Showing papers in "Journal of Plasma Physics in 2012"
TL;DR: In this article, the authors explore a new parameter space of the two-beam acceleration (TBA) scheme based on an ultra-short (~20 ns) rf pulse in a dielectric TBA.
Abstract: Abstract We are exploring a new parameter space of the two-beam acceleration (TBA) scheme based on an ultra-short (~20 ns) rf pulse in a dielectric TBA. All two-beam accelerators (TBAs) use an electron drive beam to generate high-power rf in a decelerator and extract this power to drive an accelerating structure to high gradient. Typically, the rf pulse is on the order of hundreds of ns or greater in order to maintain good rf-to-beam efficiency. However, recent scaling arguments show that the rf breakdown threshold improves with decreasing rf pulse length, so it desirable to find a way to run at short-pulse length with good efficiency. In this paper, we discuss how we chose the design parameters of a short-pulse TBA for a TeV linear collider module. We then present plans for an experimental program to demonstrate TBA at Argonne wakefield accelerator (AWA) facility including high-power rf generation, high-gradient acceleration, and staging.
37 citations
TL;DR: In this article, a numerical scheme has been provided to find the value of the Mach number at which double layer solution exists, and also the amplitude of that double layer, and a finite jump between the amplitudes of negative potential solitary waves at M = MD − ϵ1 and M =MD + ϵ2 has been observed, where 0 0.
Abstract: Dust ion-acoustic solitary structures have been investigated in an unmagnetized non-thermal plasma consisting of negatively charged dust grains, adiabatic positive ions, and non-thermal electrons. Whenever the non-thermal parameter exceeds a critical value, the present system supports negative potential double layer solution. However, this double layer solution is unable to restrict the occurrence of negative potential solitary waves of the present system. As a result, the occurrence of one type of negative potential solitary wave is restricted by Mc MD, where Mc is the lower bound of the Mach number M and MD (> Mc) is the Mach number corresponding to a negative potential double layer. A finite jump between the amplitudes of negative potential solitary waves at M = MD − ϵ1 and M = MD + ϵ2 has been observed, where 0 0. Depending on the analytical theory presented in this paper, a numerical scheme has been provided to find the value of the Mach number at which double layer solution exists, and also the amplitude of that double layer. Although the occurrence of coexistence of solitary structures of both polarities is restricted by Mc Mmax, where Mmax is the upper bound of M for the existence of positive potential solitary waves only. Qualitatively different compositional parameter spaces showing the nature of existing solitary structures of the energy integral have been found. These solution spaces are capable of producing new results and physical ideas for the formation of solitary structures whenever one can move the solution spaces through the family of curves parallel to the curve M = Mc.
36 citations
TL;DR: In this paper, two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined: the Cartesian code vorpal (Nieter, C. et al. 2004 VORPAL) and reduced-geometry codes.
Abstract: Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100-terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined. First, the Cartesian code vorpal (Nieter, C. and Cary, J. R. 2004 VORPAL: a versatile plasma simulation code. J. Comput. Phys. 196, 538) using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while keeping the usage of computational resources modest. The second way to reduce the simulation load is using reduced-geometry codes. In our case, the quasi-cylindrical code calder-circ (Lifschitz, A. F. et al. 2009 Particle-in-cell modelling of laser-plasma interaction using Fourier decomposition. J. Comput. Phys. 228(5), 1803-1814) uses decomposition of fields and currents into a set of poloidal modes, while the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the interaction allows using just two modes, reducing the computational load to roughly that of a planar Cartesian simulation while preserving the 3D nature of the interaction. This significant economy of resources allows using fine resolution in the direction of propagation and a small time step, making numerical dispersion vanishingly small, together with a large number of particles per cell, enabling good particle statistics. Quantitative agreement of two simulations indicates that these are free of numerical artefacts. Both approaches thus retrieve the physically correct evolution of the plasma bubble, recovering the intrinsic connection of electron self-injection to the nonlinear optical evolution of the driver.
29 citations
TL;DR: In this paper, the Weibel instability in counterpropagating electron-ion plasmas with the focus on the ion contribution was investigated, considering a realistic mass ratio, and a generalized dis- persion relation was defined.
Abstract: We investigate the Weibel instability in counterpropagating electron-ion plasmas with the focus on the ion contribution, considering a realistic mass ratio. A generalized dis- persion relation is d ...
