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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,567 records · Page 87
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DOE OSTI2010

The ALICE Electromagnetic Calorimeter

ALICE (A Large Ion Collider Experiment) is the only LHC experiment at CERN fully dedicated to the study of the quark and gluon plasma. Driven by the RHIC results on jet quenching, the ALICE collaboration has proposed to extend the capabilities of the ALICE detector for the study of high momentum photons and jets by adding a large acceptance calorimeter. This EMCal (ElectroMagnetic Calorimeter) is designed to provide an unbiased fast high-p{sub T} trigger and to measure the neutral energy of jets and photons up to 200 GeV. Four over ten supermodules of the calorimeter have been installed and commissioned at CERN in 2009 which represents 40% of the full acceptance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Analytic model of electromagnetic ion-cyclotron anisotropy instability

In the present paper, the real frequency and growth rate associated with the electromagnetic ion cyclotron instability driven by temperature anisotropy are analytically modeled on the basis of conjecture and upon comparison with numerical roots of the dispersion relation. The ions are assumed to have an anisotropic distribution function with Maxwellian parallel distribution. Under such an assumption complex roots of the dispersion relation depend only on two dimensionless parameters, namely, the temperature anisotropy factor A=T{sub perpendiculari}/T{sub ||}i-1, where T{sub perpendiculari} and T{sub ||i} are the perpendicular and parallel ion temperatures, respectively, and the parallel ion beta, {beta}=(8{pi}nT{sub i}/B{sup 2}){sup 1/2}, where n and B are the plasma density and magnetic field intensity, respectively. The ion-cyclotron instability is thus heuristically modeled by complex frequency which is parametrically dependent on A and {beta}. The present result constitutes a useful shortcut research tool that may be employed in a wide variety of applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Chaotic electron trajectories in an electromagnetic wiggler free-electron laser with ion-channel guiding

Chaotic behavior of an electron motion in combined backward propagating electromagnetic wiggler and ion-channel electrostatic fields is studied. The Poincare surface-of-sections are employed to investigate chaotic behavior of electron motion. It is shown that the electron motion can exhibit chaotic behavior when the ion-channel density is low or medium, while for sufficiently high ion-channel density, the electron motion becomes regular (nonchaotic). Also, the chaotic trajectories decrease when the effects of self-fields of electron beam are taken into account and under Budker condition all trajectories become regular. The above result is in contrast with magnetostatic helical wiggler with axial magnetic field in which chaotic motion is produced by self-fields of electron beam. The chaotic and nonchaotic electron trajectories are confirmed by calculating Liapunov exponents.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Derivation via free energy conservation constraints of gyrofluid equations with finite-gyroradius electromagnetic nonlinearities

The derivation of electromagnetic gyrofluid equations is made systematic by using the Hermite polynomial form of the underlying delta-f gyrokinetic distribution function. The gyrokinetic free-energy functional is explicitly used to set up the model. The gyrofluid free energy follows directly. The interaction term in the gyrokinetic Lagrangian is used to obtain the gyrofluid counterpart, from which the polarization equation follows. One closure rule is decided for taking moments over the kinetic gyroaveraging operator. These steps fix the rest of the derivation of the conservative part of the gyrofluid equations. Dissipation is then added in a form to obtain positive definite dissipation and to obtain the collisional fluid equations in their appropriate limit. Existing results are recovered, with the addition of a completely consistent model for finite gyroradius effects in the nonlinearities responsible for magnetic reconnection.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Dry calibration of electromagnetic flowmeters based on numerical models combining multiple physical phenomena (multiphysics)

This paper presents a method for dry calibration of an electromagnetic flowmeter (EMF). This method, which determines the voltage induced in the EMF as conductive liquid flows through a magnetic field, numerically solves a coupled set of multiphysical equations with measured boundary conditions for the magnetic, electric, and flow fields in the measuring pipe of the flowmeter. Specifically, this paper details the formulation of dry calibration and an efficient algorithm (that adaptively minimizes the number of measurements and requires only the normal component of the magnetic flux density as boundary conditions on the pipe surface to reconstruct the magnetic field involved) for computing the sensitivity of EMF. Along with an in-depth discussion on factors that could significantly affect the final precision of a dry calibrated EMF, the effects of flow disturbance on measuring errors have been experimentally studied by installing a baffle at the inflow port of the EMF. Results of the dry calibration on an actual EMF were compared against flow-rig calibration; excellent agreements (within 0.3%) between dry calibration and flow-rig tests verify the multiphysical computation of the fields and the robustness of the method. As requiring no actual flow, the dry calibration is particularly useful for calibrating large-diameter EMFs where conventional flow-rig methods are often costly and difficult to implement.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2010

Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth {delta}{sub a} when {delta}{sub a}<<L, in agreement with previous authors. Furthermore, for {delta}{sub a}>>L, the heating is shown to decay with 1/{delta}{sub a}{sup 3}. The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Terahertz generation and power limits in In{sub 0.53}Ga{sub 0.47}As photomixer coupled to transverse-electromagnetic-horn antenna driven at 1.55 {mu}m wavelengths

We report continuous wave generation at frequencies up to 2 THz using ion-irradiated In{sub 0.53}Ga{sub 0.47}As photomixers coupled to transverse-electromagnetic-horn antennae driven at {approx}1.55 {mu}m wavelength. Output powers up to 0.1 {mu}W at 700 GHz have been achieved. The dependence of the output power on incident optical power and the bias voltage is analyzed in the both regimes of Ohmic transport and recombination-limited transport. The fundamental limitations of the performance of the photomixer devices based on photoconductive phenomenon in recombination-limited transport are analyzed.

36 MATERIALS SCIENCE↗
DOE OSTI2010

High-Isp Mode Of Pulsed Laser-Electromagnetic Hybrid Accelerator For Space Propulsion Applications

A fundamental study of a newly developed rectangular pulsed laser-electromagnetic hybrid thruster was conducted. Laser-ablation plasma in the thruster was induced through laser beam irradiation onto a solid target and accelerated by electrical means instead of direct acceleration only by using a laser beam. The performance of the thrusters was evaluated by measuring the mass shot and impulse bit. As results, significantly high specific impulses up to 7,200 sec were obtained at the charge energies of 8.6 J. In addition, typical thrust efficiency varied between 11.8% and 21.3% depending on the charge energy.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 {mu}F, 50 to 200 nH, and 1 to 3 kV, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Inclusive electromagnetic decay ratios of heavy quarkonium from QCD

We consider a different power counting in potential NRQCD by incorporating the static potential exactly in the leading order Hamiltonian. We compute the leading relativistic corrections to the inclusive electromagnetic decay ratios in this new scheme. The effect of this new power counting is found to be large (even for top). We produce an updated value for the {eta}{sub b} decay to two photons. This scheme also brings consistency between the weak coupling computation and the experimental value of the charmonium decay ratio.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Secondary instability of electromagnetic ion-temperature-gradient modes for zonal flow generation

An analytical model for zonal flow generation by toroidal ion-temperature-gradient (ITG) modes, including finite {beta} electromagnetic effects, is derived. The derivation is based on a fluid model for ions and electrons and takes into account both linear and nonlinear {beta} effects. The influence of finite plasma {beta} on the zonal flow growth rate ({gamma}{sub ZF}) scaling is investigated for typical tokamak plasma parameters. The results show the importance of the zonal flows close to marginal stability where {gamma}{sub ZF}/{gamma}{sub ITG} >> 1 is obtained. In this region the parameter {gamma}{sub ZF}/{gamma}{sub ITG} increases with {beta}, indicating that the ITG turbulence and associated transport would decrease with {beta} at a faster rate than expected from a purely linear or quasi-linear analysis.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Observation of plasma density dependence of electromagnetic soliton excitation by an intense laser pulse

The experimental evidence of the correlation between the initial electron density of the plasma and electromagnetic soliton excitation at the wake of an intense (10{sup 19} W/cm{sup 2}) and short (1 ps) laser pulse is presented. The spatial distribution of the solitons, together with their late time evolution into post-solitons, is found to be dependent upon the background plasma parameters, in agreement with published analytical and numerical findings. The measured temporal evolution and electrostatic field distribution of the structures are consistent with their late time evolution and the occurrence of multiple merging of neighboring post-solitons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF{sub 6}.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Two-fluid electromagnetic simulations of plasma-jet acceleration with detailed equation-of-state

