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.

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.

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.

Comparison study of the energy and instability of ion-acoustic solitary waves in magnetized electron–positron–ion quantum plasma

Notably, solitary waves that emerge from the nonlinear properties of plasmas are the main focus of many current studies of localized disturbances in both laboratory and astrophysical plasmas. By applying the reductive perturbation method, we derive the nonlinear homogeneous quantum Zakharov–Kuznetsov (QZK) equation in three-component collisionless quantum plasma consisting of electrons, positrons, and ions in the presence of an external static magnetic field. The solitary wave structures are dependent on the Bohm potential, magnetic field, obliqueness, species Fermi temperatures, and densities. The soliton’s electric field and energy are also derived and investigated, which were found to be reduced as the magnetic field increases. The instability growth rate is also derived by using the small-k perturbation expansion method. The previous parameters affect the instability growth rate as well. A comparison of the energy and instability growth rate behaviour against system parameters is carried out. Large energy and large instability growth rate occur at large values of positron density or lower values of ion density. At zero or small rotation angle, both decrease as the magnetic field increases. Our findings could help us understand the dynamics of magnetic white dwarfs, pulsar magnetospheres, semiconductor plasma, and high-intensity laser-solid matter interaction experiments where e-p-i plasma exists.

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.

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.

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.

The Beam Plasma Interactions Experiment: An Active Experiment Using Pulsed Electron Beams

The 1970s and 1980s were heydays for using active electron beam experiments to probe some of the fundamental physical processes that occur throughout the heliosphere and in astrophysical contexts. Electron beam experiments were used to study spacecraft charging and spacecraft-plasma coupling; beam-plasma interaction physics; magnetic bounce and drift physics; auroral physics; wave generation; and military applications. While these experiments were enormously successful, they were also limited by the technologies that were available at that time. New advances in space instrumentation, data collection, and accelerator technologies enable a revolutionary new generation of active experiments using electron beams in space. In this paper we discuss such an experiment, the Beam Plasma Interactions Experiment (Beam PIE), a sounding rocket experiment designed to (a) advance HEMT-based RF linear accelerator electron accelerator technology for space applications and (b) study the production of whistler and X-mode waves by modulated electron beams.

Prototype TM 01 mode launcher by using Pagoda‐shaped geometry in circular waveguide for microwave plasma interaction experiments at SYMPLE

SYstem for Microwave PLasma Experiments (SYMPLE) is an experimental system to investigate the physics of linear and nonlinear interaction of high-power microwave (HPM) with plasma in the Institute for Plasma Research (IPR), Gandhinagar, India. The objective of this paper was to present the designing and development of coaxial TEM to TM01 mode launcher in the circular waveguide for microwave plasma interaction experiments at SYMPLE. TEM mode was converted into TM01 mode by using aluminum made circular Pagoda-shaped geometry. TM01 mode launcher was hence successfully designed and developed. 3D full-wave electromagnetic solver was used to analyze and optimize the outcomes. The proposed configuration of mode launcher achieved the bandwidth of 658 MHz for S11 < −10 dB. The maximum value of achieved return loss was ~40 dB while insertion loss was ~0 dB at 3 GHz, which verified the ~100% transmission of power without any reflections. Mode purity was also verified by field distribution in the circular waveguide.

Active Experiments in Space: The Future

Planned active space experiments and ideas for future active space experiments are reviewed. Three active experiments being readied are DSX (Demonstration and Space eXperiments), SMART (Space Measurement of Rocket-released Turbulence), and BeamPIE (Beam Plasma Interaction Experiment). Ideas for future experiments include relativistic-electron-beam experiments for magnetic-field-line tracing, relativistic-electron-beam experiments to probe the middle atmosphere, plasma-wave launching using superparamagnetic-nanoparticle amplification of magnetic fields, the heavy-ion mass loading of collisionless magnetic-field-line reconnection, the use of electrostatically charged tethers to pitch-angle scatter radiation-belt particles, cold plasma releases to modify magnetospheric plasma physics, and neutral-gas releases to enhance neutral-particle imaging of the magnetosphere. Technologies that are being developed to enable future space active experiments are reviewed: this includes the development of compact relativistic accelerators, superparamagnetic particle amplified antennae, CubeSats, and a new understanding of how to control dynamic spacecraft charging. New capabilities to use laboratory facilities to design space active experiments as well as new computer-simulation capabilities to design and understand space active experiments are reviewed.

A washer gun plasma system for microwave-plasma interaction experiments.

