified by polytropic exponents and quantum diffraction parameter. The graphical illustrations show that quantum corrections have a stabilizing influence on the mirror instability. The presence of uniform rotation stabilizes while quantum corrections destabilize the growth rate of the system. It is also observed that the growth rate stabilizes much faster in parallel wave propagation in comparison to the transverse mode of propagation. The quantum corrections and polytropic exponents also modify the pseudo-MHD and reverse-MHD modes in dense quantum plasma. The phase speed (Friedrichs) diagrams of slow, fast, and intermediate wave modes are illustrated for isotropic MHD and double adiabatic MHD or CGL quantum plasmas, where the significant role of magnetic field and quantum diffraction parameters on the phase speed is observed.
Natural Vibration of a Beam with a Breathing Oblique Crack
Directory of Open Access Journals (Sweden)
Yijiang Ma
2017-01-01
Full Text Available An analytical method is proposed to calculate the natural frequency of a cantilever beam with a breathing oblique crack. A double-linear-springs-model is developed in the modal analysis process to describe the breathing oblique crack, and the breathing behaviour of the oblique crack is objectively simulated. The finite element method (FEM analysis software ABAQUS is used to calculate the geometric correction factors when the cracked plate is subjected to a pure bending moment at different oblique crack angles and relative depths. The Galerkin method is applied to simplify the cracked beam to a single degree of freedom system, allowing the natural frequency of the beam with the breathing oblique crack to be calculated. Compared with the natural frequencies of the breathing oblique cracked beam obtained using the ABAQUS FEM method, the proposed analytical method exhibits a high computational accuracy, with a maximum error of only 4.65%.
Moore, M. R.
2012-10-02
A minor error in Howison et al. (J. Eng. Math. 48:321-337, 2004) obscured the fact that the points at which the free surface turns over in the solution of the Wagner model for the oblique impact of a two-dimensional body are directly related to the turnover points in the equivalent normal impact problem. This note corrects some of the earlier results given in Howison et al. (J. Eng. Math. 48:321-337, 2004) and discusses the implications for the applicability of the Wagner model. © 2012 Springer Science+Business Media B.V.
Flow and sediment transport across oblique channels
DEFF Research Database (Denmark)
Hjelmager Jensen, Jacob; Madsen, Erik Østergaard; Fredsøe, Jørgen
1998-01-01
A 3D numerical investigation of flow across channels aligned obliquely to the main flow direction has been conducted. The applied numerical model solves the Reynolds-averaged Navier-Stokes equations using the k-ε model for turbulence closure on a curvilinear grid. Three momentum equations...... are solved, but the computational domain is 2D due to a uniformity along the channel alignment. Two important flow features arise when the flow crosses the channel: (i) the flow will be refracted in the direction of the channel alignment. This may be described by a depth-averaged model. (ii) due to shear...
Theory and analysis of a large field polarization imaging system with obliquely incident light.
Lu, Xiaotian; Jin, Weiqi; Li, Li; Wang, Xia; Qiu, Su; Liu, Jing
2018-02-05
Polarization imaging technology provides information about not only the irradiance of a target but also the polarization degree and angle of polarization, which indicates extensive application potential. However, polarization imaging theory is based on paraxial optics. When a beam of obliquely incident light passes an analyser, the direction of light propagation is not perpendicular to the surface of the analyser and the applicability of the traditional paraxial optical polarization imaging theory is challenged. This paper investigates a theoretical model of a polarization imaging system with obliquely incident light and establishes a polarization imaging transmission model with a large field of obliquely incident light. In an imaging experiment with an integrating sphere light source and rotatable polarizer, the polarization imaging transmission model is verified and analysed for two cases of natural light and linearly polarized light incidence. Although the results indicate that the theoretical model is consistent with the experimental results, the theoretical model distinctly differs from the traditional paraxial approximation model. The results prove the accuracy and necessity of the theoretical model and the theoretical guiding significance for theoretical and systematic research of large field polarization imaging.
Plasma microinstabilities driven by loss-cone distributions
International Nuclear Information System (INIS)
Summers, D.; Thorne, R.M.
1995-01-01
Electromagnetic and electrostatic instabilities driven by loss-cone particle distributions have been invoked to explain a variety of plasma phenomena observed in space and in the laboratory. In this paper we analyse how the loss-cone feature (as determined by the loss-cone index or indices) influences the growth of such instabilities in a fully ionized, homogeneous, hot plasma in a uniform magnetic field. Specifically, we consider three loss-cone distributions: a generalized Lorentzian (kappa) loss-cone distribution, the Dory-Guest-Harris distribution and the Ashour-Abdalla-Kennel distribution (involving a subtracted Maxwellian). Our findings are common to all three distributions. We find that, for parallel propagation, electromagnetic instabilities are only affected by the loss-cone indices in terms of their occurrence in the temperature anisotropy. However, for oblique propagation, even including propagation at small angles to the ambient magnetic field, the loss-cone indices do independently affect the growth of instabilities for electromagnetic waves, in contrast to certain claims in the literature. For electrostatic waves such that 1/2(κ perpendicular to ρ L σ 2 L σ is the Larmor radius for particle species σ, we find that the loss-cone indices only enter the dispersion equation via the temperature anisotropy, and so in this case the loss-cone feature and perpendicular effective thermal speed do not independently affect wave growth. (Author)
Zhang, Lu; Cheng, Li; Bai, Suo; Su, Chen; Chen, Xiaobo; Qin, Yong
2015-01-01
Ultrafine organic nanowire arrays (ONWAs) with a controlled direction were successfully fabricated by a novel one-step Faraday cage assisted plasma etching method. The mechanism of formation of nanowire arrays is proposed; the obliquity and aspect ratio can be accurately controlled from approximately 0° to 90° via adjusting the angle of the sample and the etching time, respectively. In addition, the ONWAs were further utilized to improve the output of the triboelectric nanogenerator (TENG). Compared with the output of TENG composed of vertical ONWAs, the open-circuit voltage, short-circuit current and inductive charges were improved by 73%, 150% and 98%, respectively. This research provides a convenient and practical method to fabricate ONWAs with various obliquities on different materials, which can be used for energy harvesting.
International Nuclear Information System (INIS)
Hermansson, B.R.
1989-01-01
The main part of this thesis consists of 15 published papers, in which the numerical Beam Propagating Method (BPM) is investigated, verified and used in a number of applications. In the introduction a derivation of the nonlinear Schroedinger equation is presented to connect the beginning of the soliton papers with Maxwell's equations including a nonlinear polarization. This thesis focuses on the wide use of the BPM for numerical simulations of propagating light and particle beams through different types of structures such as waveguides, fibers, tapers, Y-junctions, laser arrays and crystalline solids. We verify the BPM in the above listed problems against other numerical methods for example the Finite-element Method, perturbation methods and Runge-Kutta integration. Further, the BPM is shown to be a simple and effective way to numerically set up the Green's function in matrix form for periodic structures. The Green's function matrix can then be diagonalized with matrix methods yielding the eigensolutions of the structure. The BPM inherent transverse periodicity can be untied, if desired, by for example including an absorptive refractive index at the computational window edges. The interaction of two first-order soliton pulses is strongly dependent on the phase relationship between the individual solitons. When optical phase shift keying is used in coherent one-carrier wavelength communication, the fiber attenuation will suppress or delay the nonlinear instability. (orig.)
Propagation of microwaves in pulsar magnetospheres
Energy Technology Data Exchange (ETDEWEB)
Bodo, G; Ferrari, A [Turin Univ. (Italy). Ist. di Fisica Generale; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica); Massaglia, S [Turin Univ. (Italy). Ist. di Fisica Generale; Cambridge Univ. (UK). Inst. of Astronomy)
1981-12-01
We discuss the dispersion relation of linearly-polarized waves, propagating along a strong background magnetic field embedded in an electron-positron plasma. The results are then applied to the study of the propagation conditions of coherent curvature radio radiation inside neutron stars magnetospheres, as produced by electric discharges following current pulsar models.
Energy Technology Data Exchange (ETDEWEB)
Gomez R, F. [UAEM, A.P. 2-139, 50000 Toluca, Estado de Mexico (Mexico); Ondarza R, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)
2004-07-01
An analytical model for the description of the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized propagating along of a static and homogeneous external magnetic field in a plasma starting from the force equation is presented. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary amplitude and modulated by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radiative effects. (Author)
Energy Technology Data Exchange (ETDEWEB)
Gomez R, F. [UAEM, Facultad de Ciencias, 50000 Toluca, Estado de Mexico (Mexico); Ondarza R, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)
2004-07-01
An analytic model is presented for the description of the motion of a charged particle in the interaction of an elliptically electromagnetic pulse polarized propagating along a static and homogeneous external magnetic field in a plasma starting from the force equation. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary and modulated width by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radioactive effects. (Author)
Directory of Open Access Journals (Sweden)
Yang Zhang
2014-05-01
Full Text Available AIM: To investigate the viability of the morphology of inferior oblique muscle observed stereoscopically using 3-dimensional CT reconstruction technique. METHODS: This control study included of 29 cases which were clinically diagnosed with monocular congenital superior oblique palsy, examined by dimensional CT. The images of the inferior oblique muscle were reconstructed by Mimics software. 3D digital images on the basis of CT scanning data of the individuals were established. Observing the morphology of binocular inferior oblique muscle by self-controlled design, we compared the maximum transverse diameter of inferior oblique muscle of paralyzed eye with non-paralyzed one. We chose 5% as the significant level.RESULTS: The reconstructed results of 3-dimensional CT scan showed that not all of the inferior oblique abdominal muscle of paralyzed eyes were thinner than that of the non-paralyzed eye in maximum transverse diameter of cross-sectional area. The maximum transverse diameter of inferior oblique muscle was measured. The average maximum transverse diameter of the paralyzed eye was 6.797±1.083mm and the non-paralyzed eye was 6.507±0.848mm. The maximum transverse diameter of inferior oblique muscle of paralyzed eye did not, however, differ significantly from the normal(P>0.05. CONCLUSION: The three-dimensional CT reconstruction technology can be used for preoperative evaluation of the morphology of inferior oblique muscle.
Oblique and lateral impact response of the PMHS thorax.
