We consider weakly ionized plasma where frequent elastic scattering of electrons on neutrals changes the individual acts and the rate of electron–electron collisions significantly. In this case, the kinetics of electron thermalization is very different from that in fully ionized plasma. The colliding electrons do not move freely. They, instead, diffuse because of fast scattering on neutrals. We demonstrate

The transverse instability induced transparency can be detrimental in the laser-driven radiation pressure acceleration (RPA) of ions. It is the primary source of increase in the energy spread of the accelerated ion beam. In this paper, through two-dimensional particle-in-cell simulations, we demonstrate the suppression of transparency and significant improvement in the energy spread of the accelerated

The dense plasma focus is a plasma discharge powered by a capacitor bank. Standard diagnostics include the measurement of the time derivative of the current through and the voltage across its connections with the capacitor bank. Interpretation of this diagnostic data often involves some assumptions regarding the representation of the dense plasma focus as a time varying inductance. One of the characteristic

Magnetic flux ropes have been successfully created with plasma guns in the newly commissioned PHAse Space MApping (PHASMA) experiment. The flux ropes exhibit the expected m = 1 kink instability. The observed threshold current for the onset of this kink instability is half of the Kruskal–Shafranov current limit, consistent with predictions for the non-line tied boundary condition of PHASMA. The helicity

When a magnetic field is forced to evolve on a time scale τev, as by footpoint motions driving the solar corona or non-axisymmetric instabilities in tokamaks, the magnetic field lines undergo large-scale changes in topology on a time scale approximately an order of magnitude longer than τev. But the physics that allows such changes operates on a time scale eight or more orders of magnitude slower.

Thresholds for the absolute stimulated Raman scattering (SRS) and two-plasma decay (TPD) instabilities driven by multiple broadband laser beams are evaluated using 3D simulations at conditions relevant to inertial confinement fusion experiments. Multibeam TPD and SRS backscatter are found to be easier to mitigate with bandwidth than the corresponding single-beam instabilities. A relative bandwidth

Separatrices of magnetic reconnection host intense perpendicular Hall electric fields. The fields are produced by the decoupling of the ion and electron components and are associated with the in-plane electrostatic potential drop between the inflow and outflow regions. The width of these structures is typically less than the ion inertial length, which is small enough to demagnetize ions as they cross

We study the phenomena of radiative-driven shock waves using a semi-analytic model based on self-similar solutions of the radiative hydrodynamic problem. The relation between the Hohlraum drive temperature T Rad and the resulting ablative shock DS is a well-known method for the estimation of the drive temperature. However, the various studies yield different scaling relations between T Rad and DS based

The turbulence of magnetically confined plasmas usually presents high-density pulses with short duration known as bursts. In the Texas Helimak, it is possible to suppress bursts in a broader region by applying a negative electrostatic bias. However, an almost unchanged burst rate persists in a region far from the location where bias is applied. We investigate the turbulence transition that occurs from

Reduction of flow compressibility with the corresponding ideally invariant helicities, universally for various fluid models of neutral and ionized gases, can be argued statistically and associated with the geometrical scenario in the Taylor–Proudman theorem and its analogs. A “chiral base flow/field,” rooted in the generic intrinsic local structure, as well as an “equivalence principle,” is explained

The basic physics of drift-wave turbulence and zonal flows has long been studied within the framework of the wave-kinetic theory. Recently, this framework has been reexamined from first principles, which has led to more accurate yet still tractable “improved” wave-kinetic equations. In particular, these equations reveal an important effect of the zonal-flow “curvature” (the second radial derivative

The low-to-high mode or L-H transition in tokamaks involves a sudden reduction in the edge turbulence level and a decrease in the edge plasma transport. The mechanism for the L-H transition is widely believed to be associated with changes in the poloidally averaged poloidal turbulence velocity. Using a gas puff imaging (GPI) diagnostic, the poloidally averaged poloidal turbulence velocity ⟨Vpol⟩pol

