eSHIVA in IOTA: Experiment on Stochasticity in High Intensity Variable Accelerators
- Northern Illinois Univ., DeKalb, IL (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Northern Illinois Univ., DeKalb, IL (United States)
Nonlinear integrable optics, the basis of IOTA, is a very special form of Hamiltonian system, called completely integrable. The consequences are many, most importantly the absence of fixed points that are in one-to-one correspondence with (overlapping) resonances. This, in turn, does not limit the dynamic aperture and allows large amplitude dependent tune shifts without adverse effects. In fact, it helps significantly in alleviating issues with collective instabilities. We developed and tested different numerical methods to give a more complete picture of the dynamics of integrable and near-integrable nonlinear Hamiltonian systems consisting of motion of charged particles in electromagnetic fields. Comparison of the results allowed us to discern real phenomena from numerical artifacts and come up with conclusions that will facilitate pushing the intensity frontier in beam dynamics even further for the benefit of the accelerator community as a whole and society as the consequence of the science and technological advancements it will make possible. We concluded that, while novel structure preserving integrators would be ideal, symplectic methods under mild restrictions offer adequate invariant preservation. We especially highlighted the very good performance of the Stormer-Verlet method at low accuracy and a modified Lobatto method at high accuracy for the Integrable Optics Test Accelerator (IOTA). However, we showed that symplectic integrators are limited by numerically induced resonances, which make interpretation of some simulation results challenging. These limitations and workarounds have been addressed.The nonlinear integrable optics test accelerator IOTA at Fermilab -- a very special experimental accelerator designed to investigate nonlinear optics under severe space-charge conditions – has recently completed its construction and initial commissioning of the ring has begun. We report first, under 2 (a) below: the progress on the nonlinear tune-shift measurements for various values of the nonlinear strength potential and their comparison with theoretical expectations, thus benchmarking the nonlinear characteristics of the ring; then, under 2 (b) below: the progress on simulation and design of a gas-jet monitor to measure beam profile and in particular its diffusive halo, expected to develop during stochastic diffusion of large amplitude particles under nonlinear forces of the magnetic lattice and Coulomb space-charge. Since the development of a proton beam source in IOTA is delayed and to be completed only in the future pending financial support, the gas-jet monitor is planned for testing with real proton beams elsewhere at Fermilab (e.g. in the Main Injector or PIP-II source possibly). Once proton beams are available in IOTA, the understanding of the nonlinear properties of IOTA combined with the developed gas-jet monitor, will enable a thorough experimental analysis of nonlinear stochastic diffusion in IOTA nonlinear ring, and boosted by proper theoretical understanding of the same.
- Research Organization:
- Northern Illinois Univ., DeKalb, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- SC0015500
- OSTI ID:
- 1561844
- Report Number(s):
- DE-SC0015500; 0017455120000
- Country of Publication:
- United States
- Language:
- English
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