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This paper presents the development of an all-in-one probe to simultaneously measure all components of the generalized Ohm's law in reversed-field pinch plasmas and tokamaks. The polyhedral configuration of the Mach probe is achieved through the specific arrangement, angle, and depth of the collimator channel apertures drilled into the surface of a hollow boron nitride cylinder encasing it. This probe includes a central Mach probe to assess the ion velocity field in three dimensions. Initial tests at the RELAX and Madison Symmetric Torus machines have confirmed the probe's effectiveness, revealing an octahedron form similar to a tetrahedron. The probe seems to function correctly and is expected to facilitate the empirical validation of two-fluid equilibria at the periphery of toroidal plasmas. [ABSTRACT FROM AUTHOR]

The results of research on the creation of a powerful source of soft X-ray radiation (SXR, hν > 100 eV) based on the Z-pinch of compact nested arrays are presented. One of the applications of such an SXR source can be radiation ablation of targets made of various substances in experiments on high-energy density physics and extreme states of matter, which are currently being actively carried out worldwide. Experiments are carried out on plasma implosion of combined nested arrays with different ratios of array radii at a discharge current level of up to 3.5 MA at the pulse power facility Angara-5-1. The outer array consisted of fibers of a substance with a low atomic number (polypropylene) and the inner array consisted of a substance with a high atomic number (tungsten). It is shown that in the case of nested arrays of this design, it is possible to obtain a significant (~1.4 times) increase in the peak SXR power compared to single W arrays with the same parameters as the W array in the inner array. At the same time, spectral data obtained using a "flat field" grazing incidence spectrograph demonstrate a significant decrease in the fraction of tungsten ions in the trailing plasma around the pinch of nested arrays. By optimizing the linear mass of the outer array and its radius, powerful and short SXR pulses with amplitude of ~10 TW, energy of ~130 kJ and duration of ~4–5 ns are obtained. This made it possible to increase the incident power density and fluence on the target up to 1.55 TW/cm2 and 17 kJ/cm2, respectively, in experiments on extreme states of matter currently being carried out at the facility. [ABSTRACT FROM AUTHOR]

A theory of the three-wave coupling of triplets of tearing modes in toroidal pinches [i.e., either reversed field pinches (RFPs) or tokamaks] was proposed by R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)]. However, this theory only applies to toroidal pinches with negligible equilibrium plasma pressure gradients. Such a limitation is particularly inappropriate to RFPs. This paper generalizes the analysis of R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)] in order to take the equilibrium pressure gradient into account. However, for the sake of simplicity, a stepped pressure profile, rather than a continuous profile, is employed. In the limit in which the number of steps becomes very large, the results obtained from the generalized theory are presumably equivalent to those that would have been achieved using a continuous pressure profile. The generalized theory is used to investigate the formation of the characteristic toroidally localized pattern of phase-locked m = 1 and m = 0 tearing modes in RFP plasmas that is known as the "slinky" pattern. The incorporation of the equilibrium plasma pressure into the analysis is found to be of crucial importance when determining the properties of the pattern. This is the case because the plasma pressure controls the number of unstable m = 1 and m = 0 tearing modes, and also significantly affects the strength of three-wave coupling, as well as the phase relation between the phase-locked m = 1 and m = 0 modes. [ABSTRACT FROM AUTHOR]

A recently published analysis of current sheets has updated the classic Harris 1D static solution by considering multiple classes of charged particle trajectories in a generalized and dynamic current sheet. It uses a 1D PIC simulation to describe dynamic pinching and bifurcation of the current sheet. These 1D results strongly suggest that properties of the inflowing plasma, including the plasma beta, have an important effect on the equilibrium thickness of the pinched current sheet. Since 1D studies cannot describe magnetic reconnection, the time appears right to carry such 1D studies over to 2D or 3D simulations to explore current sheet thickness effects on reconnection. The Magnetospheric Multiscale Mission (MMS), with its well-resolved multipoint measurements of collisionless plasma and fields, has found that collisionless reconnection is accompanied by non-adiabatic motions of electrons that only occur in magnetic structures with a narrow scale comparable to electron inertial lengths (de). The recent 1D studies suggest that a plasma pinch to such scales may only occur for inflowing magnetized plasmas with relatively low plasma beta. We conclude that a parametric exploration of simulated and observed reconnection inflow conditions, particularly plasma beta, should shed light on the enablement of reconnection in collisionless plasmas. [ABSTRACT FROM AUTHOR]

