Perpendicularly Biased YIG Tuners for the Fermilab Recycler 52.809 MHz Cavities

TL;DR

This paper presents the design, measurement, and high power testing of a perpendicularly biased YIG tuner for 52.809 MHz RF cavities used in Fermilab's Recycler Ring upgrade, enabling precise frequency tuning for slip stacking.

Contribution

It introduces a novel YIG tuner design with a 10 kHz tuning range for RF cavities, including detailed measurements and high power test results.

Findings

Successful implementation of a YIG tuner with 10 kHz tuning range

High power testing demonstrating tuner reliability

Effective tuning mechanism for Recycler Ring RF cavities

Abstract

For NOvA and future experiments requiring high intensity proton beams, Fermilab is in the process of upgrading the existing accelerator complex for increased proton production. One such improvement is to reduce the Main Injector cycle time, by performing slip stacking, previously done in the Main Injector, in the now repurposed Recycler Ring. Recycler slip stacking requires new tuneable RF cavities, discussed separately in these proceedings. These are quarter wave cavities resonant at 52.809 MHz with a 10 kHz tuning range. The 10 kHz range is achieved by use of a tuner which has an electrical length of approximately one half wavelength at 52.809 MHz. The tuner is constructed from 3 1/8 inch diameter rigid coaxial line, with 5 inches of its length containing perpendicularly biased, Al doped Yttrium Iron Garnet (YIG). The tuner design, measurements, and high power test results are presented.