Collisional transport in nonneutral plasmas

International Nuclear Information System (INIS)

Dubin, D.H.E.

1999-01-01

Classical transport theory grossly underestimates collisionally-driven cross-field transport for plasmas in the parameter regime of r c D , where r c ≡ v-bar/Ω c , λ D 2 ≡ T/4πe 2 n. In current experiments operating in this regime, cross-field test particle transport is observed to be a factor of 10 larger than the prediction of classical theory. Heat conduction is enhanced by up to 300 times over classical theory, and viscosity is up to 10 4 times larger. New guiding center theories of transport due to long-range collisions have been developed that agree with the measurements. Theory also predicts that emission and absorption of plasma waves may further enhance the thermal conduction and viscosity, providing a possible mechanism for anomalous thermal conductivity in the electron channel of fusion plasmas. (author)

Final Scientific/Technical Report: Correlations and Fluctuations in Weakly Collisional Plasma

Energy Technology Data Exchange (ETDEWEB)

Skiff, Frederick [Univ. of Iowa, Iowa City, IA (United States)

2017-11-15

large part of the complexity of plasma motion. Reduced descriptions were found to fail under most circumstances. A new technique was developed that enabled a measurement of the phase-space resolved ion correlation function for the first time. The wide range of plasma dynamics possible became clear through this technique. It was found that collisionless (Vlasov) theory has a large field of application even when the plasma is weakly-collisional. A new approach, the kinetic wave expansion, was proposed, tested and found to be very useful for describing electrostatic ion waves. This project demonstrated a new way of looking at the "degrees-of-freedom" of plasmas and provided significant validation tests of fluid and kinetic plasma descriptions.

Collisional-radiative model: a plasma spectroscopy theory for experimentalists

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Takashi [Kyoto Univ. (Japan); Sawada, Keiji

1997-01-01

The rate equation describing the population n(p) of an excited (and the ground state) level p of ions immersed in plasma is shown. In 1962, the method of quasi-steady state solution (collisional-radiative model) was proposed. Its idea is explained. The coupled differential equations reduce to a set of coupled linear equations for excited levels. The solution of these coupled equations is presented. The equations giving the ionization and recombination of this system of ions under consideration are described in terms of the effective rate coefficients. The collisional-radiative ionization and recombination rate coefficients are expressed in terms of the population coefficients for p > 1. As for ionizing plasma, the excited level populations, the populations, the population distribution among the excited levels, two regimes of the excited levels, the dominant flows of electrons among the levels and so on are shown. As for recombining plasma, the excited level populations, the population distribution among the excited levels, the dominant flows of electrons and so on are shown. Ionization balance plasma may be considered. (K.I.)

Generalized fluid equations for parallel transport in collisional to weakly collisional plasmas

International Nuclear Information System (INIS)

Zawaideh, E.; Najmabadi, F.; Conn, R.W.

1986-01-01

A new set of two-fluid equations that are valid from collisional to weakly collisional limits is derived. Starting from gyrokinetic equations in flux coordinates with no zero-order drifts, a set of moment equations describing plasma transport along the field lines of a space- and time-dependent magnetic field is derived. No restriction on the anisotropy of the ion distribution function is imposed. In the highly collisional limit, these equations reduce to those of Braginskii, while in the weakly collisional limit they are similar to the double adiabatic or Chew, Goldberger, and Low (CGL) equations [Proc. R. Soc. London, Ser. A 236, 112 (1956)]. The new set of equations also exhibits a physical singularity at the sound speed. This singularity is used to derive and compute the sound speed. Numerical examples comparing these equations with conventional transport equations show that in the limit where the ratio of the mean free path lambda to the scale length of the magnetic field gradient L/sub B/ approaches zero, there is no significant difference between the solution of the new and conventional transport equations. However, conventional fluid equations, ordinarily expected to be correct to the order (lambda/L/sub B/) 2 , are found to have errors of order (lambda/L/sub u/) 2 = (lambda/L/sub B/) 2 /(1-M 2 ) 2 , where L/sub u/ is the scale length of the flow velocity gradient and M is the Mach number. As such, the conventional equations may contain large errors near the sound speed (Mroughly-equal1)

Electromagnetic-wave absorption by inhomogeneous, collisional plasmas

International Nuclear Information System (INIS)

Gregoire, D.J.; Santoru, J.; Schumacher, R.W.

1990-01-01

Unmagnetized, collisional plasmas can be used as broadband EM-wave absorbers or refractors. In the absorption process, plasma electrons are first accelerated by the EM-wave fields and then collide with background-gas molecules, thereby transferring energy from the EM waves to the gas. A plasma absorber has several advantages compared to conventional materials. A plasma can be turned on and off very rapidly, thereby switching between absorbing and transparent conditions. Calculations indicate that plasma absorbers can also be tailored to provide broadband absorption (>40 dB) over multiple octaves. The authors have developed a one-dimensional model and a computer code to calculate the net power reflected from a plasma-enclosed EM-wave-reflecting target. They included three contributions to the reflected EM-wave power: reflections from the vacuum-plasma interface; reflections from the bulk plasma volume; and reflection of the attenuated EM wave that is transmitted through the plasma and reflected by the target

Kinetic equations for the collisional plasma model

International Nuclear Information System (INIS)

Rij, W.I. Van; Meier, H.K.; Beasley, C.O. Jr.; McCune, J.E.

1977-01-01

Using the Collisional Plasma Model (CPM) representation, expressions are derived for the Vlasov operator, both in its general form and in the drift-kinetic approximation following the recursive derivation by Hazeltine. The expressions for the operators give easily calculated couplings between neighbouring components of the CPM representation. Expressions for various macroscopic observables in the drift-kinetics approximation are also given. (author)

Reduction of collisional-radiative models for transient, atomic plasmas

Science.gov (United States)

Abrantes, Richard June; Karagozian, Ann; Bilyeu, David; Le, Hai

2017-10-01

Interactions between plasmas and any radiation field, whether by lasers or plasma emissions, introduce many computational challenges. One of these computational challenges involves resolving the atomic physics, which can influence other physical phenomena in the radiated system. In this work, a collisional-radiative (CR) model with reduction capabilities is developed to capture the atomic physics at a reduced computational cost. Although the model is made with any element in mind, the model is currently supplemented by LANL's argon database, which includes the relevant collisional and radiative processes for all of the ionic stages. Using the detailed data set as the true solution, reduction mechanisms in the form of Boltzmann grouping, uniform grouping, and quasi-steady-state (QSS), are implemented to compare against the true solution. Effects on the transient plasma stemming from the grouping methods are compared. Distribution A: Approved for public release; unlimited distribution, PA (Public Affairs) Clearance Number 17449. This work was supported by the Air Force Office of Scientific Research (AFOSR), Grant Number 17RQCOR463 (Dr. Jason Marshall).

Diagnostics of helium plasma by collisional-radiative modeling and optical emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Lee, Wonwook; Kwon, Duck-Hee [KAERI, Daejeon (Korea, Republic of)

2015-05-15

Optical diagnostics for the electron temperature (T{sub e}) and the electron density (n{sub e}) of fusion plasma is important for understanding and controlling the edge and the divertor plasmas in tokamak. Since the line intensity ratio method using the collisional-radiative modeling and OES (optical emission spectroscopy) is simple and does not disturb the plasma, many fusion devices with TEXTOR, JET, JT-60U, LHD, and so on, have employed the line intensity ratio method as a basic diagnostic tool for neutral helium (He I). The accuracy of the line intensity ratio method depends on the reliability of the cross sections and rate coefficients. We performed state-of-the-art R-matrix calculations including couplings up to n=7 states and the distorted wave (DW) calculations for the electron-impact excitation (EIE) cross sections of He I using the flexible atomic code (FAC). The collisional-radiative model for He I was constructed using the calculated the cross sections. The helium collisional-radiative model for He I was constructed to diagnose the electron temperature and the electron density of the plasma. The electron temperature and density were determined by using the line intensity ratio method.

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades In Magentized Weakly Collisional Plasmas

Energy Technology Data Exchange (ETDEWEB)

Schekochihin, A. A.; Cowley, S. C.; Dorland, W.; Hammett, G. W.; Howes, G. G.; Quataert, E.; Tatsuno, T.

2009-04-23

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulentmotions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-fieldstrength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades In Magnetized Weakly Collisional Plasmas

International Nuclear Information System (INIS)

Schekochihin, A.A.; Cowley, S.C.; Dorland, W.; Hammett, G.W.; Howes, G.G.; Quataert, E.; Tatsuno, T.

2009-01-01

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulent motions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the 'inertial range' above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-field strength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations

Drift wave dispersion relation for arbitrarily collisional plasma

International Nuclear Information System (INIS)

Angus, Justin R.; Krasheninnikov, Sergei I.

2012-01-01

The standard local linear analysis of drift waves in a plasma slab is generalized to be valid for arbitrarily collisional electrons by considering the electrons to be governed by the drift-kinetic equation with a BGK-like (Bhatnagar-Gross-Krook) collision operator. The obtained dispersion relation reduces to that found from collisionless kinetic theory when the collision frequency is zero. Electron temperature fluctuations must be retained in the standard fluid analysis in order to obtain good quantitative agreement with our general solution in the highly collisional limit. Any discrepancies between the fluid solution and our general solution in this limit are attributed to the limitations of the BGK collision operator. The maximum growth rates in both the collisional and collisionless limits are comparable and are both on the order of the fundamental drift wave frequency. The main role of the destabilizing mechanism is found to be in determining the parallel wave number at which the maximum growth rate will occur. The parallel wave number corresponding to the maximum growth rate is set by the wave-particle resonance condition in the collisionless limit and transitions to being set by the real frequency being on the order of the rate for electrons to diffuse a parallel wavelength in the collisional limit.

Drift wave dispersion relation for arbitrarily collisional plasma

Energy Technology Data Exchange (ETDEWEB)

Angus, Justin R.; Krasheninnikov, Sergei I. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093-0417 (United States)

2012-05-15

The standard local linear analysis of drift waves in a plasma slab is generalized to be valid for arbitrarily collisional electrons by considering the electrons to be governed by the drift-kinetic equation with a BGK-like (Bhatnagar-Gross-Krook) collision operator. The obtained dispersion relation reduces to that found from collisionless kinetic theory when the collision frequency is zero. Electron temperature fluctuations must be retained in the standard fluid analysis in order to obtain good quantitative agreement with our general solution in the highly collisional limit. Any discrepancies between the fluid solution and our general solution in this limit are attributed to the limitations of the BGK collision operator. The maximum growth rates in both the collisional and collisionless limits are comparable and are both on the order of the fundamental drift wave frequency. The main role of the destabilizing mechanism is found to be in determining the parallel wave number at which the maximum growth rate will occur. The parallel wave number corresponding to the maximum growth rate is set by the wave-particle resonance condition in the collisionless limit and transitions to being set by the real frequency being on the order of the rate for electrons to diffuse a parallel wavelength in the collisional limit.

Investigation of collisional excitation-transfer processes in a plasma by laser perturbation method

International Nuclear Information System (INIS)

Sakurai, Takeki

1983-01-01

The theoretical background and the experimental method of the laser perturbation method applied to the study of collisional excitation transfer process in plasma are explained. The atomic density at some specified level can be evaluated theoretically. By using the theoretical results and the experimentally obtained data, the total attenuation probability, the collisional transfer probability and natural emission probability were estimated. For the experiments, continuous wave laser (cw) and pulse laser are employed. It is possible by using pulse dye laser to observe the attenuation curve directly, and to bring in resonance to any atomic spectra. At the beginning, the experimental studies were made on He-Ne discharge. The pulse dye laser has been used for the excitation of alkali atoms. The first application of pulse laser to the study of plasma physics was the study on He. The cross section of disalignment has also been studied by the laser perturbation. The alignment of atoms, step and cascade transfer, the confinement of radiation and optogalvanic effect are discussed in this paper. (Kato, T.)

Spatial mode structures of electrostatic drift waves in a collisional cylindrical helicon plasma

DEFF Research Database (Denmark)

Schröder, C.; Grulke, O.; Klinger, T.

2004-01-01

In a cylindrical helicon plasma, mode structures of coherent drift waves are studied in the poloidal plane, the plane perpendicular to the ambient magnetic field. The mode structures rotate with a constant angular velocity in the direction of the electron diamagnetic drift and show significant...... radial bending. The experimental observations are compared with numerical solutions of a linear nonlocal cylindrical model for drift waves [ Ellis , Plasma Phys. 22, 113 (1980) ]. In the numerical model, a transition to bended mode structures is found if the plasma collisionality is increased....... This finding proves that the experimentally observed bended mode structures are the result of high electron collisionality. (C) 2004 American Institute of Physics....

Modulational instability of electric helicons in a magnetized collisional plasma

International Nuclear Information System (INIS)

El-Ashry, M.Y.; Papuashvili, N.A.

1987-06-01

The interaction of a rf electromagnetic wave with a magnetized collisional plasma in the ultra-relativistic case has been investigated to show the effect of the collisions on the modulational instability growth rate. (author). 5 refs

A one-dimensional collisional model for plasma-immersion ion implantation

International Nuclear Information System (INIS)

Vahedi, V.; Lieberman, M.A.; Alves, M.V.; Verboncoeur, J.P.; Birdsall, C.K.

1991-01-01

Plasma-immersion ion implantation (also known as plasma-source ion implantation) is a process in which a target is immersed in a plasma and a series of large negative-voltage pulses are applied to it to extract ions from the plasma and implant them into the target. A general one-dimensional model is developed to study this process in different coordinate systems for the case in which the pressure of the neutral gas is large enough that the ion motion in the sheath can be assumed to be highly collisional

Nonlinear transport processes in tokamak plasmas. I. The collisional regimes

International Nuclear Information System (INIS)

Sonnino, Giorgio; Peeters, Philippe

2008-01-01

An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear ('Onsager') transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for Joint European Torus (JET) plasmas are also reported. It is found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor that may be of the order 10 2 . The nonlinear classical coefficients exceed the neoclassical ones by a factor that may be of order 2. For JET, the discrepancy between experimental and theoretical results for the electron losses is therefore significantly reduced by a factor 10 2 when the nonlinear contributions are duly taken into account but, there is still a factor of 10 2 to be explained. This is most likely due to turbulence. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes, i.e., the plateau and the banana regimes, are analyzed in the second part of this work

Continuous Emission Spectrum Measurement for Electron Temperature Determination in Low-Temperature Collisional Plasmas

International Nuclear Information System (INIS)

Liu Qiuyan; Li Hong; Chen Zhipeng; Xie Jinlin; Liu Wandong

2011-01-01

Continuous emission spectrum measurement is applied for the inconvenient diagnostics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron temperature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method. (low temperature plasma)

Dusty Plasma Modeling of the Fusion Reactor Sheath Including Collisional-Radiative Effects

International Nuclear Information System (INIS)

Dezairi, Aouatif; Samir, Mhamed; Eddahby, Mohamed; Saifaoui, Dennoun; Katsonis, Konstantinos; Berenguer, Chloe

2008-01-01

The structure and the behavior of the sheath in Tokamak collisional plasmas has been studied. The sheath is modeled taking into account the presence of the dust 2 and the effects of the charged particle collisions and radiative processes. The latter may allow for optical diagnostics of the plasma.

Charging properties of a dust grain in collisional plasmas

International Nuclear Information System (INIS)

Khrapak, S.A.; Morfill, G.E.; Khrapak, A.G.; D'yachkov, L.G.

2006-01-01

Charging related properties of a small spherical grain immersed in a collisional plasma are investigated. Asymptotic expressions for charging fluxes, grain surface potential, long range electrostatic potential, and the properties of grain charge fluctuations due to the discrete nature of the charging process are obtained. These analytical results are in reasonable agreement with the available results of numerical modeling

Resonant absorption of radar waves by a magnetized collisional plasma

International Nuclear Information System (INIS)

Sun Aiping; Tong Honghui; Shen Liru; Tang Deli; Qiu Xiaoming

2001-01-01

The propagation of radar waves in a magnetized collisional plasma slab is studied numerically. It is found for uniform plasma that: first, the wave attenuation and absorbed power show a peak value, i.e., resonant absorption when the collision frequency f en = 0.1, 0.5, 1 GHz and the wave frequency nears upper hybrid frequency. Secondly, the attenuation, absorbed, and transmitted power curves become flat at f en = 5, 10 Ghz. thirdly, the attenuation and absorbed power increase with plasma density, and the attenuation and the proportion of absorbed power can reach 100 dB and 80%, respectively, at the plasma density n = 10 11 cm -3 . For nonuniform plasma, the peak value of reflected power is larger than that in uniform plasma. So, uniform magnetized plasma is of more benefit to plasma cloaking

Current sustaining by RF travelling field in a collisional toroidal plasma

International Nuclear Information System (INIS)

Fukuda, Masaji; Matsuura, Kiyokata

1978-01-01

The relation between the current generated by RF travelling field and the absorbed power is studied in a collisional toroidal plasma, parameters being phase velocity and filling gap pressure or electron collision frequency. It is observed at a low magnetic field that the current is proportional to the plasma conductivity and an effective electromotive force, which is a new concept introduced on the basis of fluid model; the electromotive force is proportional to the absorbed RF power and inversely proportional to the plasma density and the phase velocity of the travelling field. (author)

Current sustaining by RF travelling field in a collisional toroidal plasma

International Nuclear Information System (INIS)

Fukuda, Masaji; Matsuura, Kiyokata.

1977-06-01

The relation between the current generation by RF travelling field and the accompanied power absorption is studied in a collisional toroidal plasma, parameters being phase velocity and filling gas pressure or electron collision frequency. It is observed at a low magnetic field that the current is proportional to the plasma conductivity and an effective electromotive force, which is a new concept introduced on the basis of fluid model; the electromotive force is proportional to the absorbed RF power and inversely proportional to the plasma density and the phase velocity of the travelling field. (auth.)

Generation of Suprathermal Electrons by Collective Processes in Collisional Plasma

Science.gov (United States)

Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

2017-11-01

The ubiquity of high-energy tails in the charged particle velocity distribution functions (VDFs) observed in space plasmas suggests the existence of an underlying process responsible for taking a fraction of the charged particle population out of thermal equilibrium and redistributing it to suprathermal velocity and energy ranges. The present Letter focuses on a new and fundamental physical explanation for the origin of suprathermal electron velocity distribution function (EVDF) in a collisional plasma. This process involves a newly discovered electrostatic bremsstrahlung (EB) emission that is effective in a plasma in which binary collisions are present. The steady-state EVDF dictated by such a process corresponds to a Maxwellian core plus a quasi-inverse power-law tail, which is a feature commonly observed in many space plasma environments. In order to demonstrate this, the system of self-consistent particle- and wave-kinetic equations are numerically solved with an initially Maxwellian EVDF and Langmuir wave spectral intensity, which is a state that does not reflect the presence of EB process, and hence not in force balance. The EB term subsequently drives the system to a new force-balanced steady state. After a long integration period it is demonstrated that the initial Langmuir fluctuation spectrum is modified, which in turn distorts the initial Maxwellian EVDF into a VDF that resembles the said core-suprathermal VDF. Such a mechanism may thus be operative at the coronal source region, which is characterized by high collisionality.

Nonlinear acoustic waves in partially ionized collisional plasmas

International Nuclear Information System (INIS)

Rao, N.N.; Kaup, D.J.; Shukla, P.K.

1991-01-01

Nonlinear propagation of acoustic-type waves in a partially ionized three-component collisional plasma consisting of electrons, ions and neutral particles is investigated. For bidirectional propagation, it is shown that the small- but finite-amplitude waves are governed by the Boussinesq equation, which for unidirectional propagation near the acoustic speed reduces to the usual Korteweg-de Vries equation. For large-amplitude waves, it is demonstrated that the relevant fluid equations are integrable in a stationary frame, and the parameter values for the existence of finite-amplitude solutions are explicitly obtained. In both cases, the different temperatures of the individual species, are taken into account. The relevance of the results to the earth's ionospheric plasma in the lower altitude ranges is pointed out. (author)

Nonlinear magnetic reconnection in low collisionality plasmas

Energy Technology Data Exchange (ETDEWEB)

Ottaviani, M [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Porcelli, F [Politecnico di Torino, Turin (Italy)

1994-07-01

The magnetic reconnection in collisionless regimes, where electron inertia is responsible for the decoupling of the plasma motion from that of the field lines, is discussed. Since the linear theory of m=1 modes breaks down for very small magnetic island widths, a non linear analysis is called for. Thus, the behaviour of a collisionless, 2-D fluid slab model in the limit {rho}/d -> 0, is analyzed. The main result is that, when the island size is larger than the linear layer but smaller than the equilibrium scale length, the reconnection rate exhibits a quasi-explosive time behaviour, during which a current density sub-layer narrower than the skin depth is formed. It is believed that the inclusion of the electron initial term in Ohm`s law opens the possibility to understand the rapidity of relaxation process observed in low collisionality plasmas. 7 refs., 6 figs.

Generation of poloidal magnetic field in a hot collisional plasma by inverse Faraday effect

International Nuclear Information System (INIS)

Srivastava, M.K.; Lawande, S.V.; Dutta, D.; Sarkar, S.; Khan, M.; Chakraborty, B.

1996-01-01

Generation of poloidal magnetic field in a hot and collisional plasma by an inverse Faraday effect is discussed. This field can either be induced by a circularly polarized laser beam (CPLB) or a plane-polarized laser beam (PPLB). For the CPLB, an average field left-angle Re x right-angle ∼I 0 λ∼11.6 MG could be produced in a DT plasma for a high intensity (I 0 =10 22 W/m 2 ) and shorter wavelength (λ=0.35 μm) laser. This field is essentially induced by the field inhomogeneity effect and dominates over that induced by the plasma inhomogeneity effect (left-angle Re x right-angle ∼I 2/3 0 λ 7/3 ∼2.42 MG). The collisional and thermal contribution to left-angle Re x right-angle is just negligible for the CPLB. However, in the case of PPLB the poloidal field is generated only for a hot and collisional plasma and can be quite large for a longer wavelength laser (e.g., CO 2 laser, λ=10.6 μm). The collisional effect induces a field left-angle Re x right-angle ∼0.08 kG, which dominates near the turning point and is independent of the laser parameters. However, in the outer cronal region the thermal pressure effect dominates (e.g., left-angle Re x right-angle ∼I 5/3 0 λ 4/3 ∼3.0 MG). Further, left-angle Re x right-angle for the p-polarized beam is, in general, relatively smaller than that for the s-polarized beam. Practical implications of these results and their limitations are discussed. copyright 1996 American Institute of Physics

Highly Resolved Measurements of a Developing Strong Collisional Plasma Shock

Science.gov (United States)

Rinderknecht, Hans G.; Park, H.-S.; Ross, J. S.; Amendt, P. A.; Higginson, D. P.; Wilks, S. C.; Haberberger, D.; Katz, J.; Froula, D. H.; Hoffman, N. M.; Kagan, G.; Keenan, B. D.; Vold, E. L.

2018-03-01

The structure of a strong collisional shock front forming in a plasma is directly probed for the first time in laser-driven gas-jet experiments. Thomson scattering of a 526.5 nm probe beam was used to diagnose temperature and ion velocity distribution in a strong shock (M ˜11 ) propagating through a low-density (ρ ˜0.01 mg /cc ) plasma composed of hydrogen. A forward-streaming population of ions traveling in excess of the shock velocity was observed to heat and slow down on an unmoving, unshocked population of cold protons, until ultimately the populations merge and begin to thermalize. Instabilities are observed during the merging, indicating a uniquely plasma-phase process in shock front formation.

Behavior of collisional sheath in electronegative plasma with q-nonextensive electron distribution

Science.gov (United States)

Borgohain, Dima Rani; Saharia, K.

2018-03-01

Electronegative plasma sheath is addressed in a collisional unmagnetized plasma consisting of q-nonextensive electrons, Boltzmann distributed negative ions and cold fluid positive ions. Considering the positive ion-neutral collisions and ignoring the effects of ionization and collisions between negative species and positive ions (neutrals), a modified Bohm sheath criterion and hence floating potential are derived by using multifluid model. Using the modified Bohm sheath criterion, the sheath characteristics such as spatial profiles of density, potential and net space charge density have been numerically investigated. It is found that increasing values of q-nonextensivity, electronegativity and collisionality lead to a decrease of the sheath thickness and an increase of the sheath potential and the net space charge density. With increasing values of the electron temperature to negative ion temperature ratio, the sheath thickness increases and the sheath potential as well as the net space charge density in the sheath region decreases.

Streaming instabilities in a collisional dusty plasma

International Nuclear Information System (INIS)

Mamun, A. A.; Shukla, P. K.

2000-01-01

A pair of low-frequency electrostatic modes, which are very similar to those experimentally observed by Praburam and Goree [Phys. Plasmas 3, 1212 (1996)], are found to exist in a dusty plasma with a significant background neutral pressure and background ion streaming. One of these two modes is the dust-acoustic mode and the other one is a new mode which is due to the combined effects of the ion streaming and ion--neutral collisions. It has been shown that in the absence of the ion streaming, the dust-acoustic mode is damped due to the combined effects of the ion--neutral and dust--neutral collisions and the electron--ion recombination onto the dust grain surface. This result disagrees with Kaw and Singh [Phys. Rev. Lett. 79, 423 (1997)], who reported collisional instability of the dust-acoustic mode in such a dusty plasma. It has also been found that a streaming instability with the growth rate of the order of the dust plasma frequency is triggered when the background ion streaming speed relative to the charged dust particles is comparable or higher than the ion--thermal speed. This point completely agrees with Rosenberg [J. Vac. Soc. Technol. A 14, 631 (1996)

Experimental studies of collisional plasma shocks and plasma interpenetration via merging supersonic plasma jets

Science.gov (United States)

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.

Tungsten Ions in Plasmas: Statistical Theory of Radiative-Collisional Processes

Directory of Open Access Journals (Sweden)

Alexander V. Demura

2015-05-01

Full Text Available The statistical model for calculations of the collisional-radiative processes in plasmas with tungsten impurity was developed. The electron structure of tungsten multielectron ions is considered in terms of both the Thomas-Fermi model and the Brandt-Lundquist model of collective oscillations of atomic electron density. The excitation or ionization of atomic electrons by plasma electron impacts are represented as photo-processes under the action of flux of equivalent photons introduced by E. Fermi. The total electron impact single ionization cross-sections of ions Wk+ with respective rates have been calculated and compared with the available experimental and modeling data (e.g., CADW. Plasma radiative losses on tungsten impurity were also calculated in a wide range of electron temperatures 1 eV–20 keV. The numerical code TFATOM was developed for calculations of radiative-collisional processes involving tungsten ions. The needed computational resources for TFATOM code are orders of magnitudes less than for the other conventional numerical codes. The transition from corona to Boltzmann limit was investigated in detail. The results of statistical approach have been tested by comparison with the vast experimental and conventional code data for a set of ions Wk+. It is shown that the universal statistical model accuracy for the ionization cross-sections and radiation losses is within the data scattering of significantly more complex quantum numerical codes, using different approximations for the calculation of atomic structure and the electronic cross-sections.

Review and limitations of 3D plasma blob modeling with reduced collisional fluid equations

Energy Technology Data Exchange (ETDEWEB)

Angus, Justin R., E-mail: jangus@ucsd.edu [University of California, San Diego, La Jolla, CA (United States); Umansky, Maxim V. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Krashenninikov, Sergei I. [University of California, San Diego, La Jolla, CA (United States)

2013-07-15

Recent 3D studies on plasma blobs (coherent structures found in the edge region of magnetic confinement devices) have demonstrated that the drift wave instability can strongly limit the blob’s coherency and cross field convective nature that is predicted by 2D theory. However, the dominant unstable drift wave modes that effect plasma blobs were found to exist in parameter regimes that only marginally satisfied several of the major assumptions considered for the validity of the reduced collisional fluid equations used in the study. Namely, the neglect of electron heat flow, finite electron mean free path effects, and thermal ions. A follow up study demonstrated how the drift wave instability might change if a set of equations that does not suffer from the limitations mentioned above were considered. In the present paper, the results of this later work are used to discuss the limitations on using the collisional fluid equations for 3D studies of plasma blobs.

Electromagnetic drift waves dispersion for arbitrarily collisional plasmas

Energy Technology Data Exchange (ETDEWEB)

Lee, Wonjae, E-mail: wol023@ucsd.edu; Krasheninnikov, Sergei I., E-mail: skrash@mae.ucsd.edu [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); Angus, J. R. [Naval Research Laboratory, 4555 Overlook Avenue, Washington, DC 20375 (United States)

2015-07-15

The impacts of the electromagnetic effects on resistive and collisionless drift waves are studied. A local linear analysis on an electromagnetic drift-kinetic equation with Bhatnagar-Gross-Krook-like collision operator demonstrates that the model is valid for describing linear growth rates of drift wave instabilities in a wide range of plasma parameters showing convergence to reference models for limiting cases. The wave-particle interactions drive collisionless drift-Alfvén wave instability in low collisionality and high beta plasma regime. The Landau resonance effects not only excite collisionless drift wave modes but also suppress high frequency electron inertia modes observed from an electromagnetic fluid model in collisionless and low beta regime. Considering ion temperature effects, it is found that the impact of finite Larmor radius effects significantly reduces the growth rate of the drift-Alfvén wave instability with synergistic effects of high beta stabilization and Landau resonance.

A collisional model for plasma immersion ion implantation

International Nuclear Information System (INIS)

Vahedi, V.; Lieberman, M.A.; Alves, M.V.; Verboncoeur, J.P.; Birdsall, C.K.

1990-01-01

In plasma immersion ion implantation, a target is immersed in a plasma and a series of negative short pulses are applied to it to implant the ions. A new analytical model is being developed for the high pressure regimes in which the motion of the ions is highly collisional. The model provides values for ion flux, average ion velocity at the target, and sheath edge motion as a function of time. These values are being compared with those obtained from simulation and show good agreement. A review is also given (for comparison) of the earlier work done at low pressures, where the motion of ions in the sheath is collisionless, also showing good agreement between analysis and simulation. The simulation code is PDP1 which utilizes particle-in-cell techniques plus Monte-Carlo simulation of electron-neutral (elastic, excitation and ionization) and ion-neutral (scattering and charge-exchange) collisions

Influence of the collisional recombination on the electrostatic fluctuation spectrum in an helium plasma

International Nuclear Information System (INIS)

Baravian, G.; Bretagne, J.; Godart, J.; Sultan, G.

1975-01-01

The collisional recombination, in the afterglow of a dense plasma, is regarded as a source process for an overpopulation of the high energy tail of the electron velocity distribution function. The perturbation of the distribution function leads to an important enhancement of the fluctuations of the electrostatic field in a narrow range near the plasma frequency ωsub(p). (orig.) [de

Dielectric constant and laser beam propagation in an underdense collisional plasma: effects of electron temperature

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.

Collisionality dependence of Mercier stability in LHD equilibria with bootstrap currents

International Nuclear Information System (INIS)

Ichiguchi, Katsuji.

1997-02-01

The Mercier stability of the plasmas carrying bootstrap currents with different plasma collisionality is studied in the Large Helical Device (LHD). In the LHD configuration, the direction of the bootstrap current depends on the collisionality of the plasma through the change in the sign of the geometrical factor. When the beta value is raised by increasing the density of the plasma with a fixed low temperature, the plasma becomes more collisional and the collisionality approaches the plateau regime. In this case, the bootstrap current can flow in the direction so as to decrease the rotational transform. Then, the large Shafranov shift enhances the magnetic well and the magnetic shear, and therefore, the Mercier stability is improved. On the other hand, when the beta value is raised by increasing the temperature of the plasma with a fixed low density, the plasma collisionality becomes reduced to enter the 1/ν collisionality regime and the bootstrap current flows so that the rotational transform should be increased, which is unfavorable for the Mercier stability. Hence, the beta value should be raised by increasing the density rather than the temperature in order to obtain a high beta plasma. (author)

Density dependence of line intensities and application to plasma diagnostics

International Nuclear Information System (INIS)

Masai, Kuniaki.

1993-02-01

Electron density dependence of spectral lines are discussed in view of application to density diagnostics of plasmas. The dependence arises from competitive level population processes, radiative and collisional transitions from the excited states. Results of the measurement on tokamak plasmas are presented to demonstrate the usefulness of line intensity ratios for density diagnostics. Also general characteristics related to density dependence are discussed with atomic-number scaling for H-like and He-like systems to be helpful for application to higher density plasmas. (author)

Potential around a dust grain in collisional plasma

Energy Technology Data Exchange (ETDEWEB)

Moulick, R., E-mail: moulick@gmail.com; Goswami, K. S. [Centre of Plasma Physics - Institute for Plasma Research Sonapur, Guwahati, Assam 782402 (India)

2015-04-15

The ion neutral collision can lead to interesting phenomena in dust charging, totally different from the expectations based on the traditional orbit motion limited theory. The potential around a dust grain is investigated for the collisional plasma considering the presence of ion neutral collisions. Fluid equations are solved for the one dimensional radial coordinate. It is observed that with the gradual increase in ion neutral collision, the potential structure around the dust grain changes its shape and is different from the usual Debye-Hückel potential. The shift however starts from a certain value of ion neutral collision and the electron-ion density varies accordingly. The potential variation is interesting and reconfirms the fact that there exists a region of attraction for negative charges. The collision modeling is done for the full range of plasma, i.e., considering the bulk and the sheath jointly. The potential variation with collision is also shown explicitly and the variation is found to cope up with the earlier observations.

Measured improvement of global magnetohydrodynamic mode stability at high-beta, and in reduced collisionality spherical torus plasmas

Energy Technology Data Exchange (ETDEWEB)

Berkery, J. W.; Sabbagh, S. A.; Balbaky, A. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B. P.; Manickam, J.; Menard, J. E.; Podestà, M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Betti, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

2014-05-15

Global mode stability is studied in high-β National Spherical Torus Experiment (NSTX) plasmas to avoid disruptions. Dedicated experiments in NSTX using low frequency active magnetohydrodynamic spectroscopy of applied rotating n = 1 magnetic fields revealed key dependencies of stability on plasma parameters. Observations from previous NSTX resistive wall mode (RWM) active control experiments and the wider NSTX disruption database indicated that the highest β{sub N} plasmas were not the least stable. Significantly, here, stability was measured to increase at β{sub N}∕l{sub i} higher than the point where disruptions were found. This favorable behavior is shown to correlate with kinetic stability rotational resonances, and an experimentally determined range of measured E × B frequency with improved stability is identified. Stable plasmas appear to benefit further from reduced collisionality, in agreement with expectation from kinetic RWM stabilization theory, but low collisionality plasmas are also susceptible to sudden instability when kinetic profiles change.

A collisional-radiative average atom model for hot plasmas

International Nuclear Information System (INIS)

Rozsnyai, B.F.

1996-01-01

A collisional-radiative 'average atom' (AA) model is presented for the calculation of opacities of hot plasmas not in the condition of local thermodynamic equilibrium (LTE). The electron impact and radiative rate constants are calculated using the dipole oscillator strengths of the average atom. A key element of the model is the photon escape probability which at present is calculated for a semi infinite slab. The Fermi statistics renders the rate equation for the AA level occupancies nonlinear, which requires iterations until the steady state. AA level occupancies are found. Detailed electronic configurations are built into the model after the self-consistent non-LTE AA state is found. The model shows a continuous transition from the non-LTE to the LTE state depending on the optical thickness of the plasma. 22 refs., 13 figs., 1 tab

Jet energy loss in quark-gluon plasma. Kinetic theory with a Bhatnagar-Gross-Krook collisional kernel

Energy Technology Data Exchange (ETDEWEB)

Han, Cheng; Hou, De-fu; Li, Jia-rong [Central China Normal University, Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Wuhan, Hubei (China); Jiang, Bing-feng [Hubei University for Nationalities, Center for Theoretical Physics and School of Sciences, Enshi, Hubei (China)

2017-10-15

The dielectric functions ε{sub L}, ε{sub T} of the quark-gluon plasma (QGP) are derived within the framework of the kinetic theory with BGK-type collisional kernel. The collision effect manifested by the collision rate is encoded in the dielectric functions. Based on the derived dielectric functions we study the collisional energy loss suffered by a fast parton traveling through the QGP. The numerical results show that the collision rate increases the energy loss. (orig.)

Parametric instabilities in a magnetized and collisional plasma

Energy Technology Data Exchange (ETDEWEB)

Phalswal, D R; Dube, A [Punjabi Univ., Patiala (India). Dept. of Physics

1980-09-01

The dispersion relation for a magnetized, collisional and hot plasma in the presence of a pump wave is developed for the case where the pump frequency ..omega../sub 0/ is large compared with the cyclotron frequency ..omega..sub(c) and the plasma frequency ..omega..sub(p). Formulae for the growth rate, the damping rate for the free electron plasma wave and the threshold power are derived and discussed numerically under different conditions. It is found that in a hot plasma (for magnetic fields with ..omega..sub(c)/..omega..sub(p) = 1 and 10) the threshold power Psub(T) is less than or greater than that in a cold plamsa for the (Re..omega../sub 2/)sub(+) or (Re..omega../sub 2/)sub(-) modes respectively. In a weak magnetic field (..omega..sub(c)/..omega..sub(p) = 0.1), Psub(T) does not vary with the direction theta of the magnetic field for the (Re..omega../sub 2/) sub(+) mode. However, Psub(T) for the (Re..omega../sub 2/)sub(-) mode is a minimum at theta = 30deg. and 10deg. for ..omega..sub(c)/ ..omega..sub(p) = 1 and 10 respectively, and it becomes very large (10/sup 5/-10/sup 7/ times its value in a cold unmagnetized plasma) for ..omega..sub(c)/..omega..sub(p) = 0.1. The results for the growth are found to be just the reverse of those for the threshold power.

Rovibrationally Resolved Time-Dependent Collisional-Radiative Model of Molecular Hydrogen and Its Application to a Fusion Detached Plasma

Directory of Open Access Journals (Sweden)

Keiji Sawada

2016-12-01

Full Text Available A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below six is developed. The rovibrational X 1 Σ g + population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.

Ground-state populations of atomic hydrogen and hydrogen-like ions in nonthermal plasmas, and collisional-radiative recombination and ionization coefficients

International Nuclear Information System (INIS)

Drawin, H.W.; Emard, F.

1978-01-01

The populations of atomic hydrogen and hydrogen-like ions have been calculated using a collisional-radiative model. The global collisional-radiative excitation coefficients rsub(j)sup((0)) and rsub(j)sup((1)) valid for homogeneous-stationary and/or quasi-homogeneous quasi-stationary plasmas were published recently. The present paper contains in tabulated form the ground state populations and Saha decrements for the homogeneous stationary state, and the collisional-radiative recombination and ionization coefficients. (Auth.)

Nonlinear coherent structures of Alfvén wave in a collisional plasma

International Nuclear Information System (INIS)

Jana, Sayanee; Chakrabarti, Nikhil; Ghosh, Samiran

2016-01-01

The Alfvén wave dynamics is investigated in the framework of two-fluid approach in a compressible collisional magnetized plasma. In the finite amplitude limit, the dynamics of the nonlinear Alfvén wave is found to be governed by a modified Korteweg-de Vries Burgers equation (mKdVB). In this mKdVB equation, the electron inertia is found to act as a source of dispersion, and the electron-ion collision serves as a dissipation. The collisional dissipation is eventually responsible for the Burgers term in mKdVB equation. In the long wavelength limit, this weakly nonlinear Alfvén wave is shown to be governed by a damped nonlinear Schrödinger equation. Furthermore, these nonlinear equations are analyzed by means of analytical calculation and numerical simulation to elucidate the various aspects of the phase-space dynamics of the nonlinear wave. Results reveal that nonlinear Alfvén wave exhibits the dissipation mediated shock, envelope, and breather like structures. Numerical simulations also predict the formation of dissipative Alfvénic rogue wave, giant breathers, and rogue wave holes. These results are discussed in the context of the space plasma.

Nonlinear coherent structures of Alfvén wave in a collisional plasma

Energy Technology Data Exchange (ETDEWEB)

Jana, Sayanee; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

2016-07-15

The Alfvén wave dynamics is investigated in the framework of two-fluid approach in a compressible collisional magnetized plasma. In the finite amplitude limit, the dynamics of the nonlinear Alfvén wave is found to be governed by a modified Korteweg-de Vries Burgers equation (mKdVB). In this mKdVB equation, the electron inertia is found to act as a source of dispersion, and the electron-ion collision serves as a dissipation. The collisional dissipation is eventually responsible for the Burgers term in mKdVB equation. In the long wavelength limit, this weakly nonlinear Alfvén wave is shown to be governed by a damped nonlinear Schrödinger equation. Furthermore, these nonlinear equations are analyzed by means of analytical calculation and numerical simulation to elucidate the various aspects of the phase-space dynamics of the nonlinear wave. Results reveal that nonlinear Alfvén wave exhibits the dissipation mediated shock, envelope, and breather like structures. Numerical simulations also predict the formation of dissipative Alfvénic rogue wave, giant breathers, and rogue wave holes. These results are discussed in the context of the space plasma.

A quiver kinetic formulation of radio frequency heating and confinement in collisional edge plasmas

International Nuclear Information System (INIS)

Catto, P.J.; Myra, J.R.

1989-01-01

The near fields in the collisional edge plasma of a radio frequency heated tokamak can cause one or more charged species to oscillate in the applied field with a quiver (or jitter) speed comparable to its thermal speed. By assuming the quiver motion dominates over drifts and gyromotion a completely new kinetic description of the flows in an edge plasma is formulated which retains Coulomb collisions and the relevant atomic processes. Moment equations are employed to obtain a description in which only a lowest order quiver kinetic equation need be solved to evaluate the slow time particle fluxes and current induced by the applied fields. The electron heating by collisional randomization of their quiver motion (inverse bremsstrahlung) is balanced by impact excitation losses since equilibration with the ions is too weak. A model plasma of electrons, neutrals, and a single cold ion species is considered to illustrate the utility of the quiver kinetic formulation. The model predicts local electrostatic potential changes and a local /rvec E//times//rvec B/ convective flux that is of the same magnitude and scaling as would be predicted by Bohm diffusion. 30 refs

Kinetic particle simulation study of parallel heat transport in scrape-off layer plasmas over a wide range of collisionalities

International Nuclear Information System (INIS)

Froese, Aaron; Takizuka, Tomonori; Yagi, Masatoshi

2010-01-01

Fluid models are not generally applicable to fusion edge plasmas without external provision of kinetic factors: closure parameters and boundary conditions inside the sheath region. We explain the PARASOL-1D simulation, a particle-in-cell code with a binary collision Monte-Carlo model, and use it to determine four kinetic factors commonly needed in fluid codes. These are the electron and ion heat flux limiting factors, α e and α i , the ion adiabatic index, γ A , and the electron and ion temperature anisotropy, T ‖ /T ⊥ . We survey these factors over a wide range of collisionalities and find that, as predicted, the conductive heat flux is accurately described by the Spitzer-Härm expression in the collisional limit and asymptotes to a constant value in the collisionless limit. However, unique behavior occurs in the weakly collisional regime when the ratio of the mean free path to connection length is 0.1 < λ mfp /L ‖ < 10, when the SOL is between the conduction- and sheath-limited regimes. We find that α e can peak, becoming larger than the collisionless limit, γ A is less than unity, and only the ions are anisotropic. The effects of electron energy radiation and Langevin heating are explored. Finally, the strong deviations of the energy distribution function from Maxwellian in the weakly collisional and collisionless regimes are explained. (author)

Effects of Collisionality on the Nonlinear Characteristics of Boundary Turbulence and Blob/hole Transport in Tokamak Plasmas

Energy Technology Data Exchange (ETDEWEB)

Li, J.; Yasuaki, K., E-mail: lijq@energy.kyoto-u.ac.jp [Kyoto University, Kyoto (Japan); Cheng, J.; Longwen, Y.; Jiaqi, D. [Southwestern Institute of Physics, Chengdu (China)

2012-09-15

Full text: Blob/hole dynamics near tokamak separatrix is of striking importance in determining the boundary transport. Based on simulations using an extended 2-region (edge/SOL) fluid model, we found that blob/hole dynamics are sensitively influenced by the plasma collisionality, i.e., ion-electron and ion-neutral collisions. Namely, the holes are enhanced in highly collisional edge whereas the blobs are weakened at the SOL, causing larger particle convection. These blob/hole dynamics are closely correlated with potential dipoles. The trends are experimentally evidenced on the HL-2A tokamak. Moreover, as the neutral-ion collision increases, the blobs at the SOL tend to develop into streamers propagating outwards with reduced amplitude while the holes inwards are suppressed, showing a key role in nonlinear structure regulation and resultant transport suppression. Results suggest that adjusting the plasma collisionality by fueling, e.g., gas puffing, could serve as a method to nonlinearly select turbulent structures, i.e., blobs, holes or streamers, to access the control of boundary transport. (author)

The influence of collisional and anomalous radial diffusion on parallel ion transport in edge plasmas

International Nuclear Information System (INIS)

Helander, P.; Hazeltine, R.D.; Catto, P.J.

1996-01-01

The orderings in the kinetic equations commonly used to study the plasma core of a tokamak do not allow a balance between parallel ion streaming and radial diffusion, and are, therefore, inappropriate in the plasma edge. Different orderings are required in the edge region where radial transport across the steep gradients associated with the scrape-off layer is large enough to balance the rapid parallel flow caused by conditions close to collecting surfaces (such as the Bohm sheath condition). In the present work, we derive and solve novel kinetic equations, allowing for such a balance, and construct distinctive transport laws for impure, collisional, edge plasmas in which the perpendicular transport is (i) due to Coulomb collisions of ions with heavy impurities, or (ii) governed by anomalous diffusion driven by electrostatic turbulence. In both the collisional and anomalous radial transport cases, we find that one single diffusion coefficient determines the radial transport of particles, momentum and heat. The parallel transport laws and parallel thermal force in the scrape-off layer assume an unconventional form, in which the relative ion-impurity flow is driven by a combination of the conventional parallel gradients, and new (i) collisional or (ii) anomalous terms involving products of radial derivatives of the temperature and density with the radial shear of the parallel velocity. Thus, in the presence of anomalous radial diffusion, the parallel ion transport cannot be entirely classical, as usually assumed in numerical edge computations. The underlying physical reason is the appearance of a novel type of parallel thermal force resulting from the combined action of anomalous diffusion and radial temperature and velocity gradients. In highly sheared flows the new terms can modify impurity penetration into the core plasma

Species separation and kinetic effects in collisional plasma shocks

Energy Technology Data Exchange (ETDEWEB)

Bellei, C., E-mail: bellei1@llnl.gov; Wilks, S. C.; Amendt, P. A. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Rinderknecht, H.; Zylstra, A.; Rosenberg, M.; Sio, H.; Li, C. K.; Petrasso, R. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2014-05-15

The properties of collisional shock waves propagating in uniform plasmas are studied with ion-kinetic calculations, in both slab and spherical geometry and for the case of one and two ion species. Despite the presence of an electric field at the shock front—and in contrast to the case where an interface is initially present [C. Bellei et al., Phys. Plasmas 20, 044702 (2013)]—essentially no ion reflection at the shock front is observed due to collisions, with a probability of reflection ≲10{sup −4} for the cases presented. A kinetic two-ion-species spherical convergent shock is studied in detail and compared against an average-species calculation, confirming effects of species separation and differential heating of the ion species at the shock front. The effect of different ion temperatures on the DT and D{sup 3}He fusion reactivity is discussed in the fluid limit and is estimated to be moderately important.

