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Schroeder, R.

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MOPAS095 Study of the RHIC BPM SMA Connector Failure Problem 649
 
  • C. J. Liaw, R. Schroeder, R. Sikora
    BNL, Upton, Long Island, New York
 
  About 730 cryogenic beam position monitors (BPMs) are mounted on the RHIC CQS and triplet superconducting magnets. Semi-rigid coaxial cables bring the electrical signal from BPM feedthroughs to outside flanges at ambient temperature. Each year approximately 10 cables fail during RHIC operations. The connection usually fails at the warm end of the cable, either from solder joint failure or retraction of the center conductor in the SMA connector. Finite element analyses were performed to understand the solder joint failure mechanism. Results showed that (1) the SMA center conductor can separate from the mating connector due to the thermal retraction,(2) the maximum thermal stress at the warm end solder joint can exceed the material strength of the Pb37/Sn63 solder material, and (3) magnet ramping frequency (~10 Hz) during the machine startup can possibly resonate the coaxial cable and damage the solder joint. This failure problem can be resolved by repairing with silver bearing solder material (a higher strength material) and crimping the cable at the locations close to the SMA connector to prevent center conductor retraction.  
TUOCC02 Progress in Tune, Coupling, and Chromaticity Measurement and Feedback during RHIC Run 7 886
 
  • P. Cameron, J. Cupolo, W. C. Dawson, C. Degen, A. Della Penna, L. T. Hoff, Y. Luo, A. Marusic, R. Schroeder, C. Schultheiss, S. Tepikian
    BNL, Upton, Long Island, New York
  • M. Gasior
    CERN, Geneva
 
  Funding: US DOE

Tune feedback was first implemented in RHIC in 2002 as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End. Continuous measurement of all projections of the betatron Eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort. The results of investigations of power line harmonics in RHIC are presented elsewhere in these proceedings.

 
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