Cylindrical Liner Research Articles

Mining experimental magnetized liner inertial fusion data: Trends in stagnation morphology

In magnetized liner inertial fusion (MagLIF), a cylindrical liner filled with fusion fuel is imploded with the goal of producing a one-dimensional plasma column at thermonuclear conditions. However, structures attributed to three-dimensional effects are observed in self-emission x-ray images. Despite this, the impact of many experimental inputs on the column morphology has not been characterized. We demonstrate the use of a linear regression analysis to explore correlations between morphology and a wide variety of experimental inputs across 57 MagLIF experiments. Results indicate the possibility of several unexplored effects. For example, we demonstrate that increasing the initial magnetic field correlates with improved stability. Although intuitively expected, this has never been quantitatively assessed in integrated MagLIF experiments. We also demonstrate that azimuthal drive asymmetries resulting from the geometry of the “current return can” appear to measurably impact the morphology. In conjunction with several counterintuitive null results, we expect the observed correlations will encourage further experimental, theoretical, and simulation-based studies. Finally, we note that the method used in this work is general and may be applied to explore not only correlations between input conditions and morphology but also with other experimentally measured quantities.

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.

Exploring stress and deformation in filament-wound composite pressure vessel liners using PyMAPDL

PyMAPDL, which stands for Python based Mechanical Ansys Parametric Design Language, provides a Pythonic interface to Ansys for automating tasks and managing multiple simulations. The present study focuses on utilizing PyMAPDL to numerically explore the stress and deformation conditions in the domed section of a cylindrical liner, specifically by analyzing ellipsoidal and torispherical dome shapes through the creation of a parametric model in Python. The output suggests a better selection of the dome geometrical parameters. The study extends to filament-wound composite pressure vessels, emphasizing the challenges in determining winding angles and layer thickness variations along the meridian line in dome parts. Cadfil software is used to obtain the thickness and angle variation of the composite layers, and the output data from Cadfil is imported into Ansys ACP as lookup table to generate the composite layer for linear elastic analysis of single composite layer on the liner. The findings suggest that a lower helical angle enhances strength protection in the dome section.

Numerical study of implosion instability mitigation in magnetically driven solid liner dynamic screw pinches

Magnetized liner inertial fusion experiments on the Z accelerator suffer from magneto-Rayleigh–Taylor instabilities (MRTI) that compromise integrity of the imploding cylindrical liner, limiting achievable fusion fuel conditions and ultimately reducing magneto-inertial fusion target performance. Dynamic screw pinches (DSP) provide a method to reduce MRTI in-flight via application of magnetic field line tension to the imploding liner outer surface. In contrast with z-pinches that drive implosions with an azimuthal magnetic field, dynamic screw pinches enforce an additional axial drive magnetic field component, making the overall drive magnetic field helical. As the liner implodes, cumulative MRTI development is reduced by dynamically shifting the orientation of the fastest growing instability modes. Three-dimensional magnetohydrodynamic simulations show that the DSP mechanism effectively stabilizes initially solid cylindrical liner implosions driven by Z-scale current pulses, indicating that MRTI mitigation increases with the ratio of axial to azimuthal drive magnetic field components (i.e., the drive field ratio). We also performed a spectral analysis of the simulated imploding density distributions, extracting wavelength and pitch angle of the simulated MRTI structures to study their dynamics during the implosion. Simulations of liners initially perturbed with drive-field-aligned sinusoidal structures indicate that MRTI mitigation in DSP implosions decreases with perturbation wavelength, once again suggestive of magnetic field line tension effects.

Dinamika, simmetriya i udarno-indutsirovannoe «pylenie» pri kvaziizentropicheskom i izentropicheskom uskorenii tsilindricheskikh laynerov

Two devices intended for copper cylindrical liner gasdynamic acceleration to velocities of 5–7 km/s using the chemicals explosion energy have been investigated. It has been demonstrated that the acceleration of quasi-isentropically and isentropically loaded liners under the conditions of high-level dynamics, symmetry of deposition, and suppression of shock-induced dusting is feasible.

