Zeng Zhengzhong

Experimental Investigations on Trigger Characteristics of Pseudo- spark Switch Based on Surface Flashover Technology

A trigger device and a triggered pseudospark switch (TPSS) were designed based on surface flashover technology, in order to meet the requirements from present pulse power technology and pulse current test technology such as a long lifetime, reliability in a wide voltage range, a short delay time, as well as small delay jitters. The trigger devices were made from different dielectric materials, with their permittivities from tens to thousands. The trigger characteristics of TPSS were investigated. The results indicate that the high-dielectric trigger device shows better performance and higher emitted charge of the electron emission within all adjusted parameters including the gas pressure and applied voltage. For the dielectric material with relative permittivity er of 3460, when the gas pressure is 7 Pa, the hold-off voltage of TPSS is 28 kV, the minimum trigger switch voltage drops to 128 V, the minimum discharging delay time and delay jitter are less than 35ns and 6ns, respectively, and the reliable operation can be reached within a very large range of charging voltage, between 0.46% and 99% of its self-breakdown voltage.

Experimental Study of Current Loss of Stainless Steel Magnetically Insulated Transmission Line with Current Density at MA/cm Level

A magnetically insulated transmission line (MITL) is used to transmit high power electric pulses in large pulse power systems. However, current loss is unavoidable, especially when the current density is up to 1 MA/cm. In the paper, the current loss of an MITL made of stainless steel, which is usually used in large pulse power generators, is experimentally studied, and possible mechanisms to explain the current loss of the MITL are analyzed and discussed. From the experimental results, the relationship between loss current density and input current density follows approximately a power law. The loss is also related to the configuration of the MITL.

Study on Performance Parameters of the Plasma Source for a Short-Conduction-Time Plasma Opening Switch

Plasma source performance parameters, including plasma ejection density and velocity, greatly affect the operation of a short-conduction-time plasma opening switch (POS). In this paper, the plasma source used in the POS of Qiangguang I generator is chosen as the study object. At first the POS working process is analyzed. The result shows that the opening performance of the POS can be improved by increasing the plasma ejection velocity and decreasing the plasma density. The influence of the cable plasma gun structure and number on the plasma ejection parameters is experimentally investigated with two charge collectors. Finally a semi-empirical model is proposed to describe the experimental phenomenon.

Optimization of Cavity Combination for 20-MA LTD-Based Accelerators

Based on a transmission line code, a circuit model is proposed that could serve as the basic method for the analysis of linear transformer driver (LTD)-based accelerators. By using 1 MA, 100 kV LTD cavities, the peak load current is optimized for a total of N cavities between 500 and 1200. The simulation results suggest that, with the same number of cavities, the peak current changes obviously with the types of combinations, and the maximum change can be as large as 1.2 MA. The results also show that, for the cases considered, the optimized peak current as a function of the total number of cavities agrees with the exponential associate, and the peak current for one level LTD cannot be enhanced infinitely. Furthermore, it is found that, to obtain a 20 MA peak load current, at least 1029 LTD cavities (49 in series and 21 in parallel connection) are needed. Finally, the typical parameters of the optimized design are compared to those of the existing Z accelerator.

Dynamic Model for the Z Accelerator Vacuum Section Based on Transmission Line Code

The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al, is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance (used to represent any electron loss to the anode) and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.