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MOPR037 |
Space Charge Effects on Ion Beam Dynamics and Integrability in the Iota Ring | |
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Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340. Modern hadron accelerators such as spallation sources and neutrino factories must push the intensity limits to meet increasingly challenging demands on performance. The Integrable Optics Test Accelerator (IOTA) is a small ring, currently under construction at Fermilab, which will explore advanced concepts in beam dynamics with low-energy proton beams with high space charge tune depression. Through use of a special nonlinear magnet insertion, large tune spread with amplitude can be achieved while preserving two integrals of motion for the single particle behavior. The stability of these invariants is particularly sensitive to collective effects such as space charge induced tune depression. We present results from simulations of IOTA using the particle-in-cell framework Warp and the accelerator simulation package Synergia exploring the behavior of proton beams in the presence of space charge. We examine potential lattice variations that correct for tune depression and beam mismatch while minimizing deviations from integrability. |
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MOPR038 |
Nonlinear Dynamics and Paths to Integrability in the IOTA Lattice | |
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Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0011340. Betatron tune spread with amplitude suppresses intensity-driven parametric instabilities such as beam halo. Conventional approaches, such as using octupoles, can reduce the single-particle dynamic aperture. The concept of nonlinear integrable optics promises to introduce order unity tune spreads without introducing nonlinear resonances that limit the dynamic aperture. The idealized zero-current dynamics is constrained by two integrals of the motion, but even the single particle motion can be perturbed by energy spread. To study this concept, Fermilab is building the Integrable Optics Test Accelerator (IOTA). Simulations using the accelerator simulation package Synergia have demonstrated higher order effects to the ideal lattice, including effects due to finite phase advance across the nonlinear magnet and a particular sensitivity to chromaticity-correcting schemes. We present evidence for these higher-order effects, and illustrate the sensitivity of the dynamics to sextupole fields, showing that their proper pairing can preserve integrability and reduce beam loss. |
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MOPR039 |
Survey of Variational Algorithms for Modeling Intense Beams | |
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Funding: The work presented here was supported by the U.S. Department of Energy, Office of Science, and the Air Force Office of Scientific Research, Young Investigator Program. Variational algorithms are a promising tool recently rediscovered and being applied to plasma-based accelerators, fusion plasmas, and intense beams. We offer a brief historical survey of the subject, and describe the foundational concepts of the algorithm. We then present their application to the problems of beam loading in RF cavities and space charge. By making careful choices in constructing the algorithms, it is possible to use fewer time steps to achieve higher fidelity simulations. |
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MOPR040 |
A Single-Turn Map Formalism for Collective Effects | |
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Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics and by the Air Force Office of Scientific Research, Young Investigator Program. The concept of a single-turn map provides considerable insight into the long-term single particle dynamics in storage rings. Using a factored map formalism and a Hamiltonian perturbation theory for plasmas, we derive a first order perturbative treatment of collective effects in rings. This allows us to extend the single-turn map formalism to include collective effects. This treatment goes beyond the constant focusing channel approximation, and can be extended to include a variety of physical effects not previously considered. |
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