Newly obtained results on hot and dense deuterium and deuterium-neon plasma compression in a z-pinch electrical discharge configuration are presented. The investigated plasma was generated and compressed using 269 high-current discharges in a medium-sized (dense) plasma focus device. The experimental chamber of the device was filled with deuterium and deuterium-neon gas mixtures under constant total mass/density conditions. Magnetic and electric probes, beryllium neutron activation counter, and high-speed four-frame vacuum ultraviolet/soft x-ray pinhole camera were used to study the plasma dynamics and radiation emission. The results obtained experimentally for the first time confirmed clearly a decrease in the minimum radius of plasma columns with an increase in initial neon fraction. Simultaneously, a decrease in the total neutron emission from deuteron fusion was found. The observed plasma/discharge evolution revealed that the classical description of plasma-focus discharges can be approximately correct up to the moment of maximum compression. Including, existence of quasi-equilibrium plasma compression is probable. It is also possible that the homogeneity of plasma columns during the slow compression phase and maximum compression moment increases with the increase in initial neon fraction. The effect of higher stabilization (repeatability) of discharges was confirmed, for higher initial neon fractions. The dependency of the total neutron emission yield on the parameters describing the full discharge dynamics and the maximum discharge voltage was confirmed. The existence of this type of dependency, for a minimum pinch radius is also possible. In contrast, there was little dependency to the total discharge current parameters measured in the collector area. [ABSTRACT FROM AUTHOR]

Zap Energy is a private fusion energy company developing the sheared-flow-stabilized (SFS) Z-pinch concept for commercial energy production. Spun out from the University of Washington, these experimental and computational efforts have resulted in devices with quasi-steady DD fusion yields above 109 per pulse. These devices support scaling toward energy breakeven on existing devices as well as beyond to commercially relevant engineering fusion gains. This article discusses the strategy behind Zap's development path, which is derived directly from the engineering and scientific elegance of the confinement method. Without need for external confinement or heating technologies, the SFS Z pinch relies on plasma self-organization. This compact magnetic confinement technology could, in turn, provide the basis for a cost-effective fusion power plant, vastly reduced in complexity from its competitors. [ABSTRACT FROM AUTHOR]

When plasma is compressed by magnetic forces, a pinch phenomenon is observed. Pinch plasma has received significant attention as an efficient source of radiation and a way for high-density plasma physics analysis. In this study, a non-ideal magnetohydrodynamics (MHD) model is applied to a smoothed particle hydrodynamics (SPH) framework to analyze pinch plasmas whose local resistivity varies with temperature and pressure. The proposed SPH model incorporates several numerical treatments, such as a correction term to satisfy the ∇·B constraint and some artificial dissipation terms to govern the shock wave. Moreover, it includes the evaluation of a novel SPH discretization for non-ideal MHD terms, including current density calculations. Furthermore, the proposed model is validated with three benchmark cases: (1) Brio and Wu shock tube (ideal MHD), (2) resistive MHD shock simulation, and (3) magnetized Noh Z-pinch problem. The simulation results are compared with the results of some reference Eulerian MHD simulations and analytical solutions. The simulations agree well with the reference data, and the introduced numerical treatments are effective. Finally, X-pinch simulations are performed using the proposed model. The simulations well produce the micro Z-pinch and jet shapes, which are important X-pinch features. Overall, the proposed SPH model has extensive potential for studying the complex pinch plasma phenomena. [ABSTRACT FROM AUTHOR]

The influence of the external axial magnetic field on pinching plasma flows generated by a magnetoplasma compressor (MPC) has been studied using magnetic and electric probes. In the presence of an external magnetic field, temperature measurements show two groups of electrons with different temperatures near the plasma stream core. The external magnetic field leads to a noticeable increase in the electric current in the plasma stream, electron temperature, and the formation of the current-sheet-like structure observed in the MPC for the first time. [ABSTRACT FROM AUTHOR]

This article presents the results of the low inductance vacuum spark plasma diagnostics obtained with the help of a microchannel plate (MCP) detector. Time-resolved pinhole camera images and extreme-ultraviolet (EUV) spectra were obtained for discharge plasma with a framing time in the nanosecond range. It was found that, in the case of an Al anode, discharge plasma undergoes filamentation with subsequent pinching. In the case of a Mo anode, the discharge plasma displays a stratified structure—a system of plasma layers oriented mostly normal to the discharge axis. The difference of the structure can be connected with the process of the erosion of anode at the stage of the discharge current growth. The EUV spectra of discharge plasma at the pinch stage showed the presence of Al ions up to Al VIII (ionization potential 284.6 eV) and Mo ions up to Mo XVII (ionization potential 646 eV). [ABSTRACT FROM AUTHOR]

Arc plasmas have promising applications in many fields, and exploring their properties is of interest. This research paper presents detailed pressure-based finite volume simulations of an argon arc. Simulations of the free-burning argon arc show good agreement with experiment. We observe an interesting phenomenon that an argon arc concentrates intensively in a high-frequency alternating longitudinal magnetic field. This is different from existing constricting mechanisms, as here the arc is pinched through continuous dynamic transitions between shrinking and expansion. The underlying mechanism is that via working together with an arc's motion inertia, the applied high-frequency alternating magnetic field is able to effectively play a "plasma trap" role, which leads the arc plasma to be confined to a narrower space. This finding may provide a new approach to constrict arc plasmas. [ABSTRACT FROM AUTHOR]

