Laser-plasma Interaction Experiments Research Articles

Nonlinear electrostatic kelvin-helmholtz shock waves in a viscous electron-positron-ion plasma with non-maxwellian distribution

A theoretical investigation is carried out for nonlinear electrostatic Kelvin-Helmholtz (K-H) shock waves in a magnetized electron-positron-ion viscous plasma in the presence of transport equations and non-Maxwellian particles by following the generalized (r, q) distribution function. The propagation of electrostatic K-H modes are studied both in the presence of trapped and free electrons. The nonlinear analysis with inclusion of plasma transport properties (magnetic viscosity and heat conduction) lead to nonlinear electrostatic K-H mode in the form of shock like waves by solving the modified Burgers’ equation. The electrostatic K-H shocks are investigated numerically with effect of different plasma parameters such as shear velocity and non-Maxwellian distributed particles. It is observed that the striking features (viz., amplitude and width of dissipative shock through the solution of Burgers’ equation) of the K-H mode are significantly modified by the effects of non-thermality of electrons and positrons both at shoulder and tails along with shear velocity due to viscosity. The relevancy of our work to the observations in space (viz., cometary comae and earth’s ionosphere), astrophysical (viz., pulsars) and laboratory (viz., solid-high intense laser plasma interaction experiments) plasmas is highlighted.

Synchronized off-harmonic probe laser with highly variable pulse duration for laser–plasma interaction experiments

Abstract This paper presents the development and experimental utilization of a synchronized off-harmonic laser system designed as a probe for ultra-intense laser–plasma interaction experiments. The system exhibits a novel seed-generation design, allowing for a variable pulse duration spanning over more than three orders of magnitude, from 3.45 picoseconds to 10 nanoseconds. This makes it suitable for various plasma diagnostics and visualization techniques. In a side-view configuration, the laser was employed for interferometry and streaked shadowgraphy of a laser-induced plasma while successfully suppressing the self-emission background of the laser–plasma interaction, resulting in a signal-to-self-emission ratio of 110 for this setup. These properties enable the probe to yield valuable insights into the plasma dynamics and interactions at the PHELIX facility and to be deployed at various laser facilities due to its easy-to-implement design.

The effects of incident light wavelength difference on the collective stimulated Brillouin scattering in plasmas

The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility. Although each beam intensity is below its individual threshold for stimulated Brillouin backscattering (SBS), collective behaviors are excited to enhance the octad SBS. In particular, when two-color/cone lasers with wavelength separation 0.3 nm are used, the backward SBS reflectivities show novel behavior in which beams of longer wavelength achieve higher SBS gain. This property of SBS can be attributed to the rotation of the wave vectors of common ion acoustic waves due to the competition of detunings between geometrical angle and wavelength separation. This mechanism is confirmed using massively parallel supercomputer simulations with the three-dimensional laser–plasma interaction code LAP3D.

Calibration of the sub-aperture backscatter system on OMEGA EP

The sub-aperture backscatter (SABS) diagnostic on the OMEGA EP Laser System [Waxer etal., Opt. Photonics News 16, 30 (2005)] is a diagnostic that is used to measure the backscattered and sidescattered light during laser-plasma interaction experiments [W. L. Kruer, The Physics of Laser Plasma Interactions, Frontiers in Physics Vol. 73, edited by D. Pines (Addison-Wesley, Redwood City, CA, 1988) and Myatt etal., Phys. Plasmas 21, 055501 (2014)] that are relevant to high-energy-density physics and inertial confinement fusion. The diagnostic collects stimulated Brillouin scattering (SBS) UV light at around 351nm and stimulated Raman scattering (SRS) in the visible-light regime in the 420-720-nm-wavelength range and provides spectrally and temporally resolved information. Five 1-in. light collectors, composed of a lens, ground glass diffuser, and coupling into a 300-μm fiber, are positioned behind the last steering mirror on one of the four beamlines to catch a portion of the beam cross section (∼1.5%) of the emission that is scattered into the beamline. The SRS light is collected in two light collectors, combined, and transported via graded index fibers to a streaked spectrometer. The SABS-SRS streak spectrometer has a temporal and spectral resolution of 100ps and 1nm, respectively. Three other light collectors collect, combine, and transport the SBS signal to a Hamamatsu high-voltage photodiode, where an oscilloscope digitizes the data, providing a time resolution of better than 1ns. To obtain an absolute energy calibration of SRS measurements, light signals of known energy and wavelength were injected into the light collectors one at a time. The resulting counts on the streak camera charge-coupled device for SRS are then correlated with the incident fluence of scattered light at the light collector in order to allow a quantitative assessment of streak camera sensitivity to determine the energy of the scattered light during experiments. The measurements were performed in situ from the light collectors to the detectors. Additional offline measurements provided the transmission of the optics between the target chamber center and the light collectors.

