• 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.

• Y. Zhang, Z. Liu, R. Remec
  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 combined time required for diffusion release from target materials and effusive-flow of short-lived ion species must be minimized at ISOL based radioactive ion beam (RIB) facilities. Computational simulation studies with state-of-the-art codes offer cost effective means for designing targets with optimized diffusion release properties and vapor transport systems with short path lengths, as required for such applications. To demonstrate the power of the technique for designing optimum thickness targets, analytic solutions to the diffusion equation are compared with those obtained from a finite-difference code for radioactive particle release from simple geometries. The viability of the Monte Carlo technique as a practical means for optimally designing vapor transport systems is demonstrated by simulating the effusive-flow of neutral particles through several complex vapor transport systems. Important issues which affect the yield rates of short-lived species generated in high power ISOL targets are also discussed.