TUP2WD01
ANL, Argonne, Illinois, USA
Current undulator XBPMs in the Advanced Photon Source (APS) can handle limited beam power and have strong bend magnet background. The next generation XBPM will separate the power-handling elements from the signal detectors using x-ray fluorescence from aperture components and x-ray scattering from low-Z blades. They showed distinct design advantages: (1) The water-cooled aperture components greatly enhance power-handling capacity, up to the APS-U 20-kW undulators. (2) Additional x-ray optics, such as pinhole-camera, enables center-of-mass, gap-independent measurements. (3) Proper beam-intercepting elements tailor the XBPM spectral properties and suppress the background, improving undulator measurement accuracy. (4) Using limiting apertures as the XBPM allows aiming the undulator beam reliably at the aperture during user operations, eliminating the common alignment issue between the aperture and the XBPM. In this report, we discuss the x-ray physics, mechanical design, computer simulation and beam measurements of these x-ray beam position monitors for the APS Upgrade. Possible applications to the free electron laser will be discussed.
