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Sample records for direct plasma beam

  1. Direct plasma injection scheme with various ion beams

    SciTech Connect

    Okamura, M.

    2010-09-15

    The laser ion source is one of the most powerful heavy ion sources. However, it is difficult to obtain good stability and to control its intense current. To overcome these difficulties, we proposed a new beam injection scheme called 'direct plasma injection scheme'. Following this it was established to provide various species with desired charge state as an intense accelerated beam. Carbon, aluminum and iron beams have been tested.

  2. Direct measurements of plasma characteristics in space-simulation beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.

    1982-01-01

    Recent laboratory investigations of space-simulated electron-beam-plasma interactions are discussed. The plasma has been characterized with respect to its spatial distributions in density, temperature, and density fluctuation power spectra. The latter results have been further classified in terms of amplitude and spectral distributions. The overall results include: (1) detailed radial profiles of plasma density as a function of beam parameters; (2) the association of low-frequency large amplitude fluctuations with ion acoustic, ion cyclotron, and drift-wave modes; (3) the identification and spatial mapping of suprathermal electrons in the beam core; and (4) the experimental definition of a density-dependent criterion for the ignition of the beam-plasma-discharge.

  3. Simulation of direct plasma injection for laser ion beam acceleration with a radio frequency quadrupole

    SciTech Connect

    Jin, Q. Y.; Li, Zh. M.; Liu, W.; Zhao, H. Y. Zhang, J. J.; Sha, Sh.; Zhang, Zh. L.; Zhang, X. Zh.; Sun, L. T.; Zhao, H. W.

    2014-07-15

    The direct plasma injection scheme (DPIS) has been being studied at Institute of Modern Physics since several years ago. A C{sup 6+} beam with peak current of 13 mA, energy of 593 keV/u has been successfully achieved after acceleration with DPIS method. To understand the process of DPIS, some simulations have been done as follows. First, with the total current intensity and the relative yields of different charge states for carbon ions measured at the different distance from the target, the absolute current intensities and time-dependences for different charge states are scaled to the exit of the laser ion source in the DPIS. Then with these derived values as the input parameters, the extraction of carbon beam from the laser ion source to the radio frequency quadrupole with DPIS is simulated, which is well agreed with the experiment results.

  4. Simulation of direct plasma injection for laser ion beam acceleration with a radio frequency quadrupole.

    PubMed

    Jin, Q Y; Zhao, H Y; Zhang, J J; Sha, Sh; Zhang, Zh L; Li, Zh M; Liu, W; Zhang, X Zh; Sun, L T; Zhao, H W

    2014-07-01

    The direct plasma injection scheme (DPIS) has been being studied at Institute of Modern Physics since several years ago. A C(6+) beam with peak current of 13 mA, energy of 593 keV/u has been successfully achieved after acceleration with DPIS method. To understand the process of DPIS, some simulations have been done as follows. First, with the total current intensity and the relative yields of different charge states for carbon ions measured at the different distance from the target, the absolute current intensities and time-dependences for different charge states are scaled to the exit of the laser ion source in the DPIS. Then with these derived values as the input parameters, the extraction of carbon beam from the laser ion source to the radio frequency quadrupole with DPIS is simulated, which is well agreed with the experiment results.

  5. Plasma Beam Measurements

    DTIC Science & Technology

    1991-08-01

    GUN PLASMA BEAM / ,I 21 cm diameter = 0 GLASS DRIFT TUBE 50 cm diameter MCP CAMERA CLASS CROSSES (a) Gun muzzle /"- PLASA BEAM / TAROT z = 10 m MCP...discusses some of the hydrodynamic issues related to the calcula- tions. The reader may well wonder why hydrodynamics should be an issue in a 116 WL-TR-90...answer is yes for the slow beam cases and no for the fast beam cases. This is explained further. 118 WL-TR-90-83 The reader will recall the

  6. Enhanced laser beam coupling to a plasma

    DOEpatents

    Steiger, Arno D.; Woods, Cornelius H.

    1976-01-01

    Density perturbations are induced in a heated plasma by means of a pair of oppositely directed, polarized laser beams of the same frequency. The wavelength of the density perturbations is equal to one half the wavelength of the laser beams. A third laser beam is linearly polarized and directed at the perturbed plasma along a line that is perpendicular to the direction of the two opposed beams. The electric field of the third beam is oriented to lie in the plane containing the three beams. The frequency of the third beam is chosen to cause it to interact resonantly with the plasma density perturbations, thereby efficiently coupling the energy of the third beam to the plasma.

  7. Direct growth of hexagonal boron nitride/graphene heterostructures on cobalt foil substrates by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xu, Zhongguang; Khanaki, Alireza; Tian, Hao; Zheng, Renjing; Suja, Mohammad; Zheng, Jian-Guo; Liu, Jianlin

    2016-07-01

    Graphene/hexagonal boron nitride (G/h-BN) heterostructures have attracted a great deal of attention because of their exceptional properties and wide variety of potential applications in nanoelectronics. However, direct growth of large-area, high-quality, and stacked structures in a controllable and scalable way remains challenging. In this work, we demonstrate the synthesis of h-BN/graphene (h-BN/G) heterostructures on cobalt (Co) foil by sequential deposition of graphene and h-BN layers using plasma-assisted molecular beam epitaxy. It is found that the coverage of h-BN layers can be readily controlled on the epitaxial graphene by growth time. Large-area, uniform-quality, and multi-layer h-BN films on thin graphite layers were achieved. Based on an h-BN (5-6 nm)/G (26-27 nm) heterostructure, capacitor devices with Co(foil)/G/h-BN/Co(contact) configuration were fabricated to evaluate the dielectric properties of h-BN. The measured breakdown electric field showed a high value of ˜2.5-3.2 MV/cm. Both I-V and C-V characteristics indicate that the epitaxial h-BN film has good insulating characteristics.

  8. Direct growth of graphene on in situ epitaxial hexagonal boron nitride flakes by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zuo, Zheng; Liu, Jianlin

    2015-11-23

    Hexagonal boron nitride (h-BN) single-crystal domains were grown on cobalt (Co) substrates at a substrate temperature of 850–900 °C using plasma-assisted molecular beam epitaxy. Three-point star shape h-BN domains were observed by scanning electron microscopy, and confirmed by Raman and X-ray photoelectron spectroscopy. The h-BN on Co template was used for in situ growth of multilayer graphene, leading to an h-BN/graphene heterostructure. Carbon atoms preferentially nucleate on Co substrate and edges of h-BN and then grow laterally to form continuous graphene. Further introduction of carbon atoms results in layer-by-layer growth of graphene on graphene and lateral growth of graphene on h-BN until it may cover entire h-BN flakes.

  9. Theory of beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Papadopoulos, K.

    1982-01-01

    The general theory of beam plasma discharge (BPD) is discussed in relation to space and laboratory beam injection situations. An important concept introduced is that even when beam plasma instabilities are excited, there are two regime of BPD with radically different observational properties. They are described here as BPD with either classical or anomalous energy depositions. For high pressures or low altitudes, the classical is expected to dominate. For high altitudes and laboratory experiments, where the axial system size is less than lambda sub en, no BPD will be triggered unless the unstable waves are near the ambient plasma frequency and their amplitudes at saturation are large enough to create suprathermal tails by collapsing.

  10. Regimes of enhanced electromagnetic emission in beam-plasma interactions

    SciTech Connect

    Timofeev, I. V.; Annenkov, V. V.; Arzhannikov, A. V.

    2015-11-15

    The ways to improve the efficiency of electromagnetic waves generation in laboratory experiments with high-current relativistic electron beams injected into a magnetized plasma are discussed. It is known that such a beam can lose, in a plasma, a significant part of its energy by exciting a high level of turbulence and heating plasma electrons. Beam-excited plasma oscillations may simultaneously participate in nonlinear processes resulting in a fundamental and second harmonic emissions. It is obvious, however, that in the developed plasma turbulence the role of these emissions in the total energy balance is always negligible. In this paper, we investigate whether electromagnetic radiation generated in the beam-plasma system can be sufficiently enhanced by the direct linear conversion of resonant beam-driven modes into electromagnetic ones on preformed regular inhomogeneities of plasma density. Due to the high power of relativistic electron beams, the mechanism discussed may become the basis for the generator of powerful sub-terahertz radiation.

  11. Regimes of enhanced electromagnetic emission in beam-plasma interactions

    NASA Astrophysics Data System (ADS)

    Timofeev, I. V.; Annenkov, V. V.; Arzhannikov, A. V.

    2015-11-01

    The ways to improve the efficiency of electromagnetic waves generation in laboratory experiments with high-current relativistic electron beams injected into a magnetized plasma are discussed. It is known that such a beam can lose, in a plasma, a significant part of its energy by exciting a high level of turbulence and heating plasma electrons. Beam-excited plasma oscillations may simultaneously participate in nonlinear processes resulting in a fundamental and second harmonic emissions. It is obvious, however, that in the developed plasma turbulence the role of these emissions in the total energy balance is always negligible. In this paper, we investigate whether electromagnetic radiation generated in the beam-plasma system can be sufficiently enhanced by the direct linear conversion of resonant beam-driven modes into electromagnetic ones on preformed regular inhomogeneities of plasma density. Due to the high power of relativistic electron beams, the mechanism discussed may become the basis for the generator of powerful sub-terahertz radiation.

  12. Beam Plasma Turbulence Study.

    DTIC Science & Technology

    1983-05-01

    Ney, and J . F. Karczewski, Spae Sci. Instrum ., 4, 143 (1978). -- ’.. ...... .. " ’- -’ ... -,,, ,i, ,, - . --. : s v.-’ Z XW , - .. . Ř ’ - ’ " p...interactions with the able plasma theorists, Dr. J . R. Jasperse at the Air Force Geophysics Laboratory, Drs. B. Basu and J . Retterer of the Space Data Analysis...Drs. J . D. Winningham and J . Burch at the Southwest Research Institute, Dr. D. Klumpar of the University of Texas at Dallas, Dr. P. Kintner of the

  13. Direct comparison of the performance of commonly used e-beam resists during nano-scale plasma etching of Si, SiO2, and Cr

    NASA Astrophysics Data System (ADS)

    Goodyear, Andy; Boettcher, Monika; Stolberg, Ines; Cooke, Mike

    2015-03-01

    Electron beam writing remains one of the reference pattern generation techniques, and plasma etching continues to underpin pattern transfer. We report a systematic study of the plasma etch resistance of several e-beam resists, both negative and positive as well as classical and Chemically Amplified Resists: HSQ[1,2] (Dow Corning), PMMA[3] (Allresist GmbH), AR-P6200 (Allresist GmbH), ZEP520 (Zeon Corporation), CAN028 (TOK), CAP164 (TOK), and an additional pCAR (non-disclosed provider). Their behaviour under plasma exposure to various nano-scale plasma etch chemistries was examined (SF6/C4F8 ICP silicon etch, CHF3/Ar RIE SiO2 etch, Cl2/O2 RIE and ICP chrome etch, and HBr ICP silicon etch). Samples of each resist type were etched simultaneously to provide a direct comparison of their etch resistance. Resist thicknesses (and hence resist erosion rates) were measured by spectroscopic ellipsometer in order to provide the highest accuracy for the resist comparison. Etch selectivities (substrate:mask etch rate ratio) are given, with recommendations for the optimum resist choice for each type of etch chemistry. Silicon etch profiles are also presented, along with the exposure and etch conditions to obtain the most vertical nano-scale pattern transfer. We identify one resist that gave an unusually high selectivity for chlorinated and brominated etches which could enable pattern transfer below 10nm without an additional hard mask. In this case the resist itself acts as a hard mask. We also highlight the differing effects of fluorine and bromine-based Silicon etch chemistries on resist profile evolution and hence etch fidelity.

  14. Plasma lenses for focusing relativistic electron beams

    SciTech Connect

    Govil, R.; Wheeler, S.; Leemans, W.

    1997-04-01

    The next generation of colliders require tightly focused beams with high luminosity. To focus charged particle beams for such applications, a plasma focusing scheme has been proposed. Plasma lenses can be overdense (plasma density, n{sub p} much greater than electron beam density, n{sub b}) or underdense (n{sub p} less than 2 n{sub b}). In overdense lenses the space-charge force of the electron beam is canceled by the plasma and the remaining magnetic force causes the electron beam to self-pinch. The focusing gradient is nonlinear, resulting in spherical aberrations. In underdense lenses, the self-forces of the electron beam cancel, allowing the plasma ions to focus the beam. Although for a given beam density, a uniform underdense lens produces smaller focusing gradients than an overdense lens, it produces better beam quality since the focusing is done by plasma ions. The underdense lens can be improved by tapering the density of the plasma for optimal focusing. The underdense lens performance can be enhanced further by producing adiabatic plasma lenses to avoid the Oide limit on spot size due to synchrotron radiation by the electron beam. The plasma lens experiment at the Beam Test Facility (BTF) is designed to study the properties of plasma lenses in both overdense and underdense regimes. In particular, important issues such as electron beam matching, time response of the lens, lens aberrations and shot-to-shot reproducibility are being investigated.

  15. Optical Mixing in the Strong Coupling Regime: A New Method of Beam Conditioning at Hohlraum LEH and Direct Drive ICF Coronal Plasmas

    NASA Astrophysics Data System (ADS)

    Mardirian, Marine; Afeyan, Bedros; Huller, Stefan; Montgomery, David; Froula, Dustin; Kirkwood, Robert

    2012-10-01

    We will present theoretical and computational results on Brillouin interactions between two beams in co-, counter-, and orthogonal propagation geometries. The beams will be structured (with speckle patterns), the plasma will have inhomogeneous flow including the Mach -1 surface. As the growth rate of the instability surpasses the natural frequency of the ion wave, the strong coupling regime (SCR) is reached, where reactive quasi-modes with intensity dependent frequency shifts result. This is especially true in laser hot spots. We trace the consequences of operations in this regime with different damping rates on the ion acoustic waves. We consider convective and absolute instabilities as well as the design of experiments which could examine these new regimes of instability behavior with new 10 psec time resolved diagnostics. Whether well enough conditioned beams can result after 10's or 100's of pairwise crossings in direct and indirect drive ICF configurations, and whether SRS can thus be strongly suppressed downstream, remains to be demonstrated. But the prospects exist for such new paths to instability control in a staged manner before STUD pulses are implemented.-

  16. Plasma/Neutral-Beam Etching Apparatus

    NASA Technical Reports Server (NTRS)

    Langer, William; Cohen, Samuel; Cuthbertson, John; Manos, Dennis; Motley, Robert

    1989-01-01

    Energies of neutral particles controllable. Apparatus developed to produce intense beams of reactant atoms for simulating low-Earth-orbit oxygen erosion, for studying beam-gas collisions, and for etching semiconductor substrates. Neutral beam formed by neutralization and reflection of accelerated plasma on metal plate. Plasma ejected from coaxial plasma gun toward neutralizing plate, where turned into beam of atoms or molecules and aimed at substrate to be etched.

  17. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, M. C.; Muggli, Patric; Yakimenko, Vitaly; Babzien, Marcus; Kusche, Karl; Fedurin, Mikhail

    2010-11-01

    Beam-driven plasma wakefield accelerators (PWFA), such as the ``plasma afterburner,'' are a promising approach for significantly increasing the particle energies of conventional accelerators. The study and optimization of PWFA would benefit from an experimental correlation between the parameters of the drive bunch, the accelerated bunch and the corresponding, accelerating plasma wave structure. However, the plasma wave structure has not yet been observed directly in PWFA. We will report our current work on noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) visualization of beam-driven plasma waves. Both techniques employ two laser pulses (probe and reference) co-propagating with the particle drive-beam and its plasma wake. The reference pulse precedes the drive bunch, while the probe overlaps the plasma wave and maps its longitudinal and transverse structure. The experiment is being developed at the BNL/ATF Linac to visualize wakes generated by two and multi-bunch drive beams.

  18. Beam-plasma instabilities and the beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Kellogg, P. J.; Boswell, R. W.

    1986-01-01

    Using a new waves on magnetized beams and turbulence (WOMBAT) 0-450 eV electron gun, measurements bearing on the generation of beam-plasma discharge (BPD) are made. The new gun has a narrower divergence angle than the old, and the BPD ignition current is found to be proportional to the cross-sectional area of the plasma. The high-frequency instabilities are identified with the two Trivelpiece-Gould modes, (1959). The upper frequency is identified as a Cerenkov resonance with the upper Trivelpiece-Gould mode, and the lower frequency with a cyclotron resonance with the lower mode, in agreement with theoretical expectations. Convective growth rates are found to be small. A mechanism involving the conversion of a convective instability to an absolute one by trapping of the unstable waves in the density perturbations of the low-frequency waves, is suggested for the low-frequency wave control of the onset of the high frequency precursors to the BPD.

  19. Electron Beam Diagnostics in Plasmas Based on Electron Beam Ionization

    NASA Astrophysics Data System (ADS)

    Leonhardt, Darrin; Leal-Quiros, Edbertho; Blackwell, David; Walton, Scott; Murphy, Donald; Fernsler, Richard; Meger, Robert

    2001-10-01

    Over the last few years, electron beam ionization has been shown to be a viable generator of high density plasmas with numerous applications in materials modification. To better understand these plasmas, we have fielded electron beam diagnostics to more clearly understand the propagation of the beam as it travels through the background gas and creates the plasma. These diagnostics vary greatly in sophistication, ranging from differentially pumped systems with energy selective elements to metal 'hockey pucks' covered with thin layers of insulation to electrically isolate the detector from the plasma but pass high energy beam electrons. Most importantly, absolute measurements of spatially resolved beam current densities are measured in a variety of pulsed and continuous beam sources. The energy distribution of the beam current(s) will be further discussed, through experiments incorporating various energy resolving elements such as simple grids and more sophisticated cylindrical lens geometries. The results are compared with other experiments of high energy electron beams through gases and appropriate disparities and caveats will be discussed. Finally, plasma parameters are correlated to the measured beam parameters for a more global picture of electron beam produced plasmas.

  20. Electron energy distribution produced by beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Anderson, H. R.; Gordeuk, J.; Jost, R. J.

    1982-01-01

    In an investigation of a beam-plasma discharge (BPD), the electron energy distribution of an electron beam moving through a partially ionized gas is analyzed. Among other results, it is found that the occurrence of BPD heats the initially cold electron beam from the accelerator. The directional intensity of electrons measured outside the beam core indicates that most particles suffer a single scattering in energy and pitch angle. At low currents this result is expected as beam particles collide with the neutral atmosphere, while in BPD the majority of particles is determined to still undergo a single scattering near the original beam core. The extended energy spectra at various beam currents show two rather distinct plasma populations, one centered at the initial beam energy (approximately 1500 eV) and the other at approximately 150 eV.

  1. Electromagnetic radiation from beam-plasma instabilities

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Whelan, D. A.

    1982-01-01

    The mechanism by which unstable electrostatic waves of an electron-beam plasma system are converted into observed electromagnetic waves is of great current interest in space plasma physics. Electromagnetic radiation arises from both natural beam-plasma systems, e.g., type III solar bursts and kilometric radiation, and from man-made electron beams injected from rockets and spacecraft. In the present investigation the diagnostic difficulties encountered in space plasmas are overcome by using a large laboratory plasma. A finite diameter (d approximately equal to 0.8 cm) electron beam is injected into a uniform quiescent magnetized afterglow plasma of dimensions large compared with electromagnetic wavelength. Electrostatic waves grow, saturate and decay within the uniform central region of the plasma volume so that linear mode conversion on density gradients can be excluded as a possible generation mechanism for electromagnetic waves.

  2. Plasma formed ion beam projection lithography system

    DOEpatents

    Leung, Ka-Ngo; Lee, Yung-Hee Yvette; Ngo, Vinh; Zahir, Nastaran

    2002-01-01

    A plasma-formed ion-beam projection lithography (IPL) system eliminates the acceleration stage between the ion source and stencil mask of a conventional IPL system. Instead a much thicker mask is used as a beam forming or extraction electrode, positioned next to the plasma in the ion source. Thus the entire beam forming electrode or mask is illuminated uniformly with the source plasma. The extracted beam passes through an acceleration and reduction stage onto the resist coated wafer. Low energy ions, about 30 eV, pass through the mask, minimizing heating, scattering, and sputtering.

  3. Theoretical and Experimental Beam Plasma Physics (TEBPP)

    NASA Technical Reports Server (NTRS)

    Roberts, B.

    1986-01-01

    The theoretical and experimental beam plasma physics (TEBPP) consists of a package of five instruments to measure electric and magnetic fields, plasma density and temperature, neutral density, photometric emissions, and energetic particle spectra during firings of the particle injector (SEPAC) electron beam. The package is developed on a maneuverable boom (or RMS) and is used to measure beam characteristics and induced perturbations field ( 10 m) and mid field ( 10 m to 100 m) along the electron beam. The TEBPP package will be designed to investigate induced oscillations and induced electromagnetic mode waves, neutral and ion density and temperature effects, and beam characteristics as a function of axial distance.

  4. Theoretical and Experimental Beam Plasma Physics (TEBPP)

    NASA Technical Reports Server (NTRS)

    Roberts, W. T.

    1985-01-01

    The theoretical and experimental beam plasma physics (TEBPP) consists of a package of five instruments to measure electric and magnetic fields, plasma density and temperature, neutral density, photometric emissions, and energetic particle spectra during firings of the particle injector (SEPAC) electron beam. The package is deployed on a maneuverable boom (or RMS) and is used to measure beam characteristics and induced perturbations in the near field ( 10 m) and mid field (10 m to 100 m) along the electron beam. The TEBPP package will be designed to investigate induced oscillations and induced electromagnetic mode waves, neutral and ion density and temperature effects, and beam characteristics as a function of axial distance.

  5. Speckle Statistics of Multiple Overlapping Beams Propagating in Inhomogeneous Plasmas

    NASA Astrophysics Data System (ADS)

    Afeyan, Bedros B.; Schmitt, A. J.; Lehmberg, R. H.

    1999-11-01

    We have calculated the electric field of RPP, SSD and ISI beams propagating in inhomogeneous plasmas. We have studied the intensity statistics of these beams as well as those generated when a number of such beams overlap. Changes in the geometry and statistical properties of the resulting hot spots will be presented as a function of angles of incidence, spot sizes and density scale length. Analytic, semi-analytic (quadrature using Green's functions) and numerical simulation results will be shown. The degree to which vacuum electrodynamics is inappropriate to model multiple overlapping beams in inhomogeneous plasmas will be demonstrated. These results are crucial to the study of plasma phenomena in the coronas of direct drive targets including laser imprinting and parametric instabilities. Parametric instabilities at the LEH of indirect drive targets must also take into account overlapping beam physics issues discussed here.

  6. Aerosol beam-focus laser-induced plasma spectrometer device

    DOEpatents

    Cheng, Meng-Dawn

    2002-01-01

    An apparatus for detecting elements in an aerosol includes an aerosol beam focuser for concentrating aerosol into an aerosol beam; a laser for directing a laser beam into the aerosol beam to form a plasma; a detection device that detects a wavelength of a light emission caused by the formation of the plasma. The detection device can be a spectrometer having at least one grating and a gated intensified charge-coupled device. The apparatus may also include a processor that correlates the wavelength of the light emission caused by the formation of the plasma with an identity of an element that corresponds to the wavelength. Furthermore, the apparatus can also include an aerosol generator for forming an aerosol beam from bulk materials. A method for detecting elements in an aerosol is also disclosed.

  7. Simulation of beam-induced plasma for the mitigation of beam-beam effects

    SciTech Connect

    Ma, J.; Wang, G.; Samulyak, R.; Yu, K.; Litvinenko, V.

    2015-05-03

    One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.

  8. Electromagnetic radiation from beam-plasma instabilities

    NASA Technical Reports Server (NTRS)

    Pritchett, P. L.; Dawson, J. M.

    1983-01-01

    A computer simulation is developed for the generation of electromagnetic radiation in an electron beam-plasma interaction. The plasma is treated as a two-dimensional finite system, and effects of a continuous nonrelativistic beam input are accounted for. Three momentum and three field components are included in the simulation, and an external magnetic field is excluded. EM radiation generation is possible through interaction among Langmuir oscillations, ion-acoustic waves, and the electromagnetic wave, producing radiation perpendicular to the beam. The radiation is located near the plasma frequency, and polarized with the E component parallel to the beam. The scattering of Langmuir waves caused by ion-acoustic fluctuations generates the radiation. Comparison with laboratory data for the three-wave interactions shows good agreement in terms of the radiation levels produced, which are small relative to the plasma thermal energy.

  9. Terahertz twisted beams generation in plasma

    NASA Astrophysics Data System (ADS)

    Sobhani, Hassan; Vaziri (Khamedi), Mohammad; Rooholamininejad, Hossien; Bahrampour, Alireza

    2016-08-01

    The resonant vortex terahertz beam generation by the cross-focusing of two twisted coaxial laser beams is investigated. For the resonant excitation of terahertz radiation, the rippled density in plasma and the ripple wave number is suitably chosen to satisfy the phase matching condition. The nonlinear current density at terahertz frequency arises due to the spatial variation of two Laguerre-Gaussian coupled field. The terahertz intensity scales as the ponderomotive force of laser beams which imparts an oscillatory velocity to the electrons and, in fact, input Laguerre-Gaussian laser beams properties such as vortex charge number and beam waist. Various laser and plasma parameters are employed to yield vortex terahertz radiation with higher efficiency. Also, it is shown that when the beating frequency approaches plasma frequency, the amplitude of THz radiation increases.

  10. Low energy, high power hydrogen neutral beam for plasma heating

    SciTech Connect

    Deichuli, P.; Davydenko, V.; Ivanov, A. Mishagin, V.; Sorokin, A.; Stupishin, N.; Korepanov, S.; Smirnov, A.

    2015-11-15

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction.

  11. Fast ion beam-plasma interaction system.

    PubMed

    Breun, R A; Ferron, J R

    1979-07-01

    A device has been constructed for the study of the interaction between a fast ion beam and a target plasma of separately controllable parameters. The beam of either hydrogen or helium ions has an energy of 1-4 keV and a total current of 0.5-2 A. The beam energy and beam current can be varied separately. The ion source plasma is created by a pulsed (0.2-10-ms pulse length) discharge in neutral gas at up to 3 x 10(-3) Torr. The neutrals are pulsed into the source chamber, allowing the neutral pressure in the target region to remain less than 5 x 10(-5) Torr at a 2-Hz repetition rate. The creation of the source plasma can be described by a simple set of equations which predict optimum source design parameters. The target plasma is also produced by a pulsed discharge. Between the target and source chambers the beam is neutralized by electrons drawn from a set of hot filaments. Currently under study is an unstable wave in a field-free plasma excited when the beam velocity is nearly equal to the target electron thermal velocity (v(beam) approximately 3.5 x 10(7) cm/s, Te = 0.5 eV).

  12. Plasma-beam traps and radiofrequency quadrupole beam coolers.

    PubMed

    Maggiore, M; Cavenago, M; Comunian, M; Chirulotto, F; Galatà, A; De Lazzari, M; Porcellato, A M; Roncolato, C; Stark, S; Caruso, A; Longhitano, A; Cavaliere, F; Maero, G; Paroli, B; Pozzoli, R; Romé, M

    2014-02-01

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

  13. Plasma-beam traps and radiofrequency quadrupole beam coolers

    SciTech Connect

    Maggiore, M. Cavenago, M.; Comunian, M.; Chirulotto, F.; Galatà, A.; De Lazzari, M.; Porcellato, A. M.; Roncolato, C.; Stark, S.; Caruso, A.; Longhitano, A.; Cavaliere, F.; Maero, G.; Paroli, B.; Pozzoli, R.; Romé, M.

    2014-02-15

    Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

  14. Scaling of the beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Rowland, H. L.; Papadopoulos, K.; Chang, C. L.

    1981-01-01

    A theoretical analysis is presented of the scaling of the critical beam current required for ignition and the narrow band emissions observed for beam currents less than critical in a beam plasma discharge experiment. The theory of the two-stream interaction between a nonrelativistic cold electron beam and a plasma in the presence of a magnetic field is developed, and conditions for the two-stream instability and the resulting amplification are derived. It is shown that the experimentally observed scaling is consistent with the assumption that the ignition triggering occurs when an instability near the electron plasma frequency is excited. Finally, it is shown that the wave emissions observed in the subthreshold range can be explained by the excitation of the kinetic instability of the upper branch and convective saturation.

  15. Ion beams from laser-generated plasmas

    NASA Technical Reports Server (NTRS)

    Hughes, R. H.; Anderson, R. J.; Gray, L. G.; Rosenfeld, J. P.; Manka, C. K.; Carruth, M. R.

    1980-01-01

    The paper describes the space-charge-limited beams produced by the plasma blowoffs generated by 20-MW bursts of 1.06-micron radiation from an active Q-switched Nd:YAG laser. Laser power densities near 10 to the 11th/sq cm on solid targets generate thermalized plasma plumes which drift to a 15-kV gridded extraction gap where the ions are extracted, accelerated, and electrostatically focused; the spatially defined ion beams are then magnetically analyzed to determine the charge state content in the beams formed from carbon, aluminum, copper, and lead targets. This technique preserves time-of-flight (TOF) information in the plasma drift region, which permits plasma ion temperatures and mass flow velocities to be determined from the Maxwellian ion curve TOF shapes for the individual charge species.

  16. Challenges in plasma and laser wakefield accelerated beams diagnostic

    NASA Astrophysics Data System (ADS)

    Cianchi, A.; Anania, M. P.; Bellaveglia, M.; Castellano, M.; Chiadroni, E.; Ferrario, M.; Gatti, G.; Marchetti, B.; Mostacci, A.; Pompili, R.; Ronsivalle, C.; Rossi, A. R.; Serafini, L.

    2013-08-01

    The new frontier in the particle beam accelerator is the so called plasma acceleration. Using the strong electric field inside a plasma it is possible to achieve accelerating gradients in the order of magnitude larger with respect to the actual technologies. Different schemes have been proposed and several already tested, producing beams of energy of several GeV. Mainly two approaches are followed: either the beam is directly produced by the interaction of a TW/PW class laser with a gas jet or a preexisting particle beam is accelerated in a plasma channel. In both cases a precise determination of the emerging beam parameters is mandatory for the fine tuning of the devices. The measurement of these parameters, in particular the emittance, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We show the problems related to the diagnostic of this kind of beams and the proposed or already realized solutions.

  17. Ions beams and ferroelectric plasma sources

    NASA Astrophysics Data System (ADS)

    Stepanov, Anton

    Near-perfect space-charge neutralization is required for the transverse compression of high perveance ion beams for ion-beam-driven warm dense matter experiments, such as the Neutralized Drift Compression eXperiment (NDCX). Neutralization can be accomplished by introducing a plasma in the beam path, which provides free electrons that compensate the positive space charge of the ion beam. In this thesis, charge neutralization of a 40 keV, perveance-dominated Ar+ beam by a Ferroelectric Plasma Source (FEPS) is investigated. First, the parameters of the ion beam, such as divergence due to the extraction optics, charge neutralization fraction, and emittance were measured. The ion beam was propagated through the FEPS plasma, and the effects of charge neutralization were inferred from time-resolved measurements of the transverse beam profile. In addition, the dependence of FEPS plasma parameters on the configuration of the driving pulser circuit was studied to optimize pulser design. An ion accelerator was constructed that produced a 30-50 keV Ar + beam with pulse duration <300 mus and dimensionless perveance Q up to 8 x 10-4. Transverse profile measurements 33 cm downstream of the ion source showed that the dependence of beam radius on Q was consistent with space charge expansion. It was concluded that the beam was perveance-dominated with a charge neutralization fraction of approximately zero in the absence of neutralizing plasma. Since beam expansion occurred primarily due to space charge, the decrease in effective perveance due to neutralization by FEPS plasma can be inferred from the reduction in beam radius. Results on propagation of the ion beam through FEPS plasma demonstrate that after the FEPS is triggered, the beam radius decreases to its neutralized value in about 5 mus. The duration of neutralization was about 10 mus at a charging voltage VFEPS = 5.5 kV and 35 mus at VFEPS = 6.5 kV. With VFEPS = 6.5 kV, the transverse current density profile 33 cm downstream

  18. Whittaker functions in beam driven plasma wakefield acceleration for a plasma with a parabolic density profile

    SciTech Connect

    Golian, Y.; Dorranian, D.; Aslaninejad, M.

    2016-01-15

    A model for the interaction of charged particle beams and plasma for a linear wakefield generation in a parabolic plasma channel is presented. The density profile has the maximum on the axis. A Gaussian proton beam is employed to excite the plasma wakefield in the channel. We have built a thorough analytical model and solved the governing equations for the wakefield acceleration of a charged particle beam. The longitudinal and radial wakefields are expressed by Whittaker functions, and for certain parameters of plasma and the beam, their behaviours in longitudinal and radial directions are investigated. It is observed that the radial electric field generated by the bunch increases with the distance behind the bunch.

  19. Direct fabrication of nanoscale bio-adhesive patterns by electron beam surface modification of plasma polymerized poly ethylene oxide-like coatings

    NASA Astrophysics Data System (ADS)

    Brétagnol, Frédéric; Sirghi, Lucel; Mornet, Stéphane; Sasaki, Takao; Gilliland, Douglas; Colpo, Pascal; Rossi, Francois

    2008-03-01

    In this study we present a method to produce nanostructured surfaces containing bio-adhesive features inside a non bio-adhesive matrix. The strategy is based on the combination of low pressure plasma polymerization and electron beam lithography processes and allows the fabrication of the structured materials in just two steps without using any solvents. In a first step, a thin protein-and-cell-repelling coating (~10 nm) is obtained by plasma polymerization of Di-glyme. Then, in a second step, the bio-adhesive properties of the layer are tuned by monitoring the concentration of ether bonds of the film by irradiating it locally by different irradiation doses with an electron beam. Time-of-flight secondary ion mass spectroscopy and atomic force microscopy analysis have been used to characterize the produced surfaces. Experiments with a model protein (bovine serum albumin) on the patterned surfaces show preferential adhesion to the irradiated regions, indicating the potential of this simple technique for the development of highly compacted sensitive bio-sensing devices.

  20. Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction

    NASA Astrophysics Data System (ADS)

    Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.

    2016-03-01

    In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.

  1. A Hybrid Mode and a Classification of Beam Plasma Instabilities

    DTIC Science & Technology

    2014-09-26

    is warranted include: electron beam heating of a dense plasma for inertial confinement fusion driver; laser-plasma beat wave acceleration of particles...beam are assumed collisionless. The plasma is at rest, and both the plasma and the beam are cold . It is assumed that there is no plasma return current...relativistic mass factor and c is the speed of light. The beam is cold and is embedded in a uniform background of ions of considerably lower density. The

  2. Plasma diagnostic techniques using particle beam probes

    SciTech Connect

    Jennings, W C

    1980-07-01

    A brief overview is given of particle beam probing. The fundamental concepts common to all techniques are discussed as well as the design considerations for choosing a particular diagnostic technique. The capabilities of existing and proposed techniques, and the present status of the techniques in major magnetic confinement geometries is also presented. Techniques which involve the injection of a beam of neutral particles into the plasma are then considered. The techniques of beam attenuation, beam scattering, and active charge exchange using a beam of light particles such as hydrogen or helium are first presented. Optical measurements of the Zeeman splitting of the radiation from a neutral lithium beam is then discussed, including a new proposal for significantly improving this technique through the addition of a dye laser. Two techniques involving the injection of heavy neutral particles are then presented, and the section concludes with two proposed techniques for measuring the properties of the alpha particles produced from actual fusion reactions. The diagnostic techniques which are based upon the injection of a beam of charged particles into the plasma are next described. The advantages and limitations of these techniques in comparison with the neutral techniques are discussed, followed by a description of specific techniques.

  3. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, L.E.

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region are described. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10/sup 17/ to 10/sup 20/.

  4. Working group report on beam plasmas, electronic propulsion, and active experiments using beams

    NASA Technical Reports Server (NTRS)

    Dawson, J. M.; Eastman, T.; Gabriel, S.; Hawkins, J.; Matossian, J.; Raitt, J.; Reeves, G.; Sasaki, S.; Szuszczewicz, E.; Winkler, J. R.

    1986-01-01

    The JPL Workshop addressed a number of plasma issues that bear on advanced spaceborne technology for the years 2000 and beyond. Primary interest was on the permanently manned space station with a focus on identifying environmentally related issues requiring early clarification by spaceborne plasma experimentation. The Beams Working Group focused on environmentally related threats that platform operations could have on the conduct and integrity of spaceborne beam experiments and vice versa. Considerations were to include particle beams and plumes. For purposes of definition it was agreed that the term particle beams described a directed flow of charged or neutral particles allowing single-particle trajectories to represent the characteristics of the beam and its propagation. On the other hand, the word plume was adopted to describe a multidimensional flow (or expansion) of a plasma or neutral gas cloud. Within the framework of these definitions, experiment categories included: (1) Neutral- and charged-particle beam propagation, with considerations extending to high powers and currents. (2) Evolution and dynamics of naturally occurring and man-made plasma and neutral gas clouds. In both categories, scientific interest focused on interactions with the ambient geoplasma and the evolution of particle densities, energy distribution functions, waves, and fields.

  5. Observations of ionospheric electron beams in the plasma sheet.

    PubMed

    Zheng, H; Fu, S Y; Zong, Q G; Pu, Z Y; Wang, Y F; Parks, G K

    2012-11-16

    Electrons streaming along the magnetic field direction are frequently observed in the plasma sheet of Earth's geomagnetic tail. The impact of these field-aligned electrons on the dynamics of the geomagnetic tail is however not well understood. Here we report the first detection of field-aligned electrons with fluxes increasing at ~1 keV forming a "cool" beam just prior to the dissipation of energy in the current sheet. These field-aligned beams at ~15 R(E) in the plasma sheet are nearly identical to those commonly observed at auroral altitudes, suggesting the beams are auroral electrons accelerated upward by electric fields parallel (E([parallel])) to the geomagnetic field. The density of the beams relative to the ambient electron density is δn(b)/n(e)~5-13% and the current carried by the beams is ~10(-8)-10(-7) A m(-2). These beams in high β plasmas with large density and temperature gradients appear to satisfy the Bohm criteria to initiate current driven instabilities.

  6. Threshold criterion for a space simulation beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.; Walker, D. N.; Papadopoulos, K.; Bernstein, W.; Lin, C. S.

    1982-01-01

    An experimental and theoretical study of the threshold characteristics of a space simulation beam-plasma discharge with emphasis on density profiles and a density-dependent ignition criterion. The study included various beam-plasma conditions covering beam currents from 8 to 85 mA, beam energies from 0.8 to 2.0 keV, and magnetic fields at 0.9 and 1.5 G. The study included experimental determinations of radial profiles of electron density for each of the selected conditions extending from a low-density, pre-beam-plasma discharge state to a strong beam-plasma discharge condition. The experimental results are shown to agree with detailed model calculations, which consider the beam-plasma discharge to be produced by large-amplitude electron plasma waves resulting from the beam-plasma interaction.

  7. Spectral signature of the beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Hallinan, T. J.; Deehr, C. S.; Hoch, E.; Viereck, R.; Bernstein, W.; Konradi, A.

    1988-01-01

    The effect of the beam current on the spectrum of a beam plasma discharge (BPD) in N2 at 50, 100, or 400 microtorr is investigated experimentally in the 2.6-m chamber described by Bernstein et al. (1983). The results are presented graphically and discussed in detail. An increase in the ratio of first positive N2 emissions to first negative N2(+) emissions at BPD onset is shown to disappear at currents above the BPD threshold and is attributed to a large population of suprathermal electrons.

  8. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    SciTech Connect

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-04

    Bunch driven plasma wakefield accelerators (PWFA), such as the 'plasma afterburner', are a promising emerging method for significantly increasing the energy output of conventional particle accelerators. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two and multi-bunch drive beams.

  9. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-01

    Bunch driven plasma wakefield accelerators (PWFA), such as the "plasma afterburner," are a promising emerging method for significantly increasing the energy output of conventional particle accelerators [1]. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) [2] and Holographic (FDH) [3] diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two [4] and multi-bunch [5] drive beams.

  10. Restrike Particle Beam Experiments on a Dense Plasma Focus.

    DTIC Science & Technology

    1980-11-30

    soft Xray spectrometer should enable the formation of a fairly complete picture of the plasma phenomena as well as that of the beams for input into the...SSNTD are insensitive to light, electrons or Xrays 2) Record is virtually permanent 3) Direct measurement of fast particles is possible and (detection...detectors. The bands are delimited by Ross balanced filtering technique. This technique uses the fact that the stopping power for xrays has 3narp edges at

  11. Three regimes of relativistic beam - plasma interaction

    SciTech Connect

    Muggli, P.; Allen, B.; Fang, Y.; Yakimenko, V.; Babzien, M.; Kusche, K.; Fedurin, M.; Vieira, J.; Martins, J.; Silva, L.

    2012-12-21

    Three regimes of relativistic beam - plasma interaction can in principle be reached at the ATF depending on the relative transverse and longitudinal size of the electron bunch when compared to the cold plasma collisionless skin depth c?{omega}{sub pe}: the plasma wakefield accelerator (PWFA), the self-modulation instability (SMI), and the current filamentation instability (CFI) regime. In addition, by choosing the bunch density, the linear, quasi-nonlinear and non linear regime of the PWFA can be reached. In the case of the two instabilities, the bunch density determines the growth rate and therefore the occurrence or not of the instability. We briefly describe these three regimes and outline results demonstrating that all these regime have or will be reached experimentally. We also outline planned and possible follow-on experiments.

  12. Investigation of plasma-surface interaction at plasma beam facilities

    NASA Astrophysics Data System (ADS)

    Kurnaev, V.; Vizgalov, I.; Gutorov, K.; Tulenbergenov, T.; Sokolov, I.; Kolodeshnikov, A.; Ignashev, V.; Zuev, V.; Bogomolova, I.; Klimov, N.

    2015-08-01

    The new Plasma Beam Facility (PBF) has been put into operation for assistance in testing of plasma faced components at Material Science Kazakhstan Tokamak (KTM). PBF includes a powerful electron gun (up to 30 kV, 1 A) and a high vacuum chamber with longitudinal magnetic field coils (up to 0.2 T). The regime of high vacuum electron beam transportation is used for thermal tests with power density at the target surface up to 10 GW/m2. The beam plasma discharge (BPD) regime with a gas-puff is used for generation of intensive ion fluxes up to 3 ṡ 1022 m-2 s-1. Initial tests of the KTM PBF's capabilities were carried out: various discharge regimes, carbon deposits cleaning, simultaneous thermal and ion impacts on radiation cooled refractory targets. With a water-cooled target the KTM PBF could be used for high heat flux tests of materials (validated by the experiment with W mock-up at the PR-2 PBF).

  13. Ribbon Ion Beam with Controlled Directionality and Local Reactive Chemistry

    NASA Astrophysics Data System (ADS)

    Biloiu, Costel; Gilchrist, Glen; Kontos, Alex; Basame, Solomon; Rockwell, Tyler; Campbell, Chris; Daniels, Kevin; Allen, Ernest; Wallace, Jay; Ballou, Jon; Hertel, Richard; Chen, Tsung-Liang; Liang, Shurong; Singh, Vikram

    2016-09-01

    A plasma processing technology designed for etch of 3D semiconductor structures is presented. The technology is characterized by controllable ion directionality and local reactive chemistry and it is based on proprietary Applied Materials - Varian Semiconductor Equipment ribbon ion beam architecture. It uses a combination of inert gas ion beam and injection of reactive chemical species at the Point-of-Use (PoU), i.e., at the wafer surface. The ion source uses an inductively coupled plasma source and a diode-type extraction optics. A beam shaping electrode allows extraction of two symmetrical ribbon-like beamlets. The ion beam has in situ controllable ion angular distribution in both mean angle and angular spread. The beam has a uniform distribution of beam current and angles over a waist exceeding 300 mm, allowing full wafer processing in one pass. Chemical compounds are delivered at PoU through linear shower heads. The reactive chemical compound delivered in this fashion maintains its molecular integrity. This result in protection of the trench side walls from deposition of etch residue and facilitates formation of volatile byproducts. The technology was used successfully for mitigation of Magnetic Tunel Junction etch residue. Other applications were this technology differentiate from present technologies are contact liner etch, Co recess, and 1D hole elongation.

  14. Electron beam direct write: shaped beam overcomes resolution concerns

    NASA Astrophysics Data System (ADS)

    Stolberg, Ines; Pain, Laurent; Kretz, Johannes; Boettcher, Monika; Doering, Hans-Joachim; Gramss, Juergen; Hahmann, Peter

    2007-02-01

    In semiconductor industry time to market is one of the key success factors. Therefore fast prototyping and low-volume production will become extremely important for developing process technologies that are well ahead of the current technological level. Electron Beam Lithography has been launched for industrial use as a direct write technology for these types of applications. However, limited throughput rates and high tool complexity have been seen as the major concerns restricting the industrial use of this technology. Nowadays this begins to change. Variable Shaped Beam (VSB) writers have been established in Electron Beam Direct Write (EBDW) on Si or GaAs. In the paper semiconductor industry requirements to EBDW will be outlined. Behind this background the Vistec SB3050 lithography system will be reviewed. The achieved resolution enhancement of the VSB system down to the 22nm node exposure capability will be discussed in detail; application examples will be given. Combining EBDW in a Mix and Match technology with optical lithography is one way to utilize the high flexibility advantage of this technology and to overcome existing throughput concerns. However, to some extend a common Single Electron Beam Technology (SBT) will always be limited in throughput. Therefore Vistec's approach of a system that is based on the massive parallelisation of beams (MBT), which was initially pursued in a European Project, will also be discussed.

  15. Plasma dark matter direct detection

    SciTech Connect

    Clarke, J.D.; Foot, R. E-mail: rfoot@unimelb.edu.au

    2016-01-01

    Dark matter in spiral galaxies like the Milky Way may take the form of a dark plasma. Hidden sector dark matter charged under an unbroken U(1)' gauge interaction provides a simple and well defined particle physics model realising this possibility. The assumed U(1)' neutrality of the Universe then implies (at least) two oppositely charged dark matter components with self-interactions mediated via a massless 'dark photon' (the U(1)' gauge boson). In addition to nuclear recoils such dark matter can give rise to keV electron recoils in direct detection experiments. In this context, the detailed physical properties of the dark matter plasma interacting with the Earth is required. This is a complex system, which is here modelled as a fluid governed by the magnetohydrodynamic equations. These equations are numerically solved for some illustrative examples, and implications for direct detection experiments discussed. In particular, the analysis presented here leaves open the intriguing possibility that the DAMA annual modulation signal is due primarily to electron recoils (or even a combination of electron recoils and nuclear recoils). The importance of diurnal modulation (in addition to annual modulation) as a means of probing this kind of dark matter is also emphasised.

  16. PLASMA WAKE EXCITATION BY LASERS OR PARTICLE BEAMS

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric; Benedetti, Carlo; Toth, Csaba; Geddes, Cameron; Leemans, Wim

    2011-04-01

    Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed. Plasma-based accelerators have attracted considerable attention owing to the ultrahigh field gradients sustainable in a plasma wave, enabling compact accelerators. These relativistic plasma waves are excited by displacing electrons in a neutral plasma. Two basic mechanisms for excitation of plasma waves are actively being researched: (i) excitation by the nonlinear ponderomotive force (radiation pressure) of an intense laser or (ii) excitation by the space-charge force of a dense charged particle beam. There has been significant recent experimental success using lasers and particle beam drivers for plasma acceleration. In particular, for laser-plasma accelerators (LPAs), the demonstration at LBNL in 2006 of high-quality, 1 GeV electron beams produced in approximately 3 cm plasma using a 40 TW laser. In 2007, for beam-driven plasma accelerators, or plasma-wakefield accelerators (PWFAs), the energy doubling over a meter to 42 GeV of a fraction of beam electrons on the tail of an electron beam by the plasma wave excited by the head was demonstrated at SLAC. These experimental successes have resulted in further interest in the development of plasma-based acceleration as a basis for a linear collider, and preliminary collider designs using laser drivers and beam drivers are being developed. The different physical mechanisms of plasma wave excitation, as well as the typical characteristics of the drivers, have implications for accelerator design. In the following, we identify the similarities and differences between wave excitation by lasers and particle beams. The field structure of the plasma wave driven by lasers or particle beams is discussed, as well as the

  17. Collisionless relaxation in beam-plasma systems

    SciTech Connect

    Backhaus, Ekaterina Yu.

    2001-01-01

    This thesis reports the results from the theoretical investigations, both numerical and analytical, of collisionless relaxation phenomena in beam-plasma systems. Many results of this work can also be applied to other lossless systems of plasma physics, beam physics and astrophysics. Different aspects of the physics of collisionless relaxation and its modeling are addressed. A new theoretical framework, named Coupled Moment Equations (CME), is derived and used in numerical and analytical studies of the relaxation of second order moments such as beam size and emittance oscillations. This technique extends the well-known envelope equation formalism, and it can be applied to general systems with nonlinear forces. It is based on a systematic moment expansion of the Vlasov equation. In contrast to the envelope equation, which is derived assuming constant rms beam emittance, the CME model allows the emittance to vary through coupling to higher order moments. The CME model is implemented in slab geometry in the absence of return currents. The CME simulation yields rms beam sizes, velocity spreads and emittances that are in good agreement with particle-in-cell (PIC) simulations for a wide range of system parameters. The mechanism of relaxation is also considered within the framework of the CME system. It is discovered that the rapid relaxation or beam size oscillations can be attributed to a resonant coupling between different modes of the system. A simple analytical estimate of the relaxation time is developed. The final state of the system reached after the relaxation is complete is investigated. New and accurate analytical results for the second order moments in the phase-mixed state are obtained. Unlike previous results, these connect the final values of the second order moments with the initial beam mismatch. These analytical estimates are in good agreement with the CME model and PIC simulations. Predictions for the final density and temperature are developed that show

  18. Vortex stabilized electron beam compressed fusion grade plasma

    SciTech Connect

    Hershcovitch, Ady

    2014-03-19

    Most inertial confinement fusion schemes are comprised of highly compressed dense plasmas. Those schemes involve short, extremely high power, short pulses of beams (lasers, particles) applied to lower density plasmas or solid pellets. An alternative approach could be to shoot an intense electron beam through very dense, atmospheric pressure, vortex stabilized plasma.

  19. Second harmonic generation of Cosh-Gaussian laser beam in collisional plasma with nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Singh, Navpreet; Gupta, Naveen; Singh, Arvinder

    2016-12-01

    This paper investigates second harmonic generation (SHG) of an intense Cosh-Gaussian (ChG) laser beam propagating through a preformed underdense collisional plasma with nonlinear absorption. Nonuniform heating of plasma electrons takes place due to the nonuniform irradiance of intensity along the wavefront of laser beam. This nonuniform heating of plasma leads to the self-focusing of the laser beam and thus produces strong density gradients in the transverse direction. The density gradients so generated excite an electron plasma wave (EPW) at pump frequency that interacts with the pump beam to produce its second harmonics. To envision the propagation dynamics of the ChG laser beam, moment theory in Wentzel-Kramers-Brillouin (W.K.B) approximation has been invoked. The effects of nonlinear absorption on self-focusing of the laser beam as well as on the conversion efficiency of its second harmonics have been theoretically investigated.

  20. Plasma ion sources and ion beam technology inmicrofabrications

    SciTech Connect

    Ji, Lili

    2007-01-01

    For over decades, focused ion beam (FIB) has been playing a very important role in microscale technology and research, among which, semiconductor microfabrication is one of its biggest application area. As the dimensions of IC devices are scaled down, it has shown the need for new ion beam tools and new approaches to the fabrication of small-scale devices. In the meanwhile, nanotechnology has also deeply involved in material science research and bioresearch in recent years. The conventional FIB systems which utilize liquid gallium ion sources to achieve nanometer scale resolution can no longer meet the various requirements raised from such a wide application area such as low contamination, high throughput and so on. The drive towards controlling materials properties at nanometer length scales relies on the availability of efficient tools. In this thesis, three novel ion beam tools have been developed and investigated as the alternatives for the conventional FIB systems in some particular applications. An integrated focused ion beam (FIB) and scanning electron microscope (SEM) system has been developed for direct doping or surface modification. This new instrument employs a mini-RF driven plasma source to generate focused ion beam with various ion species, a FEI two-lens electron (2LE) column for SEM imaging, and a five-axis manipulator system for sample positioning. An all-electrostatic two-lens column has been designed to focus the ion beam extracted from the source. Based on the Munro ion optics simulation, beam spot sizes as small as 100 nm can be achieved at beam energies between 5 to 35 keV if a 5 μm-diameter extraction aperture is used. Smaller beam spot sizes can be obtained with smaller apertures at sacrifice of some beam current. The FEI 2LE column, which utilizes Schottky emission, electrostatic focusing optics, and stacked-disk column construction, can provide high-resolution (as small as 20 nm) imaging capability, with fairly long working distance (25

  1. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    SciTech Connect

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O’Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

  2. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator.

    PubMed

    Gessner, Spencer; Adli, Erik; Allen, James M; An, Weiming; Clarke, Christine I; Clayton, Chris E; Corde, Sebastien; Delahaye, J P; Frederico, Joel; Green, Selina Z; Hast, Carsten; Hogan, Mark J; Joshi, Chan; Lindstrøm, Carl A; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A; Mori, Warren B; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m(-1) is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

  3. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    PubMed Central

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-01-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m−1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations. PMID:27250570

  4. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    DOE PAGES

    Gessner, Spencer; Adli, Erik; Allen, James M.; ...

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

  5. Ultrafast Directional Beam Switching in Coupled VCSELs

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast directional beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 microns in diameter placed about 1 micron apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees.

  6. Waves in relativistic electron beam in low-density plasma

    NASA Astrophysics Data System (ADS)

    Sheinman, I.; Sheinman (Chernenco, J.

    2016-11-01

    Waves in electron beam in low-density plasma are analyzed. The analysis is based on complete electrodynamics consideration. Dependencies of dispersion laws from system parameters are investigated. It is shown that when relativistic electron beam is passed through low-density plasma surface waves of two types may exist. The first type is a high frequency wave on a boundary between the beam and neutralization area and the second type wave is on the boundary between neutralization area and stationary plasma.

  7. Parametric instabilities in an electron beam plasma system

    NASA Astrophysics Data System (ADS)

    Nakach, R.; Cuperman, S.; Gell, Y.; Levush, B.

    1981-08-01

    The excitation of low-frequency parametric instabilities by a finite wavelength pump, in a system consisting of a warm electron plasma traversed by a warm electron beam, is investigated in a fluid dissipationless model. The appropriate dispersion relation is derived for the three-dimensional problem in a magnetized plasma with arbitrary directions for the waves, and the one-dimensional case is analyzed numerically. It is shown that when the plasma-electron Debye length is larger than the beam-electron Debye length, two low frequency electrostatic instabilities may exist simultaneously. For this case, their growth rates might differ by more than one order of magnitude and the effect of the pump field on the larger growth rate instability is not very significant. For the opposite case, only one instability can be excited which reduces to the parametric instability discussed by Fried et al. (1976), when the beam is switched off. Attention is given to the case corresponding to equal Debye lengths where, in addition to the previously mentioned parametric instability, a large growth rate instability can be excited, which, however, depends on the amplitude of the pump field.

  8. Fundamentals and applications of a plasma-processing system based on electron-beam ionizationa)

    NASA Astrophysics Data System (ADS)

    Leonhardt, D.; Walton, S. G.; Fernsler, R. F.

    2007-05-01

    Plasmas generated from moderate energy (2-5keV) electron beams (e-beam) have unique, attractive characteristics that are ideal for materials processing applications. These plasmas possess low electron temperatures (<0.5eV), variable plasma densities (109-1012cm-3) with an improved control of plasma species generation, and perhaps most importantly, a direct scalability to processing areas exceeding one square meter. These characteristics are due to the plasma ionization being driven by the e-beam instead of an external electromagnetic field as used in conventional processing plasma sources. Theoretical and experimental system details are discussed in terms of plasma operating conditions applied to three different surface modification approaches: metal nitriding, negative ion etching, and polymer surface energy tailoring.

