Building the impedance model of a real machine

A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved

Machine layout and performance

The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community of about 7,000 scientists working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will need a major upgrade in the 2020s. This will increase its luminosity (rate of collisions) by a factor of five beyond the original design value and the integrated luminosity (total collisions created) by a factor ten. The LHC is already a highly complex and exquisitely optimised machine so this upgrade must be carefully conceived and will require about ten years to implement. The new configuration, known as High Luminosity LHC (HL-LHC), will rely on a number of key innovations that push accelerator technology beyond its present limits. Among these are cutting-edge 11-12 tesla superconducting magnets, compact superconducting cavities for beam rotation with ultra-precise phase control, new technology and physical processes for beam collimation and 300 metre-long high-power superconducting links with negligible energy dissipation. The present document describes the technologies and components that will be used to realise the project and is intended to serve as the basis for the detailed engineering design of HL-LHC

Testing Long-Range Beam-Beam Compensation for the LHC Luminosity Upgrade

The performance of the Large Hadron Collider (LHC) at CERN and its minimum crossing angle are limited by the effect of long-range beam-beam collisions. A wire compensators can mitigate part of the long-range effects and may allow for smaller crossing angles, or higher beam intensity. A prototype long-range wire compensator could be installed in the LHC by 2014/15. Since the originally reserved position for such a wire compensator is not available for this first step, we explore other possible options. Our investigations consider various longitudinal and transverse locations, different wire shapes, different optics configurations and several crossing angles between the two colliding beams. Simulations are carried out with the weak-strong code BBtrack. New postprocessing tools are introduced to analyse tune footprints and particle stability. In particular, a new method for the Lyapunov coefficient calculation is implemented. Submitted as "Tesi di laurea" at the University of Milano, 2012

LEIR impedance model and coherent beam instability observations

The LEIR machine is the first synchrotron in the ion ac-celeration chain at CERN and it is responsible to deliverhigh intensity ion beams to the LHC. Following the recentprogress in the understanding of the intensity limitations,detailed studies of the machine impedance started. In thiswork we describe the present LEIR impedance model, detail-ing the contribution to the total longitudinal and transverseimpedance of several machine elements. We then comparethe machine tune shift versus intensity predictions againstmeasurements at injection energy and summarize the co-herent instability observations in the absence of transversefeedback

Design of Low-Impact Impedance Devices: the new Proton Synchrotron Booster Absorber Scraper (PSBAS)

At CERN the HL-LHC (High Luminosity Large Hadron Collider) and the LIU (LHC Injection Upgrade) projects call for an increase in beam parameters such as energy, intensity and brightness. To achieve this goal the whole accelerator complex will be upgraded. Systems, equipment and devices need to be redesigned and rebuilt accounting for the demanding new beam features. In this framework device impedance is a key parameter. It is essential to evaluate and to minimize the impedance of the component during its early design phase. This avoids beam instabilities and minimizes beam losses and induced heating. In this paper we outline general guidelines for a low-impedance design and we show how to implement them in a real case, taking as example the design of the new Proton Synchrotron Booster Absorber Scraper (PSBAS). This is a key component aimed to remove the beam halo at the beginning of the LHC accelerator chain

Chapter 2: Machine Layout and Performance

Chapter 2 in High-Luminosity Large Hadron Collider (HL-LHC) : Preliminary Design Report. The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community of about 7,000 scientists working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will need a major upgrade in the 2020s. This will increase its luminosity (rate of collisions) by a factor of five beyond the original design value and the integrated luminosity (total collisions created) by a factor ten. The LHC is already a highly complex and exquisitely optimised machine so this upgrade must be carefully conceived and will require about ten years to implement. The new configuration, known as High Luminosity LHC (HL-LHC), will rely on a number of key innovations that push accelerator technology beyond its present limits. Among these are cutting-edge 11-12 tesla superconducting magnets, compact superconducting cavities for beam rotation with ultra-precise phase control, new technology and physical processes for beam collimation and 300 metre-long high-power superconducting links with negligible energy dissipation. The present document describes the technologies and components that will be used to realise the project and is intended to serve as the basis for the detailed engineering design of HL-LHC