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Start Over Author "Qiu, Aici" Journal ieee transactions on plasma science
49 results on '"Qiu, Aici"'

9. Numerical Investigation of Runaway Electrons During the Breakdown of Homogeneous Electric Field Air Gaps Under Nanosecond Pulse Voltage

Author

Wen, Zhenming, Jiang, Ming, Wang, Zhiguo, Fan, Siyuan, Ren, Shuyi, and Qiu, Aici

Abstract

The development of discharge that starts near the cathode in a homogeneous electric field air gap under nanosecond pulse voltage is studied using a 2.5-D particle-in-cell/Monte Carlo collisional model. The simulation is first performed in the absence of photoionization reactions. It is found that runaway electrons are produced in the head of the streamer when the local electric field strength is sufficiently high. Runaway electrons ionize the area in front of the streamer tip while producing abundant preionization electrons, which significantly accelerate the rate of discharge propagation. Photoelectrons and runaway electrons perform an analogous role in preionizing gas, but the latter is more efficient because of their directionality. A more complete discharge process is simulated in the presence of photoionization reactions. Electrons with relatively high energy appear in the bipolar end of the discharge channel while the discharge continuously progresses toward the anode. During the later moment of discharge, the streamer expands to the anode at an extremely fast velocity as a result of the combined action of photoionization and runaway electrons located at the negative streamer tip. The simulation results reveal the discharge mechanisms of the air gap applied with a homogeneous electric field under a nanosecond voltage pulse and provide a comprehensive understanding of the fast breakdown of air gaps.

Published
2023
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14. Development of a 4-MV, 80-kA-Induction Voltage Adder for Flash X-ray Radiography

Author

Wei, Hao, primary, Sun, Jiang, additional, Liu, Wenyuan, additional, Luo, Qiangfeng, additional, Ding, Weidong, additional, Hu, Yixiang, additional, Yin, Jiahui, additional, Zhang, Pengfei, additional, Sun, Fengju, additional, Qiu, Aici, additional, Liang, Tianxue, additional, Zeng, Jiangtao, additional, Jiang, Xiaofeng, additional, and Wang, Zhiguo, additional

Published
2019
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17. A high-current high-di/dt pulse generator based on reverse switching dynistors

Author

Wang, Haiyang, He, Xiaoping, Chen, Weiqing, Xue, Binjie, and Qiu, Aici

Subjects
Pulse generators -- Design and construction, Pulse generators -- Usage, Business, Chemistry, Electronics, Electronics and electrical industries
Abstract

A scheme for a high-current high-di/dt pulse generator is described, which incorporates an assembly of reverse switching dynistors (RSDs), a magnetic compression section, a trigger circuit based on a step-up saturable pulse transformer, and an additional RSD unit with a small working area. The generator, with an operating voltage of 10 kV, can switch a 108-kA pulse current with a full width at half maximum of about 65-[micro]s duration, a di/dt of 8.66 kA/[micro]s, and a jitter of less than 60 ns. The charge transferred and action are about 6 C and 0.53 [MA.sup.2]s, respectively. Index Terms---di/dt, pulse generator, reverse switching dynistor (RSD), saturable transformer.

Published
2009

24. Investigation of the Load Current Tail Phenomenon on the Qiangguang Generator

Author

Wei Fuli, Wang Liangping, Guo Ning, Han Juanjuan, Wu Jian, Qiu Aici, and Li Mo

Subjects
Physics, Nuclear and High Energy Physics, business.industry, Electrical engineering, Insulator (electricity), Mechanics, Condensed Matter Physics, Electric power transmission, Stack (abstract data type), Transmission line, Z-pinch, Arc flash, Equivalent circuit, Waveform, business
Abstract

The phenomenon of load currents with long decaying tails can be found on many pulsed-power generators, such as the Z accelerator at Sandia National Laboratories in the U.S. and the Angara-5-1 facility in Russia. In this paper, the reasons that cause the load current tail on the Qiangguang generator are investigated. The experiments were carried out using two insulator stacks with different diameters and insulator ring numbers. The results show that the current tail on the Qiangguang generator is not caused by measurement error but rather by electrical flashover across the surface of the insulator stack and by leakage current through the water between the stack and the outer wall of the water-filled transmission line that feeds the vacuum section on the Qiangguang generator. Also, an equivalent circuit for the Qiangguang generator was constructed and used in PSpice simulations. By adding a time-dependent resistance in parallel with the load, the simulations were able to produce current waveforms that closely match those recorded during experiments. In additional experiments, an optical fiber was used with a photoelectric cell to collect the flashover light emitted from the surface of the vacuum-insulator rings. The data collected show that the fiber signal and the beginning of the load current tail are time correlated. More recently, a new insulator stack made of Rexolite was acquired and used in yet more experiments. The results of these experiments show that, by using the new insulator stack, the onset of the load current tail phenomenon is significantly delayed. The data from all of the experiments show that stack flashover is the main cause of the load current tail on the Qiangguang generator.

