Z-pinch Plasma Research Articles

Confined Z-Pinch Magnetic Nozzle : A New Approach to Space Propulsion System that Utilizes Trapped Charged Particles

This paper provides a theoretical overview of a Z-pinch magnetic nozzle plasma propulsion system designed for Low Earth Orbit (LEO). The system utilizes trapped charged particles from the spacecraft's environment and magnetic confinement to generate thrust, reducing the need for onboard propellants. By employing a magnetic mirror configuration, the plasma is confined and accelerated to create propulsion. The proposed propulsion system is tailored to function in the dynamic space radiation environment of LEO, particularly in polar orbits, accounting for variations in solar activity that affect trapped protons and electrons. The mechanism involves converting magnetic plasma energy into directed kinetic energy, facilitating efficient plasma detachment and momentum transfer to the spacecraft. This study examines the feasibility, design overview, and constraints of implementing this propulsion technology. Key challenges include the variability of the space environment, technological complexities, radiation effects, plasma detachment efficiency, energy requirements, and material durability. Overcoming these challenges through innovative engineering and rigorous testing is essential for successful implementation. The Z-pinch magnetic nozzle plasma propulsion system promises to advance space propulsion technology, offering a more efficient and cost-effective method for satellite operations in LEO. With further research and development, it has the potential to support future satellite missions and space exploration initiatives.

Reconstruction of Z-pinch emission spectra in the wavelength range of less than 10Å using a crystal X-ray spectrograph.

This work is devoted to the reconstruction of Z-pinch plasma emission spectra in the wavelength range of less than 10Å recorded by using a crystal x-ray spectrograph at the Angara 5-1 mega-ampere facility. The spectrograph JA-1 used in experiments has a cylindrical mica crystal with dimensions of 50 × 40mm2 and radius of curvature of 100mm. Registration of spectra is performed on the photographic film UF-4 with dimensions of 30 × 10mm2. To reconstruct the spectra, the previously developed method based on iterative approximation of a true spectrum shape while minimizing a residual between experimental and calculated spectrograms is used. The calculated spectrogram was obtained taking into account the instrumental function of the spectrograph. To define the instrumental function a virtual Monte-Carlo model in the Geant4 toolkit has been developed. This model takes into account the interaction of radiation with the mica crystal using dynamical theory of diffraction. A true spectrum of Z-pinch plasma radiation is reconstructed for a 16mm high load made of two nested cylindrical wire liners. External liner with a diameter of 12mm has 40 Al wires with a diameter of 18 μm. The internal liner with a diameter of 5mm has 4W wires with a diameter of 6 μm. The W wires have a sputtered layer of Rethat is 0.5 μm thick.

Increase in Power of Radiation and Specific Concentration of Energy of Plasma of the High-Current Z-Pinches due to Compression of the Cascade Wire Arrays Interacting via Magnetic Field

Increase in Power of Radiation and Specific Concentration of Energy of Plasma of the High-Current Z-Pinches due to Compression of the Cascade Wire Arrays Interacting via Magnetic Field

Structural and optical performance of NiV/Ti multilayer mirrors for Z-pinch plasma diagnostic at the wavelength region of 350-450 eV.

This Letter reports on investigations of novel, to the best of our knowledge, NiV(Ni93V7)/Ti multilayer mirrors for the operation in the wavelength region of 350-450 eV. Such mirrors are promising optical components for the Z-pinch plasma diagnostic. The NiV/Ti multilayers show superior structural and optical performance compared to conventional Ni/Ti multilayers. Replacing Ni with NiV in multilayers decreases interface widths and enhances the contrast of the refractive index between the absorber and spacer layers. The improvement of interface quality contributes to the enhancement in reflectance. Under the grazing incidence of 13°, a peak reflectivity of 25.1% at 429 eV is achieved for NiV/Ti multilayers, while 17.7% at 427 eV for Ni/Ti.

Impact Initiated Nuclear Pulse Propulsion and Applications

A new iteration of nuclear pulse propulsion (NPP) is investigated in which propulsive nuclear explosions are initiated via hypervelocity impacts. Working entirely without a fission first stage and requiring precise planning of orbits often years in advance, this new iteration, being intrinsically difficult to weaponise, is suited only to peaceful and commercial purposes and so sidesteps the political issues regarding weapons proliferation that have so far prevented use of NPP as originally envisioned (in the form of Project Orion) despite high potential utility and technological maturity demonstrated. Use of Jovian gravity assist/Oberth effect burn to invert a Hohmann transfer orbit into a retrograde ellipse is investigated and suggests that collision velocities with a waiting spacecraft propulsion system could be attained upwards of 70 km/s. Potential schemes for fusion chain reaction initiation are suggested: 1) Inversion of impactor plate by collision with conical annulus into a collapsing cylindrical tamper, 2) Plasma Z-pinch powered by induction of fast moving permanent magnet through a conducting coil, 3) Impact induced x-ray flash powering spherical tamper collapse by ablation as in conventional Teller-Ulam systems, as well as how these may be used in combination. Further avenues for research are suggested. Keywords: Nuclear Pulse Propulsion, Project Orion, Hypervelocity Impact, Spaceflight