26 citations
TL;DR: In this article, a unified model of electron penetration into linear plasma wakefields is formulated and studied, and the optimum angle for side injection of electrons is found, at smaller angles, all electrons are reflected radially.
Abstract: A unified model of electron penetration into linear plasma wakefields is formulated and studied. The optimum angle for side injection of electrons is found. At smaller angles, all electrons are reflected radially. At larger angles, electrons enter the wakefield with superfluous transverse momentum that is unfavorable for trapping. Separation of incident electrons into penetrated and reflected fractions occurs in the outer region of the wakefield at some ‘reflection’ radius that depends on electron energy.
24 citations
TL;DR: In this paper, the influence of the magnetic field on the propagation of dust-lattice waves is studied and the envelope evolution equation for longitudinal modes in the presence of a weak magnetic field, which is in the form of the Gross-Pitaevskii equation.
Abstract: The propagation of dust-lattice waves in two-dimensional hexagonal dusty plasma crystals in the presence of an external weak magnetic field is considered. Linear and nonlinear properties of the longitudinal dust-lattice waves are investigated. Dispersion relation, group velocity and evolution equation are found. The influence of the magnetic field on the propagation of dust-lattice waves is studied. We obtain the envelope evolution equation for longitudinal modes in the presence of a weak magnetic field, which is in the form of the Gross–Pitaevskii equation.
23 citations
TL;DR: In this article, the nonlinear propagation characteristics of Gardner solitons in a non-planar (cylindrical and spherical) two-ion-temperature unmagnetized dusty plasma, whose constituents are inertial negative dust, Boltzmann electrons and ions with two distinctive temperatures, are investigated by deriving the modified Gardner (mG) equation.
Abstract: The nonlinear propagation characteristics of Gardner solitons (GSs) in a non-planar (cylindrical and spherical) two-ion-temperature unmagnetized dusty plasma, whose constituents are inertial negative dust, Boltzmann electrons and ions with two distinctive temperatures, are investigated by deriving the modified Gardner (mG) equation. The standard reductive perturbation method is employed to derive the mG equation. The basic features of non-planar dust-acoustic (DA) GSs are analyzed. It has been found that the basic characteristics of GSs, which are shown to exist for the values of ni10/Zdnd0 around 0.311, for ni20/Zdnd0 = 0.5, Ti1/Te = 0.07, and Ti1/Ti2 = 0.05 [where ni10 (ni20) is the lower (higher) temperature ion number density at equilibrium, Ti1 (Ti2) is the lower (higher) temperature of ions, Te is the electron temperature, Zd is the number of electrons residing on the dust grain surface, and nd0 is the equilibrium dust number density] are different from those of Korteweg-de Vries solitons, which do not exist around ni10/Zdnd0 ≃ 0.311. It has been found that the propagation characteristics of non-planar DA GSs significantly differ from those of planar ones.
23 citations
TL;DR: In this paper, the proton bunch-driven plasma wakefield acceleration (PWFA) has been proposed as an approach to accelerate an electron beam to the TeV energy regime in a single plasma section.
Abstract: The proton bunch-driven plasma wakefield acceleration (PWFA) has been proposed as an approach to accelerate an electron beam to the TeV energy regime in a single plasma section. An experimental program has been recently proposed to demonstrate the capability of proton-driven PWFA by using existing proton beams from the European Organization for Nuclear Research (CERN) accelerator complex. At present, a spare Super Proton Synchrotron (SPS) tunnel, having a length of 600 m, could be used for this purpose. The layout of the experiment is introduced. Particle-in-cell simulation results based on realistic SPS beam parameters are presented. Simulations show that working in a self-modulation regime, the wakefield driven by an SPS beam can accelerate an externally injected ~10 MeV electrons to ~2 GeV in a 10-m plasma, with a plasma density of 7 × 10 14 cm −3 .
23 citations
TL;DR: In this paper, quasilinear development of anisotropy-driven electromagnetic instabilities is computed on the basis of recently formulated empirical wave dispersion relation and compared against exact numerical calculation based upon transcendental plasma dispersion function and exact numerical roots.
Abstract: In the present paper, quasilinear development of anisotropy-driven electromagnetic instabilities is computed on the basis of recently formulated empirical wave dispersion relation and compared against exact numerical calculation based upon transcendental plasma dispersion function and exact numerical roots. Upon comparison with the exact method it is demonstrated that the empirical model provides reasonable results. The present findings may be relevant to space physical application, as the present paper provides a useful short-cut research method for self-consistent analysis of temporal development of anisotropy-driven instabilities.