Shaw, Joshua M; Herriott, Rodney G; McFadden, Joseph D; Donnelly, Bruce R; Bolte, John H
2006-11-01
This study characterizes the PMHS thoracic response to blunt impact in oblique and lateral directions. A significant amount of data has been collected from lateral impacts conducted on human cadavers. Substantially less data has been collected from impacts that are anterior of lateral in an oblique direction. In the past, data collected from the handful of oblique impact studies were considered to be similar enough to the data from purely lateral impacts such that the oblique data were combined with data from lateral impacts. Defining the biomechanical response of the PMHS thorax to oblique impact is of great importance in side impact vehicle crashes where the loading is often anterior-oblique in direction. Data in this study was obtained from a chestband placed on the thorax at the level of impact to measure thoracic deflection. Two low energy impacts were conducted on each of seven subjects at 2.5 m/s, with one lateral impact and one oblique impact to opposite sides of each PMHS. Data was normalized using the Mertz-Viano method for a two mass system to allow for inter-subject comparisons. Force versus deflection response corridors were generated for the two impact types using an objective mathematical approach and compared to one another. Results were also compared to existing data for oblique and lateral thoracic impacts. The oblique thoracic response in low speed pendulum impacts was found to be different than the lateral thoracic response, in terms of force and deflection. Specifically, the lateral force was greater than the oblique force, and oblique deflection greater than lateral deflection for equal energy impacts.
33 CFR 118.90 - Bridges crossing channel obliquely.
2010-07-01
... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Bridges crossing channel obliquely. 118.90 Section 118.90 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES BRIDGE LIGHTING AND OTHER SIGNALS § 118.90 Bridges crossing channel obliquely. Bridges...
Reduced Oblique Effect in Children with Autism Spectrum Disorders (ASD)
Sysoeva, Olga V.; Davletshina, Maria A.; Orekhova, Elena V.; Galuta, Ilia A.; Stroganova, Tatiana A.
2016-01-01
People are very precise in the discrimination of a line orientation relative to the cardinal (vertical and horizontal) axes, while their orientation discrimination sensitivity along the oblique axes is less refined. This difference in discrimination sensitivity along cardinal and oblique axes is called the “oblique effect.” Given that the oblique effect is a basic feature of visual processing with an early developmental origin, its investigation in children with Autism Spectrum Disorder (ASD) may shed light on the nature of visual sensory abnormalities frequently reported in this population. We examined line orientation sensitivity along oblique and vertical axes in a sample of 26 boys with ASD (IQ > 68) and 38 typically developing (TD) boys aged 7–15 years, as well as in a subsample of carefully IQ-matched ASD and TD participants. Children were asked to detect the direction of tilt of a high-contrast black-and-white grating relative to vertical (90°) or oblique (45°) templates. The oblique effect was reduced in children with ASD as compared to TD participants, irrespective of their IQ. This reduction was due to poor orientation sensitivity along the vertical axis in ASD children, while their ability to discriminate line orientation along the oblique axis was unaffected. We speculate that this deficit in sensitivity to vertical orientation may reflect disrupted mechanisms of early experience-dependent learning that takes place during the critical period for orientation selectivity. PMID:26834540
Joshi, D. R.; Groves, K. M.
2015-12-01
The Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud. A host of diagnostic instruments were used to probe and characterize the cloud including the ALTAIR incoherent scatter radar, multiple GPS and optical instruments, satellite radio beacons, and a dedicated network of high frequency (HF) radio links. Data from ALTAIR incoherent scatter radar and HF radio links have been analyzed to understand the impacts of the artificial ionization on radio wave propagation. During the first release the ionosphere was disturbed, rising rapidly and spread F formed within minutes after the release. To address the disturbed conditions present during the first release, we have developed a new method of assimilating oblique ionosonde data to generate the background ionosphere that can have numerous applications for HF systems. The link budget analysis of the received signals from the HF transmitters explains the missing low frequencies in the received signals along the great circle path. Observations and modeling confirm that the small amounts of ionized material injected in the lower-F region resulted in significant changes to the natural propagation environment.
The oblique cord of the forearm in man.
Tubbs, R Shane; O'Neil, James T; Key, Christopher D; Zarzour, Jessica G; Fulghum, Sarah B; Kim, Eugenia J; Lyerly, Michael J; Shoja, Mohammadali M; George Salter, E; Jerry Oakes, W
2007-05-01
There is minimal and often conflicting data in the literature regarding the oblique cord of the forearm. The current study seeks to elucidate further the anatomy of this structure of the upper extremity. In adult cadavers, the oblique cord was observed for and, when found, measurements were made of it. Ranges of motion were carried out while observation of the oblique cord was made. An oblique cord was found on 52.6% of sides. Gantzer's muscle was found on 55% of sides and, when present, had attachment into the oblique cord on five sides. The oblique cord was present on 13 sides with a Gantzer's muscle. Of the 20 sides with an oblique cord, no Gantzer's muscle was found on 10. The mean length of the oblique cord was 3.4 cm. In the majority of specimens, this cord tapered from proximal to distal. The proximal, middle, and distal widths of this structure had means 9, 7, and 4 mm, respectively. The oblique cord was found to travel approximately 45 degrees from a line drawn through the ulna and more or less traveled perpendicular to the insertion site of the bicipital tendon. This ligament was lax in the neutral position and with pronation became lax in all specimens. The oblique cord progressively became taut with increased supination from the neutral position and was maximally taut with the forearm fully supinated. Tautness of this cord was also found with distal distraction of the radius. Following the transection of the oblique cord, no discernable difference was observed in regard to maximal supination of the forearm or distal distraction of the radius. No obvious instability of the proximal forearm was found following transection of the oblique cord. Functionally, although the oblique cord may resist supination, it is unlikely that this structure affords significant stability to the proximal forearm, as it was often absent, of a very small caliber, and based on our observations, following its transection, the amount of supination of the forearm did not increase
International Nuclear Information System (INIS)
Malekynia, B.; Razavipour, S. S.
2013-01-01
An accelerated skin layer may be used to ignite solid state fuels. Detailed analyses were clarified by solving the hydrodynamic equations for nonlinear force driven plasma block ignition. In this paper, the complementary mechanisms are included for the advanced fuel ignition: external factors such as lasers, compression, shock waves, and sparks. The other category is created within the plasma fusion as reheating of an alpha particle, the Bremsstrahlung absorption, expansion, conduction, and shock waves generated by explosions. With the new condition for the control of shock waves, the spherical deuterium-tritium fuel density should be increased to 75 times that of the solid state. The threshold ignition energy flux density for advanced fuel ignition may be obtained using temperature equations, including the ones for the density profile obtained through the continuity equation and the expansion velocity for the r ≠ 0 layers. These thresholds are significantly reduced in comparison with the ignition thresholds at x = 0 for solid advanced fuels. The quantum correction for the collision frequency is applied in the case of the delay in ion heating. Under the shock wave condition, the spherical proton-boron and proton-lithium fuel densities should be increased to densities 120 and 180 times that of the solid state. These plasma compressions are achieved through a longer duration laser pulse or X-ray. (physics of gases, plasmas, and electric discharges)
Sadeghi, S.; Yassaghi, A.
2015-09-01
Stratigraphy, detailed structural mapping and crustal scale cross section of the NW Zagros collision zone evolved during convergence of the Arabian and Eurasian plates were conducted to constrain the spatial evolution of the belt oblique convergence since Late Cretaceous. Zagros orogeny in NW Iran consists of the Sanandaj-Sirjan, Gaveh Rud and ophiolite zones as internal, and Bisotoun, Radiolarite and High Zagros zones as external parts. The Main Zagros Thrust is known as major structures of the Zagros suture zone. Two stages of deformation are recognized in the external parts of Zagros. In the early stage, presence of dextrally deformed domains beside the reversely deformed domains in the Radiolarite zone as well as dextral-reverse faults in both Bisotoun and Radiolarite zones demonstrates partitioning of the dextral transpression. In the late stage, southeastward propagation of the Zagros orogeny towards its foreland resulted in synchronous development of orogen-parallel strike-slip and pure thrust faults. It is proposed that the first stage related to the late Cretaceous oblique obduction, and the second stage is resulted from Cenozoic collision. Cenozoic orogen-parallel strike-slip component of Zagros oblique faulting is not confined to the Zagros suture zone (Main Recent) but also occurred in the more external part (Marekhil-Ravansar fault system). Thus, it is proposed that oblique convergence of Arabia-Eurasia plates occurred in Zagros collision zone since the Late Cretaceous.
Theory of the collisional presheath in an oblique magnetic field
International Nuclear Information System (INIS)
Riemann, K.
1994-01-01
In the limit of a small Debye length (λ D →0), the plasma boundary layer in front of a negative absorbing wall is split up into a collision-free planar space charge sheath and a quasineutral presheath, where the ions are accelerated to ion sound speed (Bohm criterion). Usually the presheath mechanism depends decisively on collisional friction of the ions, on ionization, or on geometric ion current concentration. If the ion dynamics in the presheath is dominated by a magnetic field (nearly) parallel to the wall, an additional effect must be considered to provide an ion transport to the wall. The special cases (a) of an ion transport by field lines intersecting the wall at a finite angle and (b) of an ion transport by collisions result in somewhat contradictory conclusions. To get a coherent picture, a hydrodynamic model of the presheath is investigated accounting for an oblique magnetic field and for collisions. The limiting cases (a) and (b) are discussed, and it is shown that (in plane geometry) the presheath ion acceleration depends always on elementary processes. The main effect of a strong magnetic field is to ''compress'' the collisional presheath into a thin layer with a characteristic extension of the ion gyroradius ρ i
Characterization of Oblique Dual Frame Pairs
Directory of Open Access Journals (Sweden)
Christensen Ole
2006-01-01
Full Text Available Given a frame for a subspace of a Hilbert space , we consider all possible families of oblique dual frame vectors on an appropriately chosen subspace . In place of the standard description, which involves computing the pseudoinverse of the frame operator, we develop an alternative characterization which in some cases can be computationally more efficient. We first treat the case of a general frame on an arbitrary Hilbert space, and then specialize the results to shift-invariant frames with multiple generators. In particular, we present explicit versions of our general conditions for the case of shift-invariant spaces with a single generator. The theory is also adapted to the standard frame setting in which the original and dual frames are defined on the same space.
