Speaker
Description
Angular-momentum-dominated beams with a circular cross-section are referred to as circular-mode beams. The strong coupling introduced by angular momentum dominance produces a large asymmetry between the eigenmode emittances, known as intrinsic flatness: the beam is round in real space yet effectively flat in eigenmode space. With proper optics design, both the angular momentum and the circular cross-section can be preserved along the machine. This combination of round cross-section and intrinsic flatness makes the beam resilient to geometric collective effects such as space charge. Moreover, since resonance driving terms and instability growth rates scale with the mode invariants, the strong emittance asymmetry suppresses resonances and instabilities associated with the small eigenmode. This talk will introduce circular-mode beams and present two key results: the space-charge-induced tune spread is smaller than that of an uncorrelated Gaussian beam of equal intensity and total emittance, and the resonance driving terms associated with the small eigenmode do not contribute to the dynamics, rendering the beam dynamics effectively one-dimensional.