Fluctuation measurements reveal the outward electromagnetic energy flux needed to drive the dynamo electromotive force supporting magnetic self-organization in a reversed-field pinch plasma. The radial Poynting flux due to tearing mode fluctuations is measured with an insertable probe during magnetic relaxation. This flux corresponds to transient power levels much larger than the input power and comparable to the global equilibrium magnetic energy transient loss rate. The probe measurements of this flux are roughly as predicted by a simple Poynting's theorem model upon substitution of equilibrium measurement data. [ABSTRACT FROM AUTHOR]

When inductively coupled plasma (ICP) is used as a machining tool, its chemical etching-based processing method has the advantage of no contact stress between the tool and the material, thus without any mechanical damage. In recent years, this issue has been widely concerned in optical fabrication. However, there are many differences between low power ICP jet and conventional ICP jet, one of which is that the former does not easily form a rotation-symmetric removal function due to its obvious pinch effect. In this research, the electromagnetism principle of the plasma pinch effect was analyzed firstly, and the jet shape under the pinch effect was classified. Then, experiment was carried out to investigate the plasma jet shape under the pure Ar and mixed gas of CF4-Ar, and the influence law of the reaction gas on the jet propagation shape was analyzed. Finally, the rotational symmetry of the removal function of plasma jet processing was optimized, and the nozzle design criteria were proposed based on pinch effect. [ABSTRACT FROM AUTHOR]

We present the results of laboratory simulation of jets from young stars at the PF-3 plasma focus facility at the NRC "Kurchatov Institute." The objective of research question was to determine factors making the spatial structure of plasma jets in discharges in gases of different chemical compositions, namely, neon, helium, and helium with admixtures of neon, different. It was found that the plasma flow in the case of pure neon is the most structured: the head of the ejection consisted of numerous clumps, which makes is very similar to clumps in the jets from young stars, the so-called Herbig–Haro objects. The ejection in the case of pure helium was the least structured. However, the shape of the ejection head substantially changes upon admixing merely 1% of neon into helium, revealing a noticeable small-scale structure. Estimates show that these specific features can be related to the difference in the cooling efficiency of the studied gases both in the plasma ejection itself and in the shock wave generated upon jet propagation through the background gas. It is suggested that the main reason for the appearance of inhomogeneities in the plasma blob are different types of instabilities that develop in the presence of efficient radiative cooling, as is the case of the Herbig-Haro objects. In addition, it was established that, in some cases, plasma ejections can consist of several blobs propagating nearly parallel to each other that appear as early as at the stage of plasma pinching. Collision of shock waves generated by each of the blobs leads to the appearance of clumps, which facilitates formation of the lace-like structure of plasma ejection. [ABSTRACT FROM AUTHOR]

This paper investigates wire X-pinch (WXP) evolutions by the Eulerian resistive magneto-hydrodynamic code, STHENO, on 2D/3D geometry. A single-fluid two-temperature model is applied to pinch plasmas in local thermal equilibrium. The equation of state based on the Thomas–Fermi model is used to determine the ionization degree of the plasma. Electron internal energy is determined by the local density, temperature, and ionization potential with the average ion charge state. Lee–More–Desjarlais transport models are employed to obtain the thermal conductivities and resistivity for a non-ideal plasma. The radiation loss rate is calculated by the Bremsstrahlung and recombination emissivity within the ionization balance. The crossing point, which is the central part of the X-pinch, is assumed to be an axisymmetric configuration on a small computational domain in the RZ plane. The 2D simulation demonstrates that the micrometer size plasma column is elongated axially with the onset of the neck cascading structure. The radiation power is calculated and compared with the measured x-ray power from a modular X-pinch device (120-kA in 650-ns) at Seoul National University. The time evolution of the radiation power reproduces the trend of the measured x ray. 3D analyses are performed for the aluminum WXP configurations by varying wire numbers and cross-angles. The relation between the radiation performance and the numbers of wires reveals that the current density, rather than the line density, determines the central pinching condition. In addition, the multiple plasma instabilities (m = 0) near the central regions are found to degrade the radiation performance on the small cross-angle WXP. [ABSTRACT FROM AUTHOR]

In plasma wakefield accelerators, the wave excited in the plasma eventually breaks and leaves behind slowly changing fields and currents that perturb the ion density background. We study this process numerically using the example of a Facility for Advanced aCcelerator Experimental Tests (FACET) experiment where the wave is excited by an electron bunch in the bubble regime in a radially bounded plasma. Four physical effects underlie the dynamics of ions: (1) attraction of ions toward the axis by the fields of the driver and the wave, resulting in formation of a density peak, (2) generation of ion-acoustic solitons following the decay of the density peak, (3) positive plasma charging after wave breaking, leading to acceleration of some ions in the radial direction, and (4) plasma pinching by the current generated during the wave-breaking. The interplay of these effects results in the formation of various radial density profiles, which are difficult to produce in any other way. [ABSTRACT FROM AUTHOR]