CALIBRATION PROCEDURES ON OBLIQUE CAMERA SETUPS
Directory of Open Access Journals (Sweden)
G. Kemper
2016-06-01
Full Text Available Beside the creation of virtual animated 3D City models, analysis for homeland security and city planning, the accurately determination of geometric features out of oblique imagery is an important task today. Due to the huge number of single images the reduction of control points force to make use of direct referencing devices. This causes a precise camera-calibration and additional adjustment procedures. This paper aims to show the workflow of the various calibration steps and will present examples of the calibration flight with the final 3D City model. In difference to most other software, the oblique cameras are used not as co-registered sensors in relation to the nadir one, all camera images enter the AT process as single pre-oriented data. This enables a better post calibration in order to detect variations in the single camera calibration and other mechanical effects. The shown sensor (Oblique Imager is based o 5 Phase One cameras were the nadir one has 80 MPIX equipped with a 50 mm lens while the oblique ones capture images with 50 MPix using 80 mm lenses. The cameras are mounted robust inside a housing to protect this against physical and thermal deformations. The sensor head hosts also an IMU which is connected to a POS AV GNSS Receiver. The sensor is stabilized by a gyro-mount which creates floating Antenna –IMU lever arms. They had to be registered together with the Raw GNSS-IMU Data. The camera calibration procedure was performed based on a special calibration flight with 351 shoots of all 5 cameras and registered the GPS/IMU data. This specific mission was designed in two different altitudes with additional cross lines on each flying heights. The five images from each exposure positions have no overlaps but in the block there are many overlaps resulting in up to 200 measurements per points. On each photo there were in average 110 well distributed measured points which is a satisfying number for the camera calibration. In a first
Wave propagation in electromagnetic media
International Nuclear Information System (INIS)
Davis, J.L.
1990-01-01
This book is concerned with wave propagation in reacting media, specifically in electromagnetic materials. An account is presented of the mathematical methods of wave phenomena in electromagnetic materials. The author presents the theory of time-varying electromagnetic fields, which involves a discussion of Faraday's laws, Maxwell's equations and their application to electromagnetic wave propagation under a variety of conditions. The author gives a discussion of magnetohydrodynamics and plasma physics. Chapters are included on quantum mechanics and the theory of relativity. The mathematical foundation of electromagnetic waves vis a vis partial differential equations is discussed
Hsieh, Yi-Kai; Omura, Yoshiharu
2017-10-01
We investigate the properties of whistler mode wave-particle interactions at oblique wave normal angles to the background magnetic field. We find that electromagnetic energy of waves at frequencies below half the electron cyclotron frequency can flow nearly parallel to the ambient magnetic field. We thereby confirm that the gyroaveraging method, which averages the cyclotron motion to the gyrocenter and reduces the simulation from two-dimensional to one-dimensional, is valid for oblique wave-particle interaction. Multiple resonances appear for oblique propagation but not for parallel propagation. We calculate the possible range of resonances with the first-order resonance condition as a function of electron kinetic energy and equatorial pitch angle. To reveal the physical process and the efficiency of electron acceleration by multiple resonances, we assume a simple uniform wave model with constant amplitude and frequency in space and time. We perform test particle simulations with electrons starting at specific equatorial pitch angles and kinetic energies. The simulation results show that multiple resonances contribute to acceleration and pitch angle scattering of energetic electrons. Especially, we find that electrons with energies of a few hundred keV can be accelerated efficiently to a few MeV through the n = 0 Landau resonance.
Lee, Myoung-Jae; Jung, Young-Dae
2018-05-01
The dispersion properties of surface dust ion-acoustic waves in a self-gravitating magnetized dusty plasma layer with the (r, q) distribution are investigated. The result shows that the wave frequency of the symmetric mode in the plasma layer decreases with an increase in the wave number. It is also shown that the wave frequency of the symmetric mode decreases with an increase in the spectral index r. However, the wave frequency of the anti-symmetric mode increases with an increase in the wave number. It is also found that the anti-symmetric mode wave frequency increases with an increase in the spectral index r. In addition, it is found that the influence of the self-gravitation on the symmetric mode wave frequency decreases with increasing scaled Jeans frequency. Moreover, it is found that the wave frequency of the symmetric mode increases with an increase in the dust charge; however, the anti-symmetric mode shows opposite behavior.
International Nuclear Information System (INIS)
Talviste, Rasmus; Jõgi, Indrek; Raud, Jüri; Paris, Peeter
2016-01-01
The focus of this study was to investigate the effect of the dielectric tube diameter on the velocity of the ionization wave in an atmospheric pressure plasma jet in He gas flow. Plasma was ignited in quartz tubes with inner diameter in the range of 80–500 μm by 6 kHz sinusoidal voltage applied to a cylindrical electrode surrounding the quartz tube and positioned 10 mm from the tube orifice. A grounded plane was placed 2–3 cm downstream from the powered electrode to measure the plasma current. The spatial development of ionization waves was monitored by registering the optical emission along the axis of the tube. The ionization wave velocity was deduced from the temporal shift of the onset of radiation at different axial positions. The velocity of ionization wave increased by almost an order of magnitude with the tube diameter decreasing from 500 to 80 μm and was for the 80 μm microtube 1.7 · 10 5 m s −1 during the positive half-cycle and 1.45 · 10 5 m s −1 during the negative half-cycle. (paper)
Oblique-view mamography: adequacy for screening. Work in progress
International Nuclear Information System (INIS)
Muir, B.B.; Kirkpatrick, A.E.; Roberts, M.M.; Duffy, S.W.
1984-01-01
Single oblique-view mammography has been recommended for screening purposes. The authors present data indicating that using the oblique view only can allow 11% of cancers to remain undetected. The smallest and potentially curable cancers are most likely to be overlooked in this way; any possible benefit of screening is thereby reduced. Data are also presented to show that 39% of women may require other views, for reasons not necessarily related to cancer detection. It is therefore recommended that all women have four-view mammography (oblique plus craniocaudal views of each breast) at their first screening visit
Bolt beam propagation analysis
Shokair, I. R.
BOLT (Beam on Laser Technology) is a rocket experiment to demonstrate electron beam propagation on a laser ionized plasma channel across the geomagnetic field in the ion focused regime (IFR). The beam parameters for BOLT are: beam current I(sub b) = 100 Amps, beam energy of 1--1.5 MeV (gamma =3-4), and a Gaussian beam and channel of radii r(sub b) = r(sub c) = 1.5 cm. The N+1 ionization scheme is used to ionize atomic oxygen in the upper atmosphere. This scheme utilizes 130 nm light plus three IR lasers to excite and then ionize atomic oxygen. The limiting factor for the channel strength is the energy of the 130 nm laser, which is assumed to be 1.6 mJ for BOLT. At a fixed laser energy and altitude (fixing the density of atomic oxygen), the range can be varied by adjusting the laser tuning, resulting in a neutralization fraction axial profile of the form: f(z) = f(sub 0) e(exp minus z)/R, where R is the range. In this paper we consider the propagation of the BOLT beam and calculate the range of the electron beam taking into account the fact that the erosion rates (magnetic and inductive) vary with beam length as the beam and channel dynamically respond to sausage and hose instabilities.
Nonlinear radial propagation of drift wave turbulence
International Nuclear Information System (INIS)
Prakash, M.
1985-01-01
We study the linear and the nonlinear radial propagation of drift wave energy in an inhomogeneous plasma. The drift mode excited in such a plasma is dispersive in nature. The drift wave energy spreads out symmetrically along the direction of inhomogeneity with a finite group velocity. To study the effect of the nonlinear coupling on the propagation of energy in a collision free plasma, we solve the Hasegawa-Mima equation as a mixed initial boundary-value problem. The solutions of the linearized equation are used to check the reliability of our numerical calculations. Additional checks are also performed on the invariants of the system. Our results reveal that a pulse gets distorted as it propagates through the medium. The peak of the pulse propagates with a finite velocity that depends on the amplitude of the initial pulse. The polarity of propagation depends on the initial parameters of the pulse. We have also studied drift wave propagation in a resistive plasma. The Hasegawa-Wakatani equations are used to investigate this problem
Camere aeree oblique: sistemi, applicazioni e prospettive future
Directory of Open Access Journals (Sweden)
Fabio Remondino
2014-10-01
Full Text Available The use of oblique imagery has become a standard for many civil and mapping applications, thanks to the development of airborne digital multi-camera systems, as proposed by many companies. The indisputable virtue of oblique photography lies in its simplicity of interpretation and understanding for inexperienced users allowing their use of oblique images in very different applications, such as building detection and reconstruction, building structural damage classification, road land updating and administration services, etc. We report an overview of the actual oblique commercial systems and the workflow for the automated orientation and dense matching of large image blocks. Perspectives, potentialities, pitfalls and suggestions for achieving satisfactory results are given too.
Climate Dynamics and Hysteresis at Low and High Obliquity
Colose, C.; Del Genio, A. D.; Way, M.
2017-12-01
We explore the large-scale climate dynamics at low and high obliquity for an Earth-like planet using the ROCKE-3D (Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics) 3-D General Circulation model being developed at NASA GISS as part of the Nexus for Exoplanet System Science (NExSS) initiative. We highlight the role of ocean heat storage and transport in determining the seasonal cycle at high obliquity, and describe the large-scale circulation and resulting regional climate patterns using both aquaplanet and Earth topographical boundary conditions. Finally, we contrast the hysteresis structure to varying CO2 concentration for a low and high obliquity planet near the outer edge of the habitable zone. We discuss the prospects for habitability for a high obliquity planet susceptible to global glaciation.
Oblique Multi-Camera Systems - Orientation and Dense Matching Issues
Rupnik, E.; Nex, F.; Remondino, F.
2014-03-01
The use of oblique imagery has become a standard for many civil and mapping applications, thanks to the development of airborne digital multi-camera systems, as proposed by many companies (Blomoblique, IGI, Leica, Midas, Pictometry, Vexcel/Microsoft, VisionMap, etc.). The indisputable virtue of oblique photography lies in its simplicity of interpretation and understanding for inexperienced users allowing their use of oblique images in very different applications, such as building detection and reconstruction, building structural damage classification, road land updating and administration services, etc. The paper reports an overview of the actual oblique commercial systems and presents a workflow for the automated orientation and dense matching of large image blocks. Perspectives, potentialities, pitfalls and suggestions for achieving satisfactory results are given. Tests performed on two datasets acquired with two multi-camera systems over urban areas are also reported.
Magnetic resonance imaging in congenital superior oblique palsy
International Nuclear Information System (INIS)
Sato, Miho; Kondo, Nagako; Awaya, Shinobu; Nomura, Hideki; Yagasaki, Teiji.
1996-01-01
MRI examinations were carried out on the defined congenital superior oblique palsy in order to distinguish the congenital and acquired palsies. Subjects were 19 patients diagnosed as congenital and their MRI images of 3 or 5 mm-thick coronary slice were taken. The volume of the oblique muscle was calculated from the images and a comparison was made between the diseased and healthy normal sides. The oblique muscle volume at the diseased side was found reduced in most of congenital superior oblique palsy patients. The reduction was observed even at childhood and was thus considered to be a malformation. Further, it is conceivable that the palsy could be caused by the abnormality in the central nervous system as well as by the present anatomical abnormality. (K.H.)
