Output voltage waveform analysis of an intense electron beam accelerator based on strip spiral Blumlein line

Abstract

The Blumlein pulse forming line (BPFL) consisting of an inner coaxial pulse forming line (PFL) and an outer coaxial PFL is widely used in the field of pulsed power, especially for intense electron-beam accelerators (IEBA). The output voltage waveform determines the quality and characteristics of the output beam current of the IEBA. Comparing with the conventional BPFL, an IEBA based on a strip spiral type BPFL can increase the duration of the output voltage in the same geometrical volume. However, for the spiral type BPFL, the voltage waveform on a matched load may be distorted, which influences the electron-beam quality. In this paper, the output waveform of an IEBA based on strip spiral BPFL is analyzed. It is found that there is fluctuation on the flattop of the main pulse, and the flatness is increased with the increment of the output voltage. According to the time integrated pictures of the cathode holder during the operation of the IEBA, the electron emission of the cathode holder is one of the reasons to cause the variance of the flatness. Furthermore, the distribution of the current density of spiral middle cylinder of the BPFL is calculated by using electromagnetic simulation software, and it is obtained that the current density is not uniform, and which leads to the nonuniformity of the impedance of BPFL. Meanwhile, when the nonuniformity of the BPFL is taken into account, the operation of the whole accelerator is simulated using a circuit-simulation code called PSpice. It is obtained that the nonuniformity of the BPFL influences the flatness of the output voltage waveform. In order to get an ideal square pulse voltage waveform and to improve the electron beam quality of such an accelerator, the uniformity of the spiral middle cylinder should be improved and the electron emission of the cathode holder should be avoided. The theoretical analysis and simulated output voltage waveform shows reasonable agreement with that of the experimental results.

A Method to design composite insulation structures based on reliability for pulsed power systems

“…Coaxial HV vacuum insulators are widely used in the Teslatype pulsed power generators (Zhao et al, 2010;2013a;Peng et al, 2011;Liu et al, 2012) and others types of generators (Xun et al, 2008;Cheng et al, 2012). With a coaxial HV vacuum insulator, the proposed method to design composite insulation structures is exemplified.…”

“…Generally, there are three types of composite insulation structures: gas/solid insulators (Xiao et al, 2010;Peng et al, 2011;Shao et al, 2012;Zhao et al, 2013a), liquid/solid insulators (Wang et al, 2005;Cheng et al, 2012;Liu et al, 2012;Zhao et al, 2012;2013b;2013c), and vacuum/solid insulators (Kiricov et al, 2003;Milton, 1972;Miller, 1989;1993;Zhao et al, 2010;Wang et al, 2012;. These insulators play both the roles of separating a megavolt pulse voltage and presenting mechanical support.…”