• B. Han, M. P. Stockli
  ORNL, Oak Ridge, Tennessee

Beam envelope calculations show that a solenoid-drift-(singlet quad)-(sector dipole)-(singlet quad)-drift-solenoid LEBT allows for transporting 65-kV, high-current H^- beams with smaller beam radii than the initially-explored (doublet quad)-drift-(double-focusing dipole)-drift-solenoid configuration. In addition, it appears that the new configuration is more robust because it allows for perfect matching of the final beam parameters for broad ranges of the parameters describing the lattice and the input beam. Such a LEBT with a dipole (switching-) magnet is required to assure meeting the 99% ion source availability requirement after upgrading the power of the Spallation Neutron Source. The SNS power upgrade will roughly double the neutron flux by increasing the proton beam energy from 1 to 1.3 GeV and by increasing the LINAC beam peak current from 38 to 59 mA. Because the RFQ losses increase with beam current and emittance, the RFQ input current needs to be increased from 41 to 67 mA if the normalized emittance can be maintained at 0.2 mm-mrad, or to 95 mA if the emittance increases to 0.35 mm-mrad.

• M. P. McCarthy, D. E. Anderson, I. E. Campisi, F. Casagrande, R. I. Cutler, G. W. Dodson, J. Galambos, D. P. Gurd, Y. W. Kang, K.-U. Kasemir, S.-H. Kim, H. Ma, B. W. Riemer, J. P. Schubert, M. P. Stockli
  ORNL, Oak Ridge, Tennessee

Increasing the pulse repetition rate (PRR) of the SNS Linac to its designed maximum of 60 Hz to provide 1.4 MW of beam on target is in progress. Operation above 60 Hz in the future to provide beam to a second target is also being considered. Increasing the PRR to 80 Hz would allow the additional pulses to be diverted to a second target. This paper discusses the impact of increasing the PRR on the SNS infrastructure including Radio Frequency (RF) systems and structures, the ion source, cryogenics, controls and the target.

• A. V. Aleksandrov, S. Assadi, W. Blokland, P. Chu, S. M. Cousineau, V. V. Danilov, C. Deibele, J. Galambos, S. Henderson, D.-O. Jeon, M. A. Plum, A. P. Shishlo, M. P. Stockli, Y. Zhang
  ORNL, Oak Ridge, Tennessee

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H^- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5 MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006 and beam power is being gradually ramped up toward the design goal. Operational experience with the injector and linac will be presented including chopper performance, transverse emittance evolution along the linac, and the results of a beam loss study.

• R. F. Welton, J. R. Carmichael, J. Carr, D. W. Crisp, R. H. Goulding, Y. W. Kang, N. P. Luciano, S. Murray, M. P. Stockli
  ORNL, Oak Ridge, Tennessee

ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725