19 citations
TL;DR: In this paper, the authors give a definitive account of a physical situation of current practical interest by examining the plasma solution for a plasma in coaxial geometry with an applied axial magnetic field.
Abstract: This paper is concerned to give a definitive account of a physical situation of current practical interest by examining the plasma solution for a plasma in coaxial geometry with an applied axial magnetic field. It builds on earlier work concerned with plasma diamagnetism and concentrates on the parameters involved at low pressures and low collisionalities but can be extended to situations where the ions are magnetized.
19 citations
TL;DR: In this article, a homogeneous system of unmagnetized collisionless plasma consisting of a cold electron fluid, low-temperature ion obeying Boltzmann-type distribution and high-totemperature ion with non-thermal distribution is considered.
Abstract: In this paper, a homogeneous system of unmagnetized collisionless plasma consisting of a cold electron fluid, low-temperature ion obeying Boltzmann-type distribution and high-temperature ion obeying non-thermal distribution is considered. The perturbation method with two different forms of stretching will be considered to drive the KdV and modified KdV (mKdV) equations. The Agrawal's method is applied to formulate the time-fractional KdV and mKdV equations. A variational iteration method is used to solve these equations. The results show that the fractional order of the differential equations can be used to modify the shape of the solitary pulse instead of adding higher order dissipation terms to the equations. This study may be useful to construct the compressive and rarefactive electrostatic potential pulses associated with the broadband electrostatic noise type emissions.
TL;DR: In this article, a super-Gaussian laser wakefield accelerator (LWFA) with a weak focusing force is considered to seek improved beam quality in LWFA, and the behavior of the electron beam dynamics and synchrotron radiation arising from the transverse betatron oscillations through analysis and computation is studied.
Abstract: A laser wakefield accelerator (LWFA) with a weak focusing force is considered to seek improved beam quality in LWFA. We employ super-Gaussian laser pulses to generate the wakefield and study the behavior of the electron beam dynamics and synchrotron radiation arising from the transverse betatron oscillations through analysis and computation. We note that the super-Gaussian wakefields radically reduce the betatron oscillations and make the electron orbits mainly ballistic over a single stage. This feature permits to obtain small emittance and thus high luminosity, while still benefitting from the low-density operation of LWFA (Nakajima et al. 2011 Phys. Rev. ST Accel. Beams14, 091301), such as the reduced radiation loss, less number of stages, less beam instabilities, and less required wall plug power than in higher density regimes.
TL;DR: In this paper, the authors used 2 1/2D OSIRIS simulations to study the injection process of a laser-driven wakefield into a gas mixture of helium and nitrogen with gas density of each rising linearly from 0 to a peak.
Abstract: Ionization-induced injection into a laser-driven wakefield is studied using 2 1/2D OSIRIS simulations. A laser propagates into a gas mixture of 99.5% helium and 0.5% nitrogen with gas density of each rising linearly from 0 to a peak, after which these remain constant. Simulations show that the process can be controlled by varying the scale length of an up-ramp, the laser intensity, and the maximum plasma density. The injection process is controlled by the bubble radius decreasing as laser propagates up the density gradient and laser self-focusing in the flat-top region. A beam with a central energy of 350 MeV and an energy spread (FWHM) of 1.62% was obtained for an up-ramp length of 135 mu m, a normalized vector potential of 2, and a density of 7 x 10(18) cm(-3) (assuming a 0.8 mu m wavelength laser).
TL;DR: In this paper, it was shown that electrons and ions are attached to and absorbed by mesospheric dust particles at vastly different rates under PMSE conditions and that differences to earlier modeling might be so significant as to warrant further investigation.
Abstract: Numerical investigations of the Polar Mesosphere Summer Echoes (PMSE) Overshoot Effect have to date been undertaken under the premise of plasma neutrality and current equilibrium at any time. We find it necessary to revisit the calculations without these restrictions, since electrons and ions are attached to and absorbed by mesospheric dust particles at vastly different rates under PMSE conditions. We find that differences to earlier modeling might be so significant as to warrant further investigation. Furthermore, we conduct comprehensive studies of the PMSE Overshoot Effect and put the results in the context of experimental realities.
Journal Article•
TL;DR: In this article, the dispersion properties of the EM waves and stability criteria for such a degenerate plasma are significantly modified by the effects of the ultra-relativistic degenerate electron pressure, strong co-relation among extremely dense ion fluid, and the direction of the electromagnetic wave propagation relative to the ambient magnetic field direction.