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.

Laser plasma physics in shock ignition – transition from collisional to collisionless absorption

Directory of Open Access Journals (Sweden)

Klimo O.

2013-11-01

Full Text Available Shock Ignition is considered as a relatively robust and efficient approach to inertial confinement fusion. A strong converging shock, which is used to ignite the fuel, is launched by a high power laser pulse with intensity in the range of 1015 − 1016 W/cm2 (at the wavelength of 351 nm. In the lower end of this intensity range the interaction is dominated by collisions while the parametric instabilities are playing a secondary role. This is manifested in a relatively weak reflectivity and efficient electron heating. The interaction is dominated by collective effects at the upper edge of the intensity range. The stimulated Brillouin and Raman scattering (SBS and SRS respectively take place in a less dense plasma and cavitation provides an efficient collisionless absorption mechanism. The transition from collisional to collisionless absorption in laser plasma interactions at higher intensities is studied here with the help of large scale one-dimensional Particle-in-Cell (PIC simulations. The relation between the collisional and collisionless processes is manifested in the energy spectrum of electrons transporting the absorbed laser energy and in the spectrum of the reflected laser light.

Multispecies density peaking in gyrokinetic turbulence simulations of low collisionality Alcator C-Mod plasmas

Energy Technology Data Exchange (ETDEWEB)

Mikkelsen, D. R., E-mail: dmikkelsen@pppl.gov; Bitter, M.; Delgado-Aparicio, L.; Hill, K. W. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Greenwald, M.; Howard, N. T.; Hughes, J. W.; Rice, J. E. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); Reinke, M. L. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Podpaly, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); AAAS S and T Fellow placed in the Directorate for Engineering, NSF, 4201 Wilson Blvd., Arlington, Virginia 22230 (United States); Ma, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Candy, J.; Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2015-06-15

Peaked density profiles in low-collisionality AUG and JET H-mode plasmas are probably caused by a turbulently driven particle pinch, and Alcator C-Mod experiments confirmed that collisionality is a critical parameter. Density peaking in reactors could produce a number of important effects, some beneficial, such as enhanced fusion power and transport of fuel ions from the edge to the core, while others are undesirable, such as lower beta limits, reduced radiation from the plasma edge, and consequently higher divertor heat loads. Fundamental understanding of the pinch will enable planning to optimize these impacts. We show that density peaking is predicted by nonlinear gyrokinetic turbulence simulations based on measured profile data from low collisionality H-mode plasma in Alcator C-Mod. Multiple ion species are included to determine whether hydrogenic density peaking has an isotope dependence or is influenced by typical levels of low-Z impurities, and whether impurity density peaking depends on the species. We find that the deuterium density profile is slightly more peaked than that of hydrogen, and that experimentally relevant levels of boron have no appreciable effect on hydrogenic density peaking. The ratio of density at r/a = 0.44 to that at r/a = 0.74 is 1.2 for the majority D and minority H ions (and for electrons), and increases with impurity Z: 1.1 for helium, 1.15 for boron, 1.3 for neon, 1.4 for argon, and 1.5 for molybdenum. The ion temperature profile is varied to match better the predicted heat flux with the experimental transport analysis, but the resulting factor of two change in heat transport has only a weak effect on the predicted density peaking.

Nonlinear saturation of stimulated Raman scattering in a collisional homogeneous plasma

International Nuclear Information System (INIS)

McKinstrie, C.J.

1985-11-01

Using multiple scale analysis, the nonlinear saturation of the stimulated Raman scattering instability is examined in a collisional homogeneous plasma. The first problem considered is the temporal problem in an infinite plasma, with a ubiquitous driver and arbitrary damping for each wave. The second problem considered is the absolute Raman instability in a finite plasma. The incident wave amplitude exceeds the absolute instability threshold by the fractional amount Δ. In the marginally unstable regime, the complete time dependence and spatial variation of each wave amplitude is obtained. An expression for the reflected light intensity is determined analytically, and is proportional to Δ. The conditions under which the steady-state results can be extended to the moderately unstable regime are discussed. The reflected light intensity is compared to values predicted for the convective instability, for the same incident intensity. In ''short'' plasmas, i.e., ones which extend over only a few linear convective gain lengths, the reflected intensity is found to be much higher when the absolute instability is excited

2D collisional-radiative model for non-uniform argon plasmas: with or without ‘escape factor’

International Nuclear Information System (INIS)

Zhu, Xi-Ming; Tsankov, Tsanko Vaskov; Luggenhölscher, Dirk; Czarnetzki, Uwe

2015-01-01

Collisional-radiative models for excited rare-gas atoms in low-temperature plasmas are a widely investigated topic. When these plasmas are optically thick, an ‘escape factor’ is introduced into the models to account for the reabsorption of photons (so-called radiation trapping process). This factor is usually obtained assuming a uniform density profile of the excited species; however, such an assumption is often not satisfied in a bounded plasma. This article reports for the first time a self-consistent collisional-radiative model without using an ad hoc ‘escape factor’ for excited Ar atoms in the 2p states (in Paschen’s notation). Rather, the rate balance equations—i.e. the radiation transfer equations—of the 2p states are numerically solved to yield the actual density profiles. The predictions of this self-consistent model and a model based on the escape factor concept are compared with spatially-resolved emission measurements in a low-pressure inductive Ar plasma. The self-consistent model agrees well with the experiment but the ‘escape factor’ model shows considerable deviations. By the comparative analysis the limitations and shortcomings of the escape factor concept as adopted in a significant number of works are revealed. (paper)

Updated Collisional Ionization Equilibrium Calculated for Optically Thin Plasmas

Science.gov (United States)

Savin, Daniel Wolf; Bryans, P.; Badnell, N. R.; Gorczyca, T. W.; Laming, J. M.; Mitthumsiri, W.

2010-03-01

Reliably interpreting spectra from electron-ionized cosmic plasmas requires accurate ionization balance calculations for the plasma in question. However, much of the atomic data needed for these calculations have not been generated using modern theoretical methods and their reliability are often highly suspect. We have carried out state-of-the-art calculations of dielectronic recombination (DR) rate coefficients for the hydrogenic through Na-like ions of all elements from He to Zn as well as for Al-like to Ar-like ions of Fe. We have also carried out state-of-the-art radiative recombination (RR) rate coefficient calculations for the bare through Na-like ions of all elements from H to Zn. Using our data and the recommended electron impact ionization data of Dere (2007), we present improved collisional ionization equilibrium calculations (Bryans et al. 2006, 2009). We compare our calculated fractional ionic abundances using these data with those presented by Mazzotta et al. (1998) for all elements from H to Ni. This work is supported in part by the NASA APRA and SHP SR&T programs.

Introduction to plasma physics with space, laboratory and astrophysical applications

CERN Document Server

Gurnett, Donald A

2017-01-01

Introducing basic principles of plasma physics and their applications to space, laboratory and astrophysical plasmas, this new edition provides updated material throughout. Topics covered include single-particle motions, kinetic theory, magnetohydrodynamics, small amplitude waves in hot and cold plasmas, and collisional effects. New additions include the ponderomotive force, tearing instabilities in resistive plasmas and the magnetorotational instability in accretion disks, charged particle acceleration by shocks, and a more in-depth look at nonlinear phenomena. A broad range of applications are explored: planetary magnetospheres and radiation belts, the confinement and stability of plasmas in fusion devices, the propagation of discontinuities and shock waves in the solar wind, and analysis of various types of plasma waves and instabilities that can occur in planetary magnetospheres and laboratory plasma devices. With step-by-step derivations and self-contained introductions to mathematical methods, this book...

First-principle description of collisional gyrokinetic turbulence in tokamak plasmas

Energy Technology Data Exchange (ETDEWEB)

Dif-Pradalier, G

2008-10-15

This dissertation starts in chapter 1 with a comprehensive introduction to nuclear fusion, its basic physics, goals and means. It especially defines the concept of a fusion plasma and some of its essential physical properties. The following chapter 2 discusses some fundamental concepts of statistical physics. It introduces the kinetic and the fluid frameworks, compares them and highlights their respective strengths and limitations. The end of the chapter is dedicated to the fluid theory. It presents two new sets of closure relations for fluid equations which retain important pieces of physics, relevant in the weakly collisional tokamak regimes: collective resonances which lead to Landau damping and entropy production. Nonetheless, since the evolution of the turbulence is intrinsically nonlinear and deeply influenced by velocity space effects, a kinetic collisional description is most relevant. First focusing on the kinetic aspect, chapter 3 introduces the so-called gyrokinetic framework along with the numerical solver - the GYSELA code - which will be used throughout this dissertation. Very generically, code solving is an initial value problem. The impact on turbulent nonlinear evolution of out of equilibrium initial conditions is discussed while studying transient flows, self-organizing dynamics and memory effects due to initial conditions. This dissertation introduces an operational definition, now of routine use in the GYSELA code, for the initial state and concludes on the special importance of the accurate calculation of the radial electric field. The GYSELA framework is further extended in chapter 4 to describe Coulomb collisions. The implementation of a collision operator acting on the full distribution function is presented. Its successful confrontation to collisional theory (neoclassical theory) is also shown. GYSELA is now part of the few gyrokinetic codes which can self-consistently address the interplay between turbulence and collisions. While

First-principle description of collisional gyrokinetic turbulence in tokamak plasmas

International Nuclear Information System (INIS)

Dif-Pradalier, G.

2008-10-01

This dissertation starts in chapter 1 with a comprehensive introduction to nuclear fusion, its basic physics, goals and means. It especially defines the concept of a fusion plasma and some of its essential physical properties. The following chapter 2 discusses some fundamental concepts of statistical physics. It introduces the kinetic and the fluid frameworks, compares them and highlights their respective strengths and limitations. The end of the chapter is dedicated to the fluid theory. It presents two new sets of closure relations for fluid equations which retain important pieces of physics, relevant in the weakly collisional tokamak regimes: collective resonances which lead to Landau damping and entropy production. Nonetheless, since the evolution of the turbulence is intrinsically nonlinear and deeply influenced by velocity space effects, a kinetic collisional description is most relevant. First focusing on the kinetic aspect, chapter 3 introduces the so-called gyrokinetic framework along with the numerical solver - the GYSELA code - which will be used throughout this dissertation. Very generically, code solving is an initial value problem. The impact on turbulent nonlinear evolution of out of equilibrium initial conditions is discussed while studying transient flows, self-organizing dynamics and memory effects due to initial conditions. This dissertation introduces an operational definition, now of routine use in the GYSELA code, for the initial state and concludes on the special importance of the accurate calculation of the radial electric field. The GYSELA framework is further extended in chapter 4 to describe Coulomb collisions. The implementation of a collision operator acting on the full distribution function is presented. Its successful confrontation to collisional theory (neoclassical theory) is also shown. GYSELA is now part of the few gyrokinetic codes which can self-consistently address the interplay between turbulence and collisions. While

Laser-pulse compression in a collisional plasma under weak-relativistic ponderomotive nonlinearity

International Nuclear Information System (INIS)

Singh, Mamta; Gupta, D. N.

2016-01-01

We present theory and numerical analysis which demonstrate laser-pulse compression in a collisional plasma under the weak-relativistic ponderomotive nonlinearity. Plasma equilibrium density is modified due to the ohmic heating of electrons, the collisions, and the weak relativistic-ponderomotive force during the interaction of a laser pulse with plasmas. First, within one-dimensional analysis, the longitudinal self-compression mechanism is discussed. Three-dimensional analysis (spatiotemporal) of laser pulse propagation is also investigated by coupling the self-compression with the self-focusing. In the regime in which the laser becomes self-focused due to the weak relativistic-ponderomotive nonlinearity, we provide results for enhanced pulse compression. The results show that the matched interplay between self-focusing and self-compression can improve significantly the temporal profile of the compressed pulse. Enhanced pulse compression can be achieved by optimizing and selecting the parameters such as collision frequency, ion-temperature, and laser intensity.

Laser-pulse compression in a collisional plasma under weak-relativistic ponderomotive nonlinearity

Energy Technology Data Exchange (ETDEWEB)

Singh, Mamta; Gupta, D. N., E-mail: dngupta@physics.du.ac.in [Department of Physics and Astrophysics, North Campus, University of Delhi, Delhi 110 007 (India)

2016-05-15

We present theory and numerical analysis which demonstrate laser-pulse compression in a collisional plasma under the weak-relativistic ponderomotive nonlinearity. Plasma equilibrium density is modified due to the ohmic heating of electrons, the collisions, and the weak relativistic-ponderomotive force during the interaction of a laser pulse with plasmas. First, within one-dimensional analysis, the longitudinal self-compression mechanism is discussed. Three-dimensional analysis (spatiotemporal) of laser pulse propagation is also investigated by coupling the self-compression with the self-focusing. In the regime in which the laser becomes self-focused due to the weak relativistic-ponderomotive nonlinearity, we provide results for enhanced pulse compression. The results show that the matched interplay between self-focusing and self-compression can improve significantly the temporal profile of the compressed pulse. Enhanced pulse compression can be achieved by optimizing and selecting the parameters such as collision frequency, ion-temperature, and laser intensity.

Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

Directory of Open Access Journals (Sweden)

N. Chakrabarti

2003-05-01

Full Text Available Collisional Rayleigh-Taylor (RT instability is considered in the bottom side of the equatorial F-region. By a novel nonmodal calculation it is shown that for an applied shear flow in equilibrium, the growth of the instability is considerably reduced. Finite but small amounts of diffusion enhances the stabilization process. The results may be relevant to the observations of long-lived irregularities at the bottom-side of the F-layer.Key words. Ionosphere (ionospheric irregularities, equatorial ionosphere, plasma waves and instabilities

Determination of Non-Maxwellian Electron Energy Distributions in Low-Pressure Plasmas by Using the Optical Emission Spectroscopy and a Collisional-Radiative Model

International Nuclear Information System (INIS)

Zhu Ximing; Pu Yikang

2011-01-01

A Maxwellian electron energy distribution function (EEDF) is often assumed when using the optical emission line-ratio method to determine the electron temperature in low-temperature plasmas. However, in many cases, non-Maxwellian EEDFs can be formed due to the non-local electron heating or the inelastic-collisional energy loss processes. In this work, with a collisional-radiative model, we propose an approach to obtain the non-Maxwellian EEDF with a 'two-temperature structure' from the emission line-ratios of Paschen 2p levels of argon and krypton atoms. For applications of this approach in reactive gas (CF 4 , O 2 , etc) discharges that contain argon and krypton, recommendations of some specific emission line-ratios are provided, according to their sensitivities to the EEDF variation. The kinetic processes of the relevant excited atoms are also discussed in detail. (cai awardee's article)

An efficient, selective collisional ejection mechanism for inner-shell population inversion in laser-driven plasmas

Energy Technology Data Exchange (ETDEWEB)

SCHROEDER,W. ANDREAS; NELSON,THOMAS R.; BORISOV,A.B.; LONGWORTH,J.W.; BOYER,K.; RHODES,C.K.

2000-06-07

A theoretical analysis of laser-driven collisional ejection of inner-shell electrons is presented to explain the previously observed anomalous kilovolt L-shell x-ray emission spectra from atomic Xe cluster targets excited by intense sub-picosecond 248nrn ultraviolet radiation. For incident ponderomotively-driven electrons photoionized by strong above threshold ionization, the collisional ejection mechanism is shown to be highly l-state and significantly n-state (i.e. radially) selective for time periods shorter than the collisional dephasing time of the photoionized electronic wavefunction. The resulting preference for the collisional ejection of 2p electrons by an ionized 4p state produces the measured anomalous Xe(L) emission which contains direct evidence for (i) the generation of Xe{sup 27+}(2p{sup 5}3d{sup 10}) and Xe{sup 28+}(2p{sup 5}3d{sup 9}) ions exhibiting inner-shell population inversion and (ii) a coherent correlated electron state collision responsible for the production of double 2p vacancies. For longer time periods, the selectivity of this coherent impact ionization mechanism is rapidly reduced by the combined effects of intrinsic quantum mechanical spreading and dephasing--in agreement with the experimentally observed and extremely strong {minus}{lambda}{sup {minus}6} pump-laser wavelength dependence of the efficiency of inner-shell (2p) vacancy production in Xe clusters excited in underdense plasmas.

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

International Nuclear Information System (INIS)

Diem, S. J.; Caughman, J. B.; Taylor, G.; Efthimion, P. C.; Kugel, H.; LeBlanc, B. P.; Phillips, C. K.; Preinhaelter, J.; Urban, J.; Sabbagh, S. A.

2009-01-01

The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

Collisional boundary layer analysis for neoclassical toroidal plasma viscosity in tokamaks

International Nuclear Information System (INIS)

Shaing, K. C.; Cahyna, P.; Becoulet, M.; Park, J.-K.; Sabbagh, S. A.; Chu, M. S.

2008-01-01

It is demonstrated that the pitch angle integrals in the transport fluxes in the ν regime calculated in K. C. Shang [Phys. Plasmas 10, 1443 (2003)] are divergent as the trapped-circulating boundary is approached. Here, ν is the collision frequency. The origin of this divergence results from the logarithmic dependence in the bounce averaged radial drift velocity. A collisional boundary layer analysis is developed to remove the singularity. The resultant pitch angle integrals now include not only the original physics of the ν regime but also the boundary layer physics. The transport fluxes, caused by the particles inside the boundary layer, scale as √(ν)

Collisional drift waves in a plasma with electron temperature inhomogeneity

International Nuclear Information System (INIS)

Drake, J.F.; Hassam, A.B.

1981-01-01

A fluid theory of collisional electrostatic drift waves in a plasma slab with magnetic shear is presented. Both electron temperature and density gradients are included. The equations are solved analytically in all relevant regions of the parameter space defined by the magnetic shear strength and the perpendicular wavelength and explicit expressions for the growth rates are given. For shear strengths appropriate for present-day tokamak discharges the temperature gradient produces potential wells which localize the mode in the electron resistive region, well inside the ion sound turning points. Mode stability arises from a competition between the destabilizing influence of the time dependent thermal force and the stabilizing influence of electron energy dissipation. Convective energy loss is not important for shear parameters of present-day fusion devices

Triangularity effects on the collisional diffusion for elliptic tokamak plasma

International Nuclear Information System (INIS)

Martin, P.; Castro, E.

2007-01-01

In this conference the effect of ellipticity and triangularity will be analyzed for axisymmetric tokamak in the collisional regime. Analytic forms for the magnetic field cross sections are taken from those derived recently by other authors [1,2]. Analytical results can be obtained in elliptic plasmas with triangularity by using an special system of tokamak coordinates recently published [3-5]. Our results show that triangularities smaller than 0.6, increases confinement for ellipticities in the range 1.2 to 2. This behavior happens for negative and positive triangularities; however this effect is stronger for positive than for negative triangularities. The maximum diffusion velocity is not obtained for zero triangularity, but for small negative triangularities. Ellipticity is also very important in confinement, but the effect of triangularity seems to be more important. High electric inductive field increases confinement, though this field is difficult to modify once the tokamak has been built. The analytic form of the current produced by this field is like that of a weak Ware pinch with an additional factor, which weakens the effect by an order of magnitude. The dependence of the triangularity effect with the Shafranov shift is also analyzed. References 1. - L. L. Lao, S. P. Hirshman, and R. M. Wieland, Phys. Fluids 24, 1431 (1981) 2. - G. O. Ludwig, Plasma Physics Controlled Fusion 37, 633 (1995) 3. - P. Martin, Phys. Plasmas 7, 2915 (2000) 4. - P. Martin, M. G. Haines and E. Castro, Phys. Plasmas 12, 082506 (2005) 5. - P. Martin, E. Castro and M. G. Haines, Phys. Plasmas 12, 102505 (2005)

Collisional drift waves in the H-mode edge

International Nuclear Information System (INIS)

Sen, S.

1994-01-01

The stability of the collisional drift wave in a sheared slab geometry is found to be severely restricted at the H-mode edge plasma due to the very steep density gradient. However, a radially varying transverse velocity field is found to play the key role in stability. Velocity profiles usually found in the H-mode plasma stabilize drift waves. On the other hand, velocity profiles corresponding to the L-mode render collisional drift waves unstable even though the magnetic shear continues to play its stabilizing role. (author). 24 refs

Destabilization of hydromagnetic drift-Alfven waves in a finite pressure collisional plasma

International Nuclear Information System (INIS)

Tang, J.T.

1974-01-01

In a finite beta (β = 8πn 0 kT 0 /B 0 2 ) plasma, where the plasma pressure n 0 kT 0 is an appreciable fraction of the confining magnetic field energy-density B 0 2 /8π, density-gradient driven drift waves couple with Alfven waves when the phase velocities of the two waves become comparable. The resulting hydromagnetic drift-Alfven waves separate into two branches--a drift mode and an Alfven mode, with both modes exhibiting magnetic field and localized density fluctuations near the coupling point. The dispersion relation of the collisional drift-Alfven wave is derived by using a slab-geometry, two-fluid model which includes finite beta, electron-ion collisions, ion-ion collisions, finite ion larmar radius, temperature fluctuations, and an axial electron current. A hydromagnetic drift mode is found to be unstable in a moderately dense plasma. A localized ''Alfven'' mode is destabilized only with the passage of an axial current along the plasma column. In order to check the theoretical predictions an experiment is performed in a finite-beta plasma of density n 0 = 10 13 -10 15 cm -3 and temperature T/sub e/ approximately T/sub i/ = 1-7 eV. (U.S.)

Collisional particle-in-cell modeling for energy transport accompanied by atomic processes in dense plasmas

Energy Technology Data Exchange (ETDEWEB)

Mishra, R.; Beg, F. N. [Center for Energy Research, University of California, San Diego, California 92093 (United States); Leblanc, P.; Sentoku, Y. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Wei, M. S. [General Atomics, San Diego, California 92121 (United States)

2013-07-15

Fully relativistic collisional Particle-in-Cell (PIC) code, PICLS, has been developed to study extreme energy density conditions produced in intense laser-solid interaction. Recent extensions to PICLS, such as the implementation of dynamic ionization, binary collisions in a partially ionized plasma, and radiative losses, enhance the efficacy of simulating intense laser plasma interaction and subsequent energy transport in resistive media. Different ionization models are introduced and benchmarked against each other to check the suitability of the model. The atomic physics models are critical to determine the energy deposition and transport in dense plasmas, especially when they consist of high Z (atomic number) materials. Finally we demonstrate the electron transport simulations to show the importance of target material on fast electron dynamics.

Space-charge waves in magnetized and collisional quantum plasma columns confined in carbon nanotubes

International Nuclear Information System (INIS)

Bagheri, Mehran; Abdikian, Alireza

2014-01-01

We study the dispersion relation of electrostatic waves propagating in a column of quantum magnetized collisional plasma embraced completely by a metallic single-walled carbon nanotubes. The analysis is based on the quantum linearized hydrodynamic formalism of collective excitations within the quasi-static approximation. It is shown when the electronic de Broglie's wavelength of the plasma is comparable in the order of magnitude to the radius of the nanotube, the quantum effects are quite meaningful and our model anticipates one acoustical and two optical space-charge waves which are positioned into three propagating bands. With increasing the nanotube radius, the features of the acoustical branch remain unchanged, yet two distinct optical branches are degenerated and the classical behavior is recovered. This study might provide a platform to create new finite transverse cross section quantum magnetized plasmas and to devise nanometer dusty plasmas based on the metallic carbon nanotubes in the absence of either a drift or a thermal electronic velocity and their existence could be experimentally examined

Electron heat transport analysis of low-collisionality plasmas in the neoclassical-transport-optimized configuration of LHD

International Nuclear Information System (INIS)

Murakami, Sadayoshi; Yamada, Hiroshi; Wakasa, Arimitsu

2002-01-01

Electron heat transport in low-collisionality LHD plasma is investigated in order to study the neoclassical transport optimization effect on thermal plasma transport with an optimization level typical of so-called ''advanced stellarators''. In the central region, a higher electron temperature is obtained in the optimized configuration, and transport analysis suggests the considerable effect of neoclassical transport on the electron heat transport assuming the ion-root level of radial electric field. The obtained experimental results support future reactor design in which the neoclassical and/or anomalous transports are reduced by magnetic field optimization in a non-axisymmetric configuration. (author)

Plasma out of thermodynamical equilibrium: influence of the plasma environment on atomic structure and collisional cross sections

International Nuclear Information System (INIS)

Belkhiri, Madeny

2014-01-01

In hot dense plasmas, the free-electron and ion spatial distribution may strongly affect the atomic structure. To account for such effects we have implemented a potential correction based on the uniform electron gas model and on a Thomas-Fermi Approach in the Flexible Atomic Code (FAC). This code has been applied to obtain energies, wave-functions and radiative rates modified by the plasma environment. In hydrogen-like ions, these numerical results have been successfully compared to an analytical calculation based on first-order perturbation theory. In the case of multi-electron ions, we observe level crossings in agreement with another recent model calculation. Various methods for the collision cross-section calculations are reviewed. The influence of plasma environment on these cross-sections is analyzed in detail. Some analytical expressions are proposed for hydrogen-like ions in the limit where Born or Lotz approximations apply and are compared to the numerical results from the FAC code. Finally, from this work, we study the influence of the plasma environment on our collisional-radiative model so-called Foch. Because of this environment, the mean charge state of the ions increases. The line shift is observed on the bound-bound emission spectra. A good agreement is found between our work and experimental data on a Titanium plasma. (author) [fr

Modeling of collisional excited x-ray lasers using short pulse laser pumping

Energy Technology Data Exchange (ETDEWEB)

Sasaki, Akira; Moribayashi, Kengo; Utsumi, Takayuki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment

1998-03-01

A simple atomic kinetics model of electron collisional excited x-ray lasers has been developed. The model consists of a collisional radiative model using the average ion model (AIM) and a detailed term accounting (DTA) model of Ni-like Ta. An estimate of plasma condition to produce gain in Ni-like Ta ({lambda}=44A) is given. Use of the plasma confined in a cylinder is proposed to preform a uniform high density plasma from 1-D hydrodynamics calculations. (author)

Experimental evidence for collisional shock formation via two obliquely merging supersonic plasma jets

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)].

Transition from Collisionless to Collisional MRI

International Nuclear Information System (INIS)

Sharma, Prateek; Hammett, Gregory W.; Quataert, Eliot

2003-01-01

Recent calculations by Quataert et al. (2002) found that the growth rates of the magnetorotational instability (MRI) in a collisionless plasma can differ significantly from those calculated using MHD. This can be important in hot accretion flows around compact objects. In this paper, we study the transition from the collisionless kinetic regime to the collisional MHD regime, mapping out the dependence of the MRI growth rate on collisionality. A kinetic closure scheme for a magnetized plasma is used that includes the effect of collisions via a BGK operator. The transition to MHD occurs as the mean free path becomes short compared to the parallel wavelength 2*/k(sub)||. In the weak magnetic field regime where the Alfven and MRI frequencies w are small compared to the sound wave frequency k(sub)||c(sub)0, the dynamics are still effectively collisionless even if omega << v, so long as the collision frequency v << k(sub)||c(sub)0; for an accretion flow this requires n less than or approximately equal to *(square root of b). The low collisionality regime not only modifies the MRI growth rate, but also introduces collisionless Landau or Barnes damping of long wavelength modes, which may be important for the nonlinear saturation of the MRI

Influence of the plasma pedestal parameters on ELM mitigation at low collisionality

Energy Technology Data Exchange (ETDEWEB)

Leuthold, Nils [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany); Universitaet Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth (Germany); Suttrop, Wolfgang [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

2016-07-01

The control of Edge Localized Modes (ELMs) is of great importance for future fusion devices in order to provide longevity of the plasma facing components and a better overall plasma performance. In recent magnetic perturbation ELM mitigation experiments in ASDEX Upgrade at low pedestal collisionality, the dependence of ELM losses on pedestal parameters is investigated. It is found that the reduction of the stored energy loss associated with ELMs occurs in correlation with a reduction of edge density and edge pedestal pressure induced by the applied magnetic perturbation (''pedestal pump-out''). Significant ELM mitigation occurs at lowest densities, in a region of pedestal n-T parameter space that has not been accessible in ASDEX Upgrade without magnetic perturbations, and which is occupied by type-IV ELMs in DIII-D. The role of magnetic perturbations for ELM mitigation will be discussed in this context and attempts to counteract the confinement loss by increasing neutral beam injection power or pellet injection increases the ELM energy losses.

The effect of collisionality and diamagnetism on the plasma dynamo

International Nuclear Information System (INIS)

Ji, H.; Yagi, Y.; Hattori, K.; Hirano, Y.; Shimada, T.; Maejima, Y.; Hayase, K.; Almagri, A.F.; Prager, S.C.; Sarff, J.S.

1995-01-01

Fluctuation-induced dynamo forces are measured over a wide range of electron collisionality in the edge of TPE-1RM20 Reversed-Field Pinch (RFP). In the collisionless region the Magnetohydrodynamic (MHD) dynamo alone can sustain the parallel current, while in the collisional region a new dynamo mechanism resulting from the fluctuations in the electron diamagnetic drift becomes dominant. A comprehensive picture of the RFP dynamo emerges by combining with earlier results from MST and REPUTE RFPs

Particle and parallel momentum balance equations with inclusion of drifts, for modelling strong- to weakly-collisional edge plasmas

International Nuclear Information System (INIS)

Chankin, A. V.; Stangeby, P. C.

2006-01-01

A system of plasma particle and parallel momentum balance equations is derived appropriate for understanding the role of drifts in the edge and for edge modelling, particularly in the scrape-off layer (SOL) of tokamaks, stellarators and other magnetic confinement devices. The formulation allows for strong collisionality-but also covers the case of weak collisionality and strong drifts, a combination often encountered in the SOL. The most important terms are identified by assessing the magnitude of characteristic velocities and fluxes for the plasma edge region. Explanations of the physical nature of each term are provided. A number of terms that are sometimes not included in edge modelling has been included in the parallel momentum balance equation after detailed analysis of the parallel component of the gradient of the total pressure-stress tensor. This includes terms related to curvature and divergence of the field lines, as well as further contributions coming from viscous forces related mainly to the ion centrifugal drift. All these terms are shown to be roughly of the same order of magnitude as convective momentum fluxes related to drifts and therefore should be included in the momentum balance equation

Magnetic Field Effects and Electromagnetic Wave Propagation in Highly Collisional Plasmas.

Science.gov (United States)

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

Collisional plasma transport: two-dimensional scalar formulation of the initial boundary value problem and quasi one-dimensional models

International Nuclear Information System (INIS)

Mugge, J.W.

1979-10-01

The collisional plasma transport problem is formulated as an initial boundary value problem for general characteristic boundary conditions. Starting from the full set of hydrodynamic and electrodynamic equations an expansion in the electron-ion mass ratio together with a multiple timescale method yields simplified equations on each timescale. On timescales where many collisions have taken place for the simplified equations the initial boundary value problem is formulated. Through the introduction of potentials a two-dimensional scalar formulation in terms of quasi-linear integro-differential equations of second order for a domain consisting of plasma and vacuum sub-domains is obtained. (Auth.)

Visco-instability of shear viscoelastic collisional dusty plasma systems

Science.gov (United States)

Mahdavi-Gharavi, M.; Hajisharifi, K.; Mehidan, H.

2018-04-01

In this paper, the stability of Newtonian and non-Newtonian viscoelastic collisional shear-velocity dusty plasmas is studied, using the framework of a generalized hydrodynamic (GH) model. Motivated by Banerjee et al.'s work (Banerjee et al., New J. Phys., vol. 12 (12), 2010, p. 123031), employing linear perturbation theory as well as the local approximation method in the inhomogeneous direction, the dispersion relations of the Fourier modes are obtained for Newtonian and non-Newtonian dusty plasma systems in the presence of a dust-neutral friction term. The analysis of the obtained dispersion relation in the non-Newtonian case shows that the inhomogeneous viscosity force depending on the velocity shear profile can be the genesis of a free energy source which leads the shear system to be unstable. Study of the dust-neutral friction effect on the instability of the considered systems using numerical analysis of the dispersion relation in the Newtonian case demonstrates that the maximum growth rate decreases considerably by increasing the collision frequency in the hydrodynamic regime, while this reduction can be neglected in the kinetic regime. Results show a more significant stabilization role of the dust-neutral friction term in the non-Newtonian cases, through decreasing the maximum growth rate at any fixed wavenumber and construction of the instable wavenumber region. The results of the present investigation will greatly contribute to study of the time evolution of viscoelastic laboratory environments with externally applied shear; where in these experiments the dust-neutral friction process can play a considerable role.

First Test of Long-Range Collisional Drag via Plasma Wave Damping

Science.gov (United States)

Affolter, Matthew

2017-10-01

In magnetized plasmas, the rate of particle collisions is enhanced over classical predictions when the cyclotron radius rc is less than the Debye length λD. Classical theories describe local velocity scattering collisions with impact parameters ρ exchange energy and momentum over the range rc regime, the measured damping rates exceed classical predictions of collisional drag damping by as much as an order of magnitude, but agree with the new long-range enhanced collision theory. The enhanced slowing is most significant for strong magnetization and low temperatures. For example, the slowing of anti-protons at a density of 107 cm-3 and a temperature of 10 K in a 6 T trap is enhanced by a factor of 30. Supported by NSF Grant PHY-1414570 and DOE Grant DE-SC0002451. In collaboration with F. Anderegg, D.H.E. Dubin, and C.F. Driscoll.

Effects of ionization and ion loss on dust ion- acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Science.gov (United States)

Tribeche, Mouloud; Mayout, Saliha

2016-07-01

The combined effects of ionization, ion loss and electron suprathermality on dust ion- acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg- de Vries (dK-- dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK- dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the DIA solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

FDTD simulation of radar cross section reduction by a collisional inhomogeneous magnetized plasma

Science.gov (United States)

Foroutan, V.; Azarmanesh, M. N.; Foroutan, G.

2018-02-01

The recursive convolution finite difference time domain method is addressed in the scattered field formulation and employed to investigate the bistatic radar cross-section (RCS) of a square conductive plate covered by a collisional inhomogeneous magnetized plasma. The RCS is calculated for two different configurations of the magnetic field, i.e., parallel and perpendicular to the plate. The results of numerical simulations show that, for a perpendicularly applied magnetic field, the backscattered RCS is significantly reduced when the magnetic field intensity coincides with the value corresponding to the electron cyclotron resonance. By increasing the collision frequency, the resonant absorption is suppressed, but due to enhanced wave penetration and bending, the reduction in the bistatic RCS is improved. At very high collision frequencies, the external magnetic field has no significant impact on the bistatic RCS reduction. Application of a parallel magnetic field has an adverse effect near the electron cyclotron resonance and results in a large and asymmetric RCS profile. But, the problem is resolved by increasing the magnetic field and/or the collision frequency. By choosing proper values of the collision frequency and the magnetic field intensity, a perpendicular magnetic field can be effectively used to reduce the bistatic RCS of a conductive plate.

On the kinetic collisional theory of beam-plasma system (relativistic dielectric tensor). Vol. 2.

Energy Technology Data Exchange (ETDEWEB)

Khalil, Sh M; Sayed, Y A; Zaki, N G [Plasma Physics and Nuclear Fusion Department, Nuclear Research Center, Atomic Energy Authority, Cairo, (Egypt)

1996-03-01

Calculation of the dielectric tensor is useful for calculating and oscillations the stability of an inhomogeneous plasma. If the dielectric tensor is known, the problem of oscillations is reduced the derivation of the Maxwellian equations. In this case, there is no need to derive the equations of the motion of charged particles every time. The properties of the plasma, especially those connected to its instability, may be equally well specified through permittivity as through conductivity. The features of plasma instabilities and the plasma dielectric tensor are essentially affected by the presence of collision. Coloumb collisions (C.C.) are very important in the process of no linear saturation of some plasma instabilities (e.g., ion cyclotron instability, electron-ion two stream instability). For C.C., two basic properties are considered; (i) the cross section decreases rapidly as the particle velocity increases, (ii) the dominate contribution arises from a commutative effect of small-angle scattering or small-momentum transfer processes. If allowance is made for C.C. to derive the kinetic wave equations in a homogeneous plasma, it will remove the divergance in the matrix elements describing nonlinear interactions. In this paper, the collisional kinetic wave equation in cylindrical hot plasma is studied. The dielectric and polarizing tensor elements which describes the kinetic relativistic electron beam (REB) interaction with magnetized plasma into consideration the effect of pair C.C. is derived. Most research carried out in this direction has neglected the effect of C.C. In the absence of collisions, a `plauste` is formed on the distribution function, and the adsorption of the energy by the plasma stops. 1 fig.

Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2018-04-01

The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

Elements of plasma kinetic theory

International Nuclear Information System (INIS)

Guasp, J.

1976-01-01

The physical foundations of plasma kinetic equations are exposed inside a series of seminars on plasma and fusion physics. The Vlasov and collisional equations with its application range have been discussed. The momenta equations for the macroscopic magnitudes and the more usual approximations have been obtained: two fluid equations for cold and warm plasmas, magnetohydrodynamic equations and the double-adiabatic theory. (author)

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

Energy Technology Data Exchange (ETDEWEB)

Mayout, Saliha; Gougam, Leila Ait [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Tribeche, Mouloud, E-mail: mouloudtribeche@yahoo.fr, E-mail: mtribeche@usthb.dz [Faculty of Physics, Theoretical Physics Laboratory, Plasma Physics Group, University of Bab-Ezzouar, USTHB, B.P. 32, El Alia, Algiers 16111 (Algeria); Algerian Academy of Sciences and Technologies, Algiers (Algeria)

2016-03-15

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Effects of ionization and ion loss on dust ion-acoustic solitary waves in a collisional dusty plasma with suprathermal electrons

International Nuclear Information System (INIS)

Mayout, Saliha; Gougam, Leila Ait; Tribeche, Mouloud

2016-01-01

The combined effects of ionization, ion loss, and electron suprathermality on dust ion-acoustic solitary waves in a collisional dusty plasma are examined. Carrying out a small but finite amplitude analysis, a damped Korteweg-de Vries (dK–dV) equation is derived. The damping term decreases with the increase of the spectral index and saturates for Maxwellian electrons. Choosing typical plasma parameters, the analytical approximate solution of the dK-dV equation is numerically analyzed. We first neglect the ionization and ion loss effects and account only for collisions to estimate the relative importance between these damping terms which can act concurrently. Interestingly, we found that as the suprathermal character of the electrons becomes important, the strength of the collisions related dissipation becomes more important and causes the dust ion-acoustic solitary wave amplitude to decay more rapidly. Moreover, the collisional damping may largely prevail over the ionization and ion loss related damping. The latter becomes more effective as the electrons evolve far away from their thermal equilibrium. Our results complement and provide new insights into previously published work on this problem.

Collisional effects on interaction potential in complex plasma in presence of magnetic field

International Nuclear Information System (INIS)

Bezbaruah, Pratikshya; Das, Nilakshi

2016-01-01

Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

Collisional effects on interaction potential in complex plasma in presence of magnetic field

Energy Technology Data Exchange (ETDEWEB)

Bezbaruah, Pratikshya, E-mail: pratphd@tezu.ernet.in; Das, Nilakshi [Department of Physics, Tezpur University, Tezpur, Assam 784028 (India)

2016-04-15

Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

The Pade approximate method for solving problems in plasma kinetic theory

International Nuclear Information System (INIS)

Jasperse, J.R.; Basu, B.

1992-01-01

The method of Pade Approximates has been a powerful tool in solving for the time dependent propagator (Green function) in model quantum field theories. We have developed a modified Pade method which we feel has promise for solving linearized collisional and weakly nonlinear problems in plasma kinetic theory. In order to illustrate the general applicability of the method, in this paper we discuss Pade solutions for the linearized collisional propagator and the collisional dielectric function for a model collisional problem. (author) 3 refs., 2 tabs

Collisional Thermalization in Strongly Coupled Ultracold Neutral Plasmas

Science.gov (United States)

2017-01-25

calculated collisions rates in a strongly coupled plasma. From Bannasch et al., PRL 109, 185008 (2012). DISTRIBUTION A: Distribution approved for public...applicability to other plasmas.) We use a Green- Kubo relation to extract the diffusion constant from our measurements of the relaxation towards...strongly coupled systems. Our measurements (data symbols) agree with numerical calculations (solid lines) from J. Daligault, PRL 108, 225004 (2012

Multi-fluid Approach to High-frequency Waves in Plasmas. III. Nonlinear Regime and Plasma Heating

Science.gov (United States)

Martínez-Gómez, David; Soler, Roberto; Terradas, Jaume

2018-03-01

The multi-fluid modeling of high-frequency waves in partially ionized plasmas has shown that the behavior of magnetohydrodynamic waves in the linear regime is heavily influenced by the collisional interaction between the different species that form the plasma. Here, we go beyond linear theory and study large-amplitude waves in partially ionized plasmas using a nonlinear multi-fluid code. It is known that in fully ionized plasmas, nonlinear Alfvén waves generate density and pressure perturbations. Those nonlinear effects are more pronounced for standing oscillations than for propagating waves. By means of numerical simulations and analytical approximations, we examine how the collisional interaction between ions and neutrals affects the nonlinear evolution. The friction due to collisions dissipates a fraction of the wave energy, which is transformed into heat and consequently raises the temperature of the plasma. As an application, we investigate frictional heating in a plasma with physical conditions akin to those in a quiescent solar prominence.

Terahertz radiation generation by beating of two laser beams in a collisional plasma with oblique magnetic field

Science.gov (United States)

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.

Analytical investigation on domain of decentered parameter for self-focusing of Hermite-cosh-Gaussian laser beam in collisional plasma

Science.gov (United States)

Valkunde, Amol T.; Patil, Sandip D.; Vhanmore, Bandopant D.; Urunkar, Trupti U.; Gavade, Kusum M.; Takale, Mansing V.; Fulari, Vijay J.

2018-03-01

In the present paper, an analytically investigated domain of decentered parameter and its effect on the self-focusing of Hermit-cosh-Gaussian (HChG) laser beams in a collisional plasma have been studied theoretically. The nonlinearity in the dielectric constant of plasma arising due to the nonuniform heating of carriers along the wavefront of the laser beam has been employed in the present investigation. The nonlinear differential equation of beam width parameter for various laser modes of HChG beam is obtained by following the standard Akhamanov's parabolic equation approach under Wentzel-Kramers-Brillouin and paraxial approximations. The analytical treatment has enabled us to define three distinct regions: self-focusing, self-trapping and defocusing, which are presented graphically.

MHD description of plasma: handbook of plasma physics

International Nuclear Information System (INIS)

Kulsrud, R.M.

1980-10-01

The basic sets of MHD equations for the description of a plasma in various limits are derived and their usefulness and limits of validity are discussed. These limits are: the one fluid collisional plasma, the two fluid collisional plasma, the Chew-Goldberger Low formulation of the guiding center limit of a collisionless plasma and the double-adiabatic limit. Conservation relations are derived from these sets and the mathematics of the concept of flux freezing is given. An example is given illustrating the differences between guiding center theory and double adiabatic theory

Quantum degeneracy corrections to plasma line emission and to Saha equation

International Nuclear Information System (INIS)

Molinari, V.G.; Mostacci, D.; Rocchi, F.; Sumini, M.

2003-01-01

The effect of quantum degeneracy on the electron collisional excitation is investigated, and its effects on line emission evaluated for applications to spectroscopy of dense, cold plasmas. A correction to Saha equation for weakly-degenerate plasmas is also presented

Anomalous transport of charged dust grains in a magnetized collisional plasma: A molecular dynamics study

Science.gov (United States)

Bezbaruah, Pratikshya; Das, Nilakshi

2018-05-01

Anomalous diffusion of charged dust grains immersed in a plasma in the presence of strong ion-neutral collision, flowing ions, and a magnetic field has been observed. Molecular Dynamics simulation confirms the deviation from normal diffusion in an ensemble of dust grains probed in laboratory plasma chambers. Collisional effects are significant in governing the nature of diffusion. In order to have a clear idea on the transport of particles in a real experimental situation, the contribution of streaming ions and the magnetic field along with collision is considered through the relevant interaction potential. The nonlinear evolution of Mean Square Displacement is an indication of the modification in particle trajectories due to several effects as mentioned above. It is found that strong collision and ion flow significantly affect the interparticle interaction potential in the presence of the magnetic field and lead to the appearance of the asymmetric type of Debye Hückel (D H) potential. Due to the combined effect of the magnetic field, ion flow, and collision, dusty plasma exhibits a completely novel behavior. The coupling parameter Γ enhances the asymmetric D H type potential arising due to ion flow, and this may drive the system to a disordered state.

Study of carbon ion behavior by using collisional radiative model in the GAMMA 10 tandem mirror

International Nuclear Information System (INIS)

Kobayashi, Takayuki; Yoshikawa, Masayuki; Kubota, Yuusuke; Saito, Masashi; Matama, Ken; Itakura, Akiyoshi; Cho, Teruji; Kato, Takako

2006-01-01

In a plasma experiment, collisional radiative model (CRM) is very useful model to evaluate impurity behaviors and plasma parameters with line emission from a plasma. CRMs for carbon and oxygen have been developed. However verification and application of the model for analysis of experimental results are not enough. Then we applied CRM calculation results to observed impurity spectra in the GAMMA 10 tandem mirror to evaluate the impurity density profile and the particle balance of each charge state of carbon ion. We calculated the effective ionization rate for each charge state of carbon ion and obtained the density profile of each ion. Moreover, we calculated absolute emission intensities from all carbon ions. (author)

Self-consistent Kinetic Simulation of RMP-driven Transport: Collisionality and Rotation Effects on RMP Penetration and Transport

Energy Technology Data Exchange (ETDEWEB)

Park, G.; Jeon, Y.; Kim, J., E-mail: gypark@nfri.re.kr [NFRI, Daejeon (Korea, Republic of); Chang, C. [Princeton Plasma Physics Laboratory, Princeton (United States)

2012-09-15

Full text: Control of the edge localized modes (ELMs) is one of the most critical issues for a more successful operation of ITER and the future tokamak fusion reactors. This paper reports ITER relevant simulation results from the XGC0 drift-kinetic code, with respect to the collisionality, plasma density, and rotation dependence of the RMP penetration and the RMP-driven transport in diverted DIII-D geometry with neutral recycling. The simulation results are consistent with the experimental results, and contribute to the physics understanding needed for more confident extrapolation of the present RMP experiments to ITER. It is found that plasma-responded stochasticity becomes weaker as the collisionality gets higher and RMP-driven transport (i.e., density pump-out) is much weaker in the high collisionality case compared with that in the low collisionality one, which is consistent with the recent experimental results on DIII-D and ASDEX-U tokamaks. As for rotation effect, low rotation is found not to affect the stochasticity much in the edge region, while high rotation significantly suppresses the RMPs in the core. The clear difference in RMP behavior between the low and high collisionality regimes can be understood by examining the perturbed current Fourier amplitude profiles within the range of resonant poloidal mode numbers (m = 8 - 15, n = 3). It can be seen that primary shielding currents are strongly concentrated around the steep pedestal region just inside the separatrix, which naturally produces very strong suppression of RMPs there, in low collisionality case. However, in high collisionality case, primary shielding currents are very weak and accumulating toward inner radii leading to the shielding of RMPs further into the plasma. Our kinetic simulation method is also applied to the modeling of RMP ELM control experiments on KSTAR tokamak and the results will be presented together. (author)

Nonlocal collisionless and collisional electron transport in low temperature plasmas

Science.gov (United States)

Kaganovich, Igor

2009-10-01

The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and

Nonlocal transport in hot plasma. Part I

International Nuclear Information System (INIS)

Brantov, A. V.; Bychenkov, V. Yu.

