Spallation Neutron Source linac vacuum seal design and testing

Optimum seal selection with respect to vacuum performance, RF electrical performance, life, cost, reliability, and case of installation is of primary importance. This report summarizes an investigation of metallic vacuum seals including the C-seal, energized spring seal, Helicoflex copper delta seal, aluminum delta seal, delta seal with limiting ring, and a prototype copper diamond seal. This study was conducted to support the drift tube linac (DTL) and coupled cavity linac (CCL) design efforts for the Spallation Neutron Source (SNS) project. A series of vacuum leak rate tests using necessary reduced thickness flange designs has been completed. Copper plated stainless steel flanges, necessary for flanged joints intersecting RF cavities, have also been studied and tested. Detailed structural modeling of the CCL bridge coupler seal and flange has also been completed to verify flange structural integrity and appropriate seal compressive loading.