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Crofford, M. T.

Paper Title Page
TUP002 High-Dynamic-Range Current Measurements in the Medium-Energy Beta Transport Line at the Spallation Neutron Source 244
 
  • D. A. Bartkoski, A. V. Aleksandrov, D. E. Anderson, M. T. Crofford, C. Deibele, S. Henderson, J. C. Patterson, C. Sibley, A. Webster
    ORNL, Oak Ridge, Tennessee
  
  It is desired to measure the effectiveness of the LEBT (low energy beta transport) chopper system. Since this chopper is required to chop the H- beam to a 1% level, it is required therefore to accurately measure the beam during the chop. A system is developed with a high dynamic range that can both accurately measure the beam to tune the chopper system as well as provide an input to the MPS (machine protection system) to stop the beam in the event of a chopper system failure. A system description, beam based calibration, and beam measurements are included.  
THP005 Digital Control of Cavity Fields in the Spallation Neutron Source Superconducting Linac 571
 
  • H. Ma, M. S. Champion, M. T. Crofford, K.-U. Kasemir, M. F. Piller
    ORNL, Oak Ridge, Tennessee
  • A. Brandt
    DESY, Hamburg
  • L. R. Doolittle, A. Ratti
    LBNL, Berkeley, California
  
  Control of the pulsed RF cavity fields in the Spallation Neutron Source (SNS) superconducting Linac uses both the real-time feedback regulation and the pulse-to-pulse adaptive feed-forward compensation. This control combination is required to deal with the typical issues associated with superconducting cavities, such as the Lorentz force detuning, mechanical resonance modes, and cavity filling. The all-digital implementation of this system provides the capabilities and flexibility necessary for achieving the required performance, and to accommodate the needs of various control schemes. The low-latency design of the digital hardware has successfully produced a wide control bandwidth, and the developed adaptive feed forward algorithms have proved to be essential for the controlled cavity filling, the suppression of the cavity mechanical resonances, and the beam loading compensation. As of this time, all 96 LLRF systems throughout the Linac have been commissioned and are in operation.  
THP029 Development of an RFQ Input Power Coupling System 634
 
  • Y. W. Kang, A. V. Aleksandrov, M. M. Champion, M. S. Champion, M. T. Crofford, P. E. Gibson, T. W. Hardek, P. Ladd, M. P. McCarthy, D. Stout, A. V. Vassioutchenko
    ORNL, Oak Ridge, Tennessee
  • H. L. Haenichen
    TU Darmstadt, Darmstadt
  
  An RF input coupler system is designed, manufactured, and tested for future upgrade of the coupling system of the RFQ in the SNS linac. The design employs two coaxial loops in vacuum side of two coaxial ceramic windows through coaxial transmission lines that are connected to a magic-T waveguide power splitter for 402.5 MHz operation. The couplers will be used with up to total 800 kW peak power at 8% duty cycle. RF properties of the system and fabricated structure along with vacuum and thermal properties are discussed. Two couplers are joined together through an evacuated bridge waveguide for high power RF processing. Result of the high power conditioning that is performed in the RF test facility of the SNS is presented.  
THP081 Study on Fault Scenarios of Coaxial Type HOM Couplers in SRF Cavities 770
 
  • S.-H. Kim, I. E. Campisi, F. Casagrande, M. S. Champion, M. T. Crofford, D.-O. Jeon, Y. W. Kang, M. P. McCarthy, D. Stout
    ORNL, Oak Ridge, Tennessee
  
  Coaxial type couplers are adopted in many superconducting radio-frequency (SRF) cavities to suppress higher order modes for beam dynamics and cryogenic loads issues. HERA (Hadron-Electron Ring Accelerator) and TTF (Tesla Test Facility) are equipped with this type coupler and showed successful performances. It is, however, under suspicion that a limitation or a fault could be initiated from this type of coupler at certain combinations between cavity operating conditions and engineering designs of the coupler. Some possible scenarios are summarized and also some observations in the SNS (Spallation Neutron Source) SRF cavities are also reported.