Abstract: Abstract The linear propagation of the low-frequency (compared to the electron gyrofrequency) electromagnetic (EM) waves in a self-gravitating, strongly coupled magnetized plasma with ultra-relativistic degenerate electron fluid is investigated. It is found that the dispersion properties of the EM waves and stability criteria for such a degenerate plasma are significantly modified by the effects of the ultra-relativistic degenerate electron pressure, strong co-relation among extremely dense ion fluid, and the direction of the EM wave propagation relative to the ambient magnetic field direction. The relevance of our investigation to stability of white dwarf stars is briefly discussed. It is particularly seen here that the cores of such stars are stable for the class of gravito-electrodynamic waves that are analyzed for the characteristic ranges of relevant physical parameters.
TL;DR: In this article, a linear dispersion relation for electrostatic waves in a magnetized four-component, two-temperature electron-positron plasma was derived for the model and analyzed for different wave modes.
Abstract: Linear electrostatic waves in a magnetized four-component, two-temperature electron–positron plasma are investigated, with the hot species having the Boltzmann density distribution and the dynamics of cooler species governed by fluid equations with finite temperatures. A linear dispersion relation for electrostatic waves is derived for the model and analyzed for different wave modes. Analysis of the dispersion relation for perpendicular wave propagation yields a cyclotron mode with contributions from both cooler and hot species, which in the absence of hot species goes over to the upper hybrid mode of cooler species. For parallel propagation, both electron-acoustic and electron plasma modes are obtained, whereas for a single-temperature electron–positron plasma, only electron plasma mode can exist. Dispersion characteristics of these modes at different propagation angles are studied numerically.
TL;DR: In this article, the authors present design considerations for the use of laser-plasma accelerators for mimicking space radiation and testing space-grade electronics, taking advantage of the inherent ability of LPA accelerators to produce particle beams with exponential energy distribution, which is a characteristic shared with the hazardous relativistic electron flux present in the radiation belts of planets such as Earth, Saturn and Jupiter.
Abstract: We present design considerations for the use of laser-plasma accelerators for mimicking space radiation and testing space-grade electronics. This novel application takes advantage of the inherent ability of laser-plasma accelerators to produce particle beams with exponential energy distribution, which is a characteristic shared with the hazardous relativistic electron flux present in the radiation belts of planets such as Earth, Saturn and Jupiter. Fundamental issues regarding laser-plasma interaction parameters, beam propagation, flux development, and experimental setup are discussed.
TL;DR: In this paper, the authors examined more closely whether near-instantaneous diffusion is a valid assumption for these particular frequencies and showed that the earlier less complex and analytically more accessible model can still be considered sufficient for most, if not all, existing experimental data.
Abstract: Recent numerical studies of the Polar Mesosphere Summer Echo (PMSE) Overshoot Effect predict the basic shape of the Overshoot Characteristic Curve (OCC) to undergo dramatic changes as the frequency of the radar decreases Principally, this may render earlier modeling, which assumed near-instantaneous diffusion of electrons and ions, moot and exacerbate algebraic analysis of OCC obtained in the future with, eg the MORRO-radar (56 MHz) and a synchronized radio wave emitter, both at or near the European Incoherent Scatter (EISCAT) Scientific Association's site in Ramfjordmoen near Tromso, Norway Since, however, by far the most observational results on the PMSE Overshoot Effect have been assembled with the help of the Very High Frequency (VHF, 224 MHz) radar and the an Ultra High Frequency (UHF, 929 MHz) radar, both at the EISCAT site, we examine more closely whether near-instantaneous diffusion is a valid assumption for these particular frequencies We show that, indeed, the earlier less complex and analytically more accessible model can still be considered sufficient for most, if not all, existing experimental data
TL;DR: In this paper, the terahertz (THz) frequency radiation produced as a result of nonlinear interaction of high intense laser beam with low-density ripple in collisionless mag-netoplasma has been studied under the paraxial ray approximation.
Abstract: The terahertz (THz) frequency radiation produced as a result of nonlinear interaction of high intense laser beam with low-density ripple in collisionless mag- netoplasma has been studied under the paraxial ray approximation. The relativistic change of electron mass leads to self-focusing of laser beam when the initial power of laser beam is greater than its critical power. The self-focused laser beam couples with the pre-existing density ripple to produce a nonlinear current driving the THz radiation at different frequency. The applied magnetic field enhances the nonlinear coupling efficiency. Appropriate expressions for the beam width parameter of the laser beam and the electric vector of the THz wave have been evaluated. Theory and numerical simulations show that this THz source is capable of providing power of Giga watt level.
