Collimation for the LHC high intensity beams

The unprecedented design intensities of the LHC require several important advances in beam collimation. With its more than 100 collimators, acting on various planes and beams, the LHC collimation system is the biggest and most performing such system ever designed and constructed. The solution for LHC collimation is explained, the technical components are introduced and the initial performance is presented. Residual beam leakage from the system is analysed. Measurements and simulations are presented which show that collimation efficiencies of better than 99.97 % have been measured with the 3.5 TeV proton beams of the LHC, in excellent agreement with expectations.peer-reviewe

Design of the High Beta Cryomodule for the HIE-ISOLDE Upgrade at CERN

The major upgrade of the energy and intensity of the existing ISOLDE and REX-ISOLDE facilities at CERN will require the replacement of most of the existing ISOLDE post-acceleration by a superconducting linac based on quarter-wave resonators. The first stage of this upgrade involves the design, construction, installation and commissioning of two high- cryomodules downstream of REX, the existing post-accelerator. Each cryomodule houses five high-beta superconducting cavities and one superconducting solenoid. As well as providing optimum conditions for physics, where the internal active components must remain aligned within tight tolerances, the cryomodules need to function under stringent vacuum and cryogenic conditions. To preserve the RF cavity performance their assembly and sub-system testing will need to be carried out using specifically designed tooling in an ISO class 5 (US Fed. class 100) clean-room. We present the determining factors constraining the design of the high-beta cryomodules together with the design choices that these factors have imposed

DESIGN OF THE HIGH BETA CRYOMODULE FOR THE HIE-ISOLDE UPGRADE AT CERN

The major upgrade of the energy and intensity of the existing ISOLDE and REX-ISOLDE facilities at CERN will require the replacement of most of the existing ISOLDE post-acceleration by a superconducting linac based on quarter-wave resonators. The first stage of this upgrade involves the design, construction, installation and commissioning of two high-β cryomodules downstream of REX, the existing post-accelerator. Each cryomodule houses five high-β superconducting cavities and one superconducting solenoid. As well as providing optimum conditions for physics, where the internal active components must remain aligned within tight tolerances, the cryomodules need to function under stringent vacuum and cryogenic conditions. To preserve the RF cavity performance their assembly and sub-system testing will need to be carried out using specifically designed tooling in an ISO class 5 (US Fed. class 100) clean-room. We present the determining factors constraining the design of the high-β cryomodules together with the design choices that these factors have imposed.status: publishe

First cleaning with LHC collimators

The LHC has two dedicated cleaning insertions: IR3 for momentum cleaning and IR7 for betatron cleaning. The collimation system has been specified and built with tight mechanical tolerances (e.g. jaw flatness ~ 40 μm ) and is designed to achieve a high accuracy and reproducibility of the jaw positions (~ 20 μm). The practically achievable cleaning efficiency of the present Phase-I system depends on the precision of the jaw centering around the beam, the accuracy of the gap size and the jaw parallelism against the beam. The reproducibility and stability of the collimation system is important to avoid the frequent repetition of beam based alignment which is currently a lengthy procedure. Within this paper we describe the method used for the beam based alignment of the LHC collimation system, its achieved accuracy and stability and its performance at 450GeV