The techniques of metallic foil electrically exploding driving hypervelocity flyer to more than 10 km/s for shock wave physics experiments

Ran

et al. 2019

Because of the potential of nano‐TATB as a charge in slapper detonator, the shock initiation threshold of nano‐TATB explosive was studied over short pulse durations (down to 0.017 μs) and high pressure ranges (up to 17 GPa). The pulses were produced by the impact of thin plastic flyer plates, which were accelerated by electrically exploded metal foils. Nano‐TATB powders with a mean particle size of 60 nm were prepared and pressed into cylindrical sample charges with three densities (1.56, 1.64 and 1.74 g/cm3). The flyer impact velocity data versus charging voltages was measured with different flyer thicknesses. Together with the Hugoniot relationships of flyer and samples, the impact pressures and pulse durations were calculated. By using Langlie method, the threshold pressures for shock initiation were determined. In case of the identical flyer plate, the threshold pressure increases with increasing density. In case of the identical explosive density, the threshold pressure increases as the thickness of the flyer decreases (i. e. the pulse duration decreases) except for the highest tested density. These data are represented well by a constant P2τ initiation criterion for the short, high‐pressure pulses and deviate from the P2τ behavior at lower pressures. Finally, nano‐TATB is proved to be a little more sensitive to short‐duration pulses than superfine TATB, but much more sensitive than production grade TATB.

Section: Shock Initiation Threshold Measurementsmentioning

confidence: 99%

Shock Initiation of Nano‐TATB Explosives under Short‐Duration Pulses

Guo

Ran

et al. 2019

“…When high current is passed through metallic foil over a short time using RCL circuits, the state of foil changes from solid to vapor rapidly, partially ionizing the vapor and generating plasma with a high temperature and pressure [13–18]. The plasma generating from the metallic foil electric explosion has many potential applications, particularly as exploding foil initiators (EFIs) to accelerate plastic flyers to impact secondary explosives and initiate detonation [19].…”

Section: Introductionmentioning

confidence: 99%

Improved Exploding Properties of Al/Cu Multilayer Initiators

Guo

et al. 2020

Reactive multilayer films (RMFs) are widely used for energetic initiator applications, the reaction behavior and mechanism are systematically researched for ignition. Recently, Investigation into exploding plasma fields has been carried out based on Al/Ni RMFs. However, few papers are concerned about Al/Cu multilayers for exploding initiators. In this paper, an investigation on the influence of Al/Cu multilayers additives on initiators is described in detail. The Al/Cu multilayers are deposited by magnetron sputtering technology and their structure is confirmed by scanning electron microscopy. The periodic multilayer structure with controlled thickness is visible. The initiator containing Al/Cu multilayers exhibits improved exploding properties with a short exploding time, low matching charging voltages, and high flyer velocities in comparison with Cu layers or Al layer‐based initiators. Meanwhile, the flyer kinetic energy increase of up to 30 mJ indicates that this improvement could not come from the Al−Cu alloying reaction alone. The 1‐D non‐stationary acceleration model confirms that the composite electrical behavior is a factor contributing to improved flyer kinetic energy. The ultra‐high‐speed camera system is employed to observe the flyer launching process accelerated by the exploding plasma. The smaller barrel diameter is beneficial for controlling the shearing process to keep good integrity of the flyer. Overall, the electrical exploding properties of initiators can be enhanced substantially based on Al/Cu multilayers.

“…When high current pulse is passing through metallic foil or wire in short time, the state of foil or wire changes from solid to vapor rapidly, resulting plasma with high temperature and pressure by ionized vapor. The plasma created by metallic foil or wire has many applications in electrical guns (EGs) [1][2][3][4], exploding foil initiator (EFIs) [5][6][7][8][9], exploding wire initiator. The high pressure generated by plasma can accelerate plastic flyers to km/s, which can initiate explosion or investigate impacting performance of materials.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Electrically Heated Exploding Foils in Reactive Al/Ni Multilayer

Sun

Jiang

et al. 2018

The mechanisms of metal phase transition process during electrical explosion are experimentally and theoretically investigated. Past experiments of investigation are single metal foil, such as gold, aluminum, and copper. The characteristics of aluminum‐nickel (Al/Ni) multilayer foil were investigated, which means electrical behavior and energy output. The foil was fabricated by magnetron sputtering based on ceramic substrate, and lithographically patterned into bow‐tie bridge regions. Scanning electron microscopy characterization revealed the layer structure of the Al/Ni multilayer. X‐ray diffraction characterization was employed to ascertain the composition of Al/Ni. The probing of voltage‐current waveforms reveals that Al/Ni multilayer foils exhibit high voltage, short burst time and high absorbing energy in electrically heated in comparison with copper or nickel alone. We also measured the energy output of foils through velocity measurements of encapsulation layers ejected from bridge region by Photonic Doppler velocimetry. We observed flyer velocities from Al/Ni multilayer foil in the 1.6–2.9 km/s range, which is much higher than copper foil. Combined with the 1‐D non‐stationary acceleration model calculation, it is found that the chemical energy and increased electrical absorbing energy contributed to additional kinetic energy in the 40–80 mJ range.