TL;DR: In this paper, a self-injected, collimated (8 mrad divergence), 600 pC bunch of electrons with energies up to 350 MeV from a petawatt laser-driven plasma accelerator in a plasma of electron density ne = 1017 cm−3, an order of magnitude lower than previous selfinjected laser-plasma accelerators.
Abstract: We report production of a self-injected, collimated (8 mrad divergence), 600 pC bunch of electrons with energies up to 350 MeV from a petawatt laser-driven plasma accelerator in a plasma of electron density ne = 1017 cm−3, an order of magnitude lower than previous self-injected laser-plasma accelerators. The energy of the focused drive laser pulse (150 J, 150 fs) was distributed over several hot spots. Simulations show that these hot spots remained independent over a 5 cm interaction length, and produced weakly nonlinear plasma wakes without bubble formation capable of accelerating pre-heated (~1 MeV) plasma electrons up to the observed energies. The required pre-heating is attributed tentatively to pre-pulse interactions with the plasma.
TL;DR: In this paper, the authors studied the DIA SWs in an unmagnetized dusty plasma containing non-thermal electrons, cold mobile positive ions, and stationary arbitrarily (positively and negatively) charged static dust.
Abstract: The dust-ion-acoustic solitary waves (DIA SWs) in an unmagnetized dusty plasma containing non-thermal electrons, cold mobile positive ions, and stationary arbitrarily (positively and negatively) charged static dust have been theoretically studied. The reductive perturbation technique has been employed to derive the Korteweg-de Vries equation, which admits SW solutions under certain conditions. It has been also shown that the basic features (amplitude, width, speed, etc.) of DIA SWs are significantly modified by the polarity of dust and non-thermal electrons. The implications of our results in space and laboratory dusty plasma situations are briefly discussed.
TL;DR: In this paper, it was observed that a strong interaction of plasma flow and field leads to a non-force-free relaxed magnetic field configuration governed by the triple curl Beltrami (TCB) equation.
Abstract: A possibility of relaxation of relativistically hot electron and positron (e − p) plasma with a small fraction of hot or cold ions has been investigated analytically. It is observed that a strong interaction of plasma flow and field leads to a non-force-free relaxed magnetic field configuration governed by the triple curl Beltrami (TCB) equation. The triple curl Beltrami (TCB) field composed of three different Beltrami fields gives rise to three multiscale relaxed structures. The results may have the strong relevance to some astrophysical and laboratory plasmas.
TL;DR: In this paper, the theory of electromagnetic surface waves propagating along the azimuthal direction in cylindrical metal waveguides, which are filled with current-carrying plasmas, is devoted to the theory.
Abstract: Abstract The paper is devoted to the theory of electromagnetic surface waves propagating along the azimuthal direction in cylindrical metal waveguides, which are filled with current-carrying plasmas. The problem is solved by the method of successive approximation. Adequacy of this method application is proved here. To study the coupling of ordinary (O-) and extraordinary (X-) azimuthal modes, the linear theory of the eigenazimuthal X- and O-modes is applied as zero approximation. Plasma particles are described in the framework of magneto-hydrodynamics, electromagnetic fields of the coupled azimuthal modes are determined from Maxwell equations. Spatial distribution of electromagnetic field of these coupled modes and their damping caused for different reasons are studied. Possibility to observe experimentally the phenomena, which accompany propagation of these coupled modes, is estimated numerically. Branches of their possible utilization are discussed as well.
TL;DR: In this paper, an experimental study where energetic ions were produced in an underdense 2.5 × 10 19 cm −3 plasma created by a 50 fs Ti:Sapphire laser with 5 TWs of power is presented.
Abstract: In this work we present an experimental study where energetic ions were produced in an underdense 2.5 × 10 19 cm −3 plasma created by a 50 fs Ti:Sapphire laser with 5 TWs of power. The plasma comprises 95% He and 5% N 2 gases. Ionization-induced trapping of nitrogen K-shell electrons in the laser-induced wakefield generates an electron beam with a mean energy of 40 MeV and ~1 nC of charge. Some of the helium ions at the wake–vacuum interface are accelerated with a measured minimum ion energy of He 1+ ions of 1.2 MeV and He 2+ ions of 4 MeV. The physics of the interaction is studied with 2D particle-in-cell simulations. These reveal the formation of an ion filament on the axis of the plasma due to space charge attraction of the wakefield-accelerated high-charge electron bunch. Some of these high-energy electrons escape the plasma to form a sheath at the plasma–vacuum boundary that accelerates some of the ions in the filament in the forward direction. Electrons with energy less than the sheath potential cannot escape and return to the plasma boundary in a vortex-like motion. This in turn produces a time-varying azimuthal magnetic field, which generates a longitudinal electric field at the interface that further accelerates and collimates the ions.