2013-01-01

The problem of describing charged particle transport in hot plasma under the conditions in which the ratio of the electron mean free path to the gradient length is not too small is one of the key problems of plasma physics. However, up to now, there was a deficit of the systematic interpretation of the current state of this problem, which, in most studies, is formulated as the problem of nonlocal transport. In this review, we fill this gap by presenting a self-consistent linear theory of nonlocal transport for small plasma perturbations and an arbitrary collisionality from the classical highly collisional hydrodynamic regime to the collisionless regime. We describe a number of nonlinear transport models and demonstrate the application of the nonclassical transport theory to the solution of some problems of plasma physics, first of all for plasmas produced by nanosecond laser pulses with intensities of 10 13 –10 16 W/cm 2

Determination of electron temperature and density at plasma edge in the Large Helical Device with opacity-incorporated helium collisional-radiative model

International Nuclear Information System (INIS)

Goto, M.; Sawada, K.

2014-01-01

Spectra of neutral helium in the visible wavelength range are measured for a discharge in the Large Helical Device (LHD). The electron temperature (T e ) and density (n e ) are derived from the intensity distribution of helium emission lines. For that purpose, a collisional-radiative model developed by Sawada et al. [Plasma and Fusion Res. 2010;5:001] which takes the reabsorption effect into account is used. It is found that incorporation of the reabsorption effect is necessary to obtain a set of T e and n e giving consistent line intensity distribution with the measurement, and that those parameters obtained vary as the line-averaged n e changes in the course of time. The position where the helium line emission dominantly takes place is located with the help of T e and n e profiles measured by the Thomson scattering system. The result indicates that the emission position is almost fixed at the place where the connection length of the magnetic field lines to the divertor plate leaps beyond 10 m. Because intense neutral atom line emission suggests the vigorous ionization of neutral atoms, the helium line emission location determined here can be regarded as the effective boundary of the plasma. - Highlights: • The reabsorption effect is included in the helium collisional-radiative model. • Electron temperature and density are derived for the Large Helical Device (LHD). • Line emission location is found to be little changed during the discharge. • This measurement method can be used to determine the position of effective plasma boundary

Collisional transport across the magnetic field in drift-fluid models

DEFF Research Database (Denmark)

Madsen, Jens; Naulin, Volker; Nielsen, Anders Henry

2016-01-01

Drift ordered fluid models are widely applied in studies of low-frequency turbulence in the edge and scrape-off layer regions of magnetically confined plasmas. Here, we show how collisional transport across the magnetic field is self-consistently incorporated into drift-fluid models without...

On the mechanism of energy transfer in the plasma-propellant interaction

Energy Technology Data Exchange (ETDEWEB)

Porwitzky, Andrew J.; Keidar, Michael; Boyd, Iain D. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, Michigan 48109-2140 (United States)

2007-10-15

A coupled plasma sheath/ablation model is developed for electrothermal chemical gun applications. By combining a commonly employed collisional sheath model with a previous ablation model, the convective heat flux as a function of time to the propellant bed is determined for two potential electrothermal chemical gun propellants, XM39 and JA2. It is found that the convective heat flux varies smoothly from a nearly collisionless to a fully collisional regime over the short duration of the plasma pulse. The possibility of determining an accurate estimate of the amount of heat flux to the propellant bed due to radiation from the bulk plasma presents itself. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Collisional-Radiative Modeling of Tungsten at Temperatures of 1200–2400 eV

Directory of Open Access Journals (Sweden)

James Colgan

2015-04-01

Full Text Available We discuss new collisional-radiative modeling calculations of tungsten at moderate temperatures of 1200 to 2400 eV. Such plasma conditions are relevant to ongoing experimental work at ASDEX Upgrade and are expected to be relevant for ITER. Our calculations are made using the Los Alamos National Laboratory (LANL collisional-radiative modeling ATOMIC code. These calculations formed part of a submission to the recent NLTE-8 workshop that was held in November 2013. This series of workshops provides a forum for detailed comparison of plasma and spectral quantities from NLTE collisional-radiative modeling codes. We focus on the LANL ATOMIC calculations for tungsten that were submitted to the NLTE-8 workshop and discuss different models that were constructed to predict the tungsten emission. In particular, we discuss comparisons between semi-relativistic configuration-average and fully relativistic configuration-average calculations. We also present semi-relativistic calculations that include fine-structure detail, and discuss the difficult problem of ensuring completeness with respect to the number of configurations included in a CR calculation.

Recommended atomic data for collisional-radiative model of Li-like ions and gain calculation for Li-like Al ions in the recombining plasma

International Nuclear Information System (INIS)

Nishikawa, T.; Kawachi, T.; Nishihara, K.; Fujimoto, T.

1995-09-01

We have assessed atomic data for lithium-like ions for the purpose of constructing a reliable collisional-radiative model. We show several examples of the atomic data for aluminum and oxygen ions, and comparison of data from several sources is done in detail. For ions with nuclear charge z, the scaling formulas and fitting parameters, which are based on the data of oxygen ions, are presented. By use of these data, we have constructed two collisional-radiative models: the one for aluminum ions and the one for ions according to the scaling for z. The population inversion and the amplification gain of the soft x-ray laser lines in the recombining aluminum plasma are calculated for several electron temperatures. We also examine the effects of ion collisions for Δn=0 transitions on the excited level populations

Local thermodynamic equilibrium and related metrological issues involving collisional-radiative model in laser-induced aluminum plasmas

International Nuclear Information System (INIS)

Travaille, G.; Peyrusse, O.; Bousquet, B.; Canioni, L.; Pierres, K. Michel-Le; Roy, S.

2009-01-01

We present a collisional-radiative approach of the theoretical analysis of laser-induced breakdown spectroscopy (LIBS) plasmas. This model, which relies on an optimized effective potential atomic structure code, was used to simulate a pure aluminum plasma. The description of aluminum involved a set of 220 atomic levels representative of three different stages of ionization (Al 0 , Al + and Al ++ ). The calculations were carried for stationary plasmas, with input parameters (n e and T e ) ranging respectively between 10 13-18 cm -3 and 0.3-2 eV. A comparison of our atomic data with some existing databases is made. The code was mainly developed to address the validity of the local thermodynamic equilibrium (LTE) assumption. For usual LIBS plasma parameters, we did not reveal a sizeable discrepancy of the radiative equilibrium of the plasma towards LTE. For cases where LTE was firmly believed to stand, the Boltzmann plot outputs of this code were used to check the physical accuracy of the Boltzmann temperature, as it is currently exploited in several calibration-free laser-induced breakdown spectroscopy (CF-LIBS) studies. In this paper, a deviation ranging between 10 and 30% of the measured Boltzmann temperature to the real excitation temperature is reported. This may be due to the huge dispersion induced on the line emissivities, on which the Boltzmann plots are based to extract this parameter. Consequences of this fact on the CF-LIBS procedure are discussed and further insights to be considered for the future are introduced.

Influence of Kohn singularity on the occurrence scattering time in degenerate quantum collisional plasmas

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-10-01

The influence of Kohn singularity on the occurrence scattering time for the electron-ion interaction is investigated in degenerate quantum collisional plasmas. The first-order eikonal analysis is used to obtain the scattering amplitude and the occurrence scattering time. The result shows that the Friedel oscillation due to the Kohn singularity suppresses the advance phenomena of occurrence scattering time in both forward and backward scattering domains. It is shown that the increase of plasmon energy would reduce the time advance for both forward and backward scattering domains. However, the increase of Fermi energy would enhance the phenomena of time advance. It is also found that the time advance with high collision frequency is larger than that with low collision frequency for the forward scattering domain and vice versa for the backward scattering domain. We have shown that the time advance is stronger in general for the forward scattering domain than that for the backward scattering domain.

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

Energy Technology Data Exchange (ETDEWEB)

Landreman, M., E-mail: mattland@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Smith, H. M.; Helander, P. [Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); Mollén, A. [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden)

2014-04-15

In this work, we examine the validity of several common simplifying assumptions used in numerical neoclassical calculations for nonaxisymmetric plasmas, both by using a new continuum drift-kinetic code and by considering analytic properties of the kinetic equation. First, neoclassical phenomena are computed for the LHD and W7-X stellarators using several versions of the drift-kinetic equation, including the commonly used incompressible-E × B-drift approximation and two other variants, corresponding to different effective particle trajectories. It is found that for electric fields below roughly one third of the resonant value, the different formulations give nearly identical results, demonstrating the incompressible E × B-drift approximation is quite accurate in this regime. However, near the electric field resonance, the models yield substantially different results. We also compare results for various collision operators, including the full linearized Fokker-Planck operator. At low collisionality, the radial transport driven by radial gradients is nearly identical for the different operators; while in other cases, it is found to be important that collisions conserve momentum.

Sheath waves, non collisional dampings

International Nuclear Information System (INIS)

Marec, Jean Lucien Ernest

1974-01-01

When a metallic conductor is inserted into an ionised gas, an area of electron depletion is formed between the conductor and the plasma: the ionic sheath. Moreover, if the conductor is excited by an electric field, this ionic sheath plays an important role with respect to microwave properties. In this research thesis, the author addresses the range of frequencies smaller than the plasma frequency, and reports the study of resonance phenomena. After a presentation of the problem through a bibliographical study, the author recalls general characteristics of sheath wave propagation and of sheath resonances, and discusses the validity of different hypotheses (for example and among others, electrostatic approximations, cold plasma). Then, the author more particularly addresses theoretical problems related to non collisional dampings: brief bibliographical study, detailed presentation and description of the theoretical model, damping calculation methods. The author then justifies the design and performance of an experiment, indicates measurement methods used to determine plasma characteristics as well as other magnitudes which allow the description of mechanisms of propagation and damping of sheath waves. Experimental results are finally presented with respect to various parameters. The author discusses to which extent the chosen theoretical model is satisfying [fr

Collisional-radiative model including recombination processes for W27+ ion★

Science.gov (United States)

Murakami, Izumi; Sasaki, Akira; Kato, Daiji; Koike, Fumihiro

2017-10-01

We have constructed a collisional-radiative (CR) model for W27+ ions including 226 configurations with n ≤ 9 and ł ≤ 5 for spectroscopic diagnostics. We newly include recombination processes in the model and this is the first result of extreme ultraviolet spectrum calculated for recombining plasma component. Calculated spectra in 40-70 Å range in ionizing and recombining plasma components show similar 3 strong lines and 1 line weak in recombining plasma component at 45-50 Å and many weak lines at 50-65 Å for both components. Recombination processes do not contribute much to the spectrum at around 60 Å for W27+ ion. Dielectronic satellite lines are also minor contribution to the spectrum of recombining plasma component. Dielectronic recombination (DR) rate coefficient from W28+ to W27+ ions is also calculated with the same atomic data in the CR model. We found that larger set of energy levels including many autoionizing states gave larger DR rate coefficients but our rate agree within factor 6 with other works at electron temperature around 1 keV in which W27+ and W28+ ions are usually observed in plasmas. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, and Grzegorz Karwasz.

Dynamo transformation of the collisional R-T in a weakly ionized ...

Indian Academy of Sciences (India)

where the interstellar neutrals undergo charge exchange collisions with ions in the solar wind [1]. ... regime of magnetically confined torroidal plasma. The author refutes their ... rate ´7К-М µ for the usual collisional R-T is given as. 7К-М g v Дp.

Comment on 'Ion collection by a sphere in a flowing collisional plasma' [Phys. Plasmas 14, 034502 (2007)

International Nuclear Information System (INIS)

Hutchinson, I. H.

2007-01-01

It is shown that the numerical solutions presented in a recent paper discussing a highly simplified model of collisional particle collection are unnecessary because simple analytic solutions of the quantities presented are available

Effects of pressure anisotropy on plasma transport

International Nuclear Information System (INIS)

Zawaideh, E.; Najmabadi, F.; Conn, R.W.

1986-03-01

In a recent paper a new set of generalized two-field equations is derived which describes plasma transport along the field lines of a space and time dependent magnetic field. These equations are valid for collisional to weakly collisional plasmas; they reduce to the conventional fluid equations of Braginskii for highly collisional plasmas. An important feature of these equations is that the anisotropy in the ion pressure is explicitly included. In this paper, these generalized transport equations are applied to a model problem of plasma flow through a magnetic mirror field. The profiles of the plasma parameters (density, flow speed, and pressures) are numerically calculated for plasma in different collisionality regimes. These profiles are explained by examining the competing terms in the transport equation. The pressure anisotropy is found to profoundly impact the plasma flow behavior. As a result, the new generalized equations predict flow behavior more accurately than the conventional transport equations. A large density and pressure drop is predicted as the flow passes through a magnetic mirror. Further, the new equations uniquely predict oscillations in the density profile, an effect missing in results from the conventional equations

Determination of microturbulence enhanced electron collisionality in magnetized coaxial accelerator channels by direct magnetic field measurement

International Nuclear Information System (INIS)

Black, D.C.; Mayo, R.M.; Caress, R.W.

1997-01-01

A miniature magnetic probe array, consisting of 10 spatially separated coils, has been used to obtain profile information on the time varying magnetic field within the 2.54 cm wide flow channel of the coaxial plasma source experiment (CPS-1) [R. M. Mayo et al., Plasma Sources Sci. Technol. 4, 47 (1995)]. The magnetic field data have been used, together with a resistive, Hall magnetohydrodynamic (MHD) model of applied field distortion by the flowing plasma, to obtain estimates of the microturbulent enhancement to electron collisionality within the CPS-1 flow channel. These measurements provide direct experimental evidence of anomalous electron collisionality, a previously predicted effect in these devices. The anomaly parameter, a=ν an /ν cl , determined both from the distortion of contours of constant magnetic flux, and from local B θ and B z measurements scales with the classical electron magnetization parameter (Ω cl =ω ce /ν e cl ), indicating that collisionality plays a strong role in determining the level of anomalous transport in the plasma. When this anomaly parameter scaling is cast in terms of the ratio ν e cl /ω lh , it is found that the resistivity enhancement scales with ν e cl /ω lh , and becomes significant at ν e cl /ω lh ≤1, suggesting that a lower hybrid drift instability may be the responsible mechanism for enhanced transport. copyright 1997 American Institute of Physics

Collisional processes of interest in MFE plasma research. Annual report, October 1, 1985-July 31, 1986

International Nuclear Information System (INIS)

Olson, R.E.

1986-01-01

Research on this grant can be divided into two general topics: (1) determination of electron capture cross sections between impurity ions and hydrogen atoms needed for diagnostic studies of magnetic fusion plasmas, and (2) studies into reactions important in neutral beam ion source work. For topic (1) during last year, we completed cross section calculations for B 3+ and Be 2+ on H using the molecular state approach for energies between 50 eV/u and 10 keV/u. At higher energies, 40 keV/u to 140 keV/u, we have completed classical trajectory Monte Carlo calculations to determine the nl electron capture cross sections for He 2+ , C 6+ , N 7+ and O 8+ on H collisions. For ion source work, topic (2), collisional studies were completed for negative ion formation in the process H + Na → H - + Na +

Near field imaging of transient collisional excitation x-ray laser

International Nuclear Information System (INIS)

Tanaka, Momoko; Kado, Masataka; Hasegawa, Noboru; Kawachi, Tetsuya; Sukegawa, Kouta; Lu, Peixiang; Nagashima, Akira; Kato, Yoshiaki

2001-01-01

We observed the spatial profile of the transient collisional excitation Ni-like Ag laser (λ=13.9 nm) for various plasma lengths using the near field imaging method. The gain coefficient of the x-ray laser was estimated as 24 cm -1 . The gain region was a 50 μm crescent shape and included localized high gain areas. (author)

Collisional radiative model for Ar-O2 mixture plasma with fully relativistic fine structure cross sections

Science.gov (United States)

Priti, Gangwar, Reetesh Kumar; Srivastava, Rajesh

2018-04-01

A collisional radiative (C-R) model has been developed to diagnose the rf generated Ar-O2 (0%-5%) mixture plasma at low temperatures. Since in such plasmas the most dominant process is an electron impact excitation process, we considered several electron impact fine structure transitions in an argon atom from its ground as well as excited states. The cross-sections for these transitions have been obtained using the reliable fully relativistic distorted wave theory. Processes which account for the coupling of argon with the oxygen molecules have been further added to the model. We couple our model to the optical spectroscopic measurements reported by Jogi et al. [J. Phys. D: Appl. Phys. 47, 335206 (2014)]. The plasma parameters, viz. the electron density (ne) and the electron temperature (Te) as a function of O2 concentration have been obtained using thirteen intense emission lines out of 3p54p → 3p54s transitions observed in their spectroscopic measurements. It is found that as the content of O2 in Ar increases from 0%-5%, Te increases in the range 0.85-1.7 eV, while the electron density decreases from 2.76 × 1012-2.34 × 1011 cm-3. The Ar-3p54s (1si) fine-structure level populations at our extracted plasma parameters are found to be in very good agreement with those obtained from the measurements. Furthermore, we have estimated the individual contributions coming from the ground state, 1si manifolds and cascade contributions to the population of the radiating Ar-3p54p (2pi) states as a function of a trace amount of O2. Such information is very useful to understand the importance of various processes occurring in the plasma.

Computation of the Spitzer function in stellarators and tokamaks with finite collisionality

Directory of Open Access Journals (Sweden)

Kernbichler Winfried

2015-01-01

Full Text Available The generalized Spitzer function, which determines the current drive efficiency in toka- maks and stellarators is modelled for finite plasma collisionality with help of the drift kinetic equation solver NEO-2 [1]. The effect of finite collisionality on the global ECCD efficiency in a tokamak is studied using results of the code NEO-2 as input to the ray tracing code TRAVIS [2]. As it is known [3], specific features of the generalized Spitzer function, which are absent in asymptotic (collisionless or highly collisional regimes result in current drive from a symmetric microwave spectrum with respect to parallel wave numbers. Due to this effect the direction of the current may become independent of the microwave beam launch angle in advanced ECCD scenarii (O2 and X3 where due to relatively low optical depth a significant amount of power is absorbed by trapped particles.

SCROLL, a superconfiguration collisional radiative model with external radiation

International Nuclear Information System (INIS)

Bar-Shalom, A.; Oreg, J.; Klapisch, M.

2000-01-01

A collisional radiative model for calculating non-local thermodynamical-equilibrium (non-LTE) spectra of heavy atoms in hot plasmas has been developed. It takes into account the numerous excited an autoionizing states by using superconfigurations. These are split systematically until the populations converge. The influence of an impinging radiation field has recently been added to the model. The effect can be very important. (author)

On various validity criteria for the configuration average in collisional-radiative codes

Energy Technology Data Exchange (ETDEWEB)

Poirier, M [Commissariat a l' Energie Atomique, Service ' Photons, Atomes et Molecules' , Centre d' Etudes de Saclay, F91191 Gif-sur-Yvette Cedex (France)

2008-01-28

The characterization of out-of-local-thermal-equilibrium plasmas requires the use of collisional-radiative kinetic equations. This leads to the solution of large linear systems, for which statistical treatments such as configuration average may bring considerable simplification. In order to check the validity of this procedure, a criterion based on the comparison between a partial-rate systems and the Saha-Boltzmann solution is discussed in detail here. Several forms of this criterion are discussed. The interest of these variants is that they involve each type of relevant transition (collisional or radiative), which allows one to check separately the influence of each of these processes on the configuration-average validity. The method is illustrated by a charge-distribution analysis in carbon and neon plasmas. Finally, it is demonstrated that when the energy dispersion of every populated configuration is smaller than the electron thermal energy, the proposed criterion is fulfilled in each of its forms.

Transition from the constant ion mobility regime to the ion-atom charge-exchange regime for bounded collisional plasmas

International Nuclear Information System (INIS)

Poggie, Jonathan; Sternberg, Natalia

2005-01-01

A numerical and analytical study of a planar, collisional, direct-current, plasma-wall problem is presented. The fluid model for the problem is first validated by comparing numerical solutions with experimental data for low-pressure (∼0.1 Pa) electrode sheaths with wall potentials on the order of -100 V. For electric potential, ion number density, and ion velocity, good agreement was found between theory and experiment from within the sheath out to the bulk plasma. The frictional drag resulting from ion-neutral collisions is described by a model incorporating both linear and quadratic velocity terms. In order to study the transition from the constant ion mobility regime (linear friction) to the ion-atom charge-exchange collision regime (quadratic friction), the theoretical model was examined numerically for a range of ion temperatures and ion-neutral collision rates. It was found that the solution profiles in the quasineutral plasma depend on the ion temperature. For low ion temperatures they are governed mainly by the ion-atom charge-exchange regime, whereas for high temperatures they are governed by the constant ion mobility regime. Quasineutral plasma models corresponding to these two limiting cases were solved analytically. In particular, an analytical plasma solution is given for the ion-atom charge exchange regime that includes the effects of ion inertia. In contrast to the quasineutral plasma, the sheath is always governed for low to moderate collision rates by the ion-atom charge-exchange regime, independent of the ion temperature. Varying the collision rate, it was shown that when the wall potential is sufficiently high, the sheath cannot be considered collisionless, even if the collision rate is quite small

Non linear evolution of plasma waves excited to mode conversion at the vicinity of plasma resonance. Application to experiments of ionosphere modification

International Nuclear Information System (INIS)

Cros, Brigitte

1989-01-01

This research thesis reports the study of the non linear evolution of plasma waves excited by mode conversion in a non homogeneous, non collisional, and free-of-external-magnetic-field plasma. Experiments performed in the microwave domain in a plasma created by means of a multi-polar device show that the evolution of plasma waves displays a transition between a non linear quasi-steady regime and a stochastic regime when the power of incident electromagnetic waves or plasma gradient length is increased. These regimes are characterized through a numerical resolution of Zakharov equations which describe the coupled evolution of plasma wave envelope and low frequency density perturbations [fr

Double layers in a modestly collisional electronegative discharge

CERN Document Server

Sheridan, T E

1999-01-01

The effect of ion-neutral collisions on the structure and ion flux emanating from a steady-state, planar discharge with two negative components is investigated. The positive ion component is modelled as a cold fluid subject to constant-mobility collisions, while the electrons and negative ions obey Boltzmann relations. The model includes the collisionless limit. When the negative ions are sufficiently cold three types of discharge structures are found. For small negative ion concentrations or high collisionality, the discharge is 'stratified', with an electronegative core and an electropositive edge. For the opposite conditions, the discharge is 'uniform' with the negative ion density remaining significant at the edge of the plasma. Between these cases lies the special case of a double-layer-stratified discharge, where quasi-neutrality is violated at the edge of the electronegative core. Double-layer-stratified solutions are robust in that they persist for moderate collisionality. Numerical solutions for fini...

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.

A lattice based solution of the collisional Boltzmann equation with applications to microchannel flows

International Nuclear Information System (INIS)

Green, B I; Vedula, Prakash

2013-01-01

An alternative approach for solution of the collisional Boltzmann equation for a lattice architecture is presented. In the proposed method, termed the collisional lattice Boltzmann method (cLBM), the effects of spatial transport are accounted for via a streaming operator, using a lattice framework, and the effects of detailed collisional interactions are accounted for using the full collision operator of the Boltzmann equation. The latter feature is in contrast to the conventional lattice Boltzmann methods (LBMs) where collisional interactions are modeled via simple equilibrium based relaxation models (e.g. BGK). The underlying distribution function is represented using weights and fixed velocity abscissas according to the lattice structure. These weights are evolved based on constraints on the evolution of generalized moments of velocity according to the collisional Boltzmann equation. It can be shown that the collision integral can be reduced to a summation of elementary integrals, which can be analytically evaluated. The proposed method is validated using studies of canonical microchannel Couette and Poiseuille flows (both body force and pressure driven) and the results are found to be in good agreement with those obtained from conventional LBMs and experiments where available. Unlike conventional LBMs, the proposed method does not involve any equilibrium based approximations and hence can be useful for simulation of highly nonequilibrium flows (for a range of Knudsen numbers) using a lattice framework. (paper)

Plasma probe characteristics in low density hydrogen pulsed plasmas

International Nuclear Information System (INIS)

Astakhov, D I; Lee, C J; Bijkerk, F; Goedheer, W J; Ivanov, V V; Krivtsun, V M; Zotovich, A I; Zyryanov, S M; Lopaev, D V

2015-01-01

Probe theories are only applicable in the regime where the probe’s perturbation of the plasma can be neglected. However, it is not always possible to know, a priori, that a particular probe theory can be successfully applied, especially in low density plasmas. This is especially difficult in the case of transient, low density plasmas. Here, we applied probe diagnostics in combination with a 2D particle-in-cell model, to an experiment with a pulsed low density hydrogen plasma. The calculations took into account the full chamber geometry, including the plasma probe as an electrode in the chamber. It was found that the simulations reproduce the time evolution of the probe IV characteristics with good accuracy. The disagreement between the simulated and probe measured plasma density is attributed to the limited applicability of probe theory to measurements of low density pulsed plasmas on a similarly short time scale as investigated here. Indeed, in the case studied here, probe measurements would lead to, either a large overestimate, or underestimate of the plasma density, depending on the chosen probe theory. In contrast, the simulations of the plasma evolution and the probe characteristics do not suffer from such strict applicability limits. These studies show that probe theory cannot be justified through probe measurements. However, limiting cases of probe theories can be used to estimate upper and lower bounds on plasma densities. These theories include and neglect orbital motion, respectively, with different collisional terms leading to intermediate estimates. (paper)

Magnetic confinement fusion plasma theory, Task 1

International Nuclear Information System (INIS)

Callen, J.D.

1991-07-01

The research performed under this grant during the current year has concentrated on a few key tokamak plasma confinement and heating theory issues: extensive development of a new Chapman-Enskog-like fluid/kinetic hybrid approach to deriving rigorously valid fluid moment equations; applications (neoclassical viscous force, instabilities in the banana-plateau collisionality regime, nonlinear gyroviscous force, unified plasma microinstability equations and their implications, semi-collisional presheath modeling, etc.) of this new formalism; interactions of fluctuating bootstrap-current-driven magnetic islands; determination of net transport processes and equations for a tokamak; and some other topics (extracting more information from heat-pulse-propagation data, modeling of BES fluctuation data, exploring sawtooth effects on energy confinement in DIII-D, divertor X-point modeling). Recent progress and publications in these areas, and in the management of the local NERSC node and fusion theory DECstation 5000 at UW-Madison are summarized briefly in this report

A High-Order Transport Scheme for Collisional-Radiative and Nonequilibrium Plasma

Science.gov (United States)

2009-02-06

400–422, 1987. [18] M. P. F. Bristow and I. I. Glass. Polarizability of singly ionized argon . Physics of Fluids, 15(11):2066–2067, 1972. [19] A. Bultel...unsteady calculations. Numerical simulations of ionizing shocks in argon are conducted to gain insight to the shock structure and help determine the source...parameters used in previous research. . . . . . . . . 4 9.1 Rate coefficients for collisional-radiative model . . . . . . . . . . . . . . . . . 83 9.2 Argon

A collisional radiative model of hydrogen plasmas developed for diagnostic purposes of negative ion sources

Energy Technology Data Exchange (ETDEWEB)

Iordanova, Snejana, E-mail: snejana@phys.uni-sofia.bg; Paunska, Tsvetelina [Faculty of Physics, Sofia University, BG-1164 Sofia (Bulgaria)

2016-02-15

A collisional radiative model of low-pressure hydrogen plasmas is elaborated and applied in optical emission spectroscopy diagnostics of a single element of a matrix source of negative hydrogen ions. The model accounts for the main processes determining both the population densities of the first ten states of the hydrogen atom and the densities of the positive hydrogen ions H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +}. In the calculations, the electron density and electron temperature are varied whereas the atomic and molecular temperatures are included as experimentally obtained external parameters. The ratio of the H{sub α} to H{sub β} line intensities is calculated from the numerical results for the excited state population densities, obtained as a solution of the set of the steady-state rate balance equations. The comparison of measured and theoretically obtained ratios of line intensities yields the values of the electron density and temperature as well as of the degree of dissociation, i.e., of the parameters which have a crucial role for the volume production of the negative ions.

A drift-ordered short mean-free path description of a partially ionized magnetized plasma

International Nuclear Information System (INIS)

Simakov, Andrei N

2009-01-01

Neutral particles that are present at the edge of plasma magnetic confinement devices can play an important role in energy and momentum transport, and their effects should be accounted for. This work uses the drift ordering to derive a closed fluid description for a collisional, magnetized, partially ionized plasma. Charge-exchange, ionization and recombination processes are taken into account. It is assumed that electron distribution function is unaffected by atomic processes, so that electron-ion momentum and energy exchange are described by the usual expressions for a fully ionized plasma, and that neutral-neutral collisions are unimportant. The collisional fluid equations derived herein generalize the drift-ordered description of a fully ionized collisional plasma (Catto P J et al 2004 Phys. Plasmas 11 90), agree with the MHD-ordered description of a partially ionized plasma (Helander P et al 1994 Phys. Plasmas 1 3174) in the large-flow limit and can be used to describe both turbulent and collisional behavior of a partially ionized plasma.

Optically thick model for radiative and collisional effects in nonequilibrium argon plasma flows in a circular tube

International Nuclear Information System (INIS)

Shirai, Hiroyuki; Tabei, Katsuine; Koaizawa, Hisashi.

1984-01-01

Experimental and theoretical studies were made to gain a deeper understanding of the radiative properties of nonequilibrium argon plasma flows in a circular tube. The self-absorption effects were taken into account as rigorously as possible. Experimentally, the radial profiles of the population densities of argon atoms at the excited 4s, 4p, 5p, and 5d levels were obtained from the lateral distributions of the absolute intensities of ArI spectral lines originating from these levels. On the other hand, theoretical profiles of the population densities for the same levels were calculated based on the optically thick model for collisional and radiative processes proposed by Bates et al. and experimentally measured atom temperature, electron temperature, electron density and gas pressure. Comparison of the experimental and theoretical results showed a reasonably good agreement and the importance of the self-absorption effects. (author)

Using Three-Body Recombination to Extract Electron Temperatures of Ultracold Plasmas

International Nuclear Information System (INIS)

Fletcher, R. S.; Zhang, X. L.; Rolston, S. L.

2007-01-01

Three-body recombination, an important collisional process in plasmas, increases dramatically at low electron temperatures, with an accepted scaling of T e -9/2 . We measure three-body recombination in an ultracold neutral xenon plasma by detecting recombination-created Rydberg atoms using a microwave-ionization technique. With the accepted theory (expected to be applicable for weakly coupled plasmas) and our measured rates, we extract the plasma temperatures, which are in reasonable agreement with previous measurements early in the plasma lifetime. The resulting electron temperatures indicate that the plasma continues to cool to temperatures below 1 K

Collisionality dependent transport in TCV SOL plasmas

DEFF Research Database (Denmark)

Garcia, Odd Erik; Pitts, R.A.; Horacek, J.

2007-01-01

Results are presented from probe measurements in the low field side scrape-off layer (SOL) region of TCV during plasma current scan experiments. It is shown that with decreasing plasma current the radial particle density profile becomes broader and the fluctuation levels and turbulence driven...... radial particle flux increase. In the far SOL the fluctuations exhibit a high degree of statistical similarity and the particle density and flux at the wall radius scale inversely with the plasma current. Together with previous TCV density scan experiments, this indicates that plasma fluctuations...

Soft X-Ray amplification in laser plasmas

International Nuclear Information System (INIS)

Louis-Jacquet, M.

1988-01-01

The principles, experiments and theoretical models of soft x-ray, amplification, produced in laser plasmas, are studied. In the discussion of the principles, the laser plasma medium, the definition of the gain, the population inversions, saturation and superradiance are described. The results concerning recombination and collisional excitation experiments, as well as experimental devices are shown. A complete physical simulation to design and interpret x-ray laser experiments is given. Applications of x-ray lasers in grating production techniques, in contact microscopy and holography are considered

Collisional-radiative model for the visible spectrum of W{sup 26+} ions

Energy Technology Data Exchange (ETDEWEB)

Ding, Xiaobin, E-mail: dingxb@nwnu.edu.cn [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu, Jiaxin [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Koike, Fumihiro [Department of Physics, Sophia University, Tokyo, 102-8554 (Japan); Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Nakamura, Nobuyuki [Institute for Laser Science, The University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Dong, Chenzhong [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

2016-02-22

Plasma diagnostics in magnetic confinement fusion plasmas by using visible spectrum strongly depends on the knowledge of fundamental atomic properties. A detailed collisional-radiative model of W{sup 26+} ions has been constructed by considering radiative and electron excitation processes, in which the necessary atomic data had been calculated by relativistic configuration interaction method with the implementation of Flexible Atomic Code. The visible spectrum observed at an electron beam ion trap (EBIT) in Shanghai in the range of 332 nm to 392 nm was reproduced by present calculations. Some transition pairs of which the intensity ratio is sensitive to the electron density were selected as potential candidates of plasma diagnostics. Their electron density dependence is theoretically evaluated for the cases of EBIT plasmas and magnetic confinement fusion plasmas.

How plasmas dissipate: cascade and the production of internal energy and entropy in weakly collisional plasma turbulence

Science.gov (United States)

Matthaeus, W. H.; Yang, Y.; Servidio, S.; Parashar, T.; Chasapis, A.; Roytershteyn, V.

2017-12-01

Turbulence cascade transfers energy from large scale to small scale but what happens once kinetic scales are reached? In a collisional medium, viscosity and resistivity remove fluctuation energy in favor of heat. In the weakly collisional solar wind, (or corona, m-sheath, etc.), the sequence of events must be different. Heating occurs, but through what mechanisms? In standard approaches, dissipation occurs though linear wave modes or instabilities and one seeks to identify them. A complementary view is that cascade leads to several channels of energy conversion, interchange and spatial rearrangement that collectively leads to production of internal energy. Channels may be described using compressible MHD & multispecies Vlasov Maxwell formulations. Key steps are: Conservative rearrangement of energy in space; Parallel incompressible and compressible cascades - conservative rearrangment in scale; electromagnetic work on particles that drives flows, both macroscopic and microscopic; and pressure-stress interactions, both compressive and shear-like, that produces internal energy. Examples given from MHD, PIC simulations and MMS observations. A more subtle issue is how entropy is related to this degeneration (or, "dissipation") of macroscopic, fluid-scale fluctuations. We discuss this in terms of Boltzmann and thermodynamic entropies, and velocity space effects of collisions.

ADAS tools for collisional-radiative modelling of molecules

Science.gov (United States)

Guzmán, F.; O'Mullane, M.; Summers, H. P.

2013-07-01

New theoretical and computational tools for molecular collisional-radiative models are presented. An application to the hydrogen molecule system has been made. At the same time, a structured database has been created where fundamental cross sections and rates for individual processes as well as derived data (effective coefficients) are stored. Relative populations for the vibrational states of the ground electronic state of H2 are presented and this vibronic resolution model is compared electronic resolution where vibronic transitions are summed over vibrational sub-states. Some new reaction rates are calculated by means of the impact parameter approximation. Computational tools have been developed to automate process and simplify the data assembly. Effective (collisional-radiative) rate coefficients versus temperature and density are presented.

Experimental study and numerical simulations of the spectral properties of XUV lasers pumped by collisional excitation

International Nuclear Information System (INIS)

Meng, L.

2012-01-01

Improving the knowledge of the spectral and temporal properties of plasma-based XUV lasers is an important issue for the ongoing development of these sources towards significantly higher peak power. The spectral properties of the XUV laser line actually control several physical quantities that are important for applications, such as the minimum duration that can be achieved (Fourier-transform limit). The shortest duration experimentally achieved to-date is ∼1 picosecond. The demonstrated technique of seeding XUV laser plasmas with a coherent femtosecond pulse of high-order harmonic radiation opens new and promising prospects to reduce the duration to a few 100 fs, provided that the gain bandwidth can be kept large enough.XUV lasers pumped by collisional excitation of Ni-like and Ne-like ions have been developed worldwide in hot plasmas created either by fast electrical discharge, or by various types of high-power lasers. This leads to a variety of XUV laser sources with distinct output properties, but also markedly different plasma parameters (density, temperature) in the amplification zone. Hence different spectral properties are expected. The purpose of our work was then to investigate the spectral behaviour of the different types of existing collisional excitation XUV lasers, and to evaluate their potential to support amplification of pulses with duration below 1 ps in a seeded mode.The spectral characterization of plasma-based XUV lasers is challenging because the extremely narrow bandwidth (typically Δλ/λ ∼10 -5 ) lies beyond the resolution limit of existing spectrometers in this spectral range. In our work the narrow linewidth was resolved using a wavefront-division interferometer specifically designed to measure temporal coherence, from which the spectral linewidth is inferred. We have characterized three types of collisional XUV lasers, developed in three different laboratories: transient pumping in Ni-like Mo, capillary discharge pumping in Ne

Maxima and minima of the orientation phenomena for direct 1s→2p+-1 electron-ion collisional excitations in weakly coupled plasmas

International Nuclear Information System (INIS)

Yoon Jung-Sik; Jung Young-Dae

1999-01-01

Orientation phenomena for direct 1s→2p +-1 electron-ion collisional excitations in weakly coupled plasma are investigated using the semiclassical trajectory method including the close-encounter effects. In weakly coupled plasmas, the electron-ion interaction potential is given by the classical nonspherical Debye-Hueckel model. The semiclassical screened hyperbolic-orbit trajectory method is applied to describe the motion of the projectile electron in order to investigate the variation of the orientation parameter as a function of the impact parameter, projectile energy, and Debye length. A comparison is also given for the hyperbolic-orbit and straight-line trajectory methods. The results show that the orientation parameters obtained by the hyperbolic-orbit trajectory method have maxima and minima for small impact parameter regions. In other words, there are complete 1s→2p +1 (maxima) and complete 1s→2p -1 (minima) transitions for certain impact parameters. These maxima cannot be found using the straight-line trajectory method. The variation of the propensity of the 1s→2p -1 transitions due to the plasma screening effects on the atomic wave functions is also discussed

Plasma processing: Technologies and applications

International Nuclear Information System (INIS)

Naddaf, M.; Saloum, S.

2005-01-01

This study aims to present the fundamentals of physics of plasmas, methods of generation, diagnostics, and applications for processing of materials. The first chapter defines plasma in general as well as its main parameters, the most important differential equations in plasma physics, and classifies the types of plasmas. the various methods and techniques to create and sustain plasma are presented in the second chapter. Chapter 3 focuses on plasma diagnostic methods and tools. While chapter 4 deals with applications of plasma processing such as; surface modification of materials, plasma ashing and etching, plasma cutting, and the environmental applications of plasma. Plasma polymerization and its various applications have been presented in more details in the last chapter. (Author)

Analysis of plasma instabilities and verification of the BOUT code for the Large Plasma Device

International Nuclear Information System (INIS)

Popovich, P.; Carter, T. A.; Friedman, B.; Umansky, M. V.

2010-01-01

The properties of linear instabilities in the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] are studied both through analytic calculations and solving numerically a system of linearized collisional plasma fluid equations using the three-dimensional fluid code BOUT[M. Umansky et al., Contrib. Plasma Phys. 180, 887 (2009)], which has been successfully modified to treat cylindrical geometry. Instability drive from plasma pressure gradients and flows is considered, focusing on resistive drift waves and the Kelvin-Helmholtz and rotational interchange instabilities. A general linear dispersion relation for partially ionized collisional plasmas including these modes is derived and analyzed. For Large Plasma Device relevant profiles including strongly driven flows, it is found that all three modes can have comparable growth rates and frequencies. Detailed comparison with solutions of the analytic dispersion relation demonstrates that BOUT accurately reproduces all characteristics of linear modes in this system.

Plasma flow healing of magnetic islands in stellarators

International Nuclear Information System (INIS)

Hegna, C. C.

2012-01-01

Recent experiments from the large helical device (LHD) demonstrate a correlation between the “healing” of vacuum magnetic islands in stellarators and changes in the plasma flow. A model explaining this phenomenon is developed based on self-consistent torque balance and island evolution equations. In conventional stellarators, neoclassical flow damping physics plays an important role in establishing the flow profiles. The balance of neoclassical damping and cross-field viscosity produces a radial boundary layer for the plasma rotation profile outside the separatrix of a locked magnetic island. The width of this boundary layer decreases as the plasma becomes less collisional. Associated with these flow effects are plasma currents flowing in the island region that attempt to suppress island formation. These currents are enhanced as the collisionality drops making magnetic island healing occur more readily in high temperature conventional stellarators. The analytic theory produces a critical β for healing that scales monotonically with collisionality and is in qualitative agreement with LHD observations.

Plasma transport near material boundaries

International Nuclear Information System (INIS)

Singer, C.E.

1985-06-01

The fluid theory of two-dimensional (2-d) plasma transport in axisymmetric devices is reviewed. The forces which produce flow across the magnetic field in a collisional plasma are described. These flows may lead to up-down asymmetries in the poloidal rotation and radial fluxes. Emphasis is placed on understanding the conditions under which the known 2-d plasma fluid equations provide a valid description of these processes. Attempts to extend the fluid treatment to less collisional, turbulent plasmas are discussed. A reduction to the 1-d fluid equations used in many computer simulations is possible when sources or boundary conditions provide a large enough radial scale length. The complete 1-d fluid equations are given in the text, and 2-d fluid equations are given in the Appendix

Wavelength scaling of laser plasma coupling

International Nuclear Information System (INIS)

Kruer, W.L.

1983-01-01

The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized

Neoclassical transport including collisional nonlinearity.

Science.gov (United States)

Candy, J; Belli, E A

2011-06-10

In the standard δf theory of neoclassical transport, the zeroth-order (Maxwellian) solution is obtained analytically via the solution of a nonlinear equation. The first-order correction δf is subsequently computed as the solution of a linear, inhomogeneous equation that includes the linearized Fokker-Planck collision operator. This equation admits analytic solutions only in extreme asymptotic limits (banana, plateau, Pfirsch-Schlüter), and so must be solved numerically for realistic plasma parameters. Recently, numerical codes have appeared which attempt to compute the total distribution f more accurately than in the standard ordering by retaining some nonlinear terms related to finite-orbit width, while simultaneously reusing some form of the linearized collision operator. In this work we show that higher-order corrections to the distribution function may be unphysical if collisional nonlinearities are ignored.

Improving a radiative plus collisional energy loss model for application to RHIC and LHC

International Nuclear Information System (INIS)

Wicks, Simon; Gyulassy, Miklos

2007-01-01

With the QGP opacity computed perturbatively and with the global entropy constraints imposed by the observed dN ch /dy ∼ 1000, radiative energy loss alone cannot account for the observed suppression of single non-photonic electrons. Collisional energy loss is comparable in magnitude to radiative loss for both light and heavy jets. Two aspects that significantly affect the collisional energy loss are examined: the role of fluctuations and the effect of introducing a running QCD coupling as opposed to the fixed α s = 0.3 used previously

Weak turbulence theory for beam-plasma interaction

Science.gov (United States)

Yoon, Peter H.

2018-01-01

The kinetic theory of weak plasma turbulence, of which Ronald C. Davidson was an important early pioneer [R. C. Davidson, Methods in Nonlinear Plasma Theory, (Academic Press, New York, 1972)], is a venerable and valid theory that may be applicable to a large number of problems in both laboratory and space plasmas. This paper applies the weak turbulence theory to the problem of gentle beam-plasma interaction and Langmuir turbulence. It is shown that the beam-plasma interaction undergoes various stages of physical processes starting from linear instability, to quasilinear saturation, to mode coupling that takes place after the quasilinear stage, followed by a state of quasi-static "turbulent equilibrium." The long term quasi-equilibrium stage is eventually perturbed by binary collisional effects in order to bring the plasma to a thermodynamic equilibrium with increased entropy.

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.

Maxwell Prize Talk: Scaling Laws for the Dynamical Plasma Phenomena

Science.gov (United States)

Ryutov, Livermore, Ca 94550, Usa, D. D.

2017-10-01

The scaling and similarity technique is a powerful tool for developing and testing reduced models of complex phenomena, including plasma phenomena. The technique has been successfully used in identifying appropriate simplified models of transport in quasistationary plasmas. In this talk, the similarity and scaling arguments will be applied to highly dynamical systems, in which temporal evolution of the plasma leads to a significant change of plasma dimensions, shapes, densities, and other parameters with respect to initial state. The scaling and similarity techniques for dynamical plasma systems will be presented as a set of case studies of problems from various domains of the plasma physics, beginning with collisonless plasmas, through intermediate collisionalities, to highly collisional plasmas describable by the single-fluid MHD. Basic concepts of the similarity theory will be introduced along the way. Among the results discussed are: self-similarity of Langmuir turbulence driven by a hot electron cloud expanding into a cold background plasma; generation of particle beams in disrupting pinches; interference between collisionless and collisional phenomena in the shock physics; similarity for liner-imploded plasmas; MHD similarities with an emphasis on the effect of small-scale (turbulent) structures on global dynamics. Relations between astrophysical phenomena and scaled laboratory experiments will be discussed.

Inductively coupled plasma mass spectrometry with hexapole collision cell: figures of merit and applications

Energy Technology Data Exchange (ETDEWEB)

Boulyga, S.F. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen]|[Radiation Physics and Chemistry Problems Inst., Minsk (Belarus); Becker, J.S. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen

2000-11-01

The use of gas-filled multipole collision cells represents important progress in ICP-MS instrumentation. It enables an increase in element sensitivity based on the improvement of ion transmission efficiency from near thermalization and collisional focusing of ions. In addition, gas-phase ion-molecule chemistry can be applied in order to reduce mass spectral interferences via charge transfer reaction of interfering ions with reaction gas or via fragmentation of interfering molecular ions by collision-induced dissociation. The application of a hexapole collision cell in quadrupole based ICP-MS (HEX-ICP-QMS) was studied systematically in order to characterize the analytical figures of merit of this approach. Additionally, the performance of different solution introduction systems as well as an inductively coupled plasma shielded torch was studied for use with HEX-ICP-QMS. (orig.)

