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Generation of a thin plasma jet with embedded gigagauss axial magnetic fields from the frontal impact of a short linearly polarized laser pulse on an overdense microtube target is considered. It is a new scheme of axial magnetic field generation without initial laser angular momentum. Three-dimensional particle-in-cell simulations show that the space-charge field of the laser expelled tube-front electrons will pull out carbon ions to form at the tube entrance a long-living low-density plasma bunch with gigagauss magnetic fields. The front center of the plasma bunch then stretches forward to form a thin gigagauss-magnetized plasma jet, which survives for sub-picosecond after the core of the laser has passed through the tube. [ABSTRACT FROM AUTHOR]

In experiments on the effect of magnetic field on electron transportation in laser–plasma interaction, the magnetic field is often produced by two coils and is mirror-like. In this paper, the transport and the reflection of fast electron beam generated in laser–plasma interaction in solid-density plasma immersed in a mirror magnetic field are studied using particle-in-cell simulation. The helicoidal motion of fast electrons in the field and the convergence of magnetic induction lines leads to the collimated transport and focusing of the fast electrons. The reflection of the fast electrons can lead to the decrease in the transmission ratio, and this reflection increases with the magnetic mirror ratio, but saturates at a certain level. [ABSTRACT FROM AUTHOR]

Oscillations of charged dust grains in the sheath region of a radio-frequency plasma containing negative ions are studied using a one-dimensional model for collisional sheaths. The forces on a dust grain in the sheath region are first analyzed and the force-balance conditions found. Oscillations of the levitated dusts are then investigated. Linear lattice waves, including one-dimensional longitudinal and two-dimensional hexagonal transverse lattice waves, as well as the effects of the negative ions and external magnetic field on the waves, are discussed. [ABSTRACT FROM AUTHOR]

Plasma transport in a hybrid dc vacuum arc plasma source for ion deposition and plasma immersion treatment is considered. It is found that external crossed electric and magnetic fields near the substrate can significantly reduce the relative amplitude of ion current fluctuations Īf at the substrate surface. In particular, Īf decreases with the applied magnetic field when the bias voltage exceeds 300 V, thus allowing one to reduce the deviations from the rated process parameters. This phenomenon can be attributed to an interaction between the metal-plasma jet from the arc source and the discharge plasma in the crossed fields. [ABSTRACT FROM AUTHOR]

The effect of perpendicular (to the direction of shock propagation) magnetic fields on electron shock-surfing acceleration (ESSA) is investigated. Two-dimensional particle-in-cell simulations show that the strength of background magnetic fields can significantly affect the shock formation process and the electrostatic field structure near the leading edge of the shock. It is found that ESSA is most efficient when the ratio of electron cyclotron frequency to plasma frequency is about 0.1. In this case, there are two types of electrostatic field structures near the shock edge, namely, small-scale filamentary and large-scale dipole electric fields, induced by the Buneman instability and fluid compression, respectively. In such a mixed field structure, the affected electrons can undergo multiple accelerations and gain much higher energies than that under weaker or stronger background magnetic fields. [ABSTRACT FROM AUTHOR]

Excitation of streamers by modulationally unstable small-scale drift-Alfven wave (SSDAW) is investigated. It is found that the excitation depends strongly on the propagation direction of the SSDAW, and the ion and electron diamagnetic drift waves are both unstable due to the generation of streamers. It is also shown that zonal flows can be effectively excited by the SSDAW with the propagation direction different from that for streamer excitation. [ABSTRACT FROM AUTHOR]

It is shown that the intense quasistatic electric and magnetic fields self-generated near the axis of the laser-driven channel in an appropriately profiled preplasma during ultraintense laser interaction with a thin target can create dense relativistic electron bunches. The latter easily penetrate through the target and can greatly enhance the sheath field at the rear, resulting in significant increase in the laser-to-ion energy conversion efficiency and the maximum energy of the target normal sheath accelerated ions. Particle-in-cell simulations show that with a hydrogen targets a proton beam of peak energy ∼38 MeV and energy conversion efficiency ≥6.5% can be produced by a linearly polarized 5 × 1019 W/cm2 laser. An analytical model is also proposed and its results agree well with those of the simulations. [ABSTRACT FROM AUTHOR]

The effect of a guide field on the linear lower-hybrid drift instability (LHDI) in a thin current sheet containing energetic particles is investigated using kinetic theory. It is found that the symmetry properties of the LHD modes are destroyed by the guide field. The LHDI growth rate decreases with the strength of the latter, and the perturbed magnetic field is much higher than that of the guide-field free case. [ABSTRACT FROM AUTHOR]

Generation and propagation of attosecond electron bunches along a cone-and-channel target are investigated by particle-in-cell simulation. The target electrons are pulled out by the oscillating electric field of an intense laser pulse irradiating a cone target and accelerated forward along the cone walls. It is shown that the energetic electrons can be further guided and confined by a channel attached to the cone tip. The propagation of these electrons along the channel induces a strong quasistatic magnetic field as well as a sheath electric field since a part of the energetic electrons expands into the surrounding vacuum. The electromagnetic field in turn confines the surface currents. With the cone-and-channel target the energetic electrons can be much better collimated and propagate much farther than that from the classical cone target. [ABSTRACT FROM AUTHOR]