Shape manipulation of a rotating liquid liner imploded by arrays of pneumatic pistons: Experimental and numerical study

Shaping the inner surface of a rotating, imploding liquid metal liner as it compresses a magnetised plasma target is an important aspect of the Magnetised Target Fusion (MTF) scheme pursued by General Fusion. Reduced-order modelling has shown that the liner's inner surface shape can be manipulated during the implosion by spatially varying the amplitude and timing of pressure applied at the liner's outer surface. A sub-scale apparatus was constructed to investigate this concept, using water as the liner material. A simplified axisymmetric model of this apparatus was also developed using OpenFOAM software. Experimental pressure and rotational speed were used as inputs to numerical simulations. Very good agreement between numerical and experimental liner trajectories was obtained for a wide range of implosion parameters. Data analysis confirmed an initially cylindrical inner liner surface can be shaped and the shaped surface remains symmetrical to radial compression ratios of at least 7:1, despite driving the implosion using pneumatic piston arrays. Furthermore, experiments demonstrated suppression of Rayleigh-Taylor instability for shaped implosions by using liner rotation. This is significant, as literature only confirms this suppression for cylindrical implosions. These results increase confidence in simplified numerical modelling as a predictive tool for designing MTF machines.

Dynamics, Symmetry, and Shock-Induced Dusting at Quasi-Isentropic and Isentropic Acceleration of Cylindrical Liners

Dynamics, Symmetry, and Shock-Induced Dusting at Quasi-Isentropic and Isentropic Acceleration of Cylindrical Liners

Review of common hydrogen storage tanks and current manufacturing methods for aluminium alloy tank liners

With the growing concern about climate issues and the urgent need to reduce carbon emissions, hydrogen has attracted increasing attention as a clean and renewable vehicle energy source. However, the storage of flammable hydrogen gas is a major challenge, and it restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper provides a comprehensive review of common on-board hydrogen storage tanks, possible failure mechanisms and typical manufacturing methods as well as their future development trends. There are generally five types of hydrogen tanks according to different materials used, with only Type III (metallic liner wrapped with composite) and Type IV (polymeric liner wrapped with composite) tanks being used for vehicles. The metallic liner of Type III tank is generally made from aluminium alloys and the associated common manufacturing methods such as roll forming, deep drawing and ironing, and backward extrusion are reviewed and compared. In particular, backward extrusion is a method that can produce near net-shape cylindrical liners without the requirement of welding, and its tool designs and the microstructural evolution of aluminium alloys during the process are analysed. With the improvement and innovation on extrusion tool designs, the extrusion force, which is one of the most demanding issues in the process, can be reduced significantly. As a result, larger liners can be produced using currently available equipment at a lower cost.

Liner Development and Characterization for the PHELIX Containment System

Recent experiments conducted on hazardous materials using the Precision High Energy-density Liner Implosion eXperiment (PHELIX) required development of a new containment system for the apparatus. Unlike many containment systems, the PHELIX containment system includes a cylindrical imploding aluminum liner, which is driven via magnetic fields to approximate velocities of 1.4 km/s before impacting a target. The complex design attributes and monolithic geometry of the liner have been driven by both simulations and empirical measurements. The contents of this paper cover the design considerations and requirements for the liner, the efforts made in fabricating the component, and steps taken to verify performance both as the dynamic driver of the experiment and as a containment system component.

Characteristics of “Dust” Fluxes from the Surface of Copper and Lead Liners Exposed to One or Two Successive Shock Waves

Comparative experimental studies of the shock-induced particle ejection (“dusting”) from the free rough (Rz20) surface of copper and lead liners exposed to one or two successive shock waves separated in time by 0.2 μs have been carried out for the first time. This situation usually occurs in cumulative systems for the compression of the plasma by cylindrical or spherical liners shock or quasi-isentropically accelerated by explosion products. Using pulsed X-ray diffraction, laser optical recording, piezoelectric pressure sensors, and heterodyne interferometry, a qualitative picture has been studied and the quantitative characteristics of particle ejection from the free surface such as the velocities of the free surface and the particle flux front and the density (mass) distribution of particle flux in the direction of its motion, which are necessary for more accurate determination of features and the development of more appropriate models of the effect, have been evaluated.

