Mechanical analysis of the PEFP medium-beta SRF cavity

Abstract

For the extension of the existing 100-MeV PEFP (Proton Engineering Frontier Project) proton linac up to a 1-GeV machine, a study of the RF linac based on RF superconductivity technology is underway. The operating frequency of the PEFP SCL (superconducting linac) is 700 MHz, which is determined by the fact that the frequency of the existing normal conducting linac is 350 MHz. A preliminary study of the beam dynamics shows that two types of cavities with geometrical betas of 0.50 and 0.74 can cover the entire energy range from 100 MeV to 1 GeV. The baseline design of the SRF (superconducting radio frequency) cavity is an elliptical shape with a reduced beta. The reduced-beta elliptical cavity is vulnerable to structural instability; therefore, mechanical analyses, such as vacuum pressure deformation, static Lorentz force detuning and natural mode frequency analyses, were performed by using a finite-element-method code. The mechanical analysis procedures and the results will be given in this paper.