Operation of normal-conducting RF cavities in multi-tesla magnetic fields for muon ionization cooling: a feasibility demonstration

TL;DR

This paper demonstrates the first stable operation of high-gradient copper RF cavities in multi-tesla magnetic fields, addressing a key technical challenge in muon ionization cooling for particle accelerators.

Contribution

It introduces a novel solution enabling stable RF cavity operation in strong magnetic fields, crucial for advancing muon cooling technology.

Findings

Stable operation of RF cavities above 50 MV/m in 3 T magnetic fields.

Elimination of a major technical risk in ionization cooling channels.

Potential for longer, more efficient muon cooling channels.

Abstract

Ionization cooling is the preferred method for producing bright muon beams. This cooling technique requires the operation of normal conducting, radio-frequency (RF) accelerating cavities within the multi-tesla fields of DC solenoid magnets. Under these conditions, cavities exhibit increased susceptibility to RF breakdown, which can damage channel components and imposes limits on channel length and transmission efficiency. We present a solution to the problem of breakdown in strong magnetic fields. We report, for the first time, stable high-vacuum, copper cavity operation at gradients above 50 MV/m and in an external magnetic field of three tesla. This eliminates a significant technical risk that has previously been inherent in ionization cooling channel designs.