  9. Suprathermal electrons produced by beam-plasma-discharge

    NASA Technical Reports Server (NTRS)

    Sharp, W. E.

    1982-01-01

    Experiments conducted with a low energy plasma lens, HARP, in the electron beam of the large vacuum chamber at Johnson Space Center indicate that an enhanced population of 50 to 300 volt electrons appear when the beam goes into the Beam-Plasma Discharge (BPD) mode. Below the BPD instability the electron distribution appears to be characterized as non-energized single particle scattering and energy loss. At 100 cm from the beam core in the BPD mode the fluxes parallel to the beam are reduced by a factor of 20 with respect to the fluxes at 25 cm. Some evidence for isotropy near the beam core is presented.

  10. Electromagnetic radiation and nonlinear energy flow in an electron beam-plasma system

    NASA Technical Reports Server (NTRS)

    Whelan, D. A.; Stenzel, R. L.

    1985-01-01

    It is shown that the unstable electron-plasma waves of a beam-plasma system can generate electromagnetic radiation in a uniform plasma. The generation mechanism is a scattering of the unstable electron plasma waves off ion-acoustic waves, producing electromagnetic waves whose frequency is near the local plasma frequency. The wave vector and frequency matching conditions of the three-wave mode coupling are experimentally verified. The electromagnetic radiation is observed to be polarized with the electric field parallel to the beam direction, and its source region is shown to be localized to the unstable plasma wave region. The frequency spectrum shows negligible intensity near the second harmonic of the plasma frequency. These results suggest that the observed electromagnetic radiation of type III solar bursts may be generated near the local plasma frequency and observed downstream where the wave frequency is near the harmonic of the plasma frequency.

  11. INTERACTION OF MUON BEAM WITH PLASMA DEVELOPED DURING IONIZATION COOLING

    SciTech Connect

    S. Ahmed, D. Kaplan, T. Roberts, L. Spentzouris, K. Beard

    2012-07-01

    Particle-in-cell simulations involving the interaction of muon beam (peak density 10{sup 18} m{sup 3}) with Li plasma (ionized medium) of density 10{sup 16}-10{sup 22} m{sup -3} have been performed. This study aimed to understand the effects of plasma on an incoming beam in order to explore scenario developed during the process of ionization cooling. The computer code takes into account the self-consistent electromagnetic effects of beam interacting with plasma. This study shows that the beam can pass through the plasma of densities four order of magnitude higher than its peak density. The low density plasmas are wiped out by the beam, however, the resonance is observed for densities of similar order. Study reveals the signature of plasma wakefield acceleration.

  12. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, Lester E.

    1981-01-01

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target plasma is ionized prior to application of the electron beam by means of a laser or other preionization source. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region within the high density plasma target.

  13. Intense ion beam neutralization using underdense background plasma

    SciTech Connect

    Berdanier, William; Roy, Prabir K.; Kaganovich, Igor

    2015-01-15

    Producing an overdense background plasma for neutralization purposes with a density that is high compared to the beam density is not always experimentally possible. We show that even an underdense background plasma with a small relative density can achieve high neutralization of intense ion beam pulses. Using particle-in-cell simulations, we show that if the total plasma electron charge is not sufficient to neutralize the beam charge, electron emitters are necessary for effective neutralization but are not needed if the plasma volume is so large that the total available charge in the electrons exceeds that of the ion beam. Several regimes of possible underdense/tenuous neutralization plasma densities are investigated with and without electron emitters or dense plasma at periphery regions, including the case of electron emitters without plasma, which does not effectively neutralize the beam. Over 95% neutralization is achieved for even very underdense background plasma with plasma density 1/15th the beam density. We compare results of particle-in-cell simulations with an analytic model of neutralization and find close agreement with the particle-in-cell simulations. Further, we show experimental data from the National Drift Compression experiment-II group that verifies the result that underdense plasma can neutralize intense heavy ion beams effectively.

  14. Studies of Ion Beam Charge Neutralization by Ferroelectric Plasma Sources

    NASA Astrophysics Data System (ADS)

    Stepanov, A.; Gilson, E. P.; Grisham, L.; Davidson, R. C.

    2013-10-01

    Space-charge forces limit the possible transverse compression of high perveance ion beams that are used in ion-beam-driven high energy density physics applications; the minimum radius to which a beam can be focused is an increasing function of perveance. The limit can be overcome if a plasma is introduced in the beam path between the focusing element and the target in order to neutralize the space charge of the beam. This concept has been implemented on the Neutralized Drift Compression eXperiment (NDCX) at LBNL using Ferroelectric Plasma Sources (FEPS). In our experiment at PPPL, we propagate a perveance-dominated ion beam through a FEPS to study the effect of the neutralizing plasma on the beam envelope and its evolution in time. A 30-60 keV space-charge-dominated Argon beam is focused with an Einzel lens into a FEPS located at the beam waist. The beam is intercepted downstream from the FEPS by a movable Faraday cup that provides time-resolved 2D current density profiles of the beam spot on target. We report results on: (a) dependence of charge neutralization on FEPS plasma density; (b) effects on beam emittance, and (c) time evolution of the beam envelope after the FEPS pulse. Research supported by the U.S. Department of Energy.

  15. Plasma and ion beam processing at Los Alamos

    SciTech Connect

    Rej, D.J.; Davis, H.A.; Henins, I.

    1994-07-01

    Efforts are underway at Los Alamos National Laboratory to utilize plasma and intense ion beam science and technology of the processing of advanced materials. A major theme involves surface modification of materials, e.g., etching, deposition, alloying, and implantation. In this paper, we concentrate on two programs, plasma source ion implantation and high-intensity pulsed ion beam deposition.

  16. Plasma-parameter measurements using neutral-particle-beam attenuation

    SciTech Connect

    Foote, J H; Molvik, A W; Turner, W C

    1982-07-07

    Intense and energetic neutral-particle-beam injection used for fueling or heating magnetically confined, controlled-fusion experimental plasmas can also provide diagnostic measurements of the plasmas. The attenuation of an atomic beam (mainly from charge-exchange and ionization interactions) when passing through a plasma gives the plasma line density. Orthogonal arrays of highly collimated detectors of the secondary-electron-emission type have been used in magnetic-mirror experiments to measure neutral-beam attenuation along chords through the plasma volume at different radial and axial positions. The radial array is used to infer the radial plasma-density profile; the axial array, to infer the axial plasma-density profile and the ion angular distribution at the plasma midplane.

  17. Multisymplectic Integration for Beam and Plasma Simulations

    NASA Astrophysics Data System (ADS)

    Webb, Stephen; RadiaSoft, LLC Team

    2015-11-01

    Particle-in-cell methods are a standard tool for simulating charged particle systems such as fusion plasmas, intense beams, and laser- and beam-driven wakefield accelerators. Conventional methods have been successful in studying short-term dynamics, however numerical instabilities and artifacts such as grid heating make long-time simulations unreliable. A similar issue existed in single particle tracking for storage rings in the 1980s, which led to the development of symplectic algorithms. The essential insight that if the physical equations of motion derive from a least-action principle, then so too should the numerical equations of motion. The resulting update sequence preserves a symplectic 2-form, which is a strong constraint on the numerical solutions. The resulting algorithms are stable and accurate over very long simulation times. This same structure exists for field theories as well as single-particle dynamics. Such multisymplectic integrators have good stability properties and naturally encode conservation laws, making them ideal for simulations over many oscillations of the system. We present here a number of examples where multisymplectic algorithms have been used over very long time scales. This work was sponsored by the Air Force Office of Scientific Research, Young Investigator Program, under contract no. FA9550-15-C-0031. Distribution Statement A. Approved for public release; distribution is unlimited.

  18. Plasma lens experiments at the Final Focus Test Beam

    SciTech Connect

    Barletta, B. |; Chattopadhyay, S.; Chen, P.

    1993-04-01

    We intend to carry out a series of plasma lens experiments at the Final Focus Test Beam facility at SLAC. These experiments will be the first to study the focusing of particle beams by plasma focusing devices in the parameter regime of interest for high energy colliders, and is expected to lead to plasma lens designs capable of unprecedented spot sizes. Plasma focusing of positron beams will be attempted for the first time. We will study the effects of lens aberrations due to various lens imperfections. Several approaches will be applied to create the plasma required including laser ionization and beam ionization of a working gas. At an increased bunch population of 2.5 {times} 10{sup 10}, tunneling ionization of a gas target by an electron beam -- an effect which has never been observed before -- should be significant. The compactness of our device should prove to be of interest for applications at the SLC and the next generation linear colliders.

  19. A beam-maser instability: Direct amplification of radiation

    NASA Astrophysics Data System (ADS)

    Chen, Y. P.; Zhou, G. C.; Yoon, Peter H.; Wu, C. S.

    2002-06-01

    The cyclotron maser instability has been applied in the past to laboratory microwave generation devices, and radiation from planetary magnetospheres, such as Earth's kilometric radiation and Jovian decametric radiation. Recently, the same concept was put forth to explain solar coronal radio bursts. In particular, it was suggested that the ordinary (O) mode propagating in antiparallel direction with respect to the electron beam may be important. For this reason, this article revisits the maser instability theory with a particular emphasis on understanding the key difference between forward- and backward-propagating O-mode masers. It is found that the O-mode maser instability is excited over a significant range of wave phase angle which corresponds to the backward propagation. Of the various physical parameters the average beam speed and the ratio of plasma-to-gyro-frequencies, ωp/Ω, play important roles. Past discussions have emphasized the role of ωp/Ω. The present analysis also includes the effects of average beam speed on the instability. It is shown that there is a critical beam speed for the instability onset, beyond which the growth rate is quasi-independent of the beam speed. Such a finding has not been reported in the literature before.

  20. TEBPP: Theoretical and Experimental study of Beam-Plasma-Physics

    NASA Technical Reports Server (NTRS)

    Anderson, H. R.; Bernstein, W.; Linson, L. M.; Papadopoulos, K.; Kellogg, P. J.; Szuszczewicz, E. P.; Hallinan, T. J.; Leinbach, H.

    1980-01-01

    The interaction of an electron beam (0 to 10 keV, 0 to 1.5 Amp) with the plasma and neutral atmospheres at 200 to 400 km altitude is studied with emphasis on applications to near Earth and cosmical plasmas. The interaction occurs in four space time regions: (1) near electron gun, beam coming into equilibrium with medium; (2) equilibrium propagation in ionosphere; (3) ahead of beam pulse, temporal and spatial precursors; (4) behind a beam pulse. While region 2 is of the greatest interest, it is essential to study Region 1 because it determines the characteristics of the beam as it enters 2 through 4.

  1. Beam transport with magnetic solenoids and plasma lenses

    SciTech Connect

    Noble, R.J.

    1988-10-01

    We examine the behavior of axisymmetric space-charge dominated beams in transport lines using numerical simulation. A typical transport line consisting of two axisymmetric linear lenses used to make a continuous beam from an ion source to a radio frequency quadrupole (RFQ) is considered. We compare the beam evolution when both lenses are magnetic solenoids or Gabor plasma lenses for beams with different initial density profiles. Emittance oscillations due to nonlinear space-charge forces by the action of plasma lenses in which space-charge fields are shielded, but beam mismatch at the RFQ entrance can be significant for both types of lens. 8 refs., 6 figs.

  2. A preliminary model of ion beam neutralization. [in thruster plasmas

    NASA Technical Reports Server (NTRS)

    Parks, D. E.; Katz, I.

    1979-01-01

    A theoretical model of neutralized thruster ion beam plasmas has been developed. The basic premise is that the beam forms an electrostatic trap for the neutralizing electrons. A Maxwellian spectrum of electron energies is maintained by collisions between trapped electrons and by collective randomization of velocities of electrons injected from the neutralizer into the surrounding plasma. The theory contains the observed barometric law relationship between electron density and electron temperatures and ion beam spreading in good agreement with measured results.

  3. Population Inversions in Ablation Plasmas Generated by Intense Electron Beams.

    DTIC Science & Technology

    1986-11-30

    beam driven carbon anode plasmas. Diode closure results ..,.in three phases of beam-plasma evolution which are summarized below: Stage I: Deposited...enough for anode plasma forma- tion before the diode shorts. Spectroscopic data for noncrowbarred shots (dose 1 500-800 J/g) indicate the presence of CII...inconsistent with previously proposed kinetic mechanisms for the N2 laser pumped by helium. With a simple- model of the chemical kinetics, we have shown

  4. Physics of beam self-modulation in plasma wakefield accelerators

    SciTech Connect

    Lotov, K. V.

    2015-10-15

    The self-modulation instability is a key effect that makes possible the usage of nowadays proton beams as drivers for plasma wakefield acceleration. Development of the instability in uniform plasmas and in plasmas with a small density up-step is numerically studied with the focus at nonlinear stages of beam evolution. The step parameters providing the strongest established wakefield are found, and the mechanism of stable bunch train formation is identified.

  5. Generation And Applications Of Electron-Beam Plasma Flows

    NASA Astrophysics Data System (ADS)

    Vasiliev, M. N.; Tun Win, Aung

    2015-03-01

    Plasma flows generated by continuous or interrupted injection of an electron beam into subsonic or supersonic gaseous streams are considered. Liquid and powder spraying by the electron-beam plasma (EBP) flows is studied as a technique of the aerosol plasma generation. A number of experimental setups generating both free plasma jets and plasma flows in channels are described. Examples of the EBP flows applications for industrial and aerospace technologies are given. The applications are shown to be based on unique properties of the EBP and its stability within very wide ranges of the plasma generation conditions. Some applications of the Hybrid Plasma (HP) generated by combined action of the electron beam (EB) and intermittent gas discharge on flows of gaseous mixtures and aerosols are presented as well.

  6. Shunting arc plasma source for pure carbon ion beam.

    PubMed

    Koguchi, H; Sakakita, H; Kiyama, S; Shimada, T; Sato, Y; Hirano, Y

    2012-02-01

    A plasma source is developed using a coaxial shunting arc plasma gun to extract a pure carbon ion beam. The pure carbon ion beam is a new type of deposition system for diamond and other carbon materials. Our plasma device generates pure carbon plasma from solid-state carbon material without using a hydrocarbon gas such as methane gas, and the plasma does not contain any hydrogen. The ion saturation current of the discharge measured by a double probe is about 0.2 mA∕mm(2) at the peak of the pulse.

  7. Diffraction Effects in Directed Radiation Beams

    DTIC Science & Technology

    1990-04-03

    Toraldo di Francia, NuoVo Cimento, Suppl. 9, 426 (1952)> 3. W T. Welford, Qptics, (Onfordi University Press, New York, 1981), chap. 3. 4 . C.. J. Bouwkarnp...Naval Research Laboratoy 4 Washington, DC 20375.5000 It) NRL Memorandum Report 6609 Diffraction Effects in Directed Radiation BeamsI B. HAFIZI* AND P...Wq ts :Iiio ’’,t tor VVes-q , .I (), O’at 1 4 , nci,rr itlon ot)$rmtioiI ld AepoTiQ , 21 ,’ tl,’fc sonr [I•11 Fi0r h ci ti’ 204, i litiqtOt VA 220 0

  8. Nonlinear Plasma Waves Excitation by Intense Ion Beams in Background Plasma

    SciTech Connect

    Igor D. Kaganovich; Edward A. Startsev; Ronald C. Davidson

    2004-04-15

    Plasma neutralization of an intense ion pulse is of interest for many applications, including plasma lenses, heavy ion fusion, cosmic ray propagation, etc. An analytical electron fluid model has been developed to describe the plasma response to a propagating ion beam. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration {tau}{sub b} is much longer than the electron plasma period 2{pi}/{omega}{sub p}, where {omega}{sub p} = (4{pi}e{sup 2}n{sub p}/m){sup 1/2} is the electron plasma frequency and n{sub p} is the background plasma density. In the opposite limit, the beam pulse excites large-amplitude plasma waves. If the beam density is larger than the background plasma density, the plasma waves break. Theoretical predictions are compared with the results of calculations utilizing a particle-in-cell (PIC) code. The cold electron fluid results agree well with the PIC simulations for ion beam propagation through a background plasma. The reduced fluid description derived in this paper can provide an important benchmark for numerical codes and yield scaling relations for different beam and plasma parameters. The visualization of numerical simulation data shows complex collective phenomena during beam entry and exit from the plasma.

  9. Plasma nanoscience: setting directions, tackling grand challenges

    NASA Astrophysics Data System (ADS)

    (Ken Ostrikov, Kostya; Cvelbar, Uros; Murphy, Anthony B.

    2011-05-01

    This review paper presents historical perspectives, recent advances and future directions in the multidisciplinary research field of plasma nanoscience. The current status and future challenges are presented using a three-dimensional framework. The first and the largest dimension covers the most important classes of nanoscale objects (nanostructures, nanofeatures and nanoassemblies/nanoarchitectures) and materials systems, namely carbon nanotubes, nanofibres, graphene, graphene nanoribbons, graphene nanoflakes, nanodiamond and related carbon-based nanostructures; metal, silicon and other inorganic nanoparticles and nanostructures; soft organic nanomaterials; nano-biomaterials; biological objects and nanoscale plasma etching. In the second dimension, we discuss the most common types of plasmas and plasma reactors used in nanoscale plasma synthesis and processing. These include low-temperature non-equilibrium plasmas at low and high pressures, thermal plasmas, high-pressure microplasmas, plasmas in liquids and plasma-liquid interactions, high-energy-density plasmas, and ionized physical vapour deposition as well as some other plasma-enhanced nanofabrication techniques. In the third dimension, we outline some of the 'Grand Science Challenges' and 'Grand Socio-economic Challenges' to which significant contributions from plasma nanoscience-related research can be expected in the near future. The urgent need for a stronger focus on practical, outcome-oriented research to tackle the grand challenges is emphasized and concisely formulated as from controlled complexity to practical simplicity in solving grand challenges.

  10. A reflex electron beam discharge as a plasma source for electron beam generation

    SciTech Connect

    Murray, C.S.; Rocca, J.J.; Szapiro, B. )

    1988-10-01

    A reflex electron beam glow discharge has been used as a plasma source for the generation of broad-area electron beams. An electron current of 120 A (12 A/cm/sup 2/) was extracted from the plasma in 10 ..mu..s pulses and accelerated to energies greater than 1 keV in the gap between two grids. The scaling of the scheme for the generation of multikiloamp high-energy beams is discussed.

  11. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  12. A Novel Microwave Beam Steering Technique Using Plasma

    NASA Astrophysics Data System (ADS)

    Linardakis, Peter; Borg, Gerard G.; Harris, Jeffrey H.; Martin, Noel M.

    2002-10-01

    At frequencies above the plasma frequency, electromagnetic waves propagate through plasma with a wavelength longer than the free space wavelength. As a result, a plasma with a centrally peaked density profile can deflect rather than focus electromagnetic waves. We present a plasma device designed specifically to deflect a microwave beam as an alternative to conventional beam deflectors based on antenna arrays. A 22^rc deflection of Ka band microwave has been achieved using a laboratory plasma, with no detrimental effect on the beamwidth or side-lode level and structure. The use of a simple WKB model shows agreement and that the deflection can be increased with appropriate design. Results indicate the potential for increases in dynamic range, in power handling (for example from a gyrotron) and for the reduction of insertion losses over current beam steering systems. A ``plasma lens'' demonstrator device has also been designed to test practical performance aspects such as phase noise and to test optimization parameters.

  13. Monoenergetic beams of relativistic electrons from intense laser-plasma interactions.

    PubMed

    Mangles, S P D; Murphy, C D; Najmudin, Z; Thomas, A G R; Collier, J L; Dangor, A E; Divall, E J; Foster, P S; Gallacher, J G; Hooker, C J; Jaroszynski, D A; Langley, A J; Mori, W B; Norreys, P A; Tsung, F S; Viskup, R; Walton, B R; Krushelnick, K

    2004-09-30

    High-power lasers that fit into a university-scale laboratory can now reach focused intensities of more than 10(19) W cm(-2) at high repetition rates. Such lasers are capable of producing beams of energetic electrons, protons and gamma-rays. Relativistic electrons are generated through the breaking of large-amplitude relativistic plasma waves created in the wake of the laser pulse as it propagates through a plasma, or through a direct interaction between the laser field and the electrons in the plasma. However, the electron beams produced from previous laser-plasma experiments have a large energy spread, limiting their use for potential applications. Here we report high-resolution energy measurements of the electron beams produced from intense laser-plasma interactions, showing that--under particular plasma conditions--it is possible to generate beams of relativistic electrons with low divergence and a small energy spread (less than three per cent). The monoenergetic features were observed in the electron energy spectrum for plasma densities just above a threshold required for breaking of the plasma wave. These features were observed consistently in the electron spectrum, although the energy of the beam was observed to vary from shot to shot. If the issue of energy reproducibility can be addressed, it should be possible to generate ultrashort monoenergetic electron bunches of tunable energy, holding great promise for the future development of 'table-top' particle accelerators.

  14. A Space-Charge-Neutralizing Plasma for Beam Drift Compression

    SciTech Connect

    Roy, P.K.; Seidl, P.A.; Anders, A.; Bieniosek, F.M.; Coleman, J.E.; Gilson, E.P.; Greenway, W.; Grote, D.P.; Jung, J.Y.; Leitner, M.; Lidia, S.M.; Logan, B.G.; Sefkow, A.B.; Waldron, W.L.; Welch, D.R.

    2008-08-01

    Simultaneous radial focusing and longitudinal compression of intense ion beams are being studied to heat matter to the warm dense matter, or strongly coupled plasma regime. Higher compression ratios can be achieved if the beam compression takes place in a plasma-filled drift region in which the space-charge forces of the ion beam are neutralized. Recently, a system of four cathodic arc plasma sources has been fabricated and the axial plasma density has been measured. A movable plasma probe array has been developed to measure the radial and axial plasma distribution inside and outside of a {approx} 10 cm long final focus solenoid (FFS). Measured data show that the plasma forms a thin column of diameter {approx} 5 mm along the solenoid axis when the FFS is powered with an 8T field. Measured plasma density of {ge} 1 x 10{sup 13} cm{sup -3} meets the challenge of n{sub p}/Zn{sub b} > 1, where n{sub p} and n{sub b} are the plasma and ion beam density, respectively, and Z is the mean ion charge state of the plasma ions.

  15. Direct plasma interaction with living tissue

    NASA Astrophysics Data System (ADS)

    Fridman, Gregory

    For some time, plasma has been used in medicine to cauterize or cut tissue using heat and mechanical energy. In the recent decade, some researchers around the world have started to investigate how gas jets that pass through thermal plasma can be employed in medicine. This thesis presents the first investigation of biomedical uses of non-thermal plasma discharge which comes in direct contact with living tissue. It is demonstrated that the direct application of non-thermal plasma in air can cause rapid deactivation of bacteria on surfaces of tissues without causing any visible tissue damage. Medical need for such a device is discussed. Construction and operation of various types of non-thermal plasma power supplies and many types of treatment electrodes are presented as well. Application of this plasma to living organisms is shown to be safe from both the electrical perspective and from the biological perspective. Biological safety is revealed through a series of differential skin toxicity trials on human cadaver tissue, live hairless mouse skin tissue, live pig skin tissue, and finally in an open wound model on pigs. Direct non-thermal plasma in air is shown to deactivate bacteria about 100 times faster than indirect application using jets. A series of experiments reveal that this effectiveness is due to the ability of direct discharge to bring charges to tissue surfaces. It is demonstrated that neither ultraviolet (UV) radiation nor neutral active species such as hydroxyl radicals or ozone produced in plasma are responsible for the main effect on bacteria. Although much additional work remains on establishing detailed mechanism by which charges from plasma achieve this effect, the work carried out in this thesis clearly demonstrates that direct application of non-thermal plasma in air can be a very useful tool in medicine.

  16. Electron beam directed energy device and methods of using same

    DOEpatents

    Retsky, Michael W.

    2007-10-16

    A method and apparatus is disclosed for an electron beam directed energy device. The device consists of an electron gun with one or more electron beams. The device includes one or more accelerating plates with holes aligned for beam passage. The plates may be flat or preferably shaped to direct each electron beam to exit the electron gun at a predetermined orientation. In one preferred application, the device is located in outer space with individual beams that are directed to focus at a distant target to be used to impact and destroy missiles. The aimings of the separate beams are designed to overcome Coulomb repulsion. A method is also presented for directing the beams to a target considering the variable terrestrial magnetic field. In another preferred application, the electron beam is directed into the ground to produce a subsurface x-ray source to locate and/or destroy buried or otherwise hidden objects including explosive devices.

  17. Tailored Positron Beams from Trapped Single-component Plasmas

    NASA Astrophysics Data System (ADS)

    Weber, T. R.

    2009-11-01

    There are a number of important uses of antiparticles (e.g., positrons and antiprotons) including the creation of antihydrogen, modeling astrophysical processes, and the characterization of materials and material surfaces. Much of this progress has been driven by the development of new plasma techniques to accumulate, manipulate and store antiparticles. This talk focuses on recent workfootnotetextT. R. Weber, J. R. Danielson and C. M. Surko, Phys. Plasmas 15, 012106 (2008).^,footnotetextT. R. Weber, J. R. Danielson and C. M. Surko, Phys. Plasmas 16, 057105 (2009). to create specially tailored positron beams with small transverse spatial extent ρb, narrow energy spreads δE, and high brightness by pulsed extraction from plasmas in a Penning-Malmberg trap. Experiments are presented using electron plasmas for increased data rate. By briefly lowering the exit-gate potential, beam pulses (δt < 10 μsec) from near the plasma center are created with ρb= 2 λD (HW 1/e) and δE T, where λD is the plasma Debye length, and T is the plasma temperature. Specifically, by tailoring the plasma temperature to T 25 meV and density to n0 10^10 cm-3, beams are created with δE < 35 meV and ρb< 50 μm. A nonlinear model for beam extraction is used to derive expressions for the beam amplitude Nb, transverse spatial profile σb(r), and single particle energy distribution as a function of the exit-gate potential VE, trap wall radius RW, and plasma parameters.^3 All predictions are verified for a wide range of plasmas. Protocols to optimize ρb and δE for various applications will be discussed. Prospects for cryogenic beams and pulsed extraction from the confining B field (to B = 0, for brightness enhancement and electrostatic focusing) will be discussed along with selected applications.

  18. Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Joshi, Chan; Malka, Victor

    2010-04-01

    The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

  19. Dense plasma heating by crossing relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Ratan, N.; Sircombe, N. J.; Ceurvorst, L.; Sadler, J.; Kasim, M. F.; Holloway, J.; Levy, M. C.; Trines, R.; Bingham, R.; Norreys, P. A.

    2017-01-01

    Here we investigate, using relativistic fluid theory and Vlasov-Maxwell simulations, the local heating of a dense plasma by two crossing electron beams. Heating occurs as an instability of the electron beams drives Langmuir waves, which couple nonlinearly into damped ion-acoustic waves. Simulations show a factor 2.8 increase in electron kinetic energy with a coupling efficiency of 18%. Our results support applications to the production of warm dense matter and as a driver for inertial fusion plasmas.

  20. Dense plasma heating by crossing relativistic electron beams.

    PubMed

    Ratan, N; Sircombe, N J; Ceurvorst, L; Sadler, J; Kasim, M F; Holloway, J; Levy, M C; Trines, R; Bingham, R; Norreys, P A

    2017-01-01

    Here we investigate, using relativistic fluid theory and Vlasov-Maxwell simulations, the local heating of a dense plasma by two crossing electron beams. Heating occurs as an instability of the electron beams drives Langmuir waves, which couple nonlinearly into damped ion-acoustic waves. Simulations show a factor 2.8 increase in electron kinetic energy with a coupling efficiency of 18%. Our results support applications to the production of warm dense matter and as a driver for inertial fusion plasmas.

  1. Generation of filamentary structures by beam-plasma interaction

    SciTech Connect

    Wang, X.Y.; Lin, Y.

    2006-05-15

    The previous simulations by Wang and Lin [Phys. Plasmas. 10, 3528 (2003)] showed that filaments, frequently observed in space plasmas, can form via the interaction between an ion beam and a background plasma. In this study, the physical mechanism for the generation of the filaments is investigated by a two-dimensional hybrid simulation, in which a field-aligned ion beam with relative beam density n{sub b}=0.1 and beam velocity V{sub b}=10V{sub A} is initiated in a uniform plasma. Right-hand nonresonant ion beam modes, consistent with the linear theory, are found to be dominant in the linear stage of the beam-plasma interaction. In the later nonlinear stage, the nonresonant modes decay and the resonant modes grow through a nonlinear wave coupling. The interaction among the resonant modes leads to the formation of filamentary structures, which are the field-aligned structures (k perpendicular B) of magnetic field B, density, and temperature in the final stage. The filaments are nonlinearly generated in a prey-predator fashion by the parallel and oblique resonant ion beam modes, which meanwhile evolve into two types of shear Alfven modes, with one mainly propagating along the background field B{sub 0} and the other obliquely propagating. The filamentary structures are found to be phase standing in the plasma frame, but their amplitude oscillates with time. In the dominant filament mode, fluctuations in the background ion density, background ion temperature, and beam density are in phase with the fluctuations in B, whereas the significantly enhanced beam temperature is antiphase with B. It is found that the filaments are produced by the interaction of at least two ion beam modes with comparable amplitudes, not by only one single mode, thus their generation mechanism is different from other mechanisms such as the stimulated excitation by the decay of an Alfven wave.

  2. Reflected beam's direction deviation induced by the corner cube retroreflector

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Xian, Hao; Jang, WenHan

    2008-12-01

    The direction deviation of the reflected beam induced by the corner cube retroreflector (CCR) is respectively discussed by geometrical optics approach and the principle of physical optics in this paper. A mathematical model was built to calculate the beam's aberration due to the fabrication errors of the CCR. It can be concluded that the centroid direction error of far field spot is much more appropriate to describe the reflection beam's direction deviation for a broad incident beam, and the beam with even intensity distribution should be used to reduce its direction deviation.

  3. On the Magnetization of Cosmic Outflows: Plasma Modes and Instabilities of Unmagnetized Plasma Beams

    NASA Astrophysics Data System (ADS)

    Michno, M. J.; Schlickeiser, R.

    2010-05-01

    The dissipation of the kinetic energy of cosmic outflows in interactions with ambient collision-free plasmas and the associated generation of electromagnetic plasma turbulence is a fundamental problem of modern astrophysics. Thermalization by elastic two-body Coulomb collisions is orders of magnitudes too slow as compared to interactions with electric and magnetic fields because of the generally low density of cosmic plasmas. Alternative dissipation mechanisms have to be examined such as energy diffusion by second-order Fermi interactions of charged particles with electromagnetic turbulence, which are an intrinsic property of any sufficiently agitated magnetized plasma. We consider the microphysical details of the energy conversion in relativistic and nonrelativistic outflows by investigating the solutions of the linear plasma dispersion relation in an unmagnetized anisotropic beam plasma consisting of two overall-neutral particle beams propagating with arbitrary velocities in the same direction. The general plasma dispersion relation is derived for arbitrary propagation angle θ with respect to the beam propagation direction both in the initial laboratory frame and in the counterstream frame of reference. Solutions of the linear dispersion relation are derived for parallel (θ = π/2) and perpendicular (θ = 0) propagation angle, respectively. For parallel propagation angles, the electrostatic mode is excited and its maximum growth rate depends on the relative bulk Lorentz factor of the flows and their density ratio. For perpendicular propagation angles, the aperiodic filamentation mode is excited and its maximum growth rate depends differently on the relative bulk Lorentz factor of the flow and their density ratio. The respective maximum growth rates indicate that for nonrelativistic flow velocities the electrostatic instability (EI) is excited much faster than the filamentation instability (FI), whereas for relativistic flow velocities the FI has a larger growth

  4. Nonlinear analysis of a relativistic beam-plasma cyclotron instability

    NASA Technical Reports Server (NTRS)

    Sprangle, P.; Vlahos, L.

    1986-01-01

    A self-consistent set of nonlinear and relativistic wave-particle equations are derived for a magnetized beam-plasma system interacting with electromagnetic cyclotron waves. In particular, the high-frequency cyclotron mode interacting with a streaming and gyrating electron beam within a background plasma is considered in some detail. This interaction mode may possibly find application as a high-power source of coherent short-wavelength radiation for laboratory devices. The background plasma, although passive, plays a central role in this mechanism by modifying the dielectric properties in which the magnetized electron beam propagates. For a particular choice of the transverse beam velocity (i.e., the speed of light divided by the relativistic mass factor), the interaction frequency equals the nonrelativistic electron cyclotron frequency times the relativistic mass factor. For this choice of transverse beam velocity the detrimental effects of a longitudinal beam velocity spread is virtually removed. Power conversion efficiencies in excess of 18 percent are both analytically calculated and obtained through numerical simulations of the wave-particle equations. The quality of the electron beam, degree of energy and pitch angle spread, and its effect on the beam-plasma cyclotron instability is studied.

  5. ECRH microwave beam broadening in the edge turbulent plasma

    SciTech Connect

    Sysoeva, E. V.; Gusakov, E. Z.; Popov, A. Yu.; Silva, F. da; Heuraux, S.

    2014-02-12

    The influence of turbulent plasma density fluctuations on angular and spatial beam width is treated analytically in the framework of WKB based eikonal method. Reasonable agreement of analytical and numerical treatment results is demonstrated within the domain of quasi-optical approximation validity. Significant broadening of microwave beams is predicted for future ECRH experiments at ITER.

  6. Recent observations of beam plasma interactions in the ionosphere and a comparison with laboratory studies of the beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Bernstein, W.; Kellogg, P. J.; Monson, S. J.; Holzworth, R. H.; Whalen, B. A.

    1982-01-01

    Experimental results from an electron beam injection rocket flight (27:010 AE) launched into an active aurora are summarized. The rocket carried an accelerator which injected programmed electron beams of less than 100 ma at 2 and 4 kV into the ionospheric plasma over the altitude range 120-240 km. A major objective of the experiment was the study of beam-plasma interactions and the possible identification of the ignition of the beam-plasma discharge (BPD) which had been intensively studied in the laboratory. A qualitative assessment of the data indicates that BPD ignition was produced by both 10 ma and Im beams at 2 and 4 kV. Many of the observed characteristics are similar to the BPD characteristics observed in the laboratory.

  7. A new criterion to describe crossed-beam energy transfer in laser-plasma interactions

    NASA Astrophysics Data System (ADS)

    Trines, R.; Schmitz, H.; Alves, E. P.; Fiuza, F.; Vieira, J.; Silva, L. O.; Bingham, R.

    2016-10-01

    Crossed-beam energy transfer (CBET) between laser beams in underdense plasma is ubiquitous in both direct-drive and indirect-drive inertial confinement fusion. To understand the impact of this process on the final shape of the laser beams involved, as well as their imprint on either hohlraum walls or target surface, a detailed spatial and temporal description of the crossing beams is needed. We have developed an analytical model and derived new criteria describing both the spatial structure and temporal evolution of the beams after crossing. Numerical simulations have been carried out justifying the analytical model and confirming the criteria. The impact of our results on present and future multi-beam experiments in laser fusion and high-energy-density physics, in particular the ``bursty'' nature of beams predicted to occur in NIF experiments, will be discussed.

  8. Effect of beam emittance on self-modulation of long beams in plasma wakefield accelerators

    SciTech Connect

    Lotov, K. V.

    2015-12-15

    The initial beam emittance determines the maximum wakefield amplitude that can be reached as a result of beam self-modulation in the plasma. The wakefield excited by the fully self-modulated beam decreases linearly with the increase in the beam emittance. There is a value of initial emittance beyond which the self-modulation does not develop even if the instability is initiated by a strong seed perturbation. The emittance scale at which the wakefield is suppressed by a factor of two with respect to the zero-emittance case (the so called critical emittance) is determined by inability of the excited wave to confine beam particles radially and is related to beam and plasma parameters by a simple formula. The effect of beam emittance can be observed in several discussed self-modulation experiments.

  9. Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

    SciTech Connect

    Anders, Andre; Kauffeldt, Marina; Oks, Efim M.; Roy, Prabir K.

    2010-10-30

    Space-charge neutralization is required to compress and focus a pulsed, high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We described approaches to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. Among the options are plasma injection from pulsed vacuum arc sources located outside the solenoid, and using a high current (> 4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means, by an array of movable Langmuir probes, by a small single probe, and by evaluating Stark broadening of the Balmer H beta spectral line. In the main approach described here, the plasma is produced at several cathode spots distributed azimuthally on the ring cathode. It is shown that the plasma is essentially hollow, as determined by the structure of the magnetic field, though the plasma density exceeds 1014 cm-3 in practically all zones of the solenoid volume if the ring electrode is placed a few centimeters off the center of the solenoid. The plasma is non-uniform and fluctuating, however, since its density exceeds the ion beam density it is believed that this approach could provide a practical solution to the space charge neutralization challenge.

  10. Laser-wakefield acceleration of monoenergetic electron beams in the first plasma-wave period.

    PubMed

    Mangles, S P D; Thomas, A G R; Kaluza, M C; Lundh, O; Lindau, F; Persson, A; Tsung, F S; Najmudin, Z; Mori, W B; Wahlström, C-G; Krushelnick, K

    2006-06-02

    Beam profile measurements of laser-wakefield accelerated electron bunches reveal that in the monoenergetic regime the electrons are injected and accelerated at the back of the first period of the plasma wave. With pulse durations ctau >or= lambda(p), we observe an elliptical beam profile with the axis of the ellipse parallel to the axis of the laser polarization. This increase in divergence in the laser polarization direction indicates that the electrons are accelerated within the laser pulse. Reducing the plasma density (decreasing ctau/lambda(p)) leads to a beam profile with less ellipticity, implying that the self-injection occurs at the rear of the first period of the plasma wave. This also demonstrates that the electron bunches are less than a plasma wavelength long, i.e., have a duration <25 fs. This interpretation is supported by 3D particle-in-cell simulations.

  11. Direct Acceleration of Electrons in a Corrugated Plasma Channel

    SciTech Connect

    Palastro, J. P.; Antonsen, T. M.; Morshed, S.; York, A. G.; Layer, B.; Aubuchon, M.; Milchberg, H. M.; Froula, D. H.

    2009-01-22

    Direct laser acceleration of electrons provides a low power tabletop alternative to laser wakefield accelerators. Until recently, however, direct acceleration has been limited by diffraction, phase matching, and material damage thresholds. The development of the corrugated plasma channel [B. Layer et al., Phys. Rev. Lett. 99, 035001 (2007)] has removed all of these limitations and promises to allow direct acceleration of electrons over many centimeters at high gradients using femtosecond lasers [A. G. York et al., Phys Rev. Lett 100, 195001 (2008), J. P. Palastro et al., Phys. Rev. E 77, 036405 (2008)]. We present a simple analytic model of laser propagation in a corrugated plasma channel and examine the laser-electron beam interaction. Simulations show accelerating gradients of several hundred MeV/cm for laser powers much lower than required by standard laser wakefield schemes. In addition, the laser provides a transverse force that confines the high energy electrons on axis, while expelling low energy electrons.

  12. THz generation by self-focusing of hollow Gaussian laser beam in magnetised plasma

    NASA Astrophysics Data System (ADS)

    Hussain, Saba; Singh, Monika; Kishor Singh, Ram; Sharma, R. P.

    2014-09-01

    A scheme of terahertz (THz) generation is proposed by the self-focusing of a high-power laser beam having hollow Gaussian intensity profile in a collissionless magnetized plasma, where ponderomotive nonlinearity is operative. THz waves are resonantly excited at the difference frequency of laser and electron plasma wave (EPW) satisfying the proper phase matching conditions. In this paper first we have investigated the filamentation of the circularly polarized hollow Gaussian beam (HGB) propagating parallel to the direction of a static background magnetic field within the paraxial approximation, subsequently this filamented HG laser beam interplay with the electron plasma wave to generate a nonlinear current in the transverse direction, thereby producing THz radiations. The intensity of the emitted radiations are found to be highly sensitive to the order of the HGB. For the current scheme the power level of THz wave comes out to be ˜ 0.05 gigawatts.

  13. Beam acceleration by plasma-loaded free-electron devices

    NASA Astrophysics Data System (ADS)

    Tsui, K. H.; Serbeto, A.; D'olival, J. B.

    1998-01-01

    The use of a plasma-filled wiggler free-electron laser device operating near the plasma cutoff to accelerate electron beams is examined. Near the cutoff, the group velocity of the microwave field in the plasma is much less than the beam velocity. This scheme, therefore, operates in the pulse mode to accelerate electron beam bunches much shorter than the wiggler length. Between one bunch and the other, the wiggler is reloaded with microwave field. During the loading period, the laser-wiggler-plasma (SWL) Raman interaction generates a Langmuir mode with the laser and the wiggler as the primary energy sources. When the wiggler plasma is fully loaded with microwave field, a short electron bunch is fired into the device. In this accelerating period, the Langmuir mode is coupled to the laser-wiggler-beam (SWB) free-electron-laser interaction. The condition that the Langmuir phase velocity matches the free-electron-laser resonant beam velocity assures the simultaneous interaction of the SWL and SWB parametric processes. Beam acceleration is accomplished fundamentally via the space charge field of the Langmuir mode and the electron phase in the ponderomotive potential. Linear energy gain regime is accomplished when the phase velocity of the Langmuir mode is exactly equal to the speed of light.

  14. RF wave observations in beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Bernstein, W.

    1986-01-01

    The Beam Plasma Discharge (BPD) was produced in the large vacuum chamber at Johnson Space Center (20 x 30 m) using an energetic electron beam of moderately high perveance. A more complete expression of the threshold current I sub c taking into account the pitch angle injection dependence is given. Ambient plasma density inferred from wave measurements under various beam conditions are reported. Maximum frequency of the excited RF band behaves differently than the frequency of the peak amplitude. The latter shows signs of parabolic saturation consistent with the light data. Beam plasma state (pre-BPD or BPD) does not affect the pitch angle dependence. Unexpected strong modulation of the RF spectrum at half odd integer of the electron cyclotron frequency (n + 1/2)f sub ce is reported (5 n 10). Another new feature, the presence of wave emission around 3/2 f sub ce for I sub b is approximate I sub c is reported.

  15. Collaborative Research: Instability and transport of laser beam in plasma

    SciTech Connect

    Rose, Harvey Arnold; Lushnikov, Pavel

    2014-11-18

    Our goal was to determine the onset of laser light scattering due to plasma wave instabilities. Such scatter is usually regarded as deleterious since laser beam strength is thereby diminished. While this kind of laser-plasma-instability (LPI) has long been understood for the case of coherent laser light, the theory of LPI onset for a laser beam with degraded coherence is recent. Such a laser beam fills plasma with a mottled intensity distribution, which has large fluctuations. The key question is: do the exceptionally large fluctuations control LPI onset or is it controlled by the relatively quiescent background laser intensity? We have answered this question. This is significant because LPI onset power in the former case is typically small compared to that of the latter. In addition, if large laser intensity fluctuations control LPI onset, then nonlinear effects become significant for less powerful laser beams than otherwise estimated.

  16. Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

    SciTech Connect

    Singh, N.; Conrad, J.R.; Schunk, R.W.

    1985-06-01

    It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves. 39 references.

  17. Electrostatic ion cyclotron, beam-plasma, and lower hybrid waves excited by an electron beam

    NASA Technical Reports Server (NTRS)

    Singh, N.; Conrad, J. R.; Schunk, R. W.

    1985-01-01

    It is pointed out that electrostatic ion cyclotron (EIC) waves have been extensively investigated in connection with both space and laboratory plasmas. The present investigation has the objective to study the excitation of low-frequency waves in a multiion plasma by electron beams. The frequencies considered range from below the lowest gyrofrequency of the heaviest ion to about the lower hybrid frequency. It is shown that electron-beam instabilities can produce peaks in the growth rate below the cyclotron frequency of each ion species if nonzero perpendicular wave number effects are included in the ion dynamics. The dispersion relations for neutralized ion Bernstein (NIB) and pure ion Bernstein (PIB) waves are considered along with an instability analysis for a cold plasma and warm electron beam, the electron beam-plasma mode, banded ion cyclotron (EIC) waves with small perpendicular wavelengths, and the growth lengths of the waves.

  18. Ignition of beam plasma discharge in the electron beam experiment in space

    NASA Technical Reports Server (NTRS)

    Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Roberts, W. T.; Taylor, W. W. L.

    1985-01-01

    An ignition of beam plasma discharge (BPD) in space was observed in a neutral gas-electron beam interaction experiment by Space Shuttle/Spacelab-1 in 1983. An electron beam of 8 kV 100 mA was injected into a high dense nitrogen gas cloud of 10 to the 23rd molecules which was released during 100 msec from the Orbiter. The appearance of the beam and its surroundings observed by a low-light-level TV camera showed a local ignition of the beam plasma discharge in the gas cloud. The enhanced plasma production, generation of auroral emission, and associated wave emission were also detected by onboard diagnostic instruments.

  19. Toroidal midplane neutral beam armor and plasma limiter

    DOEpatents

    Kugel, Henry W.; Hand Jr, Samuel W.; Ksayian, Haig

    1986-02-04

    For use in a tokamak fusion reactor having a midplane magnetic coil on the inner wall of an evacuated toriodal chamber within which a neutral beam heated, fusing plasma is magnetically confined, a neutral beam armor shield and plasma limiter is provided on the inner wall of the toroidal chamber to shield the midplane coil from neutral beam shine-thru and plasma deposition. The armor shield/plasma limiter forms a semicircular enclosure around the midplane coil with the outer surface of the armor shield/plasma limiter shaped to match, as closely as practical, the inner limiting magnetic flux surface of the toroidally confined, indented, bean-shaped plasma. The armor shield/plasma limiter includes a plurality of semicircular graphite plates each having a pair of coupled upper and lower sections with each plate positioned in intimate contact with an adjacent plate on each side thereof so as to form a closed, planar structure around the entire outer periphery of the circular midplane coil. The upper and lower plate sections are adapted for coupling to heat sensing thermocouples and to a circulating water conduit system for cooling the armor shield/plasma limiter.The inner center portion of each graphite plate is adapted to receive and enclose a section of a circular diagnostic magnetic flux loop so as to minimize the power from the plasma confinement chamber incident upon the flux loop.

  20. Toroidal midplane neutral beam armor and plasma limiter

    DOEpatents

    Kugel, Henry W.; Hand, Jr, Samuel W.; Ksayian, Haig

    1986-01-01

    For use in a tokamak fusion reactor having a midplane magnetic coil on the inner wall of an evacuated toriodal chamber within which a neutral beam heated, fusing plasma is magnetically confined, a neutral beam armor shield and plasma limiter is provided on the inner wall of the toroidal chamber to shield the midplane coil from neutral beam shine-thru and plasma deposition. The armor shield/plasma limiter forms a semicircular enclosure around the midplane coil with the outer surface of the armor shield/plasma limiter shaped to match, as closely as practical, the inner limiting magnetic flux surface of the toroidally confined, indented, bean-shaped plasma. The armor shield/plasma limiter includes a plurality of semicircular graphite plates each having a pair of coupled upper and lower sections with each plate positioned in intimate contact with an adjacent plate on each side thereof so as to form a closed, planar structure around the entire outer periphery of the circular midplane coil. The upper and lower plate sections are adapted for coupling to heat sensing thermocouples and to a circulating water conduit system for cooling the armor shield/plasma limiter.The inner center portion of each graphite plate is adapted to receive and enclose a section of a circular diagnostic magnetic flux loop so as to minimize the power from the plasma confinement chamber incident upon the flux loop.

  1. Theory of a beam-driven plasma antenna

    NASA Astrophysics Data System (ADS)

    Timofeev, I. V.; Volchok, E. P.; Annenkov, V. V.

    2016-08-01

    In this paper, we propose a theory describing generation of electromagnetic waves in a thin beam-plasma system with a characteristic transverse size comparable with the radiation wavelength. In fact, a thin plasma column with a longitudinal density modulation works like a plasma antenna in which an electron beam can excite a superluminal wave of electric current. It has previously been shown that, if the period of this modulation coincides with the wavelength of the most unstable beam-driven mode, radiation at a frequency slightly below the plasma frequency is emitted transversely to the plasma column and generated in thin boundary layers. For the plasma thickness comparable with the skin-depth, generation of the terahertz radiation can reach high efficiency ( ˜10 % ) in such a scheme, but the absolute power of this radiation cannot be increased by increasing the transverse plasma size. In this paper, we study whether the power of such an antenna can be increased in the regime of oblique emission when the magnetized plasma is transparent to the radiated electromagnetic waves and the whole plasma volume may be involved in their generation.

  2. Laser beam propagation through inertial confinement fusion hohlraum plasmas

    SciTech Connect

    Froula, D. H.; Divol, L.; Meezan, N. B.; Dixit, S.; Neumayer, P.; Moody, J. D.; Pollock, B. B.; Ross, J. S.; Suter, L.; Glenzer, S. H.

    2007-05-15

    A study of the laser-plasma interaction processes have been performed in plasmas that are created to emulate the plasma conditions in indirect drive inertial confinement fusion targets. The plasma emulator is produced in a gas-filled hohlraum; a blue 351-nm laser beam propagates along the axis of the hohlraum interacting with a high-temperature (T{sub e}=3.5 keV), dense (n{sub e}=5x10{sup 20} cm{sup -3}), long-scale length (L{approx}2 mm) plasma. Experiments at these conditions have demonstrated that the interaction beam produces less than 1% total backscatter resulting in transmission greater than 90% for laser intensities less than I<2x10{sup 15} W cm{sup -2}. The bulk plasma conditions have been independently characterized using Thomson scattering where the peak electron temperatures are shown to scale with the hohlraum heater beam energy in the range from 2 keV to 3.5 keV. This feature has allowed us to determine the thresholds for both backscattering and filamentation instabilities; the former measured with absolutely calibrated full aperture backscatter and near backscatter diagnostics and the latter with a transmitted beam diagnostics. Comparing the experimental results with detailed gain calculations for the onset of significant laser scattering processes shows a stimulated Brillouin scattering threshold (R=10%) for a linear gain of 15; these high temperature, low density experiments produce plasma conditions comparable to those along the outer beams in ignition hohlraum designs. By increasing the gas fill density (n{sub e}=10{sup 21} cm{sup -3}) in these targets, the inner beam ignition hohlraum conditions are accessed. In this case, stimulated Raman scattering dominates the backscattering processes and we show that scattering is small for gains less than 20 which can be achieved through proper choice of the laser beam intensity.

  3. GeV electron acceleration by a Gaussian field laser with effect of beam width parameter in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Ghotra, Harjit Singh; Kant, Niti

    2017-01-01

    Electron acceleration due to a circularly polarized (CP) Gaussian laser field has been investigated theoretically in magnetized plasma. A Gaussian laser beam possesses trapping forces on electrons during its propagation through plasma. A single particle simulation indicates a resonant enhancement of electron acceleration with a Gaussian laser beam. The plasma is magnetized with an axial magnetic field in same direction as that of laser beam propagation. The dependence of laser beam width parameter on electron energy gain with propagation distance has been presented graphically for different values of laser intensity. Electron energy gain is relatively high where the laser beam parameter is at its minimum value. Enhanced energy gain of the order of GeV is reported with magnetic field under 20 MG in plasma. It is also seen that the axial magnetic field maintains the electron acceleration for large propagation distance even with an increasing beam width parameter.

  4. Laser-Plasma Interactions in NIF Direct-Drive-Scale Plasmas

    NASA Astrophysics Data System (ADS)

    Regan, S. P.

    1998-11-01

    Laser-plasma interactions have been carried out on OMEGA under plasma conditions representative of the peak of the NIF direct-drive laser pulse. This pulse, for a 1.5 MJ, α = 3 design, has a peak intensity of 2 × 10^15 W/cm^2 (summed over all beams) and a foot intensity of 4 × 10^13 W/cm^2. The coronal plasmas predicted for these implosions have Te ~ 4 keV and a ~1-mm density scale length at the peak of the laser pulse, and Te ~ 600 eV and a ~0.25-mm density scale length during the foot. In the OMEGA experiments, exploding foil plasmas with a maximum on-axis density of n_c/5 have been produced by irradiating mass-limited, 18- to 20-μm-thick CH foils on both sides with a total of 20 kJ of laser energy from 38 beams. In addition, NIF direct-drive scale plasmas including a critical density have been created by irradiating solid CH targets on one side with 10 kJ of laser energy from 19 beams. All of the experiments were carried out with distributed phase plates (DPP's) and 2-D SSD ( ~0.25 THz). The electron temperature and density of exploding-foil plasmas have been diagnosed using time-resolved x-ray spectroscopy and stimulated Raman scattering (SRS) measurements and are consistent with SAGE code predictions. Temperatures increasing with time up to 4 keV have been found. When these plasmas were irradiated with our interaction beam at ~1.5 × 10^15 W/cm^2, stimulated Brillouin backscattering (SBS) was found to be completely inhibited when DPP's were used. Without a DPP in the interaction beam, the SBS reflectivity can exceed 10%. Future experiments on OMEGA will address the parametric instabilities of the coronal plasmas in the foot and transition regions of the NIF laser pulse. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460. *In collaboration with D.K. Bradley^a, J.J. Carroll III^b, A.V. Chirokikh^a, R.S. Craxton^a, R.P. Drake^b, D.D. Meyerhofer^a, W. Seka^a, R

  5. Electron beam driven lower hybrid waves in a dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri; Sharma, Suresh C.; Gupta, Ruby

    2013-05-15

    An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed.

  6. Beam-plasma interactions in a positive ion-negative ion plasma

    NASA Technical Reports Server (NTRS)

    Intrator, T.; Hershkowitz, N.; Stern, R.

    1983-01-01

    An electron-free plasma consisting of negative ions /SF6(-)/ and positive ions /Ar(+)/, and negligible neutral-ion collision frequencies has been created in the laboratory. This plasma has a mass ratio of approximately 3.5-similar to many computer particle-in-cell simulated systems. A fluid description of this positive and negative ion confinement (PANIC) plasma is given and compared to experimental measurements of a beam-plasma instability for both beam species and a wide range of beam energies. The fluid dispersion relation and most growing modes are predicted to be insensitive to many parameters of the PANIC beam-plasma system, and found to the consistent with the data.

  7. Parameters of the beam plasma formed by a forevacuum plasma source of a ribbon beam in zero-field transportation system

    NASA Astrophysics Data System (ADS)

    Klimov, A. S.; Lomaev, M. I.; Oks, E. M.; Andreichik, A. P.

    2017-02-01

    We have studied the generation of the beam plasma formed by a forevacuum plasma source of a ribbon electron beam in the conditions of its transportation without an accompanying magnetic field. The ignition conditions in the beam transportation region of the beam-plasma discharge producing a plasma formation of the plasma sheet type with a plasma concentration of 1016 m-3 and an electron temperature of 1-2.5 eV have been determined. The attained values of parameters and the sizes of the plasma formation make it possible to use it in technologies of the surface modification of planar extended articles.

  8. Halo Formation And Emittance Growth of Positron Beams in Plasmas

    SciTech Connect

    Muggli, P.; Blue, B.E.; Clayton, C.E.; Decker, F.J.; Hogan, M.J.; Huang, C.; Joshi, C.; Katsouleas, Thomas C.; Lu, W.; Mori, W.B.; O'Connell, C.L.; Siemann, R.H.; Walz, D.; Zhou, M.; /UCLA

    2011-10-25

    An ultrarelativistic 28.5 GeV, 700-{micro}m-long positron bunch is focused near the entrance of a 1.4-m-long plasma with a density n{sub e} between {approx}10{sup 13} and {approx}5 x 10{sup 14} cm{sup -3}. Partial neutralization of the bunch space charge by the mobile plasma electrons results in a reduction in transverse size by a factor of {approx}3 in the high emittance plane of the beam {approx}1 m downstream from the plasma exit. As n{sub e} increases, the formation of a beam halo containing {approx}40% of the total charge is observed, indicating that the plasma focusing force is nonlinear. Numerical simulations confirm these observations. The bunch with an incoming transverse size ratio of {approx}3 and emittance ratio of {approx}5 suffers emittance growth and exits the plasma with approximately equal sizes and emittances.