Linear analytical model for magneto-Rayleigh–Taylor and sausage instabilities in a cylindrical liner

Recent experimental and numerical results demonstrates that the interfacial motion of a liner Z-pinch during the early stage of implosion may be controlled by the coupled effects of magneto-Rayleigh–Taylor (MRT), sausage, and kink instabilities. However, previous treatments of sausage instability have not considered the mechanical properties of the liner material. In this paper, we present an analytical model that allows us to study the effects of liner viscosity and elasticity on the coupling effects of MRT and sausage instabilities, and we further assume that the wavelengths are much smaller than the liner thickness by neglecting the feedthrough effect. The dispersion relations are analyzed. It is found that viscosity suppresses short-wavelength perturbations, and longer wavelengths are needed to achieve the fastest growing mode as the viscosity grows. Elasticity also strongly suppresses short-wavelength perturbations and eventually leads to the appearance of a cutoff wavenumber beyond which the interface always remains stable. In particular, the present approach provides the basis for the development of a more general theory that would also include magnetohydrodynamic instabilities and would allow a more accurate description of liner motion.

Effect of Different Types of Denture Cleansers on Hardliner Surface Roughness


 Introduction: Hard liner is a denture relining material which can be used directly at the chairside in brief time. The characteristic of the hardliner is its susceptibility towards porosity which consequently resulting biofilm accumulation and Candida albicans colonization. Thus, there is a need for denture cleaning. Alkaline peroxide is a type of denture cleanser which is widely used, but it could affect the physical properties of hard liner. One of the traditional ingredients that have the potential to be used as an alternative to denture cleanser is cinnamon. Objective: This study aimed to evaluate the effect of different types of denture cleansers on the surface roughness of hard liner. Method: Twelve cylindrical hard liner specimens (15mm x 10mm, ASTM: D-2240 64T) were divided into three groups: group I (immersed in distilled water), group II (immersed in alkaline peroxide) and group III (immersed in 1.5% extract cinnamon). All specimens were soaked for 15 minutes/day for 7 days. Surface roughness was measured using surface roughness tester (Handysurf E-MC-S24B Japan). Data were analysed using one-way ANOVA and post hoc Bonferroni (α=0.05). Results: The highest average of surface roughness was shown on specimens immersed in alkaline peroxide, followed by specimens immersed in 1.5% cinnamon extract and distilled water, respectively. There were a significant difference in surface roughness values in all groups (p<0.05). Conclusion: There is an effect of type of denture cleanser on the surface hardness of hard liner.

Study of the electrothermal and MHD instabilities in exploding cylindrical foil liner

An experimental and numerical study of the plasma instabilities in an electrical exploding cylindrical Al liner is reported. The Al liner 3 mm in diameter and 10 μm in thickness is exploded at the Qin-1 facility (450 ns, 400 kA). Various diagnostics, such as multi-frame laser shadowgraphy, an x-ray framing camera, and an x-ray backlighting system are developed. The different imaging systems are sensitive to plasma of different areal densities based on the comparison between the experiments and simulation, which reveal the dynamics of the exploding liner in more detail. The laser shadow images show the low-density plasma (∼1–2 × 10−4 g cm−2) at the edge of the liner, and both the amplitude and wavelength of the plasma instabilities increase over time, which are considered to be magnetohydrodynamic (MHD) instabilities rather than electrothermal instabilities. During the ablation of the liner, quasi-periodic azimuthally correlated striations are directly observed in extreme ultraviolet (EUV) self-emission images. Meanwhile, the vertical filaments, which are electrothermal instabilities for plasma under the condition of ∂η/∂T < 0, are also observed in EUV self-emission images. The x-ray backlighting images of the exploding liner are obtained by placing an X-pinch load on the current-return path to serve as an x-ray point source (∼1 ns, ∼10 μm). The x-ray backlighting results show the behavior of the high-density plasma (∼1.89 × 10−3 g cm−2), which includes the transition from electrothermal to MHD instabilities. Finally, we realized a 2D MHD simulation of the exploding liner under experimental conditions, which shows good agreement with the results of the experimental perturbation.

