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The design, construction, and testing of high frequency, high voltage pulse power supply are reported. The purpose of the power supply is to generate dielectric barrier discharges for industrial applications. The power supply is compact and has the advantage of low cost, over current protection, and convenient control for voltage and frequency selection. The power supply can generate high voltage pulses of up to 45 kV at the repetitive frequency range of 1 kHz-50 kHz with 1.2 kW input power. The output current of the power supply is limited to 500 mA. The pulse rise time and fall time are less than 2 μs and the pulse width is 2 μs. The power supply is short circuit proof and can withstand variable plasma load conditions. The power supply mainly consists of a half bridge series resonant converter to charge an intermediate capacitor, which discharges through a step-up transformer at high frequency to generate high voltage pulses. Semiconductor switches and amorphous cores are used for power modulation at higher frequencies. The power supply is tested with quartz tube dielectric barrier discharge load and worked stably. The design details and the performance of the power supply on no load and dielectric barrier discharge load are presented. [ABSTRACT FROM AUTHOR]

High energy capacitor bank is used for primary electrical energy storage in pulsed power drivers. The capacitors used in these pulsed power drivers have low inductance, low internal resistance, and less dc life, so it has to be charged rapidly and immediately discharged into the load. A series resonant converter based 45 kV compact power supply is designed and developed for rapid charging of the capacitor bank with constant charging current up to 150 mA. It is short circuit proof, and zero current switching technique is used to commute the semiconductor switch. A high frequency resonant inverter switching at 10 kHz makes the overall size small and reduces the switching losses. The output current of the power supply is limited by constant on-time and variable frequency switching control technique. The power supply is tested by charging the 45 kV/1.67 µF and 15 kV/356 µF capacitor banks. It has charged the capacitor bank up to rated voltage with maximum charging current of 150 mA and the average charging rate of 3.4 kJ/s. The output current of the power supply is limited by reducing the switching frequency at 5 kHz, 3.3 kHz, and 1.7 kHz and tested with 45 kV/1.67 µF capacitor bank. The protection circuit is included in the power supply for over current, under voltage, and over temperature. The design details and the experimental testing results of the power supply for resonant current, output current, and voltage traces of the power supply with capacitive, resistive, and short circuited load are presented and discussed. [ABSTRACT FROM AUTHOR]

For long-life operation, easy to mount and compact in size penning type ion sources are widely used in different fields of research such as neutron generators, material research, and surface etching. One penning type ion source has been developed in our laboratory. Applying high voltage of 2 kV between two oppositely biased electrodes and using permanent magnet of 500 gauss magnetic field along the axis, we had produced the glow discharge in the plasma region. The performance of this source was investigated using nitrogen gas. Deuterium ions were produced and extracted on the basis of chosen electrodes and the angle of extraction. Using a single aperture plasma electrode, the beam was extracted along the axial direction. The geometry of plasma electrode is an important factor for the efficient extraction of the ions from the plasma ion source. The extracted ion current depends upon the shape of the plasma meniscus. A concave shaped plasma meniscus produces converged ion beam. The convergence of extracted ions is related to the extraction electrode angle. The greater the angle, the more the beam converges. We had studied experimentally this effect with a compact size penning ion source. The detailed comparison among the different extraction geometry and different electrode angle are discussed in this paper. [ABSTRACT FROM AUTHOR]

Observes X pinches made from various metal wires that were exploded in vacuum by a capacitor bank. Neutron emission from exploding wire/fiber, containing deuterium; Experimental details; Results; Discussion.

The results of a very-compact (Marx generator-cum-inductor confined into 0.20 m cylindrical diameter and 0.75 m length) and light-weight (< 15 kg) pulsed-power generator are being presented in the paper. The load voltage at 10.5 Ω is measured 125 kV (150 ns full width at half maximum FWHM) with 1.5 GW peak-power. The use of single-optimized-exploding-copper-wire along with the use of air for all the switches of the generator (closing switches of Marx generator used as primary energy source and opening switch of exploding wire) make device very attractive. Marx generator shape itself provides the desired inductance for the inductive storage. [ABSTRACT FROM AUTHOR]

