Investigation of the Temporal Evolution of X-Ray Emission From a Copper Vacuum Spark Plasma

The temporal evolution of the X-ray pulses generated by the vacuum spark device was investigated by using five channels of p-i-n diodes, which were mounted at the end-on position along the axis of the electrode system. A time-integrated X-ray spectrometer was used to record the spectral distribution of the X-ray emission. Two types of X-ray emission mechanisms can be identified from our experiments. The first mechanism is due to an electron beam accelerated to bombard at the anode tip, which produces a Cu-K_α-dominated spectrum. The second mechanism of X-ray emission is due to the formation of hot plasma during the vacuum spark discharge. There can be two possible sources of energetic electron beams. One is the transient hollow cathode electron beam that is used to trigger the main discharge of the vacuum spark, and the second one is due to plasma instability. The plasma emission during the vacuum spark discharge may be contaminated by electron beam-target emission toward the end of the pinching action. From discharges with clear evidence of the formation of hot plasma and insignificant Cu-K_α contamination, electron temperatures in the range of 4-8 keV for the copper plasma had been deduced.