A Study of the Foil Explosion in Vacuum Using Spectral Streak Camera Diagnostics

The foil explosion in vacuum was studied experimentally using a spectral streak camera. The experiment was performed with Cu, Al, Ni, and Ti foils of thickness 6 μm at a current density rise rate of ∼6 × 105 A/(cm2 ns). For all exploded foils, a plasma corona was formed in the gas desorbed from the foil surface when the voltage across the discharge gap reached the collapse voltage. In the Cu, Al, and Ni foil explosions, the specific deposited energy εdep was sufficient for complete melting but insufficient for vaporization of the foil material. However, the streaked spectra obtained for these foil explosions contained the foil material lines that appeared 80–200 ns after tcoll. The authors hypothesize that these lines appeared as a result of the decaying of the metastable liquid state of the exploded foil metal, which took place at a certain time after the core was shunted. In the Ti foil explosion, the deposited energy was insufficient to melt the metal, the transition to the metastable liquid state did not occur, and the discharge plasma spectrum did not contain lines of the foil material.