• T. Sen
  Fermilab, Batavia

Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations.

• H.J. Kim, T. Sen
  Fermilab, Batavia
• W. Fischer
  BNL, Upton, Long Island, New York

In order to avoid the effects of long-range beam-beam interactions which produce beam blow-up and deteriorate beam life time, a compensation scheme with current carrying wires has been proposed. Two long-range beam-beam compensators were installed in RHIC rings in 2006. The effects of the compensators have been experimentally investigated. An indication was observed that the compensators are beneficial to beam life time in measurements performed in RHIC during 2009. In this paper, we report the effects of wire compensator on beam loss and emittance for proton-proton beams at collision energy.

• H.J. Kim, T. Sen
  Fermilab, Batavia

Increasing the luminosity requires higher beam intensity and often focusing the beam to smaller sizes at the interaction points. The effects of head-on interactions become even more significant. The head-on interaction introduces a tune spread due to a difference of tune shifts between small and large amplitude particles. A low energy electron beam so called electron lens is expected to improve intensity lifetime and luminosity of the colliding beams by reducing the betatron tune shift and spread. In this paper we discuss the results of beam simulations with the electron lens in RHIC.

• T. Sen, C.M. Bhat, H.J. Kim, J.-F. Ostiguy
  Fermilab, Batavia

We investigate the dynamics of longitudinally flat bunches created with a second harmonic cavity in a high energy collider. We study Landau damping in a second harmonic cavity with analytical and numerical methods. The latter include particle tracking and evolution of the phase space density. The results are interpreted in the context of possible application to the LHC.

• H.J. Kim, T. Sen
  Fermilab, Batavia

Beam collisions with a crossing angle at the interaction point are often necessary in colliders to reduce the effects of parasitic collisions which induce emittance growth and decrease beam lifetime. The crossing angle reduces the geometrical overlap of the beams and hence the luminosity. Crab cavity offer a promising way to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. A crab cavity experiment in SPS is proposed as a proof of principle before deciding on a full crab-cavity implementation in the LHC. In this paper, we investigate the effects of a single crab cavity on beam dynamics in the SPS and life time.