2018/04/19 by M. Fitterer, G. Stancari, Fitterer, Miriam +7
Engineering · Physics and Astronomy · #Accelerator Physics (physics.acc-ph) #FOS: Physical sciences #Gyrotron and Vacuum Electronics Research #Particle Accelerators and Free-Electron Lasers #Particle accelerators and beam dynamics
paper · pdf · doi:10.48550/arxiv.1804.07418
openalex publication_date 2018/04/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present the results of numerical simulations and experimental studies\nabout the effects of resonant and random excitations on proton losses,\nemittances, and beam distributions in the Large Hadron Collider (LHC). In\naddition to shedding light on complex nonlinear effects, these studies are\napplied to the design of hollow electron lenses (HEL) for active beam halo\ncontrol. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable\namount of energy will be stored in the beam tails. To control and clean the\nbeam halo, the installation of two hollow electron lenses, one per beam, is\nbeing considered. In standard electron-lens operation, a proton bunch sees the\nsame electron current at every revolution. Pulsed electron beam operation\n(i.e., different currents for different turns) is also considered, because it\ncan widen the range of achievable halo removal rates. For an axially symmetric\nelectron beam, only protons in the halo are excited. If a residual field is\npresent at the location of the beam core, these particles are exposed to\ntime-dependent transverse kicks and to noise. We discuss the numerical\nsimulations and the experiments conducted in 2016 and 2017 at injection energy\nin the LHC. The excitation patterns were generated by the transverse feedback\nand damping system, which acted as a flexible source of dipole kicks. Proton\nbeam losses, emittances, and transverse distributions were recorded as a\nfunction of excitation patterns and strengths. The resonant excitations induced\nrich dynamical effects and nontrivial changes of the beam distributions, which,\nto our knowledge, have not previously been observed and studied in this detail.\nWe conclude with a discussion of the tolerable and achievable residual fields\nand proposals for further studies.\n