Discharge characteristics and dynamic behaviors of a current-carrying line-tied (screw pinch) plasma have been experimentally studied. Besides its compactness, the novelty of this design is to utilize a single plasma source for both arc discharge and beam extraction, providing a plasma current of up to 2 kA with an injection voltage of 1.2 kV. The electron density and temperature of the screw pinch plasma were measured to be ∼1020 m−3 and ∼6 eV, respectively, depending on the operating parameters and magnetic field topology. The estimated Kruskal–Shafranov instability current limit of 1.58 kA was confirmed by high-speed camera measurement. The initial experimental results showed that the strength and topology of the magnetic field played a crucial role in the discharge characteristics and dynamic behaviors of the current-carrying line-tied plasma. [ABSTRACT FROM AUTHOR]

We have investigated the dependence of magnetic field intensity and stimulation time on stacking formation of red blood cells (RBCs) to study blood circulation in human body. The pulse magnetic field with the maximum intensity of 0.27-0.07 T, pulse transition time of 0.102 ms, and pulse intervals of 1 s was applied to the distal end of palm for 5-20 min. The aggregation of RBCs was measured using microscopy. After the magnetic stimulation for 10 min, the fully stacked RBCs were almost separated from each other and moved much faster than those in unstimulated state. The disaggregation was maintained at a decreasing intensity of 0.19 T, and a few cells were stacked at the weak intensity of 0.07 T. In this work, we investigated the degree of RBCs aggregation and activity time by varying the intensity and time of magnetic stimulation to get the optimum condition of pulse magnetic field stimulus. [ABSTRACT FROM AUTHOR]

The effect of magnetic field annealing methods on soft magnetic properties for nanocrystalline (Fe0.5Co0.5)73.5Si13.5B9Nb3Cu1 alloy was investigated. In contrast to nonmagnetic field annealing, the magnetic field annealing can obviously reduce saturation magnetostriction λs and increase effective magnetic anisotropy (K). Furthermore, the initial permeability μi of experimental samples can be enhanced significantly after magnetic field annealing. Different magnetic field annealing methods produced varying degrees of impact on the μi of samples, which is ascribed to the difference of obtained λs and (K). In three magnetic field annealing methods, the magnetic field nanocrystallization can manifest more effective magnetic field effect compared with other two magnetic field annealing methods and achieve more superior magnetic softness, the reason of which was also analyzed. [ABSTRACT FROM AUTHOR]

Magnetic, dielectric, and magnetoelectric properties have been investigated in the polycrystalline Mn4Nb2O9. Under zero magnetic fields, no dielectric anomaly and electric polarization are observed in this compound. When the sample is exposed in magnetic field, finite dielectric peaks and electric polarization are induced, which increase with increasing magnetic field, showing magneto-dielectric and magnetoelectric effects. The origin of magnetoelectric coupling of this compound has been discussed. [ABSTRACT FROM AUTHOR]

Magnetic, dielectric, and magnetoelectric properties have been investigated in the polycrystalline Mn4Nb2O9. Under zero magnetic fields, no dielectric anomaly and electric polarization are observed in this compound. When the sample is exposed in magnetic field, finite dielectric peaks and electric polarization are induced, which increase with increasing magnetic field, showing magneto-dielectric and magnetoelectric effects. The origin of magnetoelectric coupling of this compound has been discussed. [ABSTRACT FROM AUTHOR]

The aim of the research is to examine the dependence of plasma pinch properties and radiation emissions on the atomic number of the operating gas within the dense plasma focus device (NX2) when using hydrogen and argon gases. Simulation was performed with Lee's code on an NX2 dense plasma focus at a constant gas pressure value ( P 0 = 0.5 torr). The results showed that the minimum radius of the plasma focus in the case of the hydrogen plasma pinch was 0.30 cm and in the case of the argon plasma pinch 0.17 cm, and this affected the value of the radiation emission as it was 7.8 × 10 − 6 J and 11 J for the hydrogen and argon pinch, respectively. The energy of the ion beam released by the breakdown of the plasma pinch was found as E n = 23.8 J in the state of hydrogen and E n = 105 J in the state of argon. [ABSTRACT FROM AUTHOR]

Reversed field pinch (RFP) plasmas are subject to tearing instability that creates a broad spectrum of magnetic fluctuations. The dominant fluctuations have poloidal and toroidal mode numbers (m , n) = (1 , 6 − 10) and can grow to 2–3% of the mean magnetic field. Through nonlinear coupling, this growth culminates in a strong reconnection event and broadening of the magnetic spectrum extending to the ion gyroradius scale. Multiple developments occur during the reconnection stage: ions and electrons are energized, magnetic fluctuation amplitudes increase, plasma flow is halted, and the toroidal magnetic flux increases in a sawtooth-like fashion as the RFP dynamo becomes stronger. Magnetic fluctuations are measured in the plasma edge at multiple radial locations from r/a = 0.75 to 0.96 to assess and characterize the magnetic turbulence. The measured spectrum perpendicular to the mean field, S( k ⊥ ), can be fit to a model spectrum consisting of power-law and exponential component with one free parameter that characterizes dissipation. The measured dissipation is much larger than estimated from classical viscous or resistive dissipation, but it is consistent with a flow damping measurement of anomalous viscosity. The measurements show an evolution of the spectrum during which fluctuation power builds up in the smallest wavenumbers and cascades to the larger wavenumber due to the nonlinear coupling between the linear (m, n) = (1, > 6) and the nonlinear (m, n) = (0, 1) tearing modes. [ABSTRACT FROM AUTHOR]