A washer-gun based plasma system has been developed to enable high power microwave (HPM)-plasma interaction in a system for microwave plasma experiments. The critical pre-requisites of the plasma are density, ne ∼ (1-10) × 1017 m-3, uniformity over a radial extent ≈10 cm and axial extent ≈20-30 cm, an axial density gradient of scale-length Ln ≈ wavelength of HPM, and ambient pressure low enough to maintain electron-neutral collision frequency much less than plasma frequency. The system developed deploys a ten stage pulse forming network, discharged to the washer-gun to produce pulsed (τpulse ∼ 100 μs) discharges that get ejected into an experimental chamber. The system is capable of generating ne ∼ 1018 m-3 and Te ∼ 10 eV. Temporal and spatial regimes are identified to obtain the required extents of radial and axial ne uniformity of 10 cm and 20 cm, respectively, and a steep axial gradient Ln ≈ 10 cm. Based on the desired frequency of the interacting HPM (in the range 3-5 GHz) planned for a particular experimental campaign, the density and spatial density profiles of the plasma can be tailored. The present paper presents an account of the plasma source and characterization of the plasma.

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.

Observation of anomalous side-scattering in laser wakefield accelerators

AbstractHigh-intensity femtosecond laser–plasma interaction experiments were performed to investigate laser–plasma wakefield acceleration in the “bubble” regime. Using a 15 TW laser pulse, the emission of side-scattered radiation was spectrally and spatially resolved and was consequently used to diagnose the evolution of the laser pulse during the acceleration process. Side-scattered emission was observed immediately before wavebreaking at a frequency of ωL + 1.7ωp (where ωL is the laser frequency and ωp is the background plasma frequency). This emission may result from scattering of laser light by large amplitude plasma oscillations generated in the shell of the wakefield “bubble” and which occurs immediately prior to the wavebreaking/injection process. The observed variation of the frequency of scattered light with electron density agrees with theoretical estimates.

Multi-electron beam generation using co-propagating, parallel laser beams

High intensity short pulse laser plasma interaction experiments were performed to investigate laser wakefield acceleration (LWFA) in the ‘bubble’ regime. Using a specially designed phase plate, two high intensity laser focal spots were generated adjacent to each other with a transverse spacing of 70 μm and were focused onto a low density plasma target. We found that this configuration generated two simultaneous relativistic electron beams from LWFA (with low divergence) and that these beams often interact strongly with each other for longer propagation distances in the plasma thus reducing beam quality. In addition, it was observed that the existence of an adjacent laser driven wakefield significantly reduced the self-trapping threshold for injection of electrons. Numerical modeling of these interactions demonstrated similar phenomena and also showed that electron beam properties can be affected through precise control of the phase and polarization of the incident laser beam.

Novel scintillator-based x-ray spectrometer for use on high repetition laser plasma interaction experiments.

The characterisation of x-rays from laser-plasma interactions is of utmost importance as they can be useful for both monitoring electron dynamics and also applications in an industrial capacity. A novel versatile scintillator x-ray spectrometer diagnostic that is capable of single shot measurements of x-rays produced from laser-plasma interactions is presented here. Examples of the design and extraction of the temperature of the spectrum of x-rays produced in an intense laser-solid interaction (479 ± 39 keV) and the critical energy from a betatron source (30 ± 10 keV) are discussed. Finally, a simple optimisation process involving adjusting the scintillator thickness for a particular range of input spectra is demonstrated.

A volume-averaged model of nitrogen–hydrogen plasma chemistry to investigate ammonia production in a plasma-surface-interaction device

Nitrogen impurity seeding is a promising technique for increasing the radiative power dissipation rate in the edge plasma of a fusion device. It will be required in future fusion devices such as ITER to reduce the directed heat flux on the divertor strike-points to within erosion limits. However, chemical reactions between nitrogen and fuel isotopes may complicate tritium control measures by increasing in-vessel retention and impacting the gas-handling plant. To gain insight into the nitrogen–hydrogen plasma chemistry a volume-averaged (global) model is developed and compared with experimental measurements in the MAGnetised Plasma Interaction Experiment plasma device. A set of 702 reactions is compiled and used to model the population dynamics of 51 relevant neutral, ionic, electron, surface and metastable excited state species. Stable equilibrium values are compared to results from an experimental investigation in which a combination of mass spectrometry, Langmuir probe analysis and optical emission spectroscopy is used to determine neutral and positive-ionic trends under the same conditions. The dominant ammonia production mechanism is found to be the Langmuir–Hinshelwood reaction between adsorbed atomic hydrogen and above 25% hydrogen concentration. For lower hydrogen proportions the Eley–Rideal reaction between free atomic hydrogen and is found to dominate. The dominant loss mechanism (for all compositions) is found to be electron impact dissociation into neutral fragments.