• N.J. Sammut, C. Giloux, M. Lamont, W. Venturini Delsolaro, S.M. White
  CERN, Geneva

The Large Hadron Collider beams are brought into collision by superconducting orbit corrector magnets which generate the parallel separation and crossing angles at the interaction points during the different cycle phases. Unfortunately, the magnetic field errors that result from hysteresis effects in the operation region of these magnets lead to unwanted orbit perturbations. In a previous paper, it has been shown that these effects are within the perturbations coming from beam-beam interactions for the MCBC and the MCBY magnets but are significant in the case of the MCBX magnets. This paper presents a refined model of their field in the frame of the Field Description for the LHC (FiDeL), the results obtained from new magnetic measurements in cold conditions to test the model, the powering mechanism employed to maximize their field reproducibility, and the impact the modeling error is predicted to have on the LHC orbit.

• S.M. White, R. Alemany-Fernandez, H. Burkhardt, M. Lamont
  CERN, Geneva

We discuss luminosity monitoring, optimization and absolute calibration in the LHC. Interaction rates will be continuously monitored both by detectors on the machine side as well as by the four large LHC experiments. Horizontal and vertical separation scans will be used to optimize luminosity and to measure the beam sizes in the interaction region. An application software has been developed for this purpose. We describe the procedures which have been prepared and discuss expected systematic effects which may limit the accuracy of the measurement.

• H. Burkhardt, Y.I. Levinsen, S.M. White
  CERN, Geneva

The TOTEM experiment requires special high beta optics solutions. We report on studies of optics for an intermediate beta* = 90 m, as well as a solutions for a very high beta* of 1540 m, which respect all known constraints. These optics are rather different from the normal physics optics and will require global tune changes or adjustments.

• S.M. White, H. Burkhardt, S.D. Fartoukh, T. Pieloni
  CERN, Geneva

The LHC beams will cross each other and experience perturbations as a result of the beam-beam effect at the interaction points, which can result in emittance growth and halo creation. The beam-beam force is approximately linear for small offsets and highly non-linear for larger offsets with peaks in growth close to 0.3 and 1.5 σ separation. We present a study of the process of going into collisions in the LHC and use simulations to investigate on possible emittance blow-up. We analyze how the crossing scheme can be optimized to minimize the collapsing time of the separation bumps for given hardware constraints.

• S. Cavalier, M. Heller
  LAL, Orsay
• H. Burkhardt, P.M. Puzo, S.M. White
  CERN, Geneva

For luminosity and total