A coaxial solid state nonlinear pulse forming line with an exponentially tapered ferrite composite core

Travis D Crawford; Sophia I Evers; Bradley H Sapoff; Allen L Garner

doi:10.1063/5.0230724

A coaxial solid state nonlinear pulse forming line with an exponentially tapered ferrite composite core

Rev Sci Instrum. 2024 Dec 1;95(12):124709. doi: 10.1063/5.0230724.

Authors

Travis D Crawford¹, Sophia I Evers¹, Bradley H Sapoff¹, Allen L Garner^{1

2

3}

Affiliations

¹ School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
² Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
³ Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana 47907, USA.

PMID: 39679933
DOI: 10.1063/5.0230724

Abstract

The need to optimize size, weight, and power of high-power microwave (HPM) systems has motivated the development of solid-state HPM sources, such as nonlinear transmission lines (NLTLs), which utilize gyromagnetic precession or dispersion to generate RF. One recent development implemented the NLTL as a pulse forming line (PFL) to form a nonlinear pulse forming line (NPFL) system that substantially reduced the system's size by eliminating the need for a separate PFL; however, matching standard loads can be challenging. This paper describes the development of a tapered NPFL using an exponentially tapered composite based ferrite core containing 60% nickel zinc ferrite (by volume) encased in polydimethylsiloxane (PDMS) and encapsulated in a 5% barium strontium titanate shell. The tapers exponentially change the line's impedance from a 50 Ω standard HN connection to 25 Ω before tapering back to 50 Ω. We characterized the core behavior by obtaining magnetization curves and ferromagnetic resonance measurements. The rise time (10%-90%) of the pulse decreased from ∼6 ns for 5 kV charging voltage to 1.8 ns for 15 kV charging voltage. Under unbiased conditions, the system generated HPM with a center frequency of ∼850 MHz with a 3 dB bandwidth of 125 MHz. Magnetic biases of 15 and 25 kA/m increased the modulation depth and decreased the center frequency to ∼500 MHz for 15 kV charging voltage.