Application of MO-type Vacuum Flange to Accelerator Beam Duct

The MO-type vacuum flange, which can provide a gapless connection between flanges, was studied experimentally aiming to apply it to the beam duct of high-current accelerators. A test flange showed a good vacuum sealing property although the flange had a complex aperture, that is, a combination of a circle and a rectangle. The vacuum sealing was successfully achieved with a reasonable fastening force, and was kept even after a baking at 250°C for 24 hours. The structural analysis well reproduced the observed deformation of flange, and utilized to optimize the flange structure. The MO-type vacuum flange was found to be a promising one for the connection flanges of the beam duct with a complicated aperture in the future accelerators.