Within integrated tokamak plasma modeling, turbulent transport codes are typically the computational bottleneck limiting their routine use outside of post-discharge analysis. Neural network (NN) surrogates have been used to accelerate these calculations while retaining the desired accuracy of the physics-based models. This paper extends a previous NN model, known as QLKNN-hyper-10D, by incorporating

The complex nonlinear dynamical phenomenon described as turbulence, is known to have a great impact on fluids, magnetohydrodynamic systems, and on plasmas. This paper reviews selected topics on turbulence in these systems, emphasizing the multiscale space-time properties of the turbulence cascade as it transfers energy from large scale reservoirs, through the inertial range, finally dissipating at

Experimental data, simulations, and theory are presented for a JET tokamak thermal quench. The emphasis is on the timescale of the bulk plasma thermal energy loss. The simulations suggest that the thermal energy loss is caused by a resistive wall tearing mode, and experimental data are consistent with this conclusion. The timescale of the thermal quench is the inverse of the mode growth rate.

Collisionless particle dynamics in a helical magnetic mirror is investigated by methods of the Hamilton dynamics. In the limit of small Larmor radius, the Hamiltonian is fully integrable and particle trajectories can be divided into three types, differing in the direction of the drift velocity. The structure of the trajectories of resonant particles and the width of the resonance are studied. The influence

A non-relativistic multi-fluid plasma axisymmetric equilibrium model [A. Ishida et al., “Three-fluid axisymmetric equilibrium model and application to spherical torus plasmas sustained by RF electron heating,” Plasma Fusion Res. 10, 1403084 (2015)] was developed recently to account for the presence of an energetic electron fluid in addition to thermal electron and ion fluids. The equilibrium formulation

A Bayesian framework has been used to improve the quality of inferred plasma parameter profiles. An integrated data analysis allows for coherent combinations of different diagnostics, and Gaussian process regression provides a reliable regularization process and systematic uncertainty estimation. In this paper, we propose a new profile inference framework that utilizes our prior knowledge about plasma

A simple zero-dimensional model for a tokamak disruption is used to evaluate the effect of radial runaway losses on the avalanche multiplication of a runaway primary seed during the current quench phase of a fast disruptive event as well as during its termination phase. Analytical expressions for the resulting runaway current, the energy of the runaway beam, and the runaway energy distribution function

A description of an edge-biasing experiment conducted on the spherical compact toroid plasma injector is presented with results. The insertion of a disk-shaped molybdenum electrode (probe), biased at up to +100 V, into the edge of the Compact Torus (CT), resulted in up to 1.2 kA radial current being drawn from the probe to the wall. Core electron temperature, as measured with a Thomson-scattering diagnostic

Resonances of high energy particles in magnetic confinement devices due to electromagnetic instabilities can strongly modify the distribution, leading to a reduction in fusion power and even discharge termination and particle loss to the device walls through avalanche. The existence of a mode particle resonance depends on properties of the equilibrium, particle trajectories, and perturbation mode harmonic

The first continuum gyrokinetic calculations of electrostatic ion scale turbulence are presented for the case of a diverted tokamak geometry. The simulation model solves the long-wavelength limit of the full-F gyrokinetic equation for ion species coupled to the quasi-neutrality equation for electrostatic potential variations, where a fluid model is used for an electron response. In order to facilitate

Near peak compression, inertial confinement fusion implosions release both deuterium–tritium (DT) fusion gamma rays and neutron induced gamma rays from carbon from the areal density of the remaining ablator shell. The gamma reaction history diagnostic makes a time resolved measurement of both. Across many recent implosions, the carbon gamma ray peak arrives systematically 11 ± 10 ps later compared

Volume ignition, in which fuel is usually surrounded by pushers made from high-Z materials, is an approach to inertial confinement fusion. High-Z pushers have high albedos, which means that they can re-radiate most of the radiation coming from the hot fuel. Hence, it is beneficial to realize ignition at lower temperatures. We develop a theoretical model comprising a set of coupled equations to model