  9. Studies on Neutral Beam Injection into the SSPX Spheromak Plasma

    SciTech Connect

    Jayakumar, R; Pearlstein, L D; Casper, T A; Fowler, T K; Hill, D N; Hudson, B; McLean, H; Moller, J

    2007-10-19

    In the Sustained Spheromak Physics Experiment, (SSPX) ['Improved operation of the SSPX spheromak', R.D. Wood, D.N. Hill, E.B. Hooper, S. Woodruff1, H.S. McLean and B.W. Stallard, Nucl. Fusion 45 1582-1588 (2005)], plasmas with core electron temperatures reaching up to 500 eV at densities of 10{sup 20}/m{sup 3} have been sustained for several milliseconds, making them suitable as targets for neutral beam injection. High performance and further progress in understanding Spheromak plasma physics are expected if neutral beams are injected into the plasma. This paper presents the results of numerical 1.5 D modeling of the plasma to calculate neutral beam current drive and ion and electron heating. The results are presented for varying initial conditions of density, temperatures and profiles and beam energy, injection angle and power. Current drive efficiency (Ampere/Watt of absorbed power) of up to 0.08 can be achieved with best performance SSPX shots as target. Analyses of neutral beam heating indicate that ion temperatures of up to 1.5 keV and electron temperatures of up to 750 eV can be obtained with injection of about 1 MW of neutral beam for 5-10 ms and with diffusivities typically observed in SSPX. Injection targeting near the magnetic axis appears to be the best for heating and current drive. Effect of the current drive and evolution of SSPX equilibrium are discussed.

  10. Simulations of the effects of mobile ions on the relativistic beam-plasma instability for intense beams

    SciTech Connect

    Jones, M.E.; Lemons, D.S.; Lee, H.

    1983-01-01

    Particle-in-cell simulations of the beam-plasma instability for intense relativistic electron beams in dense plasmas show rapid heating of the electrons to multi-kilovolt temperatures. The resulting hydrodynamic motion of the plasma results in density gradients that degrade the interaction. Heat flow out of the plasma is found in some instances to limit the gradient formation process.

  11. Dynamics of ion beam charge neutralization by ferroelectric plasma sources

    SciTech Connect

    Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C.

    2016-04-27

    Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established similar to –5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-mu s surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of mu s after the high voltage pulse is applied. Lastly, it is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.

  12. Dynamics of ion beam charge neutralization by ferroelectric plasma sources

    DOE PAGES

    Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; ...

    2016-04-27

    Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3 V,more » implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established similar to –5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-mu s surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of mu s after the high voltage pulse is applied. Lastly, it is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.« less

  13. Electron Beam Transport in Advanced Plasma Wave Accelerators

    SciTech Connect

    Williams, Ronald L

    2013-01-31

    The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams were generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.

  14. Cylindrical plasmas generated by an annular beam of ultraviolet light

    SciTech Connect

    Thomas, D. M.; Allen, J. E.

    2015-07-15

    We investigate a cylindrical plasma system with ionization, by an annular beam of ultraviolet light, taking place only in the cylinder's outer region. In the steady state, both the outer and inner regions contain a plasma, with that in the inner region being uniform and field-free. At the interface between the two regions, there is an infinitesimal jump in ion density, the magnitude approaching zero in the quasi-neutral (λ{sub D} → 0) limit. The system offers the possibility of producing a uniform stationary plasma in the laboratory, hitherto obtained only with thermally produced alkali plasmas.

  15. Resonant excitation of waves by a spiraling ion beam on the large plasma device

    NASA Astrophysics Data System (ADS)

    Tripathi, Shreekrishna

    2015-11-01

    The resonant interaction between energetic-ions and plasma waves is a fundamental topic of importance in the space, controlled magnetic-fusion, and laboratory plasma physics. We report new results on the spontaneous generation of traveling shear Alfvén waves and high-harmonic beam-modes in the lower-hybrid range of frequencies by an intense ion beam. In particular, the role of Landau and Doppler-shifted ion-cyclotron resonances (DICR) in extracting the free-energy from the ion-beam and destabilizing Alfvén waves was explored on the Large Plasma Device (LAPD). In these experiments, single and dual-species magnetized plasmas (n ~1010 -1012 cm-3, Te ~ 5.0-10.0 eV, B = 0.6-1.8 kG, He+ and H+ ions, 19.0 m long, 0.6 m diameter) were produced and a spiraling hydrogen ion beam (5-15 keV, 2-10 A, beam-speed/Alfvén-speed = 0.2-1.5, J ~ 50-150 mA/cm2, pitch-angle ~53°) was injected into the plasma. The interaction of the beam with the plasma was diagnosed using a retarding-field energy analyzer, three-axis magnetic-loop, and Langmuir probes. The resonance conditions for the growth of shear Alfvén waves were examined by varying the parameters of the ion-beam and ambient plasma. The experimental results demonstrate that the DICR process is particularly effective in exciting left-handed polarized shear Alfvén waves that propagate in the direction opposite to the ion beam. The high-harmonic beam modes were detected in the vicinity of the spiraling ion beam and contained more than 80 harmonics of Doppler-shifted gyro-frequency of the beam. Work jointly supported by US DOE and NSF and performed at the Basic Plasma Science Facility, UCLA.

  16. Staging Laser Plasma Accelerators for Increased Beam Energy

    SciTech Connect

    Panasenko, D.; Shu, A. J.; Schroeder, C. B.; Gonsalves, A. J.; Nakamura, K.; Matlis, N. H.; Cormier-Michel, E.; Plateau, G.; Lin, C.; Toth, C.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

    2009-01-22

    Staging laser plasma accelerators is an efficient way of mitigating laser pump depletion in laser driven accelerators and necessary for reaching high energies with compact laser systems. The concept of staging includes coupling of additional laser energy and transporting the electron beam from one accelerating module to another. Due to laser damage threshold constraints, in-coupling laser energy with conventional optics requires distances between the accelerating modules of the order of 10 m, resulting in decreased average accelerating gradient and complicated e-beam transport. In this paper we use basic scaling laws to show that the total length of future laser plasma accelerators will be determined by staging technology. We also propose using a liquid jet plasma mirror for in-coupling the laser beam and show that it has the potential to reduce distance between stages to the cm-scale.

  17. Strongly turbulent stabilization of electron beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Haber, I.; Palmadesso, P.; Papadopoulos, K.

    1980-01-01

    The stabilization of electron beam interactions due to strongly turbulent nonlinearities is studied analytically and numerically for a wide range of plasma parameters. A fluid mode coupling code is described in which the effects of electron and ion Landau damping and linear growth due to the energetic electron beam are included in a phenomenological manner. Stabilization of the instability is found to occur when the amplitudes of the unstable modes exceed the threshold of the oscillating two-stream instability. The coordinate space structure of the turbulent spectrum which results clearly shows that soliton-like structures are formed by this process. Phenomenological models of both the initial stabilization and the asymptotic states are developed. Scaling laws between the beam-plasma growth rate and the fluctuations in the fields and plasma density are found in both cases, and shown to be in good agreement with the results of the simulation.

  18. Acceleration of electrons in strong beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1984-01-01

    The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

  19. Ideal Laser Beam Propagation through high temperature ignition hohlraum plasmas

    SciTech Connect

    Froula, D H; Divol, L; Meezan, N; Dixit, S; Moody, J D; Pollock, B B; Ross, J S; Glenzer, S H

    2006-09-20

    We demonstrate that a blue (3{omega}, 351 nm) laser beam with an intensity of 2 x 10{sup 15} W-cm{sup -2} propagates within the original beam cone through a 2-mm long, T{sub e}=3.5 keV high density (n{sub e} = 5 x 10{sup 20} cm{sup -3}) plasma. The beam produced less than 1% total backscatter; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds.

  20. Neutralization of beam-emitting spacecraft by plasma injection

    NASA Technical Reports Server (NTRS)

    Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.

    1987-01-01

    An impulsive plasma injection has been used to study charge neutralization of the Space Shuttle Orbiter while it was emitting an electron beam into space. This investigation was performed by Space Experiments with Particle Accelerators on Spacelab-1. A plasma consisting of 10 to the 19th argon ion-electron pairs was injected into space for 1 ms while an electron beam was also being emitted into space. The electron beam energy and current were as high as 5 keV and 300 mA. While the orbiter potential was positive before the plasma injection and began to decrease during the plasma injection, it was near zero for 6 to 20 ms after the plasma injection. The recovery time to the initial level of charging varied from 10 to 100 ms. In a laboratory test in a large space chamber using the same flight hardware, the neutralization time was 8-17 ms and the recovery time was 11-20 ms. The long duration of the neutralization effect in space can be explained by a model of diffusion of the cold plasma which is produced near the Orbiter by charge exchange between the neutral argon atoms and the energetic argon ions during plasma injection.

  1. Strong terahertz radiation generation by beating of two spatial-triangular beams in collisional magnetized plasma

    NASA Astrophysics Data System (ADS)

    Hematizadeh, Ayoob; Bakhtiari, Farhad; Jazayeri, Seyed Masud; Ghafary, Bijan

    2016-05-01

    A scheme of terahertz (THz) radiation generation is proposed by beating of two spatial-triangular laser beams in plasma with a spatially periodic density when electron-neutral collisions have taken into account. In this process, the laser beams exert a ponderomotive force on the electrons of the plasma and impart the oscillatory velocity at the difference frequency in the presence of a static magnetic field which is applied parallel to the direction of the lasers. We show that higher efficiency and stronger THz radiation are achieved when the parallel magnetic field is used to compare the perpendicular magnetic field. The effects of beam width of lasers, collision frequency, periodicity of density ripples, and magnetic field strength are analyzed for strong THz radiation generation. The THz field of the emitted radiations is found to be highly sensitive to collision frequency and magnetic field strength. In this scheme with the optimization of plasma parameters, the efficiency of order 21% is achieved.

  2. Modulation of continuous electron beams in plasma wake-fields

    SciTech Connect

    Rosenzweig, J.B.

    1988-09-08

    In this paper we discuss the interaction of a continuous electron beam with wake-field generated plasma waves. Using a one-dimensional two fluid model, a fully nonlinear analytical description of the interaction is obtained. The phenomena of continuous beam modulation and wave period shortening are discussed. The relationship between these effects and the two-stream instability is also examined. 12 refs., 1 fig.

  3. Population Inversions in Ablation Plasmas Generated by Intense Electron Beams.

    DTIC Science & Technology

    1988-11-01

    light weight design, and moderate cost. The Soviets have investigated intense proton beam pumped plasma lasers , however, the University of Michigan...interpretations have been verified by moving the position of the probe laser beam away from the surface of the anode (from 0.1 cm to 0.4 cm) and noting the changes...Properties Effects on Ultraviolet Laser induced Flashover of Angled Plastic insulators in Vacuum", C.L. Ensloe and R. M. Gilgenbach, IEEE 3 Trans. on

  4. Electron beam injection experiments - Replication of flight observations in a laboratory beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Bernstein, W.; Mcgarity, J. O.; Konradi, A.

    1983-01-01

    Recent electron beam injection experiments in the lower ionosphere have produced two perplexing results: (1) At altitudes from 140 km to 220 km, the beam associated 391.4 nm intensity is relatively independent of altitude despite the decreasing N2 abundance. (2) The radial extent of the perturbed region populated by beam associated energetic electrons significantly exceeds the nominal gyrodiameter for 90 deg injection. A series of laboratory measurements is described in which both of these flight results appear to have been closely reproduced. The laboratory results are reasonably consistent with the transition from a collision dominated to collisionless beam-plasma discharge configuration.

  5. Plasma heating, plasma flow and wave production around an electron beam injected into the ionosphere

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Erickson, K. N.

    1986-01-01

    A brief historical summary of the Minnesota ECHO series and other relevant electron beam experiments is given. The primary purpose of the ECHO experiments is the use of conjugate echoes as probes of the magnetosphere, but beam-plasma and wave studies were also made. The measurement of quasi-dc electric fields and ion streaming during the ECHO 6 experiment has given a pattern for the plasma flow in the hot plasma region extending to 60m radius about the ECHO 6 electron beam. The sheath and potential well caused by ion orbits is discussed with the aid of a model which fits the observations. ELF wave production in the plasma sheath around the beam is briefly discussed. The new ECHO 7 mission to be launched from the Poker Flat range in November 1987 is described.

  6. 3-D Simulations of Plasma Wakefield Acceleration with Non-Idealized Plasmas and Beams

    SciTech Connect

    Deng, S.; Katsouleas, T.; Lee, S.; Muggli, P.; Mori, W.B.; Hemker, R.; Ren, C.; Huang, C.; Dodd, E.; Blue, B.E.; Clayton, C.E.; Joshi, C.; Wang, S.; Decker, F.J.; Hogan, M.J.; Iverson, R.H.; O'Connell, C.; Raimondi, P.; Walz, D.; /SLAC

    2005-09-27

    3-D Particle-in-cell OSIRIS simulations of the current E-162 Plasma Wakefield Accelerator Experiment are presented in which a number of non-ideal conditions are modeled simultaneously. These include tilts on the beam in both planes, asymmetric beam emittance, beam energy spread and plasma inhomogeneities both longitudinally and transverse to the beam axis. The relative importance of the non-ideal conditions is discussed and a worst case estimate of the effect of these on energy gain is obtained. The simulation output is then propagated through the downstream optics, drift spaces and apertures leading to the experimental diagnostics to provide insight into the differences between actual beam conditions and what is measured. The work represents a milestone in the level of detail of simulation comparisons to plasma experiments.

  7. ECR plasma source for heavy ion beam charge neutralization

    SciTech Connect

    Efthimion, P.C.; Gilson, E.; Grisham, L.; Kolchin, P.; Davidson, E.C.; Yu, S.S.; Logan, B.G.

    2002-05-01

    Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length {approx} 0.1-2 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1-10 gauss. The goal is to operate the source at pressures {approx} 10{sup -6} Torr at full ionization. The initial operation of the source has been at pressures of 10{sup -4}-10{sup -1} Torr. Electron densities in the range of 10{sup 8}-10{sup 11} cm{sup -3} have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. To further improve breakdown at low pressure, a weak electron source will be placed near the end of the ECR source.

  8. Delay time for the onset of beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Parish, J. L.; Denig, W. F.; Raitt, W. J.

    1987-01-01

    The interaction of a nonrelativistic electron beam with a neutral gas in a large chamber is considered, and the time interval before ignition of beam plasma discharge (BPD) is studied. A new theoretical expression for the time delay before BPD ignition is found as a function of the critical current necessary for BPD to be established. There are two parameters in the theoretical expression, and both are derived from two different experiments. These parameters are used to write the time evolution equation for plasma density as a function of time.

  9. Harmonic generation by circularly polarized laser beams propagating in plasma

    SciTech Connect

    Agrawal, Ekta; Hemlata,; Jha, Pallavi

    2015-04-15

    An analytical theory is developed for studying the phenomenon of generation of harmonics by the propagation of an obliquely incident, circularly polarized laser beam in homogeneous, underdense plasma. The amplitudes of second and third harmonic radiation as well as detuning distance have been obtained and their variation with the angle of incidence is analyzed. The amplitude of harmonic radiation increases with the angle of incidence while the detuning distance decreases, for a given plasma electron density. It is observed that the generated second and third harmonic radiation is linearly and elliptically polarized, respectively. The harmonic radiation vanishes at normal incidence of the circularly polarized laser beam.

  10. MHD Induced Neutral Beam Ion Loss from NSTX Plasmas

    SciTech Connect

    D.S. Darrow, E.D. Fredrickson, N.N. Gorelenkov, A.L. Roquemore, and K. Shinohara

    2007-12-13

    Bursts of ~60 kHz activity on Mirnov coils occur frequently in NSTX plasmas and these are accompanied by bursts of neutral beam ion loss over a range in pitch angles. These losses have been measured with a scintillator type loss probe imaged with a high speed (>10,000 frames/s) video camera, giving the evolution of the energy and pitch angle distributions of the lost neutral beam ions over the course of the events. The instability occurs below the TAE frequency in NSTX (~100 kHz) in high beta plasmas and may be a beta driven Alfvén acoustic (BAAE) mode.

  11. Device and method for relativistic electron beam heating of a high-density plasma to drive fast liners

    DOEpatents

    Thode, Lester E.

    1981-01-01

    A device and method for relativistic electron beam heating of a high-density plasma in a small localized region. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target gas is ionized prior to application of the electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy and momentum into a small localized region of the high-density plasma target. Fast liners disposed in the high-density target plasma are explosively or ablatively driven to implosion by a heated annular plasma surrounding the fast liner which is generated by an annular relativistic electron beam. An azimuthal magnetic field produced by axial current flow in the annular plasma, causes the energy in the heated annular plasma to converge on the fast liner.

  12. Plasma chemistry in electron-beam sustained discharges

    NASA Astrophysics Data System (ADS)

    Turner, Miles

    2016-09-01

    There are many emerging applications that exploit the exotic chemical characteristics of plasmas. Some of these applications, if deployed on an industrial scale, involve processing much larger volumes of gas than seems reasonable using any atmospheric pressure plasma source in wide use today. We note that an electron-beam sustained discharge permits the creation of a atmospheric pressure plasma with reasonable uniformity, large volme, and widely controllable electron temperature. Robust and durable electron beam sources now exist that would facilitate such applications. In this paper we discuss the general advantages of this approach, and we present a modelling study concerned with the production of NO in mixtures of N2 and O2, looking towards plasma aided manufacturing of fertilizers.

  13. Beam-driven acceleration in ultra-dense plasma media

    SciTech Connect

    Shin, Young-Min

    2014-09-15

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10{sup 25 }m{sup −3} and 1.6 × 10{sup 28 }m{sup −3} plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers ∼20% higher acceleration gradient by enlarging the channel radius (r) from 0.2 λ{sub p} to 0.6 λ{sub p} in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g., nanotubes) of high electron plasma density.

  14. Beam-driven acceleration in ultra-dense plasma media

    SciTech Connect

    Shin, Young-Min

    2014-09-15

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 1025 m-3 and 1.6 x 1028 m-3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlarging the channel radius (r) from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.

  15. Beam-driven acceleration in ultra-dense plasma media

    DOE PAGES

    Shin, Young-Min

    2014-09-15

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 1025 m-3 and 1.6 x 1028 m-3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlarging the channel radius (r)more » from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.« less

  16. High power, fast, microwave components based on beam generated plasmas

    NASA Astrophysics Data System (ADS)

    Manheimer, W. M.; Fernsler, R. F.; Gitlin, M. S.

    1998-10-01

    It is shown that the agile mirror plasma, under development as a device to simply and cheaply give electronic steering to microwave beams, also has application as a fast, electronically controlled, high power reflector, or phase shifter. In a radar system, this can lead to such applications as pulse to pulse polarization agility and electronic control of antenna gain, as well as to innovative approaches to high power millimeter wave circulators. The basic theory of the enhanced glow plasma is also developed.

  17. Plasma heating with multi-MeV neutral atom beams

    SciTech Connect

    Grisham, L.R.; Post, D.E.; Mikkelsen, D.R.; Eubank, H.P.

    1981-10-01

    We explore the utility and feasibility of neutral beams of greater than or equal to 6 AMU formed from negative ions, and also of D/sup 0/ formed from D/sup -/. The negative ions would be accelerated to approx. 1 to 2 MeV/AMU and neutralized, whereupon the neutral atoms would be used to heat and, perhaps, to drive current in magnetically confined plasmas. Such beams appear feasible and offer the promise of significant advantages relative to conventional neutral beams based on positive deuterium ions at approx. 150 keV.

  18. Anisotropic filamentation instability of intense laser beams in plasmas near the critical density.

    PubMed

    Sheng, Z M; Nishihara, K; Honda, T; Sentoku, Y; Mima, K; Bulanov, S V

    2001-12-01

    The relativistic filamentation instability (RFI) of linearly polarized intense laser beams in plasmas near the critical density is investigated. It is found that the RFI is anisotropic to transverse perturbations in this case; a homogeneous laser beam evolves to a stratified structure parallel to the laser polarization direction, as demonstrated recently with three-dimensional particle-in-cell simulations by Nishihara et al. [Proc. SPIE 3886, 90 (2000)]. A weakly relativistic theory is developed for plasmas near the critical density. It shows that the anisotropy of the RFI results from a suppression of the instability in the laser polarization direction due to the electrostatic response. The anisotropic RFI is also analyzed based on an envelope equation for the laser beam. Finally, the envelope equation is solved numerically, and anisotropic filamentation and self-focusing are illustrated.

  19. Crossed-Beam Energy Transfer in Direct-Drive Implosions

    NASA Astrophysics Data System (ADS)

    Igumenshchev, I. V.

    2011-10-01

    Direct-drive-implosion experiments on OMEGA have revealed the importance of crossed-beam energy transfer (CBET), which is caused by stimulated Brillouin scattering. The CBET reduces the laser absorption in a target corona by ~10% to 20% and, therefore, decreases the implosion performance. The signature of CBET is observed in time-resolved, reflected-light spectra as a suppression of red-shifted light during the main laser pulse. Simulations without CBET typically predict an earlier bang time and overestimate the laser absorption in high-compression, low-adiabat implosions. Simulations using a CBET model and a nonlocal heat-transport model explain well the scattered-light and bang-timing measurements. This talk will summarize the possible mitigation strategies for CBET required for robust ignition designs. CBET most effectively scatters incoming light that interacts with outgoing light originated from laser beam edges. This makes it possible to mitigate CBET by reducing the beam diameter with respect to the target diameter. Implosion experiments using large 1400- μm-diam plastic shells and in-focus and defocus laser beams have demonstrated the reduction of CBET in implosions with a smaller ratio of the beam-to-target diameters. Simulations predict the optimum range of this ratio to be 0.7 to 0.8. Another mitigation strategy involves splitting the incident light into two or more colors. This reduces CBET by shifting and suppressing the coupling resonances. The reduction in scattered light caused by CBET is predicted to be up to a factor of 2 when incident light colors are separated by δλ > 6 Ã. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. In collaboration with W. Seka, D. H. Edgell, D. H. Froula, V. N. Goncharov, R. S. Craxton, R. L. McCrory, A. V. Maximov, D. D. Meyerhofer, J. F. Myatt, T. C. Sangster, A. Shvydky, S. Skupsky, and C. Stoeckl. I. V. Igumenshchevet

  20. Laser Beam Propagation through Inertial Confinement Fusion Hohlraum Plasmas

    SciTech Connect

    Froula, D H; Divol, L; Meezan, N B; DIxit, S; Neumayer, P; Moody, J D; Pollock, B B; Ross, J S; Glenzer, S H

    2006-10-26

    A study of the relevant laser-plasma interaction processes has been performed in long-scale length plasmas that emulate the plasma conditions in indirect drive inertial confinement fusion targets. Experiments in this high-temperature (T{sub e} = 3.5 keV), dense (n{sub e} = 0.5 - 1 x 10{sup -3}) hohlraum plasma have demonstrated that blue 351-nm laser beams produce less than 1% total backscatter resulting in transmission greater than 90% for ignition relevant laser intensities (I < 2 x 10{sup 15} W cm{sup -2}). The bulk plasma conditions have been independently characterized using Thomson scattering where the peak electron temperatures are shown to scale with the hohlraum heater beam energy in the range from 2 keV to 3.5 keV. This feature has allowed us to determine the thresholds for both backscattering and filamentation instabilities; the former measured with absolutely calibrated full aperture backscatter and near backscatter diagnostics and the latter with a transmitted beam diagnostics. Comparing the experimental results with detailed gain calculations for the onset of significant laser scattering processes shows that these results are relevant for the outer beams in ignition hohlraum experiments corresponding to a gain threshold for stimulated Brillouin scattering of 15. By increasing the gas fill density in these experiments further accesses inner beam ignition hohlraum conditions. In this case, stimulated Raman scattering dominates the backscattering processes. They show that scattering is small for gains smaller than 20, which can be achieved through proper choice of the laser beam intensity.

  1. Electron-beam direct processing on living cell membrane

    SciTech Connect

    Hoshino, Takayuki; Morishima, Keisuke

    2011-10-24

    We demonstrated a direct processing on a living Hep G2 cell membrane in conventional cultivation conditions using an electron beam. Electron beam-induced deposition from liquid precursor 3,4-ethylenedioxythiophene and ablation was performed on the living cells. The 2.5-10 keV electron beam which was irradiated through a 100-nm-thick SiN nanomembrane could induce a deposition pattern and a ablation on a living cell membrane. This electron beam direct processing can provide simple in-situ cell surface modification for an analytical method of living cell membrane dynamic.

  2. Coherent Beam Combination Via Microparticle Plasma Modes

    NASA Astrophysics Data System (ADS)

    Rogovin, D.; Shen, T. P.

    1988-01-01

    Recently Hache, Ricard and Flytzanis have reported interesting observations and calculations on phase conjugation via degenerate four-wave mixing in gold colloids. The generation of phase conjugate radiation in these media arises from and reflects the creation of static index grating imposed on the electronic wave functions within the microparticies. These encouraging findings motivate us to consider the possibility of generating moving index gratings in these media with possible applications to coherent beam combination.

  3. Instabilities in Beam-Plasma Waves in a Model of the Beam-Driven FRC

    NASA Astrophysics Data System (ADS)

    Nicks, Bradley Scott; Necas, Ales; Tajima, Toshi; Tri Alpha Energy Team

    2016-10-01

    Using a semi-analytic solver, the kinetic properties of plasma waves are analyzed in various regimes in the presence of a beam. This analysis is done to model the strong beam-driven Field-Reversed Configuration (FRC) plasma kinetic instabilities in the neighborhood of the ion cyclotron frequency. As the frequency is relatively high, and wavelength small, the plasma is taken to be local and thus homogeneous, comprised of bulk ions, electrons, and beam ions, with a uniform background magnetic field. The beam ions are given an azimuthal drift velocity with respect to the magnetic field, but otherwise have various Maxwellian velocity distributions. First, the magnetic field is varied to create regimes of low and high β, and the mode structures are compared. The low- β case (corresponding to the scrape-off layer and near the separatrix) features primarily the beam-driven ion Bernstein instability. The high- β case (the core of FRC) is primarily electromagnetic and features the AIC instability when temperature anisotropy is included. The most unstable modes are incited by near-perpendicular beam injection with respect to the magnetic field. Finally, the results of the semi-analytic solver are compared with those from the EPOCH PIC code to evaluate the influence of nonlinear effects. This theoretical modeling was used in conjunction with EPOCH to investigate the beam driven instabilities in Tri Alpha Energy's C-2U experiment.

  4. Dynamics of Ion Beam Charge Neutralization by Ferroelectric Plasma Sources

    NASA Astrophysics Data System (ADS)

    Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C.; Ji, Qing; Persaud, Arun; Seidl, Peter A.; Schenkel, Thomas

    2016-10-01

    Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams. Here we present experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a FEPS plasma. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable. The transverse electrostatic potential of the ion beam is reduced from 15 V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Near-complete charge neutralization is established 5 μs after the driving pulse is applied to the FEPS, and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub- μs surface discharge. Measurements of current flow in the driving circuit of the FEPS suggest that plasma can be generated for tens of μs after the high voltage pulse is applied. This is confirmed by fast photography of the plasma in the 1-meter long FEPS on NDCX-II, where effective charge neutralization of the beam was achieved with the optimized FEPS timing. This work was supported by the Office of Science of the US Department of Energy under contracts DE-AC0209CH11466 (PPPL) and DE-AC0205CH11231 (LBNL).

  5. High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.

    PubMed

    Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

    2013-12-13

    We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness bunches. This injection principle is explained by example of three-dimensional particle-in-cell calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blowout regime inside a fully ionized hydrogen plasma of density 5×10(17)cm-3. Within an embedded 100  μm long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a 1.5 kA peak current, 1.5  μm transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length.

  6. Optical guiding of laser beam in nonuniform plasma

    NASA Astrophysics Data System (ADS)

    Singh Gill, Tarsem

    2000-11-01

    A plasma channel produced by a short ionising laser pulse is axially nonuniform resulting from the self-defocusing. Through such preformed plasma channel, when a delayed pulse propagates, the phenomena of diffraction, refraction and self-phase modulation come into play. We have solved the nonlinear parabolic partial differential equation governing the propagation characteristics for an approximate analytical solution using variational approach. Results are compared with the theoretical model of Liu and Tripathi ( Phys. Plasmas, 1, 3100 (1994)) based on paraxial ray approximation. Particular emphasis is on both beam width and longitudinal phase delay which are crucial to many applications.}

  7. Future Directions in Ion Beam Therapy

    NASA Astrophysics Data System (ADS)

    Habermehl, Daniel; Combs, Stephanie; Debus, Jürgen

    There is a growing interest in ion beam therapy (IBT) worldwide which has led to an increasing number of new treatment facilities. This development is accompanied by intensive radiobiological, physical and clinical research of both proton therapy (PT) and carbon ion radiotherapy (CIRT). Current developments in IBT with high impact for future challenges will be summarized in this chapter.

  8. Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams

    NASA Astrophysics Data System (ADS)

    van Tilborg, J.; Steinke, S.; Geddes, C. G. R.; Matlis, N. H.; Shaw, B. H.; Gonsalves, A. J.; Huijts, J. V.; Nakamura, K.; Daniels, J.; Schroeder, C. B.; Benedetti, C.; Esarey, E.; Bulanov, S. S.; Bobrova, N. A.; Sasorov, P. V.; Leemans, W. P.

    2015-10-01

    Compact, tunable, radially symmetric focusing of electrons is critical to laser-plasma accelerator (LPA) applications. Experiments are presented demonstrating the use of a discharge-capillary active plasma lens to focus 100-MeV-level LPA beams. The lens can provide tunable field gradients in excess of 3000 T /m , enabling cm-scale focal lengths for GeV-level beam energies and allowing LPA-based electron beams and light sources to maintain their compact footprint. For a range of lens strengths, excellent agreement with simulation was obtained.

  9. Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams.

    PubMed

    van Tilborg, J; Steinke, S; Geddes, C G R; Matlis, N H; Shaw, B H; Gonsalves, A J; Huijts, J V; Nakamura, K; Daniels, J; Schroeder, C B; Benedetti, C; Esarey, E; Bulanov, S S; Bobrova, N A; Sasorov, P V; Leemans, W P

    2015-10-30

    Compact, tunable, radially symmetric focusing of electrons is critical to laser-plasma accelerator (LPA) applications. Experiments are presented demonstrating the use of a discharge-capillary active plasma lens to focus 100-MeV-level LPA beams. The lens can provide tunable field gradients in excess of 3000 T/m, enabling cm-scale focal lengths for GeV-level beam energies and allowing LPA-based electron beams and light sources to maintain their compact footprint. For a range of lens strengths, excellent agreement with simulation was obtained.

  10. Use of molecular beams to support microspheres during plasma coating

    SciTech Connect

    Crane, J.K.; Smith, R.D.; Johnson, W.L.; Jordan, C.W.; Letts, S.A.; Korbel, G.R.; Krenik, R.M.

    1980-08-26

    Spherical targets can be levitated on beams of Ar or other gas atoms. This is an especially useful technique for supporting microspheres during plasma coating and processing. Measurements of gas flow and pressure indicate that the levitation device operates in the regime of Knudsen's flow. This device is currently being used in the development of future generation laser targets.

  11. Electron Beam Biasing of Substrates during Plasma Etching [1

    NASA Astrophysics Data System (ADS)

    Quick, A. K.; Hershkowitz, N.

    1997-10-01

    Electron beam biasing of substrates is being studied as an alternative to the usual method of using a capacitively coupled, rf-powered wafer chuck. The advantage of biasing with an electron beam is that the electrons which arrive at the wafer do so with an anisotropic velocity distribution similar to the plasma sheath-accelerated ions. This becomes important when etching large aspect ratio features. Isotropic plasma electrons can't follow the ions to the bottom of deep wells and they adhere to and charge up the feature sidewalls. This differential charging creates electric fields which deflect incoming ions and causes sidewall profile defects such as bowing, notching, and microtrenching and contributes to RIE(Reactive Ion Etch) lag( R. A. Gottscho, C. W. Jurgensen, and D. J. Vitkavage, J. Vac. Sci. Technol. B 10, Sep/Oct 1992, 2133.). The effects of etching sub-half micron nested poly-Silicon lines in Cl2 plasmas in the presence of an electron beam will be presented particularly in regard to notch suppression. The effects that the electron beam has on RIE lag suppression in SiO2 etching in fluorocarbon plasmas will also be discussed.

  12. Mono-Energetic Beams from Laser Plasma Interactions

    SciTech Connect

    Geddes, C.G.R.; Esarey, E.; Leemans, W.P.; Schroeder, C.B.; Toth,Cs.; van Tilborg, J.; Cary, John R.; Bruhwiler, David L.; Nieter, Chet

    2005-05-09

    A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100 percent electron energy spread. In the present experiments on the L'OASIS laser, the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing > 200 pC charge above 80 MeV and with normalized emittance estimated at< 2pi-mm-mrad were produced. Data and simulations (VORPAL code) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.

  13. Space-time evolution of the beam-plasma instability

    SciTech Connect

    Jones, M.E.; Lemons, D.S.; Mostrom, M.A.

    1983-10-01

    Particle-in-cell simulations of the beam-plasma instability confirm that the behavior of the interaction can be described as a wave packet that continually grows in both space and time. A consequence is that the energy deposition length of the instability becomes shorter in time, offering increased potential for this interaction to be used as an inertial fusion driver.

  14. Electric Conductivity in a Beam, Plasma System.

    DTIC Science & Technology

    1977-09-15

    internal processes such as the temperature gradient and stress tensor in fluids . He also distinguishes between two 6...processes in fluids , a macroscopic process which is represented by hydrodynamic equations and a microscopic process which allows for local...thermodynamic equilibrum . The electric conduction problem studied by Kubo16 is analogous to the macroscopic process in fluids studied by Mori)7 A study of plasma

  15. Suppression of stimulated Raman scattering due to localization of electron plasma wave in laser beam filaments

    SciTech Connect

    Sharma, Prerana; Sharma, R. P.

    2009-03-15

    The filamentation of the high power laser beam by taking off-axial contribution is investigated when ponderomotive nonlinearity is taken into account. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. It is observed that the weak electron plasma wave (EPW) propagating in the z direction is nonlinearly coupled in the modified filamentary regions of the laser beam. The semianalytical solution of the nonlinear coupled EPW equation in the presence of laser beam filaments has been found and it is observed that the nonlinear coupling between these two waves leads to localization of the EPW. Stimulated Raman scattering (SRS) of this EPW is studied and backreflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. As a result of this, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. For the typical laser beam and plasma parameters with wavelength ({lambda}=1064 nm), power flux ({approx_equal}10{sup 16} W cm{sup -2}), and plasma density (n/n{sub cr})=0.2; the backreflectivity was found to be suppressed by a factor of around 20%.

  16. Suppression of stimulated Raman scattering due to localization of electron plasma wave in laser beam filaments

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Sharma, R. P.

    2009-03-01

    The filamentation of the high power laser beam by taking off-axial contribution is investigated when ponderomotive nonlinearity is taken into account. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. It is observed that the weak electron plasma wave (EPW) propagating in the z direction is nonlinearly coupled in the modified filamentary regions of the laser beam. The semianalytical solution of the nonlinear coupled EPW equation in the presence of laser beam filaments has been found and it is observed that the nonlinear coupling between these two waves leads to localization of the EPW. Stimulated Raman scattering (SRS) of this EPW is studied and backreflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. As a result of this, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the backreflectivity. For the typical laser beam and plasma parameters with wavelength (λ =1064 nm), power flux (≈1016 W cm-2), and plasma density (n /ncr)=0.2; the backreflectivity was found to be suppressed by a factor of around 20%.

  17. Suppression of stimulated Raman scattering due to localization of electron plasma wave in laser beam filaments

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Sharma, Rampal

    2009-11-01

    The filamentation of the high power laser beam by taking off-axial contribution is investigated when ponderomotive nonlinearity is taken into account. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. It is observed that the weak electron plasma wave (EPW) propagating in the z direction is nonlinearly coupled in the modified filamentary regions of the laser beam. The semi-analytical solution of the nonlinear coupled EPW equation in the presence of laser beam filaments has been found and it is observed that the nonlinear coupling between these two waves leads to localization of the EPW. Stimulated Raman scattering (SRS) of this EPW is studied and back reflectivity has been calculated. Further, the localization of EPW affects the eigen frequency and damping of plasma wave. As a result of this, mismatch and modified enhanced Landau damping lead to the disruption of SRS process and a substantial reduction in the back reflectivity. For the typical laser beam and plasma parameters with wavelength (λ=1064nm), power flux ( 10^16 W cm-2), and plasma density (n/ncr) = 0.2; the back reflectivity was found to be suppressed by a factor of around 20%.

  18. Ion beam control in laser plasma interaction

    NASA Astrophysics Data System (ADS)

    Kawata, S.; Izumiyama, T.; Sato, D.; Nagashima, T.; Takano, M.; Barada, D.; Gu, Y. J.; Ma, Y. Y.; Kong, Q.; Wang, P. X.; Wang, W. M.

    2016-03-01

    By a two-stage successive acceleration in laser ion acceleration, our 2.5-dimensional particle-in-cell simulations demonstrate a remarkable increase in ion energy by a few hundreds of MeV; the maximum proton energy reaches about 250MeV. The ions are accelerated by the inductive continuous post-acceleration in a laser plasma interaction together with the target normal sheath acceleration and the breakout afterburner mechanism. An intense short-pulse laser generates a strong current by high-energy electrons accelerated, when an intense short- pulse laser illuminates a plasma target. The strong electric current creates a strong magnetic field along the high-energy electron current in the plasma. During the increase phase in the magnetic field strength, the moving longitudinal inductive electric field is induced by the Faraday law, and accelerates the forward-moving ions continously. The multi-stage acceleration provides a unique controllability in the ion energy and its quality.

  19. Study of beam optics and beam halo by integrated modeling of negative ion beams from plasma meniscus formation to beam acceleration

    SciTech Connect

    Miyamoto, K.; Okuda, S.; Hatayama, A.; Hanada, M.; Kojima, A.

    2013-01-14

    To understand the physical mechanism of the beam halo formation in negative ion beams, a two-dimensional particle-in-cell code for simulating the trajectories of negative ions created via surface production has been developed. The simulation code reproduces a beam halo observed in an actual negative ion beam. The negative ions extracted from the periphery of the plasma meniscus (an electro-static lens in a source plasma) are over-focused in the extractor due to large curvature of the meniscus.

  20. Electromagnetic rogue waves in beam-plasma interactions

    NASA Astrophysics Data System (ADS)

    Veldes, G. P.; Borhanian, J.; McKerr, M.; Saxena, V.; Frantzeskakis, D. J.; Kourakis, I.

    2013-06-01

    The occurrence of rogue waves (freak waves) associated with electromagnetic pulse propagation interacting with a plasma is investigated, from first principles. A multiscale technique is employed to solve the fluid Maxwell equations describing weakly nonlinear circularly polarized electromagnetic pulses in magnetized plasmas. A nonlinear Schrödinger (NLS) type equation is shown to govern the amplitude of the vector potential. A set of non-stationary envelope solutions of the NLS equation are considered as potential candidates for the modeling of rogue waves (freak waves) in beam-plasma interactions, namely in the form of the Peregrine soliton, the Akhmediev breather and the Kuznetsov-Ma breather. The variation of the structural properties of the latter structures with relevant plasma parameters is investigated, in particular focusing on the ratio between the (magnetic field dependent) cyclotron (gyro-)frequency and the plasma frequency.

  1. Long Plasma Source for Heavy Ion Beam Charge Neutralization

    SciTech Connect

    Efthimion, P.C.; Gilson, E.P.; Grisham, L.; Davidson, R.C.; Logan, B.G.; Seidl, P.A.; Waldron, W.

    2008-06-01

    Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to focus them to a small spot size and compress their axial length. The plasma source should operate at low neutral pressures and without strong externally-applied fields. To produce long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic material. High voltage ({approx} 8 kV) is applied between the drift tube and the front surface of the ceramics. A BaTiO{sub 3} source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma in the 5 x 10{sup 10} cm{sup -3} density range. The source was integrated into the NDCX device for charge neutralization and beam compression experiments, and yielded current compression ratios {approx} 120. Present research is developing multi-meter-long and higher density sources to support beam compression experiments for high energy density physics applications.

  2. Beam Phase Space of an Intense Ion Beam in a Neutralizing Plasma

    NASA Astrophysics Data System (ADS)

    Seidl, Peter A.; Bazouin, Guillaume; Beneytout, Alice; Lidia, Steven M.; Vay, Jean-Luc; Grote, David P.

    2011-10-01

    The Neutralized Drift Compression Experiment (NDCX-I) generates high intensity ion beams to explore warm dense matter physics. Transverse final focusing is accomplished with an 8-Tesla, 10-cm long pulsed solenoid magnet combined with a background neutralizing plasma to effectively cancel the space charge field of the ion beam. We report on phase space measurements of the beam before the neutralization channel and of the focused ion beam at the target plane. These are compared to WARP particle-in-cell simulations of the ion beam propagation through the focusing system and neutralizing plasma. Due to the orientation of the plasma sources with respect to the focusing magnet, the plasma distribution within the final focusing lens is strongly affected by the magnetic field, an effect which can influence the peak intensity at the target and which is included in the model of the experiment. Work performed under auspices of U.S. DoE by LLNL, LBNL under Contracts DE-AC52-07NA27344, DE-AC02-05CH1123.

  3. Pre-formed plasma channels for ion beam fusion

    NASA Astrophysics Data System (ADS)

    Peterson, R. R.; Olson, C. L.

    1997-04-01

    The transport of driver ions to the target in an IFE power plant is an important consideration in IFE target chamber design. Pre-formed laser-guided plasma discharge channels have been considered for light ions because they reduce the beam microdivergence constraints, allow long transport lengths, and require a target chamber fill gas that can help protect the target chamber from the target explosion. Here, pre-formed plasma discharge channels are considered for heavy ion transport. The channel formation parameters are similar to those for light ions. The allowable ion power per channel is limited by the onset of plasma instabilities and energy loss due to a reverse emf from the rapid channel expansion driven by the ion beam.

  4. Focused ion beams using a high-brightness plasma source

    NASA Astrophysics Data System (ADS)

    Guharay, Samar

    2002-10-01

    High-brightness ion beams, with low energy spread, have merits for many new applications in microelectronics, materials science, and biology. Negative ions are especially attractive for the applications that involve beam-solid interactions. When negative ions strike a surface, especially an electrically isolated surface, the surface charging voltage is limited to few volts [1]. This property can be effectively utilized to circumvent problems due to surface charging, such as device damage and beam defocusing. A compact plasma source, with the capability to deliver either positive or negative ion beams, has been developed. H- beams from this pulsed source showed brightness within an order of magnitude of the value for beams from liquid-metal ion sources. The beam angular intensity is > 40 mAsr-1 and the corresponding energy spread is <2.5 eV [2]. Using a simple Einzel lens with magnification of about 0.1, a focused current density of about 40 mAcm-2 is obtained. It is estimated that an additional magnification of about 0.1 can yield a focused current density of > 1 Acm-2 and a spot size of 100 nm. Such characteristics of focused beam parameters, using a dc source, will immediately open up a large area of new applications. [1] P. N. Guzdar, A. S. Sharma, S. K. Guharay, "Charging of substrates irradiated by particle beams" Appl. Phys. Lett. 71, 3302 (1997). [2] S. K. Guharay, E. Sokolovsky, J. Orloff, "Characteristics of ion beams from a Penning source for focused ion beam applications" J. Vac. Sci Technol. B17, 2779 (1999).

  5. Self-effect in expanding electron beam plasma

    SciTech Connect

    Garcia, M

    1999-05-07

    An analytical model of plasma flow from a metal plate hit by an intense, pulsed, electron beam aims to bridge the gap between radiation-hydrodynamics simulations and experiments, and to quantify the self-effect of the electron beam penetrating the flow. Does the flow disrupt the tight focus of the initial electron bunch, or later pulses in a train? This work aims to model the spatial distribution of plasma speed, density, degree of ionization, and magnetization to inquire. The initial solid density, several eV plasma expands to 1 cm and 10{sup {minus}4} relative density by 2 {micro}s, beyond which numerical simulations are imprecise. Yet, a Faraday cup detector at the ETA-II facility is at 25 cm from the target and observes the flow after 50 {micro}s. The model helps bridge this gap. The expansion of the target plasma into vacuum is so rapid that the ionized portion of the flow departs from local thermodynamic equilibrium. When the temperature (in eV) in a parcel of fluid drops below V{sub i} x [(2{gamma} - 2)/(5{gamma} + 17)], where V{sub i} is the ionization potential of the target metal (7.8 eV for tantalum), and {gamma} is the ratio of specific heats (5/3 for atoms), then the fractional ionization and electron temperature in that parcel remain fixed during subsequent expansion. The freezing temperature as defined here is V{sub i}/19. The balance between the self-pinching force and the space charge repulsion of an electron beam changes on penetrating a flow: (i) the target plasma cancels the space-charge field, (ii) internal eddy currents arise to counter the magnetization of relativistic electrons, and (iii) electron beam heating alters the flow magnetization by changing the plasma density gradient and the magnitude of the conductivity.

  6. Transformer ratio improvement for beam based plasma accelerators

    SciTech Connect

    O'Shea, Brendan; Rosenzweig, James; Barber, Samuel; Fukasawa, Atsushi; Williams, Oliver; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl

    2012-12-21

    Increasing the transformer ratio of wakefield accelerating systems improves the viability of present novel accelerating schemes. The use of asymmetric bunches to improve the transformer ratio of beam based plasma systems has been proposed for some time[1, 2] but suffered from lack appropriate beam creation systems. Recently these impediments have been overcome [3, 4] and the ability now exists to create bunches with current profiles shaped to overcome the symmetric beam limit of R {<=} 2. We present here work towards experiments designed to measure the transformer ratio of such beams, including theoretical models and simulations using VORPAL (a 3D capable PIC code) [5]. Specifically we discuss projects to be carried out in the quasi-nonlinear regime [6] at the UCLA Neptune Laboratory and the Accelerator Test Facility at Brookhaven National Lab.

  7. Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question.

    PubMed

    Yang, X; Brunetti, E; Gil, D Reboredo; Welsh, G H; Li, F Y; Cipiccia, S; Ersfeld, B; Grant, D W; Grant, P A; Islam, M R; Tooley, M P; Vieux, G; Wiggins, S M; Sheng, Z M; Jaroszynski, D A

    2017-03-10

    Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5-10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°-60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators.

  8. Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question

    PubMed Central

    Yang, X.; Brunetti, E.; Gil, D. Reboredo; Welsh, G. H.; Li, F. Y.; Cipiccia, S.; Ersfeld, B.; Grant, D. W.; Grant, P. A.; Islam, M. R.; Tooley, M. P.; Vieux, G.; Wiggins, S. M.; Sheng, Z. M.; Jaroszynski, D. A.

    2017-01-01

    Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5–10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°–60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators. PMID:28281679

  9. Ion probe beam experiments and kinetic modeling in a dense plasma focus Z-pinch

    SciTech Connect

    Schmidt, A. Ellsworth, J. Falabella, S. Link, A. McLean, H. Rusnak, B. Sears, J. Tang, V.; Welch, D.

    2014-12-15

    The Z-pinch phase of a dense plasma focus (DPF) emits multiple-MeV ions in a ∼cm length. The mechanisms through which these physically simple devices generate such high energy beams in a relatively short distance are not fully understood. We are exploring the origins of these large gradients using measurements of an ion probe beam injected into a DPF during the pinch phase and the first kinetic simulations of a DPF Z-pinch. To probe the accelerating fields in our table top experiment, we inject a 4 MeV deuteron beam along the z-axis and then sample the beam energy distribution after it passes through the pinch region. Using this technique, we have directly measured for the first time the acceleration of an injected ion beam. Our particle-in-cell simulations have been benchmarked on both a kJ-scale DPF and a MJ-scale DPF. They have reproduced experimentally measured neutron yields as well as ion beams and EM oscillations which fluid simulations do not exhibit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for accelerator and neutron source applications.

  10. Survey of Collective Instabilities and Beam-Plasma Interactions in Intense Heavy Ion Beams

    SciTech Connect

    Davidson, Ronald C.; Dorf, Mikhail A.; Kaganovich, Igor D.; Qin, Hong; Startsev, Edward A.; Rose, David V.; Lund, Steven M.; Welch, Dale R.; Sefkow, Adam

    2008-06-19

    This paper presents a survey of the present theoretical understanding based on advanced analytical and numerical studies of collective processes and beam-plasma interactions in intense heavy ion beams for applications to ion-beam-driven high energy density physics and heavy ion fusion. The topics include: discussion of the conditions for quiescent beam propagation over long distances; and the electrostatic Harris instability and the transverse electromagnetic Weibel instability in highly anisotropic, intense one-component ion beams. In the longitudinal drift compression and transverse compression regions, collective processes associated with the interaction of the intense ion beam with a charge-neutralizing background plasma are described, including the electrostatic electron-ion two-stream instability, the multispecies electromagnetic Weibel instability, and collective excitations in the presence of a solenoidal magnetic field. The effects of a velocity tilt on reducing two-stream instability growth rates are also discussed. Operating regimes are identified where the possible deleterious effects of collective processes on beam quality are minimized.

  11. Generation of metal ions in the beam plasma produced by a forevacuum-pressure electron beam source

    SciTech Connect

    Tyunkov, A. V.; Yushkov, Yu. G. Zolotukhin, D. B.; Klimov, A. S.; Savkin, K. P.

    2014-12-15

    We report on the production of metal ions of magnesium and zinc in the beam plasma formed by a forevacuum-pressure electron source. Magnesium and zinc vapor were generated by electron beam evaporation from a crucible and subsequently ionized by electron impact from the e-beam itself. Both gaseous and metallic plasmas were separately produced and characterized using a modified RGA-100 quadrupole mass-spectrometer. The fractional composition of metal isotopes in the plasma corresponds to their fractional natural abundance.

  12. Hollow structure formation of intense ion beams with sharp edge in background plasmas

    SciTech Connect

    Hu, Zhang-Hu; Wang, You-Nian

    2016-02-15

    The transport of intense ion beams with sharp radial beam edge in plasmas has been studied with two-dimensional electromagnetic particle simulations. The initial solid beam evolves into a hollow beam due to the nonlinear sharp transverse force peak in the regions of beam edge. The magnitude and nonlinearity of this peak are enhanced as the ion beam travels further into the plasma, due to the self-consistent interactions between the beam ions and the plasma electrons. This structure formation is shown to be independent on the beam radius.

  13. Ultraviolet Thomson Scattering from Direct-Drive Coronal Plasmas

    NASA Astrophysics Data System (ADS)

    Henchen, R. J.; Goncharov, V. N.; Michel, D. T.; Follett, R. K.; Katz, J.; Froula, D. H.

    2013-10-01

    Ultraviolet (λ4 ω = 263 nm) Thomson scattering (TS) was used to probe ion-acoustic waves (IAW's) and electron plasma waves (EPW's) from direct-drive coronal plasmas. Fifty-nine drive beams (λ3 ω = 351 nm) illuminate a spherical target with a radius of ~860 μm. Advances in the ultraviolet (UV) TS diagnostic at the Omega Laser Facility provide the ability to detect deep UV photons (~190 nm) and allow access to scattered light from EPW's propagating near the 3 ω quarter-critical surface (~2.5 × 1021 cm-3) . A series of experiments studied the effects of ablator materials on coronal plasma conditions. Electron temperatures and densities were measured from 150 μm to 400 μm from the initial target surface. Standard CH shells were compared to three-layered shells consisting of Si doped CH, Si, and Be. Early analysis indicates that these multilayered targets have less hot-electron energy as a result of higher electron temperature in the coronal plasma. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  14. A laser-plasma accelerator producing monoenergetic electron beams.

    PubMed

    Faure, J; Glinec, Y; Pukhov, A; Kiselev, S; Gordienko, S; Lefebvre, E; Rousseau, J-P; Burgy, F; Malka, V

    2004-09-30

    Particle accelerators are used in a wide variety of fields, ranging from medicine and biology to high-energy physics. The accelerating fields in conventional accelerators are limited to a few tens of MeV m(-1), owing to material breakdown at the walls of the structure. Thus, the production of energetic particle beams currently requires large-scale accelerators and expensive infrastructures. Laser-plasma accelerators have been proposed as a next generation of compact accelerators because of the huge electric fields they can sustain (>100 GeV m(-1)). However, it has been difficult to use them efficiently for applications because they have produced poor-quality particle beams with large energy spreads, owing to a randomization of electrons in phase space. Here we demonstrate that this randomization can be suppressed and that the quality of the electron beams can be dramatically enhanced. Within a length of 3 mm, the laser drives a plasma bubble that traps and accelerates plasma electrons. The resulting electron beam is extremely collimated and quasi-monoenergetic, with a high charge of 0.5 nC at 170 MeV.

  15. Diagnostics of ion beam generated from a Mather type plasma focus device

    SciTech Connect

    Lim, L. K. Ngoi, S. K. Wong, C. S. Yap, S. L.

    2014-03-05

    Diagnostics of ion beam emission from a 3 kJ Mather-type plasma focus device have been performed for deuterium discharge at low pressure regime. Deuterium plasma focus was found to be optimum at pressure of 0.2 mbar. The energy spectrum and total number of ions per shot from the pulsed ion beam are determined by using biased ion collectors, Faraday cup, and solid state nuclear track detector CR-39. Average energy of the ion beam obtained is about 60 keV. Total number of the ions has been determined to be in the order of 10{sup 11} per shot. Solid state nuclear track detectors (SSNTD) CR39 are employed to measure the particles at all angular direction from end on (0°) to side on (90°). Particle tracks are registered by SSNTD at 30° to 90°, except the one at the end-on 0°.

  16. Improvement of a plasma uniformity of the 2nd ion source of KSTAR neutral beam injector

    SciTech Connect

    Jeong, S. H. Kim, T. S.; Lee, K. W.; Chang, D. H.; In, S. R.; Bae, Y. S.

    2014-02-15

    The 2nd ion source of KSTAR (Korea Superconducting Tokamak Advanced Research) NBI (Neutral Beam Injector) had been developed and operated since last year. A calorimetric analysis revealed that the heat load of the back plate of the ion source is relatively higher than that of the 1st ion source of KSTAR NBI. The spatial plasma uniformity of the ion source is not good. Therefore, we intended to identify factors affecting the uniformity of a plasma density and improve it. We estimated the effects of a direction of filament current and a magnetic field configuration of the plasma generator on the plasma uniformity. We also verified that the operation conditions of an ion source could change a uniformity of the plasma density of an ion source.

  17. RF plasma source for heavy ion beam charge neutralization

    SciTech Connect

    Efthimion, Philip C.; Gilson, Erik; Grisham, Larry; Davidson, Ronald C.; Yu, Simon S.; Logan, B. Grant

    2003-05-01

    Highly ionized plasmas are being used as a medium for charge neutralizing heavy ion beams in order to focus the ion beam to a small spot size. A radio frequency (RF) plasma source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The goal is to operate the source at pressures {approx} 10{sup -5} Torr at full ionization. The initial operation of the source has been at pressures of 10{sup -4}-10{sup -1} Torr and electron densities in the range of 10{sup 8}-10{sup 11} cm{sup -3}. Recently, pulsed operation of the source has enabled operation at pressures in the 10{sup -6} Torr range with densities of 10{sup 11} cm{sup -3}. Near 100% ionization has been achieved. The source has been integrated with the NTX facility and experiments have begun.

  18. Role of beam absorption in plasma during laser welding

    SciTech Connect

    SEMAK,V.V.; STEELE,R.J.; FUERSCHBACH,PHILLIP W.; DAMKROGER,BRIAN K.

    2000-05-15

    The relationship between beam focus position and penetration depth in CW laser welding was studied numerically and experimentally for different welding conditions. Calculations were performed using a transient hydrodynamic model that incorporates the effect of evaporation recoil pressure and the associated melt expulsion. The simulation results are compared with measurements made on a series of test welds obtained using a 1650 W CO{sub 2} laser. The simulations predict, and the experiments confirm, that maximum penetration occurs with a specific location of the beam focus, with respect to the original sample surface, and that this relationship depends on the processing conditions. In particular, beam absorption in the plasma has a significant effect on the relationship between penetration and focus position. When the process parameters result in strong beam absorption in the keyhole plasma, the maximum penetration will occur when the laser focus is at or above the sample surface. In a case of weak absorption however, the penetration depth reaches its maximum value when the beam focus is located below the sample surface. In all cases, the numerical results are in good agreement with the experimental measurements.

