Summary: A new method for water treatment utilizing radicals produced by a discharge on the surface of a bubble in water is proposed and this method is applied to the de‐color of indigo solution whose original color is blue. The discharge of this method begins at the crossing points of mesh electrode, acrylic resin spacer, and bubbling gas (i.e., called a triple junction where there is a weak point for the electrical breakdown in the electrical power devices). This weak point for the electrical breakdown is used very actively for the surface discharge. The discharge process on the surface of the bubble in water is also observed using a wire‐to‐plane electrode system to fix the observation region of discharge (type‐A reactor). The streamer length estimated by photographs increased linearly with the applied voltage. The energy consumption of discharge for type‐B reactor with a mesh‐to‐plane electrode in oxygen is about 0.09 J when the applied voltage is 20 kV. Production efficiency of the H2O2 concentration of about 27 mg · L−1 in oxygen (46 mg · L−1 in helium) has been obtained when the repetition rate of discharge operated by a pulsed‐power generator, the peak value of applied voltage, and the discharge period are 100 pps (pulsed power generator), 25 kV and 60 min, respectively.

A new method for a water treatment utilizing radicals produced by a discharge inside bubbles in water is proposed. Radicals with short lifetime (atomic oxygen and OH radical) are used effectively for the water purification because those are generated by discharge inside bubbles in water. OH radical production was confirmed by ;a light emission of the discharge using the spectroscopic technique. Dissolved ozone concentration of about 0.3 mg/l was obtained when oxygen was used as a bubbling gas. Decolorization process of' indigo solution by a discharge inside bubbles in water was investigated.

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This study experimentally examined the explosive fragmentation of thin ceramic tubes using pulsed power. A thin ceramic tube was threaded on a thin copper wire, and high voltage was applied to the wire using a pulsed power generator. This melted the wire and the resulting vapor put pressure on the ceramic tube, causing it to fragment. We examined the statistical properties of the fragment mass distribution. The cumulative fragment mass distribution obeyed the double exponential or power law with exponential decay. Both distributions agreed well with the experimental data. Finally, we obtained universal scaling for fragmentation, which is applicable to both impact and explosive fragmentation.

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