Electron Cloud Issues for the APS Superconducting Undulator

The Advanced Photon Source (APS) Upgrade calls for the design and development of a superconducting undulator (SCU) at APS, a 7-GeV electron synchrotron. The heat load is a critical parameter in designing the cryosystem for the SCU. Operation of an SCU at ANKA shows a heat load and pressure rise that may be consistent with beam-induced multipacting from an electron cloud. For this reason, a study was undertaken to minimize the contribution to the heat load by a possible electron cloud at the APS. We focused on analyzing the photon absorption on the chamber walls that can potentially give rise to photoelectrons. Preliminary tracking of the photon flux using the code synrad3d for the APS SCU chamber is presented, and possible ways to mitigate the photoelectrons are discussed.