We have already reported the low-voltage operation of a plasma focus describing the operation of plasma focus at 4.2 kV which proposes possibility of making a repetitive system using compact driving source. Another recent article describes that the same capacitor-bank can drive the plasma focus for a measured ∼5 × 104 neutrons per shot at 5 kV and 59 kA current. In the present work, repetitive operation of the capacitor-bank of plasma focus is done and that too is being reported at a very high repetition rate of 50 Hz using very simple scheme of charging and triggering the bank. The bank is continuously discharged to burst duration of 20 s in this configuration admeasuring a thousand shots. [ABSTRACT FROM AUTHOR]

We know in an under-damped L-C-R series circuit, current follows a damped sinusoidal waveform. But if a number of sinusoidal waveforms of decreasing time period, generated in an L-C-R circuit, be combined in first quarter cycle of time period, then a quasi-exponential nature of output current waveform can be achieved. In an L-C-R series circuit, quasi-exponential current waveform shows a rising current derivative and thereby finds many applications in pulsed power. Here, we have described design and experiment details of a 9-loop quasi-exponential waveform generator. In that, design details of magnetic switches have also been described. In the experiment, output current of 26 kA has been achieved. It has been shown that how well the experimentally obtained output current profile matches with the numerically computed output. [ABSTRACT FROM AUTHOR]

The article presents a research on a series loaded resonant converter-based power supply intended for pulsed power applications. It cites that an impulse power supply has been created, simulated, and tested to manage the primary of a high-frequency transformer. The research introduces a novel topological circuit of stable voltage source power converter utilizing the latest insulated gate bipolar transistors (IGBTs) (IRG4PH40PUD). It also indicates that a maximum power of 10 kilowatts decrease in this initial version to 5 kilowatts is the needed charging voltage of impulse power supply.

A 200 kJ pulsed power system (PPS) has been built up to drive pulsed plasma devices. This PPS consists of two 100 kJ capacitor bank modules, each comprising of five capacitors of each 178~\mu \textF , a discharge switch, and a pulse-shaping unit. When both the banks are charged simultaneously to −15 kV using full charging technique, it delivers a peak current 100 kA at the load (damping resistor and pulse-shaping inductor). Later on, a plasma system will be attached at the load which will also have an inductive and resistive effect. A fiber-optic triggering unit controls both the modules and there exists a flexibility of sometimes operating a single module only, besides there are provisions for further up gradation of the PPS to a targeted 600 kJ. Prior to this development, PSpice simulation was carried out to estimate the parameters of the circuit components to achieve the required wave pulse with precision. Using these parameters, a design of the PPS was made keeping into account about the critical issues involved and the ratings of the components, some of which were fabricated in house. This paper basically includes the criticality surrounding the operation of a high-energy long-pulse PPS under negative operating voltage. [ABSTRACT FROM AUTHOR]

The use of aluminium alloys has increased significantly in industries, so this trend has spurred the development of new joining methods for aluminium alloys. A 40 kJ Magnetic Pulse Welding (MPW) system was designed and developed to carry out the Electro-Magnetic (EM) expansion welding of aluminium 6061 alloy tube. The system consists of 15 kV, 356 μF capacitor bank, spark-gap switch and an EM expansion welding coil. The short circuit frequency of the MPW system is 20 kHz; it had delivered the maximum current of 166 kA, magnetic field of 31 T in the 1.5 μH coil and has achieved the maximum impact velocity of 660 m/s for 65 mm diameter, 1.5 mm thick tube. The EM expansion coils were designed and fabricated using circular and rectangular cross section copper wires. For the same discharge current, coils fabricated with rectangular cross section copper wires were found mechanically stronger and developed about 1.3 times higher fields than the coils fabricated of circular cross section copper wires. Simulation and experimental studies have been done to analyse the effect of factors like system frequency, peak current, magnetic field profile and geometry of work piece on the quality of weld obtained in the process. Expansion welding of Al 6061 tube of 25 mm to 65 mm diameter, 1.5 mm and 2 mm thickness and stand-off distance 2 mm to 3 mm was carried out. A stand-off distance of 2.5 mm was found to be the optimal value for a 65 mm diameter, 1.5 mm tube at a discharge current of 166 kA, which resulted into a good and strong metallurgical bond between the work pieces at the interface. Thicker tubes require comparatively more energy to deform significantly and to get accelerated to required velocity in comparison to thinner tubes. The characterization of the weld joint was done by drop, pull out, peel-off tests and microscopic image of the weld joint was also analysed to confirm the wavy morphology of the weld interface. [ABSTRACT FROM AUTHOR]