Investigation on the scaling of magneto-Rayleigh–Taylor instability to the current rise time of Z-pinch plasmas

Understanding how the magneto-Rayleigh–Taylor instability (MRTI) scales to the current rise time is vital for Z-pinch dynamic hohlraum driven inertial confinement fusion. Wang et al discovered in prior theoretical work that the perturbation amplitude of MRTI before stagnation increases linearly with the current rise time when the implosion velocity of Z-pinch plasma is held constant. In the present work, three types of wire-array experiments with similar implosion dynamics and constant implosion velocity are performed on an 8 MA pulse power generator to investigate the scaling of MRTI to the rise time. It is successfully accomplished for the first time to obtain the similar wire-array Z-pinch implosions in which the current rise time is scaled up to three times on the generator by controlling the trigger time of its 24 modules. Both the experimental results, which include x-ray radiation pulses and x-ray images of imploding plasmas, and the related numerical analysis have shown that the MRTI before stagnation grows linearly with the rise time, as predicted by the theoretical model.

8th Special Issue on Z-PINCH PLASMAS: IEEE Transactions on Plasma Science

8th Special Issue on Z-PINCH PLASMAS: IEEE Transactions on Plasma Science

8th Special Issue on Z-PINCH PLASMAS

8th Special Issue on Z-PINCH PLASMAS

Experimental study of the mechanism of prepulse current on Z-pinch plasma using Faraday rotation diagnosis.

The prepulse current is an effective way to optimize the load structure and improve the implosion quality of the Z-pinch plasma. Investigating the strong coupling between the preconditioned plasma and pulsed magnetic field is essential for the design and improvement of prepulse current. In this study, the mechanism of the prepulse current on the Z-pinch plasma was revealed by determining the two-dimensional magnetic field distribution of preconditioned and nonpreconditioned single-wire Z-pinch plasma with a high-sensitivity Faraday rotation diagnosis. When the wire was nonpreconditioned, the current path was consistent with the plasma boundary. When the wire was preconditioned, the distributions of current and mass density presented good imploding axial uniformity, and the imploding speed of the current shell was higher than that of the mass shell. In addition, the mechanism of the prepulse current suppressing the magneto-Rayleigh-Taylor instability was revealed, which formed a sharp density profile of the imploding plasma and slowed the shock wave driven by the magnetic pressure. This discovery is essential and instructive for the design of preconditioned wire-array Z-pinch experiments.

Improvement of Faraday Rotation and Its Application in Preconditioned Single-Wire Z-Pinch Plasma

Magnetic field measurement in Z-pinch plasma has drawn considerable interest because it is a key problem in the research of dynamic behaviors and the coupling of magnetic field and plasma. In this study, the measurement sensitivity of the rotation angle in Z-pinch plasma was improved by considering the second polarization effect caused by optical elements. The magnetic field distribution of preconditioned single-wire Z-pinch plasma was determined by this method. The Faraday rotation of the 1064-nm probe laser was measured by the beam-splitting polarization method when the plasma acted as a Faraday medium. A second polarization effect on the rotation angle was realized by taking the different transmittances and reflectivities of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s$</tex-math> </inline-formula> components of the beam splitters into account. This configuration doubled the sensitivity of the Faraday rotation measurement. The diagnostic errors produced by the techniques and data processing were quantified. The early stage of the preconditioned imploding plasma was monitored, and the distributions of areal electron density, Faraday rotation, and magnetic field were measured. The experimental results demonstrated that the current distribution can be divided into three parts by two dense shells. The majority of the current was distributed outside the dense shell which existed inside the coronal plasma. In addition, only a small amount of current was distributed in the wire core.

K-shell radiation and bright spot characteristics of high-energy-density Fe-Cr-Ni plasmas influenced by X-pinch load geometry