Effects of Extreme Obliquity Variations on the Habitability of Exoplanets
Armstrong, J. C.; Barnes, R.; Domagal-Goldman, S.; Breiner, J.; Quinn, T. R.; Meadows, V. S.
2014-01-01
We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large-amplitude, high-frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, increasing the outer edge of the habitable zone. We restricted our exploration to hypothetical systems consisting of a solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We verified that these systems are stable for 108 years with N-body simulations and calculated the obliquity variations induced by the orbital evolution of the Earth-mass planet and a torque from the host star. We ran a simplified energy balance model on the terrestrial planet to assess surface temperature and ice coverage on the planet's surface, and we calculated differences in the outer edge of the habitable zone for planets with rapid obliquity variations. For each hypothetical system, we calculated the outer edge of habitability for two conditions: (1) the full evolution of the planetary spin and orbit and (2) the eccentricity and obliquity fixed at their average values. We recovered previous results that higher values of fixed obliquity and eccentricity expand the habitable zone, but we also found that obliquity oscillations further expand habitable orbits in all cases. Terrestrial planets near the outer edge of the habitable zone may be more likely to support life in systems that induce rapid obliquity oscillations as opposed to fixed-spin planets. Such planets may be the easiest to directly characterize with space-borne telescopes.
The Oblique Basis Method from an Engineering Point of View
International Nuclear Information System (INIS)
Gueorguiev, V G
2012-01-01
The oblique basis method is reviewed from engineering point of view related to vibration and control theory. Examples are used to demonstrate and relate the oblique basis in nuclear physics to the equivalent mathematical problems in vibration theory. The mathematical techniques, such as principal coordinates and root locus, used by vibration and control theory engineers are shown to be relevant to the Richardson - Gaudin pairing-like problems in nuclear physics.
Effects of extreme obliquity variations on the habitability of exoplanets.
Armstrong, J C; Barnes, R; Domagal-Goldman, S; Breiner, J; Quinn, T R; Meadows, V S
2014-04-01
We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large-amplitude, high-frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, increasing the outer edge of the habitable zone. We restricted our exploration to hypothetical systems consisting of a solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We verified that these systems are stable for 10(8) years with N-body simulations and calculated the obliquity variations induced by the orbital evolution of the Earth-mass planet and a torque from the host star. We ran a simplified energy balance model on the terrestrial planet to assess surface temperature and ice coverage on the planet's surface, and we calculated differences in the outer edge of the habitable zone for planets with rapid obliquity variations. For each hypothetical system, we calculated the outer edge of habitability for two conditions: (1) the full evolution of the planetary spin and orbit and (2) the eccentricity and obliquity fixed at their average values. We recovered previous results that higher values of fixed obliquity and eccentricity expand the habitable zone, but we also found that obliquity oscillations further expand habitable orbits in all cases. Terrestrial planets near the outer edge of the habitable zone may be more likely to support life in systems that induce rapid obliquity oscillations as opposed to fixed-spin planets. Such planets may be the easiest to directly characterize with space-borne telescopes.
Directory of Open Access Journals (Sweden)
Hin On Chu
2017-02-01
Full Text Available Surface Enhanced Raman Spectroscopy presents a rapid, non-destructive method to identify chemical and biological samples with up to single molecule sensitivity. Since its discovery in 1974, the technique has become an intense field of interdisciplinary research, typically generating >2000 publications per year since 2011. The technique relies on the localised surface plasmon resonance phenomenon, where incident light can couple with plasmons at the interface that result in the generation of an intense electric field. This field can propagate from the surface from the metal-dielectric interface, so molecules within proximity will experience more intense Raman scattering. Localised surface plasmon resonance wavelength is determined by a number of factors, such as size, geometry and material. Due to the requirements of the surface optical response, Ag and Au are typical metals used for surface enhanced Raman applications. These metals then need to have nano features that improve the localised surface plasmon resonance, several variants of these substrates exist; surfaces can range from nanoparticles in a suspension, electrochemically roughened electrodes to metal nanostructures on a substrate. The latter will be the focus of this review, particularly reviewing substrates made by oblique angle deposition. Oblique angle deposition is the technique of growing thin films so that the material flux is not normal to the surface. Films grown in this fashion will possess nanostructures, due to the atomic self-shadowing effect, that are dependent mainly on the deposition angle. Recent developments, applications and highlights of surface enhanced Raman scattering substrates made by oblique angle deposition will be reviewed.
Effects of oblique muscle surgery on the rectus muscle pulley
International Nuclear Information System (INIS)
Okanobu, Hirotaka; Kono, Reika; Ohtsuki, Hiroshi
2011-01-01
The purpose of this study was to determine the position of rectus muscle pulleys in Japanese eyes and to evaluate the effect of oblique muscle surgery on rectus muscle pulleys. Quasi-coronal plane MRI was used to determine area centroids of the 4 rectus muscles. The area centroids of the rectus muscles were transformed to 2-dimensional coordinates to represent pulley positions. The effects of oblique muscle surgery on the rectus muscle pulley positions in the coronal plane were evaluated in 10 subjects with cyclovertical strabismus and, as a control, pulley locations in 7 normal Japanese subjects were calculated. The mean positions of the rectus muscle pulleys in the coronal plane did not significantly differ from previous reports on normal populations, including Caucasians. There were significant positional shifts of the individual horizontal and vertical rectus muscle pulleys in 3 (100%) patients with inferior oblique advancement, but not in eyes with inferior oblique recession and superior oblique tendon advancement surgery. The surgical cyclorotatory effect was significantly correlated with the change in the angle of inclination formed by the line connecting the vertical rectus muscles (p=0.0234), but weakly correlated with that of the horizontal rectus muscles. The most important factor that affects the pulley position is the amount of ocular torsion, not the difference in surgical procedure induced by oblique muscle surgery. (author)
International Nuclear Information System (INIS)
Picard, R.R.
1989-01-01
Topics covered in this chapter include a discussion of exact results as related to nuclear materials management and accounting in nuclear facilities; propagation of error for a single measured value; propagation of error for several measured values; error propagation for materials balances; and an application of error propagation to an example of uranium hexafluoride conversion process
Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question
Yang, X; Reboredo Gil, David; Welsh, Gregor H; Li, Y.F; Cipiccia, Silvia; Ersfeld, Bernhard; Grant, D. W; Grant, P. A; Islam, Muhammad; Tooley, M.B; Vieux, Gregory; Wiggins, Sally; Sheng, Zheng-Ming; Jaroszynski, Dino
2017-01-01
Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lowerenergy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5–10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°–60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wake...
International Nuclear Information System (INIS)
Wattellier, Benoit; Fuchs, Julien; Zou Jiping; Chanteloup, Jean-Christophe; Bandulet, Heidi; Michel, Pierre; Labaune, Christine; Depierreux, Sylvie; Kudryashov, Alexis; Aleksandrov, Alexander
2003-01-01
Adaptive optics systems offer the prospect of significantly increasing the capabilities of high-power laser focusability, which is currently limited by thermal distortions. Using novel wave-front measurement techniques that improve the stability of such systems and a downstream large-aperture deformable mirror that does not bear the usual limitations associated with precompensation, we have improved the focusability of a high-power (6x100-J, 1-ns) Nd:glass laser facility by a factor of 6. Measuring the wave front and the on-target focal spot at full power, we obtained after correction focal spots with a best Strehl ratio of 0.6. The pulse peak intensity could thus be increased to ∼2x10 16 W/cm 2 , a level beyond reach of the usual focal spot shaping techniques. We then used the near-diffraction-limited focal spots produced by this system to measure the laser-plasma coupling for a single, controlled filament of light and to underline the importance of the coupling among the numerous speckles within conventional multispeckled beams
International Nuclear Information System (INIS)
Rebuffi, L.
1987-10-01
The development and optimization of a microwave technique, concerning the high frequency (electronic cyclotron frequency) plasma heating is presented. The experiments are effectuated on the Fontenay-aux-Roses TFR tokamak, with 660 kw whole power, during 100 msec, produced at 60 GHz. Low power tests are performed on the different transmission line components (there are 3, formed by metallic circular waveguides). The work also includes: the development of a lens formed by thin metallic plans; the study of slotted surface mirror; the development of a system for the accurate measurement (5.10 -6 ) of the gyrotronic frequency; a theory, based on the equivalent circuits method, generalized to the rotational and polarization mirrors; the development of a numerical simulation code. A practical scheme, for the optimization of the parameters concerning the optical transmission line project, is given. The results of this work can be applied to the experiment involving power levels, frequencies and times of impulsion increasingly higher (respectively about MW, 100 GHz and 10s) than the reported ones. Moreover, they can also be used in any experiment in the microwave field [fr
Reconstruction and simplification of urban scene models based on oblique images
Liu, J.; Guo, B.
2014-08-01
We describe a multi-view stereo reconstruction and simplification algorithms for urban scene models based on oblique images. The complexity, diversity, and density within the urban scene, it increases the difficulty to build the city models using the oblique images. But there are a lot of flat surfaces existing in the urban scene. One of our key contributions is that a dense matching algorithm based on Self-Adaptive Patch in view of the urban scene is proposed. The basic idea of matching propagating based on Self-Adaptive Patch is to build patches centred by seed points which are already matched. The extent and shape of the patches can adapt to the objects of urban scene automatically: when the surface is flat, the extent of the patch would become bigger; while the surface is very rough, the extent of the patch would become smaller. The other contribution is that the mesh generated by Graph Cuts is 2-manifold surface satisfied the half edge data structure. It is solved by clustering and re-marking tetrahedrons in s-t graph. The purpose of getting 2- manifold surface is to simply the mesh by edge collapse algorithm which can preserve and stand out the features of buildings.