In TAE Technologies' current experimental fusion device, C-2W (also called "Norman"), record breaking, advanced beam-driven field-reversed configuration plasmas are produced and sustained in steady state utilizing variable-energy neutral beams, expander divertors, end-bias electrodes, and an active plasma control system. With a rapid shot-pace and an extensive number of data channels, the amount of data generated necessitates automated signal processing. To this end, a machine learning algorithm consisting of a multi-layered neural network as well as other data processing software has been designed for signal feature identification, allowing for accurate and fast signal classification, anomalous condition detection, and providing for signal pre-processing. With a small set of training data, the neural network can be "bootstrapped" to provide a robust classification system while minimizing human oversight. An example using data from the theta pinch plasma formation pulsed power system is presented. With an overall accuracy of ∼97%—having classified more than 5 × 106 pulsed power signals—the classification scheme is more than sufficient to fine-tune machine set points. However, this technique can be used for near-real-time preprocessing of any plasma physics signal and has wide ranging application in fusion experiments for the varied data produced by plasma diagnostics. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental and theoretical studies of imploding metal-puff Z-pinches. The experiments were carried out on the MIG high-current pulse generator at a current level of about 2 MA and a current rise time of about 100 ns. A plasma gun was used to produce a plasma column with a tailored density profile through which the main electromagnetic pulse of the MIG generator was passed. The experiments have shown that pinches of this type, being compressed, are resistant to dynamic magneto-Rayleigh–Taylor (MRT) instabilities. The experimental results were analyzed using one-dimensional radiation magnetohydrodynamic simulations. It has been shown that in a pinch with a tailored density profile, the formation of a high-temperature plasma at the pinch axis and the generation of x-rays occur at the stagnation stage, i.e. under conditions close to Bennett equilibrium. At this stage, flute-like MRT instabilities develop, causing the pinch to decay. [ABSTRACT FROM AUTHOR]

The characteristics of the electron beams emitted from the hydrogen (H), nitrogen (N), neon (Ne), and argon plasma pinches have been numerically investigated and compared by solving the Vlasov–Maxwell system with the forward semi-Lagrangian approach. Several outcomes have been obtained. For examples, it was found that, in the case of 1-mbar H, the electron current density reached a value of about 1.431 × 109 A⋅m−2 due to turbulence, while it reached 2.554 × 107 A⋅m−2 due to other phenomena. For 2-mbar N, the calculated voltage drops across the m = 0 regions ranged from about 817 kV to 4 MV. Among these gases, Ne had the biggest upstream emission current of about 9.7 kA, while N emitted the least electron beam current of about 4.1 kA. Computations showed that the total charge delivered by each gas beam was of order 0.1 mC. The method of modeling, presented in this article, can be efficiently used to study the dynamics of a plasma pinch. Since the estimated electron beam currents for various gases are in good agreement with the measured ones, the proposed method can be used for designing the plasma focus devices for the electron beam source purpose. [ABSTRACT FROM AUTHOR]

We report a theoretical microscopic model to discuss the barocaloric and magnetocaloric effects in the Gd5Si2Ge2 compound based on the recent experimental data by Yuce et al. [Appl. Phys. Lett. 101, 071906 (2012)]. For this purpose, our model Hamiltonian includes three interactions: Zeeman, magnetoelastic, and exchange interactions, considering the magnetic field dependence of phonons entropy. Using this model, the combined magnetocaloric and barocaloric effects were calculated in Gd5Si2Ge2 compound showing satisfactory agreement with the experimental data. Besides, a high entropy change was predicted for simultaneous changes in the applied magnetic field and pressure (the combined magnetocaloric and barocaloric effects). [ABSTRACT FROM AUTHOR]

An extension of the well established Reverse Monte Carlo (RMC) method for modeling systems under close confinement has been developed. The method overcomes limitations induced by close confinement in systems such as fluids adsorbed in microporous materials. As a test of the method, we investigate a model system of 36Ar adsorbed into two zeolites with significantly different pore sizes: Silicalite-I (a pure silica form of ZSM-5 zeolite, characterized by relatively narrow channels forming a 3D network) at partial and full loadings and siliceous Faujasite (which exhibits relatively wide channels and large cavities). The model systems are simulated using grand canonical Monte Carlo and, in each case, its structure factor is used as input for the proposed method, which shows a rapid convergence and yields an adsorbate microscopic structure in good agreement with that of the model system, even to the level of three body correlations, when these are induced by the confining media. The application to experimental systems is straightforward incorporating factors such as the experimental resolution and appropriate q-sampling, along the lines of previous experiences of RMC modeling of powder diffraction data including Bragg and diffuse scattering. [ABSTRACT FROM AUTHOR]

