Trailing Mass Research Articles

Experimental study of the dynamics of planar wire array Z-pinch preconditioned by a controlled prepulse current

The influences of the prepulse current on the implosion dynamics of planar wire array were investigated. The time-delay between the prepulse current and the main current (Tdelay) was able to be controlled manually based on the double pulse current generator “Qin-1.” In the precondition stage by the prepulse current, the corona plasma, aluminum vapor, and residual wire cores formed during the explosion of the wires, and ∼40% (±10%) mass of the wires was in a gaseous state at ∼425 ns after the prepulse. After the main pulse was applied, the low-density corona plasma was first imploded and then collided with the aluminum vapor and residual dense cores. Then, the further implosion of the preconditoned wires closely related to their mass distribution, which was determined by the duration of Tdelay. The residual dense wire cores had a significant impact on the implosion when Tdelay was ∼200 ns. When Tdelay increased to ∼> 500 ns, the mass distribution gradually became uniform, and the implosion of the preconditioned wires showed no ablation and no trailing mass.

Researches on preconditioned wire array Z pinches in Xi’an Jiaotong University

The dynamics of wire array Z pinches are greatly affected by the initial state of the wires, which can be preconditioned by a prepulse current. Recent advances in experimental research on preconditioned wire array Z pinches at Xi’an Jiaotong University are presented in this paper. Single-wire explosion experiments were carried out to check the state of the preconditioning and to obtain the current parameters needed for wire gasification. Double-wire explosion experiments were conducted to investigate the temporal evolution of the density distribution of the two gasified wires. Based on the results of these experiments, a double-pulse Z-pinch facility, Qin-1, in which a 10 kA prepulse current was coupled with the 0.8 MA main current was designed and constructed. Wire arrays of different wire materials, including silver and tungsten, can be preconditioned by the prepulse current to a gaseous state. Implosion of the two preconditioned aluminum wires exhibited no ablation and little trailing mass.

Optimization Method for Girder of Wind Turbine Blade

This paper presents a recently developed numerical multidisciplinary optimization method for design of wind turbine blade. The objective was the highest possible blade weight under specified atmospheric conditions, determined by the design giving girder layer and location parameter. Wind turbine blade on box-section beams girder is calculated by ply thickness, main girder and trailing edge. In this study, a realistic 30 m blade from a 1.2 MW wind turbine model of blade girder parameters is established. The optimization evolves a structure which transforms along the length of the blade, changing from a design with spar caps at the maximum thickness and a trailing edge mass to a design with spar caps toward the tip. In addition, the cross-section structural properties and the modal characteristics of a 62 m rotor blade were predicted by the developed beam finite element. In summary, these findings indicate that the conventional structural layout of a wind turbine blade is suboptimal under the static load conditions, suggesting an opportunity to reduce blade weight and cost.

Structural efficiency of a wind turbine blade

Alternative structural layouts for wind turbine blades are investigated with the aim of improving their design, minimizing weight and reducing the cost of wind energy. New concepts were identified using topology optimization techniques on a 45m wind turbine blade. Additionally, non-dimensional structural shape factors were developed for non-symmetric sections under biaxial bending to evaluate structural concepts in terms of ability to maximize stiffness and minimize stress. The topology optimization evolves a structure which transforms along the length of the blade, changing from a design with spar caps at the maximum thickness and a trailing edge mass, to a design with offset spar caps toward the tip. The shape factors indicate that the trailing edge reinforcement and the offset spar cap topology are both more efficient at maximizing stiffness and minimizing stress. In summary, an alternative structural layout for a wind turbine blade has been found and structural shape factors have been developed, which can quantitatively assess the structural efficiency under asymmetric bending.

Suppression of the Ablation Phase in Wire Array Z Pinches Using a Tailored Current Prepulse

A new wire array configuration has been used to create thin shell-like implosions in a cylindrical array. The setup introduces a ~5 kA, ~25 ns current prepulse followed by a ~140 ns current-free interval before the application of the main (~1 MA) current pulse. The prepulse volumetrically heats the wires which expand to ~1 mm diameter leaving no dense wire core and without development of instabilities. The main current pulse then ionizes all the array mass resulting in suppression of the ablation phase, an accelerating implosion, and no trailing mass. Rayleigh-Taylor instability growth in the imploding plasma is inferred to be seeded by μm-scale perturbations on the surface of the wires. The absence of wire cores is found to be the critical factor in altering the implosion dynamics.

Investigation of characteristics of hard x-rays produced during implosions of wire array loads on 1.6 MA Zebra generator

Experimental study of the characteristics of hard x-ray (HXR) emission from multi-planar wire arrays and compact-cylindrical wire arrays (CCWA) plasmas on the 1.6 MA Zebra generator at UNR has been carried out. The characteristics of HXR produced by multi-planar wire arrays such as single, double, and triple planar as well as compact-cylindrical wire arrays made from Al, Cu, brass, Mo, and W were analyzed. Data from spatially resolved time-integrated and spatially integrated time-gated x-ray spectra recorded by LiF spectrometers, x-ray pinhole images, and signals from fast x-ray detectors have been used to study spatial distribution and time history of HXR emission with different loads. The dependence of the HXR yield and power on the wire material, geometry of the load and load mass is observed. Both HXR yield and power are minimum for Al and maximum for W loads. The HXR yield increases with the rise of the atomic number of the material for all loads. The presence of aluminum wires in the load with the main material such as Cu, Mo, or W in combined wire arrays decreases HXR yield. For W plasma, the intensity of cold L-shell spectral lines (1–1.5 Å) correlates with corresponding amplitude of HXR signals which may suggest the evidence of generation of electron beams in plasma. It is found that HXRs are generated from different plasma regions by the interaction of electron-beam with the plasma trailing mass, with the material of anode and due to thermal radiation from plasma bright spots. The theoretical assumption of thermal mechanism of HXR emission predicts the different trends for dependency of HXR power on atomic number and load mass.

Experimental study on K-shell radiation production of aluminum wire array Z-pinch at Qiangguang-I facility

Experimental study of aluminum wire array Z-pinch was conducted on Qiangguang-I facility （1.5 MA, 80 ns） to produce —1.7 keV characteristic X-ray radiation. With fixed wire diameter of 20 μm and annular diameter of 12 mm, K-shell yield up to 0.9 kJ/cm and 1.1 kJ/cm was obtained for wire number N=8 and N=12 arrays, respectively, which are much higher than that for N=16 and N=24 loads. X-ray power waveforms and time-resolved images showed that several implosions occurred due to the existence of trailing mass. During 60%—80% of the whole implosion time，the wire array almost stayed at its initial position rather than running inwards. Main implosion was completed in the next 25—30 ns, with parts of load mass left behind and forming so-called trailing mass. At later time of main implosion, load current was transferred to trailing mass left in outer radii, and caused secondary even tertiary implosion, which also contributed to total K-shell yield. Appearance of trailing mass might be caused by azimuthally correlated axial modulation, consisting of hot spots and gaps on wire plasma column, as well as the development of other inhomogeneities.

Mass-Profile and Instability-Growth Measurements for 300-WireZ-Pinch Implosions Driven by 14–18 MA

We present the first comprehensive study of high wire-number, wire-array Z-pinch dynamics at 14-18 MA using x-ray backlighting and optical shadowgraphy diagnostics. The cylindrical arrays retain slowly expanding, dense wire cores at the initial position up to 60% of the total implosion time. Azimuthally correlated instabilities at the array edge appear during this stage which continue to grow in amplitude and wavelength after the start of bulk motion, resulting in measurable trailing mass that does not arrive on axis before peak x-ray emission.