Streak Spectroscopy of Slapper Detonator Bridge Burst

Exploding Foil Initiator (EFI) or "Slapper" detonators launch a thin flyer at high velocities to shock initiate high explosives. Launch is achieved via high voltage switched across a thin metal bridge causing rapid heating and expansion throughout a phase transition to vapor, plasma. Despite the impressive performance of EFI detonators, the physics of plasma phase transition are poorly understood due to the extreme speeds of typical detonator bridges, raising concerns for model validation. This work aims to probe the phase transitions from metal bridge to plasma using streak spectroscopy. Streak spectroscopy is a diagnostic coupling high time resolution streak cameras with a diffractive grating across the slit, allowing sub-nanosecond resolution of dynamic plasma events. Various bridge materials, flyer materials, and firing voltages are compared, alongside extreme-time (<100ps) resolution measurements of early phase transition spectra. Elemental analysis from absorption bands are noted, and temperature estimates are made of plasma and pre-plasma light emission. Development of this diagnostic furthers efforts in understanding the fundamental physics of highly dynamic, extreme environment events.