Nonlinear interaction of the fast magnetosonic wave with the extraordinary mode laser and ion-scaled turbulence generation in the magnetized plasma

This study introduces a nonlinear wave-wave coupling model to understand the nature of the turbulence generation at the ion scale observed in the interaction of high-intensity laser with plasma. For this nonlinear coupling of waves, the fast magnetosonic wave and the extraordinary mode laser are taken into account, along with the nonlinear ponderomotive force. The model dynamical equations have been developed for the extraordinary mode laser and the fast magnetosonic wave. Laboratory simulations have been employed to solve the obtained model equations utilizing the finite difference and pseudo-spectral methods. The simulation results show the initiation of the nonlinear progression of the laser beam at an early time and its turbulent nature at a later time. The background density perturbation, along with the cavity and hump caused by the ponderomotive force, has also been studied. The simulation results demonstrate that the propagation angle of the fast magnetosonic wave affects the magnitudes of the localization of the laser beam (pump wave) and the perturbed background density. The turbulent power spectra (ensemble-averaged) have also been studied for the different propagation angles of the fast magnetosonic wave. The turbulent spectra demonstrate that the plasma turbulence is MHD-type at small-scale lengths and ion-dominated at larger-scale lengths. This study also observed that the simulation results have some resemblance with the experimental results reported by Chatterjee et al.12 in the intense laser-plasma interaction experiment at a laboratory astrophysical scale.

Identification of stimulated Raman side scattering in near-spherical coronal plasmas on OMEGA EP

Recent spherical-target laser–plasma interaction experiments, performed on the OMEGA EP laser, have been analyzed for stimulated Raman scattering (SRS). This has been motivated by results obtained on the National Ignition Facility (NIF) that have demonstrated the importance of SRS, and in particular SRS side scatter, for directly driven inertial confinement fusion (ICF) conditions [Rosenberg et al. Phys. Rev. Lett. 120, 055001 (2018); Michel et al. Phys. Rev. E 99, 033203 (2019)]. The analysis, based on a generalized ray tracing approach, is described and is shown to explain the observed scattered light spectra: it identifies SRS convective scattering, from portions of each incident beam where the scattered electromagnetic wave is generated in the direction parallel to contours of constant density, as the dominant contribution. This result is novel, as SRS is mostly associated with plasmas of higher electron temperature (Te≳3−4 keV) and longer density scale length (≳600 μm) than those considered here (Te∼1−3 keV, Ln∼150 μm) for the relevant overlapped irradiation intensities I≲1015 W/cm2. A combination of the high single-beam intensity on OMEGA EP and the side-scattering geometry, that has been identified, is responsible for this result. It is further suggested that the OMEGA EP platform could provide a good surrogate in which to develop SRS mitigation strategies.

Additive manufactured foam targets for experiments on high-power laser–matter interaction

Additive manufactured (AM) foams in the context of high-power laser–matter interaction have emerged as a topic of significant interest. Printed foam targets provide a highly controlled environment for laser interaction and permit a high degree of versatility in terms of average density, spatial structure, and materials. These features are of great value to a variety of applications, including inertial confinement fusion and generation of intense x-rays and gamma rays. This paper describes an approach to the design and fabrication of AM foams for laser–plasma interaction experiments, including the selection of cellular structure, optimization of mechanical properties using a finite element approach, and foam printing on dielectric and conducting substrates.

