• Z. Liu
  IUCF, Bloomington, Indiana
• S.M. Cousineau, J.A. Holmes, M.A. Plum
  ORNL, Oak Ridge, Tennessee

Funding: Division of Materials Science, U.S. Department of Energy, under contract number DE-AC05-96OR22464 with UT-Battelle Corporation for Oak Ridge National Laboratory

In order to achieve a more robust and optimal performance, the difference between the real machine and its underlying model should be understood and eliminated. Discrepancies between the measuremed and predicted linear optics suggest possible errors of the focusing magnets and diagnostic devices. To find and correct those errors, a widely used method, orbit response matrix (ORM)* approach is applied to the SNS storage ring, which successfully brings the tune deviation from 3% to 0.1%, improves horizontal beta beating from 15% to 3%, and perfectly flattens the orbit. In this article, we discussed the progress and possible future improvements with the SNS ring optics correction.

*J. Safranek, "Experimental determination of storage ring optics using closed orbit response measurements", Nucl. Inst. and Meth. A388, (1997), pg. 27

• J.A. Holmes, S.M. Cousineau, V.V. Danilov
  ORNL, Oak Ridge, Tennessee
• Z. Liu
  IUCF, Bloomington, Indiana

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

During one of the high beam intensity runs in SNS, a coasting beam instability was observed in the ring when the beam was stored for 10000 turns. This instability was observed at an intensity of about 12 microcoulombs and was characterized by a frequency spectrum peaking at about 6 MHz. A likely cause of the instability is the impedance of the ring extraction kickers. We carry out here a detailed benchmark of the observed instability, uniting an analysis of the experimental data, a precise ORBIT Code tracking simulation, and a theoretical estimate of the observed beam instability.