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Liaw, C. J.

Paper Title Page
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.  
TUPAS020 An 8 GeV H- Multi-turn Injection System for the Fermilab Main Injector 1700
  • D. E. Johnson
    Fermilab, Batavia, Illinois
  • J. Beebe-Wang, C. J. Liaw, D. Raparia
    BNL, Upton, Long Island, New York
  Funding: Work supported by Universities Research Association, Inc. under contract No. DE-AC02-76CH03000 with the U. S. Dept. of Energy.

The technique for H- charge exchange for multi-turn injection utilizing stripping foils in the energy range of a few hundred MeV has been used at many labs for decades and most recently up to 1 GeV at the SNS. Utilization the beam from the proposed Proton Driver* would permit the extension of this technique up to 8 GeV. The injection layout and required accelerator modifications are discussed. Results from transverse and longitudinal simulations are presented.

* W. G. Foster and J. A. MacLachlan, "A Multi-mission 8 GeV Injector Linac as a Fermilab Booster Replacement", Proc. Of LINAC-2002, Gyeongju, Korea, p.86.