Spectroscopy of the plasma formed in the vicinity of the strong shock wave implosion

Converging strong shock wave, generated by underwater electrical explosion of a spherical wire array, was used to generate plasma inside a copper tube (3 mm outer diameter and 1.4 mm inner diameter) placed at the equatorial plane. The diameter of a spherical wire array consisting of 40 wires each of 100 μm diameter, was 30 mm. The explosion of this array by the current pulse of ∼200 kA in amplitude and rise time of ∼1μs supplied by high-current generator charged up to 27 kV, results in an aperiodic discharge when almost all stored energy was deposited to the exploding wires during ∼0.5 μs. The light emission from the plasma formed inside preliminary evacuated tube was guided by an optical fiber placed inside the tube towards the beam splitter and further to a photomultiplier tube and an imaging spectrometer (2400 grooves/mm) coupled with fast framing 4QuikE camera (the spectral resolution at the CCD of the camera was ∼0.14 A/pixel for λ= 6328 A). The Stark broadening of Cu I spectral lines obtained was used for determination of the plasma electron density and the plasma electron temperature was calculated by the ratio of Cu I spectral lines intensity.