TID measurement using oblique transmissions of HF pulses
Galkin, Ivan; Reinisch, Bodo; Huang, Xueqin; Paznukhov, Vadym; Hamel, Ryan; Kozlov, Alexander; Belehaki, Anna
2017-04-01
The Traveling Ionospheric Disturbance (TID), a wave-like signature of moving plasma density modulation in the ionosphere, is widely acknowledged for its utility in backtracking the anomalous events responsible for the TID generation, and as a major inconvenience to high-frequency (HF) operational systems because of its deleterious impact on the accuracy of navigation and geolocation. The pilot project "Net-TIDE" for the real-time detection and evaluation of TIDs began its operation in 2016 based on the remote-sensing data from synchronized, network-coordinated HF sounding between pairs of DPS4D ionosondes at five participating observatories in Europe. Measurement of all signal properties (Doppler frequency, angle of arrival, and time-of-flight from transmitter to receiver) proved to be instrumental in detecting the TID and deducing the TID parameters: amplitude, wavelength, phase velocity, and direction of propagation. Processing of the measured HF signal data required a specialized signal processing technique that is capable of consistently extracting different signals that have propagated along different ionospheric paths. The multi-path signal environment proved to be the greatest challenge for the reliable TID specification by Net-TIDE, demanding the development of an intelligent system for "signal tracking". The intelligent system is based on a neural network model of a pre-attentive vision capable of extracting continuous signal tracks from the multi-path signal ensemble. Specific examples of the Net-TIDE algorithm suite operation and its suitability for a fully automated TID warning service are discussed.
Propagation of SLF/ELF electromagnetic waves
Pan, Weiyan
2014-01-01
This book deals with the SLF/ELF wave propagation, an important branch of electromagnetic theory. The SLF/ELF wave propagation theory is well applied in earthquake electromagnetic radiation, submarine communication, thunderstorm detection, and geophysical prospecting and diagnostics. The propagation of SLF/ELF electromagnetic waves is introduced in various media like the earth-ionospheric waveguide, ionospheric plasma, sea water, earth, and the boundary between two different media or the stratified media. Applications in the earthquake electromagnetic radiation and the submarine communications are also addressed. This book is intended for scientists and engineers in the fields of radio propagation and EM theory and applications. Prof. Pan is a professor at China Research Institute of Radiowave Propagation in Qingdao (China). Dr. Li is a professor at Zhejiang University in Hangzhou (China).
[Fluctuations and transport in fusion plasma]: Progress report, October 1, 1989--September 30, 1990
International Nuclear Information System (INIS)
1995-01-01
In the study of plasma collection by obstacles in a tokamak edge plasma, the effect of anomalous transport have been examined using an extension of the 2D fluid code developed here previously (Appendices A and B). The origin of the anomalous transport is assumed to be a randomly fluctuating electric field such as would be caused by drift waves. As before, the magnetic field is assumed to be uniform and perpendicular to the obstacle, which is taken to be an infinite strip. In the absence of ambient plasma flow, the numerical results indicate that ion viscous heating is important near the tip of the obstacle, where there is a large velocity gradient in the flow. For typical plasma parameters, the maximum ion temperature near the tip is up to 85% higher than the ambient ion temperature. When there is a subsonic plasma flow past the obstacle, the numerical results indicate that, near the tip of the obstacle, the ions on the downstream side are hotter than those on the upstream side. Furthermore, the ion density is higher on the upstream side. A detailed report of this work has been prepared and will be submitted as part of the Annual Progress Report. Recently, the 2D parallel electrostatic plasma particle-in-cell (PIC) code described in reference (9) (Appendix B) has been upgraded to a 2D fully electromagnetic PIC code. This code has been successfully tested on the JPL/Caltech Mark III Hypercube concurrent computers and can be used to simulate interactions of electromagnetic waves with a magnetized plasma. It is currently applied to investigate the decay of large amplitude Alfven waves, such as those observed in the solar wind. Large amplitude Alfven waves, propagating parallel to the magnetic field, are predicted to decay into obliquely propagating daughter waves and standing magnetosonic waves. Results from the simulations will be compared with theoretical predictions
Energy Technology Data Exchange (ETDEWEB)
Ofman, Leon, E-mail: Leon.Ofman@nasa.gov [Department of Physics, The Catholic University of America, Washington, DC (United States); NASA Goddard Space Flight Center, Greenbelt, MD (United States); Visiting, Department of Geosciences, Tel Aviv University, Tel Aviv (Israel); Ozak, Nataly [Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)
2016-03-25
Near the Sun (< 10R{sub s}) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super-Alfvénic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.
Inferior oblique muscle paresis as a sign of myasthenia gravis.
Almog, Yehoshua; Ben-David, Merav; Nemet, Arie Y
2016-03-01
Myasthenia gravis may affect any of the six extra-ocular muscles, masquerading as any type of ocular motor pathology. The frequency of involvement of each muscle is not well established in the medical literature. This study was designed to determine whether a specific muscle or combination of muscles tends to be predominantly affected. This retrospective review included 30 patients with a clinical diagnosis of myasthenia gravis who had extra-ocular muscle involvement with diplopia at presentation. The diagnosis was confirmed by at least one of the following tests: Tensilon test, acetylcholine receptor antibodies, thymoma on chest CT scan, or suggestive electromyography. Frequency of involvement of each muscle in this cohort was inferior oblique 19 (63.3%), lateral rectus nine (30%), superior rectus four (13.3%), inferior rectus six (20%), medial rectus four (13.3%), and superior oblique three (10%). The inferior oblique was involved more often than any other muscle (pmyasthenia gravis can be difficult, because the disease may mimic every pupil-sparing pattern of ocular misalignment. In addition diplopia caused by paresis of the inferior oblique muscle is rarely encountered (other than as a part of oculomotor nerve palsy). Hence, when a patient presents with vertical diplopia resulting from an isolated inferior oblique palsy, myasthenic etiology should be highly suspected. Copyright © 2015 Elsevier Ltd. All rights reserved.
A Quick and Affine Invariance Matching Method for Oblique Images
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XIAO Xiongwu
2015-04-01
Full Text Available This paper proposed a quick, affine invariance matching method for oblique images. It calculated the initial affine matrix by making full use of the two estimated camera axis orientation parameters of an oblique image, then recovered the oblique image to a rectified image by doing the inverse affine transform, and left over by the SIFT method. We used the nearest neighbor distance ratio(NNDR, normalized cross correlation(NCC measure constraints and consistency check to get the coarse matches, then used RANSAC method to calculate the fundamental matrix and the homography matrix. And we got the matches that they were interior points when calculating the homography matrix, then calculated the average value of the matches' principal direction differences. During the matching process, we got the initial matching features by the nearest neighbor(NN matching strategy, then used the epipolar constrains, homography constrains, NCC measure constrains and consistency check of the initial matches' principal direction differences with the calculated average value of the interior matches' principal direction differences to eliminate false matches. Experiments conducted on three pairs of typical oblique images demonstrate that our method takes about the same time as SIFT to match a pair of oblique images with a plenty of corresponding points distributed evenly and an extremely low mismatching rate.
Magnetic droplet soliton nucleation in oblique fields
Mohseni, Morteza; Hamdi, M.; Yazdi, H. F.; Banuazizi, S. A. H.; Chung, S.; Sani, S. R.; Åkerman, Johan; Mohseni, Majid
2018-05-01
We study the auto-oscillating magnetodynamics in orthogonal spin-torque nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic-field angle. In perpendicular fields and at OOP field angles down to approximately 50°, we observe the nucleation of a droplet. However, for field angles below 50°, experiments indicate that the droplet gives way to propagating spin waves, in agreement with our micromagnetic simulations. Theoretical calculations show that the physical mechanism behind these observations is the sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show that the presence of a strong perpendicular magnetic anisotropy free layer in the system reverses the angular dependence of the SWN and dynamics in STNOs with respect to the known behavior determined for the in-plane magnetic anisotropy free layer. Our results are of fundamental interest in understanding the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.
International Nuclear Information System (INIS)
Andreev, Pavel A.
2015-01-01
We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction
Zwaan, Frank; Schreurs, Guido; Adam, Jürgen
2017-04-01
During the early stages of rifting, rift segments may form along non-continuous and/or offset pre-existing weaknesses. It is important to understand how these initial rift segments interact and connect to form a continuous rift system. Previous modelling of rift interaction structures has shown the dominant influence of oblique extension, promoting rift segment linkage (e.g. Zwaan et al., 2016) and eventual continent break-up (Brune et al., 2012). However, these studies did not incorporate sedimentation, which can have important implications for rift evolution (e.g. Bialas and Buck, 2009). Here we present a series of analogue model experiments investigating the influence of sedimentation on rift interaction structures under oblique extension conditions. Our set-up involves a base of compressed foam and plexiglass that forces distributed extension in the overlying analogue materials when the model sidewalls move apart. A sand layer simulates the brittle upper crust and a viscous sand/silicone mixture the ductile lower crust. One of the underlying base plates can move laterally allowing oblique extension. Right-stepping offset and disconnected lines of silicone (seeds) on top of the basal viscous serve as inherited structures since the strong sand cover is locally thinner. We apply syn-rift sediments by filling in the developing rift and transfer zone basins with sand at fixed time steps. Models are run either with sedimentation or without to allow comparison. The first results suggest that the gross structures are similar with or without sedimentation. As seen by Zwaan et al. (2016), dextral oblique extension promotes rift linkage because rift propagation aligns itself perpendicular to the extension direction. This causes the rift segments to grow towards each other and to establish a continuous rift structure. However, the structures within the rift segments show quite different behaviour when sedimentation is applied. The extra sediment loading in the rift basin
Wang, Zhuo; Dunkerton, Timothy J.; Montgomery, Michael T.
2012-01-01
A wave-tracking algorithm is developed for northwestward-propagating waves that, on occasion, play a role in tropical cyclogenesis over the western oceans. To obtain the Lagrangian flow structure, the frame of reference is translated obliquely at the same propagation speed with the precursor disturbance. Trajectory analysis suggests that streamlines in the obliquely translated frame of reference can be used to approximate flow trajectories. The algorithm was applied to Super Typhoon Nakri (2008), Tropical Cyclone Erika (2009), and a few other examples. Diagnoses of meteorological analyses and satellite-derived moisture and precipitation fields show that the marsupial framework for tropical cyclogenesis in tropical easterly waves is relevant also for northwestward-propagating disturbances as are commonly observed in the tropical western Atlantic, the Gulf of Mexico, and the western North Pacific. Finally, it is suggested that analysis of the global model data and satellite observations in the marsupial framework can provide useful guidance on early tropical cyclone advisories.
'Non-local' response of RTP ohmic plasmas to peripheral perturbations
International Nuclear Information System (INIS)
Galli, P.; Gorini, G.; Mantica, P.; Hogeweij, G.M.D.; Kloe, J. de; Lopes Cardozo, N.J.