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.

The effect of plasma collisionality on pedestal current density formation in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Thomas, D M; Leonard, A W; Osborne, T H; Groebner, R J; West, W P; Burrell, K H [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)

2006-05-15

The evolution and performance limits for the pedestal in H-mode are dependent on the two main drive terms for instability: namely the edge pressure gradient and the edge current density. These terms are naturally coupled though neoclassical (Pfirsch-Schluter and bootstrap) effects. On DIII-D, local measurements of the edge current density are made using an injected lithium beam in conjunction with Zeeman polarimetry and compared with pressure profile measurements made with other diagnostics. These measurements have confirmed the close spatial and temporal correlation that exists between the measured current density and the edge pressure in H- and QH-mode pedestals, where substantial pressure gradients exist. In the present work we examine the changes in the measured edge current for DIII-D pedestals which have a range of values for the ion and electron collisionalities {l_brace}{upsilon}{sub i}*,{upsilon}{sub e}*{r_brace} due to fuelling effects. Such changes in the collisionality in the edge are expected to significantly alter the level of the bootstrap current from the value predicted from the collisionless limit and therefore should correspondingly alter the pedestal stability limits. We find a clear decrease in measured current as {nu} increases, even for discharges having similar edge pressure gradients.

Jeans instability of inhomogeneous dusty plasma with polarization force, ionization and recombination

International Nuclear Information System (INIS)

Jain, Shweta; Sharma, Prerana; Chhajlani, R K

2017-01-01

The self-gravitational Jeans instability has been studied in dusty plasma containing significant background of neutral pressure and recombination of ions and electrons on the dust surface. The full dynamics of charged dust grains, ions and neutral species are employed considering the electrons as Maxwellian. We have derived the general dispersion relation for collisional dusty plasma with ionization, recombination and polarization force. The general dispersion relation describes the effects of considered parameters which are solved in different dusty plasma situations. Further, the dispersion relation is solved numerically. The present work is applicable to understand the structure formation of interstellar molecular clouds in astrophysical plasma. (paper)

Jeans instability of inhomogeneous dusty plasma with polarization force, ionization and recombination

Science.gov (United States)

Jain, Shweta; Sharma, Prerana; Chhajlani, R. K.

2017-05-01

The self-gravitational Jeans instability has been studied in dusty plasma containing significant background of neutral pressure and recombination of ions and electrons on the dust surface. The full dynamics of charged dust grains, ions and neutral species are employed considering the electrons as Maxwellian. We have derived the general dispersion relation for collisional dusty plasma with ionization, recombination and polarization force. The general dispersion relation describes the effects of considered parameters which are solved in different dusty plasma situations. Further, the dispersion relation is solved numerically. The present work is applicable to understand the structure formation of interstellar molecular clouds in astrophysical plasma.

Collisional drag may lead to disappearance of wave-breaking phenomenon of lower hybrid oscillations

International Nuclear Information System (INIS)

Maity, Chandan; Chakrabarti, Nikhil

2013-01-01

The inhomogeneity in the magnetic field in a cold electron-ion non-dissipative homogeneous plasma leads to the breaking of lower hybrid modes via phase mixing phenomenon [Maity et al. Phys. Plasmas 19, 102302 (2012)]. In this work, we show that an inclusion of collisional drag force in fluid equations may lead to the disappearance of the wave-breaking phenomenon of lower hybrid oscillations. The nonlinear analysis in Lagrangian variables provides an expression for a critical value of damping rate, above which spikes in the plasma density profile may disappear. The critical damping rate depends on the perturbation and magnetic field inhomogeneity amplitudes as well as the ratio of the magnetic field inhomogeneity and perturbation scale lengths.

SO-FDTD method and its application to the calculation of electromagnetic wave reflection coefficients of plasma

International Nuclear Information System (INIS)

Yang Hongwei; Nanjing Agricultural Univ., Nanjing; Chen Rushan; Zhang Yun

2006-01-01

The dielectric property of dispersive media is written as rational polynomial function, the relation between D and E is derived in time domain. It is named shift operator FDTD (SO-FDTD) method. The high accuracy and efficiency of this method is confirmed by computing the reflection coefficients of electromagnetic waves by a collisional plasma slab. The reflection coefficients between plasma and the atmosphere or vacuum can be calculated by using the SO-FDTD method. The result is that the reflection coefficients are affected by plasma thickness, electron numerical density, the distributing orderliness of electron density, and incidence wave frequency. (authors)

High density turbulent plasma processes from a shock tube

International Nuclear Information System (INIS)

Oyedeji, O.; Johnson, J.A. III

1991-01-01

We have finished the first stages of our experimental and theoretical investigations on models for energy and momentum transport and for photon-particle collision processes in a turbulent quasi-stationary high density plasma. The system is explored by beginning to determine the turbulence phenomenology associated with an ionizing shock wave. The theoretical underpinnings are explored for phonon particle collisions by determining the collisional redistribution function, using Lioville Space Green's Function, which will characterize the inelastic scattering of the radiation from one frequency to another. We have observed that a weak magnetic field tends to increase the apparent random-like behaviors in a collisional turbulent plasma. On the theoretical side, we have been able to achieve a form for the collisional redistribution function. It remains to apply these concepts to a stationary turbulent plasma in the reflected ionizing shock wave and to exercise the implications of evaluations of the collisional redistribution function for such a system when it is probed by a strong radiation source. These results are discussed in detail in the publications, which have resulted from the this effort, cited at the end of the report

Analysis of time- and space-resolved Na-, Ne-, and F-like emission from a laser-produced bromine plasma

International Nuclear Information System (INIS)

Goldstein, W.H.; Young, B.K.F.; Osterheld, A.L.; Stewart, R.E.; Walling, R.S.; Bar-Shalom, A.

1991-01-01

Advances in the efficiency and accuracy of computational atomic physics and collisional radiative modeling promise to place the analysis and diagnostic application of L-shell emission on a par with the simpler K-shell regime. Coincident improvements in spectroscopic plasma measurements yield optically thin emission spectra from small, homogeneous regions of plasma, localized both in space and time. Together, these developments can severely test models for high-density, high-temperature plasma formation and evolution, and non-LTE atomic kinetics. In this paper we present highly resolved measurements of n=3 to n=2 X-ray line emission from a laser-produced bromine micro plasma. The emission is both space- and time-resolved, allowing us to apply simple, steady-state, 0-dimensional spectroscopic models to the analysis. These relativistic, multi-configurational, distorted wave collisional-radiative models were created using the HULLAC atomic physics package. Using these models, we have analyzed the F-like, Ne-like and Na-like (satellite) spectra with respect to temperature, density and charge-state distribution. This procedure leads to a full characterization of the plasma conditions. 9 refs., 3 figs

Interaction of the electromagnetic waves and non-magnetized plasmas

International Nuclear Information System (INIS)

Sun Aiping; Qiu Xiaoming; Dong Yuying; Li Liqiong

2002-01-01

The propagation of electromagnetic waves with 0.5 - 10 GHz in a non-magnetized collisional plasma slab is studied numerically. The change in the absorbed power, reflected power and transmitted power of the electromagnetic wave with collisional frequency of electrons and neutral atoms in plasma from 0.1 - 10 GHz, is calculated, in the condition of the uniform plasma with density of 10 10 or 10 11 cm -3 and depth of 10 cm, and the non-uniform plasma with density distribution of n = n 0 exp[2(z/d-1)] and depth of 10 cm, respectively. The results show that the absorbed power in either uniform or non-uniform plasma is large when the plasma density is large and collision frequency is high, and the peak value is 90%

Quasi-linear landau kinetic equations for magnetized plasmas: compact propagator formalism, rotation matrices and interaction

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

Quasi-linear landau kinetic equations for magnetized plasmas: compact propagator formalism, rotation matrices and interaction

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.

Collisional pumping for the production of intense spin-polarized neutral beams: target considerations. Revision

International Nuclear Information System (INIS)

Stearns, J.W.; Burrell, C.F.; Kaplan, S.N.; Pyle, R.V.; Ruby, L.; Schlachter, A.S.

1985-04-01

Polarized beams at intensity levels heretofore not considered feasible have recently been proposed for heating and fueling fusion plasmas. Polarized-beam fueling could increase fusion rates by 50% as well as allow control of the directionality of the fusion products. A process which we have recently described, and called collisional pumping, promises to produce beams of polarized ions vastly more intense than producible by current methods

Non equilibrium atomic processes and plasma spectroscopy

International Nuclear Information System (INIS)

Kato, Takako

2003-01-01

Along with the technical progress in plasma spectroscopy, non equilibrium ionization processes have been recently observed. We study non local thermodynamic equilibrium and non ionization equilibrium for various kinds of plasmas. Specifically we discuss non equilibrium atomic processes in magnetically confined plasmas, solar flares and laser produced plasmas using a collisional radiative model based on plasma spectroscopic data. (author)

Theoretical plasma physics. Final report

International Nuclear Information System (INIS)

Vahala, G.; Tracy, E.

1996-04-01

During the past year, the authors have concentrated on (1) divertor physics, (2) thermo-lattice Boltzmann (TLBE) approach to turbulence, and (3) phase space techniques in gyro-resonance problems in collaboration with Dieter Sigmar (MIT), Sergei Krasheninnikov (MIT), Linda Vahala (ODU), Joseph Morrison (AS and M/NASA-Langley), Pavol Pavlo and Josef Preinhaelter (institute of Plasma Physics, Czech Academy of Sciences) and Allan Kaufman (LBL/U.C.Berkeley). Using a 2-equation compressible closure model with a 2D mean flow, the authors are investigating the effects of 3D neutral turbulence on reducing the heat load to the divertor plate by various toroidal cavity geometries. These studies are being extended to examine 3D mean flows. Thermal Lattice Boltzmann (TLBE) methods are being investigated to handle 3D turbulent flows in nontrivial geometries. It is planned to couple the TLBE collisional regime to the weakly collisional regime and so be able to tackle divertor physics. In the application of phase space techniques to minority-ion RF heating, resonance heating is treated as a multi-stage process. A generalization of the Case-van Kampen analysis is presented for multi-dimensional non-uniform plasmas. Effects such as particle trapping and the ray propagation dynamics in tokamak geometry can now be handled using Weyl calculus

Nonadiabatic effects in inelastic collisional processes

International Nuclear Information System (INIS)

Belyaev, Andrey K

2009-01-01

The standard adiabatic Born-Oppenheimer approach to inelastic collisional processes is revised. It is shown that the widely used standard interpretation of this approach has fundamental limitations leading to physical artefacts or to uncertainties in numerical calculations due to neglecting the electron translation problem. It is demonstrated that the Born-Oppenheimer approach itself does not have such limitations. The particular full quantum solution of the electron translation problem within the Born-Oppenheimer approach by means of the reprojection procedure is discussed in the paper together with the practical applications.

Collisional Transport in a Low Aspect Ratio Tokamak -- Beyond the Drift Kinetic Formalism

International Nuclear Information System (INIS)

Gates, D.A.; White, R.B.

2004-01-01

Calculations of collisional thermal and particle diffusivities in toroidal magnetic plasma confinement devices order the toroidal gyroradius to be small relative to the poloidal gyroradius. This ordering is central to what is usually referred to as neoclassical transport theory. This ordering is incorrect at low aspect ratio, where it can often be the case that the toroidal gyroradius is larger than the poloidal gyroradius. We calculate the correction to the particle and thermal diffusivities at low aspect ratio by comparing the diffusivities as determined by a full orbit code (which we refer to as omni-classical diffusion) with those from a gyroaveraged orbit code (neoclassical diffusion). In typical low aspect ratio devices the omni-classical diffusion can be up to 2.5 times the calculated neoclassical value. We discuss the implications of this work on the analysis of collisional transport in low aspect ratio magnetic confinement experiments

Plasma sheath criterion in thermal electronegative plasmas

International Nuclear Information System (INIS)

Ghomi, Hamid; Khoramabadi, Mansour; Ghorannevis, Mahmod; Shukla, Padma Kant

2010-01-01

The sheath formation criterion in electronegative plasma is examined. By using a multifluid model, it is shown that in a collisional sheath there will be upper as well as lower limits for the sheath velocity criterion. However, the parameters of the negative ions only affect the lower limit.

Theory of the scrape-off layer width in inner-wall limited tokamak plasmas

International Nuclear Information System (INIS)

Halpern, F.D.; Ricci, P.; Jolliet, S.; Loizu, J.; Mosetto, A.

2014-01-01

We develop a predictive theory applicable to the scrape-off layer (SOL) of inner-wall limited plasmas. Using the non-linear flattening of the pressure profile as a saturation mechanism for resistive ballooning modes, we are able to demonstrate and quantify the increase of the SOL width with plasma size, connection length, plasma β, and collisionality. Individual aspects of the theory, such as saturation physics, parallel dynamics, and system size scaling, are tested and verified using non-linear, 3D flux-driven SOL turbulence simulations. Altogether, very good agreement between theory and simulation is found. (paper)

Development of transient collisional excitation x-ray laser with ultra short-pulse laser

International Nuclear Information System (INIS)

Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Tanaka, Momoko; Sukegawa, Kouta; Nagashima, Keisuke; Kato, Yoshiaki

2001-01-01

We have observed lasing on Ne-like 3s-3p line from titanium (32.4 nm), Ni-like 4p-4d line from silver (13.9 nm) and tin (11.9 nm) with the transient collisional excitation (TCE) scheme that uses combination of a long pre-pulse (∼ns) and a short main pulse (∼ps). A gain coefficient of 23 cm -1 was measured for plasma length up to 4 mm with silver slab targets. We have also observed lasing on Ne-like and Ni-like lines with new TCE scheme that used pico-seconds laser pulse to generate plasma and observed strong improvement of x-ray laser gain coefficient. A gain coefficient of 14 cm -1 was measured for plasma length up to 6 mm with tin targets. (author)

Magnetic-flutter-induced pedestal plasma transport

International Nuclear Information System (INIS)

Callen, J.D.; Hegna, C.C.; Cole, A.J.

2013-01-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δB ρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δB ρ s induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δB ρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δB ρ /B 0 ) 2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an

Magnetic-flutter-induced pedestal plasma transport

Science.gov (United States)

Callen, J. D.; Hegna, C. C.; Cole, A. J.

2013-11-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δBρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δBρs induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δBρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δBρ/B0)2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an electron

Collisional properties of weakly bound heteronuclear dimers

NARCIS (Netherlands)

Marcelis, B.; Kokkelmans, S.J.J.M.F.; Shlyapnikov, G.V.; Petrov, D.S.

2008-01-01

We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating

Introduction to Plasma Physics

Science.gov (United States)

Gurnett, Donald A.; Bhattacharjee, Amitava

2017-03-01

Preface; 1. Introduction; 2. Characteristic parameters of a plasma; 3. Single particle motions; 4. Waves in a cold plasma; 5. Kinetic theory and the moment equations; 6. Magnetohydrodynamics; 7. MHD equilibria and stability; 8. Discontinuities and shock waves; 9. Electrostatic waves in a hot unmagnetized plasma; 10. Waves in a hot magnetized plasma; 11. Nonlinear effects; 12. Collisional processes; Appendix A. Symbols; Appendix B. Useful trigonometric identities; Appendix C. Vector differential operators; Appendix D. Vector calculus identities; Index.

Use of nonlocal helium microplasma for gas impurities detection by the collisional electron spectroscopy method

Energy Technology Data Exchange (ETDEWEB)

Kudryavtsev, Anatoly A., E-mail: akud@ak2138.spb.edu [St. Petersburg State University, 7-9 Universitetskaya nab., 199034 St. Petersburg (Russian Federation); Stefanova, Margarita S.; Pramatarov, Petko M. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee blvd., 1784 Sofia (Bulgaria)

2015-10-15

The collisional electron spectroscopy (CES) method, which lays the ground for a new field for analytical detection of gas impurities at high pressures, has been verified. The CES method enables the identification of gas impurities in the collisional mode of electron movement, where the advantages of nonlocal formation of the electron energy distribution function (EEDF) are fulfilled. Important features of dc negative glow microplasma and probe method for plasma diagnostics are applied. A new microplasma gas analyzer design is proposed. Admixtures of 0.2% Ar, 0.6% Kr, 0.1% N{sub 2}, and 0.05% CO{sub 2} are used as examples of atomic and molecular impurities to prove the possibility for detecting and identifying their presence in high pressure He plasma (50–250 Torr). The identification of the particles under analysis is made from the measurements of the high energy part of the EEDF, where maxima appear, resulting from the characteristic electrons released in Penning reactions of He metastable atoms with impurity particles. Considerable progress in the development of a novel miniature gas analyzer for chemical sensing in gas phase environments has been made.

Gyrokinetic-water-bag modeling of low-frequency instabilities in a laboratory magnetized plasma column

Science.gov (United States)

Gravier, E.; Klein, R.; Morel, P.; Besse, N.; Bertrand, P.

2008-12-01

A new model is presented, named collisional-gyro-water-bag (CGWB), which describes the collisional drift waves and ion-temperature-gradient (ITG) instabilities in a plasma column. This model is based on the kinetic gyro-water-bag approach recently developed [P. Morel et al., Phys. Plasmas 14, 112109 (2007)] to investigate ion-temperature-gradient modes. In CGWB electron-neutral collisions have been introduced and are now taken into account. The model has been validated by comparing CGWB linear analysis with other models previously proposed and experimental results as well. Kinetic effects on collisional drift waves are investigated, resulting in a less effective growth rate, and the transition from collisional drift waves to ITG instability depending on the ion temperature gradient is studied.

Expansion of Collisional Radiative Model for Helium line ratio spectroscopy

Science.gov (United States)

Cinquegrani, David; Cooper, Chris; Forest, Cary; Milhone, Jason; Munoz-Borges, Jorge; Schmitz, Oliver; Unterberg, Ezekial

2015-11-01

Helium line ratio spectroscopy is a powerful technique of active plasma edge spectroscopy. It enables reconstruction of plasma edge parameters like electron density and temperature by use of suitable Collisional Radiative Models (CRM). An established approach is successful at moderate plasma densities (~1018m-3 range) and temperature (30-300eV), taking recombination and charge exchange to be negligible. The goal of this work is to experimentally explore limitations of this approach to CRM. For basic validation the Madison Plasma Dynamo eXperiment (MPDX) will be used. MPDX offers a very uniform plasma and spherical symmetry at low temperature (5-20 eV) and low density (1016 -1017m-3) . Initial data from MPDX shows a deviation in CRM results when compared to Langmuir probe data. This discrepancy points to the importance of recombination effects. The validated model is applied to first time measurement of electron density and temperature in front of an ICRH antenna at the TEXTOR tokamak. These measurements are important to understand RF coupling and PMI physics at the antenna limiters. Work supported in part by start up funds of the Department of Engineering Physics at the UW - Madison, USA and NSF CAREER award PHY-1455210.

Evolution of a Gaussian laser beam in warm collisional magnetoplasma

Energy Technology Data Exchange (ETDEWEB)

Jafari, M. J.; Jafari Milani, M. R., E-mail: mrj.milani@gmail.com [Plasma Physics Research School, NSTRI, Tehran (Iran, Islamic Republic of); Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)

2016-07-15

In this paper, the spatial evolution of an intense circularly polarized Gaussian laser beam propagated through a warm plasma is investigated, taking into account the ponderomotive force, Ohmic heating, external magnetic field, and collisional effects. Using the momentum transfer and energy equations, both modified electron temperature and electron density in plasma are obtained. By introducing the complex dielectric permittivity of warm magnetized plasma and using the complex eikonal function, coupled differential equations for beam width parameter are established and solved numerically. The effects of polarization state of laser and magnetic field on the laser spot size evolution are studied. It is observed that in case of the right-handed polarization, an increase in the value of external magnetic field causes an increase in the strength of the self-focusing, especially in the higher values, and consequently, the self-focusing occurs in shorter distance of propagation. Moreover, the results demonstrate the existence of laser intensity and electron temperature ranges where self-focusing can occur, while the beam diverges outside of these regions; meanwhile, in these intervals, there exists a turning point for each of intensity and temperature in which the self-focusing process has its strongest strength. Finally, it is found that the self-focusing effect can be enhanced by increasing the plasma frequency (plasma density).

Theory of dielectronic recombination and plasma effects

International Nuclear Information System (INIS)

Yukap Hahn

2000-01-01

Current status of the various theoretical approaches to calculation of dielectronic recombination rates is summarized, with emphasis on the available data base and on the plasma effects of both the plasma ion (and external) fields and plasma electron collisional effects which seriously affect the rates and complicate compilation of data. (author)

Screening length in dusty plasma crystals

International Nuclear Information System (INIS)

Nikolaev, V S; Timofeev, A V

2016-01-01

Particles interaction and value of the screening length in dusty plasma systems are of great interest in dusty plasma area. Three inter-particle potentials (Debye potential, Gurevich potential and interaction potential in the weakly collisional regime) are used to solve equilibrium equations for two dusty particles suspended in a parabolic trap. The inter-particle distance dependence on screening length, trap parameter and particle charge is obtained. The functional form of inter-particle distance dependence on ion temperature is investigated and compared with experimental data at 200-300 K in order to test used potentials applicability to dusty plasma systems at room temperatures. The preference is given to the Yukawa-type potential including effective values of particle charge and screening length. The estimated effective value of the screening length is 5-15 times larger than the Debye length. (paper)

Accelerated Recombination in Cold Dense Plasmas with Metastable Ions due to Resonant Deexcitation

International Nuclear Information System (INIS)

Ralchenko, Yu.V.; Maron, M.

2001-01-01

In a recombining plasma the metastable states are known to accumulate population thereby slowing down the recombination process. We show that a proper account of the doubly-excited autoionizing states, populated through collisional 3-body recombination of metastable ions, results in a significant acceleration of recombination. 3-body recombination followed by collisional (de)excitations and autoionization effectively produces deexcitation via the following chain of elementary events: A fully time-dependent collisional-radiative (CR) modeling for stripped ions of carbon recombining in a cold dense plasma demonstrates an order of magnitude faster recombination of He-like ions. The CR model used in calculations is discussed in details

Nonlinear neoclassical transport in toroidal edge plasmas

International Nuclear Information System (INIS)

Fueloep, T.; Helander, P.

2001-01-01

In conventional neoclassical theory, the density and temperature gradients are not allowed to be as steep as frequently observed in the tokamak edge. In this paper the theory of neoclassical transport in a collisional, impure plasma is extended to allow for steeper profiles than normally assumed. The dynamics of highly charged impurity ions then becomes nonlinear, which affects the transport of all species. As earlier found in the banana regime, when the bulk plasma gradients are large the impurity ions undergo a poloidal redistribution, which reduces their parallel friction with the bulk ions and suppresses the neoclassical ion particle flux. The neoclassical confinement is thus improved in regions with large radial gradients. When the plasma is collisional and the gradients are large, the impurities accumulate on the inboard side of the torus

Plasma residual poloidal rotation in TCABR tokamak

International Nuclear Information System (INIS)

Severo, J.H.F.; Nascimento, I.C.; Tsypin, V.S.; Galvao, R.M.O.

2003-01-01

This paper reports the first measurement of the radial profiles of plasma poloidal and toroidal rotation performed on the TCABR tokamak for a collisional plasma (Pfirsch-Schluter regime), using Doppler shift of carbon spectral lines, measured with a high precision optical spectrometer. The results for poloidal rotation show a maximum velocity of (4.5±1.0)·10 3 m/s at r ∼ 2/3a, (a - limiter radius), in the direction of the diamagnetic electron drift. Within the error limits, reasonable agreement is obtained with calculations using the neoclassical theory for a collisional plasma, except near the plasma edge, as expected. For toroidal rotation, the radial profile shows that the velocity decreases from a counter-current value of (20 ± 1) · 10 3 m/s for the plasma core to a co-current value of (2.0 ± 1.0) · 10 3 m/s near the limiter. An agreement within a factor 2, for the plasma core rotation, is obtained with calculations using the model proposed by Kim, Diamond and Groebner. (author)

Diffusion and transport phenomena in a collisional magnetoplasma ...

Indian Academy of Sciences (India)

Boltzmann-transport equation is analytically solved for two-component magnetoplasma using Chapman-Enskog analysis to include collisional diffusion transport having anisotropies in both streaming velocity and temperature components. The modified collisional integrals are analytically solved with flux integrals and ...

IDENTIFYING COLLISIONAL FAMILIES IN THE KUIPER BELT

International Nuclear Information System (INIS)

Marcus, Robert A.; Ragozzine, Darin; Murray-Clay, Ruth A.; Holman, Matthew J.

2011-01-01

The identification and characterization of numerous collisional families-clusters of bodies with a common collisional origin-in the asteroid belt has added greatly to the understanding of asteroid belt formation and evolution. More recent study has also led to an appreciation of physical processes that had previously been neglected (e.g., the Yarkovsky effect). Collisions have certainly played an important role in the evolution of the Kuiper Belt as well, though only one collisional family has been identified in that region to date, around the dwarf planet Haumea. In this paper, we combine insights into collisional families from numerical simulations with the current observational constraints on the dynamical structure of the Kuiper Belt to investigate the ideal sizes and locations for identifying collisional families. We find that larger progenitors (r ∼ 500 km) result in more easily identifiable families, given the difficulty in identifying fragments of smaller progenitors in magnitude-limited surveys, despite their larger spread and less frequent occurrence. However, even these families do not stand out well from the background. Identifying families as statistical overdensities is much easier than characterizing families by distinguishing individual members from interlopers. Such identification seems promising, provided the background population is well known. In either case, families will also be much easier to study where the background population is small, i.e., at high inclinations. Overall, our results indicate that entirely different techniques for identifying families will be needed for the Kuiper Belt, and we provide some suggestions.

Field distribution of a source and energy absorption in an inhomogeneous magneto-active plasma

International Nuclear Information System (INIS)

Galushko, N.P.; Erokhin, N.S.; Moiseev, S.S.

1975-01-01

In the present paper the distribution of source fields in in a magnetoactive plasma is studied from the standpoint of the possibility of an effective SHF heating of an inhomogeneous plasma in both high (ωapproximatelyωsub(pe) and low (ωapproximatelyωsub(pi) frequency ranges, where ωsub(pe) and ωsub(pi) are the electron and ion plasma frequencies. The localization of the HF energy absorption regions in cold and hot plasma and the effect of plasma inhomogeneity and source dimensions on the absorption efficiency are investigated. The linear wave transformation in an inhomogeneous hot plasma is taken into consideration. Attention is paid to the difference between the region localization for collisional and non-collisional absorption. It has been shown that the HF energy dissipation in plasma particle collisions is localized in the region of thin jets going from the source; the radiation field has a sharp peak in this region. At the same time, non-collisional HF energy dissipation is spread over the plasma volume as a result of Cherenkov and cyclotron wave attenuation. The essential contribution to the source field from resonances due to standing wave excitation in an inhomogeneous plasma shell near the source is pointed out

Implicit multi-fluid simulation of interpenetrating plasmas

International Nuclear Information System (INIS)

Rambo, P.W.; Denavit, J.

1992-01-01

A one dimensional simulation code for interpenetrating multi-component plasmas is presented. Separate fluid equations for multiple species and the Poisson equation for the electric field are solved implicitly to allow stable accurate solutions over a wide range of the time scale parameters ω p Δt and ν c Δt (ω p is the plasma frequency, ν c a typical collision frequency and Δt the time step). In regions where ω p Δt c Δt p Δt >>1 and/or ν c Δt>>1, the ambipolar and/or diffusion models are recovered. In regions of low collisionality, particles may be created and deleted which are followed using particle and cell techniques combined with scatter and drag due to collisions with the fluids. Applications of this code to interpenetrating laser generated plasmas are presented

Laser enhancement of the collisional broadening of the 4713 and 3188 A lines in a helium plasma

International Nuclear Information System (INIS)

Pignolet, P.

1986-01-01

The enhancement of the electron collisional broadening of the 4s 3 S 1 and 4p 3 P 0 sub(2,1,0) levels in a helium glow discharge (nsub(e) = 10 13 -10 14 cm -3 ), induced by the non-resonant interaction of the 4s 3 S 1 and 4p 3 P 0 sub(2,1,0) levels with a CO 2 laser field, is reported. This extra broadening depends on the product of the electron density with the laser field amplitude and manifests itself on the 4713 and 3188 A linewidths. This effect results from the destruction, by electronic collisions, of the coherence induced by the laser field between the 4s 3 S 1 and 4p 3 P 0 sub(2,1,0) levels, and can be viewed as an electron-atom collisional fluorescence redistribution process at relatively large laser detuning. (author)

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

Parallel Transport with Sheath and Collisional Effects in Global Electrostatic Turbulent Transport in FRCs

Science.gov (United States)

Bao, Jian; Lau, Calvin; Kuley, Animesh; Lin, Zhihong; Fulton, Daniel; Tajima, Toshiki; Tri Alpha Energy, Inc. Team

2017-10-01

Collisional and turbulent transport in a field reversed configuration (FRC) is studied in global particle simulation by using GTC (gyrokinetic toroidal code). The global FRC geometry is incorporated in GTC by using a field-aligned mesh in cylindrical coordinates, which enables global simulation coupling core and scrape-off layer (SOL) across the separatrix. Furthermore, fully kinetic ions are implemented in GTC to treat magnetic-null point in FRC core. Both global simulation coupling core and SOL regions and independent SOL region simulation have been carried out to study turbulence. In this work, the ``logical sheath boundary condition'' is implemented to study parallel transport in the SOL. This method helps to relax time and spatial steps without resolving electron plasma frequency and Debye length, which enables turbulent transports simulation with sheath effects. We will study collisional and turbulent SOL parallel transport with mirror geometry and sheath boundary condition in C2-W divertor.

Simulation of an ITER-like dissipative divertor plasma with a combined edge plasma Navier-Stokes neutral model

International Nuclear Information System (INIS)

Knoll, D.A.; McHugh, P.R.; Krasheninnikov, S.I.; Sigmar, D.J.

1996-01-01

A combined edge plasma/Navier-Stokes neutral transport model is used to simulate dissipative divertor plasmas in the collisional limit for neutrals on a simplified two-dimensional slab geometry with ITER-like plasma conditions and scale lengths. The neutral model contains three momentum equations which are coupled to the plasma through ionization, recombination, and ion-neutral elastic collisions. The neutral transport coefficients are evaluated including both ion-neutral and neutral-neutral collisions. (orig.)

Collisional transport in a plasma with steep gradients

International Nuclear Information System (INIS)

Wang, W.; Okamoto, M.; Nakajima, N.; Murakami, S.

1999-06-01

The validity is given to the newly proposed two δf method for neoclassical transport calculation, which can be solve the drift kinetic equation considering effects of steep plasma gradients, large radial electric field, finite banana width, and an orbit topology near the axis. The new method is applied to the study of ion transport with steep plasma gradients. It is found that the ion thermal diffusivity decreases as the scale length of density gradient decreases, while the ion particle flux due to ion-ion self collisions increases with increasing gradient. (author)

Theoretical modeling of transport barriers in helical plasmas

International Nuclear Information System (INIS)

Toda, S.; Itoh, K.; Ohyabu, N.

2008-10-01

A unified transport modelling to explain electron Internal Transport Barriers (e-ITB) in helical plasmas and Internal Diffusion Barriers (IDB) observed in Large Helical Device (LHD) is proposed. The e-ITB can be predicted with the effect of zonal flows to obtain the e-ITB in the low collisional regime when the radial variation of the particle anomalous diffusivity is included. Transport analysis in this article can newly show that the particle fuelling induces the IDB formation when this unified transport modelling is used in the high collisional regime. The density limit for the IDB in helical plasmas is also examined including the effect of the radiation loss. (author)

Atomic data for beam-stimulated plasma spectroscopy in fusion plasmas

International Nuclear Information System (INIS)

Marchuk, O.; Biel, W.; Schlummer, T.; Ralchenko, Yu.; Schultz, D. R.

2013-01-01

Injection of high energy atoms into a confined plasma volume is an established diagnostic technique in fusion research. This method strongly depends on the quality of atomic data for charge-exchange recombination spectroscopy (CXRS), motional Stark effect (MSE) and beam-emission spectroscopy (BES). We present some examples of atomic data for CXRS and review the current status of collisional data for parabolic states of hydrogen atoms that are used for accurate MSE modeling. It is shown that the collisional data require knowledge of the excitation density matrix including the off-diagonal matrix elements. The new datasets for transitions between parabolic states are used in an extended collisional-radiative model. The ratios between the σ- and π-components and the beam-emission rate coefficients are calculated in a quasi-steady state approximation. Good agreement with the experimental data from JET is found which points out to strong deviations from the statistical distribution for magnetic sublevels

Damping of electron center-of-mass oscillation in ultracold plasmas

International Nuclear Information System (INIS)

Chen, Wei-Ting; Witte, Craig; Roberts, Jacob L.

2016-01-01

Applying a short electric field pulse to an ultracold plasma induces an electron plasma oscillation. This manifests itself as an oscillation of the electron center of mass around the ion center of mass in the ultracold plasma. In general, the oscillation can damp due to either collisionless or collisional mechanisms, or a combination of the both. To investigate the nature of oscillation damping in ultracold plasmas, we developed a molecular dynamics model of the ultracold plasma electrons. Through this model, we found that depending on the neutrality of the ultracold plasma and the size of an applied DC electric field, there are some parameter ranges where the damping is primarily collisional and some primarily collisionless. We conducted experiments to compare the measured damping rate with theory predictions and found them to be in good agreement. Extension of our measurements to different parameter ranges should enable studies for strong-coupling influence on electron-ion collision rates.

Local thermodynamic equilibrium in rapidly heated high energy density plasmas

International Nuclear Information System (INIS)

Aslanyan, V.; Tallents, G. J.

2014-01-01

Emission spectra and the dynamics of high energy density plasmas created by optical and Free Electron Lasers (FELs) depend on the populations of atomic levels. Calculations of plasma emission and ionization may be simplified by assuming Local Thermodynamic Equilibrium (LTE), where populations are given by the Saha-Boltzmann equation. LTE can be achieved at high densities when collisional processes are much more significant than radiative processes, but may not be valid if plasma conditions change rapidly. A collisional-radiative model has been used to calculate the times taken by carbon and iron plasmas to reach LTE at varying densities and heating rates. The effect of different energy deposition methods, as well as Ionization Potential Depression are explored. This work shows regimes in rapidly changing plasmas, such as those created by optical lasers and FELs, where the use of LTE is justified, because timescales for plasma changes are significantly longer than the times needed to achieve an LTE ionization balance

Atomic properties in hot plasmas from levels to superconfigurations

CERN Document Server

Bauche, Jacques; Peyrusse, Olivier

2015-01-01

This book is devoted to the calculation of hot-plasma properties which generally requires a huge number of atomic data. It is the first book that combines information on the details of the basic atomic physics and its application to atomic spectroscopy with the use of the relevant statistical approaches. Information like energy levels, radiative rates, collisional and radiative cross-sections, etc., must be included in equilibrium or non-equilibrium models in order to describe both the atomic-population kinetics and the radiative properties. From the very large number of levels and transitions involved in complex ions, some statistical (global) properties emerge. The book presents a coherent set of concepts and compact formulas suitable for tractable and accurate calculations. The topics addressed are: radiative emission and absorption, and a dozen of other collisional and radiative processes; transition arrays between level ensembles (configurations, superconfigurations); effective temperatures of configurat...

Study of emission process in hot, optically thin plasma: application to solar active regions

International Nuclear Information System (INIS)

Steenman-Clark, Lois.

1983-06-01

Analysis of soft X-ray got in hot and weak density plasmas, such as those in TOKAMAKS and in solar flares, needs a detailed knowledge of emission processes. In this work are presented spectroscopic diagnostics which can be deduced from such spectra analysis and results are applied to magnesium solar spectrum analysis. An important improvement is brought to collisional calculation corresponding to forbidden line populating. For this line, The relative importance of autoionizing states effect, called also resonance effect is studied [fr

Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

Energy Technology Data Exchange (ETDEWEB)

Bandyopadhyay, P. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)], E-mail: pintu@ipr.res.in; Prasad, G.; Sen, A.; Kaw, P.K. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

2007-09-03

The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO{sub 2} dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of {partial_derivative}{omega}/{partial_derivative}k<0 are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.

Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

International Nuclear Information System (INIS)

Bandyopadhyay, P.; Prasad, G.; Sen, A.; Kaw, P.K.

2007-01-01

The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO 2 dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of ∂ω/∂k<0 are identified as signatures of dust-dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects

Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

Science.gov (United States)

Bandyopadhyay, P.; Prasad, G.; Sen, A.; Kaw, P. K.

2007-09-01

The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and MnO2 dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of ∂ω/∂k<0 are identified as signatures of dust dust correlations. In the high collisional regime dust neutral collisions produce a similar effect and prevent an unambiguous identification of strong coupling effects.

Electrostatic fluctuations measured in low temperature helical plasmas with low collisionality

International Nuclear Information System (INIS)

Takeuchi, M.; Ikeda, R.; Ito, T.; Toi, K.; Suzuki, C.; Matsunaga, G.

2004-01-01

Electrostatic fluctuations have been measured by Langmuir probes from edge to core plasma region in low temperature helical plasmas which are produced by 2.45 GHz microwaves at very low field less than 0.1 T. The principal dimensionless parameters of the plasmas, that is, the normalized electron-ion collision frequency ν ei , and averaged plasma β φ and others are in the same range of them in high temperature plasmas, except the normalized gyro radius ρ s . The data on fluctuation characteristics from the dimensionally similar low temperature plasmas may give an important insight into the understanding of turbulent transport in high temperature plasmas. Dependences of fluctuation amplitudes on the radial electric field shear, ρ s and ν ei are investigated. Electrostatic fluctuations propagating in electron-diamagnetic drift direction have been observed in the plasma edge region and in ion-diamagnetic drift direction in the plasma core region. (authors)

Collisional damping of giant monopole and quadrupole resonances

International Nuclear Information System (INIS)

Yildirim, S.; Gokalp, A.; Yilmaz, O.; Ayik, S.

2001-01-01

Collisional damping widths of giant monopole and quadrupole excitations for 120 Sn and 208 Pb at zero and finite temperatures are calculated within Thomas-Fermi approximation by employing the microscopic in-medium cross-sections of Li and Machleidt and the phenomenological Skyrme and Gogny forces, and are compared with each other. The results for the collisional widths of giant monopole and quadrupole vibrations at zero temperature as a function of the mass number show that the collisional damping of giant monopole vibrations accounts for about 30 - 40% of the observed widths at zero temperature, while for giant quadrupole vibrations it accounts for only 20 - 30% of the observed widths at zero temperature. (orig.)

Effect of impurities on kinetic transport processes in fusion plasmas

Energy Technology Data Exchange (ETDEWEB)

Braun, Stefanie

2010-12-10

Within the framework of this thesis, different problems arising in connection with impurities have been investigated. Collisional damping of zonal flows in tokamaks: Since the Coulomb collision frequency increases with increasing ion charge, heavy, highly charged impurities play an important role in this process. The effect of such impurities on the linear response of the plasma to an external potential perturbation, as caused by zonal flows, is calculated with analytical methods. In comparison with a pure plasma, the damping of the flows occurs, as expected, considerably faster; for experimentally relevant parameters, the enhancement exceeds the effective charge Z{sub eff} of the plasma. Impurity transport driven by microturbulence in tokamaks: With regard to impurities, it is especially important whether the resulting flows are directed inwards or outwards, since they are deleterious for core energy confinement on the one hand, but on the other hand help protecting plasma-facing components from too high energy fluxes in the edge region. A semi-analytical model is presented describing the resulting impurity fluxes and the stability boundary of the underlying mode. The main goal is to bridge the gap between, on the one hand, costly numerical simulations, which are applicable to a broad range of problems but yield scarcely traceable results, and, on the other hand, analytical theory, which might ease the interpretation of the results but is so far rather rudimentary. The model is based on analytical formulae whenever possible but resorts to a numerical treatment when the approximations necessary for an analytical solution would lead to a substantial distortion of the results. Both the direction of the impurity flux and the stability boundary are found to depend sensitively on the plasma parameters such as the impurity density and the temperature gradient. Pfirsch-Schlueter transport in stellarators: Due to geometry effects, collisional transport plays a much more

Tearing modes with pressure gradient effect in pair plasmas

International Nuclear Information System (INIS)

Cai Huishan; Li Ding; Zheng Jian

2009-01-01

The general dispersion relation of tearing mode with pressure gradient effect in pair plasmas is derived analytically. If the pressure gradients of positron and electron are not identical in pair plasmas, the pressure gradient has significant influence at tearing mode in both collisionless and collisional regimes. In collisionless regime, the effects of pressure gradient depend on its magnitude. For small pressure gradient, the growth rate of tearing mode is enhanced by pressure gradient. For large pressure gradient, the growth rate is reduced by pressure gradient. The tearing mode can even be stabilized if pressure gradient is large enough. In collisional regime, the growth rate of tearing mode is reduced by the pressure gradient. While the positron and electron have equal pressure gradient, tearing mode is not affected by pressure gradient in pair plasmas.

Dynamic plasma screening effects on atomic collisions in dense plasmas

International Nuclear Information System (INIS)

Young-Dae Jung

1999-01-01

Dynamic plasma screening effects are investigated on electron-ion collisional excitation and Coulomb Bremsstrahlung processes in dense plasmas. The electron-ion interaction potential is considered by introduction of the plasma dielectric function. The straight-ling trajectory method is applied to the path of the projectile electron. The transition probability including the dynamic plasma screening effect is found to be always greater than that including the static plasma screening effects. It is found that the differential Bremsstrahlung radiation cross section including the dynamic plasma screening effect is also greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. However, when the projectile velocity is greater than the electron thermal velocity, the interaction potential is almost unshielded

Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

Energy Technology Data Exchange (ETDEWEB)

Xu, X. Q., E-mail: xxu@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ma, J. F. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States); Li, G. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China)

2014-12-15

The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.

Electron acceleration by electromagnetic irradiation of a weakly-collisional plasma

International Nuclear Information System (INIS)

Karfidov, D.M.; Lukina, N.A.; Sergeychev, K.F.

1989-01-01

In this paper, electron acceleration is investigated experimentally in both a homogeneous and an inhomogeneous plasma. In the first case acceleration is produced by development of a parametric instability, while in the second case acceleration in a plasma resonance field is used. It is demonstrated that multiple electron passes through a resonant field will produce and accelerated electron energy spectrum characterized by the effective temperature. It is established that the electron replacement current flowing in the interaction region between the plasma and a spatially-limited microwave field excites ion-acoustic turbulence in plasma and also produces an anomalously low thermal conductivity and an anomalously high resistivity

Application of plasma focus device to compression of toroidal plasma

International Nuclear Information System (INIS)

Ikuta, Kazunari

1980-01-01

A new concept of compressing a toroidal plasma using a plasma focus device is considered. Maximum compression ratio of toroidal plasma is determined merely by the initial density ratio of the toroidal plasma to a sheet plasma in a focus device because of the Rayleigh-Taylor instability. An initiation senario of plasma-linear is also proposed with a possible application of this concepts to the creation of a burning plasma in reversed field configurations, i.e., burning plasma vortex. (author)

Conference record of the 1986 IEEE international conference on plasma science

International Nuclear Information System (INIS)

Anon.

1986-01-01

This book presents the papers given at a conference on plasma science. Topics considered at the conference included inverse diode computations, collisional ion heating, gyrotron phase locking using a modulated electron beam, klystrons and lasertrons, radiation pressure on moving plasma, RF heating by cylindrical plasma waveguide modes, and deionization phase characteristics of hydrogen thyratron plasmas

An investigation into the role of metastable states on excited populations of weakly ionized argon plasmas, with applications for optical diagnostics

Science.gov (United States)

Arnold, Nicholas; Loch, Stuart; Ballance, Connor; Thomas, Ed

2017-10-01

Low temperature plasmas (Te ADAS) code suite to calculate a level-resolved, generalized collisional-radiative (GCR) model for line emission in low temperature argon plasmas. By combining our theoretical model with experimental electron temperature, density, and spectral measurements from the Auburn Linear eXperiment for Instability Studies (ALEXIS), we have developed diagnostic techniques to measure metastable fraction, electron temperature, and electron density. In the future we hope to refine our methods, and extend our model to plasmas other than ALEXIS. Supported by the U.S. Department of Energy. Grant Number: DE-FG02-00ER54476.

Non linear excitation of waves at the vicinity of plasma resonance

International Nuclear Information System (INIS)

Chiron, Arnaud

1992-01-01

This research thesis reports the study of the non linear evolution of ionic acoustic and plasma waves excited by resonant absorption of an electromagnetic wave, in a non collisional plasma, without external magnetic field, and with a parabolic density profile. The plasma resonance occurs about the density profile peak. The numerical resolution of the Zakharov equation system is performed to describe the coupled evolution of the plasma wave electric field envelope, and low frequency density disturbances. Experiments performed in the microwave domain show the existence of a new effect related to the modification of the electromagnetic wave propagation under the influence of plasma density disturbances created by the ponderomotive force. This effect which results in a collisional relaxation of plasma waves trapped in the cavity formed at resonance, cannot be taken into account by a numerical simulation using a capacitive pump field. Measurements showed that plasma waves were trapped and relaxing in a cavity with characteristic dimensions of some thousands of Debye lengths, and that the plasma wave in the cavity was stationary. A new turbulence regime is thus highlighted [fr

Aerospace Applications of Non-Equilibrium Plasma

Science.gov (United States)

Blankson, Isaiah M.

2016-01-01

Nonequilibrium plasma/non-thermal plasma/cold plasmas are being used in a wide range of new applications in aeronautics, active flow control, heat transfer reduction, plasma-assisted ignition and combustion, noise suppression, and power generation. Industrial applications may be found in pollution control, materials surface treatment, and water purification. In order for these plasma processes to become practical, efficient means of ionization are necessary. A primary challenge for these applications is to create a desired non-equilibrium plasma in air by preventing the discharge from transitioning into an arc. Of particular interest is the impact on simulations and experimental data with and without detailed consideration of non-equilibrium effects, and the consequences of neglecting non-equilibrium. This presentation will provide an assessment of the presence and influence of non-equilibrium phenomena for various aerospace needs and applications. Specific examples to be considered will include the forward energy deposition of laser-induced non-equilibrium plasmoids for sonic boom mitigation, weakly ionized flows obtained from pulsed nanosecond discharges for an annular Hall type MHD generator duct for turbojet energy bypass, and fundamental mechanisms affecting the design and operation of novel plasma-assisted reactive systems in dielectric liquids (water purification, in-pipe modification of fuels, etc.).

Plasma residual rotation in the TCABR tokamak

International Nuclear Information System (INIS)

Severo, J.H.F.; Nascimento, I.C.; Tsypin, V.S.; Galvao, R.M.O.

