Operating characteristics of intense electron beam accelerator at different load conditions

Abstract

As the development of the pulsed power technology, high voltage pulse transformer (HVPT) is usually used instead of Marx generator as a charging device for the pulse forming line (PFL) of intense electron-beam accelerator (IEBA), and which make the IEBA compact. However, during the operation of the IEBA, the HVPT may be destroyed for the failure of electrical insulation and the over-voltage. So in this paper, the output voltage characteristics of IEBA, characteristics of the voltage at the output terminal of HVPT at four kinds of load conditions are analyzed, including load matching, load short, load open, and surface flashover in the vacuum chamber. It is found that load short, load open, and surface flashover in vacuum chamber will affect the voltage at the output terminal of HVPT, and an oscillation wave could be formed, which affect the electrical insulation of HVPT and decrease the lifetime of HVPT. Meanwhile, the waveform of the load voltage is also modified, especially at the conditions of load open and surface flashover in vacuum chamber. When the load is open, the amplitude of the output main pulse of IEBA is twice the charging voltage of BPFL. However, the amplitude of the output pulse of IEBA is modified by the voltage at the output terminal of HVPT, and the resistance of main switch channel has a great effect on the amplitude of the load voltage. When surface flashover occurs in the vacuum chamber, the pulse duration of the output voltage will be decreased. So, during the operation of IEBA, load short, load open and surface flashover in vacuum chamber should be avoided.

Dispersion and Dielectric Effects on Reflection and Transmission of Electromagnetic Waves Propagating in Multiple Stages of Tape-Helix Blumlein Transmission Lines

“…In this paper, (18) is adequate to describe the wave transmission and reflection characteristics in multiple stages of helical lines. In comparison with the relevant classical conclusions obtained from the classical nondispersive propagation theory used in [28][29][30], the transmission and reflection coefficients described by impedances are also extrapolated from the proposed dispersive propagation theory. In line with the method used in [32,33], the axial travelling current wave I 0zi in the ith stage transmission line can be calculated by integrating the azimuthal magnetic field component along the surface of the tape helix; furthermore, the characteristic impedance Z i of the ith stage helical line can also be extrapolated as (19).…”

“…When R load = 220 Ω, ξ u can be calculated from the first equation in (30), and the result is ξ u = 220/(220 + 80 + 80) = 57.9%. Experiment was carried out when R load = 220 Ω (R load > Z B ), and the load voltage pulse formed at point A is shown in Fig.…”

“…Under the impedance matching condition that R load = 160 Ω = Z in + Z out , ξ u = 1/2 and U 1 /U 0 = 0 can both be obtained from (30) in theory. In experiment, the task was to demonstrate the theoretical result U 1 /U 0 = 0 or U 1 = 0.…”

“…The problems of wave propagation, transmission and reflection in multiple layers of dielectrics or at dielectric-fractal interface were concerned in reference [26,27], but dispersion problems were not considered. Through employing the nondispersive travelling wave propagation method based on telegraphers' equation, the transmission and reflection of the square voltage waves at different impedance ports were analyzed in detail in references [28][29][30] without considering the helical dispersion. Through combining the helical dispersion theory and the non-dispersive lumped circuit theory, references [31][32][33] calculated the parameters of tape-helix Blumlein lines, but the employed dispersion theory based on an approximation of "infinite-long line" can not analyze the wave reflection, transmission and the S-parameters at the ports of the helical transmission line with a finite length.…”