1 kHz rep-rate operation of a spark-gap switched gyromagnetic nonlinear transmission line array

Abstract

This paper details the design, fabrication and performance of a coaxial ferrimagnetic nonlinear transmission line (NLTL), four element array, high power microwave (HPM) system operated at a 1 kHz repetition rate. Prime power is delivered from an 802L TDK Lambda power supply which charges a 5.2 nF capacitor bank up to −40 kV. The capacitors are discharged through a center pin trigatron spark gap. The trigger generator is optically isolated and battery powered for noise immunity and portability. It produces a 20 kV positive polarity pulse with a 20 ns risetime. The high dV/dt (1 kV/ns) is desirable to reduce jitter inherent to spark-gap switching. After the spark-gap switch has closed, the pulse is split four ways. The four pulses propagate through four adjustable delay lines for synchronization of the individual outputs. The four delay lines connect directly into four 76 cm NLTLs with NiZn ferrites where SF 6 is the insulating dielectric. Each NLTL is terminated into a custom fabricated, Rexolite-filled, TEM horn antenna via a zipper balun. Lastly, a LabVIEW based control system automates the whole system using a National Instruments cRIO controller. Experimental observations will include in-line D-dot measurements of voltage waveforms and radiated D-dot field measurements.