2003-01-01

This paper reports the first results on the measurement of the radial profiles of plasma poloidal and toroidal rotation performed on the TCABR tokamak, in the collisional regime (Pfirsch-Schluter), using Doppler shift of carbon spectral lines, measured with a high precision optical spectrometer. The results for poloidal rotation show a maximum velocity of (4.5±1.0) x 10 3 m s -1 at r ∼ 2/3a,(a-limiter radius), in the direction of the diamagnetic electron drift. Within the error limits, reasonable agreement is obtained with calculations using the neoclassical theory for a collisional plasma, except near the plasma edge, as expected. For toroidal rotation, the radial profile shows that the velocity decreases from a counter-current value of (20 ± 1) x 10 3 m s -1 , at the plasma core, to a co-current value of (2.0 ± 0.9) x 10 3 m s -1 near the limiter. An agreement within a factor 2, for the plasma core rotation, is obtained with calculations using the model proposed by Kim, Diamond and Groebner (1991 Phys. Fluids B 3 2050). (author)

Anisotropic hydrodynamics with a scalar collisional kernel

Science.gov (United States)

Almaalol, Dekrayat; Strickland, Michael

2018-04-01

Prior studies of nonequilibrium dynamics using anisotropic hydrodynamics have used the relativistic Anderson-Witting scattering kernel or some variant thereof. In this paper, we make the first study of the impact of using a more realistic scattering kernel. For this purpose, we consider a conformal system undergoing transversally homogenous and boost-invariant Bjorken expansion and take the collisional kernel to be given by the leading order 2 ↔2 scattering kernel in scalar λ ϕ4 . We consider both classical and quantum statistics to assess the impact of Bose enhancement on the dynamics. We also determine the anisotropic nonequilibrium attractor of a system subject to this collisional kernel. We find that, when the near-equilibrium relaxation-times in the Anderson-Witting and scalar collisional kernels are matched, the scalar kernel results in a higher degree of momentum-space anisotropy during the system's evolution, given the same initial conditions. Additionally, we find that taking into account Bose enhancement further increases the dynamically generated momentum-space anisotropy.

Density and field effect on electron-ion collision cross-sections in hot dense plasma; Etude de l'influence de l'environnement plasma sur les sections efficaces d'excitation collisionnelle electron-ion dans un plasma chaud et dense

Energy Technology Data Exchange (ETDEWEB)

Gaufridy de Dortan, F. de

2003-03-15

Collisional excitation cross-sections are essential for the modeling of the properties of non equilibrium plasmas. There has been a lot of work on electron impact excitation of isolated ions, but in dense plasmas, neighboring particles are expected to widely disturb these electron transitions in atoms. Plasma modeling through a radially perturbed potential has already been done but is not satisfactory as it does not account for levels degeneracy breaking and its consequences. Introduction of a quasistatic electric micro-field of neighboring ions allows us to break spherical symmetry. Our original theoretical study has given birth to a numerical code that accurately computes collisional strengths and rates (in the Distorted Waves approach) in atoms submitted to a realistic micro-field. Hydrogen- and helium-like aluminium is studied. Stark mixing widely increases rates of transitions from high l levels and forbidden transitions are field-enhanced by many orders of magnitude until they reach allowed ones. Eventually, we conduct an elementary stationary collisional radiative study to investigate field-enhancement effects on corresponding line shapes. In cases we study (aluminium, hydrogen- and helium-like) we find a relatively weak increase of K-shell line broadening.

Population inversion in recombining hydrogen plasma

International Nuclear Information System (INIS)

Furukane, Utaro; Yokota, Toshiaki; Oda, Toshiatsu.

1978-11-01

The collisional-radiative model is applied to a recombining hydrogen plasma in order to investigate the plasma condition in which the population inversion between the energy levels of hydrogen can be generated. The population inversion is expected in a plasma where the three body recombination has a large contribution to the recombining processes and the effective recombination rate is beyond a certain value for a given electron density and temperature. Calculated results are presented in figures and tables. (author)

Collisional effects in He I lines and helium abundances in planetary nebulae

International Nuclear Information System (INIS)

Clegg, R.E.S.

1987-01-01

Attention is drawn to new, 19-state quantal calculations for collisional excitation by electron impact in neutral helium. Recommended empirical formulae are given for the collisional contribution to HeI recombination lines such as λλ4471, 5876 A in gaseous nebulae. Collisional ionization of metastable (2 3 S) He I is significant for high-temperature nebulae. Collisional transfers provide significant cooling in nebulae with low heavy-element abundances. Revised mean He/H ratios for three large samples of planetary nebulae are given. (author)

Asteroid collisional history - Effects on sizes and spins

International Nuclear Information System (INIS)

Davis, D.R.; Weidenschilling, S.J.; Farinella, P.; Paolicchi, P.; Binzel, R.P.

1989-01-01

The effects of asteroid collisional history on sizes and spins of present-day objects are discussed. Collisional evolution studies indicate that collisions have altered the spin-rates of small bodies, but that the largest asteroids may have retained their primordial rotation rates. Most asteroids larger than 100 km diam have probably been shattered, but have gravitationally recaptured their fragments to form a rubble-pile structure. Large angular momentum asteroids appear to have Maclaurian spheroidal or Jacobi-ellipsoid-like shapes; some of them may have fissioned into binaries. An integrated size and spin collisional evolution model is presented, with two critical parameters: one which determines the spin rates for small fragments resulting from a shattering collision, and the other determines the fraction of impact angular momentum that is retained by the target. 36 refs

Parametric analysis of a magnetized cylindrical plasma

International Nuclear Information System (INIS)

Ahedo, Eduardo

2009-01-01

The relevant macroscopic model, the spatial structure, and the parametric regimes of a low-pressure plasma confined by a cylinder and an axial magnetic field is discussed for the small-Debye length limit, making use of asymptotic techniques. The plasma response is fully characterized by three-dimensionless parameters, related to the electron gyroradius, and the electron and ion collision mean-free-paths. There are the unmagnetized regime, the main magnetized regime, and, for a low electron-collisionality plasma, an intermediate-magnetization regime. In the magnetized regimes, electron azimuthal inertia is shown to be a dominant phenomenon in part of the quasineutral plasma region and to set up before ion radial inertia. In the main magnetized regime, the plasma structure consists of a bulk diffusive region, a thin layer governed by electron inertia, a thinner sublayer controlled by ion inertia, and the non-neutral Debye sheath. The solution of the main inertial layer yields that the electron azimuthal energy near the wall is larger than the electron thermal energy, making electron resistivity effects non-negligible. The electron Boltzmann relation is satisfied only in the very vicinity of the Debye sheath edge. Ion collisionality effects are irrelevant in the magnetized regime. Simple scaling laws for plasma production and particle and energy fluxes to the wall are derived.

ELM suppression in low edge collisionality H-mode discharges using n = 3 magnetic perturbations

Energy Technology Data Exchange (ETDEWEB)

Burrell, K H [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Evans, T E [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Doyle, E J [University of California, Los Angeles, California (United States); Fenstermacher, M E [Lawrence Livermore National Laboratory, Livermore, California (United States); Groebner, R J [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Leonard, A W [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Moyer, R A [University of California, San Diego, California (United States); Osborne, T H; Schaffer, M J; Snyder, P B [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Thomas, P R [CEA Cadarache EURATOM Association, Cadarache (France); West, W P [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Boedo, J A [University of California, San Diego, California (United States); Garofalo, A M [Columbia University, New York, New York (United States); Gohil, P; Jackson, G L; La Haye, R J [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Lasnier, C J [Lawrence Livermore National Laboratory, Livermore, California (United States); Reimerdes, H [Columbia University, New York, New York (United States); Rhodes, T L [University of California, Los Angeles, California (United States); Scoville, J T [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Solomon, W M [Princeton Plasma Physics Laboratory, Princeton, New Jersey (United States); Thomas, D M [General Atomics, PO Box 85608, San Diego, CA 92186-9784 (United States); Wang, G [University of California, Los Angeles, California (United States); Watkins, J G [Sandia National Laboratories, Albuquerque, New Mexico (United States); Zeng, L [University of California, Los Angeles, California (United States)

2005-12-15

Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run with constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close to those desired for next step burning plasma experiments such as ITER and provide a means of eliminating the rapid erosion of divertor components in such machines which could be caused by giant ELMs. The ELM suppression is due to an enhancement in the edge particle transport which reduces pedestal current density and maximum edge pressure gradient below the threshold for peeling-ballooning modes. These n = 3 magnetic perturbations provide a means of active control of edge plasma transport.

ELM suppression in low edge collisionality H-mode discharges using n = 3 magnetic perturbations

International Nuclear Information System (INIS)

Burrell, K H; Evans, T E; Doyle, E J; Fenstermacher, M E; Groebner, R J; Leonard, A W; Moyer, R A; Osborne, T H; Schaffer, M J; Snyder, P B; Thomas, P R; West, W P; Boedo, J A; Garofalo, A M; Gohil, P; Jackson, G L; La Haye, R J; Lasnier, C J; Reimerdes, H; Rhodes, T L; Scoville, J T; Solomon, W M; Thomas, D M; Wang, G; Watkins, J G; Zeng, L

2005-01-01

Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run with constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close to those desired for next step burning plasma experiments such as ITER and provide a means of eliminating the rapid erosion of divertor components in such machines which could be caused by giant ELMs. The ELM suppression is due to an enhancement in the edge particle transport which reduces pedestal current density and maximum edge pressure gradient below the threshold for peeling-ballooning modes. These n = 3 magnetic perturbations provide a means of active control of edge plasma transport

Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

Science.gov (United States)

Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

2018-05-01

Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

Self-focusing and self-defocusing of elliptically shaped Gaussian laser beams in plasmas

Energy Technology Data Exchange (ETDEWEB)

Nayyar, V P; Soni, V S [Punjabi Univ., Patiala (India). Dept. of Physics

1979-02-14

This paper presents a study of the self-focusing and self-defocusing of elliptically shaped Gaussian laser beams in collisional and collisionless plasmas. The non-linear dependence of the dielectric constant inside a collisional plasma is due to inhomogeneous heating of energy carriers and in a collisionless plasma it is due to the ponderomotive force. It is found that the beam gets focused at different points in different planes, exhibiting the effect of astigmatism. In certain power regions considered, the beam either converges or defocuses in both the directions, while in some other regions of the power spectrum one dimension of the beam focuses while the other defocuses. The beam also propagates in an oscillatory waveguide.

Application of fusion plasma technology. Final report

International Nuclear Information System (INIS)

Sabri, Z.A.

1976-06-01

This report presents principal findings of studies conducted at Iowa State on Applications of Fusion Plasma Technology. Two tasks were considered. The first was to identify and investigate plasma processes for near term industrial applications of already developed plasma technology. The second was to explore the potential of reprocessing the fuel for fusion test facilities in a closed-cycle system. For the first task, two applications were considered. One was alumina reduction in magnetically confined plasmas, and the other was uranium enrichment using plasma centrifuges. For the second task, in-core and ex-core plasma purification were considered. Separation techniques that are compatible with the plasma state were identified and preliminary analysis of their effectiveness were carried out. The effects of differential ionization of impurities on the separation effectiveness are considered. Possible technical difficulties in both tasks are identified and recommendations for future work are given

Generation mechanism and properties of plasma double layers

International Nuclear Information System (INIS)

Sanduloviciu, M.; Lozneanu, E.

1985-01-01

The generation mechanism of plasma double layers is studied surveying the results of some experiments. The main mechanism is the same in the cases of collisional and collisionless plasmas. Inelastic quantum collision processes taking place between plasma electrons, accelerated in a local field up to near the same oriented velocity and the neutral particles of the background gases create the necessary conditions for double layer formation. (D.Gy.)

Experimental observation of strong coupling effects on the dispersion of dust acoustic waves in a plasma

OpenAIRE

Bandyopadhyay, P.; Prasad, G.; Sen, A.; Kaw, P. K.

2016-01-01

The dispersion properties of low frequency dust acoustic waves in the strong coupling regime are investigated experimentally in an argon plasma embedded with a mixture of kaolin and $MnO_2$ dust particles. The neutral pressure is varied over a wide range to change the collisional properties of the dusty plasma. In the low collisional regime the turnover of the dispersion curve at higher wave numbers and the resultant region of $\\partial\\omega/\\partial k < 0$ are identified as signatures of du...

Curvature-induced electrostatic drift modes in a toroidal plasma

International Nuclear Information System (INIS)

Venema, M.

1985-01-01

This thesis deals with a number of problems in the theory of linear stability of a hot, fully ionized plasma immersed in a strong magnetic field. The most widely used system to magnetically confine a plasma is the tokamak. This is a toroidal, current carrying device with a strong, externally imposed, magnetic field. The author discusses the linear theory of unstable, low-frequency waves in the gradient region, restricted to electrostatic waves. In that case the resulting radial fluxes of particles and energy are due to electric cross-field drifts. In the presence of magnetic fluctuations and small-scale reconnection phenomena, radial transport could also be predominantly along field lines. At present, it is not clear which of the two mechanisms is the dominant feature of the observed anomalous transport. First, the author introduces the theory of drift waves in toroidal geometry. Next, the electrostratic drift modes in toroidal geometry (weakly collisional regime), the equations for low-frequency waves in the strongly collisional regime and the electrostatic drift modes (strongly collisional regime) are discussed. (Auth.)

Laser-plasma interactions and applications

CERN Document Server

Neely, David; Bingham, Robert; Jaroszynski, Dino

2013-01-01

Laser-Plasma Interactions and Applications covers the fundamental and applied aspects of high power laser-plasma physics. With an internationally renowned team of authors, the book broadens the knowledge of young researchers working in high power laser-plasma science by providing them with a thorough pedagogical grounding in the interaction of laser radiation with matter, laser-plasma accelerators, and inertial confinement fusion. The text is organised such that the theoretical foundations of the subject are discussed first, in Part I. In Part II, topics in the area of high energy density physics are covered. Parts III and IV deal with the applications to inertial confinement fusion and as a driver of particle and radiation sources, respectively. Finally, Part V describes the principle diagnostic, targetry, and computational approaches used in the field. This book is designed to give students a thorough foundation in the fundamental physics of laser-plasma interactions. It will also provide readers with knowl...

Dust particle charge and screening in the collisional RF plasma sheath

NARCIS (Netherlands)

Beckers, J.; Trienekens, D.J.M.; Kroesen, G.M.W.; Sprouse, G.D.

2012-01-01

Once immersed in plasma, a dust particle gathers a highly negative charge due to the net collection of free electrons. In most plasma's on earth and with particle sizes is in the micrometer range, the gravitational force is dominant and consequently the particle ends up within the plasma sheath

Suppression of large edge localized modes with edge resonant magnetic fields in high confinement DIII-D plasmas

International Nuclear Information System (INIS)

Thomas, P.R.; Becoulet, M.; Evans, T.E.; Osborne, T.H.; Groebner, R.J.; Jackson, G.L.; Haye, R.J. La; Schaffer, M.J.; West, W.P.; Moyer, R.A.; Rhodes, T.L.; Rudakov, D.L.; Watkins, J.G.; Boedo, J.A.; Doyle, E.J.; Wang, G.; Zeng, L.; Fenstermacher, M.E.; Groth, M.; Lasnier, C.J.; Finken, K.H.; Harris, J.H.; Pretty, D.G.; Masuzaki, S.; Ohyabu, N.; Reimerdes, H.; Wade, M.R.

2005-01-01

Large divertor heat pulses due to Type-I edge localized modes (ELMs) have been eliminated reproducibly in DIII-D with small dc currents driven in a simple magnetic perturbation coil. The current required to eliminate all but a few isolated Type-I ELMs, during a coil pulse, is less than 0.4% of plasma current. Modelling shows that the perturbation fields resonate with plasma flux surfaces across most of the pedestal region (0.9 ≤ N ≤ 1.0), when q95 = 3.7±0.2 creating small remnant magnetic islands surrounded by weakly stochastic field lines. The stored energy, N , H-mode quality factor and global energy confinement time are unaltered by the magnetic perturbation. At high collisionality (ν* ∼0.5-1), there is no obvious effect of the perturbation on the edge profiles and yet ELMs are suppressed, nearly completely, for up to 9τ E . At low collisionality (ν* <0.1), there is a density pump-out and complete ELM suppression, reminiscent of the DIIID QH- mode. Other differences, specifically in the resonance condition and the magnetic fluctuations, suggest that different mechanisms are at play in the different collisionality regimes. In addition to a description and interpretation of the DIIID data, the application of this method to ELM control on other machines, such as JET and ITER will be discussed. (author)

Sum rules for collisional processes

International Nuclear Information System (INIS)

Oreg, J.; Goldstein, W.H.; Bar-Shalom, A.; Klapisch, M.

1991-01-01

We derive level-to-configuration sum rules for dielectronic capture and for collisional excitation and ionization. These sum rules give the total transition rate from a detailed atomic level to an atomic configuration. For each process, we show that it is possible to factor out the dependence on continuum-electron wave functions. The remaining explicit level dependence of each rate is then obtained from the matrix element of an effective operator acting on the bound orbitals only. In a large class of cases, the effective operator reduces to a one-electron monopole whose matrix element is proportional to the statistical weight of the level. We show that even in these cases, nonstatistical level dependence enters through the dependence of radial integrals on continuum orbitals. For each process, explicit analytic expressions for the level-to-configuration sum rules are given for all possible cases. Together with the well-known J-file sum rule for radiative rates [E. U. Condon and G. H. Shortley, The Theory of Atomic Spectra (University Press, Cambridge, 1935)], the sum rules offer a systematic and efficient procedure for collapsing high-multiplicity configurations into ''effective'' levels for the purpose of modeling the population kinetics of ionized heavy atoms in plasma

Diagram of collisional regimes for particle diffusion in a stochastic magnetic field

International Nuclear Information System (INIS)

Misguich, J.H.; Balescu, R.

1995-01-01

This document deals with static stochastic fields, where magnetic lines experience exponential separation and magnetic diffusion. It more particularly focuses on the diffusivity of collisional particles in such a fields and presents a general graph which describes most regimes of collisional and weakly collisional diffusion for guiding centers in a time-independent magnetic field. (TEC). 9 refs., 1 fig., 2 tabs

Collisional boundary layer analysis for neoclassical toroidal plasma viscosity in tokamaks

Czech Academy of Sciences Publication Activity Database

Shaing, K.C.; Cahyna, Pavel; Bécoulet, M.; Park, J.-K.; Sabbagh, S.A.; Chu, M.S.

2008-01-01

Roč. 15, č. 8 (2008), 082506-1-7 ISSN 1070-664X Institutional research plan: CEZ:AV0Z20430508 Keywords : plasma boundary layers * plasma toroidal confinement * Tokamak devices Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.427, year: 2008 http://dx.doi.org/10.1063/1.2969434

Four-wave mixing and phase conjugation in plasmas

International Nuclear Information System (INIS)

Federici, J.F.

1989-01-01

Nonlinear optical effects such as Stimulated Brillouin Scattering, Stimulated Raman Scattering, self-focusing, wave-mixing, parametric mixing, etc., have a long history in plasma physics. Recently, four-wave mixing in plasmas and its applications to phase conjugation has been extensively studied. Although four-wave mixing (FWM), using various nonlinear mediums, has many practical applications in the visible regime, no successful attempt has been made to study or demonstrate FWM for wavelengths longer than 10μm. Plasmas as phase conjugate mirrors have received considerable attention since they become more efficient at longer wavelengths (far-infrared to microwave). The purpose of this thesis is to study various fundamental issues which concern the suitability of plasmas for four-wave mixing and phase conjugation. The major contributions of this thesis are the identification and study of thermal and ionization nonlinearities as potential four-wave mixing and phase conjugation mechanisms and the study of the affect of density inhomogeneities on the FWM process. Using a fluid description for the plasma, this thesis demonstrates that collisional heating generates a thermal force which substantially enhances the phase conjugate reflectivity. The prospect of using a novel ionization nonlinearity in weakly ionized plasmas for wave-mixing and phase conjugation is discussed. The ionization nonlinearity arises from localized heating of the plasma by the beat-wave. Wherever, the local temperature is increased, a plasma density grating is produced due to increased electron-impact ionization. Numerical estimates of the phase conjugate reflectivity indicate reflectivities in the range of 10 -4 -10 -3 are possible in a weakly ionized steady-state gas discharge plasma

Electrostatic sheath at the boundary of a collisional dusty plasma

Indian Academy of Sciences (India)

Department of Physics, Cotton College, Guwahati 781 001, India. Abstract. Considering the Boltzmann response of the ions ... respect to normal electronic charge (q ~105. –106e). The mass of the dust grains can have very high value too, up to ... degrees of plasma dynamics. Thus, the theoretical modeling of a dusty plasma ...

Frugal Biotech Applications of Low-Temperature Plasma.

Science.gov (United States)

Machala, Zdenko; Graves, David B

2017-09-01

Gas discharge low-temperature air plasma can be utilized for a variety of applications, including biomedical, at low cost. We term these applications 'frugal plasma' - an example of frugal innovation. We demonstrate how simple, robust, low-cost frugal plasma devices can be used to safely disinfect instruments, surfaces, and water. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the two weighting scheme for δf collisional transport simulation

International Nuclear Information System (INIS)

Okamoto, M.; Nakajima, N.; Wang, W.

1999-08-01

The validity is given to the newly proposed two weighting δf scheme (Wang et al., Research Report of National Institute for Fusion Science NIFS-588, 1999) for collisional or neoclassical transport calculations, which can solve the drift kinetic equation taking account of effects of steep plasma gradients, large radial electric field, finite banana width, and the non-standard orbit topology near the axis. The marker density functions in weight equations are successively solved by using the idea of δf method and a hierarchy of equations for weight and marker density functions is obtained. These hierarchy equations are solved by choosing an appropriate source function for each marker density. Thus the validity of the two weighting δf scheme is mathematically proved. (author)

Experimental and theoretical investigation of radiation and dynamics properties in laser-produced carbon plasmas

Science.gov (United States)

Min, Qi; Su, Maogen; Wang, Bo; Cao, Shiquan; Sun, Duixiong; Dong, Chenzhong

2018-05-01

The radiation and dynamics properties of laser-produced carbon plasma in vacuum were studied experimentally with aid of a spatio-temporally resolved emission spectroscopy technique. In addition, a radiation hydrodynamics model based on the fluid dynamic equations and the radiative transfer equation was presented, and calculation of the charge states was performed within the time-dependent collisional radiative model. Detailed temporal and spatial evolution behavior about plasma parameters have been analyzed, such as velocity, electron temperature, charge state distribution, energy level population, and various atomic processes. At the same time, the effects of different atomic processes on the charge state distribution were examined. Finally, the validity of assuming a local thermodynamic equilibrium in the carbon plasma expansion was checked, and the results clearly indicate that the assumption was valid only at the initial (applicable near the plasma boundary because of a sharp drop of plasma temperature and electron density.

Plasma heating in a variable magnetic field

Energy Technology Data Exchange (ETDEWEB)

Kichigin, G. N., E-mail: king@iszf.irk.ru [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics (Russian Federation)

2013-05-15

The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfven.

Plasma expansion: fundamentals and applications

International Nuclear Information System (INIS)

Engeln, R; Mazouffre, S; Vankan, P; Bakker, I; Schram, D C

2002-01-01

The study of plasma expansion is interesting from a fundamental point of view as well as from a more applied point of view. We here give a short overview of the way properties like density, velocity and temperature behave in an expanding thermal plasma. Experimental data show that the basic phenomena of plasma expansion are to some extent similar to those of the expansion of a hot neutral gas. From the application point of view, we present first results on the use of an expanding thermal plasma in the plasma-activated catalysis of ammonia, from N 2 -H 2 mixtures

Comparison of bootstrap current and plasma conductivity models applied in a self-consistent equilibrium calculation for Tokamak plasmas

Energy Technology Data Exchange (ETDEWEB)

Andrade, Maria Celia Ramos; Ludwig, Gerson Otto [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: mcr@plasma.inpe.br

2004-07-01

Different bootstrap current formulations are implemented in a self-consistent equilibrium calculation obtained from a direct variational technique in fixed boundary tokamak plasmas. The total plasma current profile is supposed to have contributions of the diamagnetic, Pfirsch-Schlueter, and the neoclassical Ohmic and bootstrap currents. The Ohmic component is calculated in terms of the neoclassical conductivity, compared here among different expressions, and the loop voltage determined consistently in order to give the prescribed value of the total plasma current. A comparison among several bootstrap current models for different viscosity coefficient calculations and distinct forms for the Coulomb collision operator is performed for a variety of plasma parameters of the small aspect ratio tokamak ETE (Experimento Tokamak Esferico) at the Associated Plasma Laboratory of INPE, in Brazil. We have performed this comparison for the ETE tokamak so that the differences among all the models reported here, mainly regarding plasma collisionality, can be better illustrated. The dependence of the bootstrap current ratio upon some plasma parameters in the frame of the self-consistent calculation is also analysed. We emphasize in this paper what we call the Hirshman-Sigmar/Shaing model, valid for all collisionality regimes and aspect ratios, and a fitted formulation proposed by Sauter, which has the same range of validity but is faster to compute than the previous one. The advantages or possible limitations of all these different formulations for the bootstrap current estimate are analysed throughout this work. (author)

The collisional Penrose process

Science.gov (United States)

Schnittman, Jeremy D.

2018-06-01

Shortly after the discovery of the Kerr metric in 1963, it was realized that a region existed outside of the black hole's event horizon where no time-like observer could remain stationary. In 1969, Roger Penrose showed that particles within this ergosphere region could possess negative energy, as measured by an observer at infinity. When captured by the horizon, these negative energy particles essentially extract mass and angular momentum from the black hole. While the decay of a single particle within the ergosphere is not a particularly efficient means of energy extraction, the collision of multiple particles can reach arbitrarily high center-of-mass energy in the limit of extremal black hole spin. The resulting particles can escape with high efficiency, potentially serving as a probe of high-energy particle physics as well as general relativity. In this paper, we briefly review the history of the field and highlight a specific astrophysical application of the collisional Penrose process: the potential to enhance annihilation of dark matter particles in the vicinity of a supermassive black hole.

Dynamics of collisional particles in a fluctuating magnetic field

International Nuclear Information System (INIS)

Spineanu, F.; Vlad, M.

1995-01-01

The equations of motion of a test particle in a stochastic magnetic field and interacting through collisions with a plasma are Langevin-type equations. Under reasonable assumptions on the statistical properties of the random processes (field and collisional velocity fluctuations), we perform an analytical calculation of the mean-square displacement (MSD) of the particle. The basic nonlinearity in the problem (Lagrangian argument of the random field) yields complicated averages, which we carry out using a functional formalism. The result is expressed as a series, and we find the conditions for its convergence, i.e. the limits of validity of our approach (essentially, we must restrict attention to non-chaotic regimes). Further, employing realistic bounds (spectral cut-off and limited time of observation), we derive an explicit formula for the MSD. We show that from this unique expression, we can obtain several previously known results. (author)

A numerical model for diffusion of helium in a hydrogen plasma

International Nuclear Information System (INIS)

Potters, J.H.H.M.

1983-07-01

A quasi-cylindrical steady-state numerical model for the diffusion of helium in a hydrogen plasma is presented, adopting collisional plus either ALCATOR-INTOR- or ASDEX-like anomalous transport for the charged species. The coupled momentum and conservation equations for H + , He + and He ++ are solved to obtain radial profiles of their densities, consistent with those of the neutral species. For the neutrals, a diffusion equation is used for the transport of H, whereas He is assumed to enter the plasma with an energy equal to the temperature of the plasma immediately in front of the wall. A stable numerical scheme for the solution of the coupled ion and electron energy balances is discussed. Results are presented for the JET-tokamak, using prescribed temperature profiles. Collisional effects are shown to produce an enhancement of the alpha particle density about 10 centimetres in front of the wall, especially in combination with ALCATOR-INTOR-like scaling. The neutral helium density that accumulates in the outer plasma is too low to allow for pumping helium from a cool plasma/gas blanket

Stability of axisymmetric plasmas in closed line magnetic fields

International Nuclear Information System (INIS)

Simakov, A.N.; Vernon Wong, H.; Berk, H.L.

2003-01-01

The stability of axisymmetric plasmas confined by closed poloidal magnetic field lines is considered. The results are relevant to plasmas in the dipolar fields of stars and planets, as well as the Levitated Dipole Experiment, multipoles, Z pinches and field reversed configurations. The ideal MHD energy principle is employed to study the stability of pressure driven shear Alfven modes. A point dipole is considered in detail to demonstrate that equilibria exist which are MHD stable for arbitrary beta. Effects of sound waves and plasma resistivity are investigated for Z pinch and point dipole equilibria by means of resistive MHD theory. Kinetic theory is used to study drift frequency modes and their interaction with MHD modes near the ideal stability boundary for different collisionality regimes. Effects of collisional dissipation on drift mode stability are explicitly evaluated and applied to a Z pinch. The role of finite Larmor radius effects and drift reversed particles in modifying ideal stability thresholds is examined. (author)

Convective cells and transport in toroidal plasmas

International Nuclear Information System (INIS)

Hassam, A.B.; Kulsrud, R.M.

1978-12-01

The properties of convective cells and the diffusion resulting from such cells are significantly influenced by an inhomogeneity in the extermal confining magnetic field, such as that in toroidal plasmas. The convective diffusion in the presence of a field inhomogeneity is estimated. For a thermal background, this diffusion is shown to be substantially smaller than classical collisional diffusion. For a model nonthermal background, the diffusion is estimated, for typical parameters, to be at most of the order of collisional diffusion. The model background employed is based on spectra observed in numerical simulations of drift-wave-driven convective cells

Industrial Applications of Low Temperature Plasmas

International Nuclear Information System (INIS)

Bardsley, J N

2001-01-01

The use of low temperature plasmas in industry is illustrated by the discussion of four applications, to lighting, displays, semiconductor manufacturing and pollution control. The type of plasma required for each application is described and typical materials are identified. The need to understand radical formation, ionization and metastable excitation within the discharge and the importance of surface reactions are stressed

[Plasma properties research: Task 3

International Nuclear Information System (INIS)

1992-01-01

The principal research activities of the Magneto-Fluid Dynamics Division relate to magnetic fusion plasma physics. In addition, there is a modest amount of work in closely related areas, including space plasma physics, fluid dynamics, and dynamical systems. Members of the Magneto-Fluid Dynamics Division maintain close contacts with fusion researchers in the US and abroad. Some of the work of the Division is clearly directed towards ITER and TPX, while other problems relate to the broader development of fusion plasma physics and to the support of other issues arising in the many experimental programs. Topics of some note in the last year that are discussed in this report are: Application of sophisticated statistical techniques to tokamak data reduction, including time series analysis of TFTR fluctuation data and spline analysis of profile data. Continuing development of edge plasma and divertor modelling, including initial ergodic divertor studies. Analysis of energetic fusion products losses from TFTR plasmas. Examination of anomalous transport in dynamical systems induced by chaotic-like Hamiltonian motion. Numerical simulation of the development of singular MHD equilibria. Exploration of the validity of moment expansions of kinetic equations for weakly collisional systems. Studies of RF- and ripple-induced helium ash removal. Ballooning mode studies in fluids and rotating stars. Studies in dynamical systems, including explosive instabilities, development of chaos, and motion of collisionless particles in a domain with overlapping islands

Neoclassical current and plasma rotation in helical systems

International Nuclear Information System (INIS)

Nakajima, N.; Okamoto, M.

1991-01-01

In order to clarify geometrical effects of the magnetic field on the neoclassical theory in general toroidal systems, the neoclassical parallel particle flow, heat flux, current and plasma rotation of a multispecies plasma are examined using the moment approach on the basis of the original papers under the assumptions of no fluctuations, no external sources and losses except for a fast ion beam and an external inductive electric field, steady state, and |u a | Ta where u a and v Ta are the macro and thermal velocity of species a, respectively. Hence, we might have a point of view of unifying understanding the neoclassical theory in general toroidal systems. Three collisionality regimes, i.e., the 1/ν (in non-axisymmetric toroidal systems) or banana (in axisymmetric toroidal systems), plateau, and Pfirsch-Schlueter collisionality regimes are examined separately. (author) 8 refs

Initial evolution of nonlinear magnetic islands in high temperature plasmas

International Nuclear Information System (INIS)

Kotschenreuther, M.

1988-06-01

The evolution of nonlinear magnetic islands is computed in the kinetic collisionality regime called the semicollisional regime, which is appropriate to present fusion confinement devices. Realistic effects are included, such as the presence of small external field errors, radial electric fields, and omega. When present simultaneously, these effects can greatly change the stability of small amplitude nonlinear islands. Islands with Δ' > O can sometimes be prevented from growing to macroscopic size; it is also possible to produce moderate mode-number nonlinear instabilities in the plasma edge. Furthermore, island growth can be prevented by application of external fields with suitably chosen amplitude and frequency

Transport in a toroidally confined pure electron plasma

International Nuclear Information System (INIS)

Crooks, S.M.; ONeil, T.M.

1996-01-01

O close-quote Neil and Smith [T.M. O close-quote Neil and R.A. Smith, Phys. Plasmas 1, 8 (1994)] have argued that a pure electron plasma can be confined stably in a toroidal magnetic field configuration. This paper shows that the toroidal curvature of the magnetic field of necessity causes slow cross-field transport. The transport mechanism is similar to magnetic pumping and may be understood by considering a single flux tube of plasma. As the flux tube of plasma undergoes poloidal ExB drift rotation about the center of the plasma, the length of the flux tube and the magnetic field strength within the flux tube oscillate, and this produces corresponding oscillations in T parallel and T perpendicular . The collisional relaxation of T parallel toward T perpendicular produces a slow dissipation of electrostatic energy into heat and a consequent expansion (cross-field transport) of the plasma. In the limit where the cross section of the plasma is nearly circular the radial particle flux is given by Γ r =1/2ν perpendicular,parallel T(r/ρ 0 ) 2 n/(-e∂Φ/∂r), where ν perpendicular,parallel is the collisional equipartition rate, ρ 0 is the major radius at the center of the plasma, and r is the minor radius measured from the center of the plasma. The transport flux is first calculated using this simple physical picture and then is calculated by solving the drift-kinetic Boltzmann equation. This latter calculation is not limited to a plasma with a circular cross section. copyright 1996 American Institute of Physics

Experimental studies of coaxial plasma gun current

International Nuclear Information System (INIS)

Price, D.W.

1988-01-01

In this investigation of a coaxial plasma gun, plasma sheath currents and related behavior are examined. Plasma behavior in the gun affects gun characteristics. Plasma gun applications are determined by the plasma behavior. The AFWL PUFF capacitor bank (72 μF, 29 nH, 120 kV) drives the plasma gun using a deuterium fill gas. The gas breakdown site is isolated from the dielectric/vacuum interface in the AFWL system. Two gas values deliver gas in the system. The first delivers gas from the gun breech and the second optional valve delivers gas to the gun muzzle. Currents and voltages are measured by Rogowski coils, B probes and capacitive voltage probes. A O-D slug model is used to predict the current, inductance, gun voltage and plasma sheath velocity. The slug model assumes the sheath transits the gun with all mass in the sheath. In the snowplow mode, the plasma sheath is thin with a sharp current rise and drop. Our system operated in a transition mode between the snowplow and deflagration modes with early snowplow behavior and late deflagration behavior. Neutrons are produced in a plasma pinch at the gun muzzle, indicating snowplow behavior. The slug theory models overall gun behavior to experimental accuracy. Experimental results are compared to four theories for plasma sheath velocities: the Alfven collisionally limited model, the Rosenbluth model, the Fishbine saturated model and a single particle drift model. Experimental velocities vary from 10 5 to 10 6 m/s. Only the single particle drift and the slug model calculations are of the right magnitude (8 x 10 5 m/s). The Fishbine and the Rosenbluth models predict slower velocities (2 x 10 5 m/s). The Alfven model is not applicable to this system

Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

Science.gov (United States)

Hash, David B.; Govindan, T. R.; Meyyappan, M.

2004-01-01

In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

International Nuclear Information System (INIS)

Inoue, H.; Yamoto, S.; Hatayama, A.; Homma, Y.

2016-01-01

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Extended numerical modeling of impurity neoclassical transport in tokamak edge plasmas

Energy Technology Data Exchange (ETDEWEB)

Inoue, H.; Yamoto, S.; Hatayama, A. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Homma, Y. [Graduate School of Science and Technology, Keio University, Hiyoshi, Yokohama (Japan); Research Fellow of Japan Society for the Promotion of Science, Tokyo (Japan)

2016-08-15

Understanding of impurity transport in tokamaks is an important issue in order to reduce the impurity contamination in fusion core plasmas. Recently, a new kinetic numerical scheme of impurity classical/neoclassical transport has been developed. This numerical scheme makes it possible to include classical self-diffusion (CL SD), classical inward pinch (CL IWP), and classical temperature screening effect (CL TSE) of impurity ions. However, impurity neoclassical transport has been modeled only in the case where background plasmas are in the Pfirsch-Schluter (PS) regime. The purpose of this study is to extend our previous model to wider range of collisionality regimes, i.e., not only the PS regime, but also the plateau regime. As in the previous study, a kinetic model with Binary Collision Monte-Carlo Model (BMC) has been adopted. We focus on the modeling of the neoclassical self-diffusion (NC SD) and the neoclassical inward pinch (NC IWP). In order to simulate the neoclassical transport with the BCM, velocity distribution of background plasma ions has been modeled as a deformed Maxwell distribution which includes plasma density gradient. Some test simulations have been done. As for NC SD of impurity ions, our scheme reproduces the dependence on the collisionality parameter in wide range of collisionality regime. As for NC IWP, in cases where test impurity ions and background ions are in the PS and plateau regimes, parameter dependences have been reproduced. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Validity of the Taylor hypothesis for linear kinetic waves in the weakly collisional solar wind

International Nuclear Information System (INIS)

Howes, G. G.; Klein, K. G.; TenBarge, J. M.

2014-01-01

The interpretation of single-point spacecraft measurements of solar wind turbulence is complicated by the fact that the measurements are made in a frame of reference in relative motion with respect to the turbulent plasma. The Taylor hypothesis—that temporal fluctuations measured by a stationary probe in a rapidly flowing fluid are dominated by the advection of spatial structures in the fluid rest frame—is often assumed to simplify the analysis. But measurements of turbulence in upcoming missions, such as Solar Probe Plus, threaten to violate the Taylor hypothesis, either due to slow flow of the plasma with respect to the spacecraft or to the dispersive nature of the plasma fluctuations at small scales. Assuming that the frequency of the turbulent fluctuations is characterized by the frequency of the linear waves supported by the plasma, we evaluate the validity of the Taylor hypothesis for the linear kinetic wave modes in the weakly collisional solar wind. The analysis predicts that a dissipation range of solar wind turbulence supported by whistler waves is likely to violate the Taylor hypothesis, while one supported by kinetic Alfvén waves is not.

Gyrokinetic simulations in general geometry and applications to collisional damping of zonal flows

International Nuclear Information System (INIS)

Lin, Z.; Hahm, T.S.; Lee, W.W.; Tang, W.M.; White, R.B.

2000-01-01

A fully three-dimensional gyrokinetic particle code using magnetic coordinates for general geometry has been developed and applied to the investigation of zonal flows dynamics in toroidal ion-temperature-gradient turbulence. Full torus simulation results support the important conclusion that turbulence-driven zonal flows significantly reduce the turbulent transport. Linear collisionless simulations for damping of an initial poloidal flow perturbation exhibit an asymptotic residual flow. The collisional damping of this residual causes the dependence of ion thermal transport on the ion-ion collision frequency even in regimes where the instabilities are collisionless

A collision model in plasma particle simulations

International Nuclear Information System (INIS)

Ma Yanyun; Chang Wenwei; Yin Yan; Yue Zongwu; Cao Lihua; Liu Daqing

2000-01-01

In order to offset the collisional effects reduced by using finite-size particles, β particle clouds are used in particle simulation codes (β is the ratio of charge or mass of modeling particles to real ones). The method of impulse approximation (strait line orbit approximation) is used to analyze the scattering cross section of β particle clouds plasmas. The authors can obtain the relation of the value of a and β and scattering cross section (a is the radius of β particle cloud). By using this relation the authors can determine the value of a and β so that the collisional effects of the modeling system is correspondent with the real one. The authors can also adjust the values of a and β so that the authors can enhance or reduce the collisional effects fictitiously. The results of simulation are in good agreement with the theoretical ones

Collisional shifts in optical-lattice atom clocks

International Nuclear Information System (INIS)

Band, Y. B.; Vardi, A.

2006-01-01

We theoretically study the effects of elastic collisions on the determination of frequency standards via Ramsey-fringe spectroscopy in optical-lattice atom clocks. Interparticle interactions of bosonic atoms in multiply occupied lattice sites can cause a linear frequency shift, as well as generate asymmetric Ramsey-fringe patterns and reduce fringe visibility due to interparticle entanglement. We propose a method of reducing these collisional effects in an optical lattice by introducing a phase difference of π between the Ramsey driving fields in adjacent sites. This configuration suppresses site-to-site hopping due to interference of two tunneling pathways, without degrading fringe visibility. Consequently, the probability of double occupancy is reduced, leading to cancellation of collisional shifts

Neoclassical transport in a multiple-helicity torsatron in the low-collisionality (1/#betta#) regime

International Nuclear Information System (INIS)

Shaing, K.C.; Hokin, S.A.

1983-02-01

For a sufficiently high number of field periods (m/iota > l), the magnetic field of a multiple helicity torsatron can be reduced to a simple form such that the second adiabatic invariant J can be calculated. It is found that the particle and the heat fluxes for a multiple helicity torsatron in the low collisionality (1/#betta#) regime have the same geometric dependences. An optimization of both quantities is carried out for a given equilibrium constraint. It is shown that the transport fluxes can be smaller than those of the conventional stellarator by an order of magnitude. The effect of finite plasma beta on the neoclassical fluxes is also studied

Collisional-radiative model for neutral helium in plasma. Excitation cross section and singlet-triplet wavefunction mixing

Energy Technology Data Exchange (ETDEWEB)

Goto, Motoshi [National Inst. for Fusion Science, Toki, Gifu (Japan); Fujimoto, Takashi

1997-10-01

We have revised the collisional-radiative (CR) model code of neutral helium (T. Fujimoto, JQSRT 21, 1979). The spin-orbit interaction gives rise to mixing of the wavefunctions of the singlet and triplet states. The degree of the mixing depends on the magnetic field, and at the field strength of the level-anticrossings complete mixing, or complete breakdown of the L-S coupling scheme, occurs. We have approximately incorporated this effect into the code. We have reviewed the excitation cross section data for electron impacts. For transitions starting from the ground state, the recent assessment by the group led by Dr. de Heer is judged satisfactory. For transitions from the metastable levels the assessment by the same group appears rather conservative; there remains a question about the cross section values near the threshold. For transitions between different-l levels within the same multiplicity and same n, a semi-empirical formula based on the Born cross section gives a good agreement with experiment. Proton impacts are also considered for these transitions. We compare the new cross sections with those used in the original version. These cross sections for transitions starting from the metastable levels are fitted by analytical formulas and the parameter values are given. We also give parameter values for the excitation rate coefficient for these transitions as well as for transitions starting from the ground state. With all the above revisions incorporated into the CR model code, we have calculated the energy loss rates and the line intensity ratios for the purpose of plasma diagnostics, where the effect of a magnetic field is noted. The calculated population distribution over excited levels are compared with experiment, and a tentative conclusion is drawn concerning the excitation cross section from the metastable level. (author)

Modelling of Argon Cold Atmospheric Plasmas for Biomedical Applications

Science.gov (United States)

Atanasova, M.; Benova, E.; Degrez, G.; van der Mullen, J. A. M.

2018-02-01

Plasmas for biomedical applications are one of the newest fields of plasma utilization. Especially high is the interest toward plasma usage in medicine. Promising results are achieved in blood coagulation, wound healing, treatment of some forms of cancer, diabetic complications, etc. However, the investigations of the biomedical applications from biological and medical viewpoint are much more advanced than the studies on the dynamics of the plasma. In this work we aim to address some specific challenges in the field of plasma modelling, arising from biomedical applications - what are the plasma reactive species’ and electrical fields’ spatial distributions as well as their production mechanisms; what are the fluxes and energies of the various components of the plasma delivers to the treated surfaces; what is the gas flow pattern? The focus is on two devices, namely the capacitive coupled plasma jet and the microwave surface wave sustained discharge. The devices are representatives of the so called cold atmospheric plasmas (CAPs). These are discharges characterized by low gas temperature - less than 40°C at the point of application - and non-equilibrium chemistry.

Collision effects on propagation characteristics of electromagnetic waves in a sub-wavelength plasma slab of partially ionized dense plasmas

Science.gov (United States)

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.

Plasma-neutral gas interaction in a tokamak divertor: effects of hydrogen molecules and plasma recombination

International Nuclear Information System (INIS)

Krasheninnikov, S.I.; Pigarov, A.Yu.; Soboleva, T.K.; Sigmar, D.J.

1997-01-01

We investigate the influence of hydrogen molecules on plasma recombination using a collisional-radiative model for multispecies hydrogen plasmas and tokamak detached divertor parameters. The rate constant found for molecular activated recombination of a plasma can be as high as 2 x 10 -10 cm 3 /s, confirming our pervious estimates. We investigate the effects of hydrogen molecules and plasma recombination on self-consistent plasma-neutral gas interactions in the recycling region of a tokamak divertor. We treat the plasma flow in a fluid approximation retaining the effects of plasma recombination and employing a Knudsen neutral transport model for a 'gas box' divertor geometry. For the model of plasma-neutral interactions we employ we find: (a) molecular activated recombination is a dominant channel of divertor plasma recombination; and (b) plasma recombination is a key element leading to a decrease in the plasma flux onto the target and substantial plasma pressure drop which are the main features of detached divertor regimes. (orig.)

Density and field effect on electron-ion collision cross-sections in hot dense plasma

International Nuclear Information System (INIS)

Gaufridy de Dortan, F. de

2003-03-01

Collisional excitation cross-sections are essential for the modeling of the properties of non equilibrium plasmas. There has been a lot of work on electron impact excitation of isolated ions, but in dense plasmas, neighboring particles are expected to widely disturb these electron transitions in atoms. Plasma modeling through a radially perturbed potential has already been done but is not satisfactory as it does not account for levels degeneracy breaking and its consequences. Introduction of a quasistatic electric micro-field of neighboring ions allows us to break spherical symmetry. Our original theoretical study has given birth to a numerical code that accurately computes collisional strengths and rates (in the Distorted Waves approach) in atoms submitted to a realistic micro-field. Hydrogen- and helium-like aluminium is studied. Stark mixing widely increases rates of transitions from high l levels and forbidden transitions are field-enhanced by many orders of magnitude until they reach allowed ones. Eventually, we conduct an elementary stationary collisional radiative study to investigate field-enhancement effects on corresponding line shapes. In cases we study (aluminium, hydrogen- and helium-like) we find a relatively weak increase of K-shell line broadening

On calculation of collisional angular-momentum mixing of Rydberg states

International Nuclear Information System (INIS)

Oreg, J.; Strauss, M.; Hazak, G.

