Abstract
The breakdown characteristics of a trigatron spark gap triggered by a plasma jet are studied in this paper; the development of a plasma jet and the influence of the gap distance, working coefficient, and plasma jet ejection properties on breakdown characteristics are compared. The results show that the plasma jet ejecting process can be divided into expanding, steady, and dissipating phases. The electric field distortion induced by the plasma jet is different during the expanding and dissipating phase, in which the plasma jet length increases and the radius of the curvature of the plasma jet front decreases, respectively. As the two processes have different variation rates, a faster increasing rate of the breakdown delay can be obtained during the dissipating phase. A detailed physical mode that explains the effects on the triggered breakdown process is presented. The shape of a plasma jet induced by polyethylene and ceramic surface discharge changes to a great extent during the dissipating phase; a more stable plasma jet can be obtained when induced only by polyethylene, resulting in a smaller breakdown delay under a low working coefficient. The ultraviolet radiation (UV) generated by the plasma jet is effective in reducing the critical breakdown electric field, while the electric field distortion induced by the plasma jet is the main reason behind the triggered breakdown under different working coefficients; the UV could play a limited role in the triggered breakdown process.
Highlights
Gas-insulated trigatron spark gaps could be used in a wide range of applications as high voltage switches in high-voltage pulse forming networks, as Marx generators and particle accelerators due to their voltage and current handling capabilities, and in simple constructions and applications in high voltage engineering.1–3 In order to increase the operating reliability, the working coefficient of a spark gap needs to be lower than 60%.4–7 A working coefficient is defined as the ratio of the charging voltage to the self-breakdown voltage of the spark gap
The physical development of a trigatron spark gap breakdown triggered by a plasma jet is analyzed, and the influence of the gap distance, working coefficient, and plasma ejection properties on breakdown characteristics of spark gap is compared
The irregular shape of the plasma jet can make the discharge type change from sphere-to-plane discharge to rod-to-plane discharge and has the tendency to change to needle-to-plane discharge, making the breakdown criterion easier to reach due to more serious electric field distortion
Summary
Gas-insulated trigatron spark gaps could be used in a wide range of applications as high voltage switches in high-voltage pulse forming networks, as Marx generators and particle accelerators due to their voltage and current handling capabilities, and in simple constructions and applications in high voltage engineering. In order to increase the operating reliability, the working coefficient of a spark gap needs to be lower than 60%.4–7 A working coefficient is defined as the ratio of the charging voltage to the self-breakdown voltage of the spark gap. The reliable working coefficient of the conventional triggering technology for trigatron switches and field distortion switches is generally above 70%.2,8,9. It is indicated that plasma jet triggered gas switches can achieve a reliable breakdown probability under low working coefficients. By injecting a plasma jet, the electric field distortion is enhanced gradually with the development of plasma ejection, and the reliable triggering performance of gas switches is obtained.. As the breakdown delay time and jitter are the most crucial parameters of the discharge characteristics of a spark gap, this paper mainly focuses on the change in trend of the breakdown delay time and jitter of the trigatron spark gap, and gives reasonable explanations of the breakdown delay time and jitter formation under the surface ablation plasma jet triggered breakdown process. The physical development and the main influence factors of the breakdown delay time and jitter are analyzed with high-speed multiframe camera photos
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