Xiaoxin Song’s research while affiliated with Northwest Institute Of Textile Science And Technology and other places

A long-pulse generator TPG700L based on a Tesla transformer and a series pulse forming network (PFN) is constructed to generate intense electron beams for the purpose of high power microwave (HPM) generation. The TPG700L mainly consists of a 12-stage PFN, a built-in Tesla transformer in a pulse forming line, a three-electrode gas switch, a transmission line with a trigger, and a load. The Tesla transformer and the compact PFN are the key technologies for the development of the TPG700L. This generator can output electrical pulses with a width as long as 200 ns at a level of 8 GW and a repetition rate of 50 Hz. When used to drive a relative backward wave oscillator for HPM generation, the electrical pulse width is about 100 ns on a voltage level of 520 kV. Factors affecting the pulse waveform of the TPG700L are also discussed. At present, the TPG700L performs well for long-pulse HPM generation in our laboratory.

An approach for producing a long pulse up to 100 ns is presented. The generator based on this approach consists of a Tesla transformer and a set of pulse-forming networks (PFNs). The Tesla transformer is used to charge pulse-forming lines (PFLs) and PFNs which are in parallel. When the voltage increases to a certain value, the main switch will close, and the PFLs and PFNs will discharge rapidly to the load. Therefore, a high-voltage long pulse is formed on the load. The amplitude of this pulse is dependent only on the charging voltage and the matching state between the load and the PFL (PFN). The pulsewidth is determined by the transmission time of the PFL and PFN. The rise time is determined by the working state of the main switch and the impedance of the PFL and is independent of the parameters of the PFN. The PFN is multistage and assembled in series. The single-stage PFN is formed with ceramic capacitors placed between two unclosed annular plates. The total series impedance is equal to the sum of every single-stage PFN's impedance. A nine-stage PFN is used in the generator, and the total impedance is 40 Omega. Experimental results show that a high voltage of an amplitude of 300 kV, current of 6.9 kA, and duration of 110 ns is obtained at a repetition rate of 10 Hz, with a rise time of approximately 7 ns.

An all-solid-state nanosecond generator has been developed and tested in Northwest Institute of Nuclear Technology. The generator is based on SOS-technology and is designed to deliver pulses with FWHM of 40 ns and amplitude up to 200 kV at 2 kHz repetition rate into a load in burst mode. The average output power is 13 kW. The inductive storage, the Semiconductor Opening Switch (SOS) and the magnetic pulse compressor work as the power amplifiers. The magnetic pulse compressor pumps the SOS. A primary charging unit is used as the generator input. The magnetic pulse compressor and the SOS are the key components of the generator. The material of the pulse transformer core is FeSi and Metglas. Two SOS-180-4 diodes are used in the generator in series. This unit has the operating voltage of 360 kV and cuts off currents up to 2 kA about 10ns.The design of generator, its circuitry operating principle, and experimental results obtained have been described.

The source-antenna-integrated device can produce and radiate high power level fast risetime pulses, with carefully maintaining the symmetry structure of the monocone antenna and designing of the oil spark switch. It is compact, simple, and robust. The device could be used to feed impulsive radiating antenna and for other applications re quiring high peak power level electromagnetic pulse(EMP) radiation.

In 1901 Marconi tested the propagation property of electromagnetic fields using the folded monopole antenna, which was 150 ft in height, 200 ft in width, and excited at the tip of the monopole by the shorting of a spark gap. In the study of ultra-wideband electromagnetic pulse technology, we noted that with some improvements, the prototype method Marconi used has significant advantages over the popular source-antenna-separated microwave launching system, especially for producing and launching Ultra-WideBand (UWB), high power level, and impulsive electromagnetic fields. As the power level increases and risetime decreases, the transmission line approximation turns out to be unsuitable for analyzing the field distribution of UWB systems with baluns and transmission lines, owing to the transit time dispersion, skin and dielectric losses, and electrical breakdown effects. Therefore, the introduction of baluns and transmission lines into high power level UWB systems will degrade the system performance, and make the theoretical analysis of the loss mechanism extremely difficult. By integrating the source and antenna directly, one can reduce the loss significantly and design a compact, simple, and robust device that can be used to produce and radiate UWB pulses simultaneously. This paper presents the design and experimental study of the so-called “source-antenna-integrated” device, including the theoretical analysis and numerical simulation of the conical antenna

The characteristic frequency and energy conversion efficiency of the coaxial vircator are studied by numerical simulation method. Comparing with planar vircator, the coaxial vircator generates much narrow bandwidth and higher center frequency. The simulation results also evince that by adjusting d can tune the output microwave frequency in about two octave range under certain conditions. The negative pulsed coaxial vircator can significantly improved efficiency from about 4% of positive pulsed coaxial vircator to about 10%. The experimental apparatus are setting up, the experimental results will be given in future

The results of the breakdown of microwave pulses in air have been described in this paper. The experimental study has been done in a waveguide, with the frequency of 9.37 GHz, and the peak power up to 200 kW, pulse width from 0.3 microsecond(s) to 2.0 microsecond(s) , single shot and repetition rate up to 970 Hz, and the processes of the breakdown of repetitive pulse were also recorded for ten pulses. The analytic methods for threshold power density are presented also. The comparisons between the theoretical and the experimental results for the breakdown threshold are presented, and in good agreement.