1999-01-01
A 'non-local' response of the plasma core triggered by peripheral plasma perturbations other than laser ablation is found in the RTP tokamak. Oblique pellet injection (OPI) has been used to induce fast cooling of the peripheral plasma. In response, an inward cold pulse (T e drop) and a slightly delayed core T e rise are observed. A somewhat similar 'non-local' response is observed when the peripheral plasma is heated by modulated electron cyclotron heating or by fast current ramps, i.e. the core temperature drops in response to the peripheral heating. The plasma conditions for the occurrence of the 'non-local' response have been investigated. The core T e rise following OPI is associated with the formation of a large temperature gradient in the region 1 e rise is largest at low electron density and for large pellet deposition radii. Above a critical density the T e rise disappears and only the (weaker) drop in core T e is observed. Time dependent transport simulations show that the propagation of the inward cold pulse is consistent with local transport, while the core T e rise is a slower phenomenon requiring a large transient drop of χ e in the region 1 < q < 2. (author)
Research On The Measure Method Of Oblique Pinhole Parameters
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Ma Yu-Zhen
2016-01-01
Full Text Available There are many special advantages in measuring the diameter of blind and deep holes with a capacitive probe, there are still some challenges for the measurement of a oblique pinhole parameters because the measuring device is inconvenient to stretch into the oblique pinhole exactly. A five-dimensional measurement system was adopted in the paper which included a capacitive sensor probe and a three-coordinate measuring machine to accomplish the measurement for oblique pinholes. With the help of the three-dimensional coordinates measured from the pinhole axis, we put forward a comprehensive method of combining the projection method and the least squares method together for fitting spatial straight line to obtain the optimal equation of the spacial axis. Finally, a reliable and entire measurement system was set up.
HOT STARS WITH HOT JUPITERS HAVE HIGH OBLIQUITIES
International Nuclear Information System (INIS)
Winn, Joshua N.; Albrecht, Simon; Fabrycky, Daniel; Johnson, John Asher
2010-01-01
We show that stars with transiting planets for which the stellar obliquity is large are preferentially hot (T eff > 6250 K). This could explain why small obliquities were observed in the earliest measurements, which focused on relatively cool stars drawn from Doppler surveys, as opposed to hotter stars that emerged more recently from transit surveys. The observed trend could be due to differences in planet formation and migration around stars of varying mass. Alternatively, we speculate that hot-Jupiter systems begin with a wide range of obliquities, but the photospheres of cool stars realign with the orbits due to tidal dissipation in their convective zones, while hot stars cannot realign because of their thinner convective zones. This in turn would suggest that hot Jupiters originate from few-body gravitational dynamics and that disk migration plays at most a supporting role.
Recent progress of obliquely deposited thin films for industrial applications
Suzuki, Motofumi; Itoh, Tadayoshi; Taga, Yasunori
1999-06-01
More than 10 years ago, birefringent films of metal oxides were formed by oblique vapor deposition and investigated with a view of their application to optical retardation plates. The retardation function of the films was explained in terms of the birefringence caused by the characteristic anisotropic nanostructure inside the films. These films are now classified in the genre of the so-called sculptured thin films. However, the birefringent films thus prepared are not yet industrialized even now due to the crucial lack of the durability and the yield of products. In this review paper, we describe the present status of application process of the retardation films to the information systems such as compact disc and digital versatile disc devices with a special emphasis on the uniformity of retardation properties in a large area and the stability of the optical properties of the obliquely deposited thin films. Finally, further challenges for wide application of the obliquely deposited thin films are also discussed.
Study of obliquely deposited thin cobalt films
International Nuclear Information System (INIS)
Szmaja, W.; Kozlowski, W.; Balcerski, J.; Kowalczyk, P.J.; Grobelny, J.; Cichomski, M.
2010-01-01
Research highlights: → The paper reports simultaneously on the magnetic domain structure of obliquely deposited thin cobalt films (40 nm and 100 nm thick) and their morphological structure. Such studies are in fact rare (Refs. cited in the paper). → Moreover, to our knowledge, observations of the morphological structure of these films have not yet been carried out simultaneously by transmission electron microscopy (TEM) and atomic force microscopy (AFM). → The films of both thicknesses were found to have uniaxial in-plane magnetic anisotropy. → The magnetic microstructure of the films 40 nm thick was composed of domains running and magnetized predominantly in the direction perpendicular to the incidence plane of the vapor beam. → As the film thickness was changed from 40 nm to 100 nm, the magnetic anisotropy was observed to change from the direction perpendicular to parallel with respect to the incidence plane. → Thanks to the application of TEM and AFM, complementary information on the morphological structure of the films could be obtained. → In comparison with TEM images, AFM images revealed grains larger in size and slightly elongated in the direction perpendicular rather than parallel to the incidence plane. → These experimental findings clearly show that surface diffusion plays an important role in the process of film growth. → For the films 40 nm thick, the alignment of columnar grains in the direction perpendicular to the incidence plane was observed. → This correlates well with the magnetic domain structure of these films. → For the films 100 nm thick, the perpendicular alignment of columnar grains could also be found, although in fact with larger difficulty. → TEM studies showed that the films consisted mainly of the hexagonal close-packed (HCP) crystalline structure, but no preferred crystallographic orientation of the grains could be detected for the films of both thicknesses. → For the films 100 nm thick, the alignment of
Pelvic digital subtraction catheter angiography-Are routine oblique projections necessary?
International Nuclear Information System (INIS)
Rane, Neil; Imam, Atique; Foley, Peter; Timmons, Grace; Uberoi, Raman
2011-01-01
The oblique projection is used widely in imaging of the lower vascular tree. Much of the evidence justifying the oblique projection is anecdotal. This study compares the sensitivity of the anteroposterior (AP) projection alone in lower limb vascular catheter angiography to that combined with the oblique projection. 110 digitally subtracted angiograms were analysed initially on AP and subsequently on oblique views. Oblique imaging increases confidence, demonstrates stenoses not seen on AP and changes the diagnosis. This supports the use of the oblique projection in lower limb vascular interventional imaging.
International Nuclear Information System (INIS)
Levin, B.N.
1984-01-01
The propagation of an inhomogeneous stream of fast electrons through the corona - the type III radio burst source - is considered. It is shown, that the angular spectrum width of plasma waves excited by the stream is defined both by Landau damping by particles of the diffuse component and by damping (in the region of large phase velocities) by particles of the stream itself having large pitch angles. The regime of quasi-one-dimensional diffusion in the velocity space is realized only in the presence of a sufficiently dense diffuse component of super-thermal particles and only for a sufficiently large inhomogeneity scale of the stream. A large scale of the stream space profile is formed, evidently, close to the region of injection of super-thermal particles. It is the result of 'stripping' of part of the electrons from the stream front to its slower part due to essential non-one-dimensionality of the particle diffusion in velocity space. Results obtained may explain, in particular, the evolution of a stream particle angular spectrum in the generation region of type III radio bursts observed by spacecrafts (Lin et al., 1981). For the relatively low energetic part of the stream, the oblique plasma wave stabilization by a diffuse component results in a quasi-one-dimensional regime of diffusion. The latter conserves the beam-like structure of this part of the stream. (orig.)
Oblique lumbar spine radiographs: importance in young patients
Energy Technology Data Exchange (ETDEWEB)
Libson, E.; Bloom, R.A.; Dinari, G.; Robin, G.C.
1984-04-01
Spondylolysis is a direct precursor of spondylolisthesis and can lead to crippling back pain. Of 1,743 patients surveyed, including 936 who were asymptomatic and 807 with back pain, 165 (including 91 who were asymptomatic and 74 with back pain) had spondylolysis, which was seen only on oblique lumbar views in 20% of cases. Because of the high false-negative rate of AP and lateral views, oblique views are essential in children and young adults. As spondylolysis is rare above L3, radiographs can be limited to L3-S1. Significantly less spondylolysis was seen in persons older than 30 with back pain usually caused by disk degeneration.
Oblique lumbar spine radiographs: importance in young patients
International Nuclear Information System (INIS)
Libson, E.; Bloom, R.A.; Dinari, G.; Robin, G.C.
1984-01-01
Spondylolysis is a direct precursor of spondylolisthesis and can lead to crippling back pain. Of 1,743 patients surveyed, including 936 who were asymptomatic and 807 with back pain, 165 (including 91 who were asymptomatic and 74 with back pain) had spondylolysis, which was seen only on oblique lumbar views in 20% of cases. Because of the high false-negative rate of AP and lateral views, oblique views are essential in children and young adults. As spondylolysis is rare above L3, radiographs can be limited to L3-S1. Significantly less spondylolysis was seen in persons older than 30 with back pain usually caused by disk degeneration
ACCURACY OF MEASUREMENTS IN OBLIQUE AERIAL IMAGES FOR URBAN ENVIRONMENT
Directory of Open Access Journals (Sweden)
W. Ostrowski
2016-10-01
Full Text Available Oblique aerial images have been a source of data for urban areas for several years. However, the accuracy of measurements in oblique images during this time has been limited to a single meter due to the use of direct -georeferencing technology and the underlying digital elevation model. Therefore, oblique images have been used mostly for visualization purposes. This situation changed in recent years as new methods, which allowed for a higher accuracy of exterior orientation, were developed. Current developments include the process of determining exterior orientation and the previous but still crucial process of tie point extraction. Progress in this area was shown in the ISPRS/EUROSDR Benchmark on Multi-Platform Photogrammetry and is also noticeable in the growing interest in the use of this kind of imagery. The higher level of accuracy in the orientation of oblique aerial images that has become possible in the last few years should result in a higher level of accuracy in the measurements of these types of images. The main goal of this research was to set and empirically verify the accuracy of measurements in oblique aerial images. The research focused on photogrammetric measurements composed of many images, which use a high overlap within an oblique dataset and different view angles. During the experiments, two series of images of urban areas were used. Both were captured using five DigiCam cameras in a Maltese cross configuration. The tilt angles of the oblique cameras were 45 degrees, and the position of the cameras during flight used a high grade GPS/INS navigation system. The orientation of the images was set using the Pix4D Mapper Pro software with both measurements of the in-flight camera position and the ground control points (measured with GPS RTK technology. To control the accuracy, check points were used (which were also measured with GPS RTK technology. As reference data for the whole study, an area of the city-based map was used
Plasma-based accelerator structures
International Nuclear Information System (INIS)
Schroeder, Carl B.
1999-01-01
Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas
Agapitov, Oleksiy; Drake, James; Mozer, Forrest
2016-04-01
Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.
Generation and propagation of synchro - Cherenkov radiation
International Nuclear Information System (INIS)
Heintzmann, H.; Novello, M.; Schruefer, E.
