ANL, Lemont, Illinois, USA
The Advanced Photon Source Upgrade (APS-U) storage ring arc consists of a diverse system of nar-row-aperture chambers in compact magnet assemblies with gaps often less than 1 mm. The vacuum system contains two stainless steel pumping crosses and two keyhole-shaped vacuum chambers, as well as eight non-evaporative getter (NEG) coated aluminum cham-bers and crosses per sector (40 total sectors). Each chamber contains a 22 mm diameter electron beam aperture and the keyhole components also feature a photon extraction antechamber. Each design balances functionality, manufacturability, and installation needs. The design process was aided by a flexible CAD skeleton model which allowed for easier adjustments. Synchrotron radiation heat loads applied to inline chamber photon absorbers and photon extraction beam envelopes were determined via a 3D ray tracing CAD model. The inline photon absorber and the key-hole shapes were optimized using iterative thermal-structural FEA. Focus was put on mesh quality to mod-el the <0.5 mm tall synchrotron radiation heat load absorbed across the length of the chamber to verify cooling parameters. The design process also required careful routing of the water system and vacuum pumps. The designs incorporate beam physics con-straints of the inline absorbers, cross-housed discrete absorbers, and pumping slots.