  19. Beam-Plasma Instabilities in a 2D Yukawa Lattice

    SciTech Connect

    Kyrkos, S.; Kalman, G. J.; Rosenberg, M.

    2009-06-05

    We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.

  20. Neutral Beam Injection for Plasma and Magnetic FieldDiagnostics

    SciTech Connect

    Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Kwan, Joe W.; Levinton,Fred

    2007-08-01

    At the Lawrence Berkeley National Laboratory (LBNL) adiagnostic neutral beam injection system for measuring plasma parameters,flow velocity, and local magnetic field is being developed. High protonfraction and small divergence is essential for diagnostic neutral beams.In our design, a neutral hydrogen beam with an 8 cm x 11 cm (or smaller)elliptical beam spot at 2.5 m from the end of the extraction column isproduced. The beam will deliver up to 5 A of hydrogen beam to the targetwith a pulse width of ~;1 s, once every 1 - 2 min. The H1+ ion species ofthe hydrogen beamwill be over 90 percent. For this application, we havecompared two types of RF driven multicusp ion sources operating at 13.56MHz. The first one is an ion source with an external spiral antennabehind a dielectric RF-window. The second one uses an internal antenna insimilar ion source geometry. The source needs to generate uniform plasmaover a large (8 cm x 5 cm) extraction area. We expect that the ion sourcewith internal antenna will be more efficient at producing the desiredplasma density but might have the issue of limited antenna lifetime,depending on the duty factor. For both approaches there is a need forextra shielding to protect the dielectric materials from the backstreaming electrons. The source walls will be made of insulator materialsuch as quartz that has been observed to generate plasma with higheratomic fraction than sources with metal walls. The ion beam will beextracted and accelerated by a set of grids with slits, thus forming anarray of 6 sheet-shaped beamlets. The multiple grid extraction will beoptimized using computer simulation programs. Neutralization of the beamwill be done in neutralization chamber, which has over 70 percentneutralization efficiency.

  1. Beams of fast neutral atoms and molecules in low-pressure gas-discharge plasma

    SciTech Connect

    Metel, A. S.

    2012-03-15

    Fast neutral atom and molecule beams have been studied, the beams being produced in a vacuum chamber at nitrogen, argon, or helium pressure of 0.1-10 Pa due to charge-exchange collisions of ions accelerated in the sheath between the glow discharge plasma and a negative grid immersed therein. From a flat grid, two broad beams of molecules with continuous distribution of their energy from zero up to e(U + U{sub c}) (where U is voltage between the grid and the vacuum chamber and U{sub c} is cathode fall of the discharge) are propagating in opposite directions. The beam propagating from the concave surface of a 0.2-m-diameter grid is focused within a 10-mm-diameter spot on the target surface. When a 0.2-m-diameter 0.2-m-high cylindrical grid covered by end disks and composed of parallel 1.5-mm-diameter knitting needles spaced by 4.5 mm is immersed in the plasma, the accelerated ions pass through the gaps between the needles, turn inside the grid into fast atoms or molecules, and escape from the grid through the gaps on its opposite side. The Doppler shift of spectral lines allows for measuring the fast atom energy, which corresponds to the potential difference between the plasma inside the chamber and the plasma produced as a result of charge-exchange collisions inside the cylindrical grid.

  2. Plasma Charge Current for Controlling and Monitoring Electron Beam Welding with Beam Oscillation

    PubMed Central

    Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

    2012-01-01

    Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process. PMID:23242276

  3. Plasma charge current for controlling and monitoring electron beam welding with beam oscillation.

    PubMed

    Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

    2012-12-14

    Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process.

  4. Evaluation of two-beam spectroscopy as a plasma diagnostic

    SciTech Connect

    Billard, B.D.

    1980-04-01

    A two-beam spectroscopy (TBS) system is evaluated theoretically and experimentally. This new spectroscopic technique uses correlations between components of emitted light separated by a small difference in angle of propagation. It is thus a non-perturbing plasma diagnostic which is shown to provide local (as opposed to line-of-sight averaged) information about fluctuations in the density of light sources within a plasma - information not obtainable by the usual spectroscopic methods. The present design is an improvement on earlier systems proposed in a thesis by Rostler.

  5. Scaling of the beam plasma discharge for low magnetic fields

    NASA Technical Reports Server (NTRS)

    Papadopoulos, K.

    1986-01-01

    A theoretical analysis of the scaling law and the value of the threshold current for beam plasma discharge (BPD) is presented, based on the requirement for an absolute instability near the plasma frequency. It is shown that both the scaling law as well as the numerical values of Ic are consistent with the experimental data, in the low pressure regimes and for weak magnetic field experiments if the dominant particle loss mechanism is due to Bohm diffusion. The implications of the findings to electron injection in space are discussed.

  6. Particle simulation for direct plasma injection in a radio frequency quadrupole matching section.

    PubMed

    Tamura, J; Hattori, T; Hayashizaki, N; Ishibashi, T; Kanesue, T; Kashiwagi, H; Kondo, K; Okamura, M

    2010-02-01

    We have been investigating direct plasma injection scheme (DPIS) for high-intensity heavy-ion beam acceleration. In the DPIS, laser-produced plasma is directly injected into a radio frequency quadrupole (RFQ) linac. To study the beam dynamics of the ion injection in the DPIS, we tracked particle motions in the RFQ matching section using three-dimensional particle-in-cell method. As a result of the numerical simulation, we found that the electrostatic field generated by the extraction electrode reduces the transmission efficiency. To avoid the radially defocusing force, the input beam into the RFQ has to be initially convergent. In the DPIS, further optimization of the plasma density is required for better matching.

  7. The spatial evolution of energetic electrons and plasma waves during the steady state beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Llobet, X.; Bernstein, W.; Kondradi, A.

    1985-01-01

    Experiments, involving the injection of energetic (keV) electron beams into the ionosphere-upper atmosphere system from rocket-borne electron guns, have provided evidence for the occurrence of strong beam-plasma interactions (BPI) both near to and remote from the injection point. However, the flight experiments have not provided clear and unambiguous evidence for the basic physical processes which produce the variety of confusing signatures. A laboratory experimental program was initiated to clarify some of a number of ambiguities regarding the obtained results. The present investigation is concerned with some experimental studies of the evolution of both the beam energy spectrum and the local wave amplitude-frequency spectrum at increasing axial distances from the electron gun for a variety of experimental conditions. The results of the studies show that the high frequency beam-plasma interaction represents the most important process.

  8. Excitation of Accelerating Plasma Waves by Counter-propagating Laser Beams

    SciTech Connect

    Gennady Shvets; Nathaniel J. Fisch; and Alexander Pukhov

    2001-08-30

    Generation of accelerating plasma waves using two counter-propagating laser beams is considered. Colliding-beam accelerator requires two laser pulses: the long pump and the short timing beam. We emphasize the similarities and differences between the conventional laser wakefield accelerator and the colliding-beam accelerator (CBA). The highly nonlinear nature of the wake excitation is explained using both nonlinear optics and plasma physics concepts. Two regimes of CBA are considered: (i) the short-pulse regime, where the timing beam is shorter than the plasma period, and (ii) the parametric excitation regime, where the timing beam is longer than the plasma period. Possible future experiments are also outlined.

  9. Energetic Ion Beam Production by a Low-Pressure Plasma Focus Discharge

    SciTech Connect

    Lim, L. K.; Yap, S. L.; Wong, C. S.

    2011-03-30

    Energetic ion beam emissions in a 3 kJ Mather type plasma focus operating at low-pressure regime are investigated. Deuterium gas is used and the discharge is operated in a low-pressure regime of below 1 mbar. Formation of the current sheath during the breakdown phase at the back wall is assisted by a set delayed trigger pulse. Energetic and intense ion beams with good reproducibility have been obtained for the operating pressure ranging from 0.05 mbar to 0.5 mbar. Deuteron beam is determined by time resolved measurement by making use of three biased ion collectors placed at the end on direction. The average energies of deuteron beams are resolved by using time-of flight method. Correlation between the ion emissions and the current sheath dynamics is also discussed.

  10. Toroidal midplane neutral beam armor and plasma limiter

    DOEpatents

    Kugel, H.W.; Hand, S.W. Jr.; Ksayian, H.

    1985-05-31

    This invention contemplates an armor shield/plasma limiter positioned upon the inner wall of a toroidal vacuum chamber within which is magnetically confined an energetic plasma in a tokamak nuclear fusion reactor. The armor shield/plasma limiter is thus of a general semi-toroidal shape and is comprised of a plurality of adjacent graphite plates positioned immediately adjacent to each other so as to form a continuous ring upon and around the toroidal chamber's inner wall and the reactor's midplane coil. Each plate has a generally semi-circular outer circumference and a recessed inner portion and is comprised of upper and lower half sections positioned immediately adjacent to one another along the midplane of the plate. With the upper and lower half sections thus joined, a channel or duct is provided within the midplane of the plate in which a magnetic flux loop is positioned. The magnetic flux loop is thus positioned immediately adjacent to the fusing toroidal plasma and serves as a diagnostic sensor with the armor shield/plasma limiter minimizing the amount of power from the energetic plasma as well as from the neutral particle beams heating the plasma incident upon the flux loop.

  11. Application of electron beam plasma for biopolymers modification

    NASA Astrophysics Data System (ADS)

    Vasilieva, T. M.

    2012-06-01

    The effects of the Electron Beam Plasma treatment on natural polysaccharide chitosan were studied experimentally. Low molecular water-soluble products of chitosan and chitooligosaccharides were obtained by treating the original polymers in the Electron Beam Plasma of oxygen and water vapor. The molecular mass of the products varied from 18 kDa to monomeric fragments. The degradation of the original polymers was due to the action of active oxygen particles (atomic and singlet oxygen) and the particles of the water plasmolysis (hydroxyl radicals, hydrogen peroxides). The 95% yield of low molecular weight chitosans was attained by optimizing the treatment conditions. The studies of the antimicrobial activity of low molecular products showed that they strongly inhibit the multiplication of colon bacillus, aurococcus and yeast-like fungi. The EBP-stimulated degradation of polysaccharides and proteins were found to result from breaking β-1,4 glycosidic bounds and peptide bonds, respectively.

  12. Mechanism analysis of radiation generated by the beam-plasma interaction in a vacuum diode

    NASA Astrophysics Data System (ADS)

    Zengchao, Ji; Shixiu, Chen; Shen, Gao

    2017-01-01

    When we were studying the vacuum switch, we found that the vacuum diode can radiate a broadband microwave. The vacuum diode is comprised of a cathode with a trigger device and planar anode, there is not a metallic bellows waveguide structure in this device, so the radiation mechanism of the vacuum diode is different from the plasma filled microwave device. It is hard to completely imitate the theory of the plasma filled microwave device. This paper analyzes the breakdown process of the vacuum diode, establishes the mathematical model of the radiating microwave from the vacuum diode. Based on the analysis of the dispersion relation in the form of a refractive index, the electromagnetic waves generated in the vacuum diode will resonate. The included angle between the direction of the electromagnetic radiation and the initial motion direction of electron beam is 45 degrees. The paper isolates the electrostatic effect from the beam-plasma interaction when the electromagnetic radiation occurs. According to above analyses, the dispersion relations of radiation are obtained by solving the wave equation. The dispersion curves are also obtained based on the theoretical dispersion relations. The theoretical dispersion curves are consistent with the actual measurement time-frequency maps of the radiation. Theoretical deduction and experiments indicate that the reason for microwave radiating from the vacuum diode can be well explained by the interaction of the electron beam and magnetized plasma. Supported by National Nature Science Foundation of China (No. 11075123), the Young Scientists Fund of Nature Science Foundation of China (No. 51207171).

  13. Heavy Neutral Beam Probe for Edge Plasma Analysis in Tokamaks

    SciTech Connect

    Castracane, J.

    2001-01-04

    The Heavy Neutral Beam Probe (HNBP) developed initially with DOE funding under the Small Business Innovation Research (SBIR) program was installed on the Tokamak de Varennes (TdeV) at the CCFM. This diagnostic was designed to perform fundamental measurements of edge plasma properties. The hardware was capable of measuring electron density and potential profiles with high spatial and temporal resolution. Fluctuation spectra for these parameters were obtained with HNBP for transport studies.

  14. PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS

    SciTech Connect

    Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R.; Yoon, P. H.; Pavan, J. E-mail: yoonp@umd.edu

    2016-02-10

    The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.

  15. Plasma Emission by Counter-streaming Electron Beams

    NASA Astrophysics Data System (ADS)

    Ziebell, L. F.; Petruzzellis, L. T.; Yoon, P. H.; Gaelzer, R.; Pavan, J.

    2016-02-01

    The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.

  16. Excitation of Plasma Waves in Aurora by Electron Beams

    NASA Technical Reports Server (NTRS)

    daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.

    1996-01-01

    In this paper, we study numerically the excitation of plasma waves by electron beams, in the auroral region above 2000 km of altitude. We have solved the fully kinetic dispersion relation, using numerical method and found the real frequency and the growth rate of the plasma wave modes. We have examined the instability properties of low-frequency waves such as the Electromagnetic Ion Cyclotron (EMIC) wave as well as Lower-Hybrid (LH) wave in the range of high-frequency. In all cases, the source of free energy are electron beams propagating parallel to the geomagnetic field. We present some features of the growth rate modes, when the cold plasma parameters are changed, such as background electrons and ions species (H(+) and O(+)) temperature, density or the electron beam density and/or drift velocity. These results can be used in a test-particle simulation code, to investigate the ion acceleration and their implication in the auroral acceleration processes, by wave-particle interaction.

  17. Ion beam and plasma methods of producing diamondlike carbon films

    NASA Technical Reports Server (NTRS)

    Swec, Diane M.; Mirtich, Michael J.; Banks, Bruce A.

    1988-01-01

    A variety of plasma and ion beam techniques was employed to generate diamondlike carbon films. These methods included the use of RF sputtering, dc glow discharge, vacuum arc, plasma gun, ion beam sputtering, and both single and dual ion beam deposition. Since films were generated using a wide variety of techniques, the physico-chemical properties of these films varied considerably. In general, these films had characteristics that were desirable in a number of applications. For example, the films generated using both single and dual ion beam systems were evaluated for applications including power electronics as insulated gates and protective coatings on transmitting windows. These films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Nuclear reaction and combustion analysis indicated hydrogen to carbon ratios to be 1.00, which allowed the films to have good transmittance not only in the infrared, but also in the visible. Other evaluated properties of these films include band gap, resistivity, adherence, density, microhardness, and intrinsic stress. The results of these studies and those of the other techniques for depositing diamondlike carbon films are presented.

  18. Probabilistic model of beam-plasma interaction and electromagnetic radioemission

    NASA Astrophysics Data System (ADS)

    Krasnoselskikh, Vladimir; Volokitin, Alexander; Krafft, Catherine; Voshchepynets, Andrii

    2016-07-01

    In this presentation we describe the effects of plasma density fluctuations in the solar wind on the relaxation of the electron beams accelerated in the bow shock front. The density fluctuations are supposed to be responsible for the changes in the local phase velocity of the Langmuir waves generated by the beam instability. Changes in the wave phase velocity during the wave propagation can be described in terms of probability distribution function determined by distribution of the density fluctuations. Using these probability distributions we describe resonant wave particle interactions by a system of equations, similar to well known quasi-linear approximation, where the conventional velocity diffusion coefficient and the wave growth rate are replaced by the averaged in the velocity space. It was shown that the process of relaxation of electron beam is accompanied by transformation of significant part of the beam kinetic energy to energy of the accelerated particles via generation and absorption of the Langmuir waves. Generated Langmuir waves are transformed into electromagnetic waves in the vicinity of the reflection points when the level of density fluctuations is large enough. We evaluate the level of the radiowaves intensity, and the emissivity diagram of radiowaves emission around plasma frequency and its harmonics.

  19. Electron beam injection experiments - The beam-plasma discharge at low pressures and magnetic field strengths

    NASA Technical Reports Server (NTRS)

    Bernstein, W.; Leinbach, H.; Kellogg, P.; Monson, S.; Hallinan, T.; Garriott, O. K.; Konradi, A.; Mccoy, J.; Daly, P.; Baker, B.

    1978-01-01

    The paper describes electron beam injection experiments which clarify observational results obtained in rocket flights. A column of enhanced density plasma, exceeding the density expected from ionization by primary beam electrons, was observed in a large vacuum system at low magnetic fields (1 to 1.5 G) and low ambient pressures (10 to the minus 6 to 10 to the minus 5 torr). The peak luminosity of the discharge was about 10 times that of the beam alone, and the radius increased by a factor of three. In the absence of the discharge, RF emission is observed at 1.1 to 1.2 times the cyclotron frequency, and a strong band of RF noise with upper frequency cutoff at about the cyclotron frequency is observed in the discharge mode, along with higher frequency noise at or near the plasma frequency. The onset of the plasma discharge is critically dependent on beam current. The described results agree with observations obtained at much higher densities and magnetic fields in fusion research studies.

  20. Two-dimensional studies of relativistic electron beam plasma instabilities in an inhomogeneous plasma

    SciTech Connect

    Shukla, Chandrasekhar; Das, Amita; Patel, Kartik

    2015-11-15

    Relativistic electron beam propagation in plasma is fraught with several micro instabilities like two stream, filamentation, etc., in plasma. This results in severe limitation of the electron transport through a plasma medium. Recently, however, there has been an experimental demonstration of improved transport of Mega Ampere of electron currents (generated by the interaction of intense laser with solid target) in a carbon nanotube structured solid target [G. Chatterjee et al., Phys. Rev. Lett. 108, 235005 (2012)]. This then suggests that the inhomogeneous plasma (created by the ionization of carbon nanotube structured target) helps in containing the growth of the beam plasma instabilities. This manuscript addresses this issue with the help of a detailed analytical study and 2-D Particle-In-Cell simulations. The study conclusively demonstrates that the growth rate of the dominant instability in the 2-D geometry decreases when the plasma density is chosen to be inhomogeneous, provided the scale length 1/k{sub s} of the inhomogeneous plasma is less than the typical plasma skin depth (c/ω{sub 0}) scale. At such small scale lengths channelization of currents is also observed in simulation.

  1. Development of a non-ideal plasma target for non-linear beam plasma interaction experiments

    NASA Astrophysics Data System (ADS)

    Katagiri, K.; Nishinomiya, S.; Niinou, T.; Kaneko, J.; Hasegawa, J.; Ogawa, M.; Oguri, Y.

    2007-07-01

    A shock-driven plasma target was developed to examine non-linear interactions between low-energy heavy ions and cold-dense plasmas. MD calculations predicted that beam-plasma coupling constant γ˜0.1 must be achieved to observe the non-linearity, which corresponds to the plasma coupling constant Γ≈0.2 for projectiles of vproj≈10 keV/u and q≈2. One-dimensional numerical estimations using SESAME equation of state showed that a shock wave propagating in 5-Torr H2 gas with 47 km/s must be produced to satisfy Γ≈0.2. Utilizing an electromagnetic shock tube with a peak current of 50 kA and a current rise time of 800 ns, we achieved a shock speed of 45 km/s. The electron density distribution of the shock-produced plasma along the beam axis was measured by a Mach-Zehnder interferometer. From this measurement we confirmed that the electron density was over 1017 cm-3 and the homogeneity was acceptable during several hundred nanoseconds. The electron temperature was also determined by optical spectroscopic measurements. The Coulomb coupling constant was evaluated using these experimental data to investigate feasibility of the beam-plasma interaction experiments.

  2. Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas

    NASA Astrophysics Data System (ADS)

    Thurgood, Jonathan O.; Tsiklauri, David

    2016-12-01

    Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory and Hamiltonian models based on Zakharov's equations have indicated that when the level of density fluctuations is above a given threshold, density irregularities act to de-resonate the beam-plasma interaction, restricting Langmuir wave growth on the expense of beam energy. This work presents the first fully kinetic particle-in-cell (PIC) simulations of beam relaxation under the influence of density irregularities. We aim to independently determine the influence of background inhomogeneity on the beam-plasma system, and to test theoretical predictions and alternative models using a fully kinetic treatment. We carry out one-dimensional (1-D) PIC simulations of a bump-on-tail unstable electron beam in the presence of increasing levels of background inhomogeneity using the fully electromagnetic, relativistic EPOCH PIC code. We find that in the case of homogeneous background plasma density, Langmuir wave packets are generated at the resonant condition and then quasi-linear relaxation leads to a dynamic increase of wavenumbers generated. No electron acceleration is seen - unlike in the inhomogeneous experiments, all of which produce high-energy electrons. For the inhomogeneous experiments we also observe the generation of backwards-propagating Langmuir waves, which is shown directly to be due to the refraction of the packets off the density gradients. In the case of higher-amplitude density fluctuations, similar features to the weaker cases are found, but also packets can also deviate from the expected dispersion curve in -space due to nonlinearity. Our fully kinetic PIC simulations broadly confirm the findings of quasi-linear theory and the Hamiltonian model based on Zakharov's equations. Strong density fluctuations

  3. Numerical model of the plasma formation at electron beam welding

    SciTech Connect

    Trushnikov, D. N.; Mladenov, G. M.

    2015-01-07

    The model of plasma formation in the keyhole in liquid metal as well as above the electron beam welding zone is described. The model is based on solution of two equations for the density of electrons and the mean electron energy. The mass transfer of heavy plasma particles (neutral atoms, excited atoms, and ions) is taken into account in the analysis by the diffusion equation for a multicomponent mixture. The electrostatic field is calculated using the Poisson equation. Thermionic electron emission is calculated for the keyhole wall. The ionization intensity of the vapors due to beam electrons and high-energy secondary and backscattered electrons is calibrated using the plasma parameters when there is no polarized collector electrode above the welding zone. The calculated data are in good agreement with experimental data. Results for the plasma parameters for excitation of a non-independent discharge are given. It is shown that there is a need to take into account the effect of a strong electric field near the keyhole walls on electron emission (the Schottky effect) in the calculation of the current for a non-independent discharge (hot cathode gas discharge). The calculated electron drift velocities are much bigger than the velocity at which current instabilities arise. This confirms the hypothesis for ion-acoustic instabilities, observed experimentally in previous research.

  4. Cathode Plasma Formation in High Intensity Electron Beam Diodes

    NASA Astrophysics Data System (ADS)

    Johnston, Mark; Kiefer, Mark; Oliver, Bryan; Bennett, Nichelle; Droemer, Darryl; Bernshtam, V.; Doron, R.; Maron, Yitzhak

    2013-10-01

    This talk will detail the experimental results and conclusions obtained for cathode plasma formation on the Self-Magnetic Pinch (SMP) diode fielded on the RITS-6 accelerator (4-7.5 MeV) at Sandia National Laboratories. The SMP diode utilizes a hollowed metal cathode to produce high power (TW), focused electron beams (<3 mm diameter) which are used for flash x-ray radiography applications. Optical diagnostics include high speed (<10 ns) framing cameras, optical streak cameras, and spectroscopy. The cathode plasma in this high electric (MV/cm) and magnetic (>10 Tesla) field environment forms well-defined striations. These striations have been examined for a number of different cathode sizes, vacuum gap spacings, and diode voltages. Optical streak images have been taken to determine the time evolution of the plasma, and optical spectroscopy has been employed to determine its constituents as well as their densities and temperatures inferred from detailed time-dependent, collisional-radiative (CR) and radiation transport modelings. Comments will be made as to the overall effect of the cathode plasma in regards to the diode impedance and electron beam focusing. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Coulomb repulsion and the electron beam directed energy weapon

    NASA Astrophysics Data System (ADS)

    Retsky, Michael W.

    2004-09-01

    Mutual repulsion of discrete charged particles or Coulomb repulsion is widely considered to be an ultimate hard limit in charged particle optics. It prevents the ability to finely focus high current beams into small spots at large distances from defining apertures. A classic example is the 1970s era "Star Wars" study of an electron beam directed energy weapon as an orbiting antiballistic missile device. After much analysis, it was considered physically impossible to focus a 1000-amp 1-GeV beam into a 1-cm diameter spot 1000-km from the beam generator. The main reason was that a 1-cm diameter beam would spread to 5-m diameter at 1000-km due to Coulomb repulsion. Since this could not be overcome, the idea was abandoned. But is this true? What if the rays were reversed? That is, start with a 5-m beam converging slightly with the same nonuniform angular and energy distribution as the electrons from the original problem were spreading at 1000-km distance. Could Coulomb repulsion be overcome? Looking at the terms in computational studies, some are reversible while others are not. Based on estimates, the nonreversible terms should be small - of the order of 0.1 mm. If this is true, it is possible to design a practical electron beam directed weapon not limited by Coulomb repulsion.

  6. Ion energy distribution near a plasma meniscus with beam extraction for multi element focused ion beams

    SciTech Connect

    Mathew, Jose V.; Paul, Samit; Bhattacharjee, Sudeep

    2010-05-15

    An earlier study of the axial ion energy distribution in the extraction region (plasma meniscus) of a compact microwave plasma ion source showed that the axial ion energy spread near the meniscus is small ({approx}5 eV) and comparable to that of a liquid metal ion source, making it a promising candidate for focused ion beam (FIB) applications [J. V. Mathew and S. Bhattacharjee, J. Appl. Phys. 105, 96101 (2009)]. In the present work we have investigated the radial ion energy distribution (IED) under the influence of beam extraction. Initially a single Einzel lens system has been used for beam extraction with potentials up to -6 kV for obtaining parallel beams. In situ measurements of IED with extraction voltages upto -5 kV indicates that beam extraction has a weak influence on the energy spread ({+-}0.5 eV) which is of significance from the point of view of FIB applications. It is found that by reducing the geometrical acceptance angle at the ion energy analyzer probe, close to unidirectional distribution can be obtained with a spread that is smaller by at least 1 eV.

  7. A Single-Probe-Beam, Dual-Frequency Plasma Polarimeter

    NASA Astrophysics Data System (ADS)

    Munro, Blair; Hicks, Nathaniel

    2016-10-01

    A plasma polarimeter instrument is conceived that comprises a single microwave probe beam alternating between two discrete frequencies. The method is similar to a double-heterodyne approach proposed earlier, but reduces system complexity and cost by avoiding a frequency-swept source. The instrument uses a single detector per beamline. Initial synthetic diagnostic testing of the instrument design is presented, and the prospects for further cost and space saving by way of additive manufacturing of instrument quasi-optical components are considered. A test bench setup for initial testing of the dual-frequency source and optical path is described, as is the plan for magnetized plasma measurements in a new plasma laboratory facility at the University of Alaska Anchorage. Supported by UAA Elizabeth Tower Endowment and Complex Systems Group.

  8. Diagnostic studies of ion beam formation in inductively coupled plasma

    SciTech Connect

    Jacobs, Jenee L.

    2015-01-01

    This dissertation describes a variety of studies focused on the plasma and the ion beam in inductively coupled plasma mass spectrometry (ICP-MS). The ability to use ICP-MS for measurements of trace elements in samples requires the analytes to be efficiently ionized. Updated ionization efficiency tables are discussed for ionization temperatures of 6500 K and 7000 K with an electron density of 1 x 1015 cm-3. These values are reflective of the current operating parameters of ICP-MS instruments. Calculations are also discussed for doubly charged (M2+) ion formation, neutral metal oxide (MO) ionization, and metal oxide (MO+) ion dissociation for similar plasma temperature values. Ionization efficiency results for neutral MO molecules in the ICP have not been reported previously.

  9. Modeling nitrogen plasmas produced by intense electron beams

    NASA Astrophysics Data System (ADS)

    Angus, Justin; Swanekamp, Steve; Richardson, Andrew; Schumer, Joseph; Mosher, David; Ottinger, Paul

    2016-10-01

    The Gamble II generator at the Naval Research Laboratory produces 100ns pulse duration, relativistic-electron beams with peak energies on the order of 1MV and peak currents of about 800kA with annular beam areas between 40-80cm2. This gives peak current densities 10 kA/cm2. For many different applications, a nitrogen gas in the 1Torr range is used as a charge- and current-neutralizing background to achieve beam transport. For these parameter regimes, the gas transitions from a weakly-ionized molecular state to a strongly-ionized atomic state on the time scale of the beam pulse. A detailed gas-chemistry model is presented for a dynamical description of the nitrogen plasmas produced in such experiments. The model is coupled to a 0D circuit model representative of annular beams, and results for 1Torr nitrogen are in good agreement with experimental measurements of the line-integrated electron density and the net current. It is found that the species are mostly in the ground and metastable states during the atomic phase, but that ionization proceeds predominantly through thermal ionization of the higher-lying optically-allowed states with excitation energies close to the ionization limit. Work is supported by AWE through NNSA.

  10. Imaging system for low-density plasma by heterodyne interferometer with fan beam microwave

    NASA Astrophysics Data System (ADS)

    Ito, H.; Yugami, N.; Nishida, Y.; Sakai, W.

    2002-12-01

    A microwave imaging system based on a heterodyne interferometer has been developed to measure the spatial distribution of the plasma density without introducing any direct disturbance to the plasma by employing a diode array scattering technique. The imaging system with the use of a fan beam microwave for a radar system demonstrates the principle of the technique by placing finite-size dielectric phantoms instead of the plasma between the horn antenna and the diode antenna array. Experimental results show that very good image of the objects can be reconstructed and the system is equivalent to popularly known multichannel imaging system. As a result, it is possible to make simple, low-cost, and compact microwave interferometer for measuring the spatial distribution of the plasma density.

  11. Plasma wakefield diagnostics using probe electron beam and microchannel plates

    SciTech Connect

    Fainberg, Ya.B.; Balakirev, V.A.; Berezin, A.K.

    1996-12-31

    The analytical and numerical investigations of trajectories of the probe beam electrons in the two dimensional wakefield, excited in plasma by a dense bunch of relativistic electrons with Gauss longitudinal and transverse distribution of density is carried out. On basis of calculations of probe beam deviations the diagnostic instruments is developed for parameters of experiments conducted in NSC KIPT. The diagnostic instruments consist of an electron gun forming the electron beam with energy 10KeV, current 10{mu}A and diameter 2mm which passes through the chamber of interaction and falls on collector of diameter 10mm. Collector (screen) is placed in front of the first plate of microchannel amplifier which consists of three microchannel plates (MCP) with sizes 20 - 30mm, The voltage 3kV was applied to the each plate. Total amplification of MCP amplifier is 10{sup 4} - 10{sup 5} in dependence on quantity of particles, falling on the first plate. As a result the deviations of probe beam by excited wakefield the electrons fall on first plate of amplifier and are registered by anode of amplifier, located behind the third plates. Calculated probe beam deviations and obtained amplification of MCP amplifier permit to find out and to investigate the electrical wakefields, excited by the sequence of relativistic bunches (number of particles in bunch is 2x10{sup 9}, energy is 14MeV) in plasma of density 10{sup 11} - 10{sup 13} cm{sup {minus}3}. The maximal value of the fields registered by such technique is not less 2kv/cm.

  12. Direct design of laser-beam shapers, zoom-beam expanders, and combinations thereof

    NASA Astrophysics Data System (ADS)

    Duerr, Fabian; Thienpont, Hugo

    2016-10-01

    Laser sources have become indispensable for industrial materials processing applications like surface treatment, cutting or welding to name a few examples. Many of these applications pose different requirements on the delivered laser irradiance distribution. Some applications might not only favor a specific irradiance distribution (e.g. a at-top) but can additionally benefit from time-varying distributions. We present an overview of a recently developed design approach that allows direct calculation of virtually any refractive or reflective laser beam shaping system. The derived analytic solution is fully described by few initial parameters and does allow an increasingly accurate calculation of all optical surfaces. Unlike other existing direct design methods for laser beam shaping, there is almost no limitation in the number of surfaces that can be calculated with this approach. This is of particular importance for optical designs of dynamic systems such as variable optical beam expanders that require four (or more) optical surfaces. Besides conventional static beam shapers, we present direct designs of zoom beam expanders, and as a novelty, a class of dynamic systems that shape and expand the input beam simultaneously. Such dynamic zoom beam shapers consist of a minimal number of optical elements and provide a much more compact solution, yet achieving excellent overall optical performance throughout the full range of zoom positions.

  13. Relativistic ponderomotive effect on the propagation of rippled laser beam and the excitation of electron plasma wave in collisionless plasma

    NASA Astrophysics Data System (ADS)

    Priyanka; Chauhan, Prashant; Purohit, Gunjan

    2013-01-01

    This paper presents an investigation of the propagation of rippled laser beam in a collisionless plasma and its effect on and the excitation of electron plasma wave and particle acceleration, when relativistic and ponderomotive nonlinearities are simultaneously operative. Electron plasma wave (EPW) coupling with rippled laser beam arises on account of the relativistic change in the electron mass and the modification of the background electron density due to ponderomotive nonlinearity. When the electron plasma wave gets coupled to the rippled laser beam, a large fraction of the pump energy gets transferred to EPW and this excited EPW can accelerate the electrons. Analytical expressions for the growth rate of the laser spike in plasma, beam width of the rippled laser beam and excited electron plasma wave have been obtained using paraxial ray approximation. These coupled equations are solved analytically and numerically to study the growth of laser spike in plasma and its effect on the self focusing of rippled laser beam in plasma, amplitude of the excited electron plasma wave and particle acceleration. The result shows that the effect of including ponderomotive nonlinearity significantly affects the growth of laser spike in plasma, excitation of electron plasma wave as well as the number of energetic electrons in particle acceleration process. The results are presented for typical laser plasma parameters.

  14. Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

    NASA Astrophysics Data System (ADS)

    Deng, Yongfeng; Tan, Chang; Han, Xianwei; Tan, Yonghua

    2012-02-01

    For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo (MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.

  15. Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

    NASA Astrophysics Data System (ADS)

    Girardo, Jean-Baptiste; Sharapov, Sergei; Boom, Jurrian; Dumont, Rémi; Eriksson, Jacob; Fitzgerald, Michael; Garbet, Xavier; Hawkes, Nick; Kiptily, Vasily; Lupelli, Ivan; Mantsinen, Mervi; Sarazin, Yanick; Schneider, Mireille

    2016-01-01

    Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called "tornado" modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.

  16. Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

    SciTech Connect

    Girardo, Jean-Baptiste; Sharapov, Sergei; Fitzgerald, Michael; Hawkes, Nick; Kiptily, Vasily; Lupelli, Ivan; Boom, Jurrian; Dumont, Rémi; Garbet, Xavier; Sarazin, Yanick; Schneider, Mireille; Eriksson, Jacob; Mantsinen, Mervi

    2016-01-15

    Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called “tornado” modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.

  17. Runaway electron production during intense electron beam penetration in dense plasma

    SciTech Connect

    Parks, P. B.; Cowan, T. E.

    2007-01-15

    Relativistic electrons are efficiently generated when multiterawatt lasers focused to ultrahigh intensities > or approx. 10{sup 19} W/cm{sup 2} illuminate the surface of dense plasma targets. A theoretical study finds that during typical picosecond pulse widths, significant amounts of Dreicer produced runaway electrons can build up due to the high axial electric field driving the neutralizing return current. An important consequence is that there will be a conversion of plasma current to runaway electron current, which is maximized at some optimum value of the beam-to-plasma density ratio N{sub b}=n{sub b}/n{sub e}, depending on the plasma collisionality. At collisionalities representative of solid target experiments, complete conversion to runaway electrons can only take place over a certain range of N{sub b} values. At higher collisionalities and pulse widths, applicable to the fast ignition concept for inertial confinement fusion, it was found that conversion to runaways has a peak at {approx}90% around N{sub b}{approx}0.06. Significant lessening of target material heating by Joule current dissipation is also possible, since part of the beam energy loss is transferred through the electric field directly to the formation of energetic runaways. Implications for beam transport inhibition by the electric field are also discussed.

  18. Direct Shear Failure in Reinforced Concrete Beams under Impulsive Loading

    DTIC Science & Technology

    1983-09-01

    failures in reinforced concrete under static loads are realized in specimens for which the ratio of shear span to effective depth (M/Vd) is less than O.Z...AFWL-TR-83-84 AFWL-TR- Ŝ, 83-84 000 DIRECT SHEAR FAILURE IN REINFORCED CONCRETE BEAMS UNDER IMPULSIVE LOADING Dr Timothy J. Ross September 1983...S TYP or 1116100 t PE& IGO 1OVRC DIRECT SHEAR FAILURE IN REINFORCED CONCRETE BEAMS Final Report UNDER IMPULSIVE LOADING 4. PEROMING.,OO.qEPORT NUMSER

  19. Ion Beam Analysis applied to laser-generated plasmas

    NASA Astrophysics Data System (ADS)

    Cutroneo, M.; Macková, A.; Havranek, V.; Malinsky, P.; Torrisi, L.; Kormunda, M.; Barchuk, M.; Ullschmied, J.; Dudzak, R.

    2016-04-01

    This paper presents the research activity on Ion Beam Analysis methods performed at Tandetron Laboratory (LT) of the Institute of Nuclear Physics AS CR, Rez, Czech Republic. Recently, many groups are paying attention to implantation by laser generated plasma. This process allows to insert a controllable amount of energetic ions into the surface layers of different materials modifying the physical and chemical properties of the surface material. Different substrates are implanted by accelerated ions from plasma through terawatt iodine laser, at nominal intensity of 1015 W/cm2, at the PALS Research Infrastructure AS CR, in the Czech Republic. This regime of the laser matter interaction generates, multi-MeV proton beams, and multi-charged ions that are tightly confined in time (hundreds ps) and space (source radius of a few microns). These ion beams have a much lower transverse temperature, a much shorter duration and a much higher current than those obtainable from conventional accelerators. The implementation of protons and ions acceleration driven by ultra-short high intensity lasers is exhibited by adopting suitable irradiation conditions as well as tailored targets. An overview of implanted targets and their morphological and structural characterizations is presented and discussed.

  20. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    SciTech Connect

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-27

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  1. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-01

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  2. Intense ion beam generation, plasma radiation source and plasma opening switch research

    NASA Astrophysics Data System (ADS)

    Hammer, D. A.; Coleman, M. D.; Qi, N.; Similon, P. L.; Sudan, R. N.

    1989-04-01

    This report describes research on intense ion beam diodes, plasma opening switches and dense z-pinch plasma radiators. Laser induced fluorescence spectroscopy has been used to map the electrostatic potential profile in a plasma-prefilled magnetically insulated ion diode. In a simple planar diode, the measured profile is inconsistent with the electrons being confined in a sheath near the cathode by the magnetic field. Rather, the profile implies the presence of electrons throughout the accelerating gap. A theoretical model of the penetration of current and magnetic field into a plasma, and of the current-driven effective collision frequency has been developed. The snowplow action of the rising magnetic field causes a steep rise in the plasma density at the leading edge. The subsequent multistreaming of the ions caused by ion reflection at the current layer could lead to ion heating through collective effects. The two-dimensional electron flow in the plasma cathode vacuum gap is also treated. Dense z-pinch plasma radiation source experiments have been initiated on the LION accelerator using gas puff and fine wire loads. The x-pinch was found to be a more effective way to generate soft x-rays than a single wire pinch or a gas puff implosion. Plasma opening switch experiments being initiated, and plasma anode ion diode development work being terminated are also briefly described.

  3. Crossed-beam energy transfer in direct-drive implosions

    SciTech Connect

    Seka, W; Edgell, D H; Michel, D T; Froula, D H; Goncharov, V N; Craxton, R S; Divol, L; Epstein, R; Follett, R; Kelly, J H; Kosc, T Z; Maximov, A V; McCrory, R L; Meyerhofer, D D; Michel, P; Myatt, J F; Sangster, T C; Shvydky, A; Skupsky, S; Stoeckl, C

    2012-05-22

    Direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have showed discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicate the presence of a mechanism that reduces laser coupling efficiency by 10%-20%. This appears to be due to crossed-beam energy transfer (CBET) that involves electromagnetic-seeded, low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of the incoming light beam to outgoing light, reducing the laser absorption and hydrodynamic efficiency of implosions. One-dimensional hydrodynamic simulations including CBET show good agreement with all observables in implosion experiments on OMEGA. Three strategies to mitigate CBET and improve laser coupling are considered: the use of narrow beams, multicolor lasers, and higher-Z ablators. Experiments on OMEGA using narrow beams have demonstrated improvements in implosion performance.

  4. Theory of beam-plasma instability in a periodic plasma-filled waveguide.

    PubMed

    Zaginaylov, G I; Rozhkov, A A; Raguin, J Y

    1999-12-01

    The beam-plasma wave interaction in a periodic plasma-filled waveguide is treated in a mathematically correct manner on the basis of the integral equation (IE) method. It has been shown that the relevant boundary-value problem could be reduced to an IE with a singular kernel for the longitudinal component of the electric field on the waveguide axis. The regularization of the IE was performed by extracting the static part of the kernel. The resulting IE of the second kind with a regular kernel, being rather convenient for a numerical analysis, is treated in a quasistatic approximation as a spectral problem. First-order expressions for eigenfunctions, and an infinite set of dispersion relations linking a wave number and frequency of plasma oscillations which separate radial branches of plasma oscillations from axial ones, have been obtained in the closed analytical form, thus enabling us to avoid the problem with the so-called "dense" spectrum. The solutions of the relevant "cold" dispersion relations establish a periodical dependence of the frequency on the wave number over several periods within the accuracy of order of the neglected terms. In the presence of an electron beam they turn out to be unstable near frequencies providing the resonances of the beam with spatial plasma harmonics. Evaluations of the instability saturation level predict a more efficient beam-plasma wave energy transfer compared with those following from a conventional theoretical analysis based on the formulation of a dispersion relation in terms of an infinite determinant, with following truncation of the latter to the finite sized relation.

  5. Long-range attraction of an ultrarelativistic electron beam by a column of neutral plasma

    NASA Astrophysics Data System (ADS)

    Adli, E.; Lindstrøm, C. A.; Allen, J.; Clarke, C. I.; Frederico, J.; Gessner, S. J.; Green, S. Z.; Hogan, M. J.; Litos, M. D.; O'Shea, B.; Yakimenko, V.; An, W.; Clayton, C. E.; Marsh, K. A.; Mori, W. B.; Joshi, C.; Vafaei-Najafabadi, N.; Corde, S.; Lu, W.

    2016-10-01

    We report on the experimental observation of the attraction of a beam of ultrarelativistic electrons towards a column of neutral plasma. In experiments performed at the FACET test facility at SLAC we observe that an electron beam moving parallel to a neutral plasma column, at an initial distance of many plasma column radii, is attracted into the column. Once the beam enters the plasma it drives a plasma wake similar to that of an electron beam entering the plasma column head-on. A simple analytical model is developed in order to capture the essential physics of the attractive force. The attraction is further studied by 3D particle-in-cell numerical simulations. The results are an important step towards better understanding of particle beam-plasma interactions in general and plasma wakefield accelerator technology in particular.

  6. Laser induced focusing for over-dense plasma beams

    SciTech Connect

    Schmidt, Peter; Boine-Frankenheim, Oliver; Mulser, Peter

    2015-09-15

    The capability of ion acceleration with high power, pulsed lasers has become an active field of research in the past years. In this context, the radiation pressure acceleration (RPA) mechanism has been the topic of numerous theoretical and experimental publications. Within that mechanism, a high power, pulsed laser beam hits a thin film target. In contrast to the target normal sheath acceleration, the entire film target is accelerated as a bulk by the radiation pressure of the laser. Simulations predict heavy ion beams with kinetic energy up to GeV, as well as solid body densities. However, there are several effects which limit the efficiency of the RPA: On the one hand, the Rayleigh-Taylor-instability limits the predicted density. On the other hand, conventional accelerator elements, such as magnetic focusing devices are too bulky to be installed right after the target. Therefore, we present a new beam transport method, suitable for RPA-like/over-dense plasma beams: laser induced focusing.

  7. Neutral beam heating of a RFP plasma in MST

    SciTech Connect

    Waksman, J.; Anderson, J. K.; Nornberg, M. D.; Parke, E.; Reusch, J. A.; Liu, D.; Fiksel, G.; Davydenko, V. I.; Ivanov, A. A.; Stupishin, N.; Deichuli, P. P.; Sakakita, H.

    2012-12-15

    Electron temperature is observed to rise due to neutral beam injection (NBI) in the Madison Symmetric Torus (MST). Heating is observed to be 100 {+-} 50 eV in the core of 200 kA plasmas. This is the first definitive measurement of auxiliary heating of a reversed-field pinch (RFP). This heating is consistent with a 1D classical model which was developed. This 1D model calculates the evolving thermal conductivity and ohmic power input profiles during enhanced confinement, and can calculate NBI deposition and classical fast ion diffusion and slowing. The predicted temperature change is consistent with measured beam heating both during and after enhanced confinement, which is consistent with previous observations that fast ions are well confined and behave roughly classically in the RFP.

  8. Self-focusing of electromagnetic pulsed beams in collisional plasmas

    SciTech Connect

    Faisal, Mohammad; Verma, M. P.; Sodha, Mahendra Singh

    2008-10-15

    In this paper, the self-focusing of an electromagnetic pulsed beam in a collisional plasma has been investigated in the paraxial approximation, following the formalism developed by Akhmanov. The energy balance equation for electrons, the equation expressing the equality of pressure gradient (of electrons and ions) to the force due to space charge field, and the equation for the beam width parameter f (obtained by following Akhmanov's approach) have been simultaneously solved for given initial (z=0) time profile of the pulse to obtain f as a function of {xi} (cz/{omega}r{sub 0}{sup 2}) and t{sup '}=t-z/V{sub g}, where V{sub g} is the group velocity. Both Gaussian and sine time profiles of the pulse have been investigated.

  9. Propagation of a nonrelativistic electron beam in a plasma in a magnetic field

    SciTech Connect

    Okuda, H.; Horton, R.; Ono, M.; Ashour-Abdalla, M.

    1986-10-01

    Propagation of a nonrelativistic electron beam in a plasma in a strong magnetic field has been studied using electrostatic one-dimensional particle simulation models. Electron beams of finite pulse length and of continuous injection are followed in time to study the effects of beam-plasma interaction on the beam propagation. For the case of pulsed beam propagation, it is found that the beam distribution rapidly spreads in velocity space generating a plateaulike distribution with a high energy tail extending beyond the initial beam velocity.

  10. Ultracold electron bunch generation via plasma photocathode emission and acceleration in a beam-driven plasma blowout.

    PubMed

    Hidding, B; Pretzler, G; Rosenzweig, J B; Königstein, T; Schiller, D; Bruhwiler, D L

    2012-01-20

    Beam-driven plasma wakefield acceleration using low-ionization-threshold gas such as Li is combined with laser-controlled electron injection via ionization of high-ionization-threshold gas such as He. The He electrons are released with low transverse momentum in the focus of the copropagating, nonrelativistic-intensity laser pulse directly inside the accelerating or focusing phase of the Li blowout. This concept paves the way for the generation of sub-μm-size, ultralow-emittance, highly tunable electron bunches, thus enabling a flexible new class of an advanced free electron laser capable high-field accelerator.

  11. Self-generated magnetic dipoles in weakly magnetized beam-plasma system.

    PubMed

    Jia, Qing; Mima, Kunioki; Cai, Hong-bo; Taguchi, Toshihiro; Nagatomo, Hideo; He, X T

    2015-02-01

    A self-generation mechanism of magnetic dipoles and the anomalous energy dissipation of fast electrons in a magnetized beam-plasma system are presented. Based on two-dimensional particle-in-cell simulations, it is found that the magnetic dipoles are self-organized and play important roles in the beam electron energy dissipation. These dipoles drift slowly in the direction of the return flow with a quasisteady velocity, which depends upon the magnetic amplitude of the dipole and the imposed external magnetic field. This dipole formation provides a mechanism for the anomalous energy dissipation of a relativistic electron beam, which would play an important role in collisionless shock and ion shock acceleration.

  12. Collimated multi-MeV ion beams from high-intensity laser interactions with underdense plasma.

    PubMed

    Willingale, L; Mangles, S P D; Nilson, P M; Clarke, R J; Dangor, A E; Kaluza, M C; Karsch, S; Lancaster, K L; Mori, W B; Najmudin, Z; Schreiber, J; Thomas, A G R; Wei, M S; Krushelnick, K

    2006-06-23

    A beam of multi-MeV helium ions has been observed from the interaction of a short-pulse high-intensity laser pulse with underdense helium plasma. The ion beam was found to have a maximum energy for He2+ of (40(+3)(-8)) MeV and was directional along the laser propagation path, with the highest energy ions being collimated to a cone of less than 10 degrees. 2D particle-in-cell simulations show that the ions are accelerated by a sheath electric field that is produced at the back of the gas target. This electric field is generated by transfer of laser energy to a hot electron beam, which exits the target generating large space-charge fields normal to its boundary.

  13. Electron beam generated whistler emissions in a laboratory plasma

    SciTech Connect

    Van Compernolle, B. Pribyl, P.; Gekelman, W.; An, X.; Bortnik, J.; Thorne, R. M.

    2015-12-10

    Naturally occurring whistler mode emissions in the magnetosphere, are important since they are responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Recently, we reported on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced [1]. A beam of energetic electrons is launched into a cold plasma and excites both chirping whistler waves and broadband waves. Here we extend our previous analysis by comparing the properties of the broadband waves with linear theory.

  14. Probabilistic model of beam-plasma interaction in randomly inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Krasnoselskikh, Vladimir; Voshchepynets, Andrii; Artemyev, Anton

    2014-05-01

    We study beam-plasma interaction in the presence of random density fluctuations. The level of fluctuations is supposed to be high but Langmuir waves generated by the beam instability are supposed to be not trapped inside the density depletions. This system can be considered as a good approximation of beam-plasma interaction in the solar wind. We describe the system in terms of probability density for the density fluctuations that determines the probability density for wave phase velocities during wave propagation. We suppose that at each moment of time an electron can interact only with one single wave having the phase velocity equal to its velocity or do not interact at all. We suppose that the amplitudes and electron distribution functions vary slowly with respect to single wave-particle interaction that allows one to average over a large number of interactions. This allows one to write Smoluhovsky equation for probability for particle having velocity V0 at time t0 to have velocity V at time t. From this description one can obtain Kolmogorov-Feller equation for slow variations of electron distribution function similar to the diffusion equation in quasilinear approximation. This probabilistic approach allows finding out the dependence of diffusion coefficients on statistical distribution of plasma density fluctuations. We use Liouville equation to describe the evolution of the Langmuir wave's spectral power, for each single wave. To describe slow evolution of the wave power we use averaged wave growth rate. It is obtained from the probability for the wave to have the resonant velocity on the interval. The equations obtained are solved numerically. We evaluate the influence of the density inhomogeneities on the beam relaxation time. As a result the length of relaxation of the electron beam in such inhomogeneous plasma is much longer than in homogeneous case and our goal is to determine the dependence of this length on characteristics of the statistical properties

  15. Probabilistic Model of Beam-Plasma Interaction in Randomly Inhomogeneous Plasma

    NASA Astrophysics Data System (ADS)

    Krasnoselskikh, V.; Voshchepynets, A.; Volokitin, A.; Artemyev, A.

    2014-12-01

    We study beam-plasma interaction in the presence of random density fluctuations. The level of fluctuations is supposed to be high but Langmuir waves generated by the beam instability are supposed to be not trapped inside the density depletions. This system can be considered as a good approximation of beam-plasma interaction in the solar wind. We describe the system in terms of probability density for the density fluctuations that determines the probability density for wave phase velocities during wave propagation. We suppose that at each moment of time an electron can interact only with one single wave having the phase velocity equal to its velocity or do not interact at all. We suppose that the amplitudes and electron distribution functions vary slowly with respect to single wave-particle interaction that allows one to average over a large number of interactions. This allows one to write Smoluhovsky equation for probability for particle having velocity V0 at time t0 to have velocity V at time t. From this description one can obtain Kolmogorov-Feller equation for slow variations of electron distribution function similar to the diffusion equation in quasilinear approximation. This probabilistic approach allows finding out the dependence of diffusion coefficients on statistical distribution of plasma density fluctuations. We use Liouville equation to describe the evolution of the Langmuir wave's spectral power, for each single wave. To describe slow evolution of the wave power we use averaged wave growth rate. It is obtained from the probability for the wave to have the resonant velocity on the interval. The equations obtained are solved numerically. We evaluate the influence of the density inhomogeneities on the beam relaxation time. As a result the length of relaxation of the electron beam in such inhomogeneous plasma is much longer than in homogeneous case and our goal is to determine the dependence of this length on characteristics of the statistical properties

  16. Plasma convection and ion beam generation in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.; Smith, R. A.

    1991-01-01

    Because of the dawn-dusk electric field E(dd), plasma in the magnetotail convects from the lobe toward the central plasma sheet (CPS). In the absence of space or velocity diffusion due to plasma turbulence, convection would yield a steady state distribution function f = V exp (-2/3) g(v exp 2 V exp 2/3), where V is the flux tube volume. Starting with such a distribution function and a plasma beta which varies from beta greater than 1 in the CPS to beta much smaller than 1 in the lobe, the evolution of the ion distribution function was studied considering the combined effects of ion diffusion by kinetic Alfven waves (KAW) in the ULF frequency range (1-10 mHz) and convection due to E(dd) x B drift in the plasma sheet boundary layer (PSBL) and outer central plasma sheet (OCPS). The results show that, during the early stages after launching the KAWs, a beamlike ion distribution forms in the PSBL and at the same time the plasma density and temperature decrease in the OCPS. Following this stage, ions in the beams convect toward the CPS resulting in an increase of the plasma temperature in the OCPS.

  17. Recent results from studies of electron beam phenomena in space plasmas

    NASA Technical Reports Server (NTRS)

    Neubert, Torsten; Banks, Peter M.

    1992-01-01

    The paper examines selected results from experiments, performed in 1980s, involving the ejection of beams of electrons from spacecraft. Special attention is given to the basic processes associated with the spacecraft charging, passive current collection, beam-atmosphere interactions, beam-plasma interactions, and neutral gas emission. Consideration is also given to future experiments on active electron beam ejections in space.

  18. Preferential acceleration and magnetic field enhancement in plasmas with e+/e- beam injection

    NASA Astrophysics Data System (ADS)

    Huynh, Cong Tuan; Ryu, Chang-Mo

    2016-03-01

    A theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e+/e- beam injection is presented. When the e+/e- beams are injected into a plasma, current filaments are formed. The beam particles are accelerated or decelerated depending on the types of current filaments in which they are trapped. It is found that in the electron/ion ambient plasma, the e+ beam particles are preferentially accelerated, while the e- beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e+/e- plasma. We also find that the particle momentum decrease can explain the magnetic field increase during the development of Weibel/filamentation instability. Supporting simulation results of particle acceleration/deceleration and magnetic field enhancement are presented. Our findings can be applied to a wide range of astrophysical plasmas with the e+/e- beam injection.

  19. High-directivity emissions with flexible beam numbers and beam directions using gradient-refractive-index fractal metamaterial.

    PubMed

    Xu, He-Xiu; Wang, Guang-Ming; Tao, Zui; Cui, Tie Jun

    2014-07-18

    A three-dimensional (3D) highly-directive emission system is proposed to enable beam shaping and beam steering capabilities in wideband frequencies. It is composed of an omnidirectional source antenna and several 3D gradient-refractive-index (GRIN) lenses. To engineer a broadband impedance match, the design method for these 3D lenses is established under the scenario of free-space excitation by using a planar printed monopole. For realizations and demonstrations, a kind of GRIN metamaterial is proposed, which is constructed by non-uniform fractal geometries. Due to the non-resonant and deep-subwavelength features of the fractal elements, the resulting 3D GRIN metamaterial lenses have extra wide bandwidth (3 to 7.5 GHz), and are capable of manipulating electromagnetic wavefronts accurately, advancing the state of the art of available GRIN lenses. The proposal for the versatile highly-directive emissions has been confirmed by simulations and measurements, showing that not only the number of beams can be arbitrarily tailored but also the beam directions can be steerable. The proposal opens a new way to control broadband highly-directive emissions with pre-designed directions, promising great potentials in modern wireless communication systems.

