Static Magnetization Properties Of AL800 Garnet Material

TL;DR

This paper investigates the static magnetization properties of AL800 garnet material to optimize the design of a wide-range tunable RF cavity for Fermilab's Booster, aiming to prevent RF losses due to magnetic property variations.

Contribution

It provides detailed measurements of AL800 garnet's magnetic properties under conditions relevant to RF cavity tuning, aiding in design optimization.

Findings

Magnetic properties vary with magnetic field strength.

Non-uniform magnetic fields can increase RF losses.

Data supports improved tuner design considerations.

Abstract

A second harmonic tunable RF cavity is being developed for the Fermilab Booster. This device, which promises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the magnetic field in the garnet comes fairly close to the gyromagnetic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet material; thus, it is important to know the static magnetic properties of the material to avoid significant increase in the local RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the magnetic properties of the AL800 garnet material used to build the tuner of the cavity.