Flash radiography of hypersonic flyer plates with a laser-wakefield accelerator

Hypersonic flyer plates are essential to the ignition of modern munitions, typically driven by Exploding Foil Initiators (EFI). In an EFI, a pulsed power plasma with ~kA current and ~µs duration expands to launch a plastic foil, or flyer, initially adhered to a metallic bridge. The flyer reaches several km/s and after traveling across a sub-mm gap, the flyer impacts a high explosive (HE) pellet, initializing the detonation. Hydrodynamic simulations in FLAG show that flyer shape and velocity are important to detonation, yet the former is seldom measured due to stringent radiographic requirements. Here we show that betatron x-rays from a laser-wakefield accelerator meet the requirements for EFI flyer radiography, delivering 3 µm spatial resolution and <100 fs pulse duration. We recover flyer shape as a function of time, while also identifying 3D flyer features salient to initiation.