Abstract: Electrical explosion of wire (EEW) is the first stage of wire array Z-pinch, which has great influence on the following dynamics and the final X-ray emission.In this paper, the physical processes of two-wire Z-pinch was observed by X-ray backlighting.The sub-nanosecond, micrometer-scale X-ray source was generated with X-pinches connected in series with the Zpinch.Experimental results show that electrically exploded wires in vacuum usually develop into "core-corona"structure (highdensity core surrounded by low-density corona plasma).The corona plasma is then driven to the axis by global magnetic field to form a precursor plasma column, adding to the instabilities of the implosion stage.Therefore single wire EEW experiments were carried out to increase the energy deposition of wire core so as to suppress the formation of"core-corona"structure.Experimental results show that the performance of EEW can be improved by higher rising-rate of driving current and positive radial electric field along wire surface.In order to combine the two favorable methods, a flashover switch was inserted between wire-end and cathode.As a result, the specific energy of EEW was increased by 2 times (5.7 eV/atomvs 13 eV/atom) and 3.5 times (3.4 eV/atomvs12 eV/atom) under positive and negative driving current, exceeding the atomization enthalpy of tungsten (8.8 eV/atom) by a factor of 1.4.The laser interferograms show no high-density wire core; in other words, fully vaporized (core-free) wire explosion of bare tungsten wire was achieved.