High-permeability cobalt-based amorphous core for the use of an untuned broadband RF cavity

We developed a cobalt-based amorphous core as a new magnetic-alloy (MA) core for a loaded radio frequency (RF) cavity. Because of its low-quality-factor, high-permeability property, the core is suitable for constructing an untuned broadband accelerating cavity. While FINEMET FT-3M has been widely used as the core material, the permeability of our newly developed amorphous core is found to be approximately twice that of FINEMET FT-3M. This amorphous core is thus an excellent candidate for achieving a high-impedance cavity with low power consumption. Several measurements were taken in order to understand its feasibility and stability. The actual large-size cores were then manufactured for the first time for accelerator use.