This article presents a study of neutron emission on the PFZ-200 plasma focus at the Department of physics on FEE CTU in Prague, Czech Republic. In order to achieve the highest and most stable neutron yields, the deuterium working gas pressure and the anode shape were systematically varied. We observed the plasma time to the pinch and the discharge current by the Rogowski coil and neutron emission by the silver activation detector and scintillation time-of-flight detectors. The imploded plasma was visualized using a fast X-ray pinhole camera with a gated microchannel plate detector. The experiment presents the z-pinch discharges with the current maximum above 200 kA and the average neutron yields of ${3 \times 10^{8}}$ neutrons/shot. Measured pinch times were in the range from 1.65 to 1.85 $\mu \text{s}$. The hollow round anode configuration performed the most stable neutron yields with a deviation under 20%. [ABSTRACT FROM AUTHOR]

This work deals with calculation of electron beam generated in a plasma focus device. The Vlasov–Maxwell equations of the charged particles are solved using the forward semi-Lagrangian method. The traces of the electrons are computed. It is shown that electron beams are emitted by strong electric field generated by compression, turbulent, and disruption phenomena in the electrons motion. The energy spectrum of emission shows dependence on pressure and pinch current. [ABSTRACT FROM AUTHOR]

This paper describes the structure of a higher extreme ultraviolet (XUV) emission and plasma density region which surrounds a pinched dense-plasma column. It is interpreted as a toroidal-like plasma formation, which is flowing by a closed current with poloidal and toroidal components upon its surface. This current produces a local magnetic field, which separates the external discharge current from the surface of the dense pinch column. We estimated the values of closed currents as well as magnetic- and plasma-pressures in this column and its surrounding on the basis of the measured distribution of interferometric fringes and intense XUV emission, recorded during the pinch stagnation phase. The considered layer forms the region in which the magnetic energy can be conserved, and during its decay, the acceleration of fast deuterons can take place. [ABSTRACT FROM AUTHOR]

Anomalous resistivity caused by lower hybrid drift instabilities (LHDIs) has been extensively studied in the literature, and has been invoked to explain the rates of magnetic diffusion and plasma profile evolution in the low-density plasma periphery of theta and screw pinch plasmas. This article presents a fully kinetic simulation study of LHDIs with a realistic mass ratio using the particle-in-cell code Chicago over a large range of drift speeds, 0.5 < v d i 2 / v t i 2 < 14.5 , plasma β, β ≥ 2 × 10 − 5 , and temperature ratios, 0.1 < T e / T i < 10. The resistivity quantified from the simulations is compared with the analytic estimates from the literature and a generalized resistivity expression is presented, which can be applied over the entire range of plasma environments that were simulated in this study. This expression uses the amplitude of the LHDI fluctuations resulting from instability saturation by electron resonance broadening rather than plateau formation, current relaxation, or ion trapping. The generalized resistivity expression is appropriate for full-scale fluid simulations that encounter a large range of plasma conditions, and has better agreement with the resistivity quantified from kinetic simulations than previous expressions in the literature, particularly at low plasma β. Anomalous resistivity has also been considered as an explanation of the rapid magnetic field dissipation during magnetic reconnection events at large plasma β. At a large β, the magnetic field fluctuations of LHDIs can dominate the electrostatic fluctuations and this article investigates enhanced collisionality due to the nonlinear magnetic force, δ J × δ B / c. [ABSTRACT FROM AUTHOR]

Fusion–fission hybrid reactors are seen as a possible, mid-term, CO2-free energy source. Starting from the progress in understanding the reversed field pinch plasma confinement, a pilot neutron source with a configuration of R = 4 m and a = 0.8 m and a plasma current of up to 14 mega-ampére (MA) is proposed. A staged experimental approach, with increased complexity and investment, was identified to tackle the existing issues related to scientific and technological aspects and to test the D-T operation at reduced fusion power (P_fus $\approx ~30$ MW, Q $\approx ~0.4$ , continuous pulsed operation). [ABSTRACT FROM AUTHOR]

Radiation-magnetohydrodynamic simulations were able to reproduce features of the plasma structures observed in recent experiments [Ivanov et al., Plasma Phys. Controlled Fusion 59, 085008 (2017)], where a laser was used to ablate plasma in a 3 MG magnetic field. The laser ablates the plasma, and localized structures are formed due to the inhibition of heat flow by the magnetic field. The large magnetic pressures cause the plasma to pinch. In an azimuthal field, a disk-shaped plasma is generated. According to simulations, the disk has electron densities that are underdense to the laser, ranging from 1018 to 1019 cm − 3 , and electron temperatures in the range of 300 to 1000 eV during its evolution, similar to experimental data. [ABSTRACT FROM AUTHOR]

