We report on the experimental characterization of long-lived, stable Z-pinch plasmas with sustained sheared flow in the FuZE-Q device. Running in a quasi-steady-state mode of operation, FuZE-Q produces approximately 50 repeat plasma pulses, which are diagnosed with fast-framing visible light cameras, collective Thomson scattering (TS), and ion Doppler spectroscopy. This work presents the first profile measurements of the majority ion species velocity in a flowing deuterium Z pinch using collective TS. The time dependence of the flow profile is reconstructed by scanning the acquisition time of the diagnostics. Axial flow velocities of deuterium range from 50 km/s on-axis to nearly 200 km/s at the pinch radius a=1 cm, giving flow differentials △Vz of approximately 100 km/s. Typical electron densities and temperatures in these low-pressure plasmas are 8×1022 m−3 and Te=20 eV, respectively. These flow velocities are typically sustained for more than 15 μs, approximately 7.5 axial flow-through times. Interferometry measurements of the accelerator plasma show an approximately uniform electron density across the annular channel and a steady axial flow in these discharge conditions, implying that the Z pinch is steadily fueled by a stable upstream source. The stability of the Z-pinch plasma is investigated through the lens of visco-resistive and sheared-flow theory. Plasma parameters measured in this quasi-steady-state mode of operation place the Z pinches in the visco-resistive regime, with a characteristic Lundquist number S∼50. The shear flow is consistently super-Alfvénic, with a normalized shear κ≡△Vz/Vth,i, ranging from 1 to 3 that overlaps the lower end of m=0 and m=1 stabilization thresholds reported in kinetic and MHD simulations. This evidence suggests that sheared flow and visco-resistive dissipation jointly support stable operation against both modes.
Particle removal from sensitive surfaces is of great importance in the space and semiconductor industries. To remove particles from surfaces, the force balance between adhesive and repelling forces must be shifted toward a net repelling force. In low-pressure environments, this may be achieved by an electric charge on the particle in combination with an electric field. Particle charging arises from exposure to electric or photon currents, which are conditions prevalent in space environments and Extreme Ultraviolet (EUV)-driven plasmas. Simultaneously, surface charge biasing or a plasma sheath establishes an electric field that exerts a force on the particle. The details of the charging mechanisms remain an active topic of research, and several models have been developed which have been tested experimentally against release probabilities, launch velocities, and inferred charges from force balance analysis. However, due to the poorly constrained nature of adhesive forces, obtaining exact values for particle charge remains difficult. Experimental studies tend to support the Patched Charge Model, establishing it as a promising framework for explaining electrostatic lofting of insulating particles within space and EUV environments. This model is based on the presence of microcavities within the system that accumulate charge locally from the emission of secondary and photoelectrons. Nevertheless, further research is needed to validate these models quantitatively and to develop more predictive tools for controlling particle release from surfaces. This tutorial summarizes charging mechanisms, compares leading models against experimental evidence, and identifies open questions critical to predictive control of electrostatic particle removal in space and EUV environments.
High-density and high-areal-density plasmas are the fundamental prerequisites for fusion ignition in inertial confinement fusion. To generate such plasma conditions via the double-cone ignition (DCI) scheme, a laser facility delivering 160 kJ nanosecond laser pulses is currently under construction in Shanghai. In this work, we propose a compression-stage optimization method for colliding plasmas that integrates two-dimensional radiation hydrodynamics simulations with a genetic algorithm (GA). We show that an isochoric colliding plasma with a peak density of 409 g/cm3 and an areal density of 1.63 g/cm2 can be achieved. We also identify an optimal implosion velocity range of about 251–283 km/s for the plasma jet-collision process for this 160 kJ facility, which can be described by a physically interpretable fit curve. To enable large-scale, high-fidelity predictions of colliding plasma behavior, we develop a neural network ensemble surrogate model trained on over 20 000 simulation datasets derived from the aforementioned GA optimization. This surrogate model takes laser pulse shapes and target geometric parameters as inputs to predict the key plasma parameters, including peak density, areal density, and implosion velocity. The model achieves predictions with an average relative error below 3% and accelerates the optimization process by more than two orders of magnitude compared to direct MULTI-2D simulations. This work establishes a solid foundation for the rapid design and parameter optimization of future DCI experiments.
A spectral theory of quantum charge screening is developed directly from the self-consistent eigenmodes of the multistream Schrödinger–Poisson (SP) system. Unlike susceptibility-based descriptions of screening, the present formulation derives the dielectric response from the coupled SP eigenproblem and yields an exact two-screening-wavenumber factorization. The spectral evolution of these wavenumbers produces three distinct screening regimes, corresponding to two real poles, a critical double pole, and a complex-conjugate pole pair, for which closed-form real-space screening potentials are obtained. Pole coalescence defines the transition between these regimes and yields a universal critical screening profile at the double-pole point. Finite-temperature screening is formulated as an occupation-weighted spectral average of SP momentum eigenstates, establishing a direct connection between the microscopic spectral states and the macroscopic screened potential. Extension to electron–ion plasmas produces a two-branch collective spectrum with separate contributions to the screening response. The resulting static response is related to quantum-hydrodynamic and quantum-kinetic descriptions while retaining explicit spectral pole information. Finally, the formulation is extended to relativistic screening within the square-root Klein–Gordon–Poisson model.
Over the past decade, high-power laser experiments have enabled access to warm dense matter, an intermediate regime between solids and ideal plasmas, characterized by weak ionization, strong coupling, and partial degeneracy. In this regime, the equation of state (EoS) is a key quantity for describing the thermodynamic properties of matter. Although ab initio calculations provide increasingly accurate predictions for the EoS, experimental data that are both accurate and statistically significant remain essential to constrain theoretical models. However, most kilojoule-class laser systems operate at low repetition rates, limiting the amount of available data. The recently commissioned L4n beamline at ELI-Beamlines (Czech Republic) overcomes this limitation by combining kilojoule-scale energy with high-repetition-rate (HRR) operation. Leveraging this capability, we performed the first laser-driven shock compression experiment on hexagonal boron nitride (h-BN) at the L4n beamline, using Velocity Interferometer System for Any Reflector and streak optical pyrometry diagnostics to measure shock velocities. By complementing the existing experimental Hugoniot database for h-BN, this work demonstrates the capability of the HRR L4n beamline for EoS measurements, paving the way for larger experimental datasets in future experiments.
