A coaxial-output capacitor-loaded annular pulse forming line

A pulse forming line (PFL) cascaded in the radial direction by multistage rolled strip line units is put forward. With this method, the dielectric thickness of the rolled strip line unit is decreased. So, the reliability of the PFL under a high voltage will increase. At the same time, the difficulty for rolling the PFL will decrease. The factors affecting the pulse lifetime of the rolled PFL are analyzed by theory and simulation, and two improvement methods are put forward. First, the electric field enhance at the edges of the electrodes of the rolled PFL is so large that corona discharge occurs at these positions. The improvement method is to use the combination dielectric layer combined by corona-resistant polyimide (PI) films and polypropylene (PP) films as the dielectric of the rolled strip line unit. With this method, the normal electric field of the electrode edges is decreased. Besides, the corona resistance of the dielectric layer is much improved because the PI film has a good performance under corona discharge. Second, the positions where the output foils are located are the insulation weakness of the PFL because these positions are discontinuous. The improvement method is to increase the insulation thickness of these positions. A rolled PFL is cascaded by 3 stages of rolled strip lines, which has a charging voltage of 90 kV. According to the lifetime test, the pulse lifetime of the rolled PFL reaches 300 000 pulses, which is 100 times larger than the pulse lifetime of a rolled PFL without the improvement method.

Insulation improvement of an all-solid pulse forming line with film dielectric

et al. 2019

5-GW Tesla-type pulse generator based on a mixed pulse-forming line

Zeng

et al. 2020

To shorten the length of the pulse-forming line (PFL) and generate pulses with good flat-top quality, a 5-GW Tesla-type pulse generator based on a mixed PFL is developed in this paper to produce intense electron beams and generate high-power microwaves (HPMs). The mixed PFL is composed of a coaxial PFL and a multistage series annular PFL, which, in turn, consists of 18 coaxial-output capacitor-loaded annular PFL modules in series. The generator can produce quasi-square electrical pulses with a width of 43 ns and a peak power of 5 GW on a matched load. In experiments where it is used to drive a relative backward-wave oscillator to generate HPMs, the results show that the HPM frequency is 16.15 GHz and the power is 1.06 GW with an efficiency of 25% when the voltage of the diode is 620 kV and the beam current is 6.9 kA.

An annular pulse forming line based on coaxial transmission lines

Qiu,

Su,

et al. 2024

The miniaturization, lightweight, and solidification of pulse forming lines (PFLs) are of prime significance during the evolution of pulsed power technology. In this paper, an all-solid-state annular pulse forming line (APFL) based on film-insulated coaxial transmission lines is developed to generate fast-rise time quasi-square pulses. First, a coiled coaxial transmission line (CCTL) comprised of multilayer polypropylene films with outstanding insulating properties is constructed. It can withstand direct current voltages up to 200 kV, with a cross section diameter of 7.4 mm. In addition, in order to turn the pulse transmission direction from circumferential to axial, a compact insulated terminal with a 90° bend structure is designed for CCTL. Although single terminal inductance can slow down the rising edge of the output pulse, their parallel connection in an APFL can weaken such an effect. The APFL, with a characteristic impedance of 2.95 Ω and a transmission time of 13 ns, is composed of three CCTLs with six terminals, which can run over 100 thousand times under the pulse voltage of 75 kV. Finally, 15 series APFL modules are employed to assemble a multi-stage PFL for the Tesla-type pulse generator. When charged to a voltage of 1 MV, the mixed PFL consisting of a coaxial line and the multi-stage PFL outputs quasi-square pulses with a voltage amplitude, rise time, and width of 510 kV, 4 ns, and 41.5 ns, respectively, and the fluctuation of the flat top is about 6%.