• Z. Liu
  IUCF, Bloomington, Indiana
• S.M. Cousineau, J. Galambos, J.A. Holmes, M.A. Plum
  ORNL, Oak Ridge, Tennessee
• X. Huang
  SLAC, Menlo Park, California

Recently, discrepancies between model-based and observed linear optics, such as the tune and the closed orbit, have been observed in the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Accurate accelerator modeling is very important for machine control during the ongoing power ramp up. The Orbit Response Matrix (ORM) method is applied here to find and correct errors in the linear optics of the SNS ring. With the closed orbit data (4472 data points), we are able to calibrate the strength of the steering magnets, the BPM gain factors, and 6 quadrupole power supplies. Current results and remaining challenges will be presented and discussed.