1983-09-01

Exact solutions of the coupled differential equations for collisional mixing probabilities are presented for a sodium-helium system. The results show that complete mixing is not reached in this model. The main contribution to the collisional mixing cross-section of the sodium ''nd'' state comes from impact parameters b within the range n 2 2 . The total cross-sections obtained are in agreement with the experiment. (author)

Industrial applications of low-temperature plasma physics

International Nuclear Information System (INIS)

Chen, F.F.

1995-01-01

The application of plasma physics to the manufacturing and processing of materials may be the new frontier of our discipline. Already partially ionized discharges are used in industry, and the performance of plasmas has a large commercial and technological impact. However, the science of low-temperature plasmas is not as well developed as that of high-temperature, collisionless plasmas. In this paper several major areas of application are described and examples of forefront problems in each are given. The underlying thesis is that gas discharges have evolved beyond a black art, and that intellectually challenging problems with elegant solutions can be found. copyright 1995 American Institute of Physics

Collisional redistribution effects on x-ray laser saturation behavior

International Nuclear Information System (INIS)

Koch, J.A.; MacGowan, B.J.; Da Silva, L.B.; Matthews, D.J.; Lee, R.W.; London, R.A.; Mrowka, S.; Underwood, J.H.; Batson, P.J.

1994-06-01

We recently published a detailed summary of our experimental and theoretical research on Ne-like Se x-ray laser line widths, and one of our conclusions was that collisional redistribution rates are likely to have an effect on the saturation behavior of the 206.4 angstrom Se x-ray laser. In this paper we focus on the effects of collisional redistribution on x-ray laser gain coefficients, and discuss ways of including these effects in existing laser line- transfer models

Statistical moments of the angular spectrum of normal waves in a turbulent collisional magnetized plasma

International Nuclear Information System (INIS)

Aistov, A.V.; Gavrilenko, V.G.

1996-01-01

The normal incidence of a small-amplitude electromagnetic wave upon a semi-infinite turbulent collisional plasm with an oblique external magnetic field is considered. Within a small-angle-scattering approximation of the radiative transport theory, a system of differential equations is derived for statistical moments of the angular power spectrum of radiation. The dependences of the spectrum centroid, dispersion, and asymmetry on the depth of penetration are studied numerically. The nonmonotonic behavior of the dispersion is revealed, and an increase in the spectrum width with absorption anisotropy is found within some depth interval. It is shown that, at large depths, the direction of the displacement of the spectrum centroid, does not always coincide with the direction of minimum absorption

Proceedings of the 3rd US-Japan Workshop on Plasma Polarization Spectroscopy

International Nuclear Information System (INIS)

Beiersdorfer, P; Flyimoto, T

2002-01-01

The third US-Japan Workshop on Plasma Polarization Spectroscopy was held at the Lawrence Livermore National Laboratory in Livermore, California, on June 18-21, 2001. The talks presented at this workshop are summarized in these proceedings. The papers cover both experimental investigation and applications of plasma polarization spectroscopy as well as the theoretical foundation and formalisms to understand and describe the polarization phenomena. The papers give an overview of the history of plasma polarization spectroscopy, derive the formal aspects of polarization spectroscopy, including the effects of electric and magnetic fields, discuss spectra perturbed by intense microwave fields, charge exchange, and dielectronic recombination, and present calculations of various collisional excitation and ionization cross sections and the modeling of plasma polarization spectroscopy phenomena. Experimental results are given from the WT-3 tokamak, the MST reverse field pinch, the Large Helical Device, the GAMMA 10 mirror machine, the Nevada Terrawatt Facility, the Livermore EBIT-II electron beam ion trap, and beam-foil spectroscopy. In addition, results were presented from studies of several laser-produced plasma experiments and new instrumental techniques were demonstrated

The application of laser plasma in ophthalmology

International Nuclear Information System (INIS)

He Yujiang; Luo Le; Sun Yabing

2000-01-01

The production and development of laser plasma are introduced, and the contribution of laser biomedicine and laser plasma technology to ophthalmology is analyzed. The latest three progresses (laser photocoagulation, photo-refractive keratotomy and laser iridectomy) of laser plasma applications in ophthalmology are presented

Collisional effect on lower hybrid waves instability in a dusty plasma ...

African Journals Online (AJOL)

The effect of particle collisions on lower hybrid modes in a dusty plasma is studied. The dispersion relation derived from fluid theory is numerically solved for plasma parameters relevant to determine the modification in wave propagation due to collisions. This study is relevant to the earth's lower atmosphere, in particular, the ...

Temperature and impurity transport studies of heated tokamak plasmas by means of a collisional-radiative model of x-ray emission from Mo30+ to Mo39+

International Nuclear Information System (INIS)

Pacella, D.; Fournier, K. B.; Zerbini, M.; Finkenthal, M.; Mattioli, M.; May, M. J.; Goldstein, W. H.

2000-01-01

This work presents and interprets, by means of detailed atomic calculations, observations of L-shell (n=3→n=2) transitions in highly ionized molybdenum, the main intrinsic heavy impurity in the Frascati tokamak upgrade plasmas. These hot plasmas were obtained by additional electron cyclotron resonance heating (ECRH), at the frequency of 140 Ghz, during the current ramp-up phase of the discharge. Injecting 400 kW on axis and 800 kW slightly off axis, the peak central electron temperature reached 8.0 and 7.0 keV, respectively, for a time much longer than the ionization equilibrium time of the molybdenum ions. X-ray emissions from rarely observed high charge states, Mo 30+ to Mo 39+ , have been studied with moderate spectral resolution (λ/Δλ∼150) and a time resolution of 5 ms. A sophisticated collisional-radiative model for the study of molybdenum ions in plasmas with electron temperature in the range 4-20 keV is presented. The sensitivity of the x-ray emission to the temperature and to impurity transport processes is discussed. This model has been then used to investigate two different plasma scenarios. In the first regime the ECRH heating occurs on axis during the current ramp up phase, when the magnetic shear is evolving from negative to zero up to the half radius. The spectrum is well reproduced with the molybdenum ions in coronal equilibrium and with a central impurity peaking. In the second regime, at the beginning of the current flat top when magnetic shear is monotonic and sawtoothing activity is appearing, the lowest charge states (Mo 33+ to Mo 30+ ), populated off axis, are affected by anomalous transport and the total molybdenum profile is found to be flat up to the half radius. We conclude with the presentation of ''synthetic spectra'' computed for even higher temperature plasmas that are expected in future experiments with higher ECRH power input. (c) 2000 The American Physical Society

Amplification of magnetic modes in laser-created plasmas

International Nuclear Information System (INIS)

Matte, J.P.; Bendib, A.; Luciani, J.F.

1987-01-01

The amplification of magnetic (Weibel) modes in laser-plasma interaction is investigated by use of unperturbed distribution functions given by Fokker-Planck simulations and a dispersion relation valid for all collisionality regimes. In the five cases studied, a strongly growing mode is found in the underdense plasma, where v-bar/sub x/ 2 2 , and the usual slowly growing one in the overdense plasma. The first mode grows convectively outwards by more than 10 4 . The convection velocities are found to be very different from Nernst values

Ion trapping within the dust grain plasma sheath

International Nuclear Information System (INIS)

Jovanovic, D.; Shukla, P.K.

2002-01-01

One of the most important and still unresolved problems in the physics of dusty plasmas is the determination of the dust charge. The grains are not directly accessible to measurements and it is necessary to have a reliable theoretical model of the electron and ion dynamics inside the Debye sphere for the interpretation of the relevant experimental data, which include also the effects of the surrounding electron and ion clouds. Recent computer simulations [6] and laboratory experiments [9] indicate that the plasma sheath is dominated by trapped ions, orbiting the grain on closed trajectories at distances smaller than the Debye radius, that cannot be accounted for by the classical theories. We present the first analytical, fully self-consistent, calculations of the electrostatic shielding of a charged dust grain in a collisional plasma. In the regime when the mean free path for the ion-dust collisions is larger than that for the ion-neutral collisions, we solve the kinetic equation for the ions, coupled with Boltzmann distributed electrons and Poisson's equation. The ion velocity distribution function, in the form of a spherically symmetric ion hole, is found to be anisotropic in the presence of charge-exchange collisions. The number of trapped ions and their spatial distribution are determined from the interplay between the collective plasma interaction and the collisional trapping/de-trapping. The stationary state results from the self-tuning of the trapped ion density by the feedback based on the nonlocality of the collisional integral, and on the ion mixing in the radial direction along elongated orbits. Our results confirm the existence of a strong Debye shielding of the dust charge, allowing also the over-population of the trapped ion distribution (ion hump)

Application of plasma technology to nuclear engineering fields

International Nuclear Information System (INIS)

Suzuki, Masaaki; Akatsuka, Hiroshi

1996-01-01

In order to discuss about the application of the plasma technology to nuclear engineering fields, we mention two subjects, the oxygenation of metal chloride waste by oxygen plasma and the characterization of fine particles generated in the plasma process. Through the experimental results of two subjects, both of the advantage and the disadvantage of the plasma technology and their characteristics are shown and discussed. The following conclusions are obtained. The reactive plasma is effective to oxygenate the chloride wastes. The particle generation which is one of the disadvantages must not be specialized and its characteristics can be estimated. Consequently, the plasma technology should be applicable to nuclear engineering fields adopting its advantage and overcoming its disadvantage. (author)

Fundamental Processes in Plasmas

Energy Technology Data Exchange (ETDEWEB)

Driscoll, Charles Fred [Univ. of California, San Diego, CA (United States)

2017-11-03

This Final Technical Report gives brief summaries of the plasma physics results developed under DOE grant DE-SC0002451; and provides reference to the published journal articles giving full scientific descriptions. General topics include 1) cyclotron modes; 2) damping and decay of Langmuir modes; 3) 2D vortex dynamics and diocotron modes; 4) separatrix-induced transport and damping; and 5) long-range collisional velocity slowing.

Spectroscopic and Collisional Data for Tungsten from 1 eV to 20 keV. Summary Report of the Final Research Coordination Meeting

International Nuclear Information System (INIS)

Chung, H.-K.; Beiersdorfer, P.; Müller, A.; Ralchenko, Yu.; Braams, B. J.

2014-12-01

The final Research Coordination Meeting of a coordinated research project (CRP) on spectroscopic and collisional data for tungsten ions in fusion plasma was held at IAEA Headquarters with 17 external experts representing 14 research groups and staff from the International Atomic Energy Agency. Participants summarized their research during the CRP and made plans for a final report. The proceedings and conclusions of the meeting are summarized here. (author)

Biomimetic architectures by plasma processing fabrication and applications

CERN Document Server

Chattopadhyay, Surojit

2014-01-01

Photonic structures in the animal kingdom: valuable inspirations for bio-mimetic applications. Moth eye-type anti-reflecting nanostructures by an electron cyclotron resonance plasma. Plasma-processed biomimetic nano/microstructures. Wetting properties of natural and plasma processed biomimetic surfaces. Biomimetic superhydrophobic surface by plasma processing. Biomimetic interfaces of plasma modified titanium alloy.

Laser diagnostics of atomic hydrogen and oxygen production in rf and microwave plasma discharges

International Nuclear Information System (INIS)

Preppernau, B.L.

1993-01-01

The research for this thesis involved the application of two-photon allowed laser-induced fluorescence (TALIF) to the study of atomic hydrogen and oxygen production in industrial scale radio-frequency and microwave plasma discharge apparatus. Absolute atomic hydrogen concentration profiles were measured in a Gaseous Electronics Conference Reference Cell installed at Wright-Patterson AFB, Ohio operating with a simple H 2 discharge. Two-dimensional atomic hydrogen concentration profiles were also measured in an ASTEX HPMM microwave plasma diamond deposition reactor during actual diamond growth. In addition absolute atomic oxygen concentrations were measured in the ASTEX system. Particular attention as paid to refining the concentration calibration technique and in determining a correction to account for the collisional quenching of excited state fluorescence in high pressure gases

Revisited neoclassical transport theory for steep, collisional plasma edge profiles

International Nuclear Information System (INIS)

Rogister, A.L.

1994-01-01

Published neoclassical results are misleading as concerns the plasma edge for they do not adequately take the peculiar local conditions into account, in particular the fact that the density and temperature variation length-scales are quite small. Coupled novel neoclassical equations obtain, not only for the evolution of the density and temperatures, but also for the radial electric field and the evolution of the parallel ion momentum: gyro-stresses and inertia indeed upset the otherwise de facto ambipolarity of particle transport and a radial electric field necessarily builds up. The increased nonlinear character of these revisited neoclassical equations widens the realm of possible plasma behaviors. (author)

Introduction to Plasma Technology Science, Engineering and Applications

CERN Document Server

Harry, John Ernest

2011-01-01

Written by a university lecturer with more than forty years experience in plasma technology, this book adopts a didactic approach in its coverage of the theory, engineering and applications of technological plasmas. The theory is developed in a unified way to enable brevity and clarity, providing readers with the necessary background to assess the factors that affect the behavior of plasmas under different operating conditions. The major part of the book is devoted to the applications of plasma technology and their accompanying engineering aspects, classified by the various pressure and densit

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.

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.

Analysis of Atomic Electronic Excitation in Nonequilibrium Air Plasmas

International Nuclear Information System (INIS)

He Xin; Jia Hong-Hui; Yin Hong-Wei; Zhang Hai-Liang; Chang Sheng-Li; Yang Jun-Cai; Dang Wei-Hua

2014-01-01

Electronic excitation of atoms is studied in nonequilibrium air plasmas with the electronic temperature between 8000 K and 20000 K. By using the modified Saha—Boltzmann equation, our simplified method takes into account significant radiative processes and strong self-absorption of the vacuum ultraviolet lines. Calculations are carried out at three trajectory points of the Fire II flight experiment. Good agreement with the detailed collisional-radiative model is obtained, and the performance of this method in applications to highly nonequilibrium conditions is better than Park's quasi-steady-state model and Spradian-9.0. A short discussion on the influence of optical thickness of the vacuum ultraviolet radiation is also given. It costs about 2.9 ms on the average to solve one cell of the shock layer on a low cost computer, which shows that the present method is fast and efficient. (physics of gases, plasmas, and electric discharges)

Ion mobility studies of carbohydrates as group I adducts: isomer specific collisional cross section dependence on metal ion radius.

Science.gov (United States)

Huang, Yuting; Dodds, Eric D

2013-10-15

Carbohydrates play numerous critical roles in biological systems. Characterization of oligosaccharide structures is essential to a complete understanding of their functions in biological processes; nevertheless, their structural determination remains challenging in part due to isomerism. Ion mobility spectrometry provides the means to resolve gas phase ions on the basis of their shape-to-charge ratios, thus providing significant potential for separation and differentiation of carbohydrate isomers. Here, we report on the determination of collisional cross sections for four groups of isomeric carbohydrates (including five isomeric disaccharides, four isomeric trisaccharides, two isomeric pentasaccharides, and two isomeric hexasaccharides) as their group I metal ion adducts (i.e., [M + Li](+), [M + Na](+), [M + K](+), [M + Rb](+), and [M + Cs](+)). In all, 65 collisional cross sections were measured, the great majority of which have not been previously reported. As anticipated, the collisional cross sections of the carbohydrate metal ion adducts generally increase with increasing metal ion radius; however, the collisional cross sections were found to scale with the group I cation size in isomer specific manners. Such measurements are of substantial analytical value, as they illustrate how the selection of charge carrier influences carbohydrate ion mobility determinations. For example, certain pairs of isomeric carbohydrates assume unique collisional cross sections upon binding one metal ion, but not another. On the whole, these data suggest a role for the charge carrier as a probe of carbohydrate structure and thus have significant implications for the continued development and application of ion mobility spectrometry for the distinction and resolution of isomeric carbohydrates.

Low temperature plasma technology methods and applications

CERN Document Server

Chu, Paul K

2013-01-01

Written by a team of pioneering scientists from around the world, Low Temperature Plasma Technology: Methods and Applications brings together recent technological advances and research in the rapidly growing field of low temperature plasmas. The book provides a comprehensive overview of related phenomena such as plasma bullets, plasma penetration into biofilms, discharge-mode transition of atmospheric pressure plasmas, and self-organization of microdischarges. It describes relevant technology and diagnostics, including nanosecond pulsed discharge, cavity ringdown spectroscopy, and laser-induce

Wills Plasma Physics Department annual progress report 1982

International Nuclear Information System (INIS)

1982-01-01

Progress in the experimental program using the research tokamak TORTUS is presented. The main thrust of the program is the study of the characteristics of hydromagnetic waves in tokamak plasmas and in the use of such waves in r.f. heating. Work on runaway electron production, on wave propagation in collisional plasmas and on hydromagnetic shock wave studies is reported. Diagnostic techniques and equipment described include a laser interferometer system and techniques based on the observation of resonance fluorescence and near-resonant scattering of a laser beam from atomic species in a plasma

Plasma spray technology process parameters and applications

International Nuclear Information System (INIS)

Sreekumar, K.P.; Karthikeyan, J.; Ananthapadmanabhan, P.V.; Venkatramani, N.; Chatterjee, U.K.

1991-01-01

The current trend in the structural design philosophy is based on the use of substrate with the necessary mechanical properties and a thin coating to exhibit surface properties. Plasma spray process is a versatile surface coating technique which finds extensive application in meeting advance technologies. This report describes the plasma spray technique and its use in developing coatings for various applications. The spray system is desribed in detail including the different variables such as power input to the torch, gas flow rate, powder properties, powder injection, etc. and their interrelation in deciding the quality of the coating. A brief write-up on the various plasma spray coatings developed for different applications is also included. (author). 15 refs., 15 figs., 2 tabs

Parallel Transport and Profile of Boundary Plasma with a Low Recycling Wall

Energy Technology Data Exchange (ETDEWEB)

Tang, X.; Guo, Z., E-mail: xtang@lanl.gov [Los Alamos National Laboratory, Los Alamos (United States)

2012-09-15

Full text: Reduction of wall recycling by, for example, a flowing liquid surface at the divertor and first wall, holds the promise of accessing the distinct tokamak reactor operational mode with boundary plasmas of high temperature and low density. Earlier work has indicated that such a boundary plasma would reduce the temperature gradient across the entire plasma and hence remove the primary micro-instability drive responsibly for anomalous particle and energy transport. Here we present a systematic study solving the kinetic equations both analytically and numerically, with and without Coulomb collision. The distinct roles of magnetic field strength modulation and the ambipolar electric field on the electron and ion distribution functions are clarified. The resulting behavior on plasma profile and parallel heat flux, which are often surprising and counter the expectations from the collisional fluid models, on which previous work were based, are explained both intuitively and with a contrast between analytical calculation and numerical simulations. The transport-induced plasma instabilities, and their essential role in maintaining ambipolarity, are clarified, along with the subtle effect of Coulomb collision on electron temperature and wall potential as small but finite collisionality is taken into account. (author)

Computer models for kinetic equations of magnetically confined plasmas

International Nuclear Information System (INIS)

Killeen, J.; Kerbel, G.D.; McCoy, M.G.; Mirin, A.A.; Horowitz, E.J.; Shumaker, D.E.

1987-01-01

This paper presents four working computer models developed by the computational physics group of the National Magnetic Fusion Energy Computer Center. All of the models employ a kinetic description of plasma species. Three of the models are collisional, i.e., they include the solution of the Fokker-Planck equation in velocity space. The fourth model is collisionless and treats the plasma ions by a fully three-dimensional particle-in-cell method

Oxygen auroral transition laser system excited by collisional and photolytic energy transfer

International Nuclear Information System (INIS)

Murray, J.R.; Powell, H.T.; Rhodes, C.K.

1975-06-01

The properties of laser media involving the auroral transition of atomic oxygen and analogous systems are examined. A discussion of the atomic properties, collisional mechanisms, excitation processes, and collisionally induced radiative phenomena is given. Crossing phenomena play a particularly important role in governing the dynamics of the medium

Optical diagnostics of atmospheric pressure air plasmas

International Nuclear Information System (INIS)

Laux, C O; Spence, T G; Kruger, C H; Zare, R N

2003-01-01

Atmospheric pressure air plasmas are often thought to be in local thermodynamic equilibrium owing to fast interspecies collisional exchange at high pressure. This assumption cannot be relied upon, particularly with respect to optical diagnostics. Velocity gradients in flowing plasmas and/or elevated electron temperatures created by electrical discharges can result in large departures from chemical and thermal equilibrium. This paper reviews diagnostic techniques based on optical emission spectroscopy and cavity ring-down spectroscopy that we have found useful for making temperature and concentration measurements in atmospheric pressure plasmas under conditions ranging from thermal and chemical equilibrium to thermochemical nonequilibrium

Study of a continuous plasma generated by electron bombardment and its mixing with a laser induced plasma. Influence of collisions on resonance cone phenomenon

International Nuclear Information System (INIS)

Besuelle, E.

1997-01-01

This thesis deals with three different fields of plasma physics. In the first part, we studied free expansion of an ionised uranium vapour generated in an electron beam evaporator. The electron temperature and the electron density of the expanding plasma have been measured by a Langmuir probe. The experimental results have been compared with the ones obtained by numerical simulation using a fluid code. The calculated points are in the error bars. We observe that there are two electron populations with different temperatures, which undergo a mixing during the plasma expansion. The neutral density influence on the electron temperature by collisional relaxation is also studied. The second part deals with a plasma diagnostic which can replace Langmuir probe in the case of a cold magnetized plasma: the resonance cone phenomenon. After recalling the wave propagation theory in a cold plasma, we introduce a new calculation of the potential radiated by an antenna in a collisional magnetized plasma. The domain where the resonance cone exists in considerably reduced because of collisions. More of that, the cone angle is reduced by this phenomenon too. The experiments performed show that we must take into account a wave turbulence phenomenon to explain the High collision frequency that we observe. The third part is about the study of the expansion of a plasma into another one. We solve this problem with fluid codes and Particle-In-Cell (PIC) code. THe electron families have a counter stream motion locally. Then, we study the electrostatic extraction of two plasmas-one pulsed, one continuous-in which we observe electron unfurling. (author)

COLLISIONALLY BORN FAMILY ABOUT 87 SYLVIA

International Nuclear Information System (INIS)

Vokrouhlicky, David; Nesvorny, David; Bottke, William F.; Morbidelli, Alessandro

2010-01-01

There are currently more than 1000 multi-opposition objects known in the Cybele population, adjacent and exterior to the asteroid main belt, allowing a more detailed analysis than was previously possible. Searching for collisionally born clusters in this population, we find only one statistically robust case: a family of objects about (87) Sylvia. We use a numerical model to simulate the Sylvia family long-term evolution due to gravitational attraction from planets and thermal (Yarkovsky) effects and to explain its perturbed structure in the orbital element space. This allows us to conclude that the Sylvia family must be at least several hundreds of million years old, in agreement with evolutionary timescales of Sylvia's satellite system. We find it interesting that other large Cybele-zone asteroids with known satellites-(107) Camilla and (121) Hermione-do not have detectable families of collisional fragments about them (this is because we assume that binaries with large primary and small secondary components are necessarily impact generated). Our numerical simulations of synthetic clusters about these asteroids show they would suffer a substantial dynamical depletion by a combined effect of diffusion in numerous weak mean-motion resonances and Yarkovsky forces provided their age is close to ∼4 billion years. However, we also believe that a complete effacement of these two families requires an additional component, very likely due to resonance sweeping or other perturbing effects associated with the late Jupiter's inward migration. We thus propose that both Camilla and Hermione originally had their collisional families, as in the Sylvia case, but they lost them in an evolution that lasted a billion years. Their satellites are the only witnesses of these effaced families.

Pair plasma relaxation time scales.

Science.gov (United States)

Aksenov, A G; Ruffini, R; Vereshchagin, G V

2010-04-01

By numerically solving the relativistic Boltzmann equations, we compute the time scale for relaxation to thermal equilibrium for an optically thick electron-positron plasma with baryon loading. We focus on the time scales of electromagnetic interactions. The collisional integrals are obtained directly from the corresponding QED matrix elements. Thermalization time scales are computed for a wide range of values of both the total-energy density (over 10 orders of magnitude) and of the baryonic loading parameter (over 6 orders of magnitude). This also allows us to study such interesting limiting cases as the almost purely electron-positron plasma or electron-proton plasma as well as intermediate cases. These results appear to be important both for laboratory experiments aimed at generating optically thick pair plasmas as well as for astrophysical models in which electron-positron pair plasmas play a relevant role.

Fluctuations in collisional plasma in the presence of an external electric field

International Nuclear Information System (INIS)

Momot, A. I.; Zagorodny, A. G.

2011-01-01

The theory of large-scale fluctuations in a plasma is used to calculate the correlations functions of electron and ion density with regard to particle collisions described within the Bhatnagar-Gross-Krook (BGK) model and the presence of a constant external electric field. The changes of plasma particle distribution functions due to an external electric field and their influence on the plasma dielectric response are taken into account. The dispersion relations for longitudinal waves in such a plasma are studied in details. It is shown that external electric field can lead to the ion-acoustic wave instability and anomalous growth of the fluctuation level. Detailed numerical studies of the general relations for electron number density fluctuations are performed and the effect of external electric field on the fluctuation spectra is studied.

Optogalvanic monitoring of collisional transfer of laser excitation energy in a neon RF plasma

International Nuclear Information System (INIS)

Armstrong, T.D.

1994-01-01

The optogalvanic signals produced by pulsed laser excitation of 1s5--2p8 and 1s5-2p9 (Paschen notation) transition by a ∼29 MHz radiofrequency (rf) discharge at ∼5 torr have been investigated. The optogalvanic signal produced by 1s5-2p9 excitations indicates that there is transfer of energy from the 2p9 state to some other state. The state to which this energy is transferred is believed to be mainly the 2p8 state because of the very small energy gap between the 2p9 and 2p8 states. To verify this transfer, the 1s5-2p8 transition was investigated. The similarity of the temporal profiles of the optogalvanic signals in both excitations confirms the collisional transfer of laser excitation energy from 2p9 to 2p8

Spectroscopic and Collisional Data for Tungsten from 1 eV to 20 keV. Summary Report of the First Research Coordination Meeting

International Nuclear Information System (INIS)

Braams, B.J.; Chung, H.-K.

2012-06-01

Experts representing 14 research groups and the International Atomic Energy Agency met at IAEA Headquarters for the first research coordination meeting of a coordinated research project (CRP) on spectroscopic and collisional data for tungsten ions in fusion plasma. Participants presented their research following which a work plan was developed for the remainder of the CRP and outstanding data needs were identified. The proceedings and conclusions of the meeting are summarized here. (author)

Study of a continuous plasma generated by electron bombardment and its mixing with a laser induced plasma. Influence of collisions on resonance cone phenomenon; Contribution a l`etude d`un plasma cree de facon continue par bombardement electronique et de son melange avec un photo-plasma pulse. Influence des collisions sur les cones de resonance

Energy Technology Data Exchange (ETDEWEB)

Besuelle, E.

1997-02-25

This thesis deals with three different fields of plasma physics. In the first part, we studied free expansion of an ionised uranium vapour generated in an electron beam evaporator. The electron temperature and the electron density of the expanding plasma have been measured by a Langmuir probe. The experimental results have been compared with the ones obtained by numerical simulation using a fluid code. The calculated points are in the error bars. We observe that there are two electron populations with different temperatures, which undergo a mixing during the plasma expansion. The neutral density influence on the electron temperature by collisional relaxation is also studied. The second part deals with a plasma diagnostic which can replace Langmuir probe in the case of a cold magnetized plasma: the resonance cone phenomenon. After recalling the wave propagation theory in a cold plasma, we introduce a new calculation of the potential radiated by an antenna in a collisional magnetized plasma. The domain where the resonance cone exists in considerably reduced because of collisions. More of that, the cone angle is reduced by this phenomenon too. The experiments performed show that we must take into account a wave turbulence phenomenon to explain the High collision frequency that we observe. The third part is about the study of the expansion of a plasma into another one. We solve this problem with fluid codes and Particle-In-Cell (PIC) code. THe electron families have a counter stream motion locally. Then, we study the electrostatic extraction of two plasmas-one pulsed, one continuous-in which we observe electron unfurling. (author).

Partial local thermal equilibrium in a low-temperature hydrogen plasma

International Nuclear Information System (INIS)

Hey, J.D.; Chu, C.C.; Rash, J.P.S.

1999-01-01

If the degree of ionisation is sufficient, competition between de-excitation by electron collisions and radiative decay determines the smallest principal quantum number (the so-called 'thermal limit') above which partial local thermodynamic equilibrium (PLTE) holds under the particular conditions of electron density and temperature. The LTE (PLTE) criteria of Wilson (JQSRT 1962;2:477-90), Griem (Phys Rev 1963;131:1170-6; Plasma Spectroscopy. New York: McGraw-Hill, 1964), Drawin (Z Physik 1969;228: 99-119), Hey (JQSRT 1976;16:69-75), and Fujimoto and McWhirter (Phys Rev A 1990;42:6588-601) are examined as regards their applicability to neutral atoms. For these purposes, we consider for simplicity an idealised, steady-state, homogeneous and primarily optically thin plasma, with some additional comments and numerical estimates on the roles of opacity and of atom-atom collisions. Particularly for atomic states of lower principal quantum number, the first two of the above criteria should be modified quite appreciably before application to neutral radiators in plasmas of low temperature, because of the profoundly different nature of the near-threshold collisional cross-sections for atoms and ions, while the most recent criterion should be applied with caution to PLTE of atoms in cold plasmas in ionisation balance. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Plasma response to electron energy filter in large volume plasma device

International Nuclear Information System (INIS)

Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K.

2013-01-01

An electron energy filter (EEF) is embedded in the Large Volume Plasma Device plasma for carrying out studies on excitation of plasma turbulence by a gradient in electron temperature (ETG) described in the paper of Mattoo et al. [S. K. Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. In this paper, we report results on the response of the plasma to the EEF. It is shown that inhomogeneity in the magnetic field of the EEF switches on several physical phenomena resulting in plasma regions with different characteristics, including a plasma region free from energetic electrons, suitable for the study of ETG turbulence. Specifically, we report that localized structures of plasma density, potential, electron temperature, and plasma turbulence are excited in the EEF plasma. It is shown that structures of electron temperature and potential are created due to energy dependence of the electron transport in the filter region. On the other hand, although structure of plasma density has origin in the particle transport but two distinct steps of the density structure emerge from dominance of collisionality in the source-EEF region and of the Bohm diffusion in the EEF-target region. It is argued and experimental evidence is provided for existence of drift like flute Rayleigh-Taylor in the EEF plasma

Quasi-molecular processes in dense plasmas

International Nuclear Information System (INIS)

Younger, S.M.

1991-01-01

Quasi-molecular phenomena occur in dense plasmas when the interatomic spacing is comparable to the characteristic wavelength of the electrons. If the electronic states are bound, covalent orbitals arise with different excitation energies, radiative rates, and collisional rates than for isolated ions. For continuum electrons, charge localization near transient clusters of nuclei can influence many scattering and transport processes. We identify several novel consequences of quasi-molecular phenomena in plasmas and give a possible explanation of high energy features associated with helium-like emissions lines observed in recent inertial fusion experiments. 7 refs

Electron density and plasma dynamics of a colliding plasma experiment

Energy Technology Data Exchange (ETDEWEB)

Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J. [Plasma Physics Group, Institute of Applied Physics, Goethe University, 60438 Frankfurt am Main (Germany)

2016-07-15

We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

Ion-sound oscillations in strongly non-isotherm weakly ionized nonuniform hydrogen plasma

International Nuclear Information System (INIS)

Leleko, Ya.F.; Stepanov, K.N.

2010-01-01

A stationary distribution of strongly non-isotherm weakly ionized hydrogen plasma parameters is obtained in the hydrodynamic approximation in a quasi neutrality region in the transient layer between the plasma and dielectric taking the ionization, charge exchange, diffusion, viscosity, and a self-consistent field potential distribution. The ion-sound oscillation frequency and the collisional damping decrement as functions of the wave vector in the plasma with the obtained parameters are found in the local approximation.

Diagnostics of atmospheric pressure air plasmas

International Nuclear Information System (INIS)

Laux, C.O.; Kruger, C.H.; Zare, R.N.

2001-01-01

Atmospheric pressure air plasmas are often thought to be in Local Thermodynamics Equilibrium (LTE) owing to fast interspecies collisional exchanges at high pressure. As will be seen here, this assumption cannot be relied upon, particularly with respect to optical diagnostics. Large velocity gradients in flowing plasmas and/or elevated electron temperatures created by electrical discharges can result in large departures from chemical and thermal equilibrium. Diagnostic techniques based on optical emission spectroscopy (OES) and Cavity Ring-Down Spectroscopy (CRDS) have been developed and applied at Stanford University to the investigation of atmospheric pressure plasmas under conditions ranging from thermal and chemical equilibrium to thermochemical nonequilibrium. This article presents a review of selected temperature and species concentration measurement techniques useful for the study of air and nitrogen plasmas

Microwave imaging for plasma diagnostics and its applications

International Nuclear Information System (INIS)

Mase, A.; Kogi, Y.; Ito, N.

2007-01-01

Microwave to millimeter-wave diagnostic techniques such as interferometry, reflectometry, scattering, and radiometry have been powerful tools for diagnosing magnetically confined plasmas. Important plasma parameters were measured to clarify the physics issues such as stability, wave phenomena, and fluctuation-induced transport. Recent advances in microwave and millimeter-wave technology together with computer technology have enabled the development of advanced diagnostics for visualization of 2D and 3D structures of plasmas. Microwave/millimeter-wave imaging is expected to be one of the most promising diagnostic methods for this purpose. We report here on the representative microwave diagnostics and their industrial applications as well as application to magnetically-confined plasmas. (author)

Cancellation of collisional frequency shifts in optical lattice clocks with Rabi spectroscopy

International Nuclear Information System (INIS)

Lee, Sangkyung; Park, Chang Yong; Lee, Won-Kyu; Yu, Dai-Hyuk

2016-01-01

We analyze both the s- and p-wave collision induced frequency shifts and propose an over-π pulse scheme to cancel the shifts in optical lattice clocks interrogated by a Rabi pulse. The collisional frequency shifts are analytically solved as a function of the pulse area and the inhomogeneity of the Rabi frequencies. Experimentally measured collisional frequency shifts in an Yb optical lattice clock are in good agreement with the analytical calculations. Based on our analysis, the over-π pulse combined with a small inhomogeneity below 0.1 allows a fractional uncertainty on a level of 10 −18 in both Sr and Yb optical lattice clocks by canceling the collisional frequency shift. (paper)

SCRIC: a code dedicated to the detailed emission and absorption of heterogeneous NLTE plasmas; application to xenon EUV sources

International Nuclear Information System (INIS)

Gaufridy de Dortan, F. de

2006-01-01

Nearly all spectral opacity codes for LTE and NLTE plasmas rely on configurations approximate modelling or even supra-configurations modelling for mid Z plasmas. But in some cases, configurations interaction (either relativistic and non relativistic) induces dramatic changes in spectral shapes. We propose here a new detailed emissivity code with configuration mixing to allow for a realistic description of complex mid Z plasmas. A collisional radiative calculation. based on HULLAC precise energies and cross sections. determines the populations. Detailed emissivities and opacities are then calculated and radiative transfer equation is resolved for wide inhomogeneous plasmas. This code is able to cope rapidly with very large amount of atomic data. It is therefore possible to use complex hydrodynamic files even on personal computers in a very limited time. We used this code for comparison with Xenon EUV sources within the framework of nano-lithography developments. It appears that configurations mixing strongly shifts satellite lines and must be included in the description of these sources to enhance their efficiency. (author)

Plasma oscillations and sound waves in collision-dominated two-component plasmas

International Nuclear Information System (INIS)

Hansen, J.P.; Sjoegren, L.

1982-01-01

Charge, mass, and electron density fluctuation spectra of strongly correlated, fully ionized two-component plasmas within the framework of the Mori--Zwanzig memory function formalism are analyzed. All dynamical correlation functions are expressed in terms of the memory functions of the ion and electron velocity autocorrelation functions by a generalized effective field approximation which preserves the exact initial values (i.e., static correlations). The theory reduces correctly to the mean field (or collisionless Vlasov) results in the weak coupling limit, and yields charge density fluctuation spectra in good agreement with available computer simulation data, as well as reasonable estimates of the transport coefficients. The collisional damping and frequency shift of the plasma oscillation mode are sizeable, even in the long wavelength limit. The theory also predicts the propagation of well-defined sound waves in dense plasmas in thermal equilibrium

Critical gradients and plasma flows in the edge plasma of Alcator C-Moda)

Science.gov (United States)

Labombard, B.; Hughes, J. W.; Smick, N.; Graf, A.; Marr, K.; McDermott, R.; Reinke, M.; Greenwald, M.; Lipschultz, B.; Terry, J. L.; Whyte, D. G.; Zweben, S. J.; Alcator C-Mod Team

2008-05-01

Recent experiments have led to a fundamental shift in our view of edge transport physics; transport near the last-closed flux surface may be more appropriately described in terms of a critical gradient phenomenon rather than a diffusive and/or convective paradigm. Edge pressure gradients, normalized by the square of the poloidal magnetic field strength, appear invariant in plasmas with the same normalized collisionality, despite vastly different currents and magnetic fields—a behavior that connects with first-principles electromagnetic plasma turbulence simulations. Near-sonic scrape-off layer (SOL) flows impose a cocurrent rotation boundary condition on the confined plasma when B ×∇B points toward the active x-point, suggesting a link to the concomitant reduction in input power needed to attain high-confinement modes. Indeed, low-confinement mode plasmas are found to attain higher edge pressure gradients in this configuration, independent of the direction of B, evidence that SOL flows may affect transport and "critical gradient" values in the edge plasma.

Probing the properties of nebular plasmas with optical and infrared spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Barlow, M. J. [Dept. of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

2012-05-25

A number of current developments arising from spectroscopic studies of ionized nebulae are reviewed. Until the past decade or so, such studies were generally confined to the analysis of recombination lines from hydrogen and helium, along with collisionally excited forbidden lines from second and third row elements in the periodic table. However, the advent of efficient detectors on 8m-class telescopes has enabled the detection of recombination lines from second and third row elements, along with collisionally excited lines from much less abundant species. Significant discrepancies have been found between ionic abundances derived from collisionally excited lines and those obtained for the same ions from their recombination lines. The existence of 'cold plasma' with T{sub e}{<=} 1000 K has been confirmed for a number of planetary nebulae. Optical and infrared collisionally excited ionic lines from a wide range of 'neutron-capture' elements from beyond the iron abundance peak have also been detected. There is a consequent need for new calculations and experimental measurements of the atomic data needed to interpret these observations.

ELM-Induced Plasma Wall Interactions in DIII-D

International Nuclear Information System (INIS)

Rudakov, D.L.; Boedo, J.A.; Yu, J.H.; Brooks, N.H.; Fenstermacher, M.E.; Groth, M.; Hollmann, E.M.; Lasnier, C.J.; McLean, A.G.; Moyer, R.A.; Stangeby, P.C.; Tynan, G.R.; Wampler, W.R.; Watkins, J.G.; West, W.P.; Wong, C.C.; Zeng, L.; Bastasz, R.J.; Buchenauer, D.; Whaley, J.

2008-01-01

Intense transient fluxes of particles and heat to the main chamber components induced by edge localized modes (ELMs) are of serious concern for ITER. In DIII-D, plasma interaction with the outboard chamber wall is studied using Langmuir probes and optical diagnostics including a fast framing camera. Camera data shows that ELMs feature helical filamentary structures localized at the low field side of the plasma and aligned with the local magnetic field. During the nonlinear phase of an ELM, multiple filaments are ejected from the plasma edge and propagate towards the outboard wall with velocities of 0.5-0.7 km/s. When reaching the wall, filaments result in 'hot spots'--regions of local intense plasma-material interaction (PMI) where the peak incident particle and heat fluxes are up to 2 orders of magnitude higher than those between ELMs. This interaction pattern has a complicated geometry and is neither toroidally nor poloidally symmetric. In low density/collisionality H-mode discharges, PMI at the outboard wall is almost entirely due to ELMs. In high density/collisionality discharges, contributions of ELMs and inter-ELM periods to PMI at the wall are comparable. A Midplane Material Evaluation Station (MiMES) has been recently installed in order to conduct in situ measurements of erosion/redeposition at the outboard chamber wall, including those caused by ELMs

EDITORIAL: Plasma jets and plasma bullets Plasma jets and plasma bullets

Science.gov (United States)

Kong, M. G.; Ganguly, B. N.; Hicks, R. F.

2012-06-01

to 1990 with only 31 papers per year on average, and a total of some 1300 papers, precedes a considerable growth of some 35-50% in research activity every five years, over the last 20 years or so. As shown in the table, the annual dissemination of the field is more than 1600 papers and the total number of papers is in excess of 20000. This upwards trajectory is typical of a strong and growing subject area in physical science, with considerable capacity in both fundamental science and applications. PeriodNumber of papersPapers per annum 1948-1990130031 1991-19952279456 1996-20003447689 2001-20054571914 2006-201066401328 2011 1658 In many of the dense plasma jets discussed above, strong physical forces generated by the plasma are often desired and this favours plasma generation at elevated gas pressure, including atmospheric pressure, which favours a high level of gas ionization. Historically it has been challenging to reduce and control the strong physical forces in high-pressure plasmas for applications where these are unwanted, for example, surface modification of polymeric sheets [5]. Indeed, there is a real need for a vast range of material processing applications at temperatures below 100oC (or below 400 K) and this favours atmospheric-pressure plasma jets sustained far from thermal equilibrium with the dissipated electrical energy largely used not in heat generation but in unleashing non-equilibrium chemical reactions. The long-standing difficulty of effectively controlling the level of gas ionization at atmospheric pressure was overcome by the technological breakthrough of achieving atmospheric-pressure glow discharges in the late 1980s [6]. A related challenge stemming from high collisionality of atmospheric-pressure plasmas (v >> ω0) means that large-area plasmas sustained between parallel-plate electrodes are very susceptible to strong plasma instabilities when molecular gases are introduced for processing applications. This led to an effective

The relationship between collisional phase defect distribution and cascade collapse efficiency

International Nuclear Information System (INIS)

Morishita, K.; Heinisch, H.L.; Ishino, S.; Sekimura, N.

1994-01-01

Defect distributions after the collisional phase of cascade damage processes were calculated using the computer simulation code MARLOWE, which is based on the binary collision approximation. The densities of vacant sites were evaluated in defect-dense regions at the end of the collisional phase in simulated ion irradiations of several pure metals (Au, Ag, Cu, Ni, Fe, Mo and W). The vacancy density distributions were compared to the measured cascade collapse efficiencies obtained from low-dose ion irradiations of thin foils reported in the literature to identify the minimum or ''critical'' values of the vacancy densities during the collisional phase corresponding to cascade collapse. The critical densities are generally independent of the cascade energy in the same metal. The relationships between physical properties of the target elements and the critical densities are discussed within the framework of the cascade thermal spike model. ((orig.))

Surface flute waves in plasmas theory and applications

CERN Document Server

Girka, Volodymyr; Thumm, Manfred

2014-01-01

The book presents results of a comprehensive study of various features of eigen electromagnetic waves propagating across the axis of plasma filled metal waveguides with cylindrical geometry. The authors collected in one book material on various features of surface flute waves, i. e. impact of waveguide design on wave dispersion, wave damping influenced by various reasons, impact of plasma density and external magnetic field inhomogeneity on the wave, and impact of waveguide corrugation and electric current on the wave. A variety of present surface waves applications and possible future applications is also included. Using the method of successive approximations it is shown how one can solve problems, which concern real experimental devices, starting from simple models. The book applies to both professionals dealing with problems of confined plasmas and to graduate and post-graduate students specializing in the field of plasma physics and related applications.

Proceedings of the Japan-US workshop on plasma polarization spectroscopy and the international seminar on plasma polarization spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Takashi; Beiersdorfer, Peter [eds.

1998-06-01

The international meeting on Plasma Polarization Spectroscopy (PPS) was held in Kyoto during January 26-28, 1998. This Proceedings book includes the papers of the talks given at the meeting. These include: overviews of PPS from the aspects of atomic physics, and of plasma physics; several PPS and MSE (motional Stark effect) experiments on magnetically confined plasmas and a laser-produced plasma; polarized laser-induced fluorescence spectroscopy, several experiments on EBITs (electron beam ion trap) and their theoretical interpretations; polarized profiles of spectral lines, basic formulation of PPS; inelastic and elastic electron collisions leading to polarized atomic states; polarization in recombining plasma; relationship between the collisional polarization relaxation and the line broadening; and characteristics of the plasma produced by very short pulse and high power laser irradiation. The 19 of the presented papers are indexed individually. (J.P.N.)

Kinetic and spectral descriptions of autoionization phenomena associated with atomic processes in plasmas

Science.gov (United States)

Jacobs, Verne L.