TL;DR: In this article, the effect of laser beam filamentation on the localization of electron plasma wave and stimulated Raman scattering (SRS) in unmagnetized plasma when relativistic and ponderomotive nonlinearities are operative is presented.
Abstract: This paper presents the effect of laser beam filamentation on the local- ization of electron plasma wave (EPW) and stimulated Raman scattering (SRS) in unmagnetized plasma when relativistic and ponderomotive nonlinearities are operative. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. The semi-analytical solution of the nonlinearly coupled EPW equation in the presence of laser beam filaments has been found. It is observed that due to this nonlinear coupling between these two waves, localization of EPW takes place. Stimulated Raman scattering of this EPW is studied and back reflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. The new enhanced damping of the plasma wave has been calculated and it is found that the SRS process gets suppressed due to the localization of plasma wave in laser beam filamentary structures.
TL;DR: In this paper, the generation of 1-5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density has been studied by 2D particle-in-cell simulations.
Abstract: The generation of 1–5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma with a symmetric, linearly ramped density distribution occurs via formation of sheath of the hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence, net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. Forward directed ion beams from a debris free gaseous target can find an application as a high-brightness ion source-injector to a conventional accelerator operating up to kHz pulse repetition frequency.
TL;DR: In this paper, the authors used particle-in-cell simulations with the code QuickPIC to demonstrate that a laser pulse can remain focused in a plasma channel for hundreds of Rayleigh lengths and efficiently accelerate a high-quality electron beam to 100GeV (25GeV) in a single stage with average gradient 3.6GV/m (7.2GV)
Abstract: Optimization of laser wakefield acceleration involves understanding and control of the laser evolution in tenuous plasmas, the response of the plasma medium, and its effect on the accelerating particles. We explore these phenomena in the weakly nonlinear regime, in which the laser power is similar to the critical power for self-focusing. Using Particle-In-Cell simulations with the code QuickPIC, we demonstrate that a laser pulse can remain focused in a plasma channel for hundreds of Rayleigh lengths and efficiently accelerate a high-quality electron beam to 100GeV (25GeV) in a single stage with average gradient 3.6GV/m (7.2GV/m).
TL;DR: In this article, an ultrashort electron bunch train with picosecond (ps) spacing was obtained for high-power terahertz (Thz) radiation production by various radiation mechanisms.
Abstract: Ultrashort electron bunch trains can be used for plasma wake field acceleration (PWFA) to overcome the limit of transformer ratio of a single electron bunch, or high-power terahertz (Thz) radiation production by various radiation mechanisms. Basic facility for high-power THz radiation development based on ultrashort electron beam has been set up at accelerator lab of TUB. Using birefringent crystal serials, ultraviolet (UV) pulse shaping for photocathode radio frequency gun to produce THz-repetition-rate pulse train was realized. Driven by such pulses, ultrashort electron bunch train with picosecond (ps) spacing was obtained for THz production. Measurement of the stacked UV pulse trains was done by difference frequency generation (DFG), and the measured group velocity mismatch of α-BBO crystal at 266.7-nm wavelength was 0.8 ps/mm. This method may also be applied to form ramped electron bunch trains for PWFA.
TL;DR: In this paper, non-planar (cylindrical and spherical) double layers (DLs) in two-ion-temperature dusty plasma, whose constituents are inertial negative dust, ions with two distinctive temperatures, and Boltzmann electrons, are studied by employing the reductive perturbation method.
Abstract: Non-planar (cylindrical and spherical) double layers (DLs) in two-ion-temperature dusty plasma, whose constituents are inertial negative dust, ions with two distinctive temperatures, and Boltzmann electrons, are studied by employing the reductive perturbation method. The modified Gardner equation describing the nonlinear propagation of dust-acoustic (DA) waves is derived, and its non-planar double layer solutions are analyzed numerically. The parametric regimes for the existence of DA DLs, which are found to be associated with positive potential only, are obtained. The basic features of non-planar DA DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations are discussed.