Electromagnetic solitons and their stability in relativistic degenerate dense plasmas with two electron species

The evolution of electromagnetic (EM) solitons due to nonlinear coupling of circularly polarized intense laser pulses with low-frequency electron-acoustic perturbations is studied in relativistic degenerate dense astrophysical plasmas with two groups of electrons: a sparse population of classical relativistic electrons and a dense population of relativistic degenerate electron gas. Different forms of localized stationary solutions are obtained and their properties are analyzed. Using the Vakhitov-Kolokolov stability criterion, the conditions for the existence and stability of a moving EM soliton are also studied. It is noted that the stable and unstable regions shift around the plane of soliton eigenfrequency and the soliton velocity due to the effects of relativistic degeneracy, the fraction of classical to degenerate electrons and the EM wave frequency. Furthermore, while the standing solitons exhibit stable profiles for a longer time, the moving solitons, however, can be stable or unstable depending on the degree of electron degeneracy, the soliton eigenfrequency and the soliton velocity. The latter with an enhanced value can eventually lead to a soliton collapse. The results should be useful for understanding the formation of solitons in the coupling of highly intense laser pulses with slow response of degenerate dense plasmas in the next generation laser-plasma interaction experiments as well as the novel features of x-ray and γ-ray pulses that originate from compact astrophysical objects.

Frequency chirp effects on stimulated Raman scattering in inhomogeneous plasmas

Previous studies have shown that the use of laser bandwidth may mitigate the growth of stimulated Raman scattering (SRS) in laser plasma interaction experiments, in particular, when the spectrum of the driving (or pump) laser is composed of uniformly distributed frequency components with a well-chosen bandwidth [for example, Luo et al., Phys. Plasmas 29, 032102 (2022); Wen et al., ibid. 28, 042109 (2021); and Follett et al., ibid. 26, 062111 (2019)]. Here, we investigate the effects of frequency chirp in the pump laser on backward SRS in inhomogeneous plasmas, taking into account kinetic effects associated with the nonlinear detuning of the parametric resonance due to high-amplitude electron plasma waves (EPW). Through theoretical considerations and numerical simulations, using a multi-dimensional particle-in-cell (PIC) code, it is shown that positive frequency chirp rates lead to a displacement of the resonance in the plasma profile. For a sufficiently strong positive chirp rate, such that the resonance displacement is faster than the EPW group velocity, the EPWs prove to remain limited in amplitude such that SRS is suppressed. The required frequency chirp rate corresponds to a laser bandwidth of about 1%–2%.

Electron Acoustic Peregrine Breathers in a Quantum Plasma With 1-D Temperature Anisotropy

In the work, we study the formation of electron acoustic Korteweg–de Vries (KdV) solitons and their gradual nonlinear evolution into a peregrine soliton (PS) in a dense plasma at finite temperature with quantum effects. The plasma under consideration has temperature anisotropy along the direction of wave propagation. Such an anisotropy is due to the initial disturbance incorporated in the system or due to the lack of homogeneity of field quantities. We have studied both the linear and nonlinear characteristics of their dispersion relation. By employing reductive perturbation technique, we have obtained the KdV equation and studied the characteristics of the solitary structures. The effect of external forcing term which leads to self-interaction among different parts of the system and the gradual conversion of the waveform into Peregrine breather mode is analytically studied. Finally, we study the dynamical properties of the system and its dependence on plasma parameters. This theoretical study will help in predicting possible characteristics in laser plasma interaction and beam plasma experiments in which there are instances of temperature anisotropy.

Methods for extremely sparse-angle proton tomography.

Proton radiography is a widely fielded diagnostic used to measure magnetic structures in plasma. The deflection of protons with multi-MeV kinetic energy by the magnetic fields is used to infer their path-integrated field strength. Here the use of tomographic methods is proposed for the first time to lift the degeneracy inherent in these path-integrated measurements, allowing full reconstruction of spatially resolved magnetic field structures in three dimensions. Two techniques are proposed which improve the performance of tomographic reconstruction algorithms in cases with severely limited numbers of available probe beams, as is the case in laser-plasma interaction experiments where the probes are created by short, high-power laser pulse irradiation of secondary foil targets. A new configuration allowing production of more proton beams from a single short laser pulse is also presented and proposed for use in tandem with these analytical advancements.