2017-06-01

This investigation has been devoted to the theoretical description and computer modeling of atomic processes giving rise to radiative emission in energetic electron and ion beam interactions and in laboratory plasmas. We are also interested in the effects of directed electron and ion collisions and of anisotropic electric and magnetic fields. In the kinetic-theory description, we treat excitation, de-excitation, ionization, and recombination in electron and ion encounters with partially ionized atomic systems, including the indirect contributions from processes involving autoionizing resonances. These fundamental collisional and electromagnetic interactions also provide particle and photon transport mechanisms. From the spectral perspective, the analysis of atomic radiative emission can reveal detailed information on the physical properties in the plasma environment, such as non-equilibrium electron and charge-state distributions as well as electric and magnetic field distributions. In this investigation, a reduced-density-matrix formulation is developed for the microscopic description of atomic electromagnetic interactions in the presence of environmental (collisional and radiative) relaxation and decoherence processes. Our central objective is a fundamental microscopic description of atomic electromagnetic processes, in which both bound-state and autoionization-resonance phenomena can be treated in a unified and self-consistent manner. The time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations of the reduced-density-matrix approach are developed in a unified and self-consistent manner. This is necessary for our ultimate goal of a systematic and self-consistent treatment of non-equilibrium (possibly coherent) atomic-state kinetics and high-resolution (possibly overlapping) spectral-line shapes. We thereby propose the introduction of a generalized collisional-radiative atomic-state kinetics model based on a reduced

An EDDY/particle-in-cell simulation of erosion of plasma facing walls bombarded by a collisional plasma

International Nuclear Information System (INIS)

Inai, Kensuke; Ohya, Kaoru

2011-01-01

To investigate the erosion of a plasma-facing wall intersecting an oblique magnetic field, we performed a kinetic particle-in-cell (PIC) simulation of magnetized plasma, in which collision processes between charged and neutral particles were taken into account. Sheath formation and local physical quantities, such as the incident angle and energy distributions of plasma ions at the wall, were examined at a plasma density of 10 18 m -3 , a temperature of 10 eV, and a magnetic field strength of 5 T. The erosion rate of a carbon wall was calculated using the ion-solid interaction code EDDY. At a high neutral density (>10 20 m -3 ), the impact energy of the ions dropped below the threshold for physical sputtering, so that the sputtering yield was drastically decreased and wall erosion was strongly suppressed. Sputter erosion was also suppressed when the angle of the magnetic field with respect to the surface normal was sufficiently large. (author)

RMP-Flutter-Induced Pedestal Plasma Transport

Energy Technology Data Exchange (ETDEWEB)

Callen, J. D.; Hegna, C., E-mail: callen@engr.wisc.edu [University of Wisconsin, Madison (United States); Cole, A. J. [Columbia University, New York (United States)

2012-09-15

Full text: Plasma toroidal rotation can prevent or limit reconnection of externally applied resonant magnetic perturbation (RMP) fields {delta}B on rational magnetic flux surfaces. Hence, it causes the induced radial perturbations to vanish or be small there, and thereby inhibits magnetic island formation and stochasticity in the edge of high (H-mode) confinement tokamak plasmas. However, the radial component of the spatial magnetic flutter induced by RMP fields off rational surfaces causes a radial electron thermal diffusivity of (1/2)({delta}B{sub p}/B){sup 2} times a magnetic-shear-influenced effective parallel electron thermal diffusivity. The resultant RMP-flutter-induced electron thermal diffusivity can be comparable to experimentally inferred values at the top of H-mode pedestals. This process also causes a factor of about 3 smaller RMP-induced electron density diffusivity there. Because this electron density transport is non-ambipolar, it produces a toroidal torque on the plasma, which is usually in the co-current direction. Kinetic-based cylindrical screw-pinch and toroidal models of these RMP-flutter-induced plasma transport effects have been developed. The RMP-induced increases in these diffusive plasma transport processes are typically spatially inhomogeneous in that they are strongly peaked near the rational surfaces in low collisionality pedestals, which may lead to resonant sensitivities to the local safety factor q. The effects can be large enough to reduce the radially averaged gradients of the electron temperature and density at the top of H-mode edge pedestals, and modify the plasma toroidal rotation and radial electric field there. At high collisionality the various effects are less strongly peaked at rational surfaces and thus less likely to exhibit RMP-induced resonant behavior. These RMP-flutter-induced plasma transport processes provide a new paradigm for developing an understanding of how RMPs modify the pedestal structure to stabilize

Effect of Radiation on Chromospheric Magnetic Reconnection: Reactive and Collisional Multi-fluid Simulations

Energy Technology Data Exchange (ETDEWEB)

Alvarez Laguna, A.; Poedts, S. [Centre for Mathematical Plasma-Astrophysics, KU Leuven, Leuven (Belgium); Lani, A.; Deconinck, H. [Aeronautics and Aerospace Department, von Karman Institute for Fluid Dynamics, Sint-Genesius-Rode (Belgium); Mansour, N. N. [NASA Ames Research Center, MS 230-3, Moffett Field, CA 94035 (United States)

2017-06-20

We study magnetic reconnection under chromospheric conditions in five different ionization levels from 0.5% to 50% using a self-consistent two-fluid (ions + neutrals) model that accounts for compressibility, collisional effects, chemical inequilibrium, and anisotropic heat conduction. Results with and without radiation are compared, using two models for the radiative losses: an optically thin radiation loss function, and an approximation of the radiative losses of a plasma with photospheric abundances. The results without radiation show that reconnection occurs faster for the weakly ionized cases as a result of the effect of ambipolar diffusion and fast recombination. The tearing mode instability appears earlier in the low ionized cases and grows rapidly. We find that radiative losses have a stronger effect than was found in previous results as the cooling changes the plasma pressure and the concentration of ions inside the current sheet. This affects the ambipolar diffusion and the chemical equilibrium, resulting in thin current sheets and enhanced reconnection. The results quantify this complex nonlinear interaction by showing that a strong cooling produces faster reconnections than have been found in models without radiation. The results accounting for radiation show timescales and outflows comparable to spicules and chromospheric jets.

Magnetic flux and heat losses by diffusive, advective, and Nernst effects in MagLIF-like plasma

International Nuclear Information System (INIS)

Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.

2014-01-01

The MagLIF approach to inertial confinement fusion involves subsonic/isobaric compression and heating of a DT plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot plasma to the cold liner is dominated by the transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter ω e τ e effective diffusion coefficients determining the losses of heat and magnetic flux are both shown to decrease with ω e τ e as does the Bohm diffusion coefficient, which is commonly associated with low collisionality and two-dimensional transport. This family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics

Measurement of the dynamo effect in a plasma

International Nuclear Information System (INIS)

Ji, H.; Prager, S.C.; Almagri, A.F.; Sarff, J.S.; Hirano, Y.; Toyama, H.

1995-11-01

A series of the detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line (the α effect) arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E x B drift and electron diamagnetic drift. The three major findings are (1) the α effect accounts for the dynamo current generation, even in the time dependence through a ''sawtooth'' cycle; (2) at low collisionality the dynamo is explained primarily by the widely studied pressureless Magnetohydrodynamic (MHD) model, i.e., the fluctuating velocity is dominated by the E x B drift; (3) at high collisionality, a new ''electron diamagnetic dynamo'' is observed, in which the fluctuating velocity is dominated by the diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying J.B. Taylor's conjecture

MMS observation of energy conversion and collisionless plasma dissipation channels in the turbulent magnetosheath

Science.gov (United States)

Parashar, T.; Yang, Y.; Chasapis, A.; Matthaeus, W. H.

2017-12-01

High resolution Magnetospheric Multiscale (MMS) plasma and magnetic field data obtained in the inhomogeneous turbulent magnetosheath directly reveals the exchanges of energy between electromagnetic, flow and random kinetic energy. The parameters that quantify these exchanges are based on standard manipulations of the collisionless Vlasov model of plasma dynamics [1], without appeal to viscous or other closures. No analysis of heat transport or heat conduction is carried out. Several intervals of burst mode data in the magnetosheath are considered. Time series of the work done by the electromagnetic field, and the pressure-stress interaction enable description of the pathways to dissipation in this low collisionality plasma. Using these examples we demonstrate that the pressure-stress interaction provides important information not readily revealed in other diagnostics concerning the physical processes that are observed. This method does not require any specific mechanism for its application such as reconnection or a selected mode, although with increased experience it will be useful in distinguishing among proposed possibilities. [1] Y. Yang et al, Phys. Plasmas 24, 072306 (2017); doi: 10.1063/1.4990421.

Collisional avalanche exponentiation of runaway electrons in electrified plasmas

International Nuclear Information System (INIS)

Jayakumar, R.; Fleischmann, H.H.; Zweben, S.J.

1993-01-01

In contrast to earlier expectations, it is estimated that generation of runaway electrons from close collisions of existing runaways with cold plasma electrons can be significant even for small electric fields, whenever runaways can gain energies of about 20 MeV or more. In that case, the runaway population will grow exponentially with the energy spectrum showing an exponential decrease towards higher energies. Energy gains of the required magnitude may occur in large tokamak devices as well as in cosmic-ray generation. (orig.)

Applications of plasma core reactors to terrestrial energy systems

International Nuclear Information System (INIS)

Lantham, T.S.; Biancardi, F.R.; Rodgers, R.J.

1974-01-01

Plasma core reactors offer several new options for future energy needs in addition to space power and propulsion applications. Power extraction from plasma core reactors with gaseous nuclear fuel allows operation at temperatures higher than conventional reactors. Highly efficient thermodynamic cycles and applications employing direct coupling of radiant energy are possible. Conceptual configurations of plasma core reactors for terrestrail applications are described. Closed-cycle gas turbines, MHD systems, photo- and thermo-chemical hydrogen production processes, and laser systems using plasma core reactors as prime energy sources are considered. Cycle efficiencies in the range of 50 to 65 percent are calculated for closed-cycle gas turbine and MHD electrical generators. Reactor advantages include continuous fuel reprocessing which limits inventory of radioactive by-products and thorium-U-233 breeder configurations with about 5-year doubling times

Microwave plasmas generated in bubbles immersed in liquids for hydrocarbons reforming

International Nuclear Information System (INIS)

Levko, Dmitry; Sharma, Ashish; Raja, Laxminarayan L

2016-01-01

We present a computational modeling study of microwave plasma generated in cluster of atmospheric-pressure argon bubbles immersed in a liquid. We demonstrate that the use of microwaves allows the generation of a dense chemically active non-equilibrium plasma along the gas–liquid interface. Also, microwaves allow generation of overdense plasma in all the bubbles considered in the cluster which is possible because the collisional skin depth of the wave exceeds the bubble dimension. These features of microwave plasma generation in bubbles immersed in liquids are highly desirable for the large-scale liquid hydrocarbon reforming technologies. (letter)

Plasma treatment: A Novel Medical Application

International Nuclear Information System (INIS)

Boonyawan, Dheerawan

2015-01-01

Cold atmospheric plasma (CAP) for the medical treatment is a new field in plasma application, called plasma medicine. CAP contrains mix of excited atoms and molecules, UV photons, charged particles as well as reactive oxygen species (ROS) and reactive nitrogen species (RNS). Typical species in air CAPs are O 3 , OH, N x , and HNO x . Two cold atomospheric plasma devices were utiized (either in an indirect or a direct way) for the treatment of physiologically healthy volunterrs, The results show that CAP is effective againts chronic wound infections and/ or for skin treatment in clinical trials. The current developments in this field have fuelled the hope that CAP could be, and interesting new therapeutic apptoach in the treatment of cancer.

Understanding non-equilibrium collisional and expansion effects in the solar wind with Parker Solar Probe

Science.gov (United States)

Korreck, K. E.; Klein, K. G.; Maruca, B.; Alterman, B. L.

2017-12-01

The evolution of the solar wind from the corona to the Earth and throughout the heliosphere is a complex interplay between local micro kinetics and large scale expansion effects. These processes in the solar wind need to be separated in order to understand and distinguish the dominant mechanism for heating and acceleration of the solar wind. With the upcoming launch in 2018 of Parker Solar Probe and the launch of Solar Orbiter after, addressing the local and global phenomena will be enabled with in situ measurements. Parker Solar Probe will go closer to the Sun than any previous mission enabling the ability to examine the solar wind at an early expansion age. This work examines the predictions for what will be seen inside of the 0.25 AU (54 solar radii) where Parker Solar Probe will take measurements and lays the groundwork for disentangling the expansion and collisional effects. In addition, methods of thermal plasma data analysis to determine the stability of the plasma in the Parker Solar Probe measurements will be discussed.

Plasma in dentistry: a review of basic concepts and applications in dentistry.

Science.gov (United States)

Kim, Jae-Hoon; Lee, Mi-Ae; Han, Geum-Jun; Cho, Byeong-Hoon

2014-01-01

Plasma-related technologies are essential in modern industries. Recently, plasma has attracted increased attention in the biomedical field. This paper provides a basic knowledge of plasma and a narrative review of plasma applications in dentistry. To review plasma applications in dentistry, an electronic search in PubMed, SCOPUS and Google scholar up to December 2012 was done. This was followed by extensive hand searching using reference lists from relevant articles. There have been attempts to apply plasma technology in various fields of dentistry including surface modifications of dental implants, adhesion, caries treatment, endodontic treatment and tooth bleaching. Although many studies were in early stages, the potential value of plasma for dental applications has been demonstrated. To enlarge the scope of plasma applications and put relevant research to practical use, interdisciplinary research with participation of dental professionals is required.

Collisional excitation transfer between Rb(5P) states in 50–3000 Torr of 4He

International Nuclear Information System (INIS)

Sell, J F; Gearba, M A; Patterson, B M; Byrne, D; Jemo, G; Meeter, R; Knize, R J; Lilly, T C

2012-01-01

Measurements of the mixing rates and cross sections for collisional excitation transfer between the 5P 1/2 and 5P 3/2 states of rubidium (Rb) in the presence of 4 He buffer gas are presented. Selected pulses from a high repetition rate, mode-locked femtosecond laser are used to excite either Rb state with the fluorescence due to collisional excitation transfer observed by time-correlated single-photon counting. The time dependence of this fluorescence is fitted to the solution of rate equations which include the mixing rate, atomic lifetimes and any quenching processes. The variation in the mixing rate over a large range of buffer gas densities allows the determination of both the binary collisional transfer cross section and a three-body collisional transfer rate. We do not observe any collisional quenching effects at 4 He pressures up to 6 atm and discuss in detail other systematic effects considered in the experiment. (paper)

Plasma cleaning techniques and future applications in environmentally conscious manufacturing

Energy Technology Data Exchange (ETDEWEB)

Ward, P.P.

1995-07-01

Plasmas have frequently been used in industry as a last step surface preparation technique in an otherwise predominantly wet-etch process. The limiting factor in the usefulness of plasma cleaning techniques has been the rate at which organic materials are removed. Recent research in the field of plasma chemistry has provided some understanding of plasma processes. By controlling plasma conditions and gas mixtures, ultra-fast plasma cleaning and etching is possible. With enhanced organic removal rates, plasma processes become more desirable as an environmentally sound alternative to traditional solvent or acid dominated process, not only as a cleaning tool, but also as a patterning and machining tool. In this paper, innovations in plasma processes are discussed including enhanced plasma etch rates via plasma environment control and aggressive gas mixtures. Applications that have not been possible with the limited usefulness of past plasma processes are now approaching the realm of possibility. Some of these possible applications will be discussed along with their impact to environmentally conscious manufacturing.

Self-consistent collisional-radiative model for hydrogen atoms: Atom–atom interaction and radiation transport

International Nuclear Information System (INIS)

Colonna, G.; Pietanza, L.D.; D’Ammando, G.

2012-01-01

Graphical abstract: Self-consistent coupling between radiation, state-to-state kinetics, electron kinetics and fluid dynamics. Highlight: ► A CR model of shock-wave in hydrogen plasma has been presented. ► All equations have been coupled self-consistently. ► Non-equilibrium electron and level distributions are obtained. ► The results show non-local effects and non-equilibrium radiation. - Abstract: A collisional-radiative model for hydrogen atom, coupled self-consistently with the Boltzmann equation for free electrons, has been applied to model a shock tube. The kinetic model has been completed considering atom–atom collisions and the vibrational kinetics of the ground state of hydrogen molecules. The atomic level kinetics has been also coupled with a radiative transport equation to determine the effective adsorption and emission coefficients and non-local energy transfer.

SCRIC: a code dedicated to the detailed emission and absorption of heterogeneous NLTE plasmas; application to xenon EUV sources; SCRIC: un code pour calculer l'absorption et l'emission detaillees de plasmas hors equilibre, inhomogenes et etendus; application aux sources EUV a base de xenon

Energy Technology Data Exchange (ETDEWEB)

Gaufridy de Dortan, F. de

2006-07-01

Nearly all spectral opacity codes for LTE and NLTE plasmas rely on configurations approximate modelling or even supra-configurations modelling for mid Z plasmas. But in some cases, configurations interaction (either relativistic and non relativistic) induces dramatic changes in spectral shapes. We propose here a new detailed emissivity code with configuration mixing to allow for a realistic description of complex mid Z plasmas. A collisional radiative calculation. based on HULLAC precise energies and cross sections. determines the populations. Detailed emissivities and opacities are then calculated and radiative transfer equation is resolved for wide inhomogeneous plasmas. This code is able to cope rapidly with very large amount of atomic data. It is therefore possible to use complex hydrodynamic files even on personal computers in a very limited time. We used this code for comparison with Xenon EUV sources within the framework of nano-lithography developments. It appears that configurations mixing strongly shifts satellite lines and must be included in the description of these sources to enhance their efficiency. (author)

Atmospheric plasma processes for environmental applications

OpenAIRE

Shapoval, Volodymyr

2012-01-01

Plasma chemistry is a rapidly growing field which covers applications ranging from technological processing of materials, including biological tissues, to environmental remediation and energy production. The so called atmospheric plasma, produced by electric corona or dielectric barrier discharges in a gas at atmospheric pressure, is particularly attractive for the low costs and ease of operation and maintenance involved. The high concentrations of energetic and chemically active species (e.g...

Neoclassical MHD descriptions of tokamak plasmas

International Nuclear Information System (INIS)

Callen, J.D.; Kim, Y.B.; Sundaram, A.K.

1988-01-01

Considerable progress has been made in extending neoclassical MHD theory and in exploring the linear instabilities, nonlinear behavior and turbulence models it implies for tokamak plasmas. The areas highlighted in this paper include: extension of the neoclassical MHD equations to include temperature-gradient and heat flow effects; the free energy and entropy evolution implied by this more complete description; a proper ballooning mode formalism analysis of the linear instabilities; a new rippling mode type instability; numerical simulation of the linear instabilities which exhibit a smooth transition from resistive ballooning modes at high collisionality to neoclassical MHD modes at low collisionality; numerical simulation of the nonlinear growth of a single helicity tearing mode; and a Direct-Interaction-Approximation model of neoclassical MHD turbulence and the anomalous transport it induces which substantially improves upon previous mixing length model estimates. 34 refs., 2 figs

Theory for neoclassical toroidal plasma viscosity in tokamaks

International Nuclear Information System (INIS)

Shaing, K C; Chu, M S; Hsu, C T; Sabbagh, S A; Seol, Jae Chun; Sun, Y

2012-01-01

Error fields and magnetohydrodynamic modes break toroidal symmetry in tokamaks. The broken symmetry enhances the toroidal plasma viscosity, which results in a steady-state toroidal plasma flow. A theory for neoclassical toroidal plasma viscosity in the low-collisionality regimes is developed. It extends stellarator transport theory to include multiple modes and to allow for |m − nq| ∼ 1. Here, m is the poloidal mode number, n is the toroidal mode number and q is the safety factor. The bounce averaged drift kinetic equation is solved in several asymptotic limits to obtain transport fluxes. These fluxes depend non-linearly on the radial electric field except for those in the 1/ν regime. Here, ν is the collision frequency. The theory is refined to include the effects of the superbanana plateau resonance at the phase space boundary and the finite ∇B drift on the collisional boundary layer fluxes. Analytical expressions that connect all asymptotic limits are constructed and are in good agreement with the numerical results. The flux–force relations that relate transport fluxes to forces are used to illustrate the roles of transport fluxes in the momentum equation. It is shown that the ambipolar state is reached when the momentum equation is relaxed. It is also shown that the origin of the momentum for plasma flow generated without momentum sources is the local unbalance of particles' momenta and is diamagnetic in nature regardless of the details of the theory. (paper)

Fully implicit kinetic modelling of collisional plasmas

International Nuclear Information System (INIS)

Mousseau, V.A.

1996-05-01

This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. To this end, implementations of Chang-Cooper differencing and flux limited Quadratic Upstream Interpolation for Convective Kinematics (QUICK) are presented. Results are given for a fully kinetic ion-electron problem with a self consistent electric field calculated from the ion and electron distribution functions. This numerical method, including advanced differencing, provides accurate solutions, which quickly converge on workstation class machines. It is demonstrated that efficient steady-state solutions can be achieved to the non-linear integro-differential equation, obtaining quadratic convergence, without incurring the large memory requirements of an integral operator. Model problems are presented which simulate plasma impinging on a plate with both high and low neutral particle recycling typical of a divertor in a Tokamak device. These model problems demonstrate the performance of the new solution method

Modification of Edge Plasma Turbulence by External Magnetic Pertubations

International Nuclear Information System (INIS)

Boedo, J.; McKee, G.; Rudakov, D.; Reiser, D.; Evans, T.; Moyer, R.; Schaffer, M.; Watkins, J.; Allen, S.; Fenstermacher, M.; Groth, M.; Holland, C.; Hollmann, E.; Lasnier, C.; Leonard, A.; Mahdavi, M.; McLean, A.; Tynan, G.; Wang, G.; West, W.; Zeng, L.

2006-01-01

Magnetostatic perturbations applied to the DIII-D plasma using a n=3 coil set have significant impact on the plasma edge, such as edge localized mode (ELM) suppression [1], but also affect the background turbulence levels. Discharges with parameters R=1.75 m, a=0.56 m, B T ∼ 1.6 T, I p ∼ 1 MA and n e ∼ 3 x 10 13 cm -3 -n e ∼ 7 x 10 13 cm -3 (low, v* e ∼ 0.1 and moderate, v* e ∼ 1 electron pedestal collisionality) were used as a target for the perturbation, [applied at 3 s Fig. 1(a) and 2 s Fig. 1(b)]. The global density and energy content, among many other parameters, are unaffected, raising the issue of what mechanism replaces the particle and heat exhaust otherwise mediated by ELMs. Mixed ELMs (high frequency, low amplitude Type II ELMs interspersed with Type I) in the moderate collisionality regime and Type I ELMs in the low collisionality regime, are replaced by intermittency and broadband turbulence or semiperiodic events. It is important to notice that the coils can be energized in high poloidal mode spectra (upper and lower coils produce fields in the same direction) or odd configuration (upper and lower coils produce fields in the opposite direction) and also rotated 60 deg toroidally. Although we will focus on scanning probe [2] data obtained in the scrape-off layer (SOL), other diagnostics, beam emission spectroscopy (BES), reflectometry [3], were used to study the changes in the plasma turbulence when the ELMs are suppressed and the underlying turbulence and transport change. Thomson scattering n e and T e profiles (Fig. 2) accumulated over 200 ms before (red) and during (blue) I-coil perturbation are fitted with y = a + b* tanh[(r-c)/d] resulting in a,b staying constant while d varies from -0.009 to -0.011 and c from -0.013 to -0.009, i.e. the profiles mostly broaden and shift outward, changes which may be connected to an increase in radial turbulent transport assuming no deformation of the separatrix. This broadening is seen in both low and

Theoretical Atomic Physics code development II: ACE: Another collisional excitation code

International Nuclear Information System (INIS)

Clark, R.E.H.; Abdallah, J. Jr.; Csanak, G.; Mann, J.B.; Cowan, R.D.

1988-12-01

A new computer code for calculating collisional excitation data (collision strengths or cross sections) using a variety of models is described. The code uses data generated by the Cowan Atomic Structure code or CATS for the atomic structure. Collisional data are placed on a random access file and can be displayed in a variety of formats using the Theoretical Atomic Physics Code or TAPS. All of these codes are part of the Theoretical Atomic Physics code development effort at Los Alamos. 15 refs., 10 figs., 1 tab

Progress toward commissioning and plasma operation in NSTX-U

Science.gov (United States)

Ono, M.; Chrzanowski, J.; Dudek, L.; Gerhardt, S.; Heitzenroeder, P.; Kaita, R.; Menard, J. E.; Perry, E.; Stevenson, T.; Strykowsky, R.; Titus, P.; von Halle, A.; Williams, M.; Atnafu, N. D.; Blanchard, W.; Cropper, M.; Diallo, A.; Gates, D. A.; Ellis, R.; Erickson, K.; Hosea, J.; Hatcher, R.; Jurczynski, S. Z.; Kaye, S.; Labik, G.; Lawson, J.; LeBlanc, B.; Maingi, R.; Neumeyer, C.; Raman, R.; Raftopoulos, S.; Ramakrishnan, R.; Roquemore, A. L.; Sabbagh, S. A.; Sichta, P.; Schneider, H.; Smith, M.; Stratton, B.; Soukhanovskii, V.; Taylor, G.; Tresemer, K.; Zolfaghari, A.; The NSTX-U Team

2015-07-01

The National Spherical Torus Experiment-Upgrade (NSTX-U) is the most powerful spherical torus facility at PPPL, Princeton USA. The major mission of NSTX-U is to develop the physics basis for an ST-based Fusion Nuclear Science Facility (FNSF). The ST-based FNSF has the promise of achieving the high neutron fluence needed for reactor component testing with relatively modest tritium consumption. At the same time, the unique operating regimes of NSTX-U can contribute to several important issues in the physics of burning plasmas to optimize the performance of ITER. NSTX-U further aims to determine the attractiveness of the compact ST for addressing key research needs on the path toward a fusion demonstration power plant (DEMO). The upgrade will nearly double the toroidal magnetic field BT to 1 T at a major radius of R0 = 0.93 m, plasma current Ip to 2 MA and neutral beam injection (NBI) heating power to 14 MW. The anticipated plasma performance enhancement is a quadrupling of the plasma stored energy and near doubling of the plasma confinement time, which would result in a 5-10 fold increase in the fusion performance parameter nτ T. A much more tangential 2nd NBI system, with 2-3 times higher current drive efficiency compared to the 1st NBI system, is installed to attain the 100% non-inductive operation needed for a compact FNSF design. With higher fields and heating powers, the NSTX-U plasma collisionality will be reduced by a factor of 3-6 to help explore the favourable trend in transport towards the low collisionality FNSF regime. The NSTX-U first plasma is planned for the Summer of 2015, at which time the transition to plasma operations will occur.

A phenomenological model for collisional coherence transfer in an optically pumped atomic system

Energy Technology Data Exchange (ETDEWEB)

Khanbekyan, K; Bevilaqua, G; Mariotti, E; Moi, L [Universita degli Studi di Siena, Siena, 53100 (Italy); Khanbekyan, A; Papoyan, A, E-mail: karen.khanbekyan@gmail.com [Institute for Physical Research, National Academy of Sciences, Ashtarak 2 (Armenia)

2011-03-14

We consider a dual {Lambda}-system under double laser excitation to investigate the possibility of indirect coherence transfer between atomic ground states through an excited state. The atomic system is excited by a frequency modulated pump laser and probed by a low-power cw laser. All the decoherence mechanisms are discussed and taken into account. Adjustment of parameters of the two radiations aimed at maximization of coherence transfer is addressed. The study can help to understand the phenomena as collisional transfer of coherence and can find application in the experimental realization of atomic sensors.

Plasma-based localized defect for switchable coupling applications

International Nuclear Information System (INIS)

Varault, Stefan; Gabard, Benjamin; Sokoloff, Jerome; Bolioli, Sylvain

2011-01-01

We report in this paper experimental measurements in order to validate the concept of switchable electromagnetic band gap filters based on plasma capillaries in the microwave regime. The plasma tube is embedded inside the structure to create a bistable (plasma on or off) punctual defect. We first investigate two kinds of discharge tubes: Ar-Hg and pure Ne, which we then use to experimentally achieve plasma-based reconfigurable applications, namely, a two-port coupler and a two-port demultiplexer.

Studies of high repetition rate laser-produced plasma soft-X-ray amplifiers; Etudes d'amplificateurs plasma laser a haute cadence dans le domaine X-UV et applications

Energy Technology Data Exchange (ETDEWEB)

Cassou, K

2006-12-15

The progress made as well on the Ti:Sa laser system, as in the control and the knowledge of laser produced X-UV sources allowed the construction of a X-UV laser station dedicated to the applications. My thesis work falls under the development of this station and more particularly on the characterization of a X-UV laser plasma amplifier. The experimental study relates to the coupling improvement of the pump infra-red laser with plasma within the framework of the transient collisional X-UV laser generation. These X-UV lasers are generated in a plasma formed by the interaction of a solid target and a laser pulse of approximately 500 ps duration, followed by a second infra-red laser pulse known as of pump (about 5 ps) impinging on the target in grazing incidence. For the first time, a complete parametric study was undertaken on the influence of the grazing angle on the pumping of the amplifying medium. One of the results was to reach very high peak brightness about 10{sup 28} ph/s/mm{sup 2}/mrad{sup 2}/(0.1%bandwidth), which compares well with the free-electron laser brightness. Moreover, we modified then used a new two-dimensional hydrodynamic code with adaptive mesh refinement in order to understand the influence of the space-time properties of the infra-red laser on the formation and the evolution of the amplifying plasma. Our modeling highlighted the interest to use a super Gaussian transverse profile for the line focus leading to an increase in a factor two of the gain region size and a reduction of the electron density gradient by three orders of magnitude. These improvements should strongly increase the energy contained in X-UV laser beam. We thus used X-UV laser to study the appearance of transient defects produced by a laser IR on a beam-splitter rear side. We also began research on the mechanisms of DNA damage induced by a very intense X-UV radiation. (author)

Beam-plasma discharge in a Kyoto beam-plasma-ion source

International Nuclear Information System (INIS)

Ishikawa, J.; Takagi, T.

1983-01-01

A beam-plasma type ion source employing an original operating principle has been developed by the present authors. The ion source consists of an ion extraction region with an electron gun, a thin long drift tube as the plasma production chamber, and a primary electron beam collector. An electron beam is effectively utilized for the dual purpose of high density plasma production as a result of beam-plasma discharge, and high current ion beam extraction with ion space-charge compensation. A high density plasma of the order of 10 11 --10 13 cm -3 was produced by virtue of the beam-plasma discharge which was caused by the interaction between a space-charge wave on the electron beam and a high frequency plasma wave. The plasma density then produced was 10 2 --10 3 times the density produced only by collisional ionization by the electron beam. In order to obtain a stable beam-plasma discharge, a secondary electron beam emitted from the electron collector should be utilized. The mechanism of the beam-plasma discharge was analyzed by use of a linear theory in the case of the small thermal energy of the electron beam, and by use of a quasilinear theory in the case of the large thermal energy. High current ion beams of more than 0.1 A were extracted even at a low extraction voltage of 1--5 kV

Spectroscopy of X-ray Photoionized Plasmas in the Laboratory

Science.gov (United States)

Liedahl, Duane A.; Loisel, Guillaume; Bailey, James E.; Nagayama, Taisuke; Hansen, Stephanie B.; Rochau, Gregory; Fontes, Christopher J.; Mancini, Roberto; Kallman, Timothy R.

2018-06-01

The physical processes operating in astrophysical plasmas --- heating, cooling, ionization, recombination, level population kinetics, and radiation transport --- are all accessible to observation in the laboratory. What distinguishes X-ray photoionized plasmas from the more common case of high-temperature collisionally-ionized plasmas is the elevated level of importance of the radiation/matter interaction. The advent of laboratory facilities with the capability to generate high-powered X-ray sources has provided the means by which to study this interaction, which is also fundamental to active galactic nuclei and other accretion-powered objects. We discuss recent and ongoing experiments, with an emphasis on X-ray spectroscopic measurements of silicon plasmas obtained at the Sandia Z Pulsed Power Facility.

Ion acceleration by laser hole-boring into plasmas

International Nuclear Information System (INIS)

Pogorelsky, I. V.; Dover, N. P.; Babzien, M.; Bell, A. R.; Dangor, A. E.; Horbury, T.; Palmer, C. A. J.; Polyanskiy, M.; Schreiber, J.; Schwartz, S.; Shkolnikov, P.; Yakimenko, V.; Najmudin, Z.

2012-01-01

By experiment and simulations, we study the interaction of an intense CO 2 laser pulse with slightly overcritical plasmas of fully ionized helium gas. Transverse optical probing is used to show a recession of the front plasma surface with an initial velocity >10 6 m/s driven by hole-boring by the laser pulse and the resulting radiation pressure driven electrostatic shocks. The collisionless shock propagates through the plasma, dissipates into an ion-acoustic solitary wave, and eventually becomes collisional as it slows further. These observations are supported by PIC simulations which prove the conclusion that monoenergetic protons observed in our earlier reported experiment with a hydrogen jet result from ion trapping and reflection from a shock wave driven through the plasma.

Beam-generated plasmas for processing applications

Science.gov (United States)

Meger, R. A.; Blackwell, D. D.; Fernsler, R. F.; Lampe, M.; Leonhardt, D.; Manheimer, W. M.; Murphy, D. P.; Walton, S. G.

2001-05-01

The use of moderate energy electron beams (e-beams) to generate plasma can provide greater control and larger area than existing techniques for processing applications. Kilovolt energy electrons have the ability to efficiently ionize low pressure neutral gas nearly independent of composition. This results in a low-temperature, high-density plasma of nearly controllable composition generated in the beam channel. By confining the electron beam magnetically the plasma generation region can be designated independent of surrounding structures. Particle fluxes to surfaces can then be controlled by the beam and gas parameters, system geometry, and the externally applied rf bias. The Large Area Plasma Processing System (LAPPS) utilizes a 1-5 kV, 2-10 mA/cm2 sheet beam of electrons to generate a 1011-1012cm-3 density, 1 eV electron temperature plasma. Plasma sheets of up to 60×60 cm2 area have been generated in a variety of molecular and atomic gases using both pulsed and cw e-beam sources. The theoretical basis for the plasma production and decay is presented along with experiments measuring the plasma density, temperature, and potential. Particle fluxes to nearby surfaces are measured along with the effects of radio frequency biasing. The LAPPS source is found to generate large-area plasmas suitable for materials processing.

Dynamics of Dust in a Plasma Sheath with Magnetic Field

International Nuclear Information System (INIS)

Duan Ping; Liu Jinyuan; Gon Ye; Liu Yue; Wang Xiaogang

2007-01-01

Dynamics of dust in a plasma sheath with a magnetic field was investigated using a single particle model. The result shows that the radius, initial position, initial velocity of the dust particles and the magnetic field do effect their movement and equilibrium position in the plasma sheath. Generally, the dust particles with the same size, whatever original velocity and position they have, will locate at the same position in the end under the net actions of electrostatic, gravitational, neutral collisional, and Lorentz forces. But the dust particles will not locate in the plasma sheath if their radius is beyond a certain value

Magnetospheric Multiscale (MMS) Observation of Plasma Velocity-Space Cascade Processes

Science.gov (United States)

Parashar, T. N.; Servidio, S.; Matthaeus, W. H.; Chasapis, A.; Perrone, D.; Valentini, F.; Veltri, P.; Gershman, D. J.; Schwartz, S. J.; Giles, B. L.; Fuselier, S. A.; Phan, T.; Burch, J.

2017-12-01

Plasma turbulence is investigated using high-resolution ion velocity distributions, measured by theMagnetospheric Multiscale Mission (MMS) in the Earth's magnetosheath. The particle distributionmanifests large fluctuations, suggesting a cascade-like process in velocity space, invoked by theoristsfor many years. This complex velocity space structure is investigated using a three-dimensional Hermitetransform that reveals a power law distribution of moments. A Kolmogorov approach leads directlyto a range of predictions for this phase-space cascade. The scaling theory is in agreement withobservations, suggesting a new path for the study of plasma turbulence in weakly collisional spaceand astrophysical plasmas.

Perspective: The physics, diagnostics, and applications of atmospheric pressure low temperature plasma sources used in plasma medicine

Science.gov (United States)

Laroussi, M.; Lu, X.; Keidar, M.

2017-07-01

Low temperature plasmas have been used in various plasma processing applications for several decades. But it is only in the last thirty years or so that sources generating such plasmas at atmospheric pressure in reliable and stable ways have become more prevalent. First, in the late 1980s, the dielectric barrier discharge was used to generate relatively large volume diffuse plasmas at atmospheric pressure. Then, in the early 2000s, plasma jets that can launch cold plasma plumes in ambient air were developed. Extensive experimental and modeling work was carried out on both methods and much of the physics governing such sources was elucidated. Starting in the mid-1990s, low temperature plasma discharges have been used as sources of chemically reactive species that can be transported to interact with biological media, cells, and tissues and induce impactful biological effects. However, many of the biochemical pathways whereby plasma affects cells remain not well understood. This situation is changing rather quickly because the field, known today as "plasma medicine," has experienced exponential growth in the last few years thanks to a global research community that engaged in fundamental and applied research involving the use of cold plasma for the inactivation of bacteria, dental applications, wound healing, and the destruction of cancer cells/tumors. In this perspective, the authors first review the physics as well as the diagnostics of the principal plasma sources used in plasma medicine. Then, brief descriptions of their biomedical applications are presented. To conclude, the authors' personal assessment of the present status and future outlook of the field is given.

Impurities in a non-axisymmetric plasma: Transport and effect on bootstrap current

Energy Technology Data Exchange (ETDEWEB)

Mollén, A., E-mail: albertm@chalmers.se [Department of Applied Physics, Chalmers University of Technology, Göteborg (Sweden); Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); Landreman, M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Smith, H. M.; Helander, P. [Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); Braun, S. [Max-Planck-Institut für Plasmaphysik, 17491 Greifswald (Germany); German Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, D-70569 Stuttgart (Germany)

2015-11-15

Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21, 042503 (2014)] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/ν-scaling of the inter-species radial transport coefficient at low collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We also use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Z{sub eff} of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.

Investigation and applications of a plasma generator

International Nuclear Information System (INIS)

Frere, Isabelle

1992-01-01

This work describes the experimental study of a plasma generator: a cylindrical or parallelepipedic rectangle cathode. A permanent magnet creates an axial magnetic field of a few hundred Gauss. A cold and abnormal glow discharge plasma is obtained. The experimental research on the correlation between the discharge parameters (electrode geometry, gas pressure, discharge voltage and current, magnetic field) of the discharge is presented. Another part of the text mentions some generator applications to surface treatment: evaporation, sputtering, surface modification of polymers by exposure to plasma. (author) [fr

Numerical simulation of collision-free plasma using Vlasov hybrid simulation

International Nuclear Information System (INIS)

Nunn, D.

1990-01-01

A novel scheme for the numerical simulation of wave particle interactions in space plasmas has been developed. The method, termed VHS or Vlasov Hybrid Simulation, is applicable to hot collision free plasmas in which the unperturbed distribution functions is smooth and free of delta function singularities. The particle population is described as a continuous Vlasov fluid in phase space-granularity and collisional effects being ignored. In traditional PIC/CIC codes the charge/current due to each simulation particle is assigned to a fixed spatial grid. In the VHS method the simulation particles sample the Vlasov fluid and provide information about the value of distribution function (F(r,v) at random points in phase space. Values of F are interpolated from the simulation particles onto a fixed grid in velocity/position or phase space. With distribution function defined on a phase space grid the plasma charge/current field is quickly calculated. The simulation particles serve only to provide information, and thus the particle population may be dynamic. Particles no longer resonant with the wavefield may be discarded from the simulation, and new particles may be inserted into the Vlasov fluid where required

Plasma heating in multiple-resonance excitation of a plasma in a mirror machine

Energy Technology Data Exchange (ETDEWEB)

Bender, A; Siambis, J G [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1976-06-01

By applying 1 kW of microwave power at 2.45 GHz and 1 kW of r.f. power in the frequency range of 4-25 MHz at one end of a mirror machine, where neutral hydrogen gas is injected in a pulsed mode, a plasma density of 2 x 10/sup 11/cm/sup -3/ with an electron temperature of 60 eV and ion temperature of 40 eV is generated. The ion heating mechanism, is, principally, collisional thermalization of the applied r.f. power, via coupling to and excitation of the low frequency resonances of the plasma column, in agreement with the theoretical prediction for the case of high total effective collision frequency for momentum transfer for the electrons.

Results from colliding magnetized plasma jet experiments executed at the Trident laser facility

Science.gov (United States)

Manuel, M. J.-E.; Rasmus, A. M.; Kurnaz, C. C.; Klein, S. R.; Davis, J. S.; Drake, R. P.; Montgomery, D. S.; Hsu, S. C.; Adams, C. S.; Pollock, B. B.

2015-11-01

The interaction of high-velocity plasma flows in a background magnetic field has applications in pulsed-power and fusion schemes, as well as astrophysical environments, such as accretion systems and stellar mass ejections into the magnetosphere. Experiments recently executed at the Trident Laser Facility at the Los Alamos National Laboratory investigated the effects of an expanding aluminum plasma flow into a uniform 4.5-Tesla magnetic field created using a solenoid designed and manufactured at the University of Michigan. Opposing-target experiments demonstrate interesting collisional behavior between the two magnetized flows. Preliminary interferometry and Faraday rotation measurements will be presented and discussed. This work is funded by the U.S Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840. Support for this work was provided by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Astrophysical Observatory for NASA under contract NAS8-03060.

Biomedical applications using low temperature plasma technology

International Nuclear Information System (INIS)

Dai Xiujuan; Jiang Nan

2006-01-01

Low temperature plasma technology and biomedicine are two different subjects, but the combination of the two may play a critical role in modern science and technology. The 21 st century is believed to be a biotechnology century. Plasma technology is becoming a widely used platform for the fabrication of biomaterials and biomedical devices. In this paper some of the technologies used for material surface modification are briefly introduced. Some biomedical applications using plasma technology are described, followed by suggestions as to how a bridge between plasma technology and biomedicine can be built. A pulsed plasma technique that is used for surface functionalization is discussed in detail as an example of this kind of bridge or combination. Finally, it is pointed out that the combination of biomedical and plasma technology will be an important development for revolutionary 21st century technologies that requires different experts from different fields to work together. (authors)

Contribution to the modelling and multi-scale numerical simulation of kinetic electron transport in hot plasma

International Nuclear Information System (INIS)

Mallet, J.

2012-01-01

This research thesis stands at the crossroad of plasma physics, numerical analysis and applied mathematics. After an introduction presenting the problematic and previous works, the author recalls some basis of classical kinetic models for plasma physics (collisionless kinetic theory and Vlasov equation, collisional kinetic theory with the non-relativistic Maxwell-Fokker-Plansk system) and describes the fundamental properties of the collision operators such as conservation laws, entropy dissipation, and so on. He reports the improvement of a deterministic numerical method to solve the non-relativistic Vlasov-Maxwell system coupled with Fokker-Planck-Landau type operators. The efficiency of each high order scheme is compared. The evolution of the hot spot is studied in the case of thermonuclear reactions in the centre of the pellet in a weakly collisional regime. The author focuses on the simulation of the kinetic electron collisional transport in inertial confinement fusion (ICF) between the laser absorption zone and the ablation front. A new approach is then introduced to reduce the huge computation time obtained with kinetic models. In a last chapter, the kinetic continuous equation in spherical domain is described and a new model is chosen for collisions in order to preserve collision properties

Plasma technologies: applications to waste processing

International Nuclear Information System (INIS)

Fauchais, P.

2007-01-01

Since the 1990's, plasma technologies have found applications in the processing of toxic wastes of military and industrial origin, like the treatment of contaminated solids and low level radioactive wastes, the decontamination of soils etc.. Since the years 2000, this development is becoming exponential, in particular for the processing of municipal wastes and the recovery of their synthesis gas. The advantage of thermal plasmas with respect to conventional combustion techniques are: a high temperature (more than 6000 K), a pyrolysis capability (CO formation instead of CO 2 ), about 90% of available energy above 1500 K (with respect to 23% with flames), a greater energy density, lower gas flow rates, and plasma start-up and shut-down times of only few tenth of seconds. This article presents: 1 - the present day situation of thermal plasmas development; 2 - some general considerations about plasma waste processing; 3 - the plasma processes: liquid toxic wastes, solid wastes (contaminated soils and low level radioactive wastes, military wastes, vitrification of incinerators fly ash, municipal wastes processing, treatment of asbestos fibers, treatment of chlorinated industrial wastes), metallurgy wastes (dusts, aluminium slags), medical and ship wastes, perspectives; 4 -conclusion. (J.S.)

Spectroscopic and Collisional Data for Tungsten from 1 eV to 20 keV. Summary Report of the Second Research Coordination Meeting

International Nuclear Information System (INIS)

Braams, Bastiaan J.

2014-08-01

The second Research Coordination Meeting of a coordinated research project (CRP) on spectroscopic and collisional data for tungsten ions in fusion plasma was held 29-31 August 2012 at Max-Planck- Institute for Nuclear Physics, Heidelberg, Germany. Thirteen projects participate in the CRP and were represented at the meeting together with 8 further experts and 2 IAEA scientific staff. Participants presented their research following which outstanding data needs were identified and a work plan was developed for the remainder of the CRP. The proceedings and conclusions of the meeting are summarized here. (author)

Bremsstrahlung emission coefficient of a plasma in a uniform magnetic field

International Nuclear Information System (INIS)

Pangborn, R.J.

1976-01-01

The leading (electron-ion, dipole) contribution to the bremsstrahlung spectrum of a Maxwellian plasma in a constant, uniform magnetic field is calculated. The plasma is assumed infinite and fully ionized. A simpler, more direct derivation of Kirchoff's Law for anisotropic media is presented. The plasma dispersion relation is then found using previously obtained expressions for the conductivity tensor (accurate to first order in collisional effects). From the dispersion the collisional damping, assumed small, is obtained and by means of Kirchoff's Law an expression for the bremsstrahlung emission coefficient is written. No terms of order (kappa 2 lambda 2 0 ) or higher are included. For wave frequencies large compared with the plasma and electron cyclotron frequencies (ω 2 much greater than ω 2 rho, ω 2 much greater than Ω 3 ) an expansion of the exact result is given accurate to fourth order in Ω/ω and ω rho/ω. The result is found to disagree with previous high frequency expressions. Analysis of the exact expression reveals that for certain frequencies and directions of propagation the emission spectrum exhibits a resonance quality. The results are presented in such fashion that for various magnetic field strengths the frequency of the resonant emission at arbitrary angle relative to the field is easily obtained. These phenomena arise due to the influence of the magnetic fieldon the dielectric properties of the plasma and not because of its effect on the binary collision process. A physical explanation of the results is presented

Research on high energy density plasmas and applications

International Nuclear Information System (INIS)

1999-01-01

Recently, technologies on lasers, accelerators, and pulse power machines have been significantly advanced and input power density covers the intensity range from 10 10 W/cm 2 to higher than 10 20 W/cm 2 . As the results, high pressure gas and solid targets can be heated up to very high temperature to create hot dense plasmas which have never appeared on the earth. The high energy density plasmas opened up new research fields such as inertial confinement fusion, high brightness X-ray radiation sources, interiors of galactic nucleus,supernova, stars and planets, ultra high pressure condensed matter physics, plasma particle accelerator, X-ray laser, and so on. Furthermore, since these fields are intimately connected with various industrial sciences and technologies, the high energy density plasma is now studied in industries, government institutions, and so on. This special issue of the Journal of Plasma Physics and Nuclear Fusion Research reviews the high energy density plasma science for the comprehensive understanding of such new fields. In May, 1998, the review committee for investigating the present status and the future prospects of high energy density plasma science was established in the Japan Society of Plasma Science and Nuclear Fusion Research. We held three committee meetings to discuss present status and critical issues of research items related to high energy density plasmas. This special issue summarizes the understandings of the committee. This special issue consists of four chapters: They are Chapter 1: Physics important in the high energy density plasmas, Chapter 2: Technologies related to the plasma generation; drivers such as lasers, pulse power machines, particle beams and fabrication of various targets, Chapter 3: Plasma diagnostics important in high energy density plasma experiments, Chapter 4: A variety of applications of high energy density plasmas; X-ray radiation, particle acceleration, inertial confinement fusion, laboratory astrophysics

Spontaneous electromagnetic emission from a strongly localized plasma flow.

Science.gov (United States)

Tejero, E M; Amatucci, W E; Ganguli, G; Cothran, C D; Crabtree, C; Thomas, E

2011-05-06

Laboratory observations of electromagnetic ion-cyclotron waves generated by a localized transverse dc electric field are reported. Experiments indicate that these waves result from a strong E×B flow inhomogeneity in a mildly collisional plasma with subcritical magnetic field-aligned current. The wave amplitude scales with the magnitude of the applied radial dc electric field. The electromagnetic signatures become stronger with increasing plasma β, and the radial extent of the power is larger than that of the electrostatic counterpart. Near-Earth space weather implications of the results are discussed.

