Electrical breakdown study of water under nano second pulsed conditions using optical diagnostic

In this work, an effort has been made to further understand the electrical breakdown properties of deionized water (σ = 0.45 μS/cm). The effect of electrode material by applying hundreds of kilo volts for tens of nano second has been studied. Experiments are performed using Tesla based pulse generator with two different electrode materials i.e. brass and stainless steel (SS). In this, hemispherical shape electrodes (50 mm diameter each) have been used and inter electrode gap is fixed to 3 mm. Experiments are performed with positive applied voltage polarity and all the experiments are performed at room temperature (~26-27°C). Initially, the test chamber is filled with deionized water (ε_r ≈78) and experiments have been performed with pair of brass electrodes. Voltage is increased in steps of tens of kilo volts until the breakdown occur in the water. Later, the same procedure repeated with pair of stainless steel electrodes. In both the cases, experiment performed for several times and average (over fifteen shots) is considered as breakdown voltage. It is observed that, with brass electrodes, breakdown occurred at low voltage compared to stainless steel. The possible explanation has been found from the emission spectra plots as explained in the following sections.