Study of high pressure gas filled RF cavities for muon collider

TL;DR

This paper investigates high-pressure hydrogen gas filled RF cavities for muon colliders, demonstrating mitigation of plasma loading effects with electronegative gas doping, enabling effective operation in strong magnetic fields.

Contribution

It presents experimental results on plasma loading mitigation in gas filled RF cavities using electronegative doping, advancing muon collider RF technology.

Findings

Gas filled RF cavities can operate effectively with muon beams.

Electronegative gas doping significantly reduces plasma loading.

The cavity functions in strong magnetic fields as required for muon colliders.

Abstract

Muon collider is a considerable candidate of the next-generation high-energy lepton collider machine. Operating an RF cavity in a multi-Tesla magnet is a critical requirement in a muon accelerator and a cooling channel. However, the maximum RF gradient in a vacuum RF cavity is strongly limited by an external magnetic field. Dense hydrogen gas filled RF cavity has been proposed since it is functional of generating a high RF accelerating gradient in a strong magnetic field and making an ionization cooling process at the same time. A critical issue of the cavity is a beam- induced plasma that consumes a considerable amount of RF power. The gas filled RF test cell was made and measured the RF loading due to a beam-induced plasma by using an intense proton beam at Fermilab. By doping an electronegative gas in dense hydrogen, the plasma loading effect is significantly mitigated. The result shows that the cavity is functional with a muon collider beam. Recent progress is shown in this presentation.