The results of characterization experiments carried out on a newly developed dense plasma focus device based intense pulsed neutron source with efficient and compact pulsed power system are reported. Its high current sealed pseudospark switch based low inductance capacitor bank with maximum stored energy of ~10 kJ is segregated into four modules of ~2.5 kJ each and it cumulatively delivers peak current in the range of 400 kA-600 kA (corresponding to charging voltage range of 14 kV-18 kV) in a quarter time period of ~2 μs. The neutron yield performance of this device has been optimized by discretely varying deuterium filling gas pressure in the range of 6 mbar-11 mbar at ~17 kV/550 kA discharge. At ~7 kJ/8.5 mbar operation, the average neutron yield has been measured to be in the order of ~4 × 109 neutrons/pulse which is the highest ever reported neutron yield from a plasma focus device with the same stored energy. The average forward to radial anisotropy in neutron yield is found to be ~2. The entire system is contained on a moveable trolley having dimensions 1.5 m × 1 m × 0.7 m and its operation and control (up to the distance of 25 m) are facilitated through optically isolated handheld remote console. The overall compactness of this system provides minimum proximity to small as well as large samples for irradiation. The major intended application objective of this high neutron yield dense plasma focus device development is to explore the feasibility of active neutron interrogation experiments by utilization of intense pulsed neutron sources. [ABSTRACT FROM AUTHOR]

The performance of railgap switch critically relies upon multichannel breakdown between the extended electrodes (rails) in order to ensure distributed current transfer along electrode length and to minimize the switch inductance. The initiation of several simultaneous arc channels along the switch length depends on the gap triggering technique and on the rate at which the electric field changes within the gap. This paper presents design, construction, and output characteristics of a coaxial cable based three-stage transmission line transformer (TLT) that is capable of initiating multichannel breakdown in a high voltage, low inductance railgap switch. In each stage three identical lengths of URM67 coaxial cables have been used in parallel and they have been wounded in separate cassettes to enhance the isolation of the output of transformer from the input. The cascaded output impedance of TLT is ~50 Ω. Along with multi-channel formation over the complete length of electrode rails, significant reduction in jitter (≤2 ns) and conduction delay (≤60 ns) has been observed by the realization of large amplitude (~80 kV), high dV/dt (~6 kV/ns) pulse produced by the indigenously developed TLT based trigger generator. The superior performance of TLT over conventional pulse transformer for railgap triggering application has been compared and demonstrated experimentally. [ABSTRACT FROM AUTHOR]

Characterization results of high-power microwave radiation, from an axial vircator driven by pulsed electron beam accelerator AMBICA-600 are reported in this paper. We present a study on variation in pulsed microwave power output and dominant frequency by discretely varying anode–cathode (A–C) gap. While keeping the cathode diameter fixed at 40 mm, for the A–C gap distance in the range 5–9 mm, dominant frequencies have been measured to be lying in the range 4.7–9.8 GHz. The trend of a subsequent increase in the dominant frequency at lower A–C gap distances (and vice versa) revealed that center frequency is mainly governed by the longitudinal size of the potential well. The highest microwave power of \sim14~MW for \sim75\-ns pulse duration was obtained at A–C gap of 7 mm having the dominant frequency in C-band at \sim6.9~GHz. The beam-to-microwave power conversion efficiency of \sim1.2\% has been demonstrated in our experiments. On the basis of power distribution pattern obtained by the gas breakdown technique, the dominant mode of emission is believed to be transverse magnetic mode. Relative analysis of frequency spectrums obtained for various A–C gap distances evidenced experimental recognition of optimum A–C spacing as a generation of narrowband distinct frequency peak of large magnitude with minimal mode hopping. [ABSTRACT FROM AUTHOR]

High-voltage double pulse of nanosecond duration (\sim hundreds of nanoseconds) with extremely short interval (\sim tens of nanoseconds) between the pulses can be used to study the double pulse effect in nanosecond laser ablation for laser-induced breakdown spectroscopy. A 0.5-GW compact pulsed-power driver is designed using the transmission line characteristics of the pulse forming line to generate two pulses with extremely short repetition interval. The impedance of the pulsed-power driver is 22 \Omega, and it generates two flat top high-voltage pulses of 100 kV, 100 ns duration with a interpulse repetition interval of 30 ns across the matched load. [ABSTRACT FROM AUTHOR]