Hot electron transport in a funnel-guided target is investigated using two-dimensional hybrid simulations. Relativistic electrons generated by a petawatt picosecond short-pulse laser interacting with a gold slab are guided by a funnel to the compressed core region of the fuel. It is shown that as the energetic electrons propagate into the compressed core, the interface magnetic fields in the inner and outer surfaces of the funnel can change sign so that the fast electrons are efficiently guided in the gold funnel to reach the dense core. It is also shown that with funnel guiding, fuel heating is enhanced compared to that without the funnel. The findings here may be useful in the design of more efficient fast-ignition schemes, as well as in other applications involving transport and heating of energetic electrons in targets. [ABSTRACT FROM AUTHOR]

The trajectories of electrons originating from different initial locations in the unperturbed plasma during the interaction of an ultraintense laser with underdense plasma in the bubble regime are followed by particle-in-cell simulation. It is found that plasma electrons initially aligned with the rim of the laser focal spot contribute most to the bow wave in front of the bubble and those aligned with the lateral bubble sheath edge contribute most to the self-injection at the back of the bubble. A scaling law between the transverse electric and magnetic fields for the case where there are many electrons in the bubble is given and discussed in terms of betatron oscillations of the injected electrons. [ABSTRACT FROM AUTHOR]

An analytical model for the electromagnetic fields in the bubble regime of the interaction of ultrahigh-intensity laser with plasma is given. The two-dimensional model is based on the results of particle-in-cell simulation and includes the bubble front region. It is used to consider the generation of dense ultrashort quasimonoenergetic high-energy electron bunches. The resulting bunch parameters agree fairly well with those from the simulation. [ABSTRACT FROM AUTHOR]

The transport and heating of laser produced relativistic electron beam propagating through coaxial two-layer solid-density plasma are studied using two-dimensional hybrid fluid-particle-in-cell simulation. When the energetic electrons enter the plastic and copper target, stronger heating is observed in the plastic plasma. The heating of the plasma electrons and the formation of tens of million Gauss interface magnetic fields results from a large difference of the velocities of the returning electrons at the two sides of the interface. Moreover, the electron beam can have a completely different emittance behavior when the target consists of different-material layers. [ABSTRACT FROM AUTHOR]

The relation between several magnetic waves and instabilities is clarified. These modes involve only electron dynamics. It is shown that in the parameter regime of interest there are no propagating unstable waves driven by the first order baroclinic effect. [ABSTRACT FROM AUTHOR]

The effect of resistivity gradient on laser-driven electron transport and ion acceleration is investigated using collisional particle-in-cell simulation. The study is motivated by recent proton acceleration experiments [Gizzi et al., Phys. Rev. ST Accel. Beams 14, 011301 (2011)], which showed significant effect of the resistivity gradient in layered targets on the proton angular spread. This effect is reproduced in the present simulations. It is found that resistivity-gradient generation of magnetic fields and inhibition of electron transport is significantly enhanced when the feedback interaction between the magnetic field and the fast-electron current is included. Filamentation of the laser-generated hot electron jets inside the target, considered as the origin of the nonuniform proton patterns observed in the experiments, is clearly suppressed by the resistive magnetic field. As a result, the electrostatic sheath field at the target back surface acquires a relatively smooth profile, which contributes to the superior quality of the proton beams accelerated off layered targets in the experiments. [ABSTRACT FROM AUTHOR]

Proton acceleration by ultra-intense laser pulse irradiating a target with cross-section smaller than the laser spot size and connected to a parabolic density channel is investigated. The target splits the laser into two parallel propagating parts, which snowplow the back-side plasma electrons along their paths, creating two adjacent parallel wakes and an intense return current in the gap between them. The radiation-pressure pre-accelerated target protons trapped in the wake fields now undergo acceleration as well as collimation by the quasistatic wake electrostatic and magnetic fields. Particle-in-cell simulations show that stable long-distance acceleration can be realized, and a 30 fs monoenergetic ion beam of >10 GeV peak energy and <2° divergence can be produced by a circularly polarized laser pulse at an intensity of about 1022 W/cm2. [ABSTRACT FROM AUTHOR]

Generation of 1012 W/cm2 Smith-Purcell radiation in the infrared (5-20μm) regime from the interaction of high-density laser-produced MeV electrons is proposed. The electron bunch is produced by impinging an intense ultrashort laser pulse on a metallic target with a grated upper surface. Particle-in-cell simulation shows that the electron bunch can efficiently couple to the periodic structure through the quasistatic self-generated electric and magnetic fields there. An analytical model for predicting the dependence of the radiation intensity on the laser and grating parameters is also proposed. With appropriate laser and grating parameters, the proposed scheme provides a tunable source for intense radiation in the infrared regime. [ABSTRACT FROM AUTHOR]

Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson et al. [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fanlike electron outflow region including three well-collimated electron jets appears. The (> 1 MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS. [ABSTRACT FROM AUTHOR]

A right-hand circularly polarized electromagnetic wave can propagate in a sufficiently magnetized plasma of any density without encountering cutoff in the whistler mode. With the recent realization of tens-kilotesla magnetic fields, laser propagation in highly magnetized high-density plasmas has become of practical interest, especially for heating plasmas to high energy density and igniting fusion targets. In this paper, the whistler regime of laser-plasma interaction is discussed. It is shown by one- and two-dimensional particle-in-cell simulations that moderately intense right-hand circularly polarized laser light can enter and propagate in high-density plasma and heat it efficiently because of the significantly reduced wave length and speed. [ABSTRACT FROM AUTHOR]