  20. High-Directivity Emissions with Flexible Beam Numbers and Beam Directions Using Gradient-Refractive-Index Fractal Metamaterial

    PubMed Central

    Xu, He-Xiu; Wang, Guang-Ming; Tao, Zui; Cui, Tie Jun

    2014-01-01

    A three-dimensional (3D) highly-directive emission system is proposed to enable beam shaping and beam steering capabilities in wideband frequencies. It is composed of an omnidirectional source antenna and several 3D gradient-refractive-index (GRIN) lenses. To engineer a broadband impedance match, the design method for these 3D lenses is established under the scenario of free-space excitation by using a planar printed monopole. For realizations and demonstrations, a kind of GRIN metamaterial is proposed, which is constructed by non-uniform fractal geometries. Due to the non-resonant and deep-subwavelength features of the fractal elements, the resulting 3D GRIN metamaterial lenses have extra wide bandwidth (3 to 7.5 GHz), and are capable of manipulating electromagnetic wavefronts accurately, advancing the state of the art of available GRIN lenses. The proposal for the versatile highly-directive emissions has been confirmed by simulations and measurements, showing that not only the number of beams can be arbitrarily tailored but also the beam directions can be steerable. The proposal opens a new way to control broadband highly-directive emissions with pre-designed directions, promising great potentials in modern wireless communication systems. PMID:25034268

  1. Laser assisted direct write process with novel beam profiles

    NASA Astrophysics Data System (ADS)

    Shang, Shuo; Wellburn, Dan; Fearon, Eamonn; Yan, Shilian; Edwardson, Stuart; Dearden, G.; Watkins, K. G.

    2013-05-01

    The Laser Assisted Direct Write (LADW) method can be used to generate electrical circuitry on a substrate by depositing metallic ink and curing the ink thermally with a laser. Compared to conventional oven curing, laser curing can be used in-situ, over complicated 3D contours, and selectively cure over heat sensitive substrates. The intensity distribution of the laser beam used has significant influence on many surface heating processes. A conventional Gaussian beam would lead to uneven heating across the beam path. To overcome this issue, Wellburn has designed a novel beam shaping device, which allows one to convert a Gaussian beam profile into an annular ring with a variable level of central plateau fill [1]. Shang et al. have developed and verified a predictive Finite Element Method (FEM) model to simulate the laser curing process for a generic combination of processing parameters. Laser modes can be flexibly varied within this model. Hence it can be used to predict the performance of curing with differently intensity distributions. This study investigates the curing process under different intensity profiles obtained with the beam shaping device. Electrical resistivity and scratch resistance of cured samples are tested as measures of the curing quality achieved. Results obtained are then compared with the FEM model predictions, and indicate the best intensity distribution for this particular application.

  2. Guiding of laser beams in plasmas by electromagnetic cascade compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, S.; Shvets, G.

    2006-10-01

    The near-resonant beatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few- femtosecond electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the difference frequency. As a result, the cascade of sidebands red- and blue-shifted by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser phase, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. Thus, a train of high intensity radiation spikes with continually evolving longitudinal profile can be self- guided over several Rayleigh lengths in homogeneous plasma. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW show that achieving GeV energy is possible under realistic experimental conditions.

  3. A simulation study of radial expansion of an electron beam injected into an ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Koga, J.; Lin, C. S.

    1994-01-01

    Injections of nonrelativistic electron beams from a finite equipotential conductor into an ionospheric plasma have been simulated using a two-dimensional electrostatic particle code. The purpose of the study is to survey the simulation parameters for understanding the dependence of beam radius on physical variables. The conductor is charged to a high potential when the background plasma density is less than the beam density. Beam electrons attracted by the charged conductor are decelerated to zero velocity near the stagnation point, which is at a few Debye lengths from the conductor. The simulations suggest that the beam electrons at the stagnation point receive a large transverse kick and the beam expands radially thereafter. The buildup of beam electrons at the stagnation point produces a large electrostatic force responsible for the transverse kick. However, for the weak charging cases where the background plasma density is larger than the beam density, the radial expansion mechanism is different; the beam plasma instability is found to be responsible for the radial expansion. The simulations show that the electron beam radius for high spacecraft charging cases is of the order of the beam gyroradius, defined as the beam velocity divided by the gyrofrequency. In the weak charging cases, the beam radius is only a fraction of the beam gyroradius. The parameter survey indicates that the beam radius increases with beam density and decreases with magnetic field and beam velocity. The beam radius normalized by the beam gyroradius is found to scale according to the ratio of the beam electron Debye length to the ambient electron Debye length. The parameter dependence deduced would be useful for interpreting the beam radius and beam density of electron beam injection experiments conducted from rockets and the space shuttle.

  4. Beat wave excitation of electron plasma wave by relativistic cross focusing of cosh-Gaussian laser beams in plasma

    NASA Astrophysics Data System (ADS)

    Singh, Arvinder; Gupta, Naveen

    2015-06-01

    A scheme for beat wave excitation of electron plasma wave (EPW) is proposed by relativistic cross-focusing of two coaxial Cosh-Gaussian (ChG) laser beams in an under dense plasma. The plasma wave is generated on account of beating of two coaxial laser beams of frequencies ω1 and ω2 . The mechanism for laser produced nonlinearity is assumed to be relativistic nonlinearity in electron mass. Following moment theory approach in Wentzel Kramers Brillouin (W.K.B) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The relativistic nonlinearity depends not only on the intensity of first laser beam but also on the intensity of second laser beam. Therefore, propagation dynamics of one laser beam affect that of second beam and hence cross-focusing of the two laser beams takes place. Due to non uniform intensity distribution of pump laser beams, the background electron concentration gets modified. The amplitude of EPW, which depends on the background electron concentration, thus gets nonlinearly coupled with the laser beams. The effects of relativistic electron mass nonlinearity and the cross-focusing of pump beams on excitation of EPW have been incorporated. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW.

  5. Plasma-Enhanced Chemical Vapor Deposition of SiOx Films Using Electron Beam Generated Plasmas

    DTIC Science & Technology

    2009-09-28

    special relation to the substrate or e-beam. A total flow of 100 sccm was used in all cases . For the gas flows mentioned above, the individual flows...beam generated plasmas. In this case , molecular hydrogen, formed primarily by recombination of atomic hydrogen on system walls, will not be...the films was large (> 130 nm/min), which implied a high porosity for all cases except for low TEOS flow (≤ 2 sccm) at the higher (300 °C) temperature

  6. Interaction of nonthermal muon beam with electron-positron-photon plasma: A thermal field theory approach

    SciTech Connect

    Noorian, Zainab; Eslami, Parvin; Javidan, Kurosh

    2013-11-15

    Interaction of a muon beam with hot dense QED plasma is investigated. Plasma system contains electrons and positrons with Fermi-Dirac distribution and Bose-Einstein distributed photons while the beam particles have nonthermal distribution. The energy loss of the beam particles during the interaction with plasma is calculated to complete leading order of interaction in terms of the QED coupling constant using thermal field theory approach. The screening effects of the plasma are computed consistently using resummation of perturbation theory with hard thermal loop approximation according to the Braaten-Pisarski method. Time evolution of the plasma characteristics and also plasma identifications during the interaction are investigated. Effects of the nonthermal parameter of the beam distribution on the energy exchange and the evolution of plasma-beam system are also explained.

  7. Optical observations of the beam-plasma discharge phenomenon

    NASA Technical Reports Server (NTRS)

    Sivjee, G. G.; Hamwey, R. M.; Hallinan, T. J.

    1993-01-01

    Spectroscopic observations of optical emissions from the beam-plasma discharge (BPD) phenomenon were made with NASA's vacuum chamber facility, at the Johnson Space Center, configured to simulate the physical conditions of magnetospheric electron beam injection into the ionospheric/upper-atmospheric environment. Nonlinear N2 and N2(+) optical emission growth rates (with respect to incremental electron beam current values) were observed from the chamber gas during transition to the BPD state. For electron-beam currents (I) near the BPD transition value (I(sub c)), the band emissions from the chamber gas produced by relatively low energy (less than or equal to 50 eV) electrons interacting with N2 were anomalously more intense than those requiring higher energy (greater than 100 eV) electrons to excite them. For I more greater than I(sub c), the optical emissions increased linearly with I (as was the case for I less than I(sub c)) and their ratios decreased significantly from the peak values attained when I approximately equals I(sub c). These observations suggest that during BPD some of the energy of the primary electron beam is efficiently transferred, via wave-particle interactions, to local electrons produced through ionization of the chamber gas; the resulting suprathermal electrons provide an additional source of excitation for the relatively low energy states (A, B and C) of N2. Such nonlinear excitation of upper atmospheric gas may occur in certain auroral events wherein the current due to the precipitating electrons approaches a value close to I(sub c).

  8. EXPERIMENTS ON LASER AND E-BEAM TRANSPORT AND INTERACTION IN A PLASMA CHANNEL.

    SciTech Connect

    POGORELSKY,I.V.; PAVLISHIN,I.V.; BEN-ZVI,I.; ET AL.

    2004-09-15

    An ablative capillary discharge is installed into a linac beamline and serves as a plasma source for generating and characterizing wakefields. Simultaneously, the electron beam is used as a tool for plasma diagnostics. A high-energy picosecond CO{sub 2} laser channeled within the same capillary strongly affects a counterpropagating electron beam. These observations, supported with simulations, suggest the possibility of manipulating relativistic electron beams by steep plasma channels ponderomotively produced by a laser.

  9. Simulation study of interactions of Space Shuttle-generated electron beams with ambient plasmas

    NASA Technical Reports Server (NTRS)

    Lin, Chin S.

    1992-01-01

    This report summarizes results obtained through the support of NASA Grant NAGW-1936. The objective of this report is to conduct large scale simulations of electron beams injected into space. The topics covered include the following: (1) simulation of radial expansion of an injected electron beam; (2) simulations of the active injections of electron beams; (3) parameter study of electron beam injection into an ionospheric plasma; and (4) magnetosheath-ionospheric plasma interactions in the cusp.

  10. Production of intense ion beams in a reflex triode with an external plasma source at the anode

    SciTech Connect

    Bystritskii, V.M.; Verigin, A.A.; Volkov, S.N.; Krasik, Y.E.; Podkatov, V.I.

    1986-09-01

    An experimental study of the production of intense ion beams in a reflex triode with an external plasma source at the anode is reported. The ions had various ratios Z/M. When the anode plasma is produced in a preliminary charging pulse of the accelerator, the plasma density is too low for operation under charge-limited emission conditions. In this case, an ion beam is observed to be produced from the plasma formed by the direct heating of the anode material by oscillating electrons. When an anode plasma resulting from the breakdown of a dielectric insert or of the vacuum gap of a composite andode by an external voltage source is used to produce an ion beam, the reflex triode operating conditions depend on delaying the operation of the accelerator with respect to the external source. The highest efficiency (approx. =20%) in the production of an ion beam is observed at t/sub d/ = 3--6 ..mu..s. In this case, the reflex triode operates under increasing or constant impedance conditions. It was shown in the course of the experiments that the ion beam which is produced is nonuniform. There are three groups of ions: H/sup +/, C/sup n//sup +/, and Cu/sup n//sup +/. The energy of the heavy ions depends on the applied anode potential. The different mass components of the ion beam do not appear at the same time. The macroscopic divergence of the beam is 4--6/sup 0/ at the periphery and drops off to approx. <1/sup 0/ at the center. The microscopic divergence of the beam is 3/sup 0/. The total energy of the ion beam which is produced is less than 120 J at an average current approx. =2.8 kA.

  11. Engineering of beam direct conversion for a 120-kV, 1-MW ion beam

    NASA Technical Reports Server (NTRS)

    Barr, W. L.; Doggett, J. N.; Hamilton, G. W.; Kinney, J. D.; Moir, R. W.

    1977-01-01

    Practical systems for beam direct conversion are required to recover the energy from ion beams at high efficiency and at very high beam power densities in the environment of a high-power neutral-injection system. Such an experiment is now in progress using a 120-kV beam with a maximum total current of 20 A. After neutralization, the H(+) component to be recovered will have a power of approximately 1 MW. A system testing these concepts has been designed and tested at 15 kV, 2 kW in preparation for the full-power tests. The engineering problems involved in the full-power tests affect electron suppression, gas pumping, voltage holding, diagnostics, and measurement conditions. Planning for future experiments at higher power includes the use of cryopumping and electron suppression by a magnetic field rather than by an electrostatic field. Beam direct conversion for large fusion experiments and reactors will save millions of dollars in the cost of power supplies and electricity and will dispose of the charged beam under conditions that may not be possible by other techniques.

  12. Calibration of Laser Beam Direction for Inner Diameter Measuring Device

    PubMed Central

    Yang, Tongyu; Wang, Zhong; Wu, Zhengang; Li, Xingqiang; Wang, Lei; Liu, Changjie

    2017-01-01

    The laser triangulation method is one of the most advanced methods for large inner diameter measurement. Our research group proposed a kind of inner diameter measuring device that is principally composed of three laser displacement sensors known to be fixed in the same plane measurement position. It is necessary to calibrate the direction of the laser beams that are emitted by laser displacement sensors because they do not meet the theoretical model accurately. For the purpose of calibrating the direction of laser beams, a calibration method and mathematical model were proposed. The inner diameter measuring device is equipped with the spindle of the machine tool. The laser beams rotate and translate in the plane and constitute the rotary rays which are driven to scan the inner surface of the ring gauge. The direction calibration of the laser beams can be completed by the sensors’ distance information and corresponding data processing method. The corresponding error sources are analyzed and the validity of the method is verified. After the calibration, the measurement error of the inner diameter measuring device reduced from ±25 μm to ±15 μm and the relative error was not more than 0.011%. PMID:28165432

  13. Calibration of Laser Beam Direction for Inner Diameter Measuring Device.

    PubMed

    Yang, Tongyu; Wang, Zhong; Wu, Zhengang; Li, Xingqiang; Wang, Lei; Liu, Changjie

    2017-02-05

    The laser triangulation method is one of the most advanced methods for large inner diameter measurement. Our research group proposed a kind of inner diameter measuring device that is principally composed of three laser displacement sensors known to be fixed in the same plane measurement position. It is necessary to calibrate the direction of the laser beams that are emitted by laser displacement sensors because they do not meet the theoretical model accurately. For the purpose of calibrating the direction of laser beams, a calibration method and mathematical model were proposed. The inner diameter measuring device is equipped with the spindle of the machine tool. The laser beams rotate and translate in the plane and constitute the rotary rays which are driven to scan the inner surface of the ring gauge. The direction calibration of the laser beams can be completed by the sensors' distance information and corresponding data processing method. The corresponding error sources are analyzed and the validity of the method is verified. After the calibration, the measurement error of the inner diameter measuring device reduced from ± 25 μ m to ± 15 μ m and the relative error was not more than 0.011%.

  14. Feedback control of plasma instabilities with charged particle beams and study of plasma turbulence

    NASA Technical Reports Server (NTRS)

    Tham, Philip Kin-Wah

    1994-01-01

    A new non-perturbing technique for feedback control of plasma instabilities has been developed in the Columbia Linear Machine (CLM). The feedback control scheme involves the injection of a feedback modulated ion beam as a remote suppressor. The ion beam was obtained from a compact ion beam source which was developed for this purpose. A Langmuir probe was used as the feedback sensor. The feedback controller consisted of a phase-shifter and amplifiers. This technique was demonstrated by stabilizing various plasma instabilities to the background noise level, like the trapped particle instability, the ExB instability and the ion-temperature-gradient (ITG) driven instability. An important feature of this scheme is that the injected ion beam is non-perturbing to the plasma equilibrium parameters. The robustness of this feedback stabilization scheme was also investigated. The principal result is that the scheme is fairly robust, tolerating about 100% variation about the nominal parameter values. Next, this scheme is extended to the unsolved general problem of controlling multimode plasma instabilities simultaneously with a single sensor-suppressor pair. A single sensor-suppressor pair of feedback probes is desirable to reduce the perturbation caused by the probes. Two plasma instabilities the ExB and the ITG modes, were simultaneously stabilized. A simple 'state' feedback type method was used where more state information was generated from the single sensor Langmuir probe by appropriate signal processing, in this case, by differentiation. This proof-of-principle experiment demonstrated for the first time that by designing a more sophisticated electronic feedback controller, many plasma instabilities may be simultaneously controlled. Simple theoretical models showed generally good agreement with the feedback experimental results. On a parallel research front, a better understanding of the saturated state of a plasma instability was sought partly with the help of feedback

  15. Density and potential measurements in an intense ion-beam-generated plasma

    SciTech Connect

    Abt, N.E.

    1982-05-01

    Neutral beams are created by intense large area ion beams which are neutralized in a gas cell. The interaction of the beam with the gas cell creates a plasma. Such a plasma is studied here. The basic plasma parameters, electron temperature, density, and plasma potential, are measured as a function of beam current and neutral gas pressure. These measurements are compared to a model based on the solution of Poisson's equation. Because of the cylindrical geometry the equation cannot be solved analytically. Details of the numerical method are presented.

  16. Collimated fast electron beam generation in critical density plasma

    SciTech Connect

    Iwawaki, T. Habara, H.; Morita, K.; Tanaka, K. A.; Baton, S.; Fuchs, J.; Chen, S.; Nakatsutsumi, M.; Rousseaux, C.; Filippi, F.; Nazarov, W.

    2014-11-15

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 10{sup 14 }W/cm{sup 2}, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 10{sup 14 }W/cm{sup 2}, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  17. Optical Device for Converting a Laser Beam into Two Co-aligned but Oppositely Directed Beams

    NASA Technical Reports Server (NTRS)

    Jennings, Donald

    2013-01-01

    Optical systems consisting of a series of optical elements require alignment from the input end to the output end. The optical elements can be mirrors, lenses, sources, detectors, or other devices. Complex optical systems are often difficult to align from end-to-end because the alignment beam must be inserted at one end in order for the beam to traverse the entire optical path to the other end. The ends of the optical train may not be easily accessible to the alignment beam. Typically, when a series of optical elements is to be aligned, an alignment laser beam is inserted into the optical path with a pick-off mirror at one end of the series of elements. But it may be impossible to insert the beam at an end-point. It can be difficult to locate the pick-off mirror at the desired position because there is not enough space, there is no mounting surface, or the location is occupied by a source, detector, or other component. Alternatively, the laser beam might be inserted at an intermediate location (not at an end-point) and sent, first in one direction and then the other, to the opposite ends of the optical system for alignment. However, in this case, alignment must be performed in two directions and extra effort is required to co-align the two beams to make them parallel and coincident, i.e., to follow the same path as an end-to-end beam. An optical device has been developed that accepts a laser beam as input and produces two co-aligned, but counter-propagating beams. In contrast to a conventional alignment laser placed at one end of the optical path, this invention can be placed at a convenient position within the optical train and aligned to send its two beams simultaneously along precisely opposite paths that, taken together, trace out exactly the same path as the conventional alignment laser. This invention allows the user the freedom to choose locations within the optical train for placement of the alignment beam. It is also self-aligned by design and requires

  18. Simulations of electromagnetic emissions produced in a thin plasma by a continuously injected electron beam

    NASA Astrophysics Data System (ADS)

    Annenkov, V. V.; Timofeev, I. V.; Volchok, E. P.

    2016-05-01

    In this paper, electromagnetic emissions produced in a thin beam-plasma system are studied using two-dimensional particle-in-cell simulations. For the first time, the problem of emission generation in such a system is considered in a realistic formulation allowing for the continuous injection of a relativistic electron beam through a plasma boundary. Specific attention is given to the thin plasma case in which the transverse plasma size is comparable to the typical wavelength of beam-driven oscillations. Such a case is often implemented in laboratory beam-plasma experiments and has a number of peculiarities. Emission from a thin plasma does not require intermediate generation of the electromagnetic plasma eigenmodes, as in an infinite case, and is more similar to the regular antenna radiation. In this work, we determine how efficiently the fundamental and the second harmonic emissions can be generated in previously modulated and initially homogeneous plasmas.

  19. Experimental beam system studies of plasma-polymer interactions

    NASA Astrophysics Data System (ADS)

    Nest, Dustin George

    Since the invention of the integrated circuit, the semiconductor industry has relied on the shrinking of device dimensions to increase device performance and decrease manufacturing costs. However, the high degree of roughening observed during plasma etching of current generation photoresist (PR) polymers can result in poor pattern transfer and ultimately decreased device performance or failure. Plasma-surface interactions are inherently difficult to study due to the highly coupled nature of the plasma enviroment. To better understand these interactions, a beam system approach is employed where polymers are exposed to beams of ions and vacuum ultraviolet (VUV) photons. Through the use of the beam system approach, simultaneous VUV radiation, ion bombardment, and moderate substrate heating have been identified as key elements, acting synergistically, as being responsible for roughening of current generation 193 nm PR during plasma processing. Sequential exposure is not adequate for the development of surface roughness, as observed through AFM and SEM. Ion bombardment results in the formation of a graphitized near-surface region with a depth of a few nanometers, the expected ion penetration depth of 150 eV argon ions. In contrast, VUV radiation results in the loss of carbon-oxygen bonds in the bulk PR as observed through Transmission FTIR. Based on the differing penetration depth of either ions or photons, their resulting chemical modifications, and the temperature dependence of the observed roughening, a mechanism is proposed based on stress relaxation resulting in surface buckling. The surface roughness of poly(4-methyl styrene) (P4MS) and poly(alpha-methyl styrene) (PalphaMS) have also been investigated under exposure to ions and VUV photons. PaMS degrades during VUV radiation above its ceiling temperature of ˜60°C. Despite having the same chemical composition as PalphaMS, P4MS does not degrade during VUV exposure at 70°C due to its relatively high ceiling

  20. Electron Beam Charge Diagnostics for Laser Plasma Accelerators

    SciTech Connect

    Nakamura, Kei; Gonsalves, Anthony; Lin, Chen; Smith, Alan; Rodgers, David; Donahue, Rich; Byrne, Warren; Leemans, Wim

    2011-06-27

    A comprehensive study of charge diagnostics is conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). First, a scintillating screen (Lanex) was extensively studied using subnanosecond electron beams from the Advanced Light Source booster synchrotron, at the Lawrence Berkeley National Laboratory. The Lanex was cross calibrated with an integrating current transformer (ICT) for up to the electron energy of 1.5 GeV, and the linear response of the screen was confirmed for charge density and intensity up to 160 pC/mm{sup 2} and 0.4 pC/(ps mm{sup 2}), respectively. After the radio-frequency accelerator based cross calibration, a series of measurements was conducted using electron beams from an LPA. Cross calibrations were carried out using an activation-based measurement that is immune to electromagnetic pulse noise, ICT, and Lanex. The diagnostics agreed within {+-}8%, showing that they all can provide accurate charge measurements for LPAs.

  1. Design Considerations for Plasma Accelerators Driven by Lasers or Particle Beams

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Benedetti, C.; Toth, Cs.; Geddes, C. G. R.; Leemans, W.P.

    2010-06-01

    Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. The implications for accelerator design and the different physical mechanisms of laser-driven and beam-driven plasma acceleration are discussed. Driver propagation is examined, as well as the effects of the excited plasma wave phase velocity. The driver coupling to subsequent plasma accelerator stages for high-energy physics applications is addressed.

  2. Second harmonic generation of q-Gaussian laser beam in preformed collisional plasma channel with nonlinear absorption

    SciTech Connect

    Gupta, Naveen Singh, Arvinder; Singh, Navpreet

    2015-11-15

    This paper presents a scheme for second harmonic generation of an intense q-Gaussian laser beam in a preformed parabolic plasma channel, where collisional nonlinearity is operative with nonlinear absorption. Due to nonuniform irradiance of intensity along the wavefront of the laser beam, nonuniform Ohmic heating of plasma electrons takes place. Due to this nonuniform heating of plasma, the laser beam gets self-focused and produces strong density gradients in the transverse direction. The generated density gradients excite an electron plasma wave at pump frequency that interacts with the pump beam to produce its second harmonics. The formulation is based on a numerical solution of the nonlinear Schrodinger wave equation in WKB approximation followed by moment theory approach. A second order nonlinear differential equation governing the propagation dynamics of the laser beam with distance of propagation has been obtained and is solved numerically by Runge Kutta fourth order technique. The effect of nonlinear absorption on self-focusing of the laser beam and conversion efficiency of its second harmonics has been investigated.

  3. An exact solution to paraxial propagation of laser beams in longitudinal inhomogeneous plasmas

    NASA Astrophysics Data System (ADS)

    Zhou, Bing-Ju; Huang, Zheng; Liu, Ming-Wei; Liu, Xiao-Juan

    2007-09-01

    An exact, general solution for laser beams propagating in longitudinally inhomogeneous plasmas is obtained in the form of the diffraction integral. The Gaussian beam and the Hermite-Gaussian beam are taken for example. In the case of an increasing plasma density along the propagation distance, natural diffraction of the Gaussian beam is retarded. This retardance has a less effect on the central part of the Hermite-Gaussian beam while a considerable rise of the power in bucket (PIB) occurs in the surrounding part of the beam.

  4. Directed Plasma Flow across Magnetic Field

    NASA Astrophysics Data System (ADS)

    Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.

    2008-04-01

    The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.

  5. Plasma effects of active ion beam injections in the ionosphere at rocket altitudes

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Cahill, L. J., Jr.; Kintner, P. M.; Moore, T. E.; Pollock, C. J.

    1992-01-01

    Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.

  6. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    SciTech Connect

    Jones, K. L.; Ahn, S.; Allmond, J. M.; Ayres, A.; Bardayan, D. W.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bey, A.; Bingham, C.; Cartegni, L.; Cerizza, G.; Chae, K. Y.; Cizewski, J. A.; Gade, A.; Galindo-Uribarri, A.; Garcia-Ruiz, R. F.; Grzywacz, R.; Howard, M. E.; Kozub, R. L.; Liang, J. F.; Manning, B.; Matoš, M.; McDaniel, S.; Miller, D.; Nesaraja, C. D.; O'Malley, P. D.; Padgett, S.; Padilla-Rodal, E.; Pain, S. D.; Pittman, S. T.; Radford, D. C.; Ratkiewicz, A.; Schmitt, K. T.; Shore, A.; Smith, M. S.; Stracener, D. W.; Stroberg, S. R.; Tostevin, J.; Varner, R. L.; Weisshaar, D.; Wimmer, K.; Winkler, R.

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.

  7. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    DOE PAGES

    Jones, K. L.; Ahn, S.; Allmond, J. M.; ...

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, Nmore » = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.« less

  8. Effect of plasma rotation on sawtooth stabilization by beam ions

    SciTech Connect

    N. N. Gorelenkov; M. F. F. Nave; R. Budny; C. Z. Cheng; G. Y. Fu; J. Hastie; J. Manickam; W. Park

    2000-06-23

    The sawtooth period in JET ELM-free H-Mode plasmas is increasing with Neutral Beam Injection (NBI) power. For injected power PNBI 12MW no large sawtooth crash is observed during the ELM-free period. However, as the edge stability is improved and external kink modes and ELMs are delayed, a possible sawtooth crash at a high plasma beta becomes a concern. In JET DT experiments, delaying sawteeth was found to be crucial in the quest for high fusion power. Fast particles are known to provide stabilizing effect on sawteeth, however, sawtooth stabilization by NBI ions is not clearly understood, since NBI ions are usually not ''fast'' enough to stabilize the m/n = 1/1 internal kink mode which is believed to cause the crash. In order to understand the observed sawteeth stabilization in tokamak experiments with NBI heating, the internal kink m/n = 1/1 mode stability of JET plasmas was modeled using the NOVA-K code, which is also benchmarked with the nonperturbative version of NOVA and the M3D code. Comparison of m/n = 1/1 mode stabilization by NBI ions in JET and TFTR and application of the nonlinear stabilization criteria is given.

  9. Assessment of the plasma start-up in Wendelstein 7-X with neutral beam injection

    NASA Astrophysics Data System (ADS)

    Gradic, D.; Dinklage, A.; Brakel, R.; McNeely, P.; Osakabe, M.; Rust, N.; Wolf, R.; the W7-X Team; the LHD Experimental Group

    2015-03-01

    Plasma start-up by neutral beam injection was investigated for stellarators. A zero-dimensional collisional model was extended to evaluate the temporal evolution of the plasma start-up in a confining toroidal magnetic field. Inclusion of different beam energy components indicated a substantial effect due to the energy dependence of beam-gas collisions. Additional collision processes and particle equations were considered to simulate the plasma start-up in helium-hydrogen mixtures. The isotope effect between operation with hydrogen and deuterium beams was also investigated. As a major objective the conditions necessary for a plasma start-up with neutral beams in W7-X have been examined. The assessed beam configuration in W7-X was found not to allow plasma start-up by neutral beam injection alone. The model has been validated for experimental data from W7-AS and Large Helical Device. Quantitative predictions of this study show that the ratio of the beam-plasma interaction length and the plasma volume is an essential quantity for the successful plasma start-up with neutral beams.

  10. Plasma focus neutron anisotropy measurements and influence of a deuteron beam obstacle

    NASA Astrophysics Data System (ADS)

    Talebitaher, A.; Springham, S. V.; Rawat, R. S.; Lee, P.

    2017-03-01

    The deuterium-deuterium (DD) fusion neutron yield and anisotropy were measured on a shot-to-shot basis for the NX2 plasma focus (PF) device using two beryllium fast-neutron activation detectors at 0° and 90° to the PF axis. Measurements were performed for deuterium gas pressures in the range 6-16 mbar, and positive correlations between neutron yield and anisotropy were observed at all pressures. Subsequently, at one deuterium gas pressure (13 mbar), the contribution to the fusion yield produced by the forwardly-directed D+ ion beam, emitted from the plasma pinch, was investigated by using a circular Pyrex plate to obstruct the beam and suppress its fusion contribution. Neutron measurements were performed with the obstacle positioned at two distances from the anode tip, and also without the obstacle. It was found that 80% of the neutron yield originates in the plasma pinch column and just above that. In addition, proton pinhole imaging was performed from the 0° and 90° directions to the pinch. The obtained proton images are consistent with the conclusion that DD fusion is concentrated ( 80%) in the pinch column region.

  11. SBS in Long-Scale-Length Plasmas for Direct-Drive ICF: Comparing Experiments with Simulations

    NASA Astrophysics Data System (ADS)

    Seka, W.; Myatt, J.; Maximov, A. V.; Short, R. W.; Craxton, R. S.; Regan, S. P.; Meyerhofer, D. D.; Stoeckl, C.; Yaakobi, B.

    2002-11-01

    Single- and multiple-beam SBS experiments will be compared to detailed simulations for plasmas representing direct-drive NIF conditions. The SBS spectra exhibit red- and blue-shifted features. The blue-shifted component is clearly identified with SBS in a flat velocity gradient that rapidly moves to higher expansion velocities. This feature can be reduced or suppressed by beam-smoothing techniques in both the experiments and simulations. The red-shifted spectrum originates near the critical density; it arises from EM seeding and is not reduced by beam smoothing. The agreement between experimental data and simulations now allows for more-confident extrapolation to other plasma conditions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  12. Simulation of radial expansion of an electron beam injected into a background plasma

    NASA Technical Reports Server (NTRS)

    Koga, J.; Lin, C. S.

    1989-01-01

    A 2-D electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

  13. Kinetic plasma modeling with quiet Monte Carlo direct simulation.

    SciTech Connect

    Albright, B. J.; Jones, M. E.; Lemons, D. S.; Winske, D.

    2001-01-01

    The modeling of collisions among particles in space plasma media poses a challenge for computer simulation. Traditional plasma methods are able to model well the extremes of highly collisional plasmas (MHD and Hall-MHD simulations) and collisionless plasmas (particle-in-cell simulations). However, neither is capable of trealing the intermediate, semi-collisional regime. The authors have invented a new approach to particle simulation called Quiet Monte Carlo Direct Simulation (QMCDS) that can, in principle, treat plasmas with arbitrary and arbitrarily varying collisionality. The QMCDS method will be described, and applications of the QMCDS method as 'proof of principle' to diffusion, hydrodynamics, and radiation transport will be presented. Of particular interest to the space plasma simulation community is the application of QMCDS to kinetic plasma modeling. A method for QMCDS simulation of kinetic plasmas will be outlined, and preliminary results of simulations in the limit of weak pitch-angle scattering will be presented.

  14. Nonlinear Charge and Current Neutralization of an Ion Beam Pulse in a Pre-formed Plasma

    SciTech Connect

    Igor D. Kaganovich; Gennady Shvets; Edward Startsev; Ronald C. Davidson

    2001-01-30

    The propagation of a high-current finite-length ion beam in a cold pre-formed plasma is investigated. The outcome of the calculation is the quantitative prediction of the degree of charge and current neutralization of the ion beam pulse by the background plasma. The electric magnetic fields generated by the ion beam are studied analytically for the nonlinear case where the plasma density is comparable in size with the beam density. Particle-in-cell simulations and fluid calculations of current and charge neutralization have been performed for parameters relevant to heavy ion fusion assuming long, dense beams with el >> V(subscript b)/omega(subscript b), where V(subscript b) is the beam velocity and omega subscript b is the electron plasma frequency evaluated with the ion beam density. An important conclusion is that for long, nonrelativistic ion beams, charge neutralization is, for all practical purposes, complete even for very tenuous background plasmas. As a result, the self-magnetic force dominates the electric force and the beam ions are always pinched during beam propagation in a background plasma.

  15. Return current effects in passive plasma lenses for relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Govil, Richa

    This thesis presents results of an experimental study of return currents effects on beam focusing in plasma lenses conducted at the Beam Test Facility (BTF) at Lawrence Berkeley National Laboratory (LBNL). Relativistic electron beams can be focused in field-free plasmas due to magnetic self-pinching. However, plasma return currents induced by the changing magnetic flux of a propagating bunch can reduce the total magnetic field and focusing force (Ampere's law). The experiment covered a parameter regime not observed previously, namely, the return current regime, where the collisionless plasma skindepth is small compared to the electron beam size and the focusing strength of the plasma lens is reduced due to return currents. A relativistic electron beam from the BTF, which utilizes the Advanced Light Source (ALS) injector, was used to study the properties of return currents in plasmas. The beam-transport line and experimental chamber were designed to allow measurement of electron beam size continuously along its path, before and after it passed through plasma lenses. For this purpose, an optical transition radiation (OTR) based diagnostic was developed. To ensure plasmas free of external fields, laser- ionization was chosen as the plasma production method. The dependence of plasma density on fill pressure and laser intensity was studied with an in-quadrature Mach- Zehnder radio frequency interferometer. A novel interferometry technique based on evanescent wave detection was developed to measure plasma densities above the cutoff density, for plasmas with a thickness less than the collisionless skin depth. Plasma density was controlled by changing the fill-pressure in the chamber, while the plasma profile was adjusted through the laser intensity. For typical experimental parameters, the electron beam size was observed to reduce in the presence of plasma. Plasma lenses were produced in the return current regime with the ratio of beam size to collisionless plasma

  16. Passive and active plasma deceleration for the compact disposal of electron beams

    SciTech Connect

    Bonatto, A.; Schroeder, C. B.; Vay, J.-L.; Geddes, C. G. R.; Benedetti, C.; Esarey, E.; Leemans, W. P.

    2015-08-15

    Plasma-based decelerating schemes are investigated as compact alternatives for the disposal of high-energy beams (beam dumps). Analytical solutions for the energy loss of electron beams propagating in passive and active (laser-driven) schemes are derived. These solutions, along with numerical modeling, are used to investigate the evolution of the electron distribution, including energy chirp and total beam energy. In the active beam dump scheme, a laser-driver allows a more homogeneous beam energy extraction and drastically reduces the energy chirp observed in the passive scheme. These concepts could benefit applications requiring overall compactness, such as transportable light sources, or facilities operating at high beam power.

  17. Attraction and repulsion of multi-color laser beams in plasmas: a computational study

    SciTech Connect

    Yi, S. A.; Kalmykov, S.; Shvets, G.

    2009-01-22

    The nonlinear interaction of high-power multi-color laser beams in plasmas is investigated numerically. Both the relativistic mass increase and the driven plasma wave contribute to the mutual beam-beam interaction and to the development of the electromagnetic cascade. The propagation of the individual cascade sidebands is modelled in the paraxial approximation. The resulting set of coupled nonlinear envelope equations is solved numerically using a newly developed pseudospectral method. We predict that two beams intersecting in the plasma can either attract or deflect each other depending on whether their frequency detuning is slightly below or above the electron Langmuir frequency.

  18. Defocusing of an ion beam propagating in background plasma due to two-stream instability

    SciTech Connect

    Tokluoglu, Erinc; Kaganovich, Igor D.

    2015-04-15

    The current and charge neutralization of charged particle beams by background plasma enable ballistic beam propagation and have a wide range of applications in inertial fusion and high energy density physics. However, the beam-plasma interaction can result in the development of collective instabilities that may have deleterious effects on ballistic propagation of an ion beam. In the case of fast, light-ion beams, non-linear fields created by instabilities can lead to significant defocusing of the beam. We study an ion beam pulse propagating in a background plasma, which is subjected to two-stream instability between the beam ions and plasma electrons, using PIC code LSP. The defocusing effects of the instability on the beam can be much more pronounced in small radius beams. We show through simulations that a beamlet produced from an ion beam passed through an aperture can be used as a diagnostic tool to identify the presence of the two-stream instability and quantify its defocusing effects. The effect can be observed on the Neutralized Drift Compression Experiment-II facility by measuring the spot size of the extracted beamlet propagating through several meters of plasma.

  19. Ion Beams in the Plasma Sheet Boundary Layer

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.; Runov, A.; Zhou, X.

    2015-12-01

    We explore characteristics of energetic particles in the plasma sheet boundary layer associated with dipolarization events, based on simulations and observations. The simulations use the electromagnetic fields of an MHD simulation of magnetotail reconnection and flow bursts as basis for test particle tracing. They are complemented by self-consistent fully electrodynamic particle-in-cell (PIC) simulations. The test particle simulations confirm that crescent shaped earthward flowing ion velocity distributions with strong perpendicular anisotropy can be generated as a consequence of near tail reconnection, associated with earthward flows and propagating magnetic field dipolarization fronts. Both PIC and test particle simulations show that the ion distribution in the outflow region close to the reconnection site also consist of a beam superposed on an undisturbed population; this beam, however, does not show strong perpendicular anisotropy. This suggests that the crescent shape is created by quasi-adiabatic deformation from ion motion along the magnetic field toward higher field strength. The simulation results compare favorably with ``Time History of Events and Macroscale Interactions during Substorms" (THEMIS) observations.

  20. Instability and dynamics of two nonlinearly coupled laser beams in a two-temperature electron plasma.

    PubMed

    Eliasson, B; Shukla, P K

    2006-10-01

    We consider nonlinear interactions between two colliding laser beams in an electron plasma, accounting for the relativistic electron mass increase in the laser fields and radiation pressure driven electron-acoustic (EA) perturbations that are supported by hot and cold electrons. By using the hydrodynamic and Maxwell equations, we obtain the relevant equations for nonlinearly coupled laser beams and EA perturbations. The coupled equations are then Fourier analyzed to obtain a nonlinear dispersion relation. The latter is numerically solved to show the existence of new classes of the parametric instabilities in the presence of two colliding laser beams in a two-electron plasma. The dynamics of nonlinearly coupled laser beams in our electron plasma is also investigated. The results should be useful in understanding the nonlinear propagation characteristics of multiple electromagnetic beams in laser-produced plasmas as well as in space plasmas.

  1. PRIMARY TESTS OF LASER / E BEAM INTERACTION IN A PLASMA CHANNEL.

    SciTech Connect

    POGORELSKY,I.V.; BEN ZVI,I.; HIROSE,T.; YAKIMENKO,V.; KUSCHE,K.; SIDDONS,P.; ET AL

    2002-06-23

    A high-energy CO{sub 2} laser is channeled in a capillary discharge. Plasma dynamic simulations confirm occurrence of guiding conditions at the relatively low axial plasma density 1 {divided_by} 4 x 10{sup 17} cm{sup -3}. A relativistic electron beam transmitted through the capillary changes its properties depending upon the plasma density. We observe focusing, defocusing or steering of the e-beam. Counter-propagation of the electron and laser beams in the plasma channel results in generation of intense picosecond x-ray pulses.

  2. Electron beam-plasma interaction experiments with the Versatile Toroidal Facility (VTF)

    SciTech Connect

    Murphy, S.M.; Lee, M.C.; Moriarty, D.T.; Riddolls, R.J.

    1995-12-31

    The laboratory investigation of electron beam-plasma interactions is motivated by the recent space shuttle experiments. Interesting but puzzling phenomena were observed in the shuttle experiments such as the bulk heating of background ionospheric plasmas by the injected electron beams and the excitation of plasma waves in the frequency range of ELF waves. The plasma machine, the Versatile Toroidal Facility (VTF) can generate a large magnetized plasma with the electron plasma frequency greater than the electron gyrofrequency by a factor of 3--5 similar to the plasma condition in the ionosphere. Short pulses of electron beams are injected into the VTF plasmas in order to simulate the beam injection from spacecrafts in the ionosphere. A Langmuir probe installed at a bottom port of VTF monitors the spatial variation of electron beams emitted from LaB6 filaments. An energy analyzer has been used to determine the particle energy distribution in the VTF plasmas. Several mechanisms will be tested as potential causes of the bulk heating of background plasmas by the injected electron beams as seen in the space shuttle experiments. It is speculated that the observed ELF emissions result from the excitation of purely growing modes detected by the space shuttle-borne detectors. Results of the laboratory experiments will be reported to corroborate this speculation.

  3. Further laboratory measurements of the beam-plasma discharge. [for aerospace technology application

    NASA Technical Reports Server (NTRS)

    Bernstein, W.; Leinbach, H.; Kellogg, P. J.; Monson, S. J.; Hallinan, T.

    1979-01-01

    The paper presents laboratory measurements of the beam-plasma discharge (BPD) produced when an energetic electron beam traverses an initially neutral gas. The results show that the critical beam current is related to energy, magnetic field, and the system length by an empirical relationship at pressures below 2 times 10 to the -5th power torr. This relationship describes the accumulation of ambient plasma density collisionally produced by the beam to a critical value at which ignition occurs. Additional measurements of the narrow-band cyclotron-related waves observed at beam currents below BPD threshold do not clearly establish whether this instability is a precursor to the BPD.

  4. Understanding extraction and beam transport in the ISIS H{sup -} Penning surface plasma ion source

    SciTech Connect

    Faircloth, D. C.; Letchford, A. P.; Gabor, C.; Whitehead, M. O.; Wood, T.; Jolly, S.; Pozimski, J.; Savage, P.; Woods, M.

    2008-02-15

    The ISIS H{sup -} Penning surface plasma source has been developed to produce beam currents up to 70 mA and pulse lengths up to 1.5 ms at 50 Hz. This paper details the investigation into beam extraction and beam transport in an attempt to understand the beam emittance and to try to improve the emittance. A scintillator profile measurement technique has been developed to assess the performance of different plasma electrode apertures, extraction electrode geometries, and postextraction acceleration configurations. This work shows that the present extraction, beam transport, and postacceleration system are suboptimal and further work is required to improve it.

  5. Plasma waves produced by the xenon ion beam experiment on the Porcupine sounding rocket

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.; Kelley, M.

    1982-01-01

    The production of electrostatic ion cyclotron waves by a perpendicular ion beam in the F-region ionosphere is described. The ion beam experiment was part of the Porcupine program and produced electrostatic hydrogen cyclotron waves just above harmonics of the hydrogen cyclotron frequency. The plasma process may be thought of as a magnetized background ionosphere through which an unmagnetized beam is flowing. The dispersion equation for this hypothesis is constructed and solved. Preliminary solutions agree well with the observed plasma waves.

  6. Temporal evolution of electron beam generated Argon plasma in pasotron device

    NASA Astrophysics Data System (ADS)

    Khandelwal, Neha; Pal, U. N.; Prakash, Ram; Choyal, Y.

    2016-10-01

    The plasma- assisted slow wave oscillator (PASOTRON) is a high power microwave source in which the electron beam in the interaction region is confined by the background plasma. The plasma is generated by impact ionization of background gas with the electron beam. A model has been developed for temporal evolution of Argon plasma in pasotron device. In this model, we consider electron beam of energy E interacting with Argon gas. The resulting ionization creates quasi neutral argon plasma composed of argon Ar atoms, singly ionized ions Ar+1and electrons having energy from 0 to E. Electron impact excitation, ionization, radiative decay, radiative recombination and three body recombination processes are considered in this model. Population of ground and excited states of argon atom, ground state of argon ion as well as the population of electron energy groups is calculated by solving time dependent rate equations. Temporal evolution of electron beam generated plasma is given.

  7. Generation of high-power electromagnetic radiation by a beam-driven plasma antenna

    NASA Astrophysics Data System (ADS)

    Annenkov, V. V.; Volchok, E. P.; Timofeev, I. V.

    2016-04-01

    In this paper we study how efficiently electromagnetic radiation can be generated by a relativistic electron beam with a gigawatt power level during its injection into a thin magnetized plasma. It is shown that, if the transverse beam and plasma size is compared with the radiation wavelength and the plasma density is modulated along the magnetic field, such a beam-plasma system can radiate electromagnetic waves via the antenna mechanism. We propose a theoretical model describing generation of electromagnetic waves by this plasma antenna and calculate its main radiation characteristics. In the two-dimensional case theoretical predictions on the radiation efficiency are shown to be confirmed by the results of particle-in-cell simulations, and the three-dimensional variant of this theory is used to estimate the peak power of sub-terahertz radiation that can be achieved in beam-plasma experiments in mirror traps.

  8. Stationary self-focusing of Gaussian laser beam in relativistic thermal quantum plasma

    SciTech Connect

    Patil, S. D.; Takale, M. V.

    2013-07-15

    In the present paper, we have employed the quantum dielectric response in thermal quantum plasma to model relativistic self-focusing of Gaussian laser beam in a plasma. We have presented an extensive parametric investigation of the dependence of beam-width parameter on distance of propagation in relativistic thermal quantum plasma. We have studied the role of Fermi temperature in the phenomenon of self-focusing. It is found that the quantum effects cause much higher oscillations of beam-width parameter and better relativistic focusing of laser beam in thermal quantum plasma in comparison with that in the relativistic cold quantum plasma and classical relativistic plasma. Our computations show more reliable results in comparison to the previous works.

  9. COUNTER PROPAGATION OF ELECTRON AND CO2 LASER BEAMS IN A PLASMA CHANNEL.

    SciTech Connect

    HIROSE,T.; POGORELSKY,I.V.; BEN ZVI,I.; YAKIMENKO,V.; KUSCHE,K.; SIDDONS,P.; KUMITA,T.; KAMIYA,Y.; ZIGLER,A.; GREENBERG,B.; ET AL

    2002-11-12

    A high-energy CO{sub 2} laser is channeled in a capillary discharge. Occurrence of guiding conditions at a relatively low plasma density (<10{sup 18} cm{sup -3}) is confirmed by MHD simulations. Divergence of relativistic electron beam changes depending on the plasma density. Counter-propagation of the electron and laser beams inside the plasma channel results in intense x-ray generation.

  10. Direct Simulation of Shock Layer Plasmas

    SciTech Connect

    Farbar, E. D.; Boyd, I. D.

    2011-05-20

    Approximate models of the electric field used with the DSMC method all impose quasi-neutrality everywhere in the shock layer plasma. The shortcomings of these models are examined in this study by simulating a weak shock layer plasma with a coupled DSMC-Particle-In-Cell (PIC) method. The stagnation streamline of an axisymmetric shock layer is simulated for entry velocities in air that correspond to both lunar and Mars return trajectories. The atmospheric densities, particle diameters and chemical reaction rates are varied from the actual values to make the computations tractable while retaining the mean free path of air at 85 km altitude. In contrast to DSMC flow field predictions, regions of non-neutrality are predicted by the DSMC-PIC method, and the electrons are predicted to be isothermal. Perhaps the most important result of this study is that the DSMC-PIC results at both reentry energies yield a 14% increase in heat flux to the vehicle surface relative to the DSMC results. Rather unintuitively, this is mostly due to an increase in ion flux to the surface, rather than the potential energy gained by each ion as it traverses the plasma sheath. In this study, an approximate electric field model is presented, with the goal of accounting for this heat flux augmentation without the need for a computationally expensive DSMC-PIC calculation of the entire flow-field. Convective heat flux results obtained with new electric field model are compared to results from the rigorous DSMC-PIC calculations.

  11. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    SciTech Connect

    Sydorenko, D.; Kaganovich, I. D.; Chen, L.; Ventzek, P. L. G.

    2015-12-15

    Generation of anomalously energetic suprathermal electrons was observed in simulation of a high-voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in the discharge via a two-stream instability. The energy transfer from the beam to the plasma electrons is ensured by the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The waves with short wavelength near the anode accelerate plasma bulk electrons to suprathermal energies. The sheath near the anode reflects some of the accelerated electrons back into the plasma. These electrons travel through the plasma, reflect near the cathode, and enter the accelerating area again but with a higher energy than before. Such particles are accelerated to energies much higher than after the first acceleration. This mechanism plays a role in explaining earlier experimental observations of energetic suprathermal electrons in similar discharges.

  12. Effect of radial plasma transport at the magnetic throat on axial ion beam formation

    NASA Astrophysics Data System (ADS)

    Zhang, Yunchao; Charles, Christine; Boswell, Rod

    2016-08-01

    Correlation between radial plasma transport and formation of an axial ion beam has been investigated in a helicon plasma reactor implemented with a convergent-divergent magnetic nozzle. The plasma discharge is sustained under a high magnetic field mode and a low magnetic field mode for which the electron energy probability function, the plasma density, the plasma potential, and the electron temperature are measured at the magnetic throat, and the two field modes show different radial parametric behaviors. Although an axial potential drop occurs in the plasma source for both field modes, an ion beam is only observed in the high field mode while not in the low field mode. The transport of energetic ions is characterized downstream of the plasma source using the delimited ion current and nonlocal ion current. A decay of ion beam strength is also observed in the diffusion chamber.

  13. Modeling and Simulation for Nanoparticle Plasma Jet Diagnostic Probe for Runaway Electron Beam-Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Bogatu, I. N.; Galkin, S. A.

    2016-10-01

    The C60 nanoparticle plasma jet (NPPJ) rapid injection into a tokamak major disruption is followed by C60 gradual fragmentation along plasma-traversing path. The result is abundant C ion concentration in the core plasma enhancing the potential to probe and diagnose the runaway electrons (REs) during different phases of their dynamics. A C60/C NPPJ of 75 mg, high-density (>1023 m-3) , hyper-velocity (>4 km/s), and uniquely fast response-to-delivery time ( 1 ms) has been demonstrated on a test bed. It can rapidly and deeply deliver enough mass to increase electron density to 2.4x1021 m-3, 60 times larger than typical DIII-D pre-disruption value. We will present the results of our on-going work on: 1) self-consistent model for RE current density evolution (by Dreicer mechanism and ``avalanche'') focused on the effect of fast and deep deposition of C ions, 2) improvement of single C60q+ fragmenting ion penetration model through tokamak B(R)-field and post-TQ plasma, and 3) simulation of C60q+ PJ penetration through the DIII-D characteristic 2 T B-field to the RE beam central location by using the Hybrid Electro-Magnetic 2D code (HEM-2D. Work supported by US DOE DE-SC0015776 Grant.

  14. Radial dependence of HF wave field strength in the BPD column. [Beam Plasma Discharge

    NASA Technical Reports Server (NTRS)

    Jost, R. J.; Anderson, H. R.; Bernstein, W.; Kellogg, P. J.

    1982-01-01

    The results of a recent set of RF frequency measurements of the beam plasma discharge (BPD) performed in order to determine a quantitative value for the field strength in the plasma frequency region of the spectrum are presented. The parallel and perpendicular components of the plasma wave electric fields inside the BPD column have comparable field strengths, on the order of 10 volts/m. The radial dependence of the field strength is very strong, decreasing by as much as 40 dB within one meter from the beam center, with the illumination or discharge column approximately one meter in diameter. The field strength inside the column increases as a function of distance along the beam at least for several meters from the gun aperture. The frequency and amplitude of the plasma wave increases with beam current. A particularly rapid increase in these parameters occurs as the beam current approaches the critical current.

  15. Issues with Phase Space Characterization of Laser-plasma Generated Electron Beams

    NASA Astrophysics Data System (ADS)

    Cianchi, A.; Alesini, D.; Anania, M. P.; Bellaveglia, M.; Castellano, M.; Chiadroni, E.; Di Giovenale, D.; Ferrario, M.; Mostacci, A.; Musumeci, P.; Pompili, R.; Ronsivalle, C.; Rossi, A. R.; Serafini, L.; Villa, F.

    Plasma acceleration is the new frontier in particle beam accelerators. Using the strong electric fields inside a plasma it is possible to achieve accelerating gradients orders of magnitude larger with respect to current technologies. Different schemes, using completely different approaches, have been proposed and several already tested, producing beams of energy up to several GeV. Regardless of the technique used for acceleration a precise determination of the output beam parameters is mandatory for the fine tuning of the process. The measurement of these parameters, in particular the beam distribution in transverse and longitudinal phase space, is not trivial, mainly due to the large energy spread and to the tight focusing of these beams or to the background noise produced in the plasma channel. We illustrate the main problems related to the diagnostic of this kind of beams and some of the proposed or already realized solutions

  16. Interaction of high power laser beams with plasma in ICF hohlraum using the FDTD method

    NASA Astrophysics Data System (ADS)

    Lin, Zhili

    2016-11-01

    In the indirect-drive Inertial confinement fusion (ICF) system, groups of laser beams are injected into a gold cylindrical hohlraum and plasma is stimulated with the ablation of the wall of hohlraum by the laser beams. In our work, the finite-difference time-domain (FDTD) method associated with the bilinear transform and Maclaurin series expansion approaches is utilized to examine the laser beam propagation in plasma described by the Drude model. The state-of-the-art approaches for generating the laser beams are presented and realized according to the full utilization of the TF/SF source condition. Base on the previous technologies, the quantitatively numerical analysis of the propagation characteristics of laser beams in the plasma is conducted. The obtained results are illustrated and discussed that are helpful for the parameter optimization of laser beams for an ICF system.

  17. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor; Sydorenko, Dmytro; Ventzek, Peter L. G.

    2016-09-01

    Electrons emitted from electrodes are accelerated by the sheath electric field and become the electron beams penetrating the plasma. The electron beam can interact with the plasma in collisionless manner via two-stream instability and produce suprathermal electrons. In order to understand the mechanism of suprathermal electrons acceleration, a beam-plasma system was simulated using a 1D3V particle-in-cell code EDIPIC. These simulation results show that the acceleration may be caused by the effects related to the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The short waves near the anode accelerate plasma bulk electrons to suprathermal energies. Rich complexity of beam-plasma interaction phenomena was also observed: intermittency and multiple regimes of two-stream instability in a dc discharge, band structure of the growth rate of the two-stream instability of an electron beam propagating in a bounded plasma, multi-stage acceleration of electrons in a finite system. This research was funded by US Department of Energy.

  18. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    NASA Astrophysics Data System (ADS)

    Sydorenko, Dmytro; Kaganovich, Igor D.; Ventzek, Peter L. G.

    2016-10-01

    Electrons emitted from electrodes are accelerated by the sheath electric field and become the electron beams penetrating the plasma. The electron beam can interact with the plasma in collisionless manner via two-stream instability and produce suprathermal electrons. In order to understand the mechanism of suprathermal electrons acceleration, a beam-plasma system was simulated using a 1D3V particle-in-cell code EDIPIC. These simulation results show that the acceleration may be caused by the effects related to the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The short waves near the anode accelerate plasma bulk electrons to suprathermal energies. Rich complexity of beam- plasma interaction phenomena was also observed: intermittency and multiple regimes of two-stream instability in a dc discharge, band structure of the growth rate of the two-stream instability of an electron beam propagating in a bounded plasma, multi-stage acceleration of electrons in a finite system.

