Experimental facts attesting to a two-phase (liquid-metal-vapor) state of t
he matter in the core produced in a high-power discharge through thin wires
are presented. The modern technique of multiframe x-ray shadow photography
has made it possible to observe vapor bubbles in the core and their intera
ction with the shock wave penetrating from the corona. (C) 1999 American In
stitute of Physics. [S0021-3640(99)00305-9].