ORNL RAD, Oak Ridge, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
I will present results of experiments at the Spallation Neutron Source to implement a method of phase space painting we refer to as ¿eigenpainting¿, in which beam is injected along one eigenvector of the transfer matrix of a ring with full coupling. The method and resultant distribution were initially proposed by Danilov almost to linearize the space charge force, minimizing space charge tune spread. In the theoretically ideal case this so-called Danilov distribution has uniform charge distribution, elliptical envelope in real-space, and a vanishing 4D transverse emittance. Such a beam can be maintained throughout injection. The Danilov distribution has implications for increasing beam intensity beyond the conventional space charge limit through a reduction of both tune spread and shift, and increasing collider performance. This talk will present current limits on beam quality, and details of the preparation of the optics in the SNS accumulator ring, including the installation of new solenoid magnets. The status of experiments to improve beam quality and characterize the interesting dynamical implications of the defining features of the Danilov distribution will also be discussed.
BNL, Upton, New York, USA
The RHIC collider physics program, in particular its polarized proton and low energy heavy ion components, present unique challenges for maintaining collider performance in the presence of space charge effects. Polarized beam performance is especially sensitive to emittance increases, since they decrease both the luminosity and polarization. Operation of the collider with gold beams at sub-injection energies (down to 3.85 GeV/n Au) with space charge tune shifts up to 0.1 required special care to optimize both the ion lifetime and its interaction with the electron-beam cooler. We describe the operational experience in these modes and some of the mitigation efforts.