Nonlinear Field Errors Research Articles

Corrections of Feed-Down of Non-Linear Field Errors in LHC and HL-LHC Insertion Regions

Corrections of Feed-Down of Non-Linear Field Errors in LHC and HL-LHC Insertion Regions

Corrections of Non-Linear Field Errors with Asymmetric Optics in LHC and HL-LHC Insertion Regions

Corrections of Non-Linear Field Errors with Asymmetric Optics in LHC and HL-LHC Insertion Regions

Beam quality and beam loss predictions with space charge for SIS100

The SIS100 synchrotron as a part of the new FAIR accelerator facility at GSI should be operated at the “space charge limit” for light and heavy-ion beams. Losses due to space charge induced resonance crossing should not exceed a few percent during a full cycle. Detailed magnet field measurements are now available for 72 out of the total 108 main SIS100 dipole magnets. Particle tracking studies including nonlinear field errors up to 7th order in the main magnets together with different space charge models are performed. Because of the long time scales reduced space charge models are employed for tune scans. First comparisons with simulations using a self-consistent space charge solver are discussed as well as potential measures to further improve the options in tune space for the reference intensities and beyond.

Collective beam-beam effects in hadron colliders

Collective beam-beam effects in hadron colliders were studied with a strong-strong beam-beam simulation on the CERN Large Hadron Collider, including multipole field errors in the lattice and beam-beam interactions at two high-luminosity interaction points. It was found that the beam-beam interaction could result in two distinct dynamics for hadron beams: a slow beam-size growth and an unstable beam-centroid oscillation. The instability of the beam-centroid oscillation has typical characteristics of the chaotic transport, i. e., the amplitude increase of the oscillation consists of slow escape from the remnants of invariant manifolds and fast diffusion in fully developed chaotic regions. The simulation results indicate that there is a threshold of the beam-beam parameter below which no unstable beam-centroid motion was observed. The escape rate of the unstable beam-centroid motion, on the other hand, increases with the nonlinear field errors in the lattice. As the slow beam-size growth is strongly enhanced by the beam-centroid oscillation, an elimination of the centroid motion with feedback can effectively suppress the beam-size growth. No steady state of coherent beam-beam oscillation was observed.

Experimental studies of nonlinear beam dynamics.

The nonlinear beam dynamics of transverse betatron oscillations were studied experimentally at the Indiana University Cyclotron Facility cooler ring. Motion in one dimension was measured for betatron tunes near the third, fourth, fifth, and seventh integer resonances. This motion is described by coupling between the transverse modes of motion and nonlinear field errors. The Hamiltonian for nonlinear particle motion near the third- and fourth-integer-resonance conditions has been deduced.