Many experiments in the frontiers of high energy physics require high luminosity as well as high energy beams. For proton-antiproton colliders, this requirement leads to the need for antiproton storage rings with smaller emittance, capable of operation at high current, and with the avoidance of catastrophic beam loss. Experiments at both CERN and Fermilab have shown that trapped ions in the antiproton accumulator (AA) are associated with limitation on these operational parameters. In this investigation, theoretical studies leading to improved methods of trapped ion removal are considered. The work will be done in collaboration with ongoing experimental work at Fermilab. The proposed scheme will optimize existing beam shaking techniques in the collective plasma regime appropriate to highly stacked beams. Phase I will develop a Vlasov theory of trapped ion equilibria, collective modes and the corresponding quasilinear (QL) theory including Landau wave-particle interaction with the trapped ions. The QL theory will yield trapped ion removal rates for the Fermilab AA as a function of collective mode amplitudes excited by beam shaking, and enable the calculation of the associated shaker power requirements. The Phase I effort will set up all necessary tools for complete identification and optimization of strategies for beam shaking. Assessment of possible scenarios (e.g., choice of collective mode, operating point for beam/trapped-ion coupling, and time sequencing of shaker power and frequency modulation) will begin in Phase I and is the major goal of Phase II, which will enable the design of an optimized shaker. Some of the techniques developed will be applicable more generally to other accelerators with negatively charged beams. Anticipated Results /Potential Commercial Applications as described by the awardee:This work will enable the design (of new equipment, if needed) and the operational scenarios for optimal removal of trapped ions by beam shaking techniques. It will extend previous single particle descriptions of beam shaking and trapped ion removal to the collective plasma regime appropriate to Fermilab AA operation with highly stacked beams. The end result will be a significant new tool for obtaining higher antiproton beam currents, lower beam emittance, and therefore improved performance of the accelerator as a whole.
