High-pressure RF cavities for muon beam cooling

Abstract

An 800 MHz RF test cell filled with high pressure gaseous hydrogen was used to study RF breakdown phenomena in hydrogen and helium gases as a function of pressure and temperature. The maximum achieved RF surface gradient was 80 MV/m at 1.83 MPa and 77 K, where the breakdown of the molybdenum electrodes of the test cell limited the study of the linear dependence of the breakdown voltage on gas density known as Paschen's Law. The test cell conditioning was also much faster in gas than in vacuum cavities. The high gradient and fast conditioning are encouraging results for the use of high-pressure RF cavities for ionization cooling of muon beams for muon colliders, neutrino factories, and intense sources.