We report the magnetic field sensitivity results on five layer structure given as Metglas/Terfenol-D/ PMN-PZT/Terfenol-D/Metglas, where PMN and PZT correspond to Pb(Mg1/3Nb2/3)O3 and Pb(Zr,Ti)O3, respectively. The piezoelectric constant (d33) of poled PMN-PZT was found to be 1600 pC/N with dielectric constant of 5380 at 1 kHz. The sensitivity measurements were conducted after attaching individual layers in the laminate clearly delineating the effect occurring in the response. The magnetoelectric response for this five layer structure at 1 kHz was found to be 5 V/cm Oe at dc bias field of 1000 Oe under an ac drive of 1 Oe. At 1 kHz frequency, the sensor was able to deterministically measure step changes of 500 nT while at 10 Hz we can clearly identify the sensitivity of 1 μT. These results are very promising for the cheap room-temperature magnetic field sensing technology. [ABSTRACT FROM AUTHOR]

In expansion cooling phase of pinched nitrogen plasma generated by fast capillary discharge, it might be possible to realize lasing a Blamer α recombination SXRL, which requires a rapid cooling of nonequilibrium plasma. It is effective to decrease the discharge current rapidly in reducing the additional heating caused by the joule heating and the magnetic compression of plasma as quickly as possible. The shaping of discharge current waveform was demonstrated with a transmission line and its effect on expanding plasma dynamics were investigated through magnetohydrodynamics (MHD) calculation, and validity of the MHD calculation in the expansion phase was shown using the discharge photographs taken by using a high speed camera. As a result, strong radiation from the H-like N ion at the maximum pinch, which is in the current decay phase of the triangular current with peak amplitude of over 70 kA and pulse width of 60 ns, has been confirmed in x-ray photodiode signals at wavelength of less than 2.5 nm, to clarify the existence of the Lyman series and continuum of the H-like N ion. Without additional heating by the discharge current after the generation of the fully stripped nitrogen ions, it might be possible to generate the population inversion between the principal quantum number n=2 and 3. [ABSTRACT FROM AUTHOR]

The Lee model code is used to compute neon soft x-ray yield Ysxr for the NX2 plasma focus as a function of pressure. Comparison with measured Ysxr shows reasonable agreement in the Ysxr versus pressure curve, the absolute maximum yield as well as the optimum pressure. This gives confidence that the code gives a good representation of the neon plasma focus in terms of gross properties including speeds and trajectories and soft x-ray yields, despite its lack of modeling localized regions of higher densities and temperatures. Computed current curves versus pressure are presented and discussed particularly in terms of the dynamic resistance of the axial phase. Computed gross properties of the plasma focus including peak discharge current Ipeak, pinch current Ipinch, minimum pinch radius rmin, plasma density at the middle duration of pinch npinch, and plasma temperature at middle duration of pinch Tpinch are presented and the trends in variation of these are discussed to explain the peaking of Ysxr at optimum pressure. [ABSTRACT FROM AUTHOR]

Experimental conditions are presented for the formation of a Z pinch from ablated wall material in a high current, medium diameter capillary discharge without an initial filling gas. A hollow cathode geometry is used and electron beams, initiated by a laser spark, form a transient metallic plasma in the hollow cathode volume. The laser spark plasma initiates the preionization phase, whose conditions are essential for generating a stable Z pinch during the main conduction phase. During the preionizing phase wall plasma is ablated. The main discharge is derived from a small pulsed power generator, whose rate of rise of current may be varied, at current of 120 kA for 120 ns. The capillary has an internal diameter of 5 mm and length of 6 cm. From time, spatial and energy resolution of the axial soft x-ray emission, the optimum conditions of plasma formation are found to depend on the preionizing electron beams, current and the rate of rise of main discharge current applied. The temperature is obtained from soft x-ray spectra, and attains a maximum value of 80 eV. The relevance of these results in soft x-ray lasing capillary discharges is discussed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The implosion of combined loads consisting of an outer wire (fiber) array and inner cylindrical target was studied experimentally at the Angara-5-1 facility (3.5 MA, 100 ns) at currents of up to 3.5 MA. The experiments were carried out with 12- and 20-mm-diameter outer arrays made of 15-μm-diameter aluminum wires, composite arrays made of aluminum wires and 25-μm-diameter kapron fibers, and arrays made of kapron fibers with a 1-μm-thick aluminum coating. The number of wires varied from 10 to 40. The targets were made of agar-agar or low-density deuterated polyethylene. The parameters of the Z-pinch plasma were determined using the Angara-5-1 diagnostic complex, which included optical streak cameras, X-ray frame cameras, X-ray detectors, X-ray pinhole cameras, neutron detectors, and a mica-crystal X-ray spectrograph. It is established that the plasma compression dynamics and the formation of local plasma structures generating neutrons depend on the load configuration: the array diameter, the number of wires (fibers), and the diameter and density of the target. The most efficient compression and the highest plasma parameters (the compression ratio and plasma temperature), as well as the highest neutron yield, were achieved in experiments with 12-mm-diameter aluminum wire arrays inside which a 1-mm-diameter deuterated target with a mass density of 0.3 g/cm3 was installed As a result of collision of the bulk of the array mass with the inner target, a compact pinch with a diameter of ≈0.5 mm forms. The pinch formation is accompanied by the generation of a soft X-ray pulse. The development of MHD instabilities in the pinch plasma results in the formation of multiple hot spots (HSs) on the pinch axis with a typical size of 200–300 μm and an electron temperature of 0.4–0.7 keV. The HS formation is accompanied by emission of neutrons with a mean energy of 2.7 ± 0.2 MeV. The maximum neutron yield achieved in these experiments was 2.6 × 1010 neutrons/shot. [ABSTRACT FROM AUTHOR]

