• B.X. Yang, W. Berg, A.R. Brill, J.C. Dooling, L. Erwin, A.F. Pietryla
  ANL, Argonne

For reliable radiation dosimetry of undulator magnets, a beam loss monitor (BLM) covering a large solid angle from the point of beam losses is highly desirable. A BLM that uses a Cherenkov radiator plate wrapping around the beam pipe is utilized in the Linac Coherent Light Source (LCLS) undulator systems, and a similar BLM geometry is currently being tested for the Advanced Photon Source (APS) undulators. We report on measurements made with large solid-angle BLMs recently installed in the APS storage ring (SR) and the booster-to-SR transfer line (BTS) to assess the following design and performance characteristics: (1) relative sensitivity of the Cherenkov detector as a function of the transverse position of electron entry into the quartz radiator; (2) signal intensity as a function of the detector distance from the nominal beam loss location at the undulator vacuum chamber entrance; and (3) the effect of incorporating different tungsten/lead enhancers upstream of the radiator. The measured data will be compared with numerical simulation of the beam loss processes.

• R.M. Lill, J.T. Collins, G. Decker, L. Erwin, J.Z. Xu, B.X. Yang
  ANL, Argonne

As the Advanced Photon Source (APS) prepares for a large-scale upgrade, many of the fundamental limitations on beam stability have to be identified. Studies have been conducted to measure thermal mechanical effects of both the water and air handling systems impacting insertion device vacuum chambers (IDVES). Mechanical stability of beam position monitor pickup electrodes mounted on these small-gap IDVES places a fundamental limitation on long-term x-ray beam stability for insertion device beamlines. Experiments have been conducted on an ID vacuum chamber indicating that the BPM blocks are moving with water temperature cycles at the level of 10 microns/degree C. Measurements and potential engineering solutions will be described.