• J. G. Wang
  ORNL, Oak Ridge, Tennessee

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

3D computer simulations are performed to study magnetic field qualities in the SNS ring extraction Lambertson septum magnet. This work is motivated by the existence of a significant skew quad term in the magnet that has been identified as the source of causing a beam profile distortion on the target. The skew quad term is computed with different methods in simulations and is compared to measurement data. The origin of the large skew quad term is thoroughly investigated. The remedy for minimizing the skew quad term by modifying the magnet is also proposed. Particle tracking has been performed to verify the beam profile evolution through the existing and modified septum. The magnetic interference to the septum performance from an adjacent quadrupole is also assessed. This paper reports our simulation techniques and major results.

• Y. Zhang, C.K. Allen, J. Galambos, J.A. Holmes, J. G. Wang
  ORNL, Oak Ridge, Tennessee

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

The Spallation Neutron Source (SNS) linac system is designed to deliver 1 GeV pulsed H^- beams up to 1.56 MW for neutron production. As beam power was increased from 10 kW to 660 kW in less than three years, beam loss in the accelerator systems – particularly in the superconducting linac (SCL), became more significant. In the previous studies, unexpected beam loss in the SCL was mainly attributed to longitudinal problems. However, our most recent simulations have focused on beam transverse effects. These include multipole components from magnet imperfections and dipole corrector windings of the linac quadrupoles. The effect of these multipoles coupled with other errors will be discussed.