Beam-induced radiation heating on the superconducting undulator at the advanced photon source

In January 2013 the Advanced Photon Source (APS), a 7 GeV synchrotron X-ray source, commissioned a Superconducting Undulator (SCU). The superconducting magnet is thermally isolated from the beam vacuum chamber, which absorbs the beam-induced heating. Previous beam induced heat load studies at other laboratories had not included a robust calculation of radiation heating from the upstream dipole magnet. The mitigation of the radiation heating mechanism, and production of photoelectrons to seed an electron cloud was studied for this thesis. An analytical model was developed to predict the radiation heat load on the SCU chamber. This model was benchmarked with ray tracings and simulations. Results from this synchrotron radiation model were used to guide the design of the installed SCU beam chamber. A 3D Monte-Carlo simulation on synchrotron radiation on the beam chamber was developed. The model considered the effect of diffuse scattering and complex chamber geometries. It was found that a simulation assuming no photon scattering gave a power that agreed within 0.4% of the analytical model. Comparison between analytical calculations and measured temperature rise on the installed SCU show the analytical model agrees with the measured temperature rise within 20%. Previous models of similar superconducting devices in accelerators have reached at best 200% difference between the measured and modeled heat load. The beam heat load model presented in this thesis represents a significant improvement in modeling of superconducting devices in high energy particle accelerators. In addition to heating the SCU chamber, absorbed photons produce photoelectrons which seed electron clouds, another source of beam induced heating. Measurements of the technical aluminum samples show peaks in the quantum efficiency for photon energies equal to the K edges of oxygen, carbon, and aluminum. These results can be added to electron cloud simulation codes to improve simulation results.