Effects of wire materials on radiative heat flux and spectral characteristics of a capillary discharge plasma jet

Capillary discharge plasmas have been widely used in many fields. This paper investigates the influence of different explosion wire materials on the radiative heat flux and spectral characteristics. Three kinds of wire (aluminum, copper and nickel) with 0.3 mm diameter were used as initiation wires to produce an electrothermal plasma, with a capacitor charging voltage of 3 kV. A thin-film calorimeter with high response speed was used for the measurement of the radiative heat flux. At the same time, spectral analysis was performed using a spatially resolved spectrometer with an ICCD. Based on the results, the electrical energy transported to the plasma that is calculated from the voltage and current traces follows the order Cu > Al > Ni, while the radiative heat flux follows the order Al > Cu > Ni. The trends can be explained by the secondary combustion (chemical reaction with the air) of Al and the fact that the dissipated energy is smaller than the vaporization energy for Ni but larger for Al and Cu, resulting in a bad performance in jet heat flux due to the incomplete vaporization of Ni wires. For the Cu and Al cases, a four-stage evolution process of the emitted radiation, which describes the emission, absorption and decay processes, can be found from the spectral analysis.