Accelerating flyer plates via underwater wire explosions to create shock compression

Studying material properties at extreme pressures and densities is essential to the advancement of astrophysics and other research fields. Such extreme conditions are created through shock compression, produced by generating shock waves inside a material. This is typically achieved by accelerating a high-velocity flyer plate via chemical explosions, gas guns or magnetic gradients.

But these methods require expensive facilities, and the energy transfer efficiency for compression is generally only about 2%. Maler et al. showed how electrical wire explosions underwater can be used to accelerate flyer plates for an energy transfer efficiency rate that is an order of magnitude higher.

The experimental setup consisted of an aluminum chamber 100 millimeters in diameter. An array of 40 copper wires was placed between electrodes inside the chamber filled with deionized water, along with a cylindrical aluminum flyer plate. A high-current generator produced the underwater explosion.

The researchers studied flyer-plate acceleration with and without thin acrylic glass plates, located between the flyer plate and wire array. They measured the target velocity and calculated the kinetic energy after 10 microseconds.

In experiments with the acrylic glass, which served as temporary barriers, they found that the energy transfer efficiency was about 20% due to the water density accumulation behind the acrylic sheets.

“When the shock wave and water flow fracture the acrylic plate, removing the temporary barrier, the increased pressure behind it generates a stronger shock wave, leading to higher compression of the target material, but without a significant jump in temperature,” author Daniel Maler said.

The method could be used to better understand the dynamics of warm dense matter, which likely make up the core of giant planets such as Jupiter.

Source: “Efficient target acceleration using underwater electrical explosion of wire array,” by D. Maler, A. Rososhek, S. Efimov, A. Virozub, and Ya. E. Krasik, Journal of Applied Physics (2020). The article can be accessed at https://doi.org/10.1063/5.0034435 .