Convergent high-energy-density (HED) experimental platforms are used to study matter under some of the most extreme conditions that can be produced on Earth, comparable to the interior of stars. There are many challenges in using these systems for fundamental measurements currently being addressed by new analysis methods, such as the combination of a reduced physics model and Bayesian inference, allowing

We report results of direct-drive laser imprint experiments measuring velocity perturbation profiles of shock waves produced by the Nike krypton fluoride laser. A new high-resolution two-dimensional velocimeter system was successfully implemented on the Nike laser facility and used for sensitive optical measurements of the velocity perturbations. Planar polystyrene targets with and without a thin high-Z

High energy gain in inertial fusion schemes requires the propagation of a thermonuclear burn wave from hot to cold fuel. We consider the problem of burn propagation when a magnetic field is orthogonal to the burn wave. Using an extended-MHD model with a magnetized α energy transport equation, we find that the magnetic field can reduce the rate of burn propagation by suppressing electron thermal conduction

Macroscopic simulations of dense plasmas rely on detailed microscopic information that can be computationally expensive and is difficult to verify experimentally. In this work, we delineate the accuracy boundary between microscale simulation methods by comparing Kohn–Sham density functional theory molecular dynamics (KS-MD) and radial pair potential molecular dynamics (RPP-MD) for a range of elements

Recently, heat transport was investigated using a directly driven beryllium sphere [Farmer et al., Phys. Plasmas 27, 082701 (2020)]. Models that overly restrict heat transport were rejected. This paper extends work to directly driven gold spheres where radiation loss is more important. Here, gold coated spheres are directly driven at the OMEGA laser facility at intensities of 5 × 10 14   W / cm 2.

X-ray Thomson scattering (XRTS) is a powerful diagnostic technique that involves an x-ray source interacting with a dense plasma sample, resulting in a spectrum of elastically and inelastically scattered x-rays. Depending on the plasma conditions, one can measure a range of parameters from the resulting spectrum, including plasma temperature, electron density, and ionization state. To achieve sensitivity

Double shell capsule implosions are an alternative approach to achieving alpha heating on the National Ignition Facility. Current machining techniques construct the outer shell as two hemispheres that are glued together, and the deuterium and tritium (DT) liquid inside the inner shell will be injected by a fill tube. These features introduce asymmetries and jetting that may disrupt the confinement

A hybrid early time x-ray drive followed by conventional laser direct drive obtained by utilizing a thin high-Z overcoat on plastic ablator targets has proven to be very effective at reducing laser imprint in experiments driven by the Nike krypton-fluoride laser. An inherent low level laser prepulse from that laser system heated and expanded the coating prior to the main pulse. Here, we report on results

To achieve ignition with high gain in inertial confinement fusion, precise symmetry control is one of the key issues to guarantee the PdV work converting into the inner energy efficiently and maximize the pressure of the hot spot. The shaped pulse is used to maintain a low adiabat of the shell. A longer pulse and more compressible shell require more rigorous symmetry control, especially the driven

This paper presents two-dimensional hydrodynamic simulations of implosion of a water sample, which is enclosed in a cylindrical shell of tungsten that is driven by an intense uranium beam. The considered beam parameters match the characteristics of the beam which will be delivered by the heavy ion synchrotron, SIS100, at the Facility for Antiprotons and Ion Research (FAIR). An experimental scheme based

The effect of the shell mass on the hot spot pressure is investigated numerically for the Inertial Confinement Fusion (ICF) implosion. By using a simplified one-dimensional spherical model, it is found that there exists a critical shell mass that determines whether the hot spot can reach the maximum pressure. When the shell mass is larger than the critical mass, the hot spot pressure reaches the maximum

Fast magnetic reconnection plays a fundamental role in driving explosive dynamics and heating in the solar chromosphere. The reconnection time scale of traditional models is shortened at the onset of the coalescence instability, which forms a turbulent reconnecting current sheet through plasmoid interaction. In this work, we aim to investigate the role of partial ionization in the development of fast

