ORNL, Oak Ridge, Tennessee
Operating at 0.5 MW beam power on target, the Spallation Neutron Source (SNS) is already the world's most powerful pulsed neutron source. However, we are only one third of the way to full power. As we ramp toward full power, the control of the beam and beam loss in the ring will be critical. In addition to practical considerations, such as choice of operating point, painting scheme, and rf bunching, it may be necessary to understand and mitigate collective effects due to space charge, impedances, and electron clouds. In dedicated high intensity beam study shifts, we have already observed resistive wall, impedance driven, and electron cloud activity. The analysis and simulation of this data are important ongoing activities at SNS. This talk will discuss the status of this work, as well as other considerations necessary to the successful full power operation of SNS.
BNL, Upton, Long Island, New York
Intra-beam scattering (IBS) is the limiting factor of the luminosity lifetime for RHIC operation with heavy ions. Over the last few years the process of IBS was carefully studied in RHIC with dedicated IBS measurements and their comparison with the theoretical models. Recently, in order to suppress transverse IBS growth, a new lattice was designed and implemented in RHIC, which lowered the average arc dispersion by 30%. This lattice became operational during RHIC Run-8. We review the IBS suppression mechanism, IBS measurements before and after the lattice change, and comparisons with predictions.
LANL, Los Alamos, New Mexico
University of Tennessee, Knoxville, Tennessee
TRIUMF, Vancouver
ORNL, Oak Ridge, Tennessee
KEK, Ibaraki
At the 39th ICFA Advanced Beam Dynamics Workshop HB 2006 we reported on first results of a test of nanocrystalline diamond foils developed at ORNL under operational conditions at the Los Alamos Proton Storage Ring (PSR). We have continued these tests during the 2006 and 2007 run cycles and have been able to compare the diamond foils with the foils that are normally in use in PSR, which were originally developed by Sugai at KEK. We have gathered valuable information regarding foil lifetime, foil related beam loss and electron emission at the foil. Additional insight was gained under unusual beam conditions where the foils are subjected to higher temperatures. In the 2007 run cycle we also tested a Diamond-like-Carbon foil developed at TRIUMF. A Hybrid-Boron-Carbon foil, also developed by Sugai, is presently in use with the PSR production beam. We will summarize our experience with these different foil types and offer an outlook for future foil activities at PSR.
ORNL, Oak Ridge, Tennessee
Beam loss is higher than expected in the Ring injection section and in the injection dump beam line. The primary causes are fairly well understood, and we have made some equipment modifications to reduce the loss. In the ring extraction beam line the beam distribution exhibits cross-plane coupling (tilt), and the cause has been traced to a large skew-quadrupole component in the extraction Lambertson septum magnet. In this talk we will discuss the issues surrounding the ring injection and extraction systems, the solutions we have implemented to date, and our plans for future improvements.