RF Cavities For The Muon and Neutrino Factory Collaboration Study

TL;DR

This paper discusses the development and testing of RF cavities designed for muon cooling in a neutrino factory or muon collider, focusing on two cavity types at different frequencies and their cold measurement results.

Contribution

It introduces two RF cavity designs for muon cooling at Fermilab and provides cold measurement data demonstrating their performance.

Findings

The 805 MHz cavity is a non-periodic pi-mode with shaped iris openings.

The 201 MHz cavity uses hollow metal tubes to increase shunt impedance.

Cold measurement data confirms cavity performance.

Abstract

A multi-laboratory collaboration is studying the feasibility of building a muon collider, the first phase of which maybe a neutrino factory. The phase space occupied by the muons is very large and needs to be cooled several orders of magnitude for either machine, 100,000 to 1 million for the collider and ten to 100 for the factory. Ionization cooling is the base line method for muon cooling. This scheme uses hydrogen absorbers and rf re-acceleration in a long series of magnetic focusing channels to cool the muons. At Fermilab two rf cavity types are under study to provide the required cooling rf re-acceleration, a 805 MHz high gradient cavity for the collider and a 201 MHz high gradient cavity for the neutrino factory. The 805 MHz cavity currently under going cold testing is a non-periodic pi-mode cavity with the iris openings shaped to follow the contour of the beam. The 201 MHz cavity uses hollow thin metal tubes over the beam aperture to terminate the field in a pill-box type mode to increase its shunt impedance. This is possible because muons have little interactions with thin metal membranes. Details of these cavities and cold measurement data will be presented.