Tang Junping

Cathode Plasma Integral Spectroscopy Diagnosis on High Current Pulsed Electron Beam Diode

Cathode plasma is an important factor affecting the cathode emission on high current pulsed electron beam diode. Diagnosing the cathode plasma composition by integral spectrum system is a method for studying the cathode plasma formation and development process. The aim of this paper is to study the cathode plasma composition and analyze the cathode plasma formation mechanism by integral spectroscopic diagnosis of different materials and cathode pretreatments. Experiment results show that not only cathode material itself, but also impurity material and adsorptive gas on cathode surface are found in the cathode plasma. For the same material, the cathode plasma composition remains unchanged, whereas the characteristic line intensity decreases as the experiment times increase. The composition of the cathode plasma can be controlled by adulterated treatment.

Comparison of two field-distortion gas switches for the compact Marx generator

To get the better choice for achieving higher stability and reproducibility of the output voltage pulse of the generator, two pancake switches commonly used in the low energy, high peak power Marx generator have been compared. The comparison is done in several aspects including the structure, the electric field distribution, and the breakdown characteristics. Some useful conclusions are drawn. And there is a big difference between the structural capacitances of the two gas switches as a result of the different configuration of their electrodes. So a circuit simulation of the switch used in a simple, basic, two-stage Marx circuit has been done on both switches respectively.

Characteristics of SF6 Switch with a Small Gap under High Pressure and Nanosecond Pulse

Structural design and tests on the characteristics of the SF6 gas switch with a small gap are presented. This kind of switch often works under high pressure and nanosecond pulse for getting pulse with faster risetime. The breakdown voltage and breakdown delay of a number of switches with different geometries, gas pressures and pulse waveforms were investigated. Experimental results suggested that the breakdown voltage increases linearly with the gas pressure, and the breakdown delay decreases with an increase in the gas pressure and a reduction in the gap distance of the switch under the same applied pulse. By using this kind of switch with a gap of 3 mm as a peaking switch, a pulse generator can provide an output voltage with a peak voltage of 300 kV and a risetime of 3 ns on a resistance load of 150 Ω.

The vacuum flashover characteristics of dielectrics under ns pulse

The solid dielectrics such as epoxy, high density polyethylene(HDPE), polytetrafluoroethylene (PTFE), nylon and polymethylmethacrylate(PMMA) are often used as vacuum insulator in pulsed power device, in which they were applied under pulse voltage with risetime from several to several tens nanoseconds. Flashover characteristics must be paying more attention because they are the major breakdown models in their applications. A pulse source with output voltage of 50 ns risetime, 320ns pulse width and peak voltage up to 200 kV has been developed in this research. The flashover characteristics including flashover voltage and flashover current of the materials mentioned above under plane electrode were tested under 5E-3Pa vacuum. In order to get the relationship between surface charge deposition and the flashover characteristics, the surface potential distribution before flashover and after once, seventh and thirty-fifth flashovers are presented in this paper.