To the theory of fluctuations in a non-equilibrium plasma with taking into account the particle collisional interaction

International Nuclear Information System (INIS)

Puchkov, V.A.

1998-01-01

A method for calculation of non-equilibrium fluctuations in a totally ionized stable plasma with taking into account the particle collisions is proposed. The spectrum of high-frequency fluctuations of the electric field is calculated by the developed method. The formula obtained for the spectrum takes into consideration both the Coulomb collisions and influence of collective effects on the collisions and is applicable for stable arbitrary distributions of electrons and ions

Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

International Nuclear Information System (INIS)

Stratton, B.C.; Bitter, M.; Hill, K.W.; Hillis, D.L.; Hogan, J.T.

2007-01-01

Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.

Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

Energy Technology Data Exchange (ETDEWEB)

Stratton, B. C.; Biter, M.; Hill, K. W.; Hillis, D. L.; Hogan, J. T.

2007-07-18

Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.

Micro- to macroscale perspectives on space plasmas

International Nuclear Information System (INIS)

Eastman, T.E.

1993-01-01

The Earth's magnetosphere is the most accessible of natural collisionless plasma environments; an astrophysical plasma ''laboratory.'' Magnetospheric physics has been in an exploration phase since its origin 35 years ago but new coordinated, multipoint observations, theory, modeling, and simulations are moving this highly interdisciplinary field of plasma science into a new phase of synthesis and understanding. Plasma systems are ones in which binary collisions are relatively negligible and collective behavior beyond the microscale emerges. Most readily accessible natural plasma systems are collisional and nearest-neighbor classical interactions compete with longer-range plasma effects. Except for stars, most space plasmas are collisionless, however, and the effects of electrodynamic coupling dominate. Basic physical processes in such collisionless plasmas occur at micro-, meso-, and macroscales that are not merely reducible to each other in certain crucial ways as illustrated for the global coupling of the Earth's magnetosphere and for the nonlinear dynamics of charged particle motion in the magnetotail. Such global coupling and coherence makes the geospace environment, the domain of solar-terrestrial science, the most highly coupled of all physical geospheres

Coulomb thermal properties and stability of the Io plasma torus

Science.gov (United States)

Barbosa, D. D.; Coroniti, F. V.; Eviatar, A.

1983-01-01

Coulomb collisional energy exchange rates are computed for a model of the Io plasma torus consisting of newly created pickup ions, a background of thermally degraded intermediary ions, and a population of cooler electrons. The electrons are collisionally heated by both the pickup ions and background ions and are cooled by electron impact excitation of plasma ions which radiate in the EUV. It is found that a relative concentration of S III pickup ions forbidden S III/electrons = 0.1 with a temperature of 340 eV can deliver energy to the electrons at a rate of 3 x 10 to the -13th erg/cu cm per sec, sufficient to power the EUV emissions in the Io torus. The model predicts a background ion temperature Ti of about 53 eV and an electron temperature Te of about 5.5 eV on the basis of steady-state energy balance relations at Coulomb rates. The model also predicts electron temperature fluctuations at the 30 percent level on a time scale of less than 11 hours, consistent with recent observations of this phenomenon.

Density-dependent lines of one- and two-electron ions in diagnostics of laboratory plasma. I. The rates of collision relaxation of excited levels

Energy Technology Data Exchange (ETDEWEB)

Shevelko, V P; Skobelev, I Yu; Vinogradov, A V [Lebedev Physical Institute, Academy of Sciences of the USSR, Moscow, USSR

1977-01-01

Plasma devices with inertial plasma confinement such as laser produced plasmas, exploding wires, plasma focus, etc., which have been rapidly developed during recent years., appear to be very intensive sources of spectral line radiation in far UV and X-ray regions. Analysis of this radiation provides a good tool for plasma diagnostics with very high electron densities up to 10/sup 22/cm/sup -3/. In this work, consisting of two parts, the authors consider the mechanism of the formation of spectral lines in hot and dense plasma. The key point for density diagnostics is the fact that for some ion levels the rate of collisional relaxation has the same order of magnitude as the radiative decay. Thus the intensities of spectral lines arising from these levels show a strong dependence on electron density which makes diagnostics possible. In this paper, emphasis is laid on the calculation of rates of transition between close ion levels induced by electron or ion impact, which usually gives the main contribution to the collisional relaxation constants. The influence of plasma polarization effects on the collision frequency in a dense plasma is also considered.

Whistleron gas in magnetized plasmas

International Nuclear Information System (INIS)

De Martino, Salvatore; Falanga, Mariarosaria; Tzenov, Stephan I.

2005-01-01

The nonlinear dynamics of whistler waves in magnetized plasmas is studied. Since the plasmas and beam-plasma systems considered here are assumed to be weakly collisional, the point of reference for the analysis performed in the present paper is the system of hydrodynamic and field equations. The renormalization group method is applied to obtain dynamical equations for the slowly varying amplitudes of whistler waves. Further, it has been shown that the amplitudes of eigenmodes satisfy an infinite system of coupled nonlinear Schroedinger equations. In this sense, the whistler eigenmodes form a sort of a gas of interacting quasiparticles, while the slowly varying amplitudes can be considered as dynamical variables heralding the relevant information about the system. An important feature of the approach is that whistler waves do not perturb the initial uniform density of plasma electrons. The plasma response to the induced whistler waves consists in velocity redistribution which follows exactly the behavior of the whistlers. In addition, selection rules governing the nonlinear mode coupling have been derived, which represent another interesting peculiarity of the description presented here

Transport of a multiple ion species plasma in the Pfirsch--Schluter regime

International Nuclear Information System (INIS)

Hirshman, S.P.

1976-10-01

The classical parallel friction coefficients, which relate the collisional friction forces to the flow of particles and heat along the magnetic field, are calculated for a multiple ion species plasma. In the short mean free path regime, the neoclassical Pfirsch--Schlueter transport coefficients for a toroidally confined multispecies plasma are computed in terms of the classical friction coefficients. The dependence of the neoclassical cross-field transport on the equilibration of the parallel ion temperature profiles is determined

Confinement of Stellarator plasmas with neutral beam and RF heating in W VII-A

International Nuclear Information System (INIS)

Grieger, G.; Cattanei, G.; Dorst, D.

1986-01-01

WENDELSTEIN VII-A has been operated for ten years. It is a low-shear, high-aspect-ratio device. The confinement properties have been thoroughly studied for both ohmically heated and net-current free plasmas. For the latter case, NBI- and ECF-maintained plasmas were of particular importance. It was found that under optimized conditions the core of high-pressure, net-current free plasmas is mainly governed by collisional effects. The experiment will now be shut down for upgrading it into the Advanced Stellarator WEDNDELSTEIN VII-AS. (author)

Fundamental Processes in Plasmas. Final report

International Nuclear Information System (INIS)

O'Neil, Thomas M.; Driscoll, C. Fred

2009-01-01

This research focuses on fundamental processes in plasmas, and emphasizes problems for which precise experimental tests of theory can be obtained. Experiments are performed on non-neutral plasmas, utilizing three electron traps and one ion trap with a broad range of operating regimes and diagnostics. Theory is focused on fundamental plasma and fluid processes underlying collisional transport and fluid turbulence, using both analytic techniques and medium-scale numerical simulations. The simplicity of these systems allows a depth of understanding and a precision of comparison between theory and experiment which is rarely possible for neutral plasmas in complex geometry. The recent work has focused on three areas in basic plasma physics. First, experiments and theory have probed fundamental characteristics of plasma waves: from the low-amplitude thermal regime, to inviscid damping and fluid echoes, to cold fluid waves in cryogenic ion plasmas. Second, the wide-ranging effects of dissipative separatrices have been studied experimentally and theoretically, finding novel wave damping and coupling effects and important plasma transport effects. Finally, correlated systems have been investigated experimentally and theoretically: UCSD experients have now measured the Salpeter correlation enhancement, and theory work has characterized the 'guiding center atoms of antihydrogen created at CERN

Orbital and Collisional Evolution of the Irregular Satellites

Science.gov (United States)

Nesvorný, David; Alvarellos, Jose L. A.; Dones, Luke; Levison, Harold F.

2003-07-01

The irregular moons of the Jovian planets are a puzzling part of the solar system inventory. Unlike regular satellites, the irregular moons revolve around planets at large distances in tilted and eccentric orbits. Their origin, which is intimately linked with the origin of the planets themselves, is yet to be explained. Here we report a study of the orbital and collisional evolution of the irregular satellites from times after their formation to the present epoch. The purpose of this study is to find out the features of the observed irregular moons that can be attributed to this evolution and separate them from signatures of the formation process. We numerically integrated ~60,000 test satellite orbits to map orbital locations that are stable on long time intervals. We found that the orbits highly inclined to the ecliptic are unstable due to the effect of the Kozai resonance, which radially stretches them so that satellites either escape from the Hill sphere, collide with massive inner moons, or impact the parent planet. We also found that prograde satellite orbits with large semimajor axes are unstable due to the effect of the evection resonance, which locks the orbit's apocenter to the apparent motion of the Sun around the parent planet. In such a resonance, the effect of solar tides on a resonant moon accumulates at each apocenter passage of the moon, which causes a radially outward drift of its orbital apocenter; once close to the Hill sphere, the moon escapes. By contrast, retrograde moons with large orbital semimajor axes are long-lived. We have developed an analytic model of the distant satellite orbits and used it to explain the results of our numerical experiments. In particular, we analytically studied the effect of the Kozai resonance. We numerically integrated the orbits of the 50 irregular moons (known by 2002 August 16) for 108 yr. All orbits were stable on this time interval and did not show any macroscopic variations that would indicate

Dynamic feedback for multi-mode plasma instabilities

International Nuclear Information System (INIS)

Sen, A.K.

1978-01-01

Constant feedback, which has been used exclusively, fails to stabilize more than one mode of a plasma instability. It is shown that a suitable dynamic or frequency-dependent feedback can stabilize all modes. Methods are developed in which such a feedback structure can be chosen in terms of its poles and zeros in relation to those of the plasma transfer function in the complex frequency plane. The synthesis procedure for such a feedback structure, in the form of an integrated electronic circuit is also discussed. As an example, a dynamic feedback for multi-mode stabilization of a collisional drift wave instability is developed in detail. (author)

Current new applications of laser plasmas

International Nuclear Information System (INIS)

Hauer, A.A.; Forslund, D.W.; McKinstrie, C.J.; Wark, J.S.; Hargis, P.J. Jr.; Hamil, R.A.; Kindel, J.M.

1988-09-01

This report describes several new applications of laser-produced plasmas that have arisen in the last few years. Most of the applications have been an outgrowth of the active research in laser/matter interaction inspired by the pursuit of laser fusion. Unusual characteristics of high-intensity laser/matter interaction, such as intense x-ray and particle emission, were noticed early in the field and are now being employed in a significant variety of applications outside the fusion filed. Applications range from biology to materials science to pulsed-power control and particle accelerators. 92 refs., 23 figs., 4 tabs

Collisional history of asteroids - evidence from Vesta and the Hirayama families

International Nuclear Information System (INIS)

Davis, D.R.; Chapman, C.R.; Weidenschilling, S.J.; Greenberg, R.

1985-01-01

Numerical simulations of the collisional evolution of hypothetical initial asteroid populations have been run which are subject to three constraints: they must evolve to the current asteroid size distribution, preserve Vesta's basaltic crust, and produce at least the observed number of major Hirayama families. A runaway growth initial asteroid population distribution is found to best satisfy these constraints, and a model is developed for the calculation of fragment size distribution in the disruption of large, gravitationally bound bodies in which the material strength is enhanced by hydrostatic self-compression. This model predicts that large asteroids behave as intrinsically strong bodies despite histories of collisional fracture. 51 references

Edge plasma density reconstruction for fast monoenergetic lithium beam probing

International Nuclear Information System (INIS)

Sasaki, S.; Takamura, S.; Ueda, M.; Iguchi, H.; Fujita, J.; Kadota, K.

1993-01-01

Two different electron density reconstruction methods for 8-keV neutral lithium beam probing have been developed for the Compact Helical System (CHS). Density dependences on emission and ionization processes are included by using effective rate coefficients obtained from the collisional radiative model. Since the two methods differ in the way the local beam density in the plasma is determined, the methods have different applicable electron densities. The beam attenuation is calculated by iteration from the electron density profile in method I. In method II, the beam remainder at the observation point z is determined by integrating the Li I emission intensity from z toward the position of emission tail-off. At the emission tail-off, the fast lithium beam is completely attenuated. Selecting an appropriate method enables us to obtain edge electron density profile well inside the last closed flux surface for various ranges of plasma densities (10 12 --5x10 13 cm -3 ). The electron density profiles reconstructed by these two different methods are in good agreement with each other and are consistent with results from ruby laser Thomson scattering

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1987-01-01

The steady state behaviour of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is shown that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed in light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (author)

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1986-06-01

The steady state behavior of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is showm that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed on light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (Author) [pt

Collisional avalanche exponentiation of run-away electrons in electrified plasmas

International Nuclear Information System (INIS)

Jayakumar, R.; Fleischmann, H.H.; Zweben, S.J.; Cornell Univ., Ithaca, NY

1992-07-01

In contrast to earlier expectations, it is estimated that generation of runaway electrons from close collisions of existing runaways with cold plasma electrons can be significant even for small electric fields, whenever runaways can gain energies of about 20 MeV or more. In that case, the runaway population will grow exponentially with the energy spectrum showing an exponential decrease towards higher energies.Energy gains of the required magnitude may occur in large Tokamak devices as well as in cosmic-ray generation

Prospective application of laser plasma propulsion in rocket technology

International Nuclear Information System (INIS)

Lu Xin; Zhang Jie; Li Yingjun

2002-01-01

Interest in laser plasma propulsion is growing intensively. The interaction of high intensity short laser pulses with materials can produce plasma expansion with a velocity of hundreds of km/s. The specific impulse of ablative laser propulsion can be many tens of times greater than that of chemical rockets. The development and potential application of laser plasma propulsion are discussed

Multi-scale description of the laser-plasma interaction: application to the physics of shock ignition in inertial confinement fusion

International Nuclear Information System (INIS)

Colaitis, Arnaud

2015-01-01

propagation and energy deposition in plasma is described in the angular scattering approximation, adapted to two-dimensional, transversally Gaussian, multigroup HE beams of arbitrary angular distribution. This model accounts for (i) competition for the laser energy between the various instabilities and with the linear collisional absorption, (ii) coupling between nonlinear LPIs and plasma dynamics via the high energy electron beams and (iii) loss of coupling due to backscattered Raman light. Its performance is confirmed by comparison with measurements of shock timing, laser absorption, HE fluxes and temperatures in experiments conducted on Omega and Pals laser facilities. This multi-scale in line LPI-HE model is used to interpret several Shock Ignition experiments. It is found that HEs from parametric instabilities significantly increase the shock pressure and velocity in the target, while decreasing its strength and the overall ablation pressure. Applications to the high-intensity regime of shock ignition ICF suggest that HEs generated by the nonlinear LPI are nefarious to the capsule implosion in conventional target designs, as they lead to a dramatic increase in the hotspot mass and losses by Bremsstrahlung radiation. This model is readily applicable to hydrodynamic description of laser-target experiments of High Energy Density Physics, in the interaction regimes involving the above-mentioned non-linear LPI processes. (author) [fr

PIC Modeling of Argon Plasma Flow in MNX

Science.gov (United States)

Cohen, Samuel; Sefkow, Adam

2007-11-01

A linear helicon-heated plasma device - the Magnetic Nozzle Experiment (MNX) at the Princeton Plasma Physics Laboratory - is used for studies of the formation of strong electrostatic double layers near mechanical and magnetic apertures and the acceleration of plasma ions into supersonic directed beams. In order to characterize the role of the aperture and its involvement with ion acceleration, detailed particle-in-cell simulations are employed to study the effects of the surrounding boundary geometry on the plasma dynamics near the aperture region, within which the transition from a collisional to collisionless regime occurs. The presence of a small superthermal electron population is examined, and the model includes a background neutral population which can be ionized by energetic electrons. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the formation mechanism of the double layer is investigated.

Application and research of special waste plasma disposal technology

International Nuclear Information System (INIS)

Lan Wei

2007-12-01

The basic concept of plasma and the principle of waste hot plasma disposal technology are simply introduced. Several sides of application and research of solid waste plasma disposal technology are sumed up. Compared to the common technology, the advantages of waste hot plasma disposal technology manifest further. It becomes one of the most prospective and the most attended high tech disposal technology in particular kind of waste disposal field. The article also simply introduces some experiment results in Southwest Institute of Physics and some work on the side of importation, absorption, digestion, development of foreign plasma torch technology and researching new power sources for plasma torch. (authors)

Classical impurity ion confinement in a toroidal magnetized fusion plasma.

Science.gov (United States)

Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S

2012-03-23

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.

Development, diagnostic and applications of radio-frequency plasma reactor

Science.gov (United States)

Puac, N.

2008-07-01

In many areas of the industry, plasma processing of materials is a vital technology. Nonequilibrium plasmas proved to be able to produce chemically reactive species at a low gas temperature while maintaining highly uniform reaction rates over relatively large areas (Makabe and Petrovic 2006). At the same time nonequilibrium plasmas provide means for good and precise control of the properties of active particles that determine the surface modification. Plasma needle is one of the atmospheric pressure sources that can be used for treatment of the living matter which is highly sensitive when it comes to low pressure or high temperatures (above 40 C). Dependent on plasma conditions, several refined cell responses are induced in mammalian cells (Sladek et al. 2005). It appears that plasma treatment may find many biomedical applications. However, there are few data in the literature about plasma effects on plant cells and tissues. So far, only the effect of low pressure plasmas on seeds was investigated. It was shown that short duration pretreatments by non equilibrium low temperature air plasma were stimulative in light induced germination of Paulownia tomentosa seeds (Puac et al. 2005). As membranes of plants have different properties to those of animals and as they show a wide range of properties we have tried to survey some of the effects of typical plasma which is envisaged to be used in biotechnological applications on plant cells. In this paper we will make a comparison between two configurations of plasma needle that we have used in treatment of biological samples (Puac et al. 2006). Difference between these two configurations is in the additional copper ring that we have placed around glass tube at the tip of the needle. We will show some of the electrical characteristics of the plasma needle (with and without additional copper ring) and, also, plasma emission intensity obtained by using fast ICCD camera.

Lithium line radiation in turbulent edge plasmas: Effects of low and high frequency temperature fluctuations

Science.gov (United States)

Rosato, J.; Capes, H.; Catoire, F.; Kadomtsev, M. B.; Levashova, M. G.; Lisitsa, V. S.; Marandet, Y.; Rosmej, F. B.; Stamm, R.

2011-08-01

In lithium-wall-conditioned tokamaks, the line radiation due to the intrinsic impurities (Li/Li+/Li++) plays a significant role on the power balance. Calculations of the radiation losses are usually performed using a stationary collisional-radiative model, assuming constant values for the plasma parameters (Ne, Te,…). Such an approach is not suitable for turbulent plasmas where the various parameters are time-dependent. This is critical especially for the edge region, where the fluctuation rates can reach several tens of percents [e.g. J.A. Boedo, J. Nucl. Mater. 390-391 (2009) 29-37]. In this work, the role of turbulence on the radiated power is investigated with a statistical formalism. A special emphasis is devoted to the role of temperature fluctuations, successively for low-frequency fluctuations and in the general case where the characteristic turbulence frequencies can be comparable to the collisional and radiative rates.

Collisional processes of interest in MFE plasma research

International Nuclear Information System (INIS)

Olson, R.E.

1991-01-01

Research on this grant is devoted to the calculation of heavy particle collision cross sections needed for diagnostic studies of magnetic fusion plasmas. This work requires the development and testing of new theoretical methods, with the implementation of benchmarked techniques to collisions pertinent to fusion reactors. Within the last context, we have provided charge-exchange-recombination cross sections to specific n,l-levels for diagnostic studies on TFTR and for major compilations for the IAEA. We have also completed a cross section study related to the planned neutral beam current drive for ITER. In addition, calculations were made to assess the use of He neutral atom angular scattering measurements for JT-60. Also, new theoretical methods have been developed to more accurately calculate cross sections involving either He or H 2 targets and partially stripped multiply-charged ions. Our most recent work concentrates on alpha particle diagnostics and collision processes of ''helium ash'' in burning reactors. Here, we are providing atomic cross section data for the carbon pellet alpha particle diagnostic work at General Atomics and the neutral He beam alpha particle diagnostic under study by the IAEA

Development of collisional data base for elementary processes of electron scattering by atoms and molecules

Energy Technology Data Exchange (ETDEWEB)

Marinković, Bratislav P., E-mail: bratislav.marinkovic@ipb.ac.rs [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); School of Electrical and Computer Engineering of Applied Studies, Vojvode Stepe 283, 11000 Belgrade (Serbia); Vujčić, Veljko [Astronomical Observatory Belgade, Volgina 7, 11050 Belgrade (Serbia); Faculty of Organizational Sciences, University of Belgrade, Jove Ilića 154, 11000 Belgrade (Serbia); Sushko, Gennady [MBN Research Center, Altenhöferallee 3, 60438 Frankfurt am Main (Germany); Vudragović, Dušan [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Marinković, Dara B. [Faculty of Organizational Sciences, University of Belgrade, Jove Ilića 154, 11000 Belgrade (Serbia); Đorđević, Stefan; Ivanović, Stefan; Nešić, Milutin [School of Electrical and Computer Engineering of Applied Studies, Vojvode Stepe 283, 11000 Belgrade (Serbia); Jevremović, Darko [Astronomical Observatory Belgade, Volgina 7, 11050 Belgrade (Serbia); Solov’yov, Andrey V. [MBN Research Center, Altenhöferallee 3, 60438 Frankfurt am Main (Germany); Mason, Nigel J. [The Open University, Department of Physical Sciences, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

2015-07-01

Highlights: • BEAMDB database maintaining electron/atom-molecule collisional data has been created. • The DB is MySQL, the web server is Nginx and Python application server is Gunicorn. • Only data that have been previously published and formally refereed are included. • Data protocol for exchanging and representing data is in the “xsams” xml format. • BEAMDB becomes a node within the VAMDC consortium and radiation damage RADAM basis. - Abstract: We present a progress report on the development of the Belgrade electron/molecule data base which is hosted by The Institute of Physics, University of Belgrade and The Astronomical Observatory Belgrade. The data base has been developed under the standards of Virtual Atomic Molecular Data Centre (VAMDC) project which provides a common portal for several European data bases that maintain atomic and molecular data. The Belgrade data base (BEAMDB) covers collisional data of electron interactions with atoms and molecules in the form of differential (DCS) and integrated cross sections as well as energy loss spectra. The final goal of BEAMDB becoming both a node within the VAMDC consortium and within the radiation damage RADAM data base has been achieved.

Semiconductor applications of plasma immersion ion implantation ...

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 25; Issue 6. Semiconductor applications of plasma immersion ion implantation technology ... Department of Electronic Science, Kurukshetra University, Kurukshetra 136 119, India ...

Effects of plasma on polyethylene fiber surface for prosthodontic application

Directory of Open Access Journals (Sweden)

Silvana Marques Miranda SPYRIDES

2015-12-01

Full Text Available ABSTRACT Plasma technology has the potential to improve the adherence of fibers to polymeric matrices, and there are prospects for its application in dentistry to reinforce the dental particulate composite. Objectives This study aimed to investigate the effect of oxygen or argon plasma treatment on polyethylene fibers. Material and Methods Connect, Construct, InFibra, and InFibra treated with oxygen or argon plasma were topographically evaluated by scanning electron microscopy (SEM, and chemically by X-ray photoelectron spectroscopy (XPS. For bending analysis, one indirect composite (Signum was reinforced with polyethylene fiber (Connect, Construct, or InFibra. The InFibra fiber was subjected to three different treatments: (1 single application of silane, (2 oxygen or argon plasma for 1 or 3 min, (3 oxygen or argon plasma and subsequent application of silane. The samples (25x2x2 mm, 6 unreinforced and 60 reinforced with fibers, were subjected to three-point loading tests to obtain their flexural strength and deflection. The results were statistically analyzed with ANOVA and the Bonferroni correction for multiple comparison tests. Results SEM analysis showed that oxygen and argon plasma treatments promote roughness on the polyethylene fiber surface. X-ray photoelectron spectroscopy (XPS analysis shows that both plasmas were effective in incorporating oxygenated functional groups. Argon or oxygen plasma treatment affected the flexural strength and deflection of a fiber reinforced composite. The application of silane does not promote an increase in the flexural strength of the reinforced composites. Conclusions Oxygen and argon plasma treatments were effective in incorporating oxygenated functional groups and surface roughness. The highest strength values were obtained in the group reinforced with polyethylene fibers treated with oxygen plasma for 3 min.

Radial variation of refractive index, plasma frequency and phase velocity in laser induced air plasma

CSIR Research Space (South Africa)

Mathuthu, M

2006-12-01

Full Text Available is the concentration of the emitting species, is the transition probability, is the emitted wavelength of the detected line, is the statistical weight of the upper level of the transition, is the excitation energy, is the Boltzmann constant, and is the partition... the Boltzmann plane: (3) For each species in a sample, the slope gives the plasma tem- perature while the intercept gives the sample concentration. B. Density Measurement The collisional processes between atoms and ions affect the shape and width...

Temperature Measurements of Dense Plasmas by Detailed Balance

International Nuclear Information System (INIS)

Holl, A; Redmer, R; Ropke, G; Reinholz, H; Thiele, R; Fortmann, C; Forster, E; Cao, L; Tschentscher, T; Toleikis, S; Glenzer, S H

2006-01-01

Plasmas at high electron densities of n e = 10 20 - 10 26 cm -3 and moderate temperatures T e = 1 - 20 eV are important for laboratory astrophysics, high energy density science and inertial confinement fusion. These plasmas are usually referred to as Warm Dense Matter (WDM) and are characterized by a coupling parameter of Λ ∼> 1 where correlations become important. The characterization of such plasmas is still a challenging task due to the lack of direct measurement techniques for temperatures and densities. They propose to measure the Thomson scattering spectrum of vacuum-UV radiation off density fluctuations in the plasma. Collective Thomson scattering provides accurate data for the electron temperature applying first principles. Further, this method takes advantage of the spectral asymmetry resulting from detailed balance and is independent of collisional effects in these dense systems

Population decay time and distribution of exciton states analyzed by rate equations based on theoretical phononic and electron-collisional rate coefficients

Science.gov (United States)

Oki, Kensuke; Ma, Bei; Ishitani, Yoshihiro

2017-11-01

Population distributions and transition fluxes of the A exciton in bulk GaN are theoretically analyzed using rate equations of states of the principal quantum number n up to 5 and the continuum. These rate equations consist of the terms of radiative, electron-collisional, and phononic processes. The dependence of the rate coefficients on temperature is revealed on the basis of the collisional-radiative model of hydrogen plasma for the electron-collisional processes and theoretical formulation using Fermi's "golden rule" for the phononic processes. The respective effects of the variations in electron, exciton, and lattice temperatures are exhibited. This analysis is a base of the discussion on nonthermal equilibrium states of carrier-exciton-phonon dynamics. It is found that the exciton dissociation is enhanced even below 150 K mainly by the increase in the lattice temperature. When the thermal-equilibrium temperature increases, the population fluxes between the states of n >1 and the continuum become more dominant. Below 20 K, the severe deviation from the Saha-Boltzmann distribution occurs owing to the interband excitation flux being higher than the excitation flux from the 1 S state. The population decay time of the 1 S state at 300 K is more than ten times longer than the recombination lifetime of excitons with kinetic energy but without the upper levels (n >1 and the continuum). This phenomenon is caused by a shift of population distribution to the upper levels. This phonon-exciton-radiation model gives insights into the limitations of conventional analyses such as the ABC model, the Arrhenius plot, the two-level model (n =1 and the continuum), and the neglect of the upper levels.

Plasma fluctuation measurements in tokamaks using beam-plasma interactions

International Nuclear Information System (INIS)

Fonck, R.J.; Duperrex, P.A.; Paul, S.F.

1990-01-01

High-frequency observations of light emitted from the interactions between plasma ions and injected neutral beam atoms allow the measurement of moderate-wavelength fluctuations in plasma and impurity ion densities. To detect turbulence in the local plasma ion density, the collisionally excited fluorescence from a neutral beam is measured either separately at several spatial points or with a multichannel imaging detector. Similarly, the role of impurity ion density fluctuations is measured using charge exchange recombination excited transitions emitted by the ion species of interest. This technique can access the relatively unexplored region of long-wavelength plasma turbulence with k perpendicular ρ i much-lt 1, and hence complements measurements from scattering experiments. Optimization of neutral beam geometry and optical sightlines can result in very good localization and resolution (Δx≤1 cm) in the hot plasma core region. The detectable fluctuation level is determined by photon statistics, atomic excitation processes, and beam stability, but can be as low as 0.2% in a 100 kHz bandwidth over the 0--1 MHz frequency range. The choices of beam species (e.g., H 0 , He 0 , etc.), observed transition (e.g., H α , L α , He I singlet or triplet transitions, C VI Δn=1, etc.) are dictated by experiment-specific factors such as optical access, flexibility of beam operation, plasma conditions, and detailed experimental goals. Initial tests on the PBX-M tokamak using the H α emissions from a heating neutral beam show low-frequency turbulence in the edge plasma region

Electrical field excitation in non-uniform plasma by a modulated electron beam

International Nuclear Information System (INIS)

Anisimov, I.O.; Borisov, O.A.

2000-01-01

Excitation of electric fields due to a modulated electron beam in a warm non-uniform plasma is treated for weak beams in warm plasma. It is shown that the maximum electric field magnitude that is reached near the local plasma resonance point depends significantly on the direction of the electron stream motion. In collisional plasma the magnitude of the Langmuir wave that propagates to the subcritical plasma also depends on the direction of the electron stream motion. The motion of the modulated electron stream front results in beatings between oscillations on the modulation frequency and on the local electron plasma frequencies at the initial moment. Later these beatings damp in the supercritical plasma, whereas in the subcritical plasma they are transformed into spatial beatings between the field of the modulated electron stream and the excited Langmuir wave. (orig.)

Collisional dynamics of perturbed particle disks in the solar system

Science.gov (United States)

Roberts, W. W.; Stewart, G. R.

1987-01-01

Investigations of the collisional evolution of particulate disks subject to the gravitational perturbation of a more massive particle orbiting within the disk are underway. Both numerical N-body simulations using a novel collision algorithm and analytical kinetic theory are being employed to extend our understanding of perturbed disks in planetary rings and during the formation of the solar system. Particular problems proposed for investigation are: (1) The development and testing of general criteria for a small moonlet to clear a gap and produce observable morphological features in planetary rings; (2) The development of detailed models of collisional damping of the wavy edges observed on the Encke division of Saturn's A ring; and (3) The determination of the extent of runaway growth of the few largest planetesimals during the early stages of planetary accretion.

Plane wave interaction with a homogeneous warm plasma sphere

International Nuclear Information System (INIS)

Ruppin, R.

1975-01-01

A Mie type theory for the scattering and absorption properties of a homogeneous warm plasma sphere is developed. The theory is applied to the calculation of the extinction cross section of plasma spheres, and the effects of Landau damping and collisional damping on the spectra are discussed. The dependence of the main resonance and of the Tonks-Dattner resonances on the physical parameters characterizing the sphere and its surroundings is investigated. The spectrum is shown to be insenitive to the boundary conditions which specify the behaviour of the electrons at the surface of the sphere (author)

Kinetic simulations in plasmas: a general view and some applications

Energy Technology Data Exchange (ETDEWEB)

Alves, Maria Virginia [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: alves@plasma.inpe.br

1999-07-01

In these lecture notes we talk about kinetic simulations plasma physics. We present a general view of the different approach that can be given to kinetic plasmas depending on the physical problem to be investigated. Some applications of kinetic simulations to space plasma phenomena and Pierce electrodes are introduced. (author)

Kinetic simulations in plasmas: a general view and some applications

International Nuclear Information System (INIS)

Alves, Maria Virginia

1999-01-01

In these lecture notes we talk about kinetic simulations plasma physics. We present a general view of the different approach that can be given to kinetic plasmas depending on the physical problem to be investigated. Some applications of kinetic simulations to space plasma phenomena and Pierce electrodes are introduced. (author)

Onset of the radial electric field oscillations in the neoclassical plasmas

International Nuclear Information System (INIS)

Liu, C.S.; Novakovskii, S.V.; Sagdeev, R.Z.; Galeev, A.A.

1996-01-01

It is shown that the relaxation of the radial electric field in the tokomak plasmas towards its neoclassical value is accompanied by the fast oscillations of the order of the ion transient frequency V T /qR. This happens during the transition from the Pfirsch-Schluter collisional regime to the plateau regime at v c qR/V T ≤ c cr ≤ 1. The investigation has been performed with the help of the specially developed numerical code for solution of the nonsteady-state drift kinetic equation with the exact collisional term in the Hirshman-Sigmar-Clarke form. Comparison with the analytical results, corresponding to the regime of the very low collisions as well as with previous approximate models for the plateau regime will also be reported

Weakly ionized plasmas in aerospace applications

International Nuclear Information System (INIS)

Semenov, V E; Bondarenko, V G; Gildenburg, V B; Gubchenko, V M; Smirnov, A I

2002-01-01

This paper is an overview of the activity and state-of-the-art in the field of plasma aerospace applications. Both experimental results and theoretical ideas are analysed. Principal attention is focused on understanding the physical mechanisms of the plasma effect on hypersonic aerodynamics. In particular, it is shown that drag reduction can be achieved using a proper distribution of heat sources around a flying body. Estimates of the energetic efficiency of the thermal mechanism of aerodynamic drag reduction are presented. The non-thermal effect caused by the interaction of a plasma flow with a magnetic field is also analysed. Specifically, it is shown that appropriate spatial distribution of volumetric forces around a hypersonic body allows for complete elimination of shock wave generation. It should be noted that in an ideal case, shock waves could be eliminated without energy consumption

Department of Plasma Physics and Technology - Overview

International Nuclear Information System (INIS)

Rabinski, M.

2008-01-01

Full text: The activities of the Department in 2007 continued previous studies in the following fields of plasma physics, controlled nuclear fusion and plasma technology of surface engineering: · Studies of physical phenomena in pulsed discharges in the Plasma-Focus (PF) and RPI-IBIS facilities; · Development of selected methods for high-temperature plasma diagnostics; · Research on plasma technologies; · Selected problems of plasma theory and computational modelling. As for the experimental studies particular attention was paid to the analysis of the correlation of X-ray pulses with pulsed electron beams and other corpuscular emissions from different Plasma-Focus (PF) facilities. A collisional-radiative model, taking into account the Stark effect and strong electric fields in the so called '' hot- spot '' regions of a pinch, was applied in those analyses. The main aim of these studies was to identify the physical phenomena responsible for the emission during the PF-type discharges. The emitted protons were also measured with nuclear track detectors. The measurements made it possible to obtain images of the regions, where the D-D fusion reactions occurred, as well as to determine the angular distribution of the emitted protons. Pulsed plasma streams were also investigated by means of time-resolved optical spectroscopy and corpuscular diagnostics. In a frame of the EURATOM program, efforts were devoted to the development of diagnostic methods for tokamak-type facilities. Such studies include the design and construction of the 4-channel Cherenkov-type detection system for the TORE-SUPRA tokamak at CEA-Cadarache. In the meantime in order to collect some experience a new measuring head was especially prepared for experiments within small facilities. Other fusion- oriented efforts are connected with the application of the solid-state nuclear track detectors for investigation of protons from tokamak plasma and high-energy beams emitted from laser produced plasmas

Instabilities, turbulence and transport in a magnetized plasma; Instabilites, turbulence et transport dans un plasma magnetise

Energy Technology Data Exchange (ETDEWEB)

Garbet, X

2001-06-01

The purpose of this work is to introduce the main processes that occur in a magnetized plasma. During the last 2 decades, the understanding of turbulence has made great progress but analytical formulas and simulations are far to produce reliable predictions. The values of transport coefficients in a tokamak plasma exceed by far those predicted by the theory of collisional transport. This phenomenon is called abnormal transport and might be due to plasma fluctuations. An estimation of turbulent fluxes derived from the levels of fluctuations, is proposed. A flow description of plasma allows the understanding of most micro-instabilities. The ballooning representation deals with instabilities in a toric geometry. 3 factors play an important role to stabilize plasmas: density pinch, magnetic shear and speed shear. The flow model of plasma gives an erroneous value for the stability threshold, this is due to a bad description of the resonant interaction between wave and particle. As for dynamics, flow models can be improved by adding dissipative terms so that the linear response nears the kinetic response. The kinetic approach is more accurate but is complex because of the great number of dimensions involved. (A.C.)

Resonantly enhanced collisional ionization measurements of radionuclides

International Nuclear Information System (INIS)

Whitaker, T.J.; Bushaw, B.A.; Gerke, G.K.

1986-01-01

The authors developed a new laser technique to analyze for radionuclides at extremely low levels. The technique, called resonantly enhanced collisional ionization (RECI), uses two nitrogen-laser pumped dye lasers to excite the target isotope to a high-energy Rydberg state. Atoms in these Rydberg states (within a few hundred wavenumbers in energy from the ionization threshold) efficiently ionize upon colliding with an inert gas and the ions can be detected by conventional means. The principal advantage of resonantly-enhanced collisional ionization is the extreme sensitivity coupled with its relative simplicity and low cost. Actinides typically have an ionization potential of about 6eV (uranium I.P. = 6.2 eV, plutonium I.P. = 5.7 eV). Two-step laser excitation to a state just below threshold requires wavelengths in the blue region of the visible spectrum. They showed that when both steps in the excitation process are resonant steps, relatively low-power lasers can populate the Rydberg state with almost unit efficiency. This is because the resonant excitations have much larger cross-sections than do photoionization processes. They also demonstrated that a few torr of a buffer gas will cause most of the excited-state atoms to be ionized

Computer simulation of plasma behavior in open-ended linear theta machines. Scientific report 81-5

International Nuclear Information System (INIS)

Stover, E.K.

1981-04-01

Zero-dimensional and one-dimensional fluid plasma computer models have been developed to study the behavior of linear theta pinch plasmas. Computer simulation results generated from these codes are compared with data obtained from two theta pinch experiments so that significant machine plasma behavior can be identified. The experiments examined are a collisional experiment, T/sub i/ approx. 50 eV, n/sub e/ approx. 10 17 cm -3 , where the plasma mean-free-path was significantly less than the plasma column length, and a hot ion species experiment, T/sub i/ approx. 3 keV, n/sub e/ approx. 10 16 cm -3 , where the ion mean-free-path was on the order of the plasma column length

Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis.

Science.gov (United States)

Ter-Avetisyan, S; Ramakrishna, B; Doria, D; Sarri, G; Zepf, M; Borghesi, M; Ehrentraut, L; Stiel, H; Steinke, S; Priebe, G; Schnürer, M; Nickles, P V; Sandner, W

2009-10-01

Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.

Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis

International Nuclear Information System (INIS)

Ter-Avetisyan, S.; Ramakrishna, B.; Doria, D.; Sarri, G.; Zepf, M.; Borghesi, M.; Ehrentraut, L.; Stiel, H.; Steinke, S.; Schnuerer, M.; Nickles, P. V.; Sandner, W.; Priebe, G.

2009-01-01

Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.

Application of piezodetectors for diagnostics of pulsed and quasi-steady-state plasma streams

Energy Technology Data Exchange (ETDEWEB)

Bandura, A.N.; Chebotarev, V.V.; Garkusha, I.E.; Tereshin, V.I.; Ladygina, M.S. [NSC KIPT, Kharkov (Ukraine). Inst. of Plasma Physics

2006-04-15

The paper reports on studies of the plasma streams generated by two experimental devices: the quasi-steady-state plasma accelerator (QSPA) Kh-50 and the pulsed plasma gun PROSVET. The radial distributions of the plasma pressure for different times and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerators. In experiments for the application of pulsed plasma streams for surface modification of different industrial steels, optimal regimes of surface processing have been chosen on the basis of the plasma pressure measurements. Examples of application of the piezodetectors in simulation experiments on plasma surface interaction under high heat loads are presented.

Application of piezodetectors for diagnostics of pulsed and quasi-steady-state plasma streams

International Nuclear Information System (INIS)

Bandura, A.N.; Chebotarev, V.V.; Garkusha, I.E.; Tereshin, V.I.; Ladygina, M.S.

2006-01-01

The paper reports on studies of the plasma streams generated by two experimental devices: the quasi-steady-state plasma accelerator (QSPA) Kh-50 and the pulsed plasma gun PROSVET. The radial distributions of the plasma pressure for different times and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerators. In experiments for the application of pulsed plasma streams for surface modification of different industrial steels, optimal regimes of surface processing have been chosen on the basis of the plasma pressure measurements. Examples of application of the piezodetectors in simulation experiments on plasma surface interaction under high heat loads are presented

Collisional model for granular impact dynamics.

Science.gov (United States)

Clark, Abram H; Petersen, Alec J; Behringer, Robert P

2014-01-01

When an intruder strikes a granular material from above, the grains exert a stopping force which decelerates and stops the intruder. Many previous studies have used a macroscopic force law, including a drag force which is quadratic in velocity, to characterize the decelerating force on the intruder. However, the microscopic origins of the force-law terms are still a subject of debate. Here, drawing from previous experiments with photoelastic particles, we present a model which describes the velocity-squared force in terms of repeated collisions with clusters of grains. From our high speed photoelastic data, we infer that "clusters" correspond to segments of the strong force network that are excited by the advancing intruder. The model predicts a scaling relation for the velocity-squared drag force that accounts for the intruder shape. Additionally, we show that the collisional model predicts an instability to rotations, which depends on the intruder shape. To test this model, we perform a comprehensive experimental study of the dynamics of two-dimensional granular impacts on beds of photoelastic disks, with different profiles for the leading edge of the intruder. We particularly focus on a simple and useful case for testing shape effects by using triangular-nosed intruders. We show that the collisional model effectively captures the dynamics of intruder deceleration and rotation; i.e., these two dynamical effects can be described as two different manifestations of the same grain-scale physical processes.

Recombination emissions and spectral blueshift of pump radiation from ultrafast laser induced plasma in a planar water microjet

Science.gov (United States)

Anija, M.; Philip, Reji

2009-09-01

We report spectroscopic investigations of an ultrafast laser induced plasma generated in a planar water microjet. Plasma recombination emissions along with the spectral blueshift and broadening of the pump laser pulse contribute to the total emission. The laser pulses are of 100 fs duration, and the incident intensity is around 10 15 W/cm 2. The dominant mechanisms leading to plasma formation are optical tunnel ionization and collisional ionization. Spectrally resolved polarization measurements show that the high frequency region of the emission is unpolarized whereas the low frequency region is polarized. Results indicate that at lower input intensities the emission arises mainly from plasma recombinations, which is accompanied by a weak blueshift of the incident laser pulse. At higher input intensities strong recombination emissions are seen, along with a broadening and asymmetric spectral blueshift of the pump laser pulse. From the nature of the blueshifted laser pulse it is possible to deduce whether the rate of change of free electron density is a constant or variable within the pulse lifetime. Two input laser intensity regimes, in which collisional and tunnel ionizations are dominant respectively, have been thus identified.

5-D simulation study of suprathermal electron transport in non-axisymmetric plasmas

International Nuclear Information System (INIS)

Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.

2000-01-01

ECRH driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5-D phase space. Two different phases of the ECRH driven transport of suprathermal electrons can be seen. The first is a rapid convective phase due to the direct radial motion of trapped electrons and the second is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile in W7-AS is clarified. The ECRH driven flux is also evaluated and considered in relation to the 'electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity, and thus the observed electron root feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. A possible scenario for this type of electron root is considered for the LHD plasma. (author)

5D simulation study of suprathermal electron transport in non-axisymmetric plasmas

International Nuclear Information System (INIS)

Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.

1999-01-01

ECRH-driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5D phase space. Two different phases of the ECRH-driven transport of suprathermal electrons can be seen; one is a rapid convective phase due to the direct radial motion of trapped electrons and the other is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile is clarified in W7-AS. The ECRH driven flux is also evaluated and put in relation with the 'electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity and, thus, the observed 'electron root' feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. The possible scenario of this 'ECRH-driven electron root' is considered in the LHD plasma. (author)

Dependence of the electron Langmuir wave damping on the angle of propagation in weakly ionized neon plasma

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

Improved break-in-slope analysis of the plasma energy response in tokamaks

International Nuclear Information System (INIS)

Lerche, E A; Eester, D van

2008-01-01

The break-in-slope method is a simple-although powerful-data analysis technique that is commonly used to determine the power absorption profiles of the plasma species during auxiliary heating experiments in tokamaks. It is based on the study of the energy response of the particles to sudden changes in the external power applied to the plasma. Even though some experimental conditions are favorable for the straightforward application of the break-in-slope analysis in its most simple form (linear fit of the experimental temperature signals), most situations require the retention of additional terms in the linearized energy conservation equation for a successful use of this technique. In this paper, important corrections necessary to extend the applicability of the traditional break-in-slope technique will be presented: (i) the numerical determination of the break-in-slope instants in the plasma energy response allowing the study of indirect (collisional) heating scenarios; (ii) the inclusion of the density variations due to the external power step based on fast density measurements; (iii) the exponential representation of the plasma energy evolution after the power break, describing the saturation of the experimental signals in slow modulation or single power step experiments; (iv) a first assessment of the influence of the change in the radiated power on the break-in-slope results. As will be shown, these corrections are particularly important in low absorption scenarios and in single power step studies, where the change in the external power cannot be considered 'non-perturbative' and the standard break-in-slope analysis usually leads to integrated power levels well below the actual power injected into the plasma

Development in Diagnostics Application to Control Advanced Tokamak Plasma

International Nuclear Information System (INIS)

Koide, Y.

2008-01-01

For continuous operation expected in DEMO, all the plasma current must be non-inductively driven, with self-generated neoclassical bootstrap current being maximized. The control of such steady state high performance tokamak plasma (so-called 'Advanced Tokamak Plasma') is a challenge because of the strong coupling between the current density, the pressure profile and MHD stability. In considering diagnostic needs for the advanced tokamak research, diagnostics for MHD are the most fundamental, since discharges which violate the MHD stability criteria either disrupt or have significantly reduced confinement. This report deals with the development in diagnostic application to control advanced tokamak plasma, with emphasized on recent progress in active feedback control of the current profile and the pressure profile under DEMO-relevant high bootstrap-current fraction. In addition, issues in application of the present-day actuators and diagnostics for the advanced control to DEMO will be briefly addressed, where port space for the advanced control may be limited so as to keep sufficient tritium breeding ratio (TBR)

Modelling of the dual frequency capacitive sheath in the intermediate pressure range

International Nuclear Information System (INIS)