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Electron-Cloud R&D



We are presently proposing to design, and later build, a feedback system to control the electron-cloud instability observed at the SPS when operated with LHC beams. Such a feedback system would allow the SPS to inject beams more reliably and with fewer losses into the LHC, and would be mandatory for the future luminosity upgrade of the LHC. This proposal has been submitted to the US-LARP program in collaboration with SLAC.


With our 2D and 3D simulation capability, which has several numerical algorithms not in use anywhere else, we are uniquely able to contribute to the important effort to model electron cloud efforts at the ILC. Our recent simulation work has led to the discovery of new resonances in electron cloud dynamics for ILC parameters, as well as the benchmarking of our 2D and 3D codes. These resonances can be expected in magnetic field configurations elsewhere. For a dipole field, the resonance manifests itself in a substantial sensitivity (factor 3-4) of the average electron-cloud density to small variations in the field. 3D simulations are necessary for assessing the magnitude of the effect for non-negligible magnetic field gradient, and its effect on the beam. Work on the resonances and initial 3D WARP runs have shown that 3D effects are important in the damping ring wigglers. Owing to our benchmarking efforts, 3D parallelized simulations of the dynamics for the ILC positron damping ring are now possible with much more confidence than before. However at this time we have no funding to do this work; a description of proposed work is found below, contingent upon obtaining ILC funding.


Finally, CESR-TA will be a facility with dedicated diagnostics and beam time for electron cloud measurements, offering unusual and powerful opportunities to study electron cloud physics. Beam fill patterns and bunch intensity can be adjusted, and comparisons will be made between the effects of positron and electron beams. We intend to take advantage of this facility to study the above-mentioned cyclotron resonances in detail, to validate our codes, and to study electron clouds in dipoles and wigglers. We have the capability to help with planning of experiments, modeling of diagnostic performance, and interpretation of data. This effort will push forward our understanding of electron cloud formation and its effect on the beam. Researchers at Cornell are enthusiastic about collaboration with us in this endeavor.