Temperature reconstruction of an axisymmetric enclosed reactive flow using simultaneous background oriented schlieren and infrared thermography

The temperature distribution of a premixed methane air flame running at a Reynolds number of 1300 on a circular burner, 12.7 diameter, enclosed in a fused silica cylindrical liner has been experimentally reconstructed using a non-invasive approach combining background oriented schlieren (BOS) and infrared (IR) thermography. BOS is used to characterize both the air ambient to the system, using an existing technique called 3D ray tracing, and the reactive flow inside the enclosure, with a novel modified version of 3D ray tracing. IR thermography is used to characterize the thermal/optical characteristics of the quartz glass enclosure itself, since the information is required as BOS is a line of sight imaging technique. Out of necessity, an approximated species independent relationship is used to calculate flow temperature from refractive index. A simulation is used to show this error is in the range of 5.8%–7%. Additionally, it is found that drastically simplifying the approach by removing the IR thermography system entirely and using the near outer wall air temperature from BOS/3D ray tracing to characterize the internal temperature of the quartz liner itself only causes a 1.5%–3.8% degradation in the accuracy of the reconstructed temperature field. The technique as presented is a relatively inexpensive, experimentally simple approach capable of determining the steady state temperature characteristics of optically accessible axisymmetric reactive flows.

The Effect of Cylindrical Liner Material on the Jet Formation and Penetration Capability of Cylinder-Cone-Shaped Charge.

The jet formation and penetration capacity of cylinder-cone-shaped charges against steel targets were studied using the method of numerical simulation. Cylinder-cone-shaped charge models with five cylindrical liner materials, including nickel, tungsten, tantalum, steel 4340 and copper, were established to investigate the penetration capability and were compared with the classical conical-shaped charge. Moreover, the influence of the connection method of the cylindrical liner and the truncated liner on the jet performance was examined. The results show that the head velocity of the projectile formed by the cylinder-cone-shaped charge with a cylindrical nickel liner was larger than that with other cylindrical liner materials; in addition, it was larger by 50.2% compared with that formed by the classical conical-shaped charge. The penetration depth of the steel target by the cylinder-cone-shaped charge with a cylindrical copper liner was the largest, which could be 51.7% higher than that of a classical conical-shaped charge at a standoff of 2.5 D. For 2.0 D and 2.5 D standoff distances, the penetration depths were increased by 18.4% and 29.5%, respectively, by using the connection method of putting the cylindrical nickel liner on the neck of the truncated liner compared with that of the previous cylinder-cone-shaped charge with a cylindrical nickel liner.

Magnetic implosion of thin aluminum foil liners

Metal liner implosions driven by a pulsed current generator are used in research on inertial confinement fusion, generation of soft x-ray pulses and megagauss magnetic fields. The energy density in the plasma column formed during the liner stagnation is largely determined by the initial radius and the radial convergence of the liner. When the liner implosion time is close to the current rise time, the liner initial radius is proportional to the current rise time. The paper presents the results of experiments on the fast implosion of cylindrical liners on the MIG generator (2 MA, 80 ns) at the Institute of High Current Electronics, Tomsk, Russia. Liners 0.7–1.0 mm in diameter were made from a 1.8 to 2.5 μm thick aluminum foil. A low-density plasma was pre-injected into the liner area. As the Lorentz force sweeps away the pre-injected plasma, the current switches to the liner in 1–3 ns. Then the liner is imploded in 3–7 ns by a current close to the peak generator current. The stagnation radius measured via time-integrated pinhole camera images was found to be not more than 25 µm. Such a radius of the stagnated plasma assumes that the plasma mass density is several times higher than the solid aluminum density.

Studying the Richtmyer–Meshkov instability in convergent geometry under high energy density conditions using the Decel platform

The “Decel” platform at Sandia National Laboratories investigates the Richtmyer–Meshkov instability (RMI) in converging geometry under high energy density conditions [Knapp et al., Phys. Plasmas 27, 092707 (2020)]. In Decel, the Z machine magnetically implodes a cylindrical beryllium liner filled with liquid deuterium, launching a converging shock toward an on-axis beryllium rod machined with sinusoidal perturbations. The passage of the shock deposits vorticity along the Be/D2 interface, causing the perturbations to grow. In this paper, we present platform improvements along with recent experimental results. To improve the stability of the imploding liner to the magneto Rayleigh–Taylor instability, we modified its acceleration history by shortening the Z electrical current pulse. Next, we introduce a “split rod” configuration that allows two axial modes to be fielded simultaneously in different axial locations along the rod, doubling our data per experiment. We then demonstrate that asymmetric slots in the return current structure modify the magnetic drive pressure on the surface of the liner, advancing the evolution on one side of the rod by multiple ns compared to its 180° counterpart. This effectively enables two snapshots of the instability at different stages of evolution per radiograph with small deviations of the cross-sectional profile of the rod from the circular. Using this platform, we acquired RMI data at 272 and 157 μm wavelengths during the single shock stage. Finally, we demonstrate the utility of these data for benchmarking simulations by comparing calculations using ALEGRA MHD and RageRunner.