We studied and demonstrated the emission of THz waves by the beating of two CW-laser beams in an axially modulated plasma in the presence of a static magnetic field (applied transversely to the direction of propagation of lasers) from two-dimensional particle-in-cell simulation. The ponderomotive-force-induced nonlinear current drives THz radiation with frequency close to the beat frequency (Δω = ω1

The advanced radiographic capability located at the National Ignition Facility (NIF) uses high intensity, short pulse lasers to create bright photon sources for diagnosing high energy density experiments. There are radiographic needs for a multi-frame time-resolved MeV gamma diagnostic for experiments on the NIF with sub-nanosecond resolution. A series of experiments demonstrated measurements of MeV

A virtual cathode oscillator (vircator), which can generate a high-power microwave, has been widely studied over the last four decades. This paper describes the dependence of microwaves and electron beams generated in a reflex triode vircator on the electrode shape and material. The reflex triode vircator is driven by a Marx generator with an output voltage of 200 kV and a stored energy of 240 J. Experiments

Two color laser pulses are used to form an air plasma and generate broadband infrared radiation suitable as a seed for backward Raman amplification of CO2 laser pulses. Broadband radiation in the atmospheric window from 8 to 14 μm is observed. The infrared radiation is characterized using a long wavelength grating spectrometer specially designed to accept an ionizing laser filament at its input plane

Laser–plasma acceleration at kilohertz repetition rates has recently been shown to work in two different regimes with pulse lengths of either 30 fs or 3.5 fs. We now report on a systematic study in which a large range of pulse durations and plasma densities were investigated through continuous tuning of the laser spectral bandwidth. Indeed, two laser–plasma accelerator (LPA) processes can be distinguished

An annular cathode is generally fixed on a cylindrical cathode holder in a magnetically insulated coaxial foilless diode. Electrons emitted from cathode plasmas or the cathode holder may easily move backward under the action of the quasi-static electric field and axial magnetic field, leading to backward current loss, which will seriously reduce the efficiency of high power microwave sources, especially

Spatially and temporally resolved visible absorption spectroscopy is performed on sodium D-lines present as surface contaminants on an expanded dense aluminum plasma plume. An 80-ns FWHM, intense, relativistic electron beam deposits 5.4 J into a 100-μm-thick Al foil, which isochorically heats and subsequently hydrodynamically expands the material through the warm dense matter state and into a classical-like

During a long-term discharge of a Hall thruster, local overheating on the anode surface occurs and its location shifts randomly. The asymmetrical supply of anode potential is thought to be the cause. To investigate their relationship, a bias voltage is applied on one piece of a quartered anode to realize the asymmetrical supply of anode potential. Variations of both the current and temperature of each

This paper considers the application of the triple Langmuir probe method to investigate the local plasma parameters of the radio frequency (RF) discharge that is placed in the applied magnetostatic field. The main criteria applicability for such a method for experimental diagnostics of RF plasma parameters is presented. As an example, this paper presents experimental results that were obtained using

A harmonic oscillator model is proposed to study the intensification of microwave radiation of an electrically small antenna when surrounded by a subwavelength plasma discharge. This model describes the oscillations of free electrons in a spherical plasma when it is excited by an incident electromagnetic wave. It shows that at resonance, these charge oscillations lead to a significant volume current

Helicon plasma sources currently represent an active field of research in the domain of low-temperature plasmas due to several interesting characteristics for in-space propulsion applications. This work reports direct comparison of krypton and xenon plasma properties through spatially resolved measurements performed in the near-field plume of a sub-kilowatt-class 13.56 MHz helicon source. The set of

