Search

Although plasmas commonly present as electrical neutrality, for plasma jet plume at atmospheric gas pressure, it might appear nonneutral polarity due to plasma bullet being consisted of a large amount of electron avalanches. In this paper, the polarity transition and the ionization enhancement of atmospheric argon plasma jet plumes generated by the repetitive microwave pulses are studied. Three interesting phenomena have been found despite of discharges either with or without the hairpin metal wire, including: 1) a potential voltage pulse with positive polarity invariably arises steeply at each moment of power on; 2) high-speed photograph images show that there are ionization enhancements happened twice in each pulsed periods; and 3) ahead of the confluence point, the polarity transits from negative to positive while behind of this point, its positive polarity changes into the negative one. Moreover, the experiment results and electromagnetic simulations suggest that the theories of guided negative ionization wave and microwave resonant discharge excited by surface plasma polaritons should be used to interpret the spatial–temporal discharge process of the proposed microwave plasma jets. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the failure mechanism of high-current gallium arsenide photoconductive semiconductor switches (GaAs PCSSs) triggered by the laser diode. We propose a Blumlein pulse forming line to test the GaAs PCSS. The result shows that the damage of GaAs PCSS almost occurs at the anode under the circumstances that either anode or cathode is illuminated, since the highest amplitude of Gunn oscillation always occurs on the anode. We speculate that the failure of high-current GaAs PCSS is attributed to the Gunn effect according to the statistics about failure factors of GaAs PCSS. We use a scanning electron microscope to semiquantitatively analyze the compositions of the erosions microball or granules, which are gallium and arsenium. The result proves our speculation. [ABSTRACT FROM AUTHOR]

A B-dot was used for measuring cathode emission current in the injector of a linear induction electron accelerator. The measured current waveforms in commissioning were different from our initial expectation. This could well be explained by that the measured current waveform was the sum of actual emission current and displacement current. The displacement current could be derived by the measured diode voltage and the calculated diode capacitance. The actual emission current waveform was then obtained by subtracting the displacement current from the measured waveform. The pure displacement current waveform was also measured by the B-dot, while there was no emission from a thermionic cathode. The calculated and measured displacement current waveforms were well consistent with each other. The B-dot’s sensitivity factor calibrated by comparing the aforementioned two waveforms was equal to our theoretical estimate within an error range. The obvious displacement current may also exist in the similar pulsed power facilities, which contain high-voltage and fast pulses. It can be processed by the same methods discussed in this paper. [ABSTRACT FROM PUBLISHER]

Presents algorithms for calculating optimal deconvolution estimators while considering the problem of optimal input estimation using an innovation analysis method in the time domain. Description of the tool for obtaining the estimators; Input problems covered by the algorithm; Application of the algorithm.