This paper reports the results of characterization and optimization experiments carried out on a newly developed NX-3 dense plasma focus device (20 kJ at 20 kV, a quarter time period of \sim\!\!3\ \mu\s, and 10 kJ/600 kA at 14 kV) at the Plasma Radiation Source Laboratory, NIE, Nanyang Technological University, Singapore. Initial experiments were conducted with an electrode assembly configuration having anode radius and length of 20 and 160 mm, respectively, for detailed neutron emission characterization of NX-3 device followed by further optimization of neutron yield using various other electrode configurations designed using the Lee Code. At \geq10-kJ operation, the average neutron yield on the order of 10^9 neutrons/pulse in 4\pi\sr was obtained for the deuterium filling gas pressure range of 6–8 mbar. The neutron yield of \sim\!\!4.6 \times 10^9 neutrons/pulse at 10 kJ/6 mbar is the highest ever reported for a device with the same stored energy. The neutron anisotropy measurements point to the beam–target mechanism as the dominant neutron production mechanism for NX-3 plasma focus device. Further optimization of neutron yield in NX-3 was achieved with the peak average neutron yield being enhanced from \sim\!\!(2.38 \pm 0.31) \times 10^9 neutrons/shot for the initial electrode configuration to about \sim\!\!(3.40 \pm 0.43) \times 10^9 neutrons/shot for the electrode configuration with anode radius and length of 26 and 140 mm, respectively. The analysis of neutron yield results for various electrode assembly configurations demonstrates the speed factor as a key optimization tool for maximization of neutron yield. [ABSTRACT FROM PUBLISHER]

Nanoscience and nanotechnology continue to grow as fields of scientific research and commercial development as many fundamental properties are size dependent on the nano scale. There are so many techniques for the production and characterization of various ultra fine powders. To gain a fundamental understanding of size dependant properties of matter in the nanometer size regimes and to develop nanoscale materials into useful devices to benefit society requires detailed study of the experimental methods, better methods of sample preparation of mono dispersed material in large quantities, and development of nanoparticles characterization methods. Exploding wire method is one such method for the production of metal and metal oxide nanoparticles capable of producing bulk amount of metal nanoparticles at low cost. With the intention of developing better exploding wire system for the production of nanoparticle and to understand the nanoparticle formation process, we have developed two systems in the way of optimization of the experimental set-up for final production of nanoparticles. The detail analysis of the systems and its effect on the nanoparticles has been described in the paper. [ABSTRACT FROM AUTHOR]

The experimental results of an air-core pulse transformer are presented, which is very compact (<10 Kg in weight) and is primed by a capacitor bank that is fabricated in such a way that the capacitor bank with its switch takes the shape of single-turn rectangular shaped primary of the transformer. A high voltage capacitor assembly (pulse-forming-line capacitor, PFL) of 5.1 nF is connected with the secondary of transformer. The transformer output voltage is 160 kV in its second peak appearing in less than 2 μS from the beginning of the capacitor discharge. The primary capacitor bank can be charged up to a maximum of 18 kV, with the voltage delivery of 360 kV in similar capacitive loads. [ABSTRACT FROM AUTHOR]

Abstract: The main elements present in the explosives are hydrogen (H), nitrogen (N), oxygen (O) and carbon (C). The elemental density ratios (C/O, N/O, H/N, etc.) of explosives are different from the other substances. The explosives are characterized by low H and C concentration and high N and O concentration. The elemental composition of explosive materials can be found by measuring the γ-rays produced due to the activation of explosive material by 14MeV neutrons. A pulsed fast neutron system is used for the identification of H, N and O. Ammonium nitrate sample has been irradiated by pulsed 14MeV neutrons of 108 neutrons/pulse and the pulse width less than a microsecond. The material has been irradiated with 5–7 neutron pulse in order to increase the γ-ray count. The resulting γ-ray spectrum due to the activation of ammonium nitrate is recorded and presented in this work. The γ-ray spectrum has been recorded using 3″×3″ Bismuth Germanium Orthosilicate (BGO) and fast digitizer with sampling rate of 2GS/s. The signal is transferred through fiber optic cable to the personal computer for further processing and analyzing. Pulse-height spectrum is constructed through a dedicate MATLAB routine in which the number of energy bins can be kept as per requirement. [ABSTRACT FROM AUTHOR]