Experimental studies of the shunting discharge developing during a foil explosion in vacuum

An experimental study of Al and Ti foil explosions was performed at a current density rise rate of ∼6 × 10⁵ A/(cm²·ns) using a framing camera (3-ns exposure time) and a streak spectral camera. Framing photography has shown that during an Al or a Ti foil explosion, a low-density plasma corona is formed 10-20 ns before a time at which the voltage across the discharge gap reaches the collapse voltage, t = t_coll. Spectral measurements have shown that atomic hydrogen and carbon lines occurred at t = t_coll for both Al and Ti foil explosions. The spectral radiation of the foil material was detected only for Al foil explosions 50-100 ns after t = t_coll. The experimental data and the estimates made in the study indicate that the formation of a plasma corona during a foil explosion occurs in the gas desorbed from the foil surface.