Vacuum chamber thermal protection for the APS

The authors summarize the results of a task group that studied the vacuum-chamber thermal protection problem for the Advanced Photon Source (APS). It is pointed out that the high-power-density photon beams in the proposed next generation of synchrotron light sources introduce new risks to the integrity of the ring vacuum chambers. In these machines, power densities are such that vacuum chamber cooling is unable to reduce the risk of rapid penetration of the chamber. Two general methods have been studied for providing passive protection of the vacuum chamber. These include limiting of the power supplies that could missteer the beam and insertion of limiting apertures using beam scrapers that prevent the photon beam from illuminating the vacuum chamber. The APS uses the former during construction and will be able to implement the latter at a future time if the potential risk to the chamber warrants additional protection