  19. Neutrino Mass Measurement Using a Directed Mono-Energetic Beam

    NASA Astrophysics Data System (ADS)

    Tsifrinovich, Vladimir; Folan, Lorcan

    2015-04-01

    It was shown that a directed mono-energetic neutrino beam can be generated by electron capture beta-decay in a sample with a strong hyperfine field at the radioactive nuclei. We study the conditions required to measure the neutrino rest mass using the recoil force produced by a directed neutrino beam. We consider the displacement of an atomic force microscope cantilever due to such a recoil force. We find the change in the cantilever displacement associated with the non-zero neutrino mass, as a function of nuclear half-life T1 / 2, cantilever spring constant, and temperature. We consider the opportunity to increase the sensitivity of the neutrino mass measurement using averaging of the measurement signal. We show that the optimal time for the signal accumulation is, approximately, 1.8T1 / 2. We compute the optimal signal-to-noise ratio for 119Sb nuclei decaying to 119Sn with a decrease in the nuclear spin from I = 5/2 to I = 3/2, and T1 / 2 = 38.2 hours. Finally, we present the parameters values required for detection of sub-eV neutrino rest mass, and estimate the angular distribution of neutrino radiation as a function of temperature.

  20. Ion Beam and Plasma Technology Development for Surface Modification at Los Alamos National Laboratory

    SciTech Connect

    Davis, H.A.; Munson, C.P.; Wood, B.P.; Bitteker, L.J.; Nastasi, M.A.; Rej, D.J.; Waganaar, W.J.; Walter, K.C.; Coates, D.M.; Schleinitz, H.M.

    1997-12-31

    We are developing two high-throughput technologies for materials modification. The first is a repetitive intense ion beam source for materials modification through rapid surface melt and resolidification (up to 10{sup 10} deg/sec cooling rates) and for ablative deposition of coatings. The short range of the ions (typically 0.1 to 5 micrometers) allows vaporization or melting at moderate beam energy density (typically 1-50 J/cm{sup 2}). A new repetitive intense ion beam accelerator called CHAMP is under development at Los Alamos. The design beam parameters are: E=200 keV, I=15 kA, {tau}=1 {micro}s, and 1 Hz. This accelerator will enable applications such as film deposition, alloying and mixing, cleaning and polishing, corrosion and wear resistance, polymer surface treatments, and nanophase powder synthesis. The second technology is plasma source ion implantation (PSII) using plasmas generated from both gas phase (using radio frequency excitation) and solid phase (using a cathodic arc) sources. We have used PSII to directly implant ions for surface modification or as method for generating graded interfaces to enhance the adhesion of surface coatings. Surfaces with areas of up to 16 m{sup 2} and weighing more than a thousand kilograms have been treated in the Los Alamos PSII chamber. In addition, PSII in combination with cathodic source deposition has been used to form highly adherent, thick Er{sub 2}O{sub 3} coatings on steel for reactive metal containment in casting. These coatings resist delamination under extreme mechanical and thermal stress.

  1. Low Temperature Plasmas Generated and Sustained Indefinitely Using a Focused Microwave Beam

    NASA Astrophysics Data System (ADS)

    Reid, Remington; Hoff, Brad; Lepell, Paul; AFRL Team

    2016-10-01

    The Air Force Research Laboratory has constructed a device that can initiate a plasma discharge in a focused microwave beam and sustain it indefinitely. A 10 kW, 4.5 GHz beam is passed through a vacuum chamber outfitted with pressure windows that are transparent to 4.5 GHz radiation. The pressure windows are large enough in diameter to prevent any interactions between the beam and the metallic chamber. The entire experiment is housed inside an anechoic chamber to minimize reflections. This novel plasma source generates low temperature, low density plasmas that have no contact with the walls which minimizes contamination and sheath formation.

  2. Effects of ionization distribution on plasma beam focusing characteristics in Hall thrusters

    NASA Astrophysics Data System (ADS)

    Ning, Zhongxi; Liu, Hui; Yu, Daren; Zhou, Zhongxiang

    2011-11-01

    The relationship between ionization distribution and divergence of plasma beam in a Hall thruster is investigated using spectrum and probe methods. Experimental results indicate that the shift of ionization region towards the exit of channel causes the reduction of accelerating field and the enhancement of electron thermal pressure effect, which result in further deviation of equipotential lines to magnetic field lines and further increase in divergence of plasma beam. It is, therefore, suggested that to put the ionization region deep inside the channel and separate it from the acceleration region at the design, and development stage is helpful to improve the plasma beam focusing characteristics of a Hall thruster.

  3. Effects of ionization distribution on plasma beam focusing characteristics in Hall thrusters

    SciTech Connect

    Ning Zhongxi; Liu Hui; Yu Daren; Zhou Zhongxiang

    2011-11-28

    The relationship between ionization distribution and divergence of plasma beam in a Hall thruster is investigated using spectrum and probe methods. Experimental results indicate that the shift of ionization region towards the exit of channel causes the reduction of accelerating field and the enhancement of electron thermal pressure effect, which result in further deviation of equipotential lines to magnetic field lines and further increase in divergence of plasma beam. It is, therefore, suggested that to put the ionization region deep inside the channel and separate it from the acceleration region at the design, and development stage is helpful to improve the plasma beam focusing characteristics of a Hall thruster.

  4. Energy deposition of heavy ions in the regime of strong beam-plasma correlations.

    PubMed

    Gericke, D O; Schlanges, M

    2003-03-01

    The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.

  5. Modification of the Coherence Properties of a Laser Beam Propagating through a Plasma and its Consequences for Stimulated Scattering Instabilities

    SciTech Connect

    Labaune, C; Baldis, H A; Bandulet, H; Depierreux, S; Fuchs, J; Michel, P; Pesme, D

    2002-11-19

    The control of coherence is a critical issue for the high-power lasers used in inertial confinement fusion (ICF). The level of coherence is an important parameter for the control of the light intensity distribution as well as the growth rate of parametric instabilities. Over the past few years, experimental and theoretical studies have evidenced the ability of an underdense plasma to reduce the spatial and temporal coherence of an intense laser beam propagating through it. As any process affecting laser propagation, plasma-induced incoherence appears fundamental for ICF for it can impact on wave-coupling conditions. We present results obtained with the six-beam LULI laser facility, in the nanosecond regime, showing direct evidences of the reduction of spatial and temporal coherence of an initially RPP-smoothed laser beam after propagation through a preformed plasma. Plasma induced incoherence (PII) proceeds from several mechanisms which include self-focusing and filament instabilities and non-linear coupling between self-focusing and forward stimulated Brillouin scattering (FSBS). Part of these experiments was dedicated to the understanding of the physical mechanisms involved in PII, as the break up of a single hot spot and the existence of ion acoustic waves having small wave vectors transverse to the interaction beam which are produced in the PII processes. The spatial and temporal characteristics of these waves give a unique access to the influence of PII on stimulated Brillouin and Raman scattering.

  6. Application of Laser-Generated Ion Beams for Isochoric Heating to Study Plasma Mix at Interfaces

    NASA Astrophysics Data System (ADS)

    Albright, B. J.; Fernández, J. C.; Bang, W.; Bradley, P. A.; Gautier, D. C.; Hamilton, C. E.; Palaniyappan, S.; Santiago Cordoba, M. A.; Vold, E. L.; Yin, L.; Hegelich, B. M.; Dyer, G.; Roycroft, R.

    2015-11-01

    The evolution and mixing of high-Z/low-Z interfaces in plasma media is of profound importance to high energy density physics and inertial fusion experiments. Recent experiments performed at the LANL Trident laser facility as part of the Plasma Interfacial Mix project have applied novel, laser-generated ion beams created under conditions of relativistic induced transparency to the heating of solid-density, multi-material targets isochorically and uniformly (over a few tens of ps), attaining plasma temperatures of several eV. Measurements have been made of the evolving plasma, including location of the material interface and the time-history of the temperature of the medium. Recent data and associated radiation hydrodynamic modeling from our Trident campaigns will be reported. Complementary kinetic simulations of interface evolution, showing anomalously rapid atomic mixing under conditions relevant to ICF experiments, will also be discussed. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Los Alamos National Laboratory Directed Research and Development Program.

  7. Anomalous electron diffusion across a magnetic field in a beam-plasma system

    SciTech Connect

    Okuda, H.; Ono, M.; Armstrong, R.J.

    1987-10-01

    The diffusion of electrons across a magnetic field in the presence of a beam-plasma instability has been studied by means of two-dimensional numerical simulations. It is found that the beam electrons can diffuse much faster across the magnetic field than the thermal electrons. This can be explained by the fact that the electrons in the beam are in resonance with the waves excited by the beam-plasma instability so that they experience a nearly dc electric field, causing large cE x B/B/sup 2/ excursions. 8 refs., 5 figs.

  8. Transport and Non-Invasive Position Detection of Electron Beams from Laser-Plasma Accelerators

    SciTech Connect

    Osterhoff, Jens; Sokollik, Thomas; Nakamura, Kei; Bakeman, Michael; Weingartner, R; Gonsalves, Anthony; Shiraishi, Satomi; Lin, Chen; vanTilborg, Jeroen; Geddes, Cameron; Schroeder, Carl; Esarey, Eric; Toth, Csaba; DeSantis, Stefano; Byrd, John; Gruner, F; Leemans, Wim

    2011-07-20

    The controlled imaging and transport of ultra-relativistic electrons from laser-plasma accelerators is of crucial importance to further use of these beams, e.g. in high peak-brightness light sources. We present our plans to realize beam transport with miniature permanent quadrupole magnets from the electron source through our THUNDER undulator. Simulation results demonstrate the importance of beam imaging by investigating the generated XUV-photon flux. In addition, first experimental findings of utilizing cavity-based monitors for non-invasive beam-position measurements in a noisy electromagnetic laser-plasma environment are discussed.

  9. Naphthalene and acenaphthene decomposition by electron beam generated plasma application

    SciTech Connect

    Ostapczuk, A.; Hakoda, T.; Shimada, A.; Kojima, T.

    2008-08-15

    The application of non-thermal plasma generated by electron beam (EB) was investigated in laboratory scale to study decomposition of polycyclic aromatic hydrocarbons like naphthalene and acenaphthene in flue gas. PAH compounds were treated by EB with the dose up to 8 kGy in dry and humid base gas mixtures. Experimentally established G-values gained 1.66 and 3.72 mol/100 eV for NL and AC at the dose of 1 kGy. NL and AC removal was observed in dry base gas mixtures showing that the reaction with OH radical is not exclusive pathway to initialize PAH decomposition; however in the presence of water remarkably higher decomposition efficiency was observed. As by-products of NL decomposition were identified compounds containing one aromatic ring and oxygen atoms besides CO and CO{sub 2}. It led to the conclusion that PAH decomposition process in humid flue gas can be regarded as multi-step oxidative de-aromatization analogical to its atmospheric chemistry.

  10. Underwater cladding with laser beam and plasma arc welding

    SciTech Connect

    White, R.A.; Fusaro, R.; Jones, M.G.; Solomon, H.D.; Milian-Rodriguez, R.R.

    1997-01-01

    Two welding processes, plasma arc (transferred arc) (PTA) and laser beam, were investigated to apply cladding to austenitic stainless steels and Inconel 600. These processes have long been used to apply cladding layers , but the novel feature being reported here is that these cladding layers were applied underwater, with a water pressure equivalent to 24 m (80 ft). Being able to apply the cladding underwater is very important for many applications, including the construction of off-shore oil platforms and the repair of nuclear reactors. In the latter case, being able to weld underwater eliminates the need for draining the reactor and removing the fuel. Welding underwater in reactors presents numerous challenges, but the ability to weld without having to drain the reactor and remove the fuel provides a huge cost savings. Welding underwater in reactors must be done remotely, but because of the radioactive corrosion products and neutron activation of the steels, remote welding would also be required even if the reactor is drained and the fuel removed. In fact, without the shielding of the water, the remote welding required if the reactor is drained might be even more difficult than that required with underwater welds. Furthermore, as shall be shown, the underwater welds that the authors have made were of high quality and exhibit compressive rather than tensile residual stresses.

  11. Neutralization efficiency estimation in a neutral beam source based on inductively coupled plasma

    SciTech Connect

    Vozniy, O. V.; Yeom, G. Y.

    2009-01-01

    This study examined the optimal conditions of neutral beam generation to maintain a high degree of neutralization and focusing during beam energy variation for a neutral beam source based on inductively coupled plasma with a three-grid ion beam acceleration system. The neutral beam energy distribution was estimated by measuring the energy profiles of ions that 'survived' the neutralization after reflection. The energy measurements of the primary and reflected ions showed narrow distribution functions, each with only one peak. At higher beam energies, both the ratio of the ion energy loss to the primary energy and the degree of energy divergence decreased, confirming the precise alignment of the neutral beam. The neutralization efficiency of the neutral beam source with a three-grid acceleration system was found to be affected mainly by the beam angle divergence rather than by the particle translation energy.

  12. Turbulent and directed plasma motions in solar flares

    NASA Technical Reports Server (NTRS)

    Fludra, A.; Bentley, R. D.; Lemen, J. R.; Jakimiec, J.; Sylwester, J.

    1989-01-01

    An improved method for fitting asymmetric soft X-ray line profiles from solar flares is presented. A two-component model is used where one component represents the total emission from directed upflow plasma and the other the emission from the plasma at rest. Unlike previous methods, the width of the moving component is independent from that of the stationary component. Time variations of flare plasma characteristics (i.e., temperature, emission measure of moving and stationary plasma, upflow and turbulent velocities) are derived from the Ca XIX and Fe XXV spectra recorded by the Bent Crystal Spectrometer on the Solar Maximum Mission. The fitting technique provides a statistical estimation for the uncertainties in the fitting parameters. The relationship between the directed and turbulent motions has been studied, and a correlation of the random and directed motions has been found in some flares with intensive plasma upflows. Mean temperatures of the upflowing and stationary plasmas are compared for the first time from ratios of calcium to iron X-ray line intensities. Finally, evidence for turbulent motions and the possibility of plasma upflow late into the decay phase is presented and discussed.

  13. AN IMPLICIT"DRIFT-LORENTZ" PARTICLE MOVER FOR PLASMA AND BEAM SIMULATIONS

    SciTech Connect

    Friedman, A.; Grote, D.P.; Vay, J.-L; Cohen, R.H.

    2008-07-15

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventionalparticle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  14. An Implicit "Drift-Lorentz" Mover for Plasma and Beam Simulations

    SciTech Connect

    Cohen, R H; Friedman, A; Grote, D P; Vay, J

    2009-02-12

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventional particle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  15. Ablation of graphene film by direct Nd:YVO4 laser under various beaming conditions.

    PubMed

    Lee, Jeongmin; Han, Jae-Hee; Lee, Jung-Hun; Yoo, Ji-Beom; Cho, Seongjae; Kwon, Sang Jik; Cho, Eou Sik

    2014-12-01

    Recently, graphene is gaining increasing popularity as one of the most functional materials for advanced electronic and optical devices owing to its high carrier mobility and optical transparency. Patterning the graphene calls for particular cares in line definition without carbon (C)-based residues that might be working as a leakage path. Thus, realization and processing of the graphene monolayer are very complicated and need to be stringently controlled. For this reason, in accordance, processing technology should be evolved with higher reliability and accuracy, and compatibility with the conventional unit processes including electron beam (e-beam) lithography, plasma etching, and nano-dimensional optical lithography. In this work, a reliable, simple, and cost-effective technique for patterning the graphene is proposed. Graphene film transferred on glass substrate is directly patterned by a quality factor (Q)-switched neodymium-doped yttrium vanadate (Nd:YVO4, λ = 1064 nm) pumped laser diode (LD). In order to optimize the process condition, various beaming conditions of repetition rate and scanning speed are experimented. From the optical microscope images, it has been shown that graphene film was more easily etched by direct laser patterning technique at higher repetition and faster scanning speed. It was confirmed by Raman spectrum where 2-dimensional (2-D) and graphite (G) peaks were closely investigated that graphene residue was also completely removed after the proposed processing technique.

  16. Numerical simulation of inducing characteristics of high energy electron beam plasma for aerodynamics applications

    NASA Astrophysics Data System (ADS)

    Yongfeng, DENG; Jian, JIANG; Xianwei, HAN; Chang, TAN; Jianguo, WEI

    2017-04-01

    The problem of flow active control by low temperature plasma is considered to be one of the most flourishing fields of aerodynamics due to its practical advantages. Compared with other means, the electron beam plasma is a potential flow control method for large scale flow. In this paper, a computational fluid dynamics model coupled with a multi-fluid plasma model is established to investigate the aerodynamic characteristics induced by electron beam plasma. The results demonstrate that the electron beam strongly influences the flow properties, not only in the boundary layers, but also in the main flow. A weak shockwave is induced at the electron beam injection position and develops to the other side of the wind tunnel behind the beam. It brings additional energy into air, and the inducing characteristics are closely related to the beam power and increase nonlinearly with it. The injection angles also influence the flow properties to some extent. Based on this research, we demonstrate that the high energy electron beam air plasma has three attractive advantages in aerodynamic applications, i.e. the high energy density, wide action range and excellent action effect. Due to the rapid development of near space hypersonic vehicles and atmospheric fighters, by optimizing the parameters, the electron beam can be used as an alternative means in aerodynamic steering in these applications.

  17. Physics of Neutralization of Intense Charged Particle Beam Pulses by a Background Plasma

    SciTech Connect

    Kaganovich, I.D.; Davidson, R.C.; Dorf, M.A.; Startsev, E.A.; Sefkow, A.B; Friedman, A.F.; Lee, E.P.

    2009-09-03

    Neutralization and focusing of intense charged particle beam pulses by a background plasma forms the basis for a wide range of applications to high energy accelerators and colliders, heavy ion fusion, and astrophysics. For example, for ballistic propagation of intense ion beam pulses, background plasma can be used to effectively neutralize the beam charge and current, so that the self-electric and self-magnetic fields do not affect the ballistic propagation of the beam. From the practical perspective of designing advanced plasma sources for beam neutralization, a robust theory should be able to predict the self-electric and self-magnetic fields during beam propagation through the background plasma. The major scaling relations for the self-electric and self-magnetic fields of intense ion charge bunches propagating through background plasma have been determined taking into account the effects of transients during beam entry into the plasma, the excitation of collective plasma waves, the effects of gas ionization, finite electron temperature, and applied solenoidal and dipole magnetic fields. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of current density and self-magnetic field perturbations is generated behind the beam pulse. A solenoidal magnetic field can be applied for controlling the beam propagation. Making use of theoretical models and advanced numerical simulations, it is shown that even a small applied magnetic field of about 100G can strongly affect the beam neutralization. It has also been demonstrated that in the presence of an applied magnetic field the ion beam pulse can excite large-amplitude whistler waves, thereby producing a complex structure of self-electric and self-magnetic fields. The presence of an applied solenoidal magnetic field may also cause a strong enhancement of the radial self-electric field of the beam pulse propagating

  18. A second kind of Beam-Plasma Discharge (BPD): Rocket and laboratory results

    NASA Technical Reports Server (NTRS)

    Kellogg, P. J.; Monson, S. J.

    1983-01-01

    It is shown that there are two types of beam plasma discharge observed in rocket shots. The second BPD transition (BPD2) is characterized by a very broad featureless emission extending from much less than the cyclotron frequency to several times the plasma frequency. The characteristic spectra observed close to the beam plasma discharge region are deformed by the intervening plasma when observations are made at a distance from the injection field line and lead to spectra which must be interpreted with care. In one case, the Bernstein mode at 2 fce seems to be a remnant of the broad, featureless spectrum of BPD2.

  19. Study of the thermal effect on silicon surface induced by ion beam from plasma focus device

    NASA Astrophysics Data System (ADS)

    Ahmad, Z.; Ahmad, M.; Al-Hawat, Sh.; Akel, M.

    2017-04-01

    Structural modifications in form of ripples and cracks are induced by nitrogen ions from plasma focus on silicon surface. The investigation of such structures reveals correlation between ripples and cracks formation in peripheral region of the melt spot. The reason of such correlation and structure formation is explained as result of thermal effect. Melting and resolidification of the center of irradiated area occur within one micro second of time. This is supported by a numerical simulation used to investigate the thermal effect induced by the plasma focus ion beams on the silicon surface. This simulation provides information about the temperature profile as well as the dynamic of the thermal propagation in depth and lateral directions. In accordance with the experimental observations, that ripples are formed in latter stage after the arrival of last ion, the simulation shows that the thermal relaxation takes place in few microseconds after the end of the ion beam arrival. Additionally, the dependency of thermal propagation and relaxation on the distance of the silicon surface from the anode is presented.

  20. Initial Tests of a Plasma Beam Combiner at NIF

    NASA Astrophysics Data System (ADS)

    Kirkwood, R. K.; Turnbull, D. P.; Chapman, T. D.; Wilks, S. C.; London, R. A.; Berger, R. L.; Michel, P. A.; Divol, L.; Dunlop, W. H.; MacGowan, B. J.; Fournier, K. B.; Blue, B. E.; NIF Team

    2016-10-01

    The seeded forward SBS process that is known to effectively amplify beams in ignition targets has recently been used to design and test a target to combine the power and energy of many beams of the NIF facility into a single beam by intersecting them in an ionized gas. The demand for high-power beams for a variety of applications at NIF makes a demonstration of this process attractive. We will describe experiments using a gas-filled balloon heated by 10 quads of beams, and pumped by additional frequency-tuned quads to amplify a single beam. The beam energy is indicated by gated x-ray images of both the spots produced by the transmitted pump and probe beams and the spot produced by a non-interacting quad of beams when they terminate on a foil. The first experiment produced a high brightness seed beam with significant reductions in brightness of the pumping beams, consistent with their depletion by energy transfer to the seed. Additional experiments studying spot brightness with varying pump power to determine total delivered seed beam energy and power will be discussed as available. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  1. Feasibility study of fusion plasma heating by relativistic high-current electron beams

    NASA Astrophysics Data System (ADS)

    Yakimenko, V.

    2017-03-01

    The goal of this research will be to study the feasibility of fusion plasma heating using ultra-short high intensity electron beam by dissipating the energy of excited wakes either in linear or nonlinear regimes.

  2. Long-lived laboratory plasmas sustained by a free-space microwave beam

    NASA Astrophysics Data System (ADS)

    Reid, Remington

    2015-11-01

    The Air Force Research Laboratory is developing a laboratory experiment to study the free-space interaction of microwave beams with low temperature, low density plasmas. A 10 kW, 4.5 GHz beam is passed through a vacuum chamber outfitted with pressure windows that are transparent to 4.5 Ghz radiation. The pressure windows are approximately 1m in diameter, allowing for minimal interaction between the beam and the chamber. The entire experiment is housed inside an anechoic chamber to minimize reflections. Plasmas generated by the beam have been observed to be stable for more than 10s. A series of optical and microwave diagnostics are being developed to measure the plasma properties, and to quantify the interaction of the plasma and the background neutral gas.

  3. Numerical simulation of nonlinear processes in a beam-plasma system

    SciTech Connect

    Efimova, A. A. Berendeev, E. A.; Vshivkov, V. A.; Dudnikova, G. I.

    2015-10-28

    In the present paper we consider the efficiency of the electromagnetic radiation generation due to various nonlinear processes in the beam-plasma system. The beam and plasma parameters were chosen close to the parameters in the experiment on the GOL-3 facility (BINP SB RAS). The model of the collisionless plasma is described by system of the Vlasov-Maxwell equations with periodic boundary conditions. The parallel numerical algorithm is based on the particles-in-cell method (PIC) with mixed Euler-Lagrangian domain decomposition. Various scenarios of nonlinear evolution in the beam-plasma system under the influence of an external magnetic field in case of a low density beam were studied. The energy transfer from one unstable mode to the others modes was observed.

  4. Flute instability of an ion-focused slab electron beam in a broad plasma

    SciTech Connect

    Whittum, D.H. , 1-1 Oho, Tsukuba, Ibaraki 305 ); Lampe, M.; Joyce, G.; Slinker, S.P. ); Yu, S.S.; Sharp, W.M. )

    1992-11-15

    An intense relativistic electron beam with an elongated cross section, propagating in the ion-focused regime through a broad, uniform, unmagnetized plasma, is shown to suffer a transverse flute instability. This instability arises from the electrostatic coupling between the beam and the plasma electrons at the ion-channel edge. The instability is found to be absolute and the asymptotic growth of the flute amplitude is computed in the frozen-field'' approximation and the large skin-depth limit. The minimum growth length is shown to be much less than the betatron period, with the consequence that focusing is rendered ineffective. It is further shown that growth is much reduced when the beam propagates through a narrow channel where the ion density greatly exceeds that of the surrounding plasma. In this limit, a modest spread in betatron frequency produces rapid saturation. The effect of plasma electron collisions is also considered. Results of beam breakup simulations are noted.

  5. Efficient regime of electromagnetic emission in a plasma with counterstreaming electron beams

    SciTech Connect

    Timofeev, I. V.; Annenkov, V. V.

    2014-08-15

    Efficiency of electromagnetic emission produced in a magnetized plasma with counterstreaming electron beams was investigated using both the linear kinetic theory and particle-in-cell simulations. We calculated the growth rate of the beam-plasma instability taking into account both kinetic and relativistic effects and showed that there exists a regime in which transversely propagating electromagnetic waves can be generated by the coupling of the most unstable oblique beam-driven modes. It was confirmed by numerical simulations that such a tune-up of system parameters for a specific nonlinear process can lead to a substantial increase in electromagnetic emission efficiency. It was found that electromagnetic radiation emerging from the plasma in such a regime is generated near the harmonics of the pump frequency that is determined by the typical eigenfrequency of the beam-driven modes. It was also shown that the peak emission power can reach 5% of the maximal power lost by beam electrons.

  6. Ponderomotive self-focusing of Gaussian laser beam in warm collisional plasma

    SciTech Connect

    Jafari Milani, M. R.; Niknam, A. R.; Farahbod, A. H.

    2014-06-15

    The propagation characteristics of a Gaussian laser beam through warm collisional plasma are investigated by considering the ponderomotive force nonlinearity and the complex eikonal function. By introducing the dielectric permittivity of warm unmagnetized plasma and using the WKB and paraxial ray approximations, the coupled differential equations defining the variations of laser beam parameters are obtained and solved numerically. Effects of laser and plasma parameters such as the collision frequency, the initial laser intensity and its spot size on the beam width parameter and the axis laser intensity distribution are analyzed. It is shown that, self-focusing of the laser beam takes place faster by increasing the collision frequency and initial laser spot size and then after some distance propagation the laser beam abruptly loses its initial diameter and vastly diverges. Furthermore, the modified electron density distribution is obtained and the collision frequency effect on this distribution is studied.

  7. Theory of type 3b solar radio bursts. [plasma interaction and electron beams

    NASA Technical Reports Server (NTRS)

    Smith, R. A.; Delanoee, J.

    1975-01-01

    During the initial space-time evolution of an electron beam injected into the corona, the strong beam-plasma interaction occurs at the head of the beam, leading to the amplification of a quasi-monochromatic large-amplitude plasma wave that stabilizes by trapping the beam particles. Oscillation of the trapped particles in the wave troughs amplifies sideband electrostatic waves. The sidebands and the main wave subsequently decay to observable transverse electromagnetic waves through the parametric decay instability. This process gives rise to the elementary striation bursts. Owing to velocity dispersion in the beam and the density gradient of the corona, the entire process may repeat at a finite number of discrete plasma levels, producing chains of elementary bursts. All the properties of the type IIIb bursts are accounted for in the context of the theory.

  8. Effect of Laser Beam Filamentation on Second Harmonic Spectrum in Laser Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Sharma, Prerana; Sharma, R. P.

    2009-11-01

    This paper presents the laser beam filamentation at ultra relativistic laser powers, when the restriction on the beam is relaxed during filamentation process. On account of laser beam intensity gradient and background density gradients in filamentary regions the electron plasma wave (epw) at pump wave frequency is generated, this epw is found to be highly localized on account of the laser beam filaments. Interaction of incident laser beam with these epw leads to second harmonic generation. The second harmonic spectrum has also been studied in detail and its correlation with the filamentation of the laser beam has been established. Starting almost with a monochromatic component of laser beam propagation, the second harmonic spectrum becomes more complicated and broadened as the laser beam propagates further, and filamentation takes place. For the typical laser beam and plasma parameters: λ0= 1064 nm, power flux (10^22 W/cm^2),φp=0.03φ0, vth=0.1c, n0=1.9x10^19. We found that conversion efficiency comes out to be (E2/E0) = 8x10-3, and the spectrum is quite broad which depends upon the laser beam propagation distance. The results (specifically, second harmonic spectral feature) presented here may be used for the diagnostics of laser produced plasmas.

  9. Innovative measurement of Debye shielding in plasmas by Lyman-α radiation of a probing metastable hydrogen beam

    SciTech Connect

    Lejeune, A.; Chérigier-Kovacic, L. Doveil, F.

    2014-02-11

    Answering to a long-standing challenge, a new way to non-intrusively measure weak electric fields in plasmas is presented. Here we show it using an H(2s) atomic probe beam, obtained from the conversion of H{sup +} ions into H(2s) either by collisions with H{sub 2} residual gas or in a resonant charge exchange cesium cell. The probe beam is sent between two polarized plates creating an electric field applied within a thermionic plasma. Indeed the interaction between a metastable H(2s) atomic hydrogen beam and an external electric field leads to the emission of the Lyman-alpha line owing to the Stark mixing of the 2s{sub 1/2} and 2p{sub 1/2} levels. When the field is weak, it can be treated as a perturbation of these two states separated by a small amount of energy called Lamb-shift. It induces a radiation with intensity proportional to the square modulus of the electric field which is measured in a direction perpendicular to the probe beam. Contrary to measurements in vacuum, the Debye sheath formation is clearly observed in the presence of plasma. This contribution reviews: presentation of Stark mixing of the 2s{sub 1/2} and 2p{sub 1/2} levels and of Lamb shift for hydrogen-like atoms, brief description of the experimental set-up, observation of the formation of a sheath between two polarized plane electrodes in a plasma, either with a probe ion beam, or atom beam.

  10. Direct reaction experimental studies with beams of radioactive tin ions

    SciTech Connect

    Jones, K. L. Ayres, A.; Bey, A.; Burcher, S.; Cartegni, L.; Cerizza, G.; Ahn, S.; Allmond, J. M.; Beene, J. R.; Galindo-Uribarri, A.; Liang, J. F.; Nesaraja, C. D.; Pain, S. D.; Radford, D. C.; Schmitt, K. T.; Smith, M. S.; Stracener, D. W.; Varner, R. L.; Bardayan, D. W.; Baugher, T.; and others

    2015-10-15

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at {sup 100}Sn, through 10 stable isotopes and the N = 82 shell closure at {sup 132}Sn out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich {sup 130}Sn. Both techniques rely on selective particle identification and the measurement of γ rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  11. Direct Reaction Experimental Studies with Beams of Radioactive Tin Ions

    SciTech Connect

    Jones, K. L.; Ahn, S.H.; Allmond, James M; Ayres, A.; Bardayan, Daniel W; Baugher, T.; Bazin, D.; Beene, James R; Berryman, J. S.; Bey, A.; Bingham, C. R.; Cartegni, L.; Chae, K. Y.; Gade, A.; Galindo-Uribarri, Alfredo {nmn}; Garcia-Ruiz, R.F.; Grzywacz, Robert Kazimierz; Howard, Meredith E; Kozub, R. L.; Liang, J Felix; Manning, Brett M; Matos, M.; McDaniel, S.; Miller, D.; Nesaraja, Caroline D; O'Malley, Patrick; Padgett, S; Padilla-Rodal, Elizabeth; Pain, Steven D; Pittman, S. T.; Radford, David C; Ratkiewicz, Andrew J; Schmitt, Kyle; Smith, Michael Scott; Stracener, Daniel W; Stroberg, S.; Tostevin, Jeffrey A; Varner Jr, Robert L; Weisshaar, D.; Wimmer, K.

    2015-01-01

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at Sn-100, through 10 stable isotopes and the N = 82 shell closure at Sn-132 out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich Sn-130. Both techniques rely on selective particle identification and the measurement of gamma rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  12. Investigations on the time evolution of the plasma density in argon electron-beam plasma at intermediate pressure

    NASA Astrophysics Data System (ADS)

    Xiaoyan, BAI; Chen, CHEN; Hong, LI; Wandong, LIU

    2017-03-01

    The time evolution of the argon electron-beam plasma at intermediate pressure and low electron beam intensity was presented. By applying the amplitude modulation with the frequency of 20 Hz on the stable beam current, the plasma evolution was studied. A Faraday cup was used for the measurement of the electron beam current and a single electrostatic probe was used for the measurement of the ion current. Experimental results indicated that the ion current was in phase with the electron beam current in the pressure range from 200 Pa to 3000 Pa and in the beam current range lower than 20 mA, the residual density increased approximately linearly with the maximum density in the log-log plot and the fitting coefficient was irrelative to the pressure. And then three kinds of kinetic models were developed and the simulated results given by the kinetic model, without the consideration of the excited atoms, mostly approached to the experimental results. This indicated that the effect of the excited atoms on the plasma density can be ignored at intermediate pressure and low electron beam current intensity, which can greatly simplify the kinetic model. In the end, the decrease of the plasma density when the beam current was suddenly off was studied based on the simplified model and it was found that the decease characteristic at intermediate pressure was approximate to the one at high pressure at low electron beam intensity, which was in good accordance with the experimental results. Supported by National Natural Science Foundations of China (No. 11375187) and the Foundation of State key Laboratory of China (No. SKLIPR1510).

  13. Modified quadrupole mass analyzer RGA-100 for beam plasma research in forevacuum pressure range

    SciTech Connect

    Zolotukhin, D. B.; Tyunkov, A. V.; Yushkov, Yu. G.; Oks, E. M.

    2015-12-15

    The industrial quadrupole RGA-100 residual gas analyzer was modified for the research of electron beam-generated plasma at forevacuum pressure range. The standard ionizer of the RGA-100 was replaced by three electrode extracting unit. We made the optimization of operation parameters in order to provide the maximum values of measured currents of any ion species. The modified analyzer was successfully tested with beam plasma of argon, nitrogen, oxygen, and hydrocarbons.

  14. Perpendicular diffusion of a dilute beam of charged particles in the PK-4 dusty plasma

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Goree, John

    2015-09-01

    We study the random walk of a dilute beam of projectile dust particles that drift through a target dusty plasma. This random walk is a diffusion that occurs mainly due to Coulomb collisions with target particles that have a different size. In the direction parallel to the drift, projectiles exhibit mobility-limited motion with a constant average velocity. We use a 3D molecular dynamics (MD) simulation of the dust particle motion to determine the diffusion and mobility coefficients for the dilute beam. The dust particles are assumed to interact with a shielded Coulomb repulsion. They also experience gas drag. The beam particles are driven by a prescribed net force that is not applied to the target particles; in the experiments this net force is due to an imbalance of the electric and ion drag forces. This simulation is motivated by microgravity experiments, with the expectation that the scattering of projectiles studied here will be observed in upcoming PK-4 experiments on the International Space Station. Supported by NASA and DOE.

  15. Roughness formation on photoresist during etching examined by HBr plasma-beam

    NASA Astrophysics Data System (ADS)

    Sekine, Makoto; Zhang, Yan; Ishikawa, Kenji; Takeda, Keigo; Kondo, Hiroki; Hori, Masaru; Plasma Nanotechnology Team

    2014-10-01

    For highly precise patterning in device fabrication, it is required to suppress roughness formations on photoresist (PR) polymers during plasma etching. HBr plasma treatment called ``plasma cure'' was proposed to reduce the roughness. By using a beam irradiation, we reported the PR roughness formation in fluorocarbon plasma, and the effect of HBr cure. We report the roughness formation mechanism by surface analyses and power spectral density (PSD) of the roughness. Average slope and roll-off frequency of PSD are characterized by frequency components, the high-frequency roughness. We treated the data for six samples: a) pristine, b) after Ar plasma irradiation, c) after Ar plasma followed by HBr cure, d) after HBr cure, e) after HBr followed by Ar plasma beam, and f) after HBr followed by H2 and Ar plasma beam irradiations. The PSD slopes were changed by each process. Based on the results, we speculated that the Ar-plasma beam formed a crust layer on the PR surface with unrelieved stress and HBr cure may soften the bulk PR to relieve the stress and cause agglomeration of polymers at the size over 10 nm.

  16. Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System

    NASA Astrophysics Data System (ADS)

    Turnbull, D.; Goyon, C.; Kemp, G. E.; Pollock, B. B.; Mariscal, D.; Divol, L.; Ross, J. S.; Patankar, S.; Moody, J. D.; Michel, P.

    2017-01-01

    We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85 %- 87 % extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

  17. Self-focusing of a Gaussian electromagnetic beam in a complex plasma

    SciTech Connect

    Mishra, S. K.; Misra, Shikha; Sodha, M. S.

    2011-04-15

    This paper analyzes the propagation of a Gaussian electromagnetic beam in a complex plasma; the paraxial approach has been invoked for the study of the propagation characteristics. The analytical model emphasizes the open nature of complex plasmas and incorporates the charge, number density, and energy balance of the plasma constituents along with the plasma neutrality. Diffusion due to the density and temperature gradients, thermal conduction, Ohmic heating, and energy exchange in collisions/accretion have also been taken into account. For a numerical appreciation of the results, the critical curves for the propagation of the beam in dark plasmas have been discussed. The dependence of the beam width parameter on distance of propagation has been evaluated for three typical cases viz., of steady divergence, oscillatory divergence, and self-focusing. The equality of electron and ion density, an assumption inherent in the earlier analysis, has been discarded on account of the presence of charged dust particles.

  18. Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System.

    PubMed

    Turnbull, D; Goyon, C; Kemp, G E; Pollock, B B; Mariscal, D; Divol, L; Ross, J S; Patankar, S; Moody, J D; Michel, P

    2017-01-06

    We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85%-87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

  19. Hysteresis effects in the formation of a neutralizing beam plasma at low ion energy

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2013-11-01

    In this paper, the PEGASES II thruster prototype is used as an ion source generating low-energy (<300\\ \\text{eV}) positive Ar ion beam, extracted without an external neutralizer. The ions are extracted and accelerated from the source using a two-grid system. The extracted positive ion beam current is measured on a large beam target that can be translated along the acceleration axis. The ion beam current shows a stepwise transition from a low-current to a high-current extraction regime with hysteresis. The hysteresis region depends strongly upon the beam target position. Langmuir probe measurements in the plume show high plasma potentials and low plasma densities in the low-current mode, while the plasma potential drops and the density increases in the high-current mode. The ion energy distribution functions of the beam are measured for different regimes of ion extraction. The ion beam extracted in the high-current mode is indicated by the presence of an additional low-energy peak corresponding to ions from an ion-beam plasma created in the downstream chamber, as well as 10-20 times higher intensity of the primary ion beam peak. The hysteresis behavior is explained by the formation of a downstream neutralizing beam plasma, that depends on the target position and pressure in agreement with a Paschen-like breakdown by secondary electrons. The obtained results are of high relevance for further development of the PEGASES thruster, as well as for improving existing neutralizer-free concepts of the broad-beam ion sources.

  20. Predictive Calculation of Neutral Beam Heating Plasmas in EAST Tokamak by NUBEAM Code for Certain Parameter Ranges

    NASA Astrophysics Data System (ADS)

    Ni, Qionglin; Fan, Tieshuan; Zhang, Xing; Zhang, Cheng; Ren, Qilong; Hu, Chundong

    2010-12-01

    A predictive calculation is carried out for neutral beam heating of fusion plasmas in EAST by using NUBEAM code under certain plasma conditions. Results calculated are analyzed for different plasma parameters. Relations between major plasma parameters, such as density and temperature, are obtained and key physical processes in the neutral beam heating, including beam power deposition, trapped fraction, heating efficiency, and power loss, are simulated. Other physical processes, such as current-drive, toroidal rotation and neutron emission, are also discussed.

  1. Increasing Extracted Beam Current Density in Ion Thrusters through Plasma Potential Modification

    NASA Astrophysics Data System (ADS)

    Arthur, Neil; Foster, John

    2015-09-01

    A gridded ion thruster's maximum extractable beam current is determined by the space charge limit. The classical formulation does not take into account finite ion drift into the acceleration gap. It can be shown that extractable beam current can be increased beyond the conventional Child-Langmuir law if the ions enter the gap at a finite drift speed. In this work, ion drift in a 10 cm thruster is varied by adjusting the plasma potential relative to the potential at the extraction plane. Internal plasma potential variations are achieved using a novel approach involving biasing the magnetic cusps. Ion flow variations are assessed using simulated beam extraction in conjunction with a retarding potential analyzer. Ion beam current density changes at a given total beam voltage in full beam extraction tests are characterized as a function of induced ion drift velocity as well.

  2. Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

    PubMed

    Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

    2015-01-01

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

  3. New electron beam facility for irradiated plasma facing materials testing in hot cell

    SciTech Connect

    Sakamoto, N.; Kawamura, H.; Akiba, M.

    1995-09-01

    Since plasma facing components such as the first wall and the divertor for the next step fusion reactors are exposed to high heat loads and high energy neutron flux generated by the plasma, it is urgent to develop of plasma facing components which can resist these. Then, we have established electron beam heat facility ({open_quotes}OHBIS{close_quotes}, Oarai Hot-cell electron Beam Irradiating System) at a hot cell in JMTR (Japan Materials Testing Reactor) hot laboratory in order to estimate thermal shock resistivity of plasma facing materials and heat removal capabilities of divertor elements under steady state heating. In this facility, irradiated plasma facing materials (beryllium, carbon based materials and so on) and divertor elements can be treated. This facility consists of an electron beam unit with the maximum beam power of 50kW and the vacuum vessel. The acceleration voltage and the maximum beam current are 30kV (constant) and 1.7A, respectively. The loading time of electron beam is more than 0.1ms. The shape of vacuum vessel is cylindrical, and the mainly dimensions are 500mm in inner diameter, 1000mm in height. The ultimate vacuum of this vessel is 1 x 10{sup -4}Pa. At present, the facility for thermal shock test has been established in a hot cell. And performance estimation on the electron beam is being conducted. Presently, the devices for heat loading tests under steady state will be added to this facility.

  4. Dynamics of laser beams in inhomogeneous electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Cheng, Li-Hong; Tang, Rong-An; Du, Hong-E.; Xue, Ju-Kui

    2015-07-01

    Nonlinear interaction of laser and electron-positron-ion plasmas is investigated by invoking the variational principle and numerical simulation, in terms of a nonlinear Schrödinger equation with inhomogeneities effect. It is shown that the plasma inhomogeneity has great influence on the laser beam dynamics. The laser beam can be self-trapped, focused, or defocused depending on the inhomogeneity character. The linearly decreasing axial plasma density makes the laser beam defocus, while the linearly increasing axial plasma density results in self-trapping of the beam. The self-focusing of the trapped beam is found in a high-density region. For the Gaussian types of density distribution, the beam field submits nonlinearly oscillating regime. The results provide an efficient way to manipulate the dynamics of laser beam propagating in plasma. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274255 and 11305132), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20136203110001), the Natural Science Foundation of Gansu Province, China (Grant No. 2011GS04358), and the Creation of Science and Technology of Northwest Normal University, China (Grant Nos. NWNU-KJCXGC-03-48 and NWNU-LKQN-12-12).

  5. Quasi-steady carbon plasma source for neutral beam injector

    SciTech Connect

    Koguchi, H. Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y.

    2014-02-15

    Carbon plasma is successfully sustained during 1000 s without any carrier gas in the bucket type ionization chamber with cusp magnetic field. Every several seconds, seed plasmas having ∼3 ms duration time are injected into the ionization chamber by a shunting arch plasma gun. The weakly ionized carbon plasma ejected from the shunting arch is also ionized by 2.45 GHz microwave at the electron cyclotron resonance surface and the plasma can be sustained even in the interval of gun discharges. Control of the gun discharge interval allows to keep high pressure and to sustain the plasma for long duration.

  6. Quasi-steady carbon plasma source for neutral beam injector

    NASA Astrophysics Data System (ADS)

    Koguchi, H.; Sakakita, H.; Kiyama, S.; Shimada, T.; Sato, Y.; Hirano, Y.

    2014-02-01

    Carbon plasma is successfully sustained during 1000 s without any carrier gas in the bucket type ionization chamber with cusp magnetic field. Every several seconds, seed plasmas having ˜3 ms duration time are injected into the ionization chamber by a shunting arch plasma gun. The weakly ionized carbon plasma ejected from the shunting arch is also ionized by 2.45 GHz microwave at the electron cyclotron resonance surface and the plasma can be sustained even in the interval of gun discharges. Control of the gun discharge interval allows to keep high pressure and to sustain the plasma for long duration.

  7. Quasi-steady carbon plasma source for neutral beam injector.

    PubMed

    Koguchi, H; Sakakita, H; Kiyama, S; Shimada, T; Sato, Y; Hirano, Y

    2014-02-01

    Carbon plasma is successfully sustained during 1000 s without any carrier gas in the bucket type ionization chamber with cusp magnetic field. Every several seconds, seed plasmas having ∼3 ms duration time are injected into the ionization chamber by a shunting arch plasma gun. The weakly ionized carbon plasma ejected from the shunting arch is also ionized by 2.45 GHz microwave at the electron cyclotron resonance surface and the plasma can be sustained even in the interval of gun discharges. Control of the gun discharge interval allows to keep high pressure and to sustain the plasma for long duration.

  8. Comparison of Plasma Activation of Thin Water Layers by Direct and Remote Plasma Sources

    NASA Astrophysics Data System (ADS)

    Kushner, Mark

    2014-10-01

    Plasma activation of liquids is now being investigated for a variety of biomedical applications. The plasma sources used for this activation can be generally classified as direct (the plasma is in contact with the surface of the liquid) or remote (the plasma does not directly touch the liquid). The direct plasma source may be a dielectric barrier discharge (DBD) where the surface of the liquid is a floating electrode or a plasma jet in which the ionization wave forming the plasma plume reaches the liquid. The remote plasma source may be a DBD with electrodes electrically isolated from the liquid or a plasma jet in which the ionization wave in the plume does not reach the liquid. In this paper, a comparison of activation of thin water layers on top of tissue, as might be encountered in wound healing, will be discussed using results from numerical investigations. We used the modeling platform nonPDPSIM to simulate direct plasma activation of thin water layers using DBDs and remote activation using plasma jets using up to hundreds of pulses. The DBDs are sustained in humid air while the plasma jets consist of He/O2 mixtures flowed into humid air. For similar number of pulses and energy deposition, the direct DBD plasma sources produce more acidification and higher production of nitrates/nitrites in the liquid. This is due to the accumulation of NxOy plasma jets, the convective flow removes many of these species prior to their diffusing into the water or reacting to form higher nitrogen oxides. This latter effect is sensitive to the repetition rate which determines whether reactive species formed during prior pulses overlap with newly produced reactive species. in the gas phase. In the plasma jets, the convective flow removes many of these species prior to their diffusing into the water or reacting to form higher nitrogen oxides. This latter effect is sensitive to the repetition rate which determines whether reactive species formed during prior pulses overlap with

  9. Fluid simulation of relativistic electron beam driven wakefield in a cold plasma

    SciTech Connect

    Bera, Ratan Kumar; Sengupta, Sudip; Das, Amita

    2015-07-15

    Excitation of wakefield in a cold homogeneous plasma, driven by an ultra-relativistic electron beam is studied in one dimension using fluid simulation techniques. For a homogeneous rigid beam having density (n{sub b}) less than or equal to half the plasma density (n{sub 0}), simulation results are found to be in good agreement with the analytical work of Rosenzweig [Phys. Rev. Lett. 58, 555 (1987)]. Here, Rosenzweig's work has been analytically extended to regimes where the ratio of beam density to plasma density is greater than half and results have been verified using simulation. Further in contrast to Rosenzweig's work, if the beam is allowed to evolve in a self-consistent manner, several interesting features are observed in simulation viz. splitting of the beam into beam-lets (for l{sub b} > λ{sub p}) and compression of the beam (for l{sub b} < λ{sub p}), l{sub b} and λ{sub p}, respectively, being the initial beam length and plasma wavelength.

  10. GEANT4 simulations for beam emittance in a linear collider based on plasma wakefield acceleration

    SciTech Connect

    Mete, O. Xia, G.; Hanahoe, K.; Labiche, M.

    2015-08-15

    Alternative acceleration technologies are currently under development for cost-effective, robust, compact, and efficient solutions. One such technology is plasma wakefield acceleration, driven by either a charged particle or laser beam. However, the potential issues must be studied in detail. In this paper, the emittance evolution of a witness beam through elastic scattering from gaseous media and under transverse focusing wakefields is studied.

  11. Diode Dynamics, Beam Generation and Transport and Plasma Erosion Opening Switch Development.

    DTIC Science & Technology

    1983-05-17

    provide standoff protecti.on for the ion diode~s) b) allow close packing of multipla generators saround a coamion target :IiaT.Lr and c) facili- tate tim...beam and plasma parame:ers in w1hich the very intense ion bea= ms behave like weak beams in prescribed electromagnetic fields. As a result, concepts of

  12. PIC Simulations of direct laser accelerated electron from underdense plasmas using the OMEGA EP Laser

    NASA Astrophysics Data System (ADS)

    Hussein, Amina; Batson, Thomas; Krushelnick, Karl; Willingale, Louise; Arefiev, Alex; Wang, Tao; Nilson, Phil; Froula, Dustin; Haberberger, Dan; Davies, Andrew; Theobald, Wolfgang; Williams, Jackson; Chen, Hui

    2016-10-01

    The OMEGA EP laser system is used to study channeling phenomena and direct laser acceleration (DLA) through an underdense plasma. The interaction of a ps laser pulse with a subcritical density CH plasma plume results in the expulsion of electron along the laser axis, forming a positively charged channel. Electrons confined within this channel are subject to the action of the laser field as well as the transverse electric field of the channel, resulting the DLA of these electrons and the formation of a high energy electron beam. We have performed 2D simulations of ultra-intense laser radiation with underdense plasma using the PIC code EPOCH to investigate electron densities and self-consistently generated electric fields, as well as electron trajectories. This work was supported by the National Laser Users' Facility (NLUF), DOE.

  13. Ring formation in self-focusing of electromagnetic beams in plasmas

    SciTech Connect

    Faisal, M.; Mishra, S. K.; Verma, M. P.; Sodha, M. S.

    2007-10-15

    This article presents a paraxial theory of ring formation as an initially Gaussian beam propagates in a nonlinear plasma, characterized by significant collisional or ponderomotive nonlinearity. Regions in the axial irradiance-(beam width){sup -2} space, for which the ring formation occurs and the paraxial theory is valid, have been characterized; for typical points in these regions the dependence of the beam width parameter and the radial distribution of irradiance on the distance has been specifically investigated and discussed.

  14. Improving directivity of laser beams by employing the effect of conical refraction in biaxial crystals.

    PubMed

    Peet, V

    2010-09-13

    The far-field pattern of Gaussian beams transformed by conical refraction in biaxial crystal is analyzed. It is shown that one of the two outgoing beam components acquires, under certain conditions, a profile with a dominating central peak. The width of this peak can be made significantly smaller than the width of the parent diffraction-limited Gaussian beam at the same propagation distance. The formation of such structurally-stable sub-diffraction beam core improves the beam directivity. Another component is a charge-one optical vortex, that forms the annular shell of the beam and carries the rest of the beam power.

  15. Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering.

    PubMed

    Follett, R K; Edgell, D H; Henchen, R J; Hu, S X; Katz, J; Michel, D T; Myatt, J F; Shaw, J; Froula, D H

    2015-03-01

    A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPD EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability.

  16. Characterisation of Plasma Filled Rod Pinch electron beam diode operation

    NASA Astrophysics Data System (ADS)

    MacDonald, James; Bland, Simon; Chittenden, Jeremy

    2016-10-01

    The plasma filled rod pinch diode (aka PFRP) offers a small radiographic spot size and a high brightness source. It operates in a very similar to plasma opening switches and dense plasma focus devices - with a plasma prefill, supplied via a number of simple coaxial plasma guns, being snowploughed along a thin rod cathode, before detaching at the end. The aim of this study is to model the PFRP and understand the factors that affect its performance, potentially improving future output. Given the dependence on the PFRP on the prefill, we are making detailed measurements of the density (1015-1018 cm-3), velocity, ionisation and temperature of the plasma emitted from a plasma gun/set of plasma guns. This will then be used to provide initial conditions to the Gorgon 3D MHD code, and the dynamics of the entire rod pinch process studied.

  17. Exploring a small sawtooth regime in Joint European Torus plasmas with counterinjected neutral beams

    SciTech Connect

    Nave, M.F.F.; Koslowski, H.R.; Coda, S.; Graves, J.; Brix, M.; Buttery, R.; Challis, C.; Giroud, C.; Stamp, M.; Vries, P. de

    2006-01-15

    During a recent reversed toroidal field (B{sub T}) campaign at the Joint European Torus (JET), experiments were performed to investigate the effect on sawteeth of neutral beam injection (NBI)-driven toroidal plasma rotation counter to the direction of the toroidal plasma current and B{sub T}. A power scan at constant density has permitted analytical continuation, into the reversed B{sub T} domain, of previous experiments with forward field and hence corotation. Earlier JET results were confirmed, indicating that counter-NBI results in sawtooth periods shorter than in the Ohmic regime. This study has demonstrated that, whereas with co-NBI the sawtooth period increases with power, with counter-NBI the sawtooth period initially decreases with power passing through a minimum at 4 MW. Clearly this trend also manifests itself in terms of the toroidal plasma rotation, for which a minimum is observed for counter-rotation frequency {approx}3 kHz. Sawteeth smaller than Ohmic sawteeth are found to be easier to obtain with perpendicular counter-NBI, for which heating penetrates deeper into the core. The sign and magnitude of the toroidal rotation, the penetration of heating to the electrons, and the peaking of the fast-ion pressure profile in the core may all play an important role in modifying the sawtooh period.

  18. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    NASA Astrophysics Data System (ADS)

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun; Hu, Liqun; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-01

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey-predator model was found to reproduce the fishbone nonlinear process well.

  19. Fishbone activity in experimental advanced superconducting tokamak neutral beam injection plasma

    SciTech Connect

    Xu, Liqing; Zhang, Jizong; Chen, Kaiyun E-mail: lqhu@ipp.cas.cn; Hu, Liqun E-mail: lqhu@ipp.cas.cn; Li, Erzhong; Lin, Shiyao; Shi, Tonghui; Duan, Yanmin; Zhu, Yubao

    2015-12-15

    Repetitive fishbones near the trapped ion procession frequency were observed for the first time in the neutral beam injection high confinement plasmas in Experimental Advanced Superconducting Tokamak (EAST) tokamak, and diagnosed using a solid-state neutral particle analyzer based on a compact silicon photodiode together with an upgraded high spatial-temporal-resolution multi-arrays soft X-ray (SX) system. This 1/1 typical internal kink mode propagates in the ion-diamagnetism direction with a rotation speed faster than the bulk plasma in the plasma frame. From the SX measurements, this mode frequency is typical of chirping down and the energetic particle effect related to the twisting mode structure. This ion fishbone was found able to trigger a multiple core sawtooth crashes with edge-2/1 sideband modes, as well as to lead to a transition from fishbone to long lived saturated kink mode to fishbone. Furthermore, using SX tomography, a correlation between mode amplitude and mode frequency was found. Finally, a phenomenological prey–predator model was found to reproduce the fishbone nonlinear process well.

  20. High frequency core localized modes in neutral beam heated plasmas on TFTR

    SciTech Connect

    Nazikian, R.; Chang, Z.; Fredrickson, E.D.

    1995-11-01

    A band of high frequency modes in the range 50--150 kHz with intermediate toroidal mode numbers 4 < n < 10 are commonly observed in the core of supershot plasmas on TFTR. Two distinct varieties of MHD modes are identified corresponding to a flute-like mode predominantly appearing around the q = 1 surface and an outward ballooning mode for q > 1. The flute-like modes have nearly equal amplitude on the high field and low field side of the magnetic axis and are mostly observed in moderate performance supershot plasmas with {tau}{sub E} < 2{tau}{sub L} while the ballooning-like modes have enhanced amplitude on the low field side of the magnetic axis and tend to appear in higher performance supershot plasmas with {tau}{sub E} > 2{tau}{sub L}, where {tau}{sub L} is the equivalent L-mode confinement time. The modes propagate in the ion diamagnetic drift direction and are highly localized with radial widths {Delta}r {approximately} 5--10 cm, fluctuation levels {tilde n}/n, {tilde T}{sub e}/T{sub e} < 0.01, and radial displacements {zeta}{sub r} {approximately} 0.1 cm. Unlike the toroidally localized high-n activity observed just prior to major and minor disruptions on TFTR, these modes are typically much weaker, more benign, and may be indicative of kinetic ballooning modes destabilized by resonant circulating neutral beam ions.