A soft x-ray streak camera system based on the conversion of fast scintillator has been developed to diagnose 10-MA Z-pinch implosions on the Primary Test Stand facility. The streak camera system is used to measure the continuous time history of the 0.2–10 keV x-ray emission from pinch plasmas and proved to be free from the intense electromagnetic environment effectively during the discharge of the Primary Test Stand. The spatial resolution of the streak camera system is estimated to be less than 120 μm, and its temporal resolution has been calibrated to be about 1 ns. X-ray streak images of aluminum wire-array plasmas have been obtained successfully in experiments, and the nonuniformity of the x-ray emission along the axial direction has been observed. [ABSTRACT FROM AUTHOR]

Ar divergent gas-puff ${Z}$ -pinch discharge with reversed polarity was performed. Spectroscopic and spatial properties of K-shell and L-shell radiations emitted from highly ionized Ar ions were investigated. It was confirmed that L-shell radiation was spreading in the axial direction, whereas K-shell radiation was emitted from a small spot. The spot size of K-shell radiation was measured, and the diameter of the spot was $34 \pm 9~\mu \text{m}$. Small creatures were observed using the K-shell radiation emitted from the spot. Repetitive and intense point radiation source with limited spectrum was realized by the divergent gas-puff ${Z}$ -pinch. [ABSTRACT FROM AUTHOR]

Electron density fluctuation has been measured based on the collect forward scattering method using a single-chord microwave interferometer system on the Keda Torus eXperiment (KTX) reversed field pinch. The interferometer system is a heterodyne one with two terahertz solid-state sources with frequency around 650 GHz, and the transmitted beam and forward scattering beam are received simultaneously by a Schottky planar diode mixer with sensitivity about 500 mV/mW. Constrained by the beamwidth and geometry limitation, the measurable wave vector range is $k_{w}\le 5 {\mathrm {cm}}^{-1}$ with a resolution $\Delta k\approx 2.07\,{\mathrm {cm}}^{-1}$. MHD activities are detected via this forward scattering technique. The results are consistent with other diagnostics, such as the chord averaged electron density, the edge magnetic probe, and high-speed charge-coupled device (CCD) camera. [ABSTRACT FROM AUTHOR]

Abstract We report on the pulsed magnetic field actuation of single crystalline Ni-Mn-Ga cuboid micropillars with dimensions of 40 × 45 × 120 μm3, created by focused ion beam milling followed by electrochemical etching. Based on the experimental and modelled results, we differentiate between type I and type II twin boundary motion in the micropillar, which display about an order difference in actuation velocities. Magnetically-induced reorientation of a micropillar was obtained in less than 5 μs by type II twin boundary motion. Our results suggest the possibility of fabrication of magnetic shape memory microdevices with working frequencies up to 100 kHz. Graphical Abstract [ABSTRACT FROM AUTHOR]

A simple and effective classification method to distinguish type-I and type-III edge-localized modes (ELMs) in an experimental advanced superconducting tokamak is introduced and some key parameters affecting the type-I and type-III ELMy H-modes are analyzed. The results indicate that the heating power and the edge safety factor q95 have strong correlations with the appearance of type-I and type-III ELMs. By using the high-speed visible-light charge-coupled device camera system, the dynamic characteristics of ELM filaments are studied and the features of type-I and type-III ELM filaments have been compared. The radial outward velocity for type-I ELMy filaments can be up to 1.5–3.5 km/s while for type-III ELMs one is about 0.5–2 km/s. In the process of type-I and type-III ELMy filaments outward propagation, the width of filament decreases gradually, while the velocity of filament increases. In addition, during an ELM event, it can be observed that the earlier the burst of an ELM filament, the higher the radial velocity it will have. [ABSTRACT FROM AUTHOR]

Deals with a study which analyzed particle trajectories from a simulation of relativistic electron pinch diode. Analytic models of pinch diode; Ways to minimize the effect of numerical fluctuations; Analysis of electron trajectories; Deflection by magnetic and radial electric fields.

Presents a study which examined the prospects of a dynamic z-pinch as alternative source of intense extreme ultraviolet radiation. Development of a small discharge apparatus; Experimental methods; Results and discussion.

Investigates pinch formation in fiber pinch experiments in the lower terawatt regime. Periods in which the experiments were performed; Diagnostics; Results.

Focuses on a study which investigated the influence of the anode and cathode geometrical structure on the stability of the z-pinch and the x-ray yield of the pinch at the z-pinch facility at the University of California in Irvine. Description of the modification of the nozzle and anode of the pinch facility; Details of the experiment; Results and discussion; Effect of double gas puff z pinch.