Structuring Free-Standing Foils for Laser-Driven Particle Acceleration Experiments

The recent development of petawatt-class laser systems sets a focus on the development of ultra-thin free-standing targets to access enhanced particle acceleration schemes vital for future applications, such as, medical and laser-driven nuclear physics. Specific strategies are required to improve the laser-to-particle energy conversion efficiency and increase the maximum particle energy. One of the promising approaches is based on the target design optimization; either by tuning key parameters which will strongly affect the laser-matter interaction process (e.g., material, composition, density, thickness, lateral dimensions, and shape) or by using micro/nanostructures on the target surface. At ELI-NP, considerable efforts are dedicated to extend the target capabilities beyond simple planar target design and develop complex targets with tailored properties suitable for high-power laser-plasma interaction experiments, as well as for studies with gamma and positrons beams. The paper provides an overview of the manufacturing capabilities currently available within ELI-NP Targets Laboratory for providing users with certain types of solid targets, specifically micro/nanostructured gold and copper foils and microns thick, porous anodized alumina. Also, optimization studies of alternative patterns (micro/nanodots) on silicon substrate are presented for future implementation on metallic free-standing thin foils.

Design of modular multi-channel electron spectrometers for application in laser matter interaction experiments at Prague Asterix Laser System

This paper describes design, development, and implementation of a multi-channel magnetic electron spectrometer for the application in laser-plasma interaction experiments carried out at the Prague Asterix Laser System. Modular design of the spectrometer allows the setup in variable configurations to evaluate the angular distribution of hot electron emission. The angular array configuration of the electron spectrometers consists of 16 channels mounted around the target. The modules incorporate a plastic electron collimator designed to suppress the secondary radiation by absorbing the wide angle scattered electrons and photons inside the collimator. The compact model of the spectrometer measures electron energies in the range from 50keV to 1.5MeV using ferrite magnets and from 250keV to 5MeV using stronger neodymium magnets. An extended model of the spectrometer increases the measured energy range up to 21MeV or 35MeV using ferrite or neodymium magnets, respectively. Position to energy calibration was obtained using the particle tracking simulations. The experimental results show the measured angularly resolved electron energy distribution functions from interaction with solid targets. The angular distribution of hot electron temperature, the total flux, and the maximum electron energy show a directional dependence. The measured values of these quantities increase toward the target normal. For a copper target, the average amount of measured electron flux is 1.36 × 1011, which corresponds to the total charge of about 21nC.

Calibration of imaging plates sensitivity to high energy photons and ions for laser-plasma interaction sources

Imaging plates are widely used in laser-plasma interaction experiments for detection of electrons, x-ray, gamma-ray, ions, and neutrons, therefore, the calibration of imaging plates to different types of ionizing and non-ionizing radiation is vital. In this paper, a universal response function of FUJI BAS-TR imaging plate is presented using experiment and Monte-Carlo simulation with respect to high-energy photons and ions. The sensitivity of imaging plate sensitivity to x-ray radiation was examined using radioactive Co-60 isotope. Furthermore, the fading and decay mechanism affected by phosphor stimulated process were also investigated by employing the high energy gamma-rays produced in laser-plasma experiment. Finally, an ion spectrometer was designed to examine the IP response to different ion energies during a laser-driven plasma experiment. The universal relation given, can be used to evaluate the response of the imaging plate against any other types of radiation.

Wavebreaking amplitudes in warm, inhomogeneous plasmas revisited

The effect of electron temperature on the space–time evolution of nonlinear plasma oscillations in an inhomogeneous plasma is studied using a one-dimensional particle-in-cell code. It is observed that, for an inhomogeneous plasma, there exists a critical value of electron temperature beyond which the wave does not break. These simulation results, which are in conformity with the purely theoretical arguments presented by Trines [Phys. Rev. E 79, 056406 (2009)], represent the first numerical elucidation of the effect of plasma pressure on wave breaking amplitude. The results presented are of relevance to experiments where moderate to large amplitude plasma waves are excited, e.g., laser–plasma interaction experiments.

