Beam Dynamics in a High Frequency RFQ - Invited Contribution

• Alessandra Lombardi (CERN)

Room: 774/R-013 CERN is constructing a 750 MHz Radio Frequency Quadrupole (RFQ) which can accelerate a proton beam to 5 MeV in a length of 2 m. The beam dynamics strategic parameters have been chosen to make this RFQ a good candidate for the injector of a medical facility operating at frequency of 3 GHz. Minimising beam losses above 1 MeV, containing the RF power losses and opening the road to industrialisation have been the guidelines for an unconventional RFQ design. In this paper, the optimisation efforts, the structure design and the expected beam qualities will be detailed. The status of the construction as well as the potential for further developments will be presented. Authors: Alessandra Maria Lombardi, Veliko Atanasov Dimov, Marco Garlasché, Alexej Grudiev, Serge Jean Mathot, Eric Montesinos, Stephen Myers, Marc Alexander Timmins, Maurizio Vretenar (CERN, Geneva)

Preliminary Design of the High-Luminosity LHC Beam Screen with Shielding - Oral Contribution

• Roberto Kersevan (CERN)

Room: 774/R-013 A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, they have to shield the cold mass from physics debris coming from the nearby beam collision points. To such purpose, energy absorbers made of tungsten alloy are installed onto the beam screen in the vacuum system. In this contribution, the proposed mechanical design is shown; it covers different thermomechanical aspects such as the behaviour during a magnet quench and the heat transfer from the tungsten absorbers to the cooling tubes. Assembly and manufacturing tolerances are also considered to evaluate the impact on the aperture. Results obtained with a short prototype assembly test are discussed. Authors: Cedric Garion, Vincent Baglin, Roberto Kersevan (CERN, Geneva)

Comparison between Measured and Computed Temperatures of the Internal High Energy Beam Dump in the CERN SPS - Oral Contribution

• Genevieve Eleanor Steele (CERN)

Room: 774/R-013 The SPS high energy internal dump (TIDVG) is designed to receive beam dumps from 102.2 to 450 GeV. The absorbing core is composed of 2.5m graphite, followed by 1m of aluminium, then 0.5m of copper and finally 0.3m of tungsten, all of which is surrounded by a water cooled copper jacket. An inspection during Long Shutdown 1 revealed significant beam induced damage to the Al section of the dump block. Temperature sensors were installed to monitor the new dump replacing the damaged one. This paper summarises the correlation between the temperature measured as a function of the energy deposited and the same temperatures computed in a numerical model combining FLUKA and ANSYS simulations. The goal of this study is the assessment of the thermal contact quality between the beam absorbing blocks and the copper jacket, by analysing the cooling times observed from the measurements and from the thermo-mechanical simulations. This paper presents an improved method to estimate the efficiency and long term reliability of the cooling of this type of design, with the view of optimising the performance of future dump versions. Authors: Genevieve Eleanor Steele, Ramon Folch, Verena Kain, Ivo Leitao, Roberto Losito, Cesare Maglioni, Florian Pasdeloup, Antonio Perillo-Marcone, Francesco Maria Velotti (CERN, Geneva)

Effects of Accelerating Structures on On-line DFS in the Main Linac of CLIC - Oral Contribution

• Juergen Pfingstner (University of Oslo (NO))

Room: 774/R-013 Long-term ground motion will create significant dispersion in the time-scale of hours in the main linac of CLIC. To preserve the emittance to an acceptable level, a dispersion correction with on-line dispersion-free steering (DFS) is inevitable. For this on-line technique, the dispersion has to be measured using beam energy variations of only about one per mil in order to not disturb the operation of the accelerator. For such small energy variations, the interaction of the particle beam and the accelerating structures creates large enough additional signals components in the measured dispersion to cause the dispersion correction to not work properly anymore. In this paper, the additional signals are described and their effect on the DFS algorithm is analysed. Finally, methods for the mitigation of the deteriorating signal components are presented and studied via simulations. Authors: Juergen Pfingstner, Erik Adli (University of Oslo, Oslo), Daniel Schulte (CERN, Geneva)

Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation - Oral Contribution

• Roderik Bruce (CERN)

Room: 774/R-013 Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed. Authors: Stefano Redaelli, Alessandro Bertarelli, Roderik Bruce, Diego Perini, Adriana Rossi, Belen Salvachua (CERN, Geneva), Giulio Stancari, Alexander Valishev (Fermilab, Batavia, Illinois)