First Experimental Evidence of a Beam-Beam Long-Range Compensation Using Wires in the Large Hadron Collider

In high intensity and high energy colliders such as the CERN Large Hadron Collider and its future High Luminosity upgrade, interactions between the two beams around the different Interaction Points impose machine performance limitations. In fact, their effect reduces the beam lifetime and therefore the collider's luminosity reach. Those interactions are called Beam-Beam Long-Range interactions and a possible mitigation of their effect using DC wires was proposed for the first time in the early 2000's. This solution is currently being studied as an option for enhancing the HL-LHC performance. In 2017 and 2018, four demonstrators of wire compensators have been installed in the LHC. A two-year long experimental campaign followed in order to validate the possibility to mitigate the BBLR interactions in the LHC. During this campaign, a proof-of-concept was completed and motivated an additional set of experiments, successfully demonstrating the mitigation of BBLR interactions effects in beam conditions compatible with the operational configuration. This paper reports in detail the preparation of the experimental campaign, the obtained results and draws some perspectives for the future.Comment: Draft for a later PRAB submissio

Application of high order symplectic integration methods with forward integration steps in beam dynamics

International audienceThe Hamiltonian describing particle motion in an accelerator belongs to a large class of systems, the members of which can be integrated with a new set of high order symplectic integrators. One benefit of these integrators is their strong numerical stability, which results from the inclusion of only forward integration steps, independent of the order of accuracy. Using these integrators, the transfer map of any multipolar accelerator magnet is derived and presented here. From these maps, the Hamiltonian flow in different lattices is simulated and benchmarked against other well established integration schemes in the accelerator community. By comparing quantities such as the linear phase advance and action invariant, the chromaticity, as well as the working point and the tune spread with amplitude, the superiority of the novel symplectic integrators is demonstrated with respect to accuracy and integration cost

Lattice and detector studies for the MDI of a 10 TeV muon collider

Among the possible future lepton colliders under study, circular muon colliders have the largest potential of reaching center-of-mass energies of 10+ TeV. Being more massive than electrons and positrons, muons are much less affected by synchrotron radiation emission, but they suffer from the drawback of having a limited lifetime. As a consequence of their decay, intense secondary radiation fields are generated in the collider, which can considerably disrupt the detector performance, both as physics background and as a cause of long-term material degradation. The machine-detector interface in a muon collider therefore requires a careful design, integrating massive shielding elements between the detector and final focus magnets. In this paper, we devise an interaction region design for a 10 TeV muon collider with a final focus triplet. We quantify the flux of secondary particles entering the detector by means of shower simulations and provide a first optimization of the shielding configuration. We also present first estimates of the power deposition and radiation damage in final focus magnets

Transverse impedance and beam stability studies for the muon collider ring

In the framework of the International Muon Collider Collaboration, a 10 TeV muon collider ring is being studied, with the option of an intermediate 3 TeV collider stage. The decay of high-energy muons represents a great challenge in terms of heat load management and radiation shielding for the superconducting magnets of the collider ring. Materials such as tungsten are being considered to shield the cold bore of the magnets from decay products. The transverse beam coupling impedance and related beam stability have been investigated in detail for several vacuum chamber designs to identify the minimum vacuum chamber radius and transverse damper properties required for stable beams