  1. Direct nano-patterning of graphene with helium ion beams

    SciTech Connect

    Naitou, Y.; Iijima, T.; Ogawa, S.

    2015-01-19

    Helium ion microscopy (HIM) was used for direct nano-patterning of single-layer graphene (SLG) on SiO{sub 2}/Si substrates. This technique involves irradiation of the sample with accelerated helium ions (He{sup +}). Doses of 2.0 × 10{sup 16 }He{sup + }cm{sup −2} from a 30 kV beam induced a metal-insulator transition in the SLG. The resolution of HIM patterning on SLG was investigated by fabricating nanoribbons and nanostructures. Analysis of scanning capacitance microscopy measurements revealed that the spatial resolution of HIM patterning depended on the dosage of He{sup +} in a non-monotonic fashion. Increasing the dose from 2.0 × 10{sup 16} to 5.0 × 10{sup 16 }He{sup + }cm{sup −2} improved the spatial resolution to several tens of nanometers. However, doses greater than 1.0 × 10{sup 17 }He{sup + }cm{sup −2} degraded the patterning characteristics. Direct patterning using HIM is a versatile approach to graphene fabrication and can be applied to graphene-based devices.

  2. Development of a plasma generator for a long pulse ion source for neutral beam injectors

    SciTech Connect

    Watanabe, K.; Dairaku, M.; Tobari, H.; Kashiwagi, M.; Inoue, T.; Hanada, M.; Jeong, S. H.; Chang, D. H.; Kim, T. S.; Kim, B. R.; Seo, C. S.; Jin, J. T.; Lee, K. W.; In, S. R.; Oh, B. H.; Kim, J.; Bae, Y. S.

    2011-06-15

    A plasma generator for a long pulse H{sup +}/D{sup +} ion source has been developed. The plasma generator was designed to produce 65 A H{sup +}/D{sup +} beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and {+-}7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm{sup 2}.

  3. Study of plasma formation in CW CO2 laser beam-metal surface interaction

    NASA Astrophysics Data System (ADS)

    Azharonok, V. V.; Vasilchenko, Zh V.; Golubev, Vladimir S.; Gresev, A. N.; Zabelin, Alexandre M.; Chubrik, N. I.; Shimanovich, V. D.

    1994-04-01

    An interaction of the cw CO2 laser beam and a moving metal surface has been studied. The pulsed and thermodynamical parameters of the surface plasma were investigated by optical and spectroscopical methods. The subsonic radiation wave propagation in the erosion plasma torch has been studied.

  4. Propagation of a laser beam in a plasma

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.; Steinhauer, L. C.; Vagners, J.

    1975-01-01

    This paper shows that for a nonabsorbing medium with a prescribed index of refraction, the effects of beam stability, line focusing, and beam distortion can be predicted from simple ray optics. When the paraxial approximation is used, diffraction effects are examined for Gaussian, Lorentzian, and square beams. Most importantly, it is shown that for a Gaussian beam, diffraction effects can be included simply by adding imaginary solutions to the paraxial ray equations. Also presented are several procedures to extend the paraxial approximation so that the solution will have a domain of validity of greater extent.

  5. Simulations of beam-fueled supershot-like plasmas near ignition

    SciTech Connect

    Budny, R.V.; Grisham, L.; Jassby, D.L.; Manickam, J.; Mikkelsen, D.; McCune, D.; McGuire, K.M.; Scott, S.D.; Stotler, D.; Wieland, R.; Zarnstorff, M.C.; Zweben, S.J.; Sabbagh, S.A.

    1993-03-01

    Centrally peaked profiles would be advantageous for tokamak reactors since the pressure and the bootstrap current would be peaked in the regions of intense reactivity. We use the TRANSP plasma analysis code to investigate the feasibility of fueling with neutral beam injection. We show that for certain conditions, neutral beams with energies less than 120 keV can penetrate into the cores of plasmas that have a large thermonuclear yield and Q{sub DT} {approximately}10. This value of ODT is too small for an economical reactor if the neutral beam injection is the only fueling source. We give examples for several proposed compact prototype reactor designs.

  6. Simulations of beam-fueled supershot-like plasmas near ignition

    SciTech Connect

    Budny, R.V.; Grisham, L.; Jassby, D.L.; Manickam, J.; Mikkelsen, D.; McCune, D.; McGuire, K.M.; Scott, S.D.; Stotler, D.; Wieland, R.; Zarnstorff, M.C.; Zweben, S.J. . Plasma Physics Lab.); Sabbagh, S.A. )

    1993-03-01

    Centrally peaked profiles would be advantageous for tokamak reactors since the pressure and the bootstrap current would be peaked in the regions of intense reactivity. We use the TRANSP plasma analysis code to investigate the feasibility of fueling with neutral beam injection. We show that for certain conditions, neutral beams with energies less than 120 keV can penetrate into the cores of plasmas that have a large thermonuclear yield and Q[sub DT] [approximately]10. This value of ODT is too small for an economical reactor if the neutral beam injection is the only fueling source. We give examples for several proposed compact prototype reactor designs.

  7. Propagation modes for a dusty plasma ionization instability under electron beam injection

    SciTech Connect

    Donoso, J. M.; Conde, L.

    2008-09-07

    The low frequency electrostatic linear modes of a dusty plasma penetrated by an energized electron beam are investigated in the frame of a one-dimensional multifluid equations. This plasma contains with thermal and non-thermal electrons, ions and charged dust grains. The stable and unstable modes of the ionization instability are examined in relation to the injected electron beam current density. We pay special attention to the relation of the unstable modes and the injected electron current and ionization cross-section dependence with beam energy, which are proved to be the critical parameters for triggering the instability. This latter could be monitored in the laboratory experiments.

  8. Surface waves of high amplitude excited by relativistic electron beam on plasma boundary

    NASA Astrophysics Data System (ADS)

    Bogdanova, S. N.; Reshetnikova, K. A.; Dankov, P. I.; Ivanov, S. T.

    1984-06-01

    The equilibrium state of a relativistic electron beam and a surface EM-wave of large amplitude on the beam-plasma boundary is analysed in hydrodynamic approximation. Taking into consideration the law of conversion of energy, the phase velocity, the wave amplitude, the efficiency of transformation of the kinetic energy into the energy of electromagnetic field and the distribution of the energy of a beam transferred to a system have been obtained. This energy is expended both on excitation of a surface wave and on plasma electrons oscillations.

  9. Experience with deuterium-tritium plasmas heated by high power neutral beams

    SciTech Connect

    Grisham, L.R.; Kamperschroer, J.H.; O`Connor, T.; Oldaker, M.; Stevenson, T.; Von Halle, A.

    1996-12-31

    The Tokamak Fusion Test Reactor has operated since November of 1993 with a deuterium-tritium fuel mixture for selected discharges. The majority of the tritium has been introduced as energetic neutral atoms of up to 120 keV injected by the neutral beam systems, with some of the twelve ion sources run on pure tritium and some on deuterium to optimize the fuel mixture in the core plasma. A maximum beam power of 39.6 megawatts has been injected, and deuterium-tritium fusion power production has reached 10.7 megawatts, achieving central fusion power densities comparable to or greater than those expected for the International Thermonuclear Reactor, and allowing the first studies of fusion-produced alpha particle behavior in reactor grade plasmas. Energy confinement in deuterium-tritium plasmas is better than in similar deuterium plasmas for most plasma regimes. Innovative techniques to manipulate the plasma current and pressure profiles are permitting studies of enhanced confinement regimes.

  10. Beam heated linear theta-pinch device for producing hot plasmas

    DOEpatents

    Bohachevsky, Ihor O.

    1981-01-01

    A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

  11. Ion-acoustic solitary waves in a positron beam plasma with electron trapping and nonextensivity effects

    NASA Astrophysics Data System (ADS)

    Ali Shan, S.; -Ur-Rehman, Aman; Mushtaq, A.

    2017-03-01

    Ion-acoustic solitary waves (IASWs) are investigated in a plasma having a cold positron beam fluid, electrons following a vortex-like distribution with entropic index q, and dynamic ions. Using a standard procedure, a pseudo-potential energy equation is derived. The presence of nonextensive q - distributed trapped electrons and cold positron beam has been shown to influence the small amplitude soliton structure quite significantly. From the analysis of our results, it is shown that compressive IASWs are supported in this plasma model. As the real plasma situations are observed with plasma species having a relative flow, our present analysis should be beneficial for comprehending the electrostatic solitary structures observed in fusion plasma devices and positron winds observed in astrophysical plasmas.

  12. Study of plasma confinement in ELMO Bumpy Torus with a heavy-ion beam probe

    SciTech Connect

    Bieniosek, F. M.

    1981-01-01

    Plasma confinement in ELMO Bumpy Torus (EBT) is generally strongly dependent on an ambipolar electric field. Spatially resolved measurements of the resulting electric space potential phi/sub sp/ have been made in a single plasma cross section by the heavy-ion beam probe. This diagnostic injects a 4-60-keV beam of (usually) Cs/sup +/ ions into the plasma. Measurement of the energy of Cs/sup 2 +/ secondary ions leaving the plasma gives a continuous monitor of the local space potential. In addition, the total detected Cs/sup 2 +/ ion current is proportional to the product of the local electron density and the ionization rate, which, in turn, is a function of the electron temperature. This signal, nf(T/sub e/), is sensitive to all three electron distributions found in EBT - those of the cold surface plasma, the warm core plasma, and the hot electron ring.

  13. Shielding analysis for a heavy ion beam chamber with plasma channels for ion transport

    SciTech Connect

    Sawan, M.E.; Peterson, R.R.; Yu, S.

    2000-06-28

    Neutronics analysis has been performed to assess the shielding requirements for the insulators and final focusing magnets in a modified HYLIFE-II target chamber that utilizes pre-formed plasma channels for heavy ion beam transport. Using 65 cm thick Flibe jet assemblies provides adequate shielding for the electrical insulator units. Additional shielding is needed in front of the final focusing superconducting quadrupole magnets. A shield with a thickness varying between 45 and 90 cm needs to be provided in front of the quadrupole unit. The final laser mirrors located along the channel axis are in the direct line-of-sight of source neutrons. Neutronics calculations were performed to determine the constraints on the placement of these mirrors to be lifetime components.

  14. Rare-earth neutral metal injection into an electron beam ion trap plasma

    SciTech Connect

    Magee, E. W. Beiersdorfer, P.; Brown, G. V.; Hell, N.

    2014-11-15

    We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10{sup −7} Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

  15. Dynamics of a helium plasma sheet created by a hollow-cathode electron beam

    NASA Astrophysics Data System (ADS)

    Larigaldie, S.; Caillault, L.

    2000-12-01

    A hollow-cathode device has been shown to operate as a plasma reflector for electronic steering of radar beams using helium in the 0.2-0.5 Torr pressure range. Compared to previous experiments, the use of this light gas significantly reduces the spurious sputtering effects on the cathode materials. A semi-quantitative physical model was developed to describe the observed evolution of microwave beam transmissions through the plasma sheet as a function of frequency. This model stresses the importance of electron-ion recombination on the edge of the plasma sheet, due to simultaneous low electron temperatures and high electron densities.

  16. Extension of Plasma Source Ion Implantation to Ion Beam Enhanced Deposition

    DTIC Science & Technology

    1989-10-05

    22, 90 (1989). Nitriding/ Carburizing , Cincinnati, Ohio, Septem- 51. M. A. Lieberman, "Model of Plasma Immersion Ion ber 16-20, 1989. Implantation...TYPE AND OATES COVERED 1990 Final I Feb 89 - 31 Jul 89 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Extension of Plasma Source Ion Implantation to Ion Beam...UL NSN 7540-01.280-5500 Standard Form 298 (Rev 2-89) *’@Krab OV ANSI St 139-IS t9-0 Extension of Plasma Source Ion Implantation to Ion Beam Enhanced

  17. Decomposition of chlorinated ethylenes and ethanes in an electron beam generated plasma reactor

    SciTech Connect

    Vitale, Steven A.

    1996-02-01

    An electron beam generated plasma reactor (EBGPR) is used to determine the plasma chemistry kinetics, energetics and decomposition pathways of six chlorinated ethylenes and ethanes: 1,1,1-trichloroethane, 1,1-dichloroethane, ethyl chloride, trichloroethylene, 1,1-dichloroethylene, and vinyl chloride. A traditional chemical kinetic and chemical engineering analysis of the data from the EBGPR is performed, and the following hypothesis was verified: The specific energy required for chlorinated VOC decomposition in the electron beam generated plasma reactor is determined by the electron attachment coefficient of the VOC and the susceptibility of the molecule to radical attack. The technology was demonstrated at the Hanford Reservation to remove VOCs from soils.

  18. Electron trapping and acceleration by the plasma wakefield of a self-modulating proton beam

    SciTech Connect

    Lotov, K. V.; Sosedkin, A. P.; Petrenko, A. V.; Amorim, L. D.; Vieira, J.; Fonseca, R. A.; Silva, L. O.; Gschwendtner, E.; Muggli, P.

    2014-12-15

    It is shown that co-linear injection of electrons or positrons into the wakefield of the self-modulating particle beam is possible and ensures high energy gain. The witness beam must co-propagate with the tail part of the driver, since the plasma wave phase velocity there can exceed the light velocity, which is necessary for efficient acceleration. If the witness beam is many wakefield periods long, then the trapped charge is limited by beam loading effects. The initial trapping is better for positrons, but at the acceleration stage a considerable fraction of positrons is lost from the wave. For efficient trapping of electrons, the plasma boundary must be sharp, with the density transition region shorter than several centimeters. Positrons are not susceptible to the initial plasma density gradient.

  19. Observation of weakly and strongly diverging ion beams in a magnetically expanding plasma

    SciTech Connect

    Takahashi, K.; Fujiwara, T.

    2009-02-09

    The spatial distribution of an ion beam created in a magnetically expanding plasma using permanent magnets is experimentally investigated for 0.35 and 1 mTorr, where the magnetic-field strength is about 100 G in the plasma source and is decreasing into a few gauss in the diffusion chamber. The beam profile for 0.35 mTorr is weakly divergent. On the other hand, the strongly diverging beam is detected for 1 mTorr. The results are discussed from the viewpoint of the plasma-potential structures and imply the beam divergence caused by the radial electric fields in the ion acceleration region and the diffusion chamber.

  20. The effect of boundaries on the ion acoustic beam-plasma instability in experiment and simulation

    SciTech Connect

    Rapson, Christopher; Grulke, Olaf; Matyash, Konstantin; Klinger, Thomas

    2014-05-15

    The ion acoustic beam-plasma instability is known to excite strong solitary waves near the Earth's bow shock. Using a double plasma experiment, tightly coupled with a 1-dimensional particle-in-cell simulation, the results presented here show that this instability is critically sensitive to the experimental conditions. Boundary effects, which do not have any counterpart in space or in most simulations, unavoidably excite parasitic instabilities. Potential fluctuations from these instabilities lead to an increase of the beam temperature which reduces the growth rate such that non-linear effects leading to solitary waves are less likely to be observed. Furthermore, the increased temperature modifies the range of beam velocities for which an ion acoustic beam plasma instability is observed.

  1. Plasma Response to Supersonic Molecular Beam Injection in J-TEXT

    NASA Astrophysics Data System (ADS)

    Xiao, Jinshui; Yang, Zhoujun; Zhuang, Ge; Hu, Qiming; Feng, Xiande; Liu, Minghai

    2014-01-01

    Recently, hydrogen fueling experiments with supersonic molecular beam injection (SMBI) system have been performed in the J-TEXT tokamak. To evaluate the effects of the injection amount of SMBI on plasma behaviors, moderate and intensive SMBs have been separately injected and compared with each other in Ohmic discharges. With moderate SMBs, electron density increases about twice as before, the size of magnetic island slightly decreases, and the edge toroidal rotation speed in a counter-current direction, measured by a high resolution spectrometer (Carbon V ion, 227.09 nm, r/a = 0.7-0.8), is accelerated from 8 km/s to 12 km/s. The state of higher electron density with moderate SMBI can be maintained for a long period, which indicates that plasma confinement is improved. However, with intensive SMBs, the accompanied magnetohydrodynamic (MHD) activities are triggered, and the electron density increases moderately. The edge toroidal velocity is decreased, in certain cases even reversed in the co-current direction. The statistical result of experimental data for moderate and intensive SMBs suggests a preferred fueling amount (less than 3.2×1019) to improve the SMBI fueling efficiency in experiments.

  2. Current neutralization and focusing of intense ion beams with a plasma-filled solenoidal lens. I

    SciTech Connect

    Oliver, B.V.; Sudan, R.N.

    1996-12-01

    The response of the magnetized plasma in an axisymmetric, plasma-filled, solenoidal magnetic lens, to intense light ion beam injection is studied. The lens plasma fill is modeled as an inertialess, resistive, electron magnetohydrodynamic (EMHD) fluid since characteristic beam times {tau} satisfy 2{pi}/{omega}{sub {ital pe}},2{pi}/{Omega}{sub {ital e}}{lt}{tau}{le}2{pi}/{Omega}{sub {ital i}} ({omega}{sub {ital pe}} is the electron plasma frequency and {Omega}{sub {ital e},{ital i}} are the electron, ion gyrofrequencies). When the electron collisionality satisfies {nu}{sub {ital e}}{lt}{Omega}{sub {ital e}}, the linear plasma response is determined by whistler wave dynamics. In this case, current neutralization of the beam is reduced on the time scale for whistler wave transit across the beam. The transit time is inversely proportional to the electron density and proportional to the angle of incidence of the beam with respect to the applied solenoidal field. In the collisional regime ({nu}{sub {ital e}}{gt}{Omega}{sub {ital e}}) the plasma return currents decay on the normal diffusive time scale determined by the conductivity. The analysis is supported by two-and-one-half dimensional hybrid particle-in-cell simulations. {copyright} {ital 1996 American Institute of Physics.}

  3. Spontaneous excitation of waves by an intense ion beam on the Large Plasma Device

    NASA Astrophysics Data System (ADS)

    Tripathi, Shreekrishna; van Compernolle, Bart; Gekelman, Walter; Pribyl, Patrick; Heidbrink, William

    2016-10-01

    A hydrogen ion beam (15 keV, 10 A) has been injected into a large magnetized plasma (n 1010 -1013 cm-3, Te = 5.0 - 15.0 eV, B = 0.6 - 1.8 kG, He+ and H+ ions, 19 m long, 0.6 m diameter) for performing fast-ion studies on the Large Plasma Device (LAPD). The beam forms a helical orbit (pitch-angle 7° -55°), propagates with an Alfvénic speed (beam-speed/Alfvén-speed = 0.2 - 3.0), and significantly enhances the electron temperature and density when injected during the plasma afterglow. We report results on spontaneous generation of Alfvén waves and electrostatic waves in the lower-hybrid range of frequencies by the beam. Roles of normal and anomalous Doppler-shifted ion-cyclotron resonances in destabilizing the Alfvén waves were examined by measuring the phase-speed of waves and relevant parameters of the plasma using a variety of diagnostic tools (retarding-field energy analyzer, three-axis magnetic-loop, Dipole, and Langmuir probes). Conditions for the maximum growth of these waves were determined by varying the parameters of the beam and ambient plasma and examining the mode-structures in the fluctuation-spectra. Work jointly supported by US DOE and NSF and performed at the Basic Plasma Science Facility, UCLA.

  4. Direct linear term in the equation of state of plasmas.

    PubMed

    Kraeft, W D; Kremp, D; Röpke, G

    2015-01-01

    We discuss a long-standing discrepancy in the equation of state of charge-neutral plasmas, the occurrence of an e(2) direct term. This e(2) term may appear in dependence of the way to determine the mean value of the potential energy. We show that such a contribution should not appear for pure Coulomb interaction.

  5. Pulse thermal processing of functional materials using directed plasma arc

    DOEpatents

    Ott, Ronald D.; Blue, Craig A.; Dudney, Nancy J.; Harper, David C.

    2007-05-22

    A method of thermally processing a material includes exposing the material to at least one pulse of infrared light emitted from a directed plasma arc to thermally process the material, the pulse having a duration of no more than 10 s.

  6. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    NASA Astrophysics Data System (ADS)

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  7. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma.

    PubMed

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  8. MM-wave emission by magnetized plasma during sub-relativistic electron beam relaxation

    SciTech Connect

    Ivanov, I. A. Arzhannikov, A. V.; Burmasov, V. S.; Popov, S. S.; Postupaev, V. V.; Sklyarov, V. F.; Vyacheslavov, L. N.; Burdakov, A. V.; Sorokina, N. V.; Gavrilenko, D. E.; Kasatov, A. A.; Kandaurov, I. V.; Mekler, K. I.; Rovenskikh, A. F.; Trunev, Yu. A.; Kurkuchekov, V. V.; Kuznetsov, S. A.; Polosatkin, S. V.

    2015-12-15

    There are described electromagnetic spectra of radiation emitted by magnetized plasma during sub-relativistic electron beam in a double plasma frequency band. Experimental studies were performed at the multiple-mirror trap GOL-3. The electron beam had the following parameters: 70–110 keV for the electron energy, 1–10 MW for the beam power and 30–300 μs for its duration. The spectrum was measured in 75–230 GHz frequency band. The frequency of the emission follows variations in electron plasma density and magnetic field strength. The specific emission power on the length of the plasma column is estimated on the level 0.75 kW/cm.

  9. MM-wave emission by magnetized plasma during sub-relativistic electron beam relaxation

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Arzhannikov, A. V.; Burdakov, A. V.; Burmasov, V. S.; Gavrilenko, D. E.; Kasatov, A. A.; Kandaurov, I. V.; Kurkuchekov, V. V.; Kuznetsov, S. A.; Mekler, K. I.; Polosatkin, S. V.; Popov, S. S.; Postupaev, V. V.; Rovenskikh, A. F.; Sklyarov, V. F.; Sorokina, N. V.; Trunev, Yu. A.; Vyacheslavov, L. N.

    2015-12-01

    There are described electromagnetic spectra of radiation emitted by magnetized plasma during sub-relativistic electron beam in a double plasma frequency band. Experimental studies were performed at the multiple-mirror trap GOL-3. The electron beam had the following parameters: 70-110 keV for the electron energy, 1-10 MW for the beam power and 30-300 μs for its duration. The spectrum was measured in 75-230 GHz frequency band. The frequency of the emission follows variations in electron plasma density and magnetic field strength. The specific emission power on the length of the plasma column is estimated on the level 0.75 kW/cm.

  10. Excitation of surface modes by electron beam in semi-bounded quantum plasma

    SciTech Connect

    Mohamed, B. F.; Elbasha, N. M.

    2015-10-15

    The excitation of the TM surface modes due to the interaction of electron beam with a semi-bounded quantum magnetized plasma is investigated. The generated current and the perturbed densities of the electron beam and plasma are obtained. The wave equation that describes the excited fields has been solved to obtain the dispersion relation for these modes. It is found that the quantum effects play important role for frequencies less and bigger than plasma frequency such that the phase velocity of modes increases with increasing the quantum effects compared to the classical case. It has also been displayed that in the absence of external magnetic field, the surface modes appear in the all regions of the wavelength while they have been only excited for high wavenumber in the presence of the magnetic field. Besides, it has been shown that the dispersion curves of the modes depend essentially on the density ratio of beam and plasma.

  11. Generation of Quasi-monoenergetic High-energy Electron Beam by Plasma Wave

    SciTech Connect

    Koyama, K.; Saito, N.; Ogata, A.; Masuda, S.; Tanimoto, M.; Miura, E.; Kato, S.; Adachi, M

    2004-12-07

    We have demonstrated an acceleration of a quasi-monoenergetic electron beam by trapping electrons in a plasma wave. Experiments were performed by focusing 2-TW (50 fs) laser pulses on supersonic gas jet targets. An intensity was 5 x 1018W/cm2(a0 = 1.5). An electron density was estimated to be 1.3 x 1020cm-3. The quasi-monoenergetic electron beam at 7 MeV was observed with a peak to foot ratio of 10. An appearance of a Stokes Raman satellite in the forward scattering well correlated with the quasi-monoenergetic electron beam. A frequency shift of the satellite coincided with a plasma frequency at the measured plasma density. Appearance of the Raman satellite coincided with appearances of a fishbone structure in a side-scattering image. Supposing the fishbone structure originated from the plasma wave, an acceleration length was estimated to be 200 to 500 microns.

  12. Observation of optical transition radiation from electron beams generated by laser plasma accelerator

    NASA Astrophysics Data System (ADS)

    Lin, Chen; Nakamura, K.; Van, Tilborg J.; Gonsalves, A. J.; Sokollik, T.; Shiraishi, S.; Leemans, W. P.; Guo, Zhi-Yu

    2013-02-01

    Laser plasma accelerators (LPAs) have made great progress, achieving electron beam with energy up to 1 GeV from a centimeter scale capillary plasma waveguide. Here, we report the measurement of optical transition radiation (OTR) from the capillary-based LPA electron beams. Transition radiation images, produced by electrons passing through two separate foils (located at 2.3 m and 3.8 m away from the exit of the LPA) were recorded with a high resolution imaging system, respectively. Two magnetic quadrupole lenses were placed right after the capillary to focus and collimate the electron beams. Significant localized spikes appeared in the OTR images when the electron beam was focused by the magnetic quadrupole lenses, indicating the coherence of the radiation and the existence of ultrashort longitudinal structures inside the electron beam.

  13. Measuring of plasma properties induced by non-vacuum electron beam welding

    SciTech Connect

    Reisgen, U.; Schleser, M.; Abdurakhmanov, A.; Gumenyuk, A.

    2012-01-15

    Electron beam plasma measurement was realised by means of DIABEAM system invented by ISF RWTH Aachen. The Langmuir probe method is used for measurement. The relative simplicity of the method and the possibility of dispersion of high power on the probe allow its application for the investigation of high-power electron beams. The key element of the method is a rotating thin tungsten wire, which intersects the beam transversely on its axis and collects part of the current by itself. The signals, which are registered in the DIABEAM as a voltage, were taken in the form of amplitude. The conversion of the probe current into the distribution along the beam radius was realised using the Abel's method. A voltage-current characteristic was built for the beam current. The local electron density as well as the electron temperature, the floating potential and the plasma potential were measured and calculated by means of this characteristic.

  14. Measuring of plasma properties induced by non-vacuum electron beam welding

    NASA Astrophysics Data System (ADS)

    Reisgen, U.; Schleser, M.; Abdurakhmanov, A.; Gumenyuk, A.

    2012-01-01

    Electron beam plasma measurement was realised by means of DIABEAM system invented by ISF RWTH Aachen. The Langmuir probe method is used for measurement. The relative simplicity of the method and the possibility of dispersion of high power on the probe allow its application for the investigation of high-power electron beams. The key element of the method is a rotating thin tungsten wire, which intersects the beam transversely on its axis and collects part of the current by itself. The signals, which are registered in the DIABEAM as a voltage, were taken in the form of amplitude. The conversion of the probe current into the distribution along the beam radius was realised using the Abel's method. A voltage-current characteristic was built for the beam current. The local electron density as well as the electron temperature, the floating potential and the plasma potential were measured and calculated by means of this characteristic.

  15. Positron Acceleration by Plasma Wakefields Driven by a Hollow Electron Beam

    NASA Astrophysics Data System (ADS)

    Jain, Neeraj; Antonsen, T. M.; Palastro, J. P.

    2015-11-01

    A scheme for positron plasma wakefield acceleration using hollow or donut-shaped electron driver beams is studied. An annular-shaped, electron-free region forms around the hollow driver beam, creating a favorable region (longitudinal field is accelerating and transverse field is focusing) for positron acceleration. For Facility for Advanced Accelerator Experimental Tests (FACET)-like parameters, the hollow beam driver produces accelerating gradients on the order of 10 GV /m . The accelerating gradient increases linearly with the total charge in the driver beam. Simulations show acceleration of a 23-GeV positron beam to 35.4 GeV with a maximum energy spread of 0.4% and very small emittance over a plasma length of 140 cm is possible.

  16. Anomalous Beam-Ion Loss in TFTR Reversed Magnetic Shear Plasmas

    SciTech Connect

    Ruskov, E.; Bell, M.; Budny, R.V.; McCune, D.C.; Medley, S.S.; Redi, M.H.; Scott, S.; Synakowski, E.J.; von Goeler, S.; White, R.B.; Zweben, S.J.

    1999-02-01

    Anomalous beam-ion loss has been observed in an experiment with short tritium beam pulses injected into deuterium-beam-heated Tokamak Fusion Test Reactor plasmas (P{sub NBI}=15 thinspthinspMW) with reversed magnetic shear (RS). Comparisons of the measured total 14thinspthinspMeV neutron emission, the neutron flux along eight radial locations, and the perpendicular plasma stored energy with predictions from an extensive set of TRANSP simulations suggest that about 40{percent} beam power is lost on a time scale much shorter than the tritium beam pulse length {Delta}t=70 thinspthinspms. In contrast with recent results [K. Tobita {ital et al.,} Nucl.thinspthinspFusion {bold 37}, 1583 (1997)] from RS experiments at JT-60U, we were not able to show conclusively that magnetic field ripple is responsible for this anomaly. {copyright} {ital 1999} {ital The American Physical Society}

  17. Anomalous Beam-Ion Loss in TFTR Reversed Magnetic Shear Plasmas

    NASA Astrophysics Data System (ADS)

    Ruskov, E.; Bell, M.; Budny, R. V.; McCune, D. C.; Medley, S. S.; Redi, M. H.; Scott, S.; Synakowski, E. J.; von Goeler, S.; White, R. B.; Zweben, S. J.

    1999-02-01

    Anomalous beam-ion loss has been observed in an experiment with short tritium beam pulses injected into deuterium-beam-heated Tokamak Fusion Test Reactor plasmas ( PNBI = 15 MW) with reversed magnetic shear (RS). Comparisons of the measured total 14 MeV neutron emission, the neutron flux along eight radial locations, and the perpendicular plasma stored energy with predictions from an extensive set of TRANSP simulations suggest that about 40% beam power is lost on a time scale much shorter than the tritium beam pulse length Δt = 70 ms. In contrast with recent results [K. Tobita et al., Nucl. Fusion 37, 1583 (1997)] from RS experiments at JT-60U, we were not able to show conclusively that magnetic field ripple is responsible for this anomaly.

  18. Anomalous electron heating and energy balance in an ion beam generated plasma

    SciTech Connect

    Guethlein, G.

    1987-04-01

    The plasma described in this report is generated by a 15 to 34 kV ion beam, consisting primarily of protons, passing through an H/sub 2/ gas cell neutralizer. Plasma ions (or ion-electron pairs) are produced by electron capture from (or ionization of) gas molecules by beam ions and atoms. An explanation is provided for the observed anomalous behavior of the electron temperature (T/sub e/): a step-lite, nearly two-fold jump in T/sub e/ as the beam current approaches that which minimizes beam angular divergence; insensitivity of T/sub e/ to gas pressure; and the linear relation of T/sub e/ to beam energy.

  19. Unfolding ambient electron plasma density from wave spectra induced by electron beam

    NASA Astrophysics Data System (ADS)

    Kiraga, A.; Klos, Z.; Oraevsky, V.; Dokukin, V.; Pulinets, S.

    Numerous rocket and few satellite projects were devoted to study of astrophysical plasma with the aid of active electron beam experiments. The quality and volume of wave data from such experiments did not fulfill original expectat ions due to complexity of involved processes, technical malfunctions and limited diagnostics. Due to fortunate, temporal malfunction of plasma accelerator, there were several cases when pulsed electron beam had been injected from the APEX satellite into otherwise unmodified ionospheric plasma. Instantaneous current intensity didn't exceeded 0.15A and an unstabilized acceleration voltage was of the order of 10keV. Injection pitch angle slowly changed according to moderate three-axis satellite stabilization. Injections took place in the altitude range 400-1100km in the European region and in the north, polar region. A receiver with bandwidth of 15kHz was connected to a cylindrical dipole antenna having half lengths of 7.5m. The receiver operated in survey mode providing one spectrum every 2s or 8s. The single spectrum was measured in 1s with an equally spaced mesh of 200 frequencies starting from 100kHz with a step of 50kHz. Electron beam induced spectra show up large variety of narrow band structures. In many cases, from reproducibility or slow evolution of the spectra, it may be inferred that distinct interactions prevail for some ranges of ambient electron gyro (fc) and plasma (fn) frequencies, injection pitch angles and beam intensity. Interaction plausibility arguments are useful in preliminary assignment of spectral structures. We show that discrete emission can be identified at least on ambient plasma frequency or ambient upper hybrid frequency. One class of arguments supporting such identification is provided by interrelation between spectral signatures of local plasma density in passive mode and beam induced spectra. Another class of arguments is provided by interrelations between spectral structures induced by electron beam

  20. Electron Acoustic Waves Generated in SRS by Beam-Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Focia, R. J.; Bers, A.; Ram, A. K.; Shoucri, M. M.

    2001-10-01

    In recent single hot spot laser-plasma experiments on the Los Alamos National Laboratory TRIDENT laser, stimulated scattering was observed at a frequency and phase velocity (ω ≈ 0.4 ω_pe, v_φ ≈ 1.4 v_e) below that of the usual SRS electron plasma wave (EPW).(D. S. Montgomery et al., LANL Report LA-UR-01-1857.) This mode has the characteristics of an electron acoustic wave (EAW). We suggest that this new mode is generated by the interaction of an energetic beam of electrons, produced by nonlinear trapping in the SRS-EPW, with the background plasma. Using a bi-Maxwellian electron distribution function to model the beam-plasma system, we find that, in addition to the usual beam-plasma mode, there exists another mode with characteristic features of an EAW. The weakly damped EAW, obtained from the dispersion relation with the complete plasma dispersion function, exists for parameters consistent with the experiments. EAW features will be presented. The validity of the beam-plasma model is also being studied with an Eulerian-Vlasov code which allows for the nonlinear evolution of the electron distribution function in SRS.

  1. Laser Doppler velocity measurement without directional ambiguity by using frequency shifted incident beams

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.

    1970-01-01

    Laser Doppler heterodyning system for velocity measurements without directional ambiguity, employing incident beams of different frequencies through rotating diffraction grating or Bragg cell application

  2. Lyman-α radiation of a probing metastable hydrogen beam to measure electric fields in diluted fluids and plasmas

    SciTech Connect

    Doveil, F.; Lejeune, A.; Chérigier-Kovacic, L.

    2013-05-15

    The interaction between a metastable H(2s) atomic hydrogen beam and an external electric field leads to the emission of the Lyman-α line. It originates in the Stark mixing of the near-degenerate 2s{sub 1/2} and 2p{sub 1/2} levels separated by the Lamb shift. The quenched radiation proportional to the square of the electric field amplitude is recovered in vacuum by using such an atomic probe beam. For larger electric field, saturation is observed and related to the beam finite transit time. We also observe the strong enhancement of the signal when the field is oscillating at the Lamb shift frequency. This technique is applied in a plasma, offering an alternative way to measure weak electric fields by direct and non-intrusive means.

  3. Ion-beam driven lower hybrid waves in a magnetized dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri; Sharma, Suresh C.; Gupta, Ruby

    2013-06-15

    An ion beam drives lower hybrid waves to instability in a magnetized dusty plasma via Cerenkov interaction. A dispersion relation and the growth rate of the lower hybrid waves have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave instability increase with relative density of negatively charged dust grains. The lower hybrid modes with phase velocity comparable to the beam velocity possess a large growth rate. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density.

  4. Impact of plasma noise on a direct thrust measurement system.

    PubMed

    Pottinger, S J; Lamprou, D; Knoll, A K; Lappas, V J

    2012-03-01

    In order to evaluate the accuracy and sensitivity of a pendulum-type thrust measurement system, a linear variable differential transformer (LVDT) and a laser optical displacement sensor have been used simultaneously to determine the displacement resulting from an applied thrust. The LVDT sensor uses an analog interface, whereas the laser sensor uses a digital interface to communicate the displacement readings to the data acquisition equipment. The data collected by both sensors show good agreement for static mass calibrations and validation with a cold gas thruster. However, the data obtained using the LVDT deviate significantly from that of the laser sensor when operating two varieties of plasma thrusters: a radio frequency (RF) driven plasma thruster, and a DC powered plasma thruster. Results establish that even with appropriate shielding and signal filtering the LVDT sensor is subject to plasma noise and radio frequency interactions which result in anomalous thrust readings. Experimental data show that the thrust determined using the LVDT system in a direct current plasma environment and a RF discharge is approximately a factor of three higher than the thrust values obtained using a laser sensor system for the operating conditions investigated. These findings are of significance to the electric propulsion community as LVDT sensors are often utilized in thrust measurement systems and accurate thrust measurement and the reproducibility of thrust data is key to analyzing thruster performance. Methods are proposed to evaluate system susceptibility to plasma noise and an effective filtering scheme presented for DC discharges.

  5. Optical fiber tip templating using direct focused ion beam milling.

    PubMed

    Micco, A; Ricciardi, A; Pisco, M; La Ferrara, V; Cusano, A

    2015-11-04

    We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a 'double-layer' photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology.

  6. Optical fiber tip templating using direct focused ion beam milling

    PubMed Central

    Micco, A.; Ricciardi, A.; Pisco, M.; La Ferrara, V.; Cusano, A.

    2015-01-01

    We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a ‘double-layer’ photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology. PMID:26531887

  7. Measuring Broadband IR Irradiance in the Direct Solar Beam (Poster)

    SciTech Connect

    Reda, I.; Konings, J.; Xie, Y.; Dooraghi, M.; Sengupta, M.

    2015-03-01

    Solar and atmospheric science radiometers, e.g. pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to a consensus reference, which is maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity with no window, developed to measure extended broadband direct solar irradiance beyond the ultraviolet and infrared bands below and above 0.2 micrometers and 50 micrometers, respectively. On the other hand, pyranometers and pyrheliometers are developed to measure broadband shortwave irradiance from approximately 0.3 micrometers to 3 micrcometers, while the present photovoltaic cells are limited to approximately 0.3 micrometers to 1 micrometers. The broadband mismatch of ACR versus such radiometers causes discrepancy in radiometers' calibration methods that has not been discussed or addressed in the solar and atmospheric science literature. Pyrgeometers are also used for solar and atmospheric science applications and calibrated with traceability to consensus reference, yet calibrated during nighttime only, because no consensus reference has yet been established for the daytime longwave irradiance. This poster shows a method to measure the broadband IR irradiance in the direct solar beam from 3 micrometers to 50 micrometers, as first step that might be used to help develop calibration methods to address the mismatch between broadband ACR and shortwave radiometers, and the lack of a daytime reference for pyrgeometers. The irradiance was measured from sunrise to sunset for 5 days when the sun disk was cloudless; the irradiance varied from approximately 1 Wm-2 to 16 Wm-2 for solar zenith angle from 80 degres to 16 degrees respectively; estimated uncertainty is 1.5 Wm-2.

  8. Measuring Broadband IR Irradiance in the Direct Solar Beam (Presentation)

    SciTech Connect

    Reda, I.

    2015-03-01

    Solar and atmospheric science radiometers, e.g. pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to a consensus reference, which is maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity with no window, developed to measure extended broadband direct solar irradiance beyond the ultraviolet and infrared bands below and above 0.2 um and 50 um, respectively. On the other hand, pyranometers and pyrheliometers are developed to measure broadband shortwave irradiance from approximately 0.3 um to 3 um, while the present photovoltaic cells are limited to approximately 0.3 um to 1 um. The broadband mismatch of ACR versus such radiometers causes discrepancy in radiometers' calibration methods that has not been discussed or addressed in the solar and atmospheric science literature. Pyrgeometers are also used for solar and atmospheric science applications and are calibrated with traceability to consensus reference, yet are calibrated during nighttime only, because no consensus reference has yet been established for the daytime longwave irradiance. This poster shows a method to measure the broadband IR irradiance in the direct solar beam from 3 um to 50 um, as a first step that might be used to help develop calibration methods to address the mismatch between broadband ACR and shortwave radiometers, and the lack of a daytime reference for pyrgeometers. The irradiance was measured from sunrise to sunset for 5 days when the sun disk was cloudless; the irradiance varied from approximately 1 Wm-2 to 16 Wm-2 for solar zenith angle from 80 degrees to 16 degrees respectively; estimated uncertainty is 1.5 Wm-2.

  9. Facile fabrication of nanogap electrodes for suspended graphene characterization using direct ion beam patterning

    NASA Astrophysics Data System (ADS)

    Qi, Zhengqing John; Johnson, A. T. Charlie

    2014-03-01

    Graphene is a two-dimensional sheet of carbon atoms with exceptional electronic and mechanical properties, giving it tremendous potential in nanoelectromechanical system devices. Here, we present a method to easily and reproducibly fabricate suspended graphene nanoribbons across nanogap electrodes of various separation lengths, demonstrating a technique with aggressive gap scalability and device geometry control. Fabrication is based on using a focused gallium ion beam to create a slit between joined electrodes prepatterened on a 100 nm thick silicon nitride membrane. The transparency of the nitride membrane provides reduced ion backscattering and adds milling resolution. Large-area monolayer graphene grown by atmospheric pressure chemical vapor deposition was transferred onto the silicon nitride chip and patterned into a free-standing ribbon geometry via electron beam lithography on organic ebeam resist followed by an O2 plasma etch. We find that commonly used inorganic negative tone resist that requires a buffered oxide etch for resist removal will attack the adhesion layer (Cr2O3) between the electrode and nitride membrane, which is exposed immediately after milling, so an organic resist was selected to avoid this. Using this technique, we fabricate freestanding graphene devices contacted by electrodes of sub-100 nm separation length and preform a comparative study on the effects of current annealing on device resistance. The gap resolution of this technique is limited by the gallium ion beam, which allows for sub-100 nm gaps. Sub-10 nm gaps are feasible with He ion beams, proving direct applications in probing the high field transport properties of graphene nanoribbons at post-CMOS length scales.

  10. Closed cycle MHD generator with nonuniform gas-plasma flow driving recombinated plasma clots formed by high-energy electron beams

    SciTech Connect

    Danilov, V.V.; Laptev, S.S.; Slavin, V.S.

    1996-12-31

    A new concept of a closed cycle MHD generator without alkali seed has been suggested. The essence of it is the use of the high-energy electron beams technology for a nonuniform gas-plasma flow in MHD channel creation. At the inlet of MHD channel in supersonic flow of noble gas (He) the plasma clots with a density about 10{sup 15} cm{sup {minus}3} are formed by pulsed intense electron beams with energy about 100 keV. Gas flow drives these clots in a cross magnetic field along the MHD channel which has electrodes connected with a load by Faraday`s scheme. Because the nonuniform gas-plasma flow has not the conductivity in the Hall`s EMF direction a Faraday`s current can flow only through the narrow plasma layers. The energy dissipation and Joule`s heating in MHD channel support the nonequilibrium conductivity in these plasma layers. a gas flow pushes current layers and produces electric power at the expense of enthalpy extraction. The key element is a question of plasma layers stability in MHD channel. The most dangerous instability is the overheating instability. it is shown that taking into account the phenomenon of frozen conductivity for recombinated plasma which appears for noble gas at T{sub e} > 4,000 K the regime with {partial_derivative}{sigma}/{partial_derivative}T{sub e} < 0 can be realized. Due to the fulfillment of this condition the overheating instability is effectively suppressed. The numerical simulation has shown that a supersonic gas flow, containing about 4 current layers in MHD channel simultaneously, is braked without shock waves creation. Current layers provide no less than 30% enthalpy extraction and about 80% isentropic efficiency.

  11. Instability versus equilibrium propagation of a laser beam in plasma.

    PubMed

    Lushnikov, Pavel M; Rose, Harvey A

    2004-06-25

    We obtain, for the first time, an analytic theory of the forward stimulated Brillouin scattering instability of a spatially and temporally incoherent laser beam that controls the transition between statistical equilibrium and nonequilibrium (unstable) self-focusing regimes of beam propagation. The stability boundary may be used as a comprehensive guide for inertial confinement fusion designs. Well into the stable regime, an analytic expression for the angular diffusion coefficient is obtained, which provides an essential correction to a geometric optic approximation for beam propagation.

  12. Strong self-focusing of a cosh-Gaussian laser beam in collisionless magneto-plasma under plasma density ramp

    SciTech Connect

    Nanda, Vikas; Kant, Niti

    2014-07-15

    The effect of plasma density ramp on self-focusing of cosh-Gaussian laser beam considering ponderomotive nonlinearity is analyzed using WKB and paraxial approximation. It is noticed that cosh-Gaussian laser beam focused earlier than Gaussian beam. The focusing and de-focusing nature of the cosh-Gaussian laser beam with decentered parameter, intensity parameter, magnetic field, and relative density parameter has been studied and strong self-focusing is reported. It is investigated that decentered parameter “b” plays a significant role for the self-focusing of the laser beam as for b=2.12, strong self-focusing is seen. Further, it is observed that extraordinary mode is more prominent toward self-focusing rather than ordinary mode of propagation. For b=2.12, with the increase in the value of magnetic field self-focusing effect, in case of extraordinary mode, becomes very strong under plasma density ramp. Present study may be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, and x-ray lasers. Moreover, plasma density ramp plays a vital role to enhance the self-focusing effect.

  13. Near Discharge Cathode Assembly Plasma Potential Measurements in a 30-cm NSTAR Type Ion Engine During Beam Extraction

    NASA Technical Reports Server (NTRS)

    Herman, Daniel A.; Gallimore, Alec D.

    2006-01-01

    Floating emissive probe plasma potential data are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring-cusp ion thruster. Discharge plasma data are presented with beam extraction at throttling conditions comparable to the NASA TH Levels 8, 12, and 15. The operating conditions of the Extended Life Test (ELT) of the Deep Space One (DS1) flight spare ion engine, where anomalous discharge keeper erosion occurred, were TH 8 and TH 12 consequently they are of specific interest in investigating discharge keeper erosion phenomena. The data do not validate the presence of a potential hill plasma structure downstream of the DCA, which has been proposed as a possible erosion mechanism. The data are comparable in magnitude to data taken by other researchers in ring-cusp electron-bombardment ion thrusters. The plasma potential structures are insensitive to thruster throttling level with a minimum as low as 14 V measured at the DCA exit plane and increasing gradually in the axial direction. A sharp increase in plasma potential to the bulk discharge value of 26 to 28 volts, roughly 10 mm radially from DCA centerline, was observed. Plasma potential measurements indicate a low-potential plume structure that is roughly 20 mm in diameter emanating from the discharge cathode that may be attributed to a free-standing plasma double layer.

  14. New Generation of Diagnostic Beam Injectors for Large Plasma Physics Experiments

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexander A.

    1999-11-01

    During the last decades the injection of neutral beams has been widely used in magnetic fusion devices for diagnostic purposes. Modern fusion facilities are characterized by quite stringent conditions for measurements with diagnostic neutral beam injectors (DNBIs). In particular, an access to the plasma is often strongly limited, the beam penetration into the plasma core is low, the background radiation and particle outfluxes are high, especially in the presence of high power heating neutral beams. Note that the required characteristics of DNBIs differ in many respects from those of injectors for plasma heating. Generally, diagnostic beams should have a higher energy and current stability, lower angular divergence and the beam size, and a higher equivalent current density. In addition, in contrast to heating beams, modulation of a diagnostic beam with a frequency of 5-500 Hz and even higher is often required to improve the signal-to-noise ratio (see, for example, [1]). Considerable progress has been recently made at the Budker Institute in developing DNBIs which are capable of meeting the requirements of plasma diagnostics in modern fusion devices, including CHERS, Rutherford scattering, motional Stark effect, active charge-exchange, etc [2,3]. For different applications, three basic versions of DNBIs have been developed: CW injectors with a relatively low current (up to 10 mA for 60 keV energy), long pulse injectors (up to 10 s, 50 keV) with a moderate current (1-2 eq. A for hydrogen) and short pulse ones (milliseconds range) with a higher current (up to 20A). The plasma emitter in the injectors is created either by the RF discharge or by an arc discharge. In many cases, the beam focusing is needed to increase the current density in the plasma. In the developed DNBIs, it is provided by spherically formed grids of the ion optical system. The paper describes the developed DNBIs and reviews experimental results on the measurements of plasma parameters at different

  15. Plasma control and diagnostics for 10 GeV electron beams on BELLA

    NASA Astrophysics Data System (ADS)

    Daniels, J.; Gonsalves, A. J.; Pieronek, C. V.; Benedetti, C.; van Tilborg, J.; Schroeder, C. B.; Leemans, W. P.

    2017-03-01

    To advance the current state-of-the-art of capillary-based laser plasma accelerators (LPAs), the tunability of capillary discharge plasma channels needs to be improved. We present the techniques used to determine critical properties of the plasma density distribution. Independent tailoring of plasma channel width and on-axis density are required to produce higher energy electron beams with existing facilities. A scheme involving an additional, nanosecond laser pulse to locally heat the channel has been proposed previously. We discuss recent progress on the implementation of this scheme, demonstrating a heating effect on the plasma channel as evidenced from nanosecond-resolved spectroscopy on transversely emitted plasma light. PIC simulations indicate the possibility of accelerating high charge beams up to 8.4 GeV average energy if other technique advances are made as well. These include the need for longer plasma channels of 10s of centimeters, low plasma density and an ionization injection scheme to inject more charge into the wake at the start of the channel. Finally, a brief overview is given of the status of these techniques working towards the goal of producing 10 GeV beams with a single accelerator module.

  16. Ribbon electron beam formation by a forevacuum plasma electron source

    SciTech Connect

    Klimov, A. S. Burdovitsin, V. A.; Grishkov, A. A.; Oks, E. M.; Zenin, A. A.; Yushkov, Yu. G.

    2016-01-15

    Results of the numerical analysis and experimental research on ribbon electron beam generation based on hollow cathode discharge at forevacuum gas pressure are presented. Geometry of the accelerating gap has modified. It lets us focus the ribbon electron beam and to transport it on a distance of several tens of centimeters in the absence of an axial magnetic field. The results of numerical simulations are confirmed by the experiment.

  17. Generation of high quality electron beams via ionization injection in a plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Vafaei-Najafabadi, Navid; Joshi, Chan; E217 SLAC Collaboration

    2016-10-01

    Ionization injection in a beam driven plasma wakefield accelerator has been used to generate electron beams with over 30 GeV of energy in a 130 cm of lithium plasma. The experiments were performed using the 3 nC, 20.35 GeV electron beam at the FACET facility of the SLAC National Accelerator Laboratory as the driver of the wakefield. The ionization of helium atoms in the up ramp of a lithium plasma were injected into the wake and over the length of acceleration maintained an emittance on the order of 30 mm-mrad, which was an order of magnitude smaller than the drive beam, albeit with an energy spread of 10-20%. The process of ionization injection occurs due to an increase in the electric field of the drive beam as it pinches through its betatron oscillations. Thus, this energy spread is attributed to the injection region encompassing multiple betatron oscillations. In this poster, we will present evidence through OSIRIS simulations of producing an injected beam with percent level energy spread and low emittance by designing the plasma parameters appropriately, such that the ionization injection occurs over a very limited distance of one betatron cycle. Work at UCLA was supported by the NSF Grant Number PHY-1415386 and DOE Grant Number DE-SC0010064. Work at SLAC was supported by DOE contract number DE-AC02-76SF00515. Simulations used the Hoffman cluster at UCLA.

  18. Ion beam and plasma jet based methods in ultra-precision optics manufacturing

    NASA Astrophysics Data System (ADS)

    Arnold, Th.; Boehm, G.; Paetzelt, H.; Pietag, F.

    2015-01-01

    Ion beam and plasma jet based techniques can be used in alternative machining processes for generating and finishing of ultra-precision optical surfaces. Since atomistic mechanisms are responsible for surface material modification, etching, and deposition, very high accuracy on the atomic level can be achieved. Various advanced techniques like pulse-width modulated ion beam figuring, sub-aperture reactive ion beam etching, or ion beam assisted structuring, planarization and smoothing technologies have been investigated aiming at precision on sub-nanometer height scale and lateral scales ranging over the full spatial wavelength range from nanometers to meters. Additionally, different atmospheric reactive plasma jet processes and plasma jet assisted process chains for generating, correction and smoothing of complex shaped optical surfaces like aspheres with large departures to best fit sphere or free forms exhibiting strong gradients have been developed in the last decade. In the paper an overview to the most recent trends of non-conventional ultra-precision optics processing is given and latest results of optics manufacturing are shown. Specific examples are given to demonstrate that form generation (e.g. for laser beam shaping optics) and surface finishing and polishing using atmospheric plasma jet tools are promising applications exhibiting advantages with respect to process efficiency and flexibility. Furthermore, the capabilities of ion beam surface figure correction using a new approach to control the tool function are demonstrated.

  19. Acceleration of plasma electrons by intense nonrelativistic ion and electron beams propagating in background plasma due to two-stream instability

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor D.

    2015-11-01

    In this paper we study the effects of the two-stream instability on the propagation of intense nonrelativistic ion and electron beams in background plasma. Development of the two-stream instability between the beam ions and plasma electrons leads to beam breakup, a slowing down of the beam particles, acceleration of the plasma particles, and transfer of the beam energy to the plasma particles and wave excitations. Making use of the particle-in-cell codes EDIPIC and LSP, and analytic theory we have simulated the effects of the two-stream instability on beam propagation over a wide range of beam and plasma parameters. Because of the two-stream instability the plasma electrons can be accelerated to velocities as high as twice the beam velocity. The resulting return current of the accelerated electrons may completely change the structure of the beam self - magnetic field, thereby changing its effect on the beam from focusing to defocusing. Therefore, previous theories of beam self-electromagnetic fields that did not take into account the effects of the two-stream instability must be significantly modified. This effect can be observed on the National Drift Compression Experiment-II (NDCX-II) facility by measuring the spot size of the extracted beamlet propagating through several meters of plasma. Particle-in-cell, fluid simulations, and analytical theory also reveal the rich complexity of beam- plasma interaction phenomena: intermittency and multiple regimes of the two-stream instability in dc discharges; band structure of the growth rate of the two-stream instability of an electron beam propagating in a bounded plasma and repeated acceleration of electrons in a finite system. In collaboration with E. Tokluoglu, D. Sydorenko, E. A. Startsev, J. Carlsson, and R. C. Davidson. Research supported by the U.S. Department of Energy.

  20. Stimulated Raman scattering of laser in a plasma in the presence of a co-propagating electron beam

    SciTech Connect

    Parashar, J.

    2013-12-15

    A relativistic electron beam co-propagating with a high power laser in plasma is shown to add to the growth of the stimulated Raman back scattering of the laser. The growth rate is sensitive to phase matching of electron beam with the plasma wave. In the case of phase mismatch, the growth rate drops by an order. The energy spread of the electron beam significantly reduces the effectiveness of the beam on the stimulated Raman process.

  1. Wavelength Detuning Cross-Beam Energy Transfer Mitigation for Polar Direct Drive and Symmetric Direct Drive

    NASA Astrophysics Data System (ADS)

    Marozas, J. A.; Collins, T. J. B.; McKenty, P. W.; Radha, P. B.; Hohenberger, M.; Rosenberg, M. J.

