• 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.