Investigation of the acoustics of full-scale perforated liners in gas turbine combustors

In conventional gas turbine combustors, the combustion chamber linings are perforated and used for cooling. To cool the liner evenly, bias flows are introduced into the combustor at rates that depend on the operating condition. It has been found that airflow through the liner not only provides cooling but also improves sound absorption and acoustic instability. This experiment reports a unique comprehensive investigation of the influences of single and double-layer cylindrical full-scale gas turbine combustor liner sound absorption properties based on the no flow and non zero bias flows. In particular it is shown that combustor liner porosity (determined by orifice diameter and axial pitch distance) has an important influence on non-zero bias flow in that it increases the peak absorption or dissipation compared with that which occurs in the absence of flow. It is shown that the main influence of bias flow is to increase absorption compared with no flow above 600 Hz and to decrease the transmission loss measured in the absence of flow below 600 Hz but to increase it above 600 Hz. Internal resonance in the combustion liner test section influences both absorption and transmission loss spectra near 600 Hz. To create higher damping, and decrease in acoustic instability during the combustion process, gas turbine combustors require mapping between the inner and outer liner perforation to increase efficiency and lower the hydrocarbon emission. The calculated pressure ratio versus mass flow and combined discharge coefficient effect explain the non-linear distribution of the absorptive and dissipative energy measured at the gas turbine combustor.

Cylindrical metal liner implosion at extremes of pressure and material velocity on an intense pulsed power facility-FP-2.

Highly precise and controllable liner implosions driven by a pulsed power facility have extensive applications in exploration of advanced hydrodynamics at the extremes of pressure and material velocity. In this paper, we describe a new pulsed power facility developed in China named FP-2 (a series of facilities for Fluid Physics investigations-the second generation) for liner implosions. Benefiting from the reliable and stable operation of 48 rail gap switches, the FP-2 facility can steadily transmit a current of 10.5 MA to a dummy load of 10 nH in the case of a charging voltage of ±40kV. The first quarter cycle is 5.5 µs, and the percentage shot-to-shot deviation of the current history is less than 1%. When the aluminum liners of 60mm in height and 0.6mm in thickness are adopted, the maximum velocity of 4.5 and 7.5 km/s has been achieved with the liner diameter of 90 and 60mm, respectively, at the diameter of 10mm. Experimental results show that the percentage shot-to-shot deviation of the liner velocity history is less than 1%. As impact on the target, the maximum of the impact time deviation measured from four perpendicular fiber pins is less than 20ns. Due to the modular design of FP-2, it is convenient for a future upgrade. The confirmation of high-quality implosion on FP-2, such as high repeatability, high reliability, and high symmetry, makes it a bright prospect to explore the advanced hydrodynamic problems at extremes of pressure and material velocity in the future.

Preliminary experimental investigation on small-aspect-ratio cylindrical solid liner implosion using compact pulsed power generator

Small-aspect-ratio cylindrical liner implosion on timescales of the order of hundreds of nanoseconds is important in the fields of high-energy-density physics, implosion dynamics, and inertial confinement fusion. This paper describes the design and development of a cylindrical liner load that has a low inductance and uniform magnetic field and its application in the CQ7 compact pulsed power generator. The dynamic response properties and implosion symmetry of liners with aspect ratios ranging from 5 to 9 are investigated. The experimental results show that the azimuthal symmetry of the liner remains intact, and that a liner with an inner diameter of 6.2 mm and a thickness of 0.4 mm can be accelerated up to 10 km/s before the reflected beam is lost. The demonstrated high performance of the experimental technique used for imploding the liner could be beneficial for studying the implosion and dynamics of materials on compact pulse power generators in the future.