    2016-10-01

    Cross-beam energy transfer (CBET) results from two-beam energy exchange via stimulated Brillouin scattering, which reduces absorbed light and implosion velocity, alters time-resolved scattered-light spectra, and redistributes absorbed and scattered light. These effects reduce target performance in polar direct drive (PDD) and symmetric direct drive (SDD) at the National Ignition Facility (NIF) and on the OMEGA Laser System. The CBET package (Adaawam) incorporated into the 2-D hydrodynamics code DRACO is an integral part of the 3-D ray-trace package (Mazinisin). Detuning the initial laser wavelength (dλ0) reduces the CBET interaction volume, which can be combined with other mitigation domains (e.g., spatial and temporal). Recent PDD experiments on the NIF explored this option using a cone-swapping technique with dλ0 = +/- 2.34 Å UV, which are compared with DRACO simulations. DRACO simulations of wavelength detuning in SDD on OMEGA predict the expected mitigation using OMEGA's three main amplifier chains in both near-term dλ0 = { - 3 , 0 , + 3 } -Å and long-term dλ0 = { - 6 , 0 , + 6 } -Å UV configurations. The detuning simulations predict improved performance and changes in 2-D and 3-D morphology in both PDD and SDD. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  2. Direct synthesis of hydrogen peroxide from plasma-water interactions

    NASA Astrophysics Data System (ADS)

    Liu, Jiandi; He, Bangbang; Chen, Qiang; Li, Junshuai; Xiong, Qing; Yue, Guanghui; Zhang, Xianhui; Yang, Size; Liu, Hai; Liu, Qing Huo

    2016-12-01

    Hydrogen peroxide (H2O2) is usually considered to be an important reagent in green chemistry since water is the only by-product in H2O2 involved oxidation reactions. Early studies show that direct synthesis of H2O2 by plasma-water interactions is possible, while the factors affecting the H2O2 production in this method remain unclear. Herein, we present a study on the H2O2 synthesis by atmospheric pressure plasma-water interactions. The results indicate that the most important factors for the H2O2 production are the processes taking place at the plasma-water interface, including sputtering, electric field induced hydrated ion emission, and evaporation. The H2O2 production rate reaches ~1200 μmol/h when the liquid cathode is purified water or an aqueous solution of NaCl with an initial conductivity of 10500 μS cm‑1.

  3. Direct synthesis of hydrogen peroxide from plasma-water interactions.

    PubMed

    Liu, Jiandi; He, Bangbang; Chen, Qiang; Li, Junshuai; Xiong, Qing; Yue, Guanghui; Zhang, Xianhui; Yang, Size; Liu, Hai; Liu, Qing Huo

    2016-12-05

    Hydrogen peroxide (H2O2) is usually considered to be an important reagent in green chemistry since water is the only by-product in H2O2 involved oxidation reactions. Early studies show that direct synthesis of H2O2 by plasma-water interactions is possible, while the factors affecting the H2O2 production in this method remain unclear. Herein, we present a study on the H2O2 synthesis by atmospheric pressure plasma-water interactions. The results indicate that the most important factors for the H2O2 production are the processes taking place at the plasma-water interface, including sputtering, electric field induced hydrated ion emission, and evaporation. The H2O2 production rate reaches ~1200 μmol/h when the liquid cathode is purified water or an aqueous solution of NaCl with an initial conductivity of 10500 μS cm(-1).

  4. On the beam direction search space in computerized non-coplanar beam angle optimization for IMRT—prostate SBRT

    NASA Astrophysics Data System (ADS)

    Rossi, Linda; Breedveld, Sebastiaan; Heijmen, Ben J. M.; Voet, Peter W. J.; Lanconelli, Nico; Aluwini, Shafak

    2012-09-01

    In a recent paper, we have published a new algorithm, designated ‘iCycle’, for fully automated multi-criterial optimization of beam angles and intensity profiles. In this study, we have used this algorithm to investigate the relationship between plan quality and the extent of the beam direction search space, i.e. the set of candidate beam directions that may be selected for generating an optimal plan. For a group of ten prostate cancer patients, optimal IMRT plans were made for stereotactic body radiation therapy (SBRT), mimicking high dose rate brachytherapy dosimetry. Plans were generated for five different beam direction input sets: a coplanar (CP) set and four non-coplanar (NCP) sets. For CP treatments, the search space consisted of 72 orientations (5° separations). The NCP CyberKnife (CK) space contained all directions available in the robotic CK treatment unit. The fully non-coplanar (F-NCP) set facilitated the highest possible degree of freedom in selecting optimal directions. CK+ and CK++ were subsets of F-NCP to investigate some aspects of the CK space. For each input set, plans were generated with up to 30 selected beam directions. Generated plans were clinically acceptable, according to an assessment of our clinicians. Convergence in plan quality occurred only after around 20 included beams. For individual patients, variations in PTV dose delivery between the five generated plans were minimal, as aimed for (average spread in V95: 0.4%). This allowed plan comparisons based on organ at risk (OAR) doses, with the rectum considered most important. Plans generated with the NCP search spaces had improved OAR sparing compared to the CP search space, especially for the rectum. OAR sparing was best with the F-NCP, with reductions in rectum DMean, V40Gy, V60Gy and D2% compared to CP of 25%, 35%, 37% and 8%, respectively. Reduced rectum sparing with the CK search space compared to F-NCP could be largely compensated by expanding CK with beams with relatively

  5. Terahertz radiation generation and shape control by interaction of array Gaussian laser beams with plasma

    NASA Astrophysics Data System (ADS)

    Bakhtiari, Farhad; Golmohammady, Shole; Yousefi, Masoud; Ghafary, Bijan

    2016-12-01

    In the present paper, a scheme for generation of terahertz (THz) radiation in electron-neutral collisional plasma based on beating of two Gaussian laser array beams has been proposed. It is shown that the efficiency of THz radiation based on the Gaussian laser array beams can be enhanced drastically in comparison with the efficiency of THz radiation based on the Gaussian one. Furthermore, the producing THz radiation by the Gaussian laser array beams, which has an exclusive field profile, is affected by some array structure parameters. It can also be used to overcome the negative consequences of electron neutral collisions in plasma, which may be occurring in the THz radiation generation process. Optimizing the collisional plasma, laser beams and array structure parameters, THz radiation efficiency up to 0.07% can be obtained in our scheme which is about three times greater than the maximum efficiency obtained for standard (single) Gaussian laser beam. Also, considering the electrostatic energy channel in solving the THz wave equation, and reduction of THz radiation efficiency to 0.054%, in this assumption, the ratio between the efficiency of Gaussian laser array beams and standard Gaussian laser beam remained unchanged.

  6. Nonlinear Amplification of the Whistler Wave in a Magnetized Relativistic Beam-Plasma Interaction

    NASA Astrophysics Data System (ADS)

    Taguchi, Toshihiro; Antonsen, Thomas; Mima, Kunioki

    2015-11-01

    We have been investigating a relativistic electron beam-plasma interaction under a strong magnetic field using a hybrid simulation code. In an initial stage, the electron beam drives a return current in a background plasma and such a two beam state causes a longitudinal two stream instability and a transverse Weibel instability. The application of a strong magnetic field is proposed for the suppression of the beam instabilities. When a sufficiently strong magnetic field is applied along the beam propagation, the Weibel instability is well suppressed and electrons flow laminarly. When the magnetic field strength is not large enough, however, electrons stagnate and the total number of beam electrons is largely reduced. Our detailed analyses show that a strong whistler wave is excited during the interaction and the wave stops the beam electrons. Since the whistler wave is composed of transverse electromagnetic fields, there should be a mechanism to convert the transverse field to a longitudinal one. In order to investigate this problem, we have performed a lot of simulation runs for a simple geometry. Then we found the amplified transverse modulation of the background plasma due to the Weibel instability plays an important role for the amplification of the whistler wave. This work was supported by a Grant-in-Aid for Scientific Research (B), 15H03758.

  7. Low-energy plasma focus device as an electron beam source.

    PubMed

    Khan, Muhammad Zubair; Ling, Yap Seong; Yaqoob, Ibrar; Kumar, Nitturi Naresh; Kuang, Lim Lian; San, Wong Chiow

    2014-01-01

    A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 10(16)/m(3), respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences.

  8. Compact disposal of high-energy electron beams using passive or laser-driven plasma decelerating stage

    SciTech Connect

    Bonatto, A.; Schroeder, C. B.; Vay, J. -L.; Geddes, C. R.; Benedetti, C.; Esarey and, E.; Leemans, W. P.

    2014-07-13

    A plasma decelerating stage is investigated as a compact alternative for the disposal of high-energy beams (beam dumps). This could benefit the design of laser-driven plasma accelerator (LPA) applications that require transportability and or high-repetition-rate operation regimes. Passive and laser-driven (active) plasma-based beam dumps are studied analytically and with particle-in-cell (PIC) simulations in a 1D geometry. Analytical estimates for the beam energy loss are compared to and extended by the PIC simulations, showing that with the proposed schemes a beam can be efficiently decelerated in a centimeter-scale distance.

  9. Terahertz generation by two cross focused laser beams in collisional plasmas

    SciTech Connect

    Sharma, R. P. Singh, Ram Kishor

    2014-07-15

    The role of two cross-focused spatial-Gaussian laser beams has been studied for the high power and efficient terahertz (THz) radiation generation in the collisional plasma. The nonlinear current at THz frequency arises on account of temperature dependent collision frequency of electrons with ions in the plasma and the presence of a static electric field (applied externally in the plasma) and density ripple. Optimisation of laser-plasma parameters gives the radiated THz power of the order of 0.23  MW.

  10. Achieving a long-lived high-beta plasma state by energetic beam injection.

    PubMed

    Guo, H Y; Binderbauer, M W; Tajima, T; Milroy, R D; Steinhauer, L C; Yang, X; Garate, E G; Gota, H; Korepanov, S; Necas, A; Roche, T; Smirnov, A; Trask, E

    2015-04-23

    Developing a stable plasma state with high-beta (ratio of plasma to magnetic pressures) is of critical importance for an economic magnetic fusion reactor. At the forefront of this endeavour is the field-reversed configuration. Here we demonstrate the kinetic stabilizing effect of fast ions on a disruptive magneto-hydrodynamic instability, known as a tilt mode, which poses a central obstacle to further field-reversed configuration development, by energetic beam injection. This technique, combined with the synergistic effect of active plasma boundary control, enables a fully stable ultra-high-beta (approaching 100%) plasma with a long lifetime.

  11. Supersonic molecular beam injection effects on tokamak plasma applied non-axisymmetric magnetic perturbation

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; In, Y.; Jeon, Y. M.; Lee, H. Y.; Hahn, S. H.; Lee, K. D.; Nam, Y. U.; Yoon, S. W.

    2016-08-01

    The change of tokamak plasma behavior by supersonic molecular beam injection (SMBI) was investigated by applying a three-dimensional magnetic perturbation that could suppress edge localized modes (ELMs). From the time trace of decreasing electron temperature and with increasing plasma density keeping the total confined energy constant, the SMBI seems to act as a cold pulse on the plasma. However, the ELM behaviors were changed drastically (i.e., the symptom of ELM suppression has disappeared). The plasma collisionality in the edge-pedestal region could play a role in the change of the ELM behaviors.

  12. Interference patterns in the Spacelab 2 plasma wave data - oblique electrostatic waves generated by the electron beam

    SciTech Connect

    Feng, Wei; Gurnett, D.A.; Cairns, I.H. )

    1992-11-01

    During the Spacelab 2 mission the University of Iowa's Plasma Diagnostics Package (PDP) explored the plasma environment around the shuttle. Wideband spectrograms of plasma waves were obtained from the PDP at frequencies of 0-30 kHz and at distances up to 400 m from the shuttle. Strong low-frequency (below 10 kHz) electric field noise was observed in the wideband data during two periods in which an electron beam was ejected from the shuttle. This noise shows clear evidence of interference patterns caused by the finite (3.89 m) antenna length. The low-frequency noise was the most dominant type of noise produced by the ejected electron beam. Analysis of antenna interference patterns generated by these waves permits a determination of the wavelength, the direction of propagation, and the location of the source region. The observed waves have a linear dispersion relation very similar to that of ion acoustic waves. The waves are believed to be oblique ion acoustic or high-order ion cyclotron waves generated by a current of ambient electrons returning to the shuttle in response to the ejected electron beam. 31 refs.

  13. Synergistic Direct/Wakefield Acceleration of Plasma Electrons In the Plasma Bubble Regime Using Tailored Laser Pulses

    NASA Astrophysics Data System (ADS)

    Shvets, Gennady

    2016-10-01

    The integration of direct laser acceleration (DLA) and laser wakefield acceleration (LWFA) is a new approach to plasma-based acceleration that confers several benefits over both schemes taken separately. Such integration requires a significant portion of the laser energy (e.g., a separate laser pulse) to trail the main bubble-producing laser pulse, and resonantly interact with the trapped accelerated electrons undergoing betatron motion inside the plasma bubble. I will demonstrate how electron dephasing from the accelerating wakefield, which is one of the key limitations of LWFA, is reduced by their growing undulating motion. Moreover, the distinct energy gains from wake and the laser pulse are compounding, thereby increasing the total energy gain. Even more significant increases of the overall acceleration can be obtained by moving away from single-frequency laser format toward combining mid-infrared laser pulses for plasma bubble generation with short-wavelength trailing pulses for DLA. Various injection mechanisms, such as ionization injection, external injection, self-injection, and their advantages will also be discussed. Translating these new concepts into specific experiments will take advantage of recent technological advances in synchronizing laser and electron beams, and using multiple beamlines for producing sophisticated laser pulse formats.

  14. Three dimensional analysis of longitudinal plasma oscillations in a thermal relativistic electron beam

    SciTech Connect

    Marinelli, Agostino; Hemsing, Erik; Rosenzweig, James B.

    2011-10-15

    In this paper, we develop a three-dimensional kinetic theory of longitudinal plasma oscillations in a relativistic electron beam. Our analysis includes the effects of betatron motion, finite emittance, and energy spread as well as edge effects due to the finite size of the beam. The consequences of these effects are shown to be of significant interest, as they give rise to several distinct new phenomena. These include an emittance induced anisotropy between backward and forward propagating plasma waves as well as a beatwave effect between plasma and betatron oscillations caused by the coupling of betatron motion to the transverse structure of the charge perturbation. The experimental implications of these new results and their relevance to the beam and radiation physics of advanced light sources, such as free-electron lasers, are also discussed.

  15. Ideal Laser-Beam Propagation through High-Temperature Ignition Hohlraum Plasmas

    SciTech Connect

    Froula, D. H.; Divol, L.; Meezan, N. B.; Dixit, S.; Moody, J. D.; Neumayer, P.; Pollock, B. B.; Ross, J. S.; Glenzer, S. H.

    2007-02-23

    We demonstrate that a blue (3{omega}, 351 nm) laser beam with an intensity of 2x10{sup 15} W cm{sup -2} propagates nearly within the original beam cone through a millimeter scale, T{sub e}=3.5 keV high density (n{sub e}=5x10{sup 20} cm{sup -3}) plasma. The beam produced less than 1% total backscatter at these high temperatures and densities; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds.

  16. Ideal laser-beam propagation through high-temperature ignition Hohlraum plasmas.

    PubMed

    Froula, D H; Divol, L; Meezan, N B; Dixit, S; Moody, J D; Neumayer, P; Pollock, B B; Ross, J S; Glenzer, S H

    2007-02-23

    We demonstrate that a blue (3omega, 351 nm) laser beam with an intensity of 2 x 10(15) W cm(-2) propagates nearly within the original beam cone through a millimeter scale, T(e)=3.5 keV high density (n(e)=5 x 10(20) cm(-3)) plasma. The beam produced less than 1% total backscatter at these high temperatures and densities; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds.

  17. Efficient numerical modelling of the emittance evolution of beams with finite energy spread in plasma wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Mehrling, T. J.; Robson, R. E.; Erbe, J.-H.; Osterhoff, J.

    2016-09-01

    This paper introduces a semi-analytic numerical approach (SANA) for the rapid computation of the transverse emittance of beams with finite energy spread in plasma wakefield accelerators in the blowout regime. The SANA method is used to model the beam emittance evolution when injected into and extracted from realistic plasma profiles. Results are compared to particle-in-cell simulations, establishing the accuracy and efficiency of the procedure. In addition, it is demonstrated that the tapering of vacuum-to-plasma and plasma-to-vacuum transitions is a viable method for the mitigation of emittance growth of beams during their injection and extraction from and into plasma cells.

  18. Plasma focus ion beam fluence and flux—For various gases

    SciTech Connect

    Lee, S.; Saw, S. H.

    2013-06-15

    A recent paper derived benchmarks for deuteron beam fluence and flux in a plasma focus (PF) [S. Lee and S. H. Saw, Phys. Plasmas 19, 112703 (2012)]. In the present work we start from first principles, derive the flux equation of the ion beam of any gas; link to the Lee Model code and hence compute the ion beam properties of the PF. The results show that, for a given PF, the fluence, flux, ion number and ion current decrease from the lightest to the heaviest gas except for trend-breaking higher values for Ar fluence and flux. The energy fluence, energy flux, power flow, and damage factors are relatively constant from H{sub 2} to N{sub 2} but increase for Ne, Ar, Kr and Xe due to radiative cooling and collapse effects. This paper provides much needed benchmark reference values and scaling trends for ion beams of a PF operated in any gas.

  19. Up- and downstream sheaths in an ion-beam-plasma system

    SciTech Connect

    Wei, Zi-an; Ma, J. X.

    2016-02-15

    Ion sheaths formed in the up- and downstream sides of a negatively biased metal plate/mesh in an ion-beam-background-plasma system were experimentally investigated in a double plasma device. Measured potential profiles near the plate exhibit asymmetric structure, showing thicker sheath in the downstream side. The presence of the ion beam causes the shrink of the sheaths on both sides. The sheath thickness decreases with the increase of beam energy and density. Furthermore, the sheaths near the mesh are substantially thinner than that near the plate because of the partial transmission of the mesh to the ions. In addition, the increase of neutral gas pressure leads to the reduction of the beam energy and density, resulting in the increase of the sheath thickness.

  20. Plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Guzeeva, Tatiana

    2017-01-01

    This paper presents the results of the experimental investigation of plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam (TEA-500 pulsed electron accelerator) with the following characteristics: 400-450 keV electron energy, 60 ns pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. Experiments were conducted on the effect of the pulsed electron beam on SF6 and on mixtures of SF6 with O2, Ar, or N2. For the mixture of SF6 and oxygen, the results indicated chemical reactions involving the formation of a number of products of which one is sulphur, confirming the Wray - Fluorescence Analysis. The plasma chemical conversion of SF6 initiated by the pulsed electron beam was not detected when SF6 was mixed with Ar or N2, suggesting a possible mechanism for the reaction of SF6 in the presence of O2.

  1. Extraction characteristics of a low-energy ion beam system with a remote plasma chamber

    SciTech Connect

    Vasquez, M. R.; Wada, M.

    2016-02-15

    Low-energy argon beams were extracted from a dual-chamber ion source system. The first chamber is a quartz cylinder where dense inductively coupled plasmas were produced using 13.56 MHz radio frequency (rf) power. The discharge was driven into an adjacent chamber which acts as a reservoir for ion beam extraction using a dual-electrode extractor configuration. Extraction of ions from the second chamber with energies in the 100 eV range was achieved while minimizing fluctuations induced by the rf signal. A custom-built retarding potential analyzer was used to analyze the effectiveness of ion beam transport using the remote plasma chamber. Well-defined beams were extracted between 60 and 100 V extraction potentials at 50–100 W rf powers. An increase in rf power resulted in an increase in average ion energy, increase in ion current density while the energy spread remains constant.

  2. Betatron radiation based diagnostics for plasma wakefield accelerated electron beams at the SPARC_LAB test facility

    NASA Astrophysics Data System (ADS)

    Shpakov, V.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Dabagov, S.; Ferrario, M.; Filippi, F.; Marocchino, A.; Paroli, B.; Pompili, R.; Rossi, A. R.; Zigler, A.

    2016-09-01

    Recent progress with wake-field acceleration has shown a great potential in providing high gradient acceleration fields, while the quality of the beams remains relatively poor. Precise knowledge of the beam size at the exit from the plasma and matching conditions for the externally injected beams are the key for improvement of beam quality. Betatron radiation emitted by the beam during acceleration in the plasma is a powerful tool for the transverse beam size measurement, being also non-intercepting. In this work we report on the technical solutions chosen at SPARC_LAB for such diagnostics tool, along with expected parameters of betatron radiation.

  3. Direct-write deposition and focused-electron-beam-induced purification of gold nanostructures.

    PubMed

    Belić, Domagoj; Shawrav, Mostafa M; Gavagnin, Marco; Stöger-Pollach, Michael; Wanzenboeck, Heinz D; Bertagnolli, Emmerich

    2015-02-04

    Three-dimensional gold (Au) nanostructures offer promise in nanoplasmonics, biomedical applications, electrochemical sensing and as contacts for carbon-based electronics. Direct-write techniques such as focused-electron-beam-induced deposition (FEBID) can provide such precisely patterned nanostructures. Unfortunately, FEBID Au traditionally suffers from a high nonmetallic content and cannot meet the purity requirements for these applications. Here we report exceptionally pure pristine FEBID Au nanostructures comprising submicrometer-large monocrystalline Au sections. On the basis of high-resolution transmission electron microscopy results and Monte Carlo simulations of electron trajectories in the deposited nanostructures, we propose a curing mechanism that elucidates the observed phenomena. The in situ focused-electron-beam-induced curing mechanism was supported by postdeposition ex situ curing and, in combination with oxygen plasma cleaning, is utilized as a straightforward purification method for planar FEBID structures. This work paves the way for the application of FEBID Au nanostructures in a new generation of biosensors and plasmonic nanodevices.

  4. Development of a radio-frequency ion beam source for fast-ion studies on the large plasma device.

    PubMed

    Tripathi, S K P; Pribyl, P; Gekelman, W

    2011-09-01

    A helium ion beam source (23 kV/2.0 A) has been constructed for studying fast-ion physics in the cylindrical magnetized plasma of the large plasma device (LAPD). An inductive RF source produces a 10(19) m(-3) density plasma in a ceramic dome. A multi-aperture, rectangular (8 cm × 8 cm) three-grid system extracts the ion beam from the RF plasma. The ion beam is injected at a variety of pitch angles with Alfvénic speeds in the LAPD. The beam current is intense enough to excite magnetic perturbations in the ambient plasma. Measurements of the ion beam profile were made to achieve an optimum beam performance and a reliable source operation was demonstrated on the LAPD.

  5. The effect of beam directivity on the inspection of anisotropic materials using ultrasonic arrays

    NASA Astrophysics Data System (ADS)

    Lane, C. J. L.; Wilcox, P. D.

    2012-05-01

    The beam directivity from an ultrasonic transducer in isotropic materials is well documented. However, beam directivities in elastically anisotropic materials and their effect on ultrasonic NDE inspection has been investigated far less extensively. In this paper, analytical and numerical finite element models are developed to predict the beam directivity in a single crystal nickel-based superalloy. This material is highly anisotropic and is used widely in the gas-turbine industry. The developed models are used to investigate the effect of the crystallographic orientation on the beam directivity. In turn, the effect of beam directivity on defect detection sensitivity and characterization capability using an ultrasonic array is demonstrated. It is shown that the effect is particularly important for the accurate sizing of small defects.

  6. Control of quasi-monoenergetic electron beams from laser-plasma accelerators

    NASA Astrophysics Data System (ADS)

    Tsai, H.-E.; Swanson, K. K.; Barber, S. K.; Mao, H.-S.; Lehe, R.; Steinke, S.; van Tilborg, J.; Geddes, C. G. R.; Leemans, W. P.

    2017-03-01

    In this paper, we demonstrate a highly tunable, controlled-injection laser-plasma accelerator (LPA) through systematically varying parameters of a density shock injector. Beam energy, energy spread, charge and pointing can be controlled in the range of 50-300 MeV, with <10% energy spread, 1.5 mrad divergence and <1 mrad pointing fluctuation. The beams are repeatable, and suitable for high quality MeV Thomson photon sources or for injectors to staged systems.

  7. Terahertz generation by relativistic ponderomotive focusing of two co-axial Gaussian laser beams propagating in ripple density plasma

    SciTech Connect

    Kumar, Subodh; Singh, Ram Kishor Sharma, R. P.

    2015-10-15

    Terahertz (THz) generation by beating of two co-axial Gaussian laser beams, propagating in ripple density plasma, has been studied when both ponderomotive and relativistic nonlinearities are operative. When the two lasers co-propagate in rippled density plasma, electrons acquire a nonlinear velocity at beat frequency in the direction transverse to the direction of propagation. This nonlinear oscillatory velocity couples with the density ripple to generate a nonlinear current, which in turn generates THz radiation at the difference frequency. The necessary phase matching condition is provided by the density ripple. Relativistic ponderomotive focusing of the two lasers and its effects on yield of the generated THz amplitude have been discussed. Numerical results show that conversion efficiency of the order of 10{sup −3} can be achieved in the terahertz radiation generation with relativistic ponderomotive focusing.

  8. Terahertz generation by relativistic ponderomotive focusing of two co-axial Gaussian laser beams propagating in ripple density plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Subodh; Singh, Ram Kishor; Sharma, R. P.

    2015-10-01

    Terahertz (THz) generation by beating of two co-axial Gaussian laser beams, propagating in ripple density plasma, has been studied when both ponderomotive and relativistic nonlinearities are operative. When the two lasers co-propagate in rippled density plasma, electrons acquire a nonlinear velocity at beat frequency in the direction transverse to the direction of propagation. This nonlinear oscillatory velocity couples with the density ripple to generate a nonlinear current, which in turn generates THz radiation at the difference frequency. The necessary phase matching condition is provided by the density ripple. Relativistic ponderomotive focusing of the two lasers and its effects on yield of the generated THz amplitude have been discussed. Numerical results show that conversion efficiency of the order of 10-3 can be achieved in the terahertz radiation generation with relativistic ponderomotive focusing.

  9. Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

    SciTech Connect

    Purohit, Gunjan Rawat, Priyanka; Chauhan, Prashant; Mahmoud, Saleh T.

    2015-05-15

    This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled laser beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate.

  10. Three-dimensional imaging of the ultracold plasma formed in a supersonic molecular beam

    NASA Astrophysics Data System (ADS)

    Schulz-Weiling, Markus; Grant, Edward

    2015-06-01

    Double-resonant excitation of nitric oxide in a seeded supersonic molecular beam forms a state-selected Rydberg gas that evolves to form an ultracold plasma. This plasma travels with the propagation of the molecular beam in z over a variable distance as great as 600 mm to strike an imaging detector, which records the charge distribution in the dimensions, x and y. The ω1 + ω2 laser crossed molecular beam excitation geometry convolutes the axial Gaussian distribution of NO in the molecular beam with the Gaussian intensity distribution of the perpendicularly aligned laser beam to create an ellipsoidal volume of Rydberg gas. Detected images describe the evolution of this initial density as a function of selected Rydberg gas initial principal quantum number, n0, ω1 laser pulse energy (linearly related to Rydberg gas density, ρ0) and flight time. Low-density Rydberg gases of lower principal quantum number produce uniformly expanding, ellipsoidal charge-density distributions. Increase either of n0 or ρ0 breaks the ellipsoidal symmetry of plasma expansion. The volume bifurcates to form repelling plasma volumes. The velocity of separation depends on n0 and ρ0 in a way that scales uniformly with ρe, the density of electrons formed in the core of the Rydberg gas by prompt Penning ionization. Conditions under which this electron gas drives expansion in the long axis dimension of the ellipsoid favours the formation of counter-propagating shock waves.

  11. Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

    PubMed

    Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

    2008-02-01

    We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

  12. Laser beam smoothing and backscatter saturation processes in plasmas relevant to National Ignition Facility hohlraums

    SciTech Connect

    Berger, R L; Cohen, B I; Decker, C D; Dixit, S; Glenzer, S H; Hinkel, D E; Kirkwood, R K; Langdon, A B; Lefebvre, E; MacGowan, B J; Moody, J D; Rothenberg, J E; Rousseuax, C; Still, C H; Suter, L J; Williams, E A

    1998-10-01

    We have used gas-filled targets irradiated at the Nova laser to simulate National Ignition Facility (NlF) hohlraum plasmas and to study the dependence of Stimulated Raman (SRS) and Brillouin (SBS) Scattering on beam smoothing at a range of laser intensities (3{omega}, 2 - 4 10{sup 15}Wcm{sup -2}) and plasma conditions. We have demonstrated the effectiveness of polarization smoothing as a potential upgrade to the NIF. Experiments with higher intensities and higher densities characteristic of 350eV hohlraum designs indicate that with appropriate beam smoothing the backscatter from such hohlraums may be tolerable.

  13. Modeling nitrogen plasmas produced by intense electron beams

    NASA Astrophysics Data System (ADS)

    Angus, J. R.; Mosher, D.; Swanekamp, S. B.; Ottinger, P. F.; Schumer, J. W.; Hinshelwood, D. D.

    2016-05-01

    A new gas-chemistry model is presented to treat the breakdown of a nitrogen gas with pressures on the order of 1 Torr from intense electron beams with current densities on the order of 10 kA/cm2 and pulse durations on the order of 100 ns. For these parameter regimes, the gas transitions from a weakly ionized molecular state to a strongly ionized atomic state on the time scale of the beam pulse. The model is coupled to a 0D-circuit model using the rigid-beam approximation that can be driven by specifying the time and spatial profiles of the beam pulse. Simulation results are in good agreement with experimental measurements of the line-integrated electron density from experiments done using the Gamble II generator at the Naval Research Laboratory. It is found that the species are mostly in the ground and metastable states during the atomic phase, but that ionization proceeds predominantly through thermal ionization of optically allowed states with excitation energies close to the ionization limit.

  14. Propagation of a laser beam in a time-varying waveguide. [plasma heating for controlled fusion

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.

    1978-01-01

    The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is reported. For the case of an axially uniform waveguide it is found that the basic characteristics of alternating focusing and defocusing beams are maintained. However, the intensity distribution is changed at the foci and outer-beam regions. The features of paraxial beam propagation are discussed with reference to axially varying waveguides. Laser plasma coupling is considered noting the case where laser heating produces a density distribution radially parabolic near the axis and the energy absorbed over the focal length of the plasma is small. It is found that: (1) beam-propagation stability is governed by the relative magnitude of the density fluctuations existing in the axial variation of the waveguides due to laser heating, and (2) for beam propagation in a time-varying waveguide, the global instability of the propagation is a function of the initial fluctuation growth rate as compared to the initial time rate of change in the radial curvature of the waveguide.

  15. Electromagnetic-wave excitation in a large laboratory beam-plasma system

    NASA Technical Reports Server (NTRS)

    Whelan, D. A.; Stenzel, R. L.

    1981-01-01

    The mechanism by which unstable electrostatic waves of a beam-plasma system are converted into observed electromagnetic waves is of current interest in space physics and in tokamak fusion research. The process involved in the conversion of electrostatic to electromagnetic waves at the critical layer is well understood. However, the radiation from uniform plasmas cannot be explained on the basis of this process. In connection with certain difficulties, it has not yet been possible to establish the involved emission processes by means of experimental observations. In the considered investigation these difficulties are overcome by employing a large laboratory plasma in a parameter range suitable for detailed diagnostics. A finite-diameter electron beam is injected into a uniform quiescent afterglow plasma of dimensions large compared with electromagnetic wavelengths. The considered generation mechanism concerning the electromagnetic waves is conclusively confirmed by observing the temporal evolution of an instability

  16. Current Control in ITER Steady State Plasmas With Neutral Beam Steering

    SciTech Connect

    R.V. Budny

    2009-09-10

    Predictions of quasi steady state DT plasmas in ITER are generated using the PTRANSP code. The plasma temperatures, densities, boundary shape, and total current (9 - 10 MA) anticipated for ITER steady state plasmas are specified. Current drive by negative ion neutral beam injection, lower-hybrid, and electron cyclotron resonance are calculated. Four modes of operation with different combinations of current drive are studied. For each mode, scans with the NNBI aimed at differing heights in the plasma are performed to study effects of current control on the q profile. The timeevolution of the currents and q are calculated to evaluate long duration transients. Quasi steady state, strongly reversed q profiles are predicted for some beam injection angles if the current drive and bootstrap currents are sufficiently large.

  17. Ground-Based Tests of Spacecraft Polymeric Materials under OXY-GEN Plasma-Beam

    NASA Astrophysics Data System (ADS)

    Chernik, Vladimir; Novikov, Lev; Gaidar, Anna

    2016-07-01

    Spacecraft LEO mission is accompanied by destruction of polymeric material surface under influence of atomic oxygen flow. Sources of molecular, plasma and ion beams are used for the accelerated ground-based tests of spacecraft materials. In the work application of oxygen plasma accelerator of a duoplasmatron type is described. Plasma particles have been accelerated up to average speed of 13-16 km/s. Influence of such beam on materials leads to more intensive destruction of polymers than in LEO. This fact allows to execute tests in the accelerated time scale by a method of an effective fluence. Special measures were given to decrease a concentration of both gaseous and electrode material impurities in the oxygen beam. In the work the results of simulative tests of spacecraft materials and experiments on LEO are considered. Comparison of plasma beam simulation with LEO data has shown conformity for structures of a number of polymeric materials. The relative erosion yields (normalized with respect to polyimide) of the tested materials are shown practically equal to those in LEO. The obtained results give grounds for using the plasma-generation mode with ion energies of 20-30 eV to accelerated testing of spacecraft materials for long -term LEO missions.

  18. Non-Maxwellian effects in underdense plasmas heated by non-uniform laser beams

    NASA Astrophysics Data System (ADS)

    Matte, Jean-Pierre

    2005-10-01

    The collisionl heating of plasmas by intense laser beams is known to drive the electron distribution function into a super-Gaussian [1] or ``DLM'' [2] shape. This reduces the absorption [1], and the reduction is stronger if the beam is very non-uniform, for a given average intensity, as there is a depletion of slow electrons, compared to a Maxwellian of the same density and average energy. If the beam irradiates most or a good fraction of the plasma volume, these non-Maxwellian effects also imply a depletion of high energy electrons, with the resulting strong reduction of Landau damping of Langmuir waves [2], contrary to the results of Brunner and Valeo [3] which were obtained in the limit of a narrow beam heating a wide plasma. The depletion of fast electrons depends essentially on the average laser intensity. We will show how these two aspects vary with the laser and plasma parameters.[1] A.B. Langdon, Phys. Rev. Lett. 44, 575 (1980) [2] B.B. Afeyan, A.E. Chou, J.P. Matte et al., Phys. Rev. Lett. 80, 2322 (1998). [3] S. Brunner and E. Valeo, Phys. Plasmas 9, 923 (2002).

  19. Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Kausik, S. S.; Kakati, B.; Saikia, B. K.

    2013-05-01

    The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (˜pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

  20. Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

    SciTech Connect

    Kausik, S. S.; Kakati, B.; Saikia, B. K.

    2013-05-15

    The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10{sup −4} millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

  1. Electron temperature measurement in Maxwellian non-isothermal beam plasma of an ion thruster

    SciTech Connect

    Zhang, Zun; Tang, Haibin Kong, Mengdi; Zhang, Zhe; Ren, Junxue

    2015-02-15

    Published electron temperature profiles of the beam plasma from ion thrusters reveal many divergences both in magnitude and radial variation. In order to know exactly the radial distributions of electron temperature and understand the beam plasma characteristics, we applied five different experimental approaches to measure the spatial profiles of electron temperature and compared the agreement and disagreement of the electron temperature profiles obtained from these techniques. Experimental results show that the triple Langmuir probe and adiabatic poly-tropic law methods could provide more accurate space-resolved electron temperature of the beam plasma than other techniques. Radial electron temperature profiles indicate that the electrons in the beam plasma are non-isothermal, which is supported by a radial decrease (∼2 eV) of electron temperature as the plume plasma expands outward. Therefore, the adiabatic “poly-tropic law” is more appropriate than the isothermal “barometric law” to be used in electron temperature calculations. Moreover, the calculation results show that the electron temperature profiles derived from the “poly-tropic law” are in better agreement with the experimental data when the specific heat ratio (γ) lies in the range of 1.2-1.4 instead of 5/3.

  2. A Wave-Based Model for Cross-Beam Energy Transfer in Direct-Drive Inertial Confinement Fusion Implosions

    NASA Astrophysics Data System (ADS)

    Myatt, J. F.

    2016-10-01

    Cross-beam energy transfer (CBET) is thought to be responsible for an 30 % reduction in hydrodynamic coupling efficiency on OMEGA and up to 50% at the ignition scale for direct-drive (DD) implosions. These numbers are determined by ray-based models that have been developed and integrated within the radiation-hydrodynamics codes LILAC (1-D) and DRACO (2-D). However, ray-based modeling of CBET in an inhomogeneous plasma assumes a steady-state plasma response, does not include the effects of beam speckle, and ray caustics are treated in an ad hoc manner. Nevertheless, simulation results are in good qualitative agreement with implosion experiments on OMEGA (when combined with a model for nonlocal heat transport). The validity of the modeling for ignition-scale implosions has not yet been determined. To address the physics shortcomings, which have important implications for DD inertial confinement fusion, a new wave-based model has been constructed. It solves the time-enveloped Maxwell equations in three-dimensions, including polarization effects, plasma inhomogeneity, and open-boundary conditions with the ability to prescribe beams incident at arbitrary angles. Beams can be made realistic with respect to laser speckle, polarization smoothing, and laser bandwidth. This, coupled to a linearized low-frequency plasma response that does not assume a steady state, represents the most-complete model of CBET to date. New results will be presented and the implications for CBET modeling and mitigation will be described. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DENA0001944, in collaboration with J. G. Shaw, R. K. Follett, and D. H. Edgell (LLE).

  3. Linear accelerator design study with direct plasma injection scheme for warm dense matter

    SciTech Connect

    Kondo, K.; Kanesue, T; Okamura, M.

    2011-03-28

    Warm Dense Matter (WDM) is a challenging science field, which is related to heavy ion inertial fusion and planetary science. It is difficult to expect the behavior because the state with high density and low temperature is completely different from ideal condition. The well-defined WDM generation is required to understand it. Moderate energy ion beams ({approx} MeV/u) slightly above Bragg peak is an advantageous method for WDM because of the uniform energy deposition. Direct Plasma Injection Scheme (DPIS) with a Interdigital H-mode (IH) accelerator has a potential for the beam parameter. We show feasible parameters of the IH accelerator for WDM. WDM physics is a challenging science and is strongly related to Heavy Ion Fusion science. WDM formation by Direct Plasma Injection Scheme (DPIS) with IH accelerator, which is a compact system, is proposed. Feasible parameters for IH accelerator are shown for WDM state. These represents that DPIS with IH accelerator can access a different parameter region of WDM.

  4. Plasma density from Cerenkov radiation, betatron oscillations, and beam steering in a plasma wakefield experiment at 30 GeV

    SciTech Connect

    Catravas, P.; Chattopadhyay, S.; Esarey, E.; Leemans, W.P.; Assmann, R.; Decker, F.-J.; Hogan, M.J.; Iverson, R.; Siemann, R.H.; Walz, D.; Whittum, D.; Blue, B.; Clayton, C.; Joshi, C.; Marsh, K.; Mori, W.B.; Wang, S.; Katsouleas, T.; Lee, S.; Muggli, P.

    2001-01-01

    A method for using Cerenkov radiation near atomic spectral lines to measure plasma source properties for plasma wakefield applications has been discussed and experimentally verified. Because the radiation co-propagates with the electron beam, the radiation samples the source properties exactly along the path of interest with perfect temporal synchronization. Observation wavelengths were chosen with respect to the atomic resonances of the plasma source, where the relative change in the index of refraction strongly affects the Cerenkov cone angle, and permits flexible diagnostic design. The Cerenkov spatial profiles were systematically studied for a Lithium heat pipe oven as a function of oven temperature and observation wavelength. Neutral densities and plasma densities were extracted from the measurements.

  5. Nature and location of the source of plasma sheet boundary layer ion beams

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Onsager, T. G.; Thomsen, M. F.; Gosling, J. T.

    1995-01-01

    Onsager et al. (1991) have put forward a model of the formation of the plasma sheet boundary layer (PSBL) which relies on a steady source of plasma from a spatially extended plasma sheet, together with steady equatorward and earthward ExB convection of field lines due to reconnection at a downtail neutral line. This model is a synthesis of earlier proposals and it explains such features as an electron layer exterior to the ion boundary layer, ion velocity dispersion, counter streaming beams, low-speed cutoffs in the beams. It also explains the apparent evolution of the ion beams through 'kidney bean' shaped velocity-space distributions toward quasi-isotropic shells without invoking pitch angle scattering or energy diffusion. In this paper we explore two ramifications of the model. In principle we can map, as a function of time, the downtail neutral line distance and establish whether or not it is retreating during substorm recovery. We can also reconstruct the plasma distribution function near the neutral line to see if it is most consistent with mantle or plasma sheet plasma. We perform this analysis using International Sun Earth Explorer (ISEE) Fast Plasma Experiment (FPE) data for two plasma sheet recovery events, one on March 1, 1978, and the other on April 18, 1978. On March 1, 1978, we find evidence for an initial retreat from around 110 to 160 R(sub E) in the first 15 min; little further retreat occurs thereafter. On April 18, 1978, the neutral line location ranges from as little as 40 R(sub E) tailward of the satellite to as much as 200 R(sub E), but there is no evidence for a systematic retreat. The reconstructed ion distributions for these events are most consistent with a plasma sheet origin for the March 1 case and possibly plasma mantle or low-latitude boundary layer for the April 18 case.

  6. Toggling between single and multi-beam effects on Stimulated Raman Scattering in a NIF hohlraum plasma

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; Strozzi, D. J.; Divol, L.; Michel, P.; Ralph, J.; Berger, R. L.; Kirkwood, R. K.; Robey, H.; Landen, O. L.; Lepape, S.; Ross, S.; MacGowan, B. J.; Williams, E. A.; Glenzer, S. H.; Nikroo, A.

    2012-10-01

    We have developed a method for studying single and multi-beam laser-plasma interactions (LPI) in a NIF hohlraum plasma. This method utilizes toggling combinations of beams on and off during the time of high (partly saturated) stimulated Raman backscattering (SRS) and measuring the effects on the SRS. We find that during the high-intensity part of the laser pulse SRS saturates at about 10 - 20% reflectivity for single and multi-beam interactions. In addition, we can place limits on the cross-beam energy transfer and show that re-amplification is small due to multiple beam effects. Spectral measurements indicate that toggling beams creates a <=10% change in the plasma temperature. These results are important for developing models of multi-beam intereactions. We will describe the backscatter measurements and simple models used to constrain the multi-beam effects.

  7. Automated detection and analysis of particle beams in laser-plasma accelerator simulations

    SciTech Connect

    Ushizima, Daniela Mayumi; Geddes, C.G.; Cormier-Michel, E.; Bethel, E. Wes; Jacobsen, J.; Prabhat, ,; R.ubel, O.; Weber, G,; Hamann, B.

    2010-05-21

    Numerical simulations of laser-plasma wakefield (particle) accelerators model the acceleration of electrons trapped in plasma oscillations (wakes) left behind when an intense laser pulse propagates through the plasma. The goal of these simulations is to better understand the process involved in plasma wake generation and how electrons are trapped and accelerated by the wake. Understanding of such accelerators, and their development, offer high accelerating gradients, potentially reducing size and cost of new accelerators. One operating regime of interest is where a trapped subset of electrons loads the wake and forms an isolated group of accelerated particles with low spread in momentum and position, desirable characteristics for many applications. The electrons trapped in the wake may be accelerated to high energies, the plasma gradient in the wake reaching up to a gigaelectronvolt per centimeter. High-energy electron accelerators power intense X-ray radiation to terahertz sources, and are used in many applications including medical radiotherapy and imaging. To extract information from the simulation about the quality of the beam, a typical approach is to examine plots of the entire dataset, visually determining the adequate parameters necessary to select a subset of particles, which is then further analyzed. This procedure requires laborious examination of massive data sets over many time steps using several plots, a routine that is unfeasible for large data collections. Demand for automated analysis is growing along with the volume and size of simulations. Current 2D LWFA simulation datasets are typically between 1GB and 100GB in size, but simulations in 3D are of the order of TBs. The increase in the number of datasets and dataset sizes leads to a need for automatic routines to recognize particle patterns as particle bunches (beam of electrons) for subsequent analysis. Because of the growth in dataset size, the application of machine learning techniques for

  8. Direct patterning of vortex generators on a fiber tip using a focused ion beam.

    PubMed

    Vayalamkuzhi, Pramitha; Bhattacharya, Shanti; Eigenthaler, Ulrike; Keskinbora, Kahraman; Samlan, C T; Hirscher, Michael; Spatz, Joachim P; Viswanathan, Nirmal K

    2016-05-15

    The realization of spiral phase optical elements on the cleaved end of an optical fiber by focused ion beam milling is presented. A focused Ga+ ion beam with an acceleration voltage of 30 keV is used to etch continuous spiral phase plates and fork gratings directly on the tip of the fiber. The phase characteristics of the output beam generated by the fabricated structures measured via an interference experiment confirmed the presence of phase singularity in the output beam. The devices are expected to be promising candidates for all-fiber beam shaping and optical trapping applications.

  9. Summary Report of Working Group 5: Electron Beam Driven Plasma Accelerators

    SciTech Connect

    Hogan, Mark J.; Conde, Manoel E.

    2009-01-22

    Electron beam driven plasma accelerators have seen rapid progress over the last decade. Recent efforts have built on this success by constructing a concept for a plasma wakefield accelerator based linear collider. The needs for any future collider to deliver both energy and luminosity have substantial implications for interpreting current experiments and setting priorities for the future. This working group reviewed current experiments and ideas in the context of the demands of a future collider. The many discussions and presentations are summarized here.

  10. Simulative research on the expansion of cathode plasma in high-current electron beam diode

    SciTech Connect

    Xu Qifu; Liu Lie

    2012-09-15

    The expansion of cathode plasma has long been recognized as a limiting factor in the impedance lifetime of high-current electron beam diode. Realistic modeling of such plasma is of great necessity in order to discuss the dynamics of cathode plasma. Using the method of particle-in-cell, the expansion of cathode plasma is simulated in this paper by a scaled-down diode model. It is found that the formation of cathode plasma increases the current density in the diode. This consequently leads to the decrease of the potential at plasma front. Once the current density has been increased to a certain value, the potential at plasma front would then be equal to or lower than the plasma potential. Then the ions would move towards the anode, and the expansion of cathode plasma is thereby formed. Different factors affecting the plasma expansion velocity are discussed in this paper. It is shown that the decrease of proton genatation rate has the benefit of reducing the plasma expansion velocity.

  11. Non-linear Dynamics in ETG Mode Saturation and Beam-Plasma Instabilities

    NASA Astrophysics Data System (ADS)

    Tokluoglu, Erinc K.

    Non-linear mechanisms arise frequently in plasmas and beam-plasma systems resulting in dynamics not predicted by linear theory. The non-linear mechanisms can influence the time evolution of plasma instabilities and can be used to describe their saturation. Furthermore time and space averaged non-linear fields generated by instabilities can lead to collisionless transport and plasma heating. In the case of beam-plasma systems counter-intuitive beam defocusing and scaling behavior which are interesting areas of study for both Low-Temperature and High Energy Density physics. The non-linear mode interactions in form of phase coupling can describe energy transfer to other modes and can be used to describe the saturation of plasma instabilities. In the first part of this thesis, a theoretical model was formulated to explain the saturation mechanism of Slab Electron Temperature Gradient (ETG) mode observed in the Columbia Linear Machine (CLM), based on experimental time-series data collected through probe diagnostics [1]. ETG modes are considered to be a major player in the unexplained high levels of electron transport observed in tokamak fusion experiments and the saturation mechanism of these modes is still an active area of investigation. The data in the frequency space indicated phase coupling between 3 modes, through a higher order spectral correlation coefficient known as bicoherence. The resulting model is similar to [2], which was a treatment for ITG modes observed in the CLM and correctly predicts the observed saturation level of the ETG turbulence. The scenario is further supported by the fact that the observed mode frequencies are in close alignment with those predicted theoretical dispersion relations. Non-linear effects arise frequently in beam-plasma systems and can be important for both low temperature plasma devices commonly used for material processing as well as High Energy Density applications relevant to inertial fusion. The non-linear time averaged

  12. Effect of collisions on amplification of laser beams by Brillouin scattering in plasmas

    SciTech Connect

    Humphrey, K. A.; Speirs, D. C.; Trines, R. M. G. M.; Norreys, P.; Fiuza, F.; Cairns, R. A.; Silva, L. O.

    2013-10-15

    We report on particle in cell simulations of energy transfer between a laser pump beam and a counter-propagating seed beam using the Brillouin scattering process in uniform plasma including collisions. The results presented show that the ion acoustic waves excited through naturally occurring Brillouin scattering of the pump field are preferentially damped without affecting the driven Brillouin scattering process resulting from the beating of the pump and seed fields together. We find that collisions, including the effects of Landau damping, allow for a more efficient transfer of energy between the laser beams, and a significant reduction in the amount of seed pre-pulse produced.

  13. System for transporting an electron beam to the atmosphere for a gun with a plasma emitter

    NASA Astrophysics Data System (ADS)

    Kornilov, S. Yu.; Rempe, N. G.; Shidlovskiy, S. V.

    2016-06-01

    We report on the results of simulation of the gas flow in a gun with a plasma emitter and in the system for extracting the electron beam to the atmosphere, constructed on the basis of standard gasdynamic windows (GDWs). The design of the gun and GDWs is described. Calculations are performed for a pressure of about 10-3 Torr in the electron beam generation range. It is shown that the pressure drop to the atmospheric pressure in the system of electron beam extraction to the atmosphere can be ensured by two GDW stages evacuated by pumps with optimal performance.

  14. Propagation of microwave beams through the stagnation zone in an inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Tereshchenko, M. A.

    2017-01-01

    A study is made of the microwave beam evolution due to passing through the stagnation zone, where the group velocity vanishes, thus making the paraxial approximation for the wavefield inappropriate. An extension to the standard beam tracing technique is suggested that allows one to calculate the microwave beam parameters on either branch of its path apart from the stagnation zone, omitting the calculation of the wavefield inside it. Application examples of the extended technique are presented for the case of microwave reflection from the upper hybrid resonance layer in a tokamak plasma.

  15. Reduction of stimulated Brillouin backscattering with plasma beam smoothing

    SciTech Connect

    Yahia, V.; Loisel, G.; Baccou, C.; Labaune, C.; Masson-Laborde, P.-E.; Depierreux, S.; Goyon, C.; Teychenné, D.; Borisenko, N. G.; Orekhov, A.; Rienecker, T.; Rosmej, O.

    2015-04-15

    Plasma induced incoherence (PII) can strongly modify the growth rates of stimulated scattering instabilities. A special double-target design was used to quantify the effect of PII on stimulated Brillouin scattering (SBS). Successive shots using all or part of these targets led to the characterization of temporal and spatial incoherence of a laser pulse after propagation through a foam plasma and to the quantification of the reduction of SBS from the second target. Numerical simulations were used to identify the main physical mechanisms in play.

  16. Formation and sustainment of field reversed configuration (FRC) plasmas by spheromak merging and neutral beam injection

    SciTech Connect

    Yamada, Masaaki

    2016-01-01

    This study briefly reviews a compact toroid reactor concept that addresses critical issues for forming, stabilizing and sustaining a field reversed configuration (FRC) with the use of plasma merging, plasma shaping, conducting shells, neutral beam injection (NBI). In this concept, an FRC plasma is generated by the merging of counter-helicity spheromaks produced by inductive discharges and sustained by the use of neutral beam injection (NBI). Plasma shaping, conducting shells, and the NBI would provide stabilization to global MHD modes. Although a specific FRC reactor design is outside the scope of the present paper, an example of a promising FRC reactor program is summarized based on the previously developed SPIRIT (Self-organized Plasmas by Induction, Reconnection and Injection Techniques) concept in order to connect this concept to the recently achieved the High Performance FRC plasmas obtained by Tri Alpha Energy [Binderbauer et al, Phys. Plasmas 22,056110, (2015)]. This paper includes a brief summary of the previous concept paper by M. Yamada et al, Plasma Fusion Res. 2, 004 (2007) and the recent experimental results from MRX.

  17. Formation and sustainment of field reversed configuration (FRC) plasmas by spheromak merging and neutral beam injection

    DOE PAGES

    Yamada, Masaaki

    2016-01-01

    This study briefly reviews a compact toroid reactor concept that addresses critical issues for forming, stabilizing and sustaining a field reversed configuration (FRC) with the use of plasma merging, plasma shaping, conducting shells, neutral beam injection (NBI). In this concept, an FRC plasma is generated by the merging of counter-helicity spheromaks produced by inductive discharges and sustained by the use of neutral beam injection (NBI). Plasma shaping, conducting shells, and the NBI would provide stabilization to global MHD modes. Although a specific FRC reactor design is outside the scope of the present paper, an example of a promising FRC reactormore » program is summarized based on the previously developed SPIRIT (Self-organized Plasmas by Induction, Reconnection and Injection Techniques) concept in order to connect this concept to the recently achieved the High Performance FRC plasmas obtained by Tri Alpha Energy [Binderbauer et al, Phys. Plasmas 22,056110, (2015)]. This paper includes a brief summary of the previous concept paper by M. Yamada et al, Plasma Fusion Res. 2, 004 (2007) and the recent experimental results from MRX.« less

  18. Formation and sustainment of field reversed configuration (FRC) plasmas by spheromak merging and neutral beam injection

    NASA Astrophysics Data System (ADS)

    Yamada, Masaaki

    2016-03-01

    This paper briefly reviews a compact toroid reactor concept that addresses critical issues for forming, stabilizing and sustaining a field reversed configuration (FRC) with the use of plasma merging, plasma shaping, conducting shells, neutral beam injection (NBI). In this concept, an FRC plasma is generated by the merging of counter-helicity spheromaks produced by inductive discharges and sustained by the use of neutral beam injection (NBI). Plasma shaping, conducting shells, and the NBI would provide stabilization to global MHD modes. Although a specific FRC reactor design is outside the scope of the present paper, an example of a promising FRC reactor program is summarized based on the previously developed SPIRIT (Self-organized Plasmas by Induction, Reconnection and Injection Techniques) concept in order to connect this concept to the recently achieved the High Performance FRC plasmas obtained by Tri Alpha Energy [Binderbauer et al, Phys. Plasmas 22,056110, (2015)]. This paper includes a brief summary of the previous concept paper by M. Yamada et al, Plasma Fusion Res. 2, 004 (2007) and the recent experimental results from MRX.

  19. Direct temperature monitoring for semiconductors in plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    Tian, Xiubo; Chu, Paul K.

    2000-07-01

    In situ temperature monitoring is extremely important in plasma immersion ion implantation (PIII) of semiconductors. For instance, the silicon wafer must be heated to 600 °C or higher in separation by plasma implantation of oxygen, and in the PIII/ion-cut process, the wafer temperature must remain below 300 °C throughout the experiment. In this article, we present a thermocouple-based direct temperature measurement system for planar samples such as silicon wafers. In order to ensure reliable high-voltage operation and overall electrical isolation, the thermocouple assembly and wires are integrated into the sample chuck and feedthrough. Hydrogen plasma immersion ion implantation is performed in silicon to demonstrate the effectiveness and reliability of the device. Our experimental results indicate that instrumental parameters such as implantation voltage, pulse duration, and pulsing frequency affect the sample temperature to a different extent. The measured temperature rise is higher than that predicted by a theoretical model based on the Child-Langmuir law. The discrepancy is attributed to the finite-sample size and the nonplanar, conformal plasma sheath.

  20. Compact beam transport system for free-electron lasers driven by a laser plasma accelerator

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Zhang, Tong; Wang, Dong; Huang, Zhirong

    2017-02-01

    Utilizing laser-driven plasma accelerators (LPAs) as a high-quality electron beam source is a promising approach to significantly downsize the x-ray free-electron laser (XFEL) facility. A multi-GeV LPA beam can be generated in several-centimeter acceleration distance, with a high peak current and a low transverse emittance, which will considerably benefit a compact FEL design. However, the large initial angular divergence and energy spread make it challenging to transport the beam and realize FEL radiation. In this paper, a novel design of beam transport system is proposed to maintain the superior features of the LPA beam and a transverse gradient undulator (TGU) is also adopted as an effective energy spread compensator to generate high-brilliance FEL radiation. Theoretical analysis and numerical simulations are presented based on a demonstration experiment with an electron energy of 380 MeV and a radiation wavelength of 30 nm.