The collective motion of dust particles during the mode-coupling induced melting of a two-dimensional plasma crystal is explored in molecular dynamics simulations. The crystal is compressed horizontally by an anisotropic confinement. This compression leads to an asymmetric triggering of the mode-coupling instability which is accompanied by alternating chains of in-phase and anti-phase oscillating particles. A new order parameter is proposed to quantify the synchronization with respect to different directions of the crystal. Depending on the orientation of the confinement anisotropy, mode-coupling instability and synchronized motion are observed in one or two directions. Notably, the synchronization is found to be direction-dependent. The good agreement with experiments suggests that the confinement anisotropy can be used to explain the observed synchronization process.
Experimental results for the reflection coefficient of shock-compressed dense Xenon plasmas at pressures of 1.6 - 17 GPa and temperatures around 30 000 K using a laser beam with λ= 1.06 10^-6 m are compared with calculations based on different theoretical approaches to the dynamical collision frequency. It is found that a reasonable description can be given assuming a spatial electron density profile corresponding to a finite width of the shock wave front of about $2 10^-6 m.
Non-modal kinetic theory of the stability of the compressed-sheared plasma flows generated by the inhomogeneous microscale turbulence in the tokamak edge plasma
The appearance of the chaotic synchronization regimes has been discovered for the coupled spatially extended beam-plasma Pierce systems. The coupling was introduced only on the right bound of each subsystem. It has been shown that with coupling increase the spatially extended beam-plasma systems show the transition from asynchronous behavior to the phase synchronization and then to the complete synchronization regime. For the consideration of the chaotic synchronization we used the concept of time scale synchronization described in work [Chaos, 14, 3 (2004) 603-610] and based on the introducti…
A feedforward scheme is applied for drift waves control in a magnetized magnetron sputtering plasma. A system of driven electrodes collecting electron current in a limited region of the explored plasma is used to interact with unstable drift waves. Drift waves actually appear as electrostatic modes characterized by discrete wavelengths of the order of few centimeters and frequencies of about 100 kHz. The effect of external quasi-periodic, both in time and space, travelling perturbations is studied. Particular emphasis is given to the role played by the phase relation between the natural and th…
Compressed Ultrafast Photography of Plasmas Formed from Laser Breakdown of Dense Gases Reveals that Internal Processes Dominate Evolution at Early Times
Modern particle accelerators and their applications increasingly rely on precisely coordinated interactions of intense charged particle and laser beams. Femtosecond-scale synchronization alongside micrometre-scale spatial precision are essential e.g. for pump-probe experiments, seeding and diagnostics of advanced light sources and for plasma-based accelerators. State-of-the-art temporal or spatial diagnostics typically operate with low-intensity beams to avoid material damage at high intensity. As such, we present a plasma-based approach, which allows measurement of both temporal and spatial o…
Plasma in the earth's magnetosphere is subjected to compression during geomagnetically active periods and relaxation in subsequent quiet times. Repeated compression and relaxation is the origin of much of the plasma dynamics and intermittency in the near-earth environment. An observable manifestation of compression is the thinning of the plasma sheet resulting in magnetic reconnection when the solar wind mass, energy, and momentum floods into the magnetosphere culminating in the spectacular auroral display. This phenomenon is rich in physics at all scale sizes, which are causally interconnecte…
Magnetothermodynamics (MTD) is the study of compression and expansion of magnetized plasma with an eye towards identifying equations of state for magneto-inertial fusion experiments. We present recent results from SSX experiments on the thermodynamics of compressed magnetized plasmas. In these experiments, we generate twisted flux ropes of magnetized, relaxed plasma accelerated from one end of a $1.5~m$ long copper flux conserver, and observe their compression in a closed conducting boundary installed at the other end. Plasma parameters are measured during compression. The instances of ion hea…
We have explored the thermodynamics of compressed magnetized plasmas in laboratory experiments and we call these studies "magnetothermodynamics". The experiments are carried out in the Swarthmore Spheromak eXperiment device. In this device, a magnetized plasma source is located at one end and at the other end, a closed conducting can is installed. We generate parcels of magnetized plasma and observe their compression against the end wall of the conducting cylinder. The plasma parameters such as plasma density, temperature, and magnetic field are measured during compression using HeNe laser int…
The design of inertial confinement fusion (ICF) ignition targets requires radiation-hydrodynamics simulations with accurate models of the fundamental material properties (i.e., equation of state, opacity, and conductivity). Validation of these models are required via experimentation. A feasibility study of using spatially-integrated, spectrally-resolved, X-ray Thomson scattering (XRTS) measurements to diagnose the temperature, density, and ionization of the compressed DT shell and hot spot of a laser direct-drive implosion at two-thirds convergence was conducted. Synthetic scattering spectra w…
Particle-in-cell (PIC) simulation results of sustained acceleration of electron-positron (e+e-) plasmas by comoving electromagnetic (EM) pulses are presented. When a thin slab of overdense e+e- plasma is irradiated with linear-polarized ultra-intense short laser pulses from both sides, the pulses are transmitted when the plasma is compressed to thinner than ~ 2 relativistic skin depths. A fraction of the plasma is then captured and efficiently accelerated by self-induced JxB forces. For 1 micron laser and 1021Wcm-2 intensity, the maximum energy exceeds GeV in a picosecond.
In this work linear stability analysis of a magnetized dusty plasma with an anisotropic dust component having transversal motions much stronger than motions parallel to the external magnetic field, and isotropic light plasma components is described. Such a situation presumably establishes in a shock compressed space dusty plasma downstream the shock front. Oblique low-frequency magneto-hydrodynamic waves ($ω\ll ω_{cd}$, $ω_{cd}$ being the dust cyclotron frequency) are shown to be undergone to the mirror instability. Consequences for nonthermal dust destruction behind shock fronts in the inters…
The problem of calculation of the reflectivity of non-ideal shock-compressed plasmas is revisited. The dielectric formalism based on the method of moments incorporating exact asymptotic forms and sum rules is applied to the new experimental data. The approach is based on the Ansatz of reflection of laser radiation from a thin shock-front and possesses one adjustable parameter which depends only on the thermodynamic conditions of the experiment. A self-consistent agreement with all available experimental data is achieved.
Propagation of short and ultra-intense laser pulses in a semi-infinite space of overdense hydrogen plasma is analyzed via fully-relativistic, real geometry particle-in-cell (PIC) simulations including radiation friction. The relativistic transparency and hole-boring regimes are found to be sensitive to the transverse plasma field, backward light reflection, and laser pulse filamentation. For laser intensities approaching $I\sim10^{24}$ W/cm$^2$ the direct laser acceleration of protons, along with ion Coulomb explosion, results in their injection into the acceleration phase of the compressed el…
Two-dimensional Particle-In-Cell simulations are used to explore collisionless shock acceleration in the corona plasma surrounding the compressed core of an inertial confinement fusion pellet. We show that an intense laser pulse interacting with the long scale-length plasma corona is able to launch a collisionless shock around the critical density. The nonlinear wave travels up-ramp through the plasma reflecting and accelerating the background ions. Our results suggest that protons with characteristics suitable for ion fast ignition may be achieved in this way.
Interaction of a frequency-chirped laser pulse with single protons and a hydrogen plasma cell is studied analytically and by means of particle-in-cell simulations, respectively. Feasibility of generating ultra-intense (10^7 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1 %) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping of the laser pulse, allows the particles to gain sufficient kinetic energy (around 250 MeV) required for such applications as hadron cancer therapy, from state-of-the-a…
With the development of ultra intense laser technology, MeV ions from the laser foil interaction have been obtained by different mechanisms, such as target normal sheath acceleration, radiation pressure acceleration, collisionless shock acceleration, breakout afterburner, and a combination of different mechanisms. These energetic ion beams can be applied in fast ignition for inertial confinement fusion, medical therapy, and proton imaging. However, these ions are mainly accelerated in the laser propagation direction, and the ion acceleration in an azimuthal orientation is scarcely mentioned. H…
Warm dense matter--an exotic, highly compressed state on the boarder between solid and plasma phases is of high current interest, in particular for compact astrophysical objects, high pressure laboratory systems, and inertial confinement fusion. For many applications the interaction of quantum plasmas with energetic particles is crucial. Moreover, often the system is driven far out of equilibrium. In that case, there is high interest in time-dependent simulations to understand the physics, in particular, during thermalization. Recently a novel many-particle technique, the G1--G2 scheme was pre…
Particle-in-cell (PIC) simulations of collisionless jets of electrons and positrons in an ambient electron-proton plasma have revealed an acceleration of positrons at the expense of electron kinetic energy. The dominant instability within the jet was a filamentation instability between electrons, protons and positrons. In this work we show that a filamentation instability, between an initially unmagnetized ambient electron-proton plasma at rest and a beam of pair plasma that moves through it at a non-relativistic speed, indeed results in preferential positron acceleration. Filaments form that …
To indirectly evaluate the asymmetry of the radiation drive under limited measurement conditions in inertial confinement fusion research, we have proposed an integral method to approximate the three-dimensional self-radiation distribution of the compressed plasma core using only four pinhole images from a single laser entrance hole at a maximum projection angle of 10°. The simultaneous algebraic reconstruction technique (SART) that uses spatial constraints provided by the prior structural information and the central pinhole image is utilized in the simulation. The simulation results showed tha…
We study the development of coherent structures in local simulations of the magnetorotational instability in accretion discs in regimes of on-off intermittency. In a previous paper [Chian et al., Phys. Rev. Lett. 104, 254102 (2010)], we have shown that the laminar and bursty states due to the on-off spatiotemporal intermittency in a one-dimensional model of nonlinear waves correspond, respectively, to nonattracting coherent structures with higher and lower degrees of amplitude-phase synchronization. In this paper we extend these results to a three-dimensional model of magnetized Keplerian shea…
The document describes a numerical algorithm to simulate plasmas and fluids in the 3 dimensional space by the Euler method, in which the spatial meshes are fixed to the space. The plasmas and fluids move through the spacial Euler mesh boundary. The Euler method can represent a large deformation of the plasmas and fluids. On the other hand, when the plasmas or fluids are compressed to a high density, the spatial resolution should be ensured to describe the density change precisely. The present 3D Euler code is developed to simulate a nuclear fusion fuel ignition and burning. Therefore, the 3D E…
A scheme of laser wakefield acceleration, when a relatively rare and long bunch of non-relativistic or weakly-relativistic electrons is initially in front of the laser pulse, is suggested and considered. The motion of test electrons is studied both in the one-dimensional case (1D wakefield) and in the three-dimensional laser wakefield excited in a plasma channel. It is shown that the bunch is trapped, effectively compressed both in longitudinal and transverse directions and accelerated to ultra-relativistic energies in the region of first accelerating maximum of the wakefield. The accelerated …
Collisionless plasma shocks are efficient sources of non-thermal particle acceleration in space and astrophysical systems. We use hybrid (kinetic ions -- fluid electrons) simulations to examine the non-linear feedback of the self-generated energetic particles (cosmic rays, CRs) on the shock hydrodynamics. When CR acceleration is efficient, we find evidence of both an upstream precursor, where the inflowing plasma is compressed and heated, and a downstream postcursor, where the energy flux in CRs and amplified magnetic fields play a dynamical role. For the first time, we assess how non-linear m…
Energetic electromagnetic emissions by astrophysical jets like those that are launched during the collapse of a massive star and trigger gamma-ray bursts (GRBs) are partially attributed to relativistic internal shocks. The shocks are mediated in the collisionless plasma of such jets by the filamentation instability of counterstreaming particle beams. The filamentation instability grows fastest only if the beams move at a relativistic relative speed. We model here with a particle-in-cell (PIC) simulation the collision of two cold pair clouds at the speed c/2 (c: speed of light). We demonstrate …
Two-temperature, two-mass quasi-equilibrium plasmas may occur in electron-ion plasmas,nuclear-matter, as well as in electron-hole condensed-matter systems. Dense two-temperature hydrogen plasmas straddle the difficult partially - degenerate regime of electron densities and temperatures which are important in astrophysics, in inertial-confinement fusion research, and other areas of warm dense matter physics. Results from Kohn-Sham calculations and QMC are used to benchmark the procedures used in classical molecular-dynamics simulations, HNC and CHNC methods to derive electron-electron and elect…