Published
2012

27. Effect of Cathode Material on the Opening Performance of Microsecond-Conduction-Time Plasma Opening Switch

Author

Zeng, Zhengzhong, Sun, Fengju, Qiu, Yuchang, Bai, Feng, and Qiu, Aici

Subjects
Plasma devices -- Design and construction, Plasma engineering -- Research, Business, Chemistry, Electronics, Electronics and electrical industries
Abstract

Experiments were conducted to investigate the effect of cathode material on the opening performance of microsecond-conduction-time plasma opening switch with cathode made of aluminum, stainless steel, molybdenum and tungsten. Remarkably different opening characteristics have been shown for these materials, with tungsten or molybdenum corresponding to better opening performance than aluminum or stainless steel. Heuristic physical explanations are proposed for understanding the switch behavior. Index Terms--Cathode material, microsecond-conduction-time, opening performance, plasma opening switch.

Published
2001

47. Trigger Method Based on Secondary Induced Overvoltage for Linear Transformer Drivers.

Author

Yin, Jiahui, Liu, Peng, Wei, Hao, Sun, Fengju, and Qiu, Aici

Subjects
SIMULATION methods & models, PERMEABILITY, ELECTRONIC circuits, ELECTRIC transformers, ELECTRIC potential
Abstract

In this paper, a triggering method based on secondary induced overvoltage for a linear transformer driver (LTD) is proposed and investigated by simulation. A detailed circuit model established for the LTD is chosen to study the effect of some factors on the feasibility of this triggering method. The considered factors include the permeability, equivalent resistance of energy loss, saturation of magnetic cores, and the delay of gas switches in LTD cavities. Simulation results indicate that high equivalent resistance and high permeability of magnetic cores are helpful in realizing this trigger method. However, the resistance plays a leading role. An equivalent resistance of more than 1.5 \Omega favors the realization of this trigger. However, a relative permeability of even 25 has not produced a fatal menace to this triggering method. The feasibility of this triggering necessitates the available volt–second product of the present magnetic cores to be expanded twice. As for gas switches, the interval given by secondary induced overvoltage would likely be long enough to complete their breakdown. From simulation results, it is shown that LTD switches could be rapidly closed under the action of such an overvoltage pulse with a rise time of less than 10 ns. [ABSTRACT FROM PUBLISHER]

Published
2013
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48. 300-kA Fast Linear Transformer Driver Stage.

Author

Liang, Tianxue, Jiang, Xiaofeng, Sun, Fengju, and Qiu, Aici

Subjects
ELECTRIC potential, ELECTRIC currents, CAPACITORS, ELECTRIC circuits, ELECTRIC transformers
Abstract

A modular linear transformer driver (LTD) is a novel fast-discharge high-pulsed power source for primarily stored energy. In LTDs, a large number of stages (or cavities) can be connected in series or in parallel conveniently to directly generate high power pulses of 50–200 ns with the required voltage or current. This paper introduces an LTD stage developed by us recently. This LTD stage consists of 14 bricks in parallel. Each brick contains two 40-nF capacitors and a compact multigap gas spark switch in series. The switch is a modification of our original version, and the diameter and the height of which have been reduced to 98 and 127 mm, respectively. The circuit model of this stage is established in PSPICE, and its output parameters are obtained through simulation. Driving a rough-matched resistive load of 0.27 \Omega, its output current peak is 300 kA with an overall rise time of about 110 ns at a charged voltage of the capacitors of about \pm90 kV, agreeing well with its simulation result. [ABSTRACT FROM PUBLISHER]

Published
2012
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49. Effect of Cavity-Triggering Sequences on Output Parameters of LTD-Based Drivers.

Author

Liu, Peng, Sun, Fengju, Yin, Jiahui, Liang, Tianxue, Jiang, Xiaofeng, Liu, Zhigang, and Qiu, Aici

Subjects
ELECTRIC transformers, ELECTRIC switchgear, MAGNETIC cores, ELECTRIC lines, POWER transmission, ELECTRONIC circuits, ELECTROMAGNETIC pulses, ELECTRIC potential, FEASIBILITY studies
Abstract

This paper explores the feasibility of improving the load current parameters by optimizing the cavity-triggering sequences for a linear transformer driver (LTD) module with 60 cavities connected in series. The mechanism behind this was analyzed. The results demonstrate that it is necessary for the improvement in the output parameters of the LTD to postpone the closure of the switches in the cavities later than the arrival of the electromagnetic pulse propagating downstream. However, this requires the switches to withstand pulsed voltages higher than their charge voltage before closing. When the LTD switches withstood a pulsed voltage peak of about 400 kV for several tens of nanoseconds before closing, the LTD module could generate a current pulse with a rise time of 12.5 ns and a peak of 1340 kA on the matched load. [ABSTRACT FROM AUTHOR]

Published
2011
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