K-shell radiation is diagnostically advantageous for the study of high-energy-density plasmas. The current work investigates the influence of load geometry on K-shell x-rays in Z-pinch plasmas produced on the 1-MA Zebra generator. Stainless steel (Fe: 69%, Cr: 20%, Ni: 9%) X-pinch wire loads are fielded with an interwire angle of 31° (small-angle) or 62.5° (large-angle), respectively and studied using various x-ray diode, imaging, and spectroscopic diagnostics. The large-angle geometry produced large, individual x-ray-emitting bright spots (> 3 keV) at the wire cross-point averaging areas ≥ 1 mm2, with noteworthy soft x-ray (> 0.75 keV) bursts and radiation yields ≤ 14.6 kJ. The small-angle geometry produced multiple x-ray-emitting bright spots extending the pinch axis with smaller average sizes (≤ 0.5 mm2), consistent with stronger current, increased radiation yield (≥ 15.5 kJ), and notable hard x-ray (> 9 keV) bursts, which peak with largest cumulative bright spot size. Spectroscopic analysis is performed with non-LTE collisional-radiative modeling, indicating a cold, nonthermal plasma region radiating from neutral to Ne-like ions, a hot, thermal region radiating from Fe and Cr He- and Li-like ions, and an intermediate region radiating Kα satellites from Li-like to O-like ions. Modeling of the nonthermal and satellite features imply a fractional hot electron abundance ∼0.1% and ∼0.5% for large- and small-angle geometries, respectively. Relative intensity analysis is performed on Heα and Kα lines, revealing intensity ratios that deviate from the original wire composition. Optical depth estimates allude to optically thick, thermal K-shell plasmas with densities consistent with non-LTE modeling.

On the Possibility of Observing Stimulated De-Excitation of Nuclear Isomer 186mRe in a High-Current Z-Pinch Plasma at the ANGARA-5-1 Setup

On the Possibility of Observing Stimulated De-Excitation of Nuclear Isomer 186mRe in a High-Current Z-Pinch Plasma at the ANGARA-5-1 Setup

Applying Thomson scattering to diagnosing turbulent density and velocity fluctuations in a gas-puff z-pinch

The electron plasma wave feature (EPW) in the time-resolved Thomson scattering spectrum is used to obtain the local electron density in imploding high energy density gas-puff z-pinch plasmas. The optical setup was optimized to allow the relatively weak EPW feature obtained from 1 MA imploding neon gas-puff z-pinches to be seen above the continuum emission as well as the brighter ion acoustic wave (IAW) feature. Using a frequency-doubled Nd:YLF laser (E = 10 J, λ = 526.5 nm, Δt= 2.3 ns, spot size ∼ 250 μm) and two visible light streak cameras, we determined the average electron density in the imploding plasma sheath 40 ns prior to stagnation to be ne=2.5×1018/cm3. At pinch time, it reached ne=1.7×1019/cm3. The electron temperature during implosion measured via the IAW (approximately 50 eV) was four times lower than the implosion electron temperature measured via the EPW (approximately 200 eV), assuming that neither feature is affected by turbulent fluctuations in the plasma. In order for the electron temperatures inferred from the EPW and IAW spectral features to be self-consistent, we find that it is necessary to include velocity fluctuations in the analysis of the IAW feature peaks and corresponding density fluctuation in the peak widths of the EPW feature.

Studying of multi-shell gas-puff Z-pinches using x-ray spectroscopy with spatial resolution

Dynamics and parameters of gas-puff Z-pinch plasmas at stagnation were studied using x-ray spectroscopic diagnostics. In experiments on a 1 MA pulsed power generator, multilayer coaxial loads were made using a triple-nozzle gas-puff valve. High-luminosity spectrographs with spherically bent crystals made it possible to record spectra with high spatial resolution along the pinch axis and to record two-dimensional plasma images in separate spectral lines. Using various combinations of gases in the nozzles and adding small amounts of a gas tracer, the final structure and composition of the compressed plasma were determined. Plasma parameters were estimated by modeling the spectra using the PrismSPECT program, but with the limitation that the spectra were time-integrated, so that spectra from different gases and at different positions may have been emitted at different times.

Instabilities, anomalous heating, and stochastic acceleration of electrons in colliding plasmas

The collision of two expanding plasma clouds is investigated, emphasizing instabilities and electron energization in the plasma mixing layer. This work is not only directly relevant to laboratory experiments with explosively created laser or z-pinch plasmas but may also elucidate naturally occurring plasma collisions in astrophysical or space physics contexts. In the previous publications [Malkov and Sotnikov, Phys. Plasmas 25, 102108 (2018) and Sotnikov et al., Phys. Plasmas 27, 122113 (2020)], we have studied, analytically and numerically, the flow emerging from interpenetrating coronas launched by two parallel wires vaporized in a vacuum chamber. The main foci of the studies have been on the general flow pattern and lower-hybrid and thin-shell instabilities that under certain conditions develop in the collision layer. The present paper centers around the initial phase of the interpenetration of the two plasmas. Two-stream ion–ion instability, efficient electron heating, and stochastic acceleration dominate plasma mixing at this phase. Both the adiabatic (reversible) electron heating and stochastic (irreversible) acceleration and heating mechanisms, powered by unstably driven electric fields, are considered. The irreversibility results from a combination of electron runaway acceleration in the wave electric fields and pitch-angle scattering on ions and neutrals.

