Design and development of vacuum chamber for superconducting undulator at IHEP

Superconducting undulators (SCUs) are crucial components for advanced photon sources and have broad applications. IHEP is currently developing SCU, which requires a vacuum chamber to provide a beam path and protect the superconducting magnets from image currents induced by the beams. However, due to the narrow magnetic gap and low temperature of the SCU, designing and processing its vacuum chamber presents challenges in terms of mechanical design, positioning, and intercepting synchrotron radiation that could damage the sensitive superconducting magnets. The SCU vacuum chamber is divided into three parts based on location and function: chamber inside the cryostat as well as upstream and downstream chambers outside it. The complex fit of the constant aperture vacuum chamber inside the cryostat with both magnets and cryostat ensures high-current operation while also safely managing dynamic heat loads imposed by beams. Using an SCU operating on HEPS as an example shows how smooth transitions between upstream/downstream and storage ring chambers effectively absorb synchrotron radiation to protect magnets and downstream equipment from damage caused by synchrotron radiation exposure. Simulations are performed to check the possible effects of synchrotron radiation on the mechanical properties, the ultimate vacuum of these chambers and to calculate the beam impedance. Finally, two solutions for using the vacuum chamber as a channel for measuring the magnetic field of the SCU in the operating state are discussed.