Ferroelectric Based High Power Components for L-Band Accelerator Applications

Both superconducting and conventional accelerating structures require fast electronic control of the input rf power. A fast controllable phase shifter would allow for example the control of the rf power delivered to multiple accelerating cavities from a single power amplifier. Nonlinear ferroelectric microwave components can control the tuning or the input power coupling for rf cavities. Applying a bias voltage across a nonlinear ferroelectric changes its permittivity. This effect can be used to cause a phase change of a propagating rf signal or change the resonant frequency of a cavity. The key is the development of a low loss highly tunable ferroelectric material. The focus of Phase I was development and measurement of the dielectric properties, phase composition, and microstructure of new low-loss nonlinear BST(M) ceramics with the required properties. Design and simulation of a prototype phase shifter (to be built and tested in Phase II) based on these materials were performed. Argonne, Brookhaven, Oak Ridge have shown interest in ferroelectric based components for high power management applications. The planned RHIC 1.3 GHz ERL linac upgrade uses superconducting RF cavities and requires fast tuning of the cavity coupling to the RF feed line. The ferroelectric tuning devices proposed here will enable the required fast phase correction and control. In Phase II of this project, the BST(M) ferroelectric tunable components will be used in a prototype L-band phase shifter. Commercial Applications and Other Benefits: The new BST composition will definitely find a variety of large-signal commercial and military applications like radar antenna elements, electrically-controlled phase shifters, and switching devices.