Experimental study of the underwater plasma based on the phased array vibrator system
In this paper, a set of underwater plasma vibroseis system was developed, which included three big systems, i.e. charge system, discharge system and trigger system. At the same time, an experimental platform was set up through tketornix digital oscilloscope, seismic detector and desktop computer for collecting and processing data. On this basis, three working stages (breakdown, detonation and spread) of the underwater plasma were carried out the experimental research and summary. By experiment, the electrical properties of the underwater plasma were investigated under the different electrode materials, different number of electrodes, different voltages, different electrode gap spacing conditions. By using the ORIGIN data analysis software, the plasma channel resistance and the trend of the change of discharge power in time domain were obtained. It laid a foundation for choosing the optimal transducer structure and its material. In addition, the process of pulsed discharge in water was analysed. By comparing and summarizing, it found that the efficiency of corona discharge significantly is higher than that of arc discharge. This research provides references for the design of the plasma source in water.
Discharge in the saline solutions in a vicinity of the threshold voltages
This paper deals with the discharge in saline solution (0.9 % NaCl) in coaxial electrode system at voltages up to several hundred volts. The discharge was powered by bipolar pulsed generator with a pulse repetition rate of 100 kHz and by a generator of negative voltage pulses. At voltages less than a threshold value (less than 300 V)' different types of gas microcavities are formed at the surface of active electrode: the microbubble' the conglomerates of microbubbles (thin gas layers) and a macrobubble with diameter of about 1 mm and less. In a vicinity of threshold voltage the breakdown in the gas cavities occur. For negative polarity at the metal electrode the discharge burns in a form of microsparks of short duration. At positive voltage pulses' the glow-type discharge is sustained in the microcavities.
Spectroscopy of high rate events during active interrogation
Abstract Pulsed accelerators are being used for radiographic inspections in homeland security applications. Adding spectroscopic detection capability enables additional information to be extracted but challenges signal processing hardware. This work compares two approaches to cost-effective digital spectroscopy systems designed to handle these high rate scenarios. In the first system, the signal from a PMT is directly digitized and then deconvolved on a PC using standard techniques. Bypassing the preamplifier, this system can handle high count rates (>10 6  cps) from an LaCl 3 detector with no dead time and an energy resolution of 5% at 1.33 MeV. Spectra acquired from fission product gamma rays between interrogation pulses are shown. At higher rates, this approach is limited by the DAQ transfer rate to the PC. Instead, we tested a fast ADC (125 MSPS) and an FPGA that performed onboard, real-time digital signal processing (DSP). The energy spectrum is generated on the FPGA board during the measurement and transferred later. This system was tested in nuclear resonance fluorescence (NRF) experiments. Resonance peaks from NRF reactions are shown.