We describe a new particle-based two-fluid fully electromagnetic algorithm suitable for modeling high density (n{sub i} {approx} 10{sup 17} cm{sup -3}) and high Mach number laboratory plasma jets. In this parameter regime, traditional particle-in-cell (PIC) techniques are challenging due to electron timescale and lengthscale constraints. In this new approach, an implicit field solve allows the use of large timesteps while an Eulerian particle remap procedure allows simulations to be run with very few particles per cell. Hall physics and charge separation effects are included self-consistently. A detailed equation of state (EOS) model is used to evolve the ion charge state and introduce non-ideal gas behavior. Electron cooling due to radiation emission is included in the model as well. We demonstrate the use of these new algorithms in 1D and 2D Cartesian simulations of railgun (parallel plate) jet accelerators using He and Ar gases. The inclusion of EOS and radiation physics reduces the electron temperature, resulting in higher calculated jet Mach numbers in the simulations. We also introduce a surface physics model for jet accelerators in which a frictional drag along the walls leads to axial spreading of the emerging jet. The simulations demonstrate that high Mach number jets can be produced by railgun accelerators for a variety of applications, including high energy density physics experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Novel electromagnetic radiation in a semi-infinite space filled with a double-negative metamaterial

We have theoretically investigated the electromagnetic radiation excited by a charged particle moving along a semi-infinite space filled with a double-negative metamaterial (DNM). Cherenkov radiation in the double-negative region exhibits reversed or backward radiation behavior. The spectral density of reversed Cherenkov radiation has a continuous distribution over the radiation frequency region. The influence of some important parameters on the Cherenkov radiation energy per unit length has been discussed. The surface wave in the vacuum region presented here also is investigated. We conclude that the amplitude of the surface wave is greatly enhanced over some normal dielectric material cases. The enhanced surface wave may be useful for high frequency and high power vacuum electron devices with the DNM.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Electromagnetic polarizabilities: Lattice QCD in background fields

Chiral perturbation theory makes definitive predictions for the extrinsic behavior of hadrons in external electric and magnetic fields. Near the chiral limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons are determined in terms of a few well-known parameters. In this limit, hadrons become quantum mechanically diffuse as polarizabilities scale with the inverse square-root of the quark mass. In some cases, however, such predictions from chiral perturbation theory have not compared well with experimental data. Ultimately we must turn to first principles numerical simulations of QCD to determine properties of hadrons, and confront the predictions of chiral perturbation theory. To address the electromagnetic polarizabilities, we utilize the background field technique. Restricting our attention to calculations in background electric fields, we demonstrate new techniques to determine electric polarizabilities and baryon magnetic moments for both charged and neutral states. As we can study the quark mass dependence of observables with lattice QCD, the lattice will provide a crucial test of our understanding of low-energy QCD, which will be timely in light of ongoing experiments, such as at COMPASS and HI gamma S.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Plasma parameters and electromagnetic forces induced by the magneto hydro dynamic interaction in a hypersonic argon flow experiment

This work proposes an experimental analysis on the magneto hydro dynamic (MHD) interaction induced by a magnetic test body immersed into a hypersonic argon flow. The characteristic plasma parameters are measured. They are related to the voltages arising in the Hall direction and to the variation of the fluid dynamic properties induced by the interaction. The tests have been performed in a hypersonic wind tunnel at Mach 6 and Mach 15. The plasma parameters are measured in the stagnation region in front of the nozzle of the wind tunnel and in the free stream region at the nozzle exit. The test body has a conical shape with the cone axis in the gas flow direction and the cone vertex against the flow. It is placed at the nozzle exit and is equipped with three permanent magnets. In the configuration adopted, the Faraday current flows in a closed loop completely immersed into the plasma of the shock layer. The electric field and the pressure variation due to MHD interaction have been measured on the test body walls. Microwave adsorption measurements have been used for the determination of the electron number density and the electron collision frequency. Continuum recombination radiation and line radiation emissions have been detected. The electron temperature has been determined by means of the spectroscopic data by using different methods. The electron number density has been also determined by means of the Stark broadening of H{sub {alpha}} and the H{sub {beta}} lines. Optical imaging has been utilized to visualize the pattern of the electric current distribution in the shock layer around the test body. The experiments show a considerable effect of the electromagnetic forces produced by the MHD interaction acting on the plasma flow around the test body. A comparison of the experimental data with simulation results shows a good agreement.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Influence of electromagnetic radiation on the power balance in a radiofrequency microdischarge with a hollow needle electrode

This study is focused on the power deposition in microplasma jet discharges generated by application of radiofrequency (RF) excitation to a hollow needle electrode. The plasma jet is initiated at atmospheric pressure in open air with a flow of helium through the electrode. We show that in this configuration, a significant part of the injected power is dissipated in electromagnetic radiation. Many recent works have demonstrated the potential of either cold plasma jets or of RF radiation for applications in medicine, and therefore a source that produces both a cold plasma jet and RF radiation could be of interest.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