An atmospheric argon discharge plasma was induced by a high-power microwave beam using a 28 GHz gyrotron and investigated at pressures of 40 kPa–100 kPa and Gaussian peak intensities of 0.115 GW/m2 (0.204 MV/cm) and 0.168 GW/m2 (0.246 MV/cm). According to high-speed imaging results, the propagation velocity of the discharge front increased with the backpressure to maintain a range of 600 m/s–1000 m/s

The cathode-sheath region of a discharge in atmospheric pressure air with a flat copper cathode is numerically investigated by using a simple fluid model that takes into account non-local ionization. The effects of the cathode temperature are considered. Results are obtained in a wide current density range of 1–102 A/cm2, which spans from normal glow discharge, through abnormal glow discharge, up to

This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting

The super-Alfvénic acceleration of an extremely high beta plasmoid due to a magnetic pressure gradient is evidenced in translation experiments involving the field-reversed configuration (FRC) in the FRC amplification via the translation-collisional merging (FAT-CM) device. Inside the FRC, there is a population of unmagnetized particles that forms a volume with extremely high beta. Formed using the

We have made an investigation on the doubly excited 1Po resonance states of helium atom in quantum plasmas using correlated exponential wave functions within the framework of the stabilization method. The effect of quantum plasma has been incorporated by using an exponential-cosine-screened Coulomb potential. A total of nine resonances for 1Po states below the He+(2s 2S) thresholds are calculated,

In collision-poor space plasmas, protons with an excess of kinetic energy or temperature in the direction perpendicular to the background magnetic field can excite the electromagnetic ion cyclotron (EMIC) instability. This instability is expected to be highly sensitive to suprathermal protons, which enhance the high-energy tails of the observed velocity distributions and are well reproduced by the

Collisional rate calculations which account for relative multifluid streaming were implemented in a collisional-radiative model that is applicable for a generalized set of atomic elements. The rate modifications for multifluid streaming were derived in two recent studies for electron-impact excitation, de-excitation, ionization, and recombination [H. P. Le and J.-L. Cambier, Phys. Plasmas 22, 093512

The nonlinear evolution of the ion–ion streaming instability (IISI) is studied using numerical techniques novel to this problem that afford direct insight into the evolution of the particle distributions of each species. During the linear phase of the instability, we demonstrate quantitative agreement with linear kinetic theory. Subsequently, the electrostatic field generated by the IISI causes ring-like

Linear stability theory for extended magnetohydrodynamics (XMHD), which incorporates the Hall and electron-inertia effects into MHD, is developed by introducing Lagrangian displacement fields for ions and electrons. For simplicity, incompressible and dissipationless XMHD is assumed in this work, since the present consideration is greatly inspired by an analogy with incompressible ideal fluid. The governing

Radio frequency (RF) breakdown can result in pulse shortening and severely limits the performance of the relativistic backward wave oscillator (RBWO). In this study, segmented slow-wave structure (SWS) rings, which can be observed directly using a scanning electron microscope without any post-processing, are used to study the breakdown in a RBWO. After undergoing high-power microwave experiments, the

Here, we report on modifications to the electron energy distribution function during X-mode microwave injection in argon and helium helicon plasmas. No electron heating is observed in argon helicon plasmas. Significant electron heating, Δ T e ∼ 1 eV, is observed in helium plasmas. The heating is spatially localized to the upper hybrid resonance layer. Previously absent helium ion emission lines, from

In this paper, we investigate the resonant electron–plasmon interactions in a drifting electron gas of arbitrary degeneracy. The kinetic-corrected quantum hydrodynamic model is transformed into the effective Schrödinger–Poisson model, and the driven coupled pseudoforce system is obtained via separation of variables from the appropriately linearized system. It is noted that in the low phase–speed kinetic

We present a study of the expansion of an ultracold neutral plasma (UCNP) with an initial density distribution that decays exponentially in space, created by photoionizing atoms shortly after their release from a quadrupole (or biconic cusp) magnetic trap. A characteristic ion acoustic timescale is evident in the evolution of the plasma size and velocity, indicating that the dynamics are reasonably