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A Tesla-type repetitive nanosecond pulse generator including a pair of electrode and a matched absorption resistor is established for the application of solid dielectric breakdown research. As major components, a built-in Tesla transformer and a gas-gap switch are designed to boost and shape the output pulse, respectively; the electrode is to form the anticipated electric field; the resistor is parallel to the electrode to absorb the reflected energy from the test sample. The parameters of the generator are a pulse width of 10 ns, a rise and fall time of 3 ns, and a maximum amplitude of 300 kV. By modifying the primary circuit of the Tesla transformer, the generator can produce both positive and negative pulses at a repetition rate of 1-50 Hz. In addition, a real-time measurement and control system is established based on the solid dielectric breakdown requirements for this generator. With this system, experiments on test samples made of common insulation materials in pulsed power systems are conducted. The preliminary experimental results show that the constructed generator is capable to research the solid dielectric breakdown phenomenon on a nanosecond time scale. [ABSTRACT FROM AUTHOR]

Transmission line pulse transformers have been widely used in pulsed power technology. Traditional transmission line pulse transformers often use separate structures, which always introduces larger spurious parameters, and have lower voltage levels. In order to solve these problems, this note proposes a coaxial transmission line pulse transformer. A circular symmetric structure is used in the input and output ports of the coaxial transmission line pulse transformer, and there are no spurious parameters theoretically. Furthermore, this structure is suitable for hundreds of kilovolts high voltage applications. The structure and working principle of the coaxial transmission line pulse transformer are introduced in this note, and the circuit simulation research is conducted. The factors that affect the pulse transformation are analyzed. Furthermore, experimental studies of the square wave impulse response are conducted on an actual device. The result shows that the proposed coaxial transmission line pulse transformer can achieve the purpose of increasing the voltage amplitude while keeping the pulse waveform undistorted. [ABSTRACT FROM AUTHOR]

Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD (PTFE) > EBD (PMMA) > EBD (Nylon) > EBD (PE). This result is consistent with the theoretical prediction. [ABSTRACT FROM AUTHOR]

Graphene has attracted great interest for its distinctive band structure and physical properties. Results from previous studies show that a graphene cathode can provide stable field emission and intense emission in a vacuum. In this paper, a graphene cathode was fabricated using chemical vapor deposition (CVD) on copper electrodes, and the breakdown of the cathode in a high-pressure gas was studied. A low-jitter, self-breakdown gas spark switch based on a graphene cathode is proposed in this paper. The impulse-breakdown characteristics of this switch in a quasi-uniform electric field were studied. When the gap length is 5 mm, and the gas pressure is 0.6 MPa, the average breakdown voltage ($U_{\mathrm {BD}}$) is nearly 85.9 kV, and the voltage jitter is only 3.2%; these values are much lower than those for pure copper cathodes and graphite cathodes. The graphene cathode is found to be a suitable choice for use as a high-power gas switch in applications requiring an intense emission source. [ABSTRACT FROM AUTHOR]

An improved coaxial high-voltage vacuum insulator applied in a Tesla-type generator, model TPG700, has been designed and tested for high-power microwave (HPM) generation. The design improvements include: changing the connection type of the insulator to the conductors from insertion to tangential, making the insulator thickness uniform, and using Nylon as the insulation material. Transient field simulation shows that the electric field (E-field) distribution within the improved insulator is much more uniform and that the average E-field on the two insulator surfaces is decreased by approximately 30% compared with the previous insulator at a voltage of 700 kV. Key structures such as the anode and the cathode shielding rings of the insulator have been optimized to significantly reduce E-field stresses. Aging experiments and experiments for HPM generation with this insulator were conducted based on a relativistic backward-wave oscillator. The preliminary test results show that the output voltage is larger than 700 kV and the HPM power is about 1 GW. Measurements show that the insulator is well within allowable E-field stresses on both the vacuum insulator surface and the cathode shielding ring. [ABSTRACT FROM AUTHOR]

Based on the Weibull statistical distribution and the thickness effect on dielectric breakdown strength EBD, a formula to evaluate the reliability of solid insulation structures (SISs) in pulsed power systems is derived. By calculating this formula, it is concluded that an increase of 1.4 times in the dielectric thickness d or a 3/4 decrease in the applied voltage U will increase the reliability of SISs by “9.” Moreover, by introducing the variable of pulse number N into the Weibull statistical distribution, a formula to evaluate the lifetime of SISs is also derived. It is concluded that when the time shape parameter a is equal to 1, an SIS is in its normal lifetime stage, and the lifetime can be described by the Martin's formula; when a is not equal to 1, the Martin's formula should be revised. To verify the lifetime formula, experiments were designed and conducted. In the end, useful suggestions on design of SISs are summarized. [ABSTRACT FROM PUBLISHER]

The thickness effect on electric breakdown strength (EBD) of four kinds of polymers under nanosecond pulses is investigated. The polymers are polyethylene, PTFE, PMMA, and nylon. The test samples are 0.5–3.5 mm in thickness (d) and are immersed in transformer oil. The nanosecond pulse is based on a Tesla-type generator, TPG200, which is with values of pulsewidth of 8.5 ns and rise time of 1.5 ns. The experimental results show that EBD is 1–2 MV/cm and decreases as d increases. The dependence of EBD on d is analyzed with the Weibull statistical distribution. It is concluded that \log EBD versus \log d is linear. By replotting the experimental data and by comparing with Martin's results, it is found that the slope for the linear dependence is about -1/8. With this conclusion, the breakdown probability is researched. It is shown that, to get a breakdown probability as low as 0.5%, the applied field should be decreased to about half of EBD. [ABSTRACT FROM PUBLISHER]