Model of Thomson scattering from z-pinch plasma: Application in experimental design for Plasma Focus

The present work develops a model of Thomson scattering (TS) for z-pinch plasmas. Sustained on the phenomenology observed in dynamical-pinch discharges of interest in fusion studies, the plasma dynamics is modeled by axisymmetric bi-Maxwellian velocity distribution with axial and radial drift velocities. Expressions for TS form factor and screening integrals are deduced, and TS spectra are reconstructed. A characteristic temperature of the spectrum is identified, which is determined by a weighted-sum of the axial and radial temperatures, whose coefficients are given by the square of the respective axial and radial components of k→ over the square of the magnitude of k→. It is shown that it is not possible to determine the velocity distribution function of the plasma from just one direction of measurement. Additionally, an experimental setup, which requires two complementary observation directions for a complete determination of the proposed distribution function, is analyzed and its capacity to measure thermal anisotropy and drift velocities is studied for plasma conditions expected in the pinch phase of a plasma focus discharge.

Increasing the Specific Energy Concentration of High-Current Z-Pinch Plasma by Using Transient Compression Modes

Increasing the Specific Energy Concentration of High-Current Z-Pinch Plasma by Using Transient Compression Modes

Thermonuclear neutron emission from a sheared-flow stabilized Z-pinch

The fusion Z-pinch experiment (FuZE) is a sheared-flow stabilized Z-pinch designed to study the effects of flow stabilization on deuterium plasmas with densities and temperatures high enough to drive nuclear fusion reactions. Results from FuZE show high pinch currents and neutron emission durations thousands of times longer than instability growth times. While these results are consistent with thermonuclear neutron emission, energetically resolved neutron measurements are a stronger constraint on the origin of the fusion production. This stems from the strong anisotropy in energy created in beam-target fusion, compared to the relatively isotropic emission in thermonuclear fusion. In dense Z-pinch plasmas, a potential and undesirable cause of beam-target fusion reactions is the presence of fast-growing, “sausage” instabilities. This work introduces a new method for characterizing beam instabilities by recording individual neutron interactions in plastic scintillator detectors positioned at two different angles around the device chamber. Histograms of the pulse-integral spectra from the two locations are compared using detailed Monte Carlo simulations. These models infer the deuteron beam energy based on differences in the measured neutron spectra at the two angles, thereby discriminating beam-target from thermonuclear production. An analysis of neutron emission profiles from FuZE precludes the presence of deuteron beams with energies greater than 4.65 keV with a statistical uncertainty of 4.15 keV and a systematic uncertainty of 0.53 keV. This analysis demonstrates that axial, beam-target fusion reactions are not the dominant source of neutron emission from FuZE. These data are promising for scaling FuZE up to fusion reactor conditions.

Mechanisms for neutron generation in Z-pinches

The studies of neutron emission in Z-pinches are analyzed in this work. The available ideas concerning the nature of neutron emission are contradictory. The terms “fusion mechanism” and “acceleration mechanism” used in publications concerning neutron generation are unable to explain all characteristic properties of Z-pinches observed experimentally. The physical grounds for using these mechanisms are also not fully confirmed. The revision of the existing theoretical approaches makes it possible to reveal new methods for studying Z-pinches, such as the studies of considerable energy release in the Z-pinch plasmas due to the development of MHD instability, as well as the studies of the energy transport during which the most of the magnetic field energy is transported directly to ions, without the participation of the electron component.

Mapping of azimuthal B-fields in Z-pinch plasmas using Z-pinch-driven ion deflectometry

B-field measurements are crucial for the study of high-temperature and high-energy-density plasmas. A successful diagnostic method, ion deflectometry (radiography), is commonly employed to measure MGauss magnetic fields in laser-produced plasmas. It is based on the detection of multi-MeV ions, which are deflected in B-fields and measure their path integral. Until now, protons accelerated via laser–target interactions from a point-like source have been utilized for the study of Z-pinch plasmas. In this paper, we present the results of the first Z-pinch-driven ion deflectometry experiments using MeV deuterium beams accelerated within a hybrid gas-puff Z-pinch plasma on the GIT-12 pulse power generator. In our experimental setup, an inserted fiducial deflectometry grid (D-grid) separates the imploding plasma into two regions of the deuteron source and the studied azimuthal B-fields. The D-grid is backlighted by accelerated ions, and its shadow imprinted into the deuteron beams demonstrates ion deflections. In contrast to the employment of the conventional point-like ion source, in our configuration, the ions are emitted from the extensive and divergent source inside the Z-pinch. Instead of having the point ion source, deflected ions are selected via a point projection by a pinhole camera before their detection. Radial distribution of path-integrated B-fields near the axis (within a 15 mm radius) is obtained by analysis of experimental images (deflectograms). Moreover, we present a 2D topological map of local azimuthal B-fields B(r,z) via numerical retrieval of the experimental deflectogram.