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Murphy, J. B.

Paper Title Page
TUPMS071 Upgrade Alternatives for the NSLS Superconducting Wiggler 1335
  • M. G. Fedurin, P. Mortazavi, J. B. Murphy, G. Rakowsky
    BNL, Upton, Long Island, New York
  The superconducting wiggler (SCW) with 4.2 Tesla field in 5 main poles has been in operation on the NSLS X-ray storage ring for more than 20 years. The inefficient cryogenic system of this wiggler uses a closed-cycle refrigerator requiring constant maintenance. It is possible to replace this insertion device with a 13-pole SCW originally built by Oxford Instruments. The cryostat of this device could be upgraded to reduce the liquid He consumption using cryocoolers, thereby greatly reducing the refrigerator operating expense. A second option is a new design of a SCW with a magnetic period and number of poles appropriate to the current users needs. All these upgrade possibilities will be described in the paper.  
TUPMS088 Efficiency Enhancement Experiment with a Tapered Undulator in a Single-pass Seeded FEL at the NSLS SDL 1371
  • T. Watanabe, D. A. Harder, R. K. Li, J. B. Murphy, G. Rakowsky, Y. Shen, X. J. Wang
    BNL, Upton, Long Island, New York
  Funding: This work is supported by the Office of Naval Research under contract No. N0002405MP70325 and U. S. Department of Energy under contract No. DE-AC02-98CH1-886.

We report the experimental characterization of the FEL efficiency enhancement using a tapered undulator in a single-pass seeded FEL amplifier at the NSLS SDL. The last 3 m of the 10 m NISUS undulator was linearly tapered so that the magnetic field strength at the end of the undulator was reduced by 5 %. The FEL energy gain along the undulator was measured for both the tapered and un-tapered undulator. The FEL energy with the taper was measured to be about 3.2 times higher than that without the taper. We also experimentally characterized the spectrum and the transverse distribution of the FEL light for both the tapered and un-tapered undulator. The experimental results are compared with the numerical simulation code, GENESIS 1.3.