1981-01-01
Particles moving along the magnetic field lines emit under favorable conditions Cherenkov radiation in a cold, rarefied plasma. A peculiar phenomenon occurs for curved magnetic fields: in for example a toroidal magnetic field the radiation spirals inward and approaches a resonance. Both the generation and the study of the propagation of these Cherenkov modes appear to be within reach of present technology. (Author) [pt
The effect of lower-hybrid waves on the propagation of hydromagnetic waves
International Nuclear Information System (INIS)
Hamabata, Hiromitsu; Namikawa, Tomikazu; Mori, Kazuhiro
1988-01-01
Propagation characteristics of hydromagnetic waves in a magnetic plasma are investigated using the two-plasma fluid equations including the effect of lower-hybrid waves propagating perpendicularly to the magnetic field. The effect of lower-hybrid waves on the propagation of hydromagnetic waves is analysed in terms of phase speed, growth rate, refractive index, polarization and the amplitude relation between the density perturbation and the magnetic-field perturbation for the cases when hydromagnetic waves propagate in the plane whose normal is perpendicular to both the magnetic field and the propagation direction of lower-hybrid waves and in the plane perpendicular to the propagation direction of lower-hybrid waves. It is shown that hydromagnetic waves propagating at small angles to the propagation direction of lower-hybrid waves can be excited by the effect of lower-hybrid waves and the energy of excited waves propagates nearly parallel to the propagation direction of lower-hybrid waves. (author)
Heat pulse propagation studies in TFTR
Energy Technology Data Exchange (ETDEWEB)
Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.; Efthimion, P.C.; Hill, K.W.; Izzo, R.; Mikkelsen, D.R.; Monticello, D.A.; McGuire, K.; Bell, J.D.
1986-02-01
The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab.
Heat pulse propagation studies in TFTR
International Nuclear Information System (INIS)
Fredrickson, E.D.; Callen, J.D.; Colchin, R.J.
1986-02-01
The time scales for sawtooth repetition and heat pulse propagation are much longer (10's of msec) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time scale coupled with more detailed diagnostics has led us to revisit the analysis of the heat pulse propagation as a method to determine the electron heat diffusivity, chi/sub e/, in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation are used to clarify previous work and develop new methods for determining chi/sub e/. Direct comparison of the predicted heat pulses with soft x-ray and ECE data indicates that the space-time evolution is diffusive. However, the chi/sub e/ determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from 2 to 10. Some hypotheses for resolving this discrepancy are discussed. 11 refs., 19 figs., 1 tab
International Nuclear Information System (INIS)
Cook, J W S; Chapman, S C; Dendy, R O; Brady, C S
2011-01-01
We present particle-in-cell (PIC) simulations of minority energetic protons in deuterium plasmas, which demonstrate a collective instability responsible for emission near the lower hybrid frequency and its harmonics. The simulations capture the lower hybrid drift instability in a parameter regime motivated by tokamak fusion plasma conditions, and show further that the excited electromagnetic fields collectively and collisionlessly couple free energy from the protons to directed electron motion. This results in an asymmetric tail antiparallel to the magnetic field. We focus on obliquely propagating modes excited by energetic ions, whose ring-beam distribution is motivated by population inversions related to ion cyclotron emission, in a background plasma with a temperature similar to that of the core of a large tokamak plasma. A fully self-consistent electromagnetic relativistic PIC code representing all vector field quantities and particle velocities in three dimensions as functions of a single spatial dimension is used to model this situation, by evolving the initial antiparallel travelling ring-beam distribution of 3 MeV protons in a background 10 keV Maxwellian deuterium plasma with realistic ion-electron mass ratio. These simulations provide a proof-of-principle for a key plasma physics process that may be exploited in future alpha channelling scenarios for magnetically confined burning plasmas.
Nonlinear optical beam manipulation, beam combining, and atmospheric propagation
International Nuclear Information System (INIS)
Fischer, R.A.
1988-01-01
These proceedings collect papers on optics: Topics include: diffraction properties of laser speckle, coherent beam combination by plasma modes, nonlinear responses, deformable mirrors, imaging radiometers, electron beam propagation in inhomogeneous media, and stability of laser beams in a structured environment
Stereotactic biopsy of cerebellar lesions: straight versus oblique frame positioning.
Quick-Weller, Johanna; Brawanski, Nina; Dinc, Nazife; Behmanesh, Bedjahn; Kammerer, Sara; Dubinski, Daniel; Seifert, Volker; Marquardt, Gerhard; Weise, Lutz
2017-10-26
Biospies of brain lesions with unknown entity are an everyday procedure among many neurosurgical departments. Biopsies can be performed frame-guided or frameless. However, cerebellar lesions are a special entity with a more complex approach. All biopsies in this study were performed stereotactically frame guided. Therefore, only biopsies of cerebellar lesions were included in this study. We compared whether the frame was attached straight versus oblique and we focused on diagnostic yield and complication rate. We evaluated 20 patients who underwent the procedure between 2009 and 2017. Median age was 56.5 years. 12 (60%) Patients showed a left sided lesion, 6 (30%) showed a lesion in the right cerebellum and 2 (10%) patients showed a midline lesion. The stereotactic frame was mounted oblique in 12 (60%) patients and straight in 8 (40%) patients. Postoperative CT scan showed small, clinically silent blood collection in two (10%) of the patients, one (5%) patient showed haemorrhage, which caused a hydrocephalus. He received an external ventricular drain. In both patients with small haemorrhage the frame was positioned straight, while in the patient who showed a larger haemorrhage the frame was mounted oblique. In all patients a final histopathological diagnosis was established. Cerebellar lesions of unknown entity can be accessed transcerebellar either with the stereotactic frame mounted straight or oblique. Also for cerebellar lesions the procedure shows a high diagnostic yield with a low rate of severe complications, which need further treatment.
Analysis of Torque Measurements on Films with Oblique Anistropy
Abelmann, Leon; Kambersky, Vladimir; Lodder, J.C.; Popma, T.J.A.
1993-01-01
A measurement method is discussed to determine the magnetic anisotropy energy in a sample without assuming an a priori model for the origins of the anisotropy. The measurement procedure involves torque measurements in five different planes. Since it is especially useful for films with an oblique
Oblique water entry of a three dimensional body
Directory of Open Access Journals (Sweden)
Scolan Yves-Marie
2014-12-01
Full Text Available The problem of the oblique water entry of a three dimensional body is considered. Wagner theory is the theoretical framework. Applications are discussed for an elliptic paraboloid entering an initially flat free surface. A dedicated experimental campaign yields a data base for comparisons. In the present analysis, pressure, force and dynamics of the wetted surface expansion are assessed.
Residual symptoms after surgery for unilateral congenital superior oblique palsy.
Caca, Ihsan; Sahin, Alparslan; Cingu, Abdullah; Ari, Seyhmus; Akbas, Umut
2012-01-01
To establish the surgical results and residual symptoms in 48 cases with unilateral congenital superior oblique muscle palsy that had surgical intervention to the vertical muscles alone. Myectomy and concomitant disinsertion of the inferior oblique (IO) muscle was performed in 38 cases and myectomy and concomitant IO disinsertion and recession of the superior rectus muscle in the ipsilateral eye was performed in 10 cases. The preoperative and postoperative vertical deviation values and surgical results were compared. Of the patients who had myectomy and concomitant IO disinsertion, 74% achieved an "excellent" result, 21% a "good" result, and 5% a "poor" result postoperatively. The difference in deviation between preoperative and postoperative values was statistically significant (P < .001). Of the patients who had myectomy and concomitant inferior oblique disinsertion and ipsilateral superior rectus recession, 50% achieved an "excellent" result, 20% a "good" result, and 30% a "poor" result postoperatively. The difference in deviation between preoperative and postoperative values was statistically significant (P < .001). Both procedures are effective and successful in patients with superior oblique muscle palsy, but a secondary surgery may be required. Copyright 2012, SLACK Incorporated.
International Nuclear Information System (INIS)
Ohno, Noriyasu; Furuta, Katsuhiro; Takamura, Shuichi
2004-01-01
We investigated the intermittent convective plasma transport in a attached and/or detached plasma condition of the linear divertor plasma simulator, NAGDIS-II. Images taken by a fast-imaging camera clearly show that in attached plasmas, blobs are peeled off the bulk plasma, and propagate outward with an azimuthal motion. In detached plasmas, plasma turbulence observed near the plasma recombining region drives strong intermittent radial plasma transport, which could broaden the radial density profile. (author)
Studies on waves and instabilities in a plasma sheath formed on the outer surface of a space craft
International Nuclear Information System (INIS)
Aria, Anil K.; Malik, Hitendra K.
2008-01-01
Using the normal mode analysis, the number of possible modes is obtained in a magnetized inhomogeneous plasma sheath formed during the motion of a space craft which consists of negative ions (due to dust) along with the positive ions and the isothermal electrons. In addition to three propagating modes with phase velocities λ 1 , λ 2 , and λ 3 such that λ 1 2 3 , two types of instabilities with growth rates γ 1 and γ 2 also occur in such a plasma sheath. The growth rate γ 1 is increased with the negative to positive ion density ratio r 0 , ion temperature T, and obliqueness θ of the magnetic field B 0 . The growth rate γ 2 of the other instability gets lower with the density ratio r 0 but gets higher with the temperature T. The growth rate γ 2 is sensitive to the temperature T, whereas the growth rate γ 1 gets prominently changed with the density ratio r 0 . The increase in the growth rate γ 1 with the obliqueness θ is more pronounced under the effect of stronger magnetic field. On other hand, the phase velocity λ 1 shows weak dependence on r 0 and T (though it gets larger) but it gets significantly changed (increased) for the larger obliqueness θ. The phase velocity λ 2 gets larger with r 0 , B 0 , and θ and becomes lower for the higher temperature T. The phase velocity λ 3 is decreased for the higher values of r 0 and B 0 and is increased for the larger values of T and θ
Nonlinear propagation of the extraordinary mode in a hot magnetoplasma
International Nuclear Information System (INIS)
Khiet, Tu; Furutani, Y.; Ichikawa, Y.H.
1978-07-01
Kinetic theory for a nonlinear propagation of quasi-monochromatic extraordinary waves is presented. It reveals that propagation of an envelope of the extraordinary carriers is described by the nonlinear Schroedinger equation. In a cold plasma limit, a detailed analysis is carried out on a behaviour of the envelope of the upper- and the lower-hybrid waves at respective resonant frequency ranges. (author)
Analyzing RCD30 Oblique Performance in a Production Environment
Soler, M. E.; Kornus, W.; Magariños, A.; Pla, M.
2016-06-01
In 2014 the Institut Cartogràfic i Geològic de Catalunya (ICGC) decided to incorporate digital oblique imagery in its portfolio in response to the growing demand for this product. The reason can be attributed to its useful applications in a wide variety of fields and, most recently, to an increasing interest in 3d modeling. The selection phase for a digital oblique camera led to the purchase of the Leica RCD30 Oblique system, an 80MPixel multispectral medium-format camera which consists of one Nadir camera and four oblique viewing cameras acquiring images at an off-Nadir angle of 35º. The system also has a multi-directional motion compensation on-board system to deliver the highest image quality. The emergence of airborne oblique cameras has run in parallel to the inclusion of computer vision algorithms into the traditional photogrammetric workflows. Such algorithms rely on having multiple views of the same area of interest and take advantage of the image redundancy for automatic feature extraction. The multiview capability is highly fostered by the use of oblique systems which capture simultaneously different points of view for each camera shot. Different companies and NMAs have started pilot projects to assess the capabilities of the 3D mesh that can be obtained using correlation techniques. Beyond a software prototyping phase, and taking into account the currently immature state of several components of the oblique imagery workflow, the ICGC has focused on deploying a real production environment with special interest on matching the performance and quality of the existing production lines based on classical Nadir images. This paper introduces different test scenarios and layouts to analyze the impact of different variables on the geometric and radiometric performance. Different variables such as flight altitude, side and forward overlap and ground control point measurements and location have been considered for the evaluation of aerial triangulation and
ANALYZING RCD30 OBLIQUE PERFORMANCE IN A PRODUCTION ENVIRONMENT
Directory of Open Access Journals (Sweden)
M. E. Soler
2016-06-01
Full Text Available In 2014 the Institut Cartogràfic i Geològic de Catalunya (ICGC decided to incorporate digital oblique imagery in its portfolio in response to the growing demand for this product. The reason can be attributed to its useful applications in a wide variety of fields and, most recently, to an increasing interest in 3d modeling. The selection phase for a digital oblique camera led to the purchase of the Leica RCD30 Oblique system, an 80MPixel multispectral medium-format camera which consists of one Nadir camera and four oblique viewing cameras acquiring images at an off-Nadir angle of 35º. The system also has a multi-directional motion compensation on-board system to deliver the highest image quality. The emergence of airborne oblique cameras has run in parallel to the inclusion of computer vision algorithms into the traditional photogrammetric workflows. Such algorithms rely on having multiple views of the same area of interest and take advantage of the image redundancy for automatic feature extraction. The multiview capability is highly fostered by the use of oblique systems which capture simultaneously different points of view for each camera shot. Different companies and NMAs have started pilot projects to assess the capabilities of the 3D mesh that can be obtained using correlation techniques. Beyond a software prototyping phase, and taking into account the currently immature state of several components of the oblique imagery workflow, the ICGC has focused on deploying a real production environment with special interest on matching the performance and quality of the existing production lines based on classical Nadir images. This paper introduces different test scenarios and layouts to analyze the impact of different variables on the geometric and radiometric performance. Different variables such as flight altitude, side and forward overlap and ground control point measurements and location have been considered for the evaluation of aerial
Numerical studies of electron dynamics in oblique quasi-perpendicular collisionless shock waves
International Nuclear Information System (INIS)
Liewer, P.C.; Decyk, V.K.; Dawson, J.M.; Lembege, B.
1991-01-01
Linear and nonlinear electron damping of the whistler precursor wave train to low Mach number quasi-perpendicular oblique shocks is studied using a one-dimensional electromagnetic plasma simulation code with particle electrons and ions. In some parameter regimes, electrons are observed to trap along the magnetic field lines in the potential of the whistler precursor wave train. This trapping can lead to significant electron heating in front of the shock for β e (∼10% or less). Use of the 64-processor Caltech/JPL Mark IIIfp hypercube concurrent computer has enables us to make long runs using realistic mass ratios (m i /m e = 1,600) in the full particle in-cell code and thus simulate shock parameter regimes and phenomena not previously studied numerically
Radial propagation of microturbulence in tokamaks
International Nuclear Information System (INIS)
Garbet, X.; Laurent, L.; Roubin, J.P.; Samain, A.
1992-01-01
Energy confinement time in tokamaks exhibits a clear dependence on global plasma parameters. This is not the case for transport coefficients; their dependence on local plasma parameters cannot be precisely established. The aim of the present paper is to give a possible explanation of this behaviour; turbulence propagates radially because of departure from cylindrical geometry. This implies that the turbulence level at a given point and hence transport coefficients are not only functions of local plasma parameters. A quantitative estimate of the propagation velocity is derived from a Lagrangian formalism. Two cases are considered: the effect of toroidicity and the effect of non linear mode-mode coupling. The consequences of this model are discussed. This process does not depend on the type of instability. For the sake of simplicity only electrostatic perturbations are considered
Validity of PEC Approximation for On-Body Propagation
DEFF Research Database (Denmark)
Kammersgaard, Nikolaj Peter Iversen; Kvist, Søren Helstrup; Thaysen, Jesper
2016-01-01
Many articles on on-body propagation assumes that the human body can be approximated by a perfect electric conductor (PEC) instead of the actual constitutive parameters of the human body, which is that of a lossy dielectric. This assumption is investigated in this article through comparison...... of the scattering of a plane wave at oblique incidence by a PEC and a lossy dielectric cylinder. The investigation shows that the validity of the assumption depends on the polarization of the plane wave, the angle of incidence, and the region of interest....
Investigation of EBW Thermal Emission and Mode Conversion Physics in H-Mode Plasmas on NSTX
International Nuclear Information System (INIS)
Diem, S.J.; Taylor, G.; Efthimion, P.C.; Kugel, H.W.; LeBlanc, B.P.; Phillips, C.K.; Caughman, J.B.; Wilgen, J.B.; Harvey, R.W.; Preinhaelter, J.; Urban, J.; Sabbagh, S.A.
2008-01-01
High β plasmas in the National Spherical Torus Experiment (NSTX) operate in the overdense regime, allowing the electron Bernstein wave (EBW) to propagate and be strongly absorbed/emitted at the electron cyclotron resonances. As such, EBWs may provide local electron heating and current drive. For these applications, efficient coupling between the EBWs and electromagnetic waves outside the plasma is needed. Thermal EBW emission (EBE) measurements, via oblique B-X-O double mode conversion, have been used to determine the EBW transmission efficiency for a wide range of plasma conditions on NSTX. Initial EBE measurements in H-mode plasmas exhibited strong emission before the L-H transition, but the emission rapidly decayed after the transition. EBE simulations show that collisional damping of the EBW prior to the mode conversion (MC) layer can significantly reduce the measured EBE for T e < 20 eV, explaining the observations. Lithium evaporation was used to reduce EBE collisional damping near the MC layer. As a result, the measured B-X-O transmission efficiency increased from < 10% (no Li) to 60% (with Li), consistent with EBE simulations.
Simulation of Plasma Jet Merger and Liner Formation within the PLX- α Project
Samulyak, Roman; Chen, Hsin-Chiang; Shih, Wen; Hsu, Scott
2015-11-01
Detailed numerical studies of the propagation and merger of high Mach number argon plasma jets and the formation of plasma liners have been performed using the newly developed method of Lagrangian particles (LP). The LP method significantly improves accuracy and mathematical rigor of common particle-based numerical methods such as smooth particle hydrodynamics while preserving their main advantages compared to grid-based methods. A brief overview of the LP method will be presented. The Lagrangian particle code implements main relevant physics models such as an equation of state for argon undergoing atomic physics transformation, radiation losses in thin optical limit, and heat conduction. Simulations of the merger of two plasma jets are compared with experimental data from past PLX experiments. Simulations quantify the effect of oblique shock waves, ionization, and radiation processes on the jet merger process. Results of preliminary simulations of future PLX- alpha experiments involving the ~ π / 2 -solid-angle plasma-liner configuration with 9 guns will also be presented. Partially supported by ARPA-E's ALPHA program.
Radio stimulation and diagnostics of space plasmas. Progress report
International Nuclear Information System (INIS)
Lee, Minchang.
1993-02-01
This report describes the investigation of the small-scale topside ionospheric plasma structures first observed at Millstone Hill, Massachusetts with the 440 MHz incoherent scatter radar. These small-scale obliquely propagating plasma modes occurring in the vicinity of the midlatitude ionospheric trough, have large radar cross-sections and narrow spectral widths. They have, until recently, been dismissed solely as hard target contamination of the incoherent scatter radar. The geophysical conditions associated with the ionospheric trough, such as the field-aligned current activity and steep plasma density gradients, suggest that these recently discovered small-scale topside ionospheric plasmas may also appear in the auroral and polar ionosphere. In fact, this speculation has been corroborated by the preliminary experiments and data analyses at Tromso, Norway and Sondrestromfjord, Greenland. The primary research results are highlighted. Described in Section 3 are the experiments conducted at Arecibo, Puerto Rico in the past summer for simulating the geophysical conditions of generating these topside ionospheric plasma structures. Recommendation for the future research is finally given. Attached as the appendix of this report are several chapters which present the detailed results of research in the concerned topside ionospheric clutter. Highlights of the research results include: (1) causes of the enhanced radar backscatter (ERB) phenomenon; (2) occurrence of the ERB phenomenon; (3) altitudes of the ERB phenomenon; (4) strength of the ERB returns; (5) range of altitudes of the ERB returns; (6) occurrence frequency of the ERB phenomenon; (7) Doppler effect of the ERB phenomenon; (8) persistency of the ERB; and (9) distinction between ERB phenomenon and space object signatures
Propagation of an ionizing surface electromagnetic wave
Energy Technology Data Exchange (ETDEWEB)
Boev, A.G.; Prokopov, A.V.
1976-11-01
The propagation of an rf surface wave in a plasma which is ionized by the wave itself is analyzed. The exact solution of the nonlinear Maxwell equations is discussed for the case in which the density of plasma electrons is an exponential function of the square of the electric field. The range over which the surface wave exists and the frequency dependence of the phase velocity are found. A detailed analysis is given for the case of a plasma whose initial density exceeds the critical density at the wave frequency. An increase in the wave amplitude is shown to expand the frequency range over which the plasma is transparent; The energy flux in the plasma tends toward a certain finite value which is governed by the effective ionization field.