The L4n laser beamline of the P3-installation: Towards high-repetition rate high-energy density physics at ELI-Beamlines

The P3 installation of ELI-Beamlines is conceived as an experimental platform for multiple high-repetition-rate laser beams spanning time scales from femtosecond via picosecond to nanosecond. The upcoming L4n laser beamline will provide shaped nanosecond pulses of up to 1.9 kJ at a maximum repetition rate of 1 shot/min. This beamline will provide unique possibilities for high-pressure, high-energy-density physics, warm dense matter, and laser–plasma interaction experiments. Owing to the high repetition rate, it will become possible to obtain considerable improvements in data statistics, in particular, for equation-of-state data sets. The nanosecond beam will be coupled with short sub-picosecond pulses, providing high-resolution diagnostic tools by either irradiating a backlighter target or driving a betatron setup to generate energetic electrons and hard X-rays.

Measurements of electron beam ring structures from laser wakefield accelerators

Laser-plasma interaction experiments using a 70 TW short-pulse laser were conducted to investigate the properties of electron beams produced from laser wakefield acceleration. In addition to narrow divergence electron beams in excess of 200 MeV, lower energy components of the electron beam were observed to have an annular emission pattern with much larger divergence. This ring-shaped component of the beam is up to several MeV in energy and gives rise to a corresponding increase in the divergence of bremsstrahlung x-rays while producing more background radiation. Scaling measurements of the emission angle of the beam with respect to plasma density were also made. From 3D numerical simulations of the interaction, it is shown that this phenomenon results from energetic electrons in the laser-driven wakefield which are not trapped by the plasma wave, but which can still obtain some longitudinal momentum from the interaction.

X-ray spectroscopy of planar laser-plasma interaction experiments at the National Ignition Facility

X-ray spectroscopy has been newly used to diagnose electron temperatures in planar-geometry experiments at the National Ignition Facility (NIF) designed to study laser-plasma interactions at plasma conditions relevant to direct-drive ignition. These experiments used a buried co-mixed Mn/Co microstrip in a CH ablator in experiments that generated long scale-length plasmas susceptible to stimulated Raman scattering (SRS). Time-resolved Mn and Co K-shell spectra, diagnosed using the NIF x-ray spectrometer, were analyzed by fitting to synthetic spectra based on a detailed atomic model of emission from the microstrip. The electron temperature at the time when the microstrip passes through the quarter-critical density surface, the key region for the development of SRS, was inferred to be around 2–3 keV. These measurements constrain 2-D DRACO radiation-hydrodynamic modeling of the planar experiments, important for determining plasma conditions pertinent to SRS, and demonstrate that this platform approaches direct-drive ignition-relevant conditions. The modeling is also assessed by a direct comparison of measured spectra to modeled spectra generated by DRACO in conjunction with the atomic physics postprocessor code SPECT3D.

Nonlinear ion acoustic waves in a relativistic degenerate plasma with Landau diamagnetism and electron trapping

We consider the effects of trapping in a relativistic degenerate plasma with quantizing magnetic field. The linear dispersion relation for such an ion acoustic wave is derived and the propagation characteristics of these waves are discussed. The Sagdeev potential for the formation of arbitrary amplitude solitary structures is obtained and it is seen that only compressive solitary structures are formed for the relativistic degenerate quantized magnetoplasma. The dependence of the linear and nonlinear propagation characteristics of ion acoustic waves on different plasma parameters is explored. A comparison is also made with the previous studies. The useful applications of the present investigation in dense astrophysical environments like white dwarf stars and neutron stars, in semiconductor physics, in high-energy density physics, in inertial confinement fusion and in next generation laser–plasma interaction experiments are pointed out.

Characterization of a two-channel, high resolution hard x-ray microscope using Fresnel zone plates for laser-plasma interaction experiments

New X-ray imaging techniques are currently being developed at the "Commissariat à l'énergie atomique et aux énergies alternatives" in the context of Inertial Confinement Fusion. Fresnel zone plates (FZPs) are being considered as they can perform high-resolution and high-flux imaging in the X-ray domain. Here we present the characterization of a bi-lens FZPs resolution used in an imager prototype, designed for the LULI2000 laser facility. Characterization was performed on a synchrotron radiation facility and on a femtosecond laser facility. The resolution of the two FZP channels was measured to be between 2.4 μm and 5.2 μm and the expected total resolution for the diagnostic was to be 3.3 μm.