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Recently, plasma activated water (PAW) has drawn huge attention because it is considered to be useful for biomedical and agricultural applications. Because the PAW contains several nitrogen compounds such as nitrate, it can be used as a natural fertilizer. In this article, we report the comparative test results of PAW production by combining nonthermal plasma, thermal plasma, and hybrid methods. As a thermal plasma source, gas-jet assisted pulsed discharge (GAPD) under water was used, and the coaxial cylindrical dielectric barrier discharge (DBD) was adopted as the nonthermal plasma source. The difference in the radical generation rate between the two methods was identified. Some synergy effects in the formation of nitrate ion by the hybrid system were also confirmed. It is considered that the surface discharge through the air channel in GAPD formed by the gas jet stabilized more rapidly by increasing the conductivity of water by relatively high power DBD. This combination can greatly improve the energy efficiency of nitric acid production at relatively low input energies. [ABSTRACT FROM AUTHOR]

Graphite rods of 2 mm in diameter and 50 mm in length have been exploded in water to produce graphite nanoparticles with electrical energy from 5.5 to 44 kJ. The products of the explosion consisted of some fragments in a few micrometer size and many nanoparticles in diameter of several tens of nanometer. It is considered that local pressure and temperature were enough to convert the graphite rod to liquid droplets, which turned to the spherical shape of graphite nanoparticles by rapid cooling. The paramagnetism of the graphite nanopowder prepared in water has been revealed by vibrating sample magnetometer results. The degree of magnetization was proportional to the discharge energy and its maximum reached up to 0.56 emu/g. [ABSTRACT FROM PUBLISHER]

After preliminary tests using a small 25 mm-caliber electromagnetic launcher, a larger mid-caliber launcher has been designed and fabricated. The launcher has a rectangular bore of 40 mm $\times $ 50 mm, where the rails are separated by 50 mm from each other and are 5.6 m long. To deliver an electrical current to the launcher, a new 4.8-MJ pulsed power supply (PPS) consisting of eight 600-kJ segments has been constructed. The 600-kJ segment is a basic building block of PPS operated independently. It contains a controller, a charger, a safety circuit, and six 100-kJ unit modules. Each unit module in the segment is composed of a 100 kJ capacitor bank, a thyristor switch, a crowbar diode, and a pulse-forming inductor. The modules in a segment are charged to the same voltage, but they are designed to have different triggering times to make a flexible shape of current waveform. The electrical parameters of the PPS were determined through the discharges of the unit modules and those of the rails were measured by launch experiments or short circuit tests at the ends of the rails. Launch experiments have been done using several current waveforms. The current of 1 MA in a few milliseconds accelerated the armatures of several hundred grams in mass to velocities near 2 km/s. In this paper, the design and basic performance of the constructed PPS and the electromagnetic launcher are presented. [ABSTRACT FROM PUBLISHER]

A 2.4-MJ capacitive pulsed power system (PPS) for a railgun was fabricated, installed, and tested. It consists of four independent 600-kJ segments. Each segment contains six 100-kJ capacitor bank modules, a capacitor charger, a circuit for charge and dump, a relay box, and a segment controller. The 100-kJ unit module is composed of a metalized film capacitor, semiconductor switches, and an inductor. It was designed for a safe operation within 10 kV and 75 kA. All the modules in a segment are charged with the same voltage, but the trigger times of each module are individually controllable. With the 2.4-MJ PPS and a medium caliber railgun, discharge experiments in the breech-shorted condition and launch experiments using aluminum armatures were conducted. With the results, we modified the electrical circuit parameters of the PPS from the initial designed values. The circuit simulation using the modified parameters showed good agreement with the experiment data. [ABSTRACT FROM PUBLISHER]