BNL, Upton, Long Island, New York
Fermilab, Batavia
Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH1-886
Long-range and head-on beam-beam effects are expected to limit the LHC performance with design parameters. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both the LHC and RHIC. We present the experimental long-range beam-beam program and report on head-on compensations studies at RHIC, which are primarily based on simulations.
Fermilab, Batavia
Abstract The compensation of long-range beam-beam interactions with current carrying wires in the Large Hadron Collider (LHC) is studied by multi-particle tracking. In the simulations, we include the effect of long-range collisions together with the nonlinearities of IR triplets, sextupoles, and head-on collisions. The model includes the wires placed at the locations reserved for them in the LHC rings. We estimate the optimal parameters of a wire for compensating the parasitic beam-beam force by long-term simulations of beam lifetime.
Fermilab, Batavia
A beam-beam simulation code (BBSIMC) has been developed to study the interaction between counter moving beams in colliders and its compensation through a low energy electron beam. This electron beam is expected to improve intensity lifetime and luminosity of the colliding beams by reducing the betatron tune shift and spread from the head-on collisions. In this paper we discuss the results of beam simulations with the electron lens in the Relativistic Heavy Ion Collider (RHIC). We study the effects of the electron beam profile and strength on the betatron tunes, dynamic aperture, frequency diffusion and beam lifetime.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No. DE-FG02-08ER85183
A new set of tools for BBSIM has recently been developed to analyze the nature of the diffusion in multi-particle simulations. The diffusion subroutines are currently used to accelerate beam lifetime calculations by estimating the diffusion coefficient at various actions and integrating the diffusion equation. However it is possible that there may be regimes where anomalous diffusion dominates and normal diffusion estimates are incorrect. The tools we have developed estimate the deviation from normal diffusion and can fit the coefficients of a jump diffusion model in the event that this type of diffusion dominates.
Fermilab, Batavia
We examine the stability of intense flat bunches in barrier buckets. We consider a class of stationary distributions and derive analytical expressions for the threshold intensity at which Landau damping is lost against rigid dipole oscillations in the presence of impedances and space charge forces. Particle simulations are used to follow the dynamics in a barrier bucket and compare with the analytic expressions. These studies are related to experimental observations in the Recycler ring at Fermilab.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No.DE-FG02-08ER85183
Recent improvements to BBSIM permit detailed simulations of collective effects due to resistive wall wake fields. We compare results of beam transfer measurements (BTF) in the Tevatron and RHIC with and without the effects of resistive wall wake fields. These are then compared to actual BTF measurements made in both machines and the impact of intensity on our measurements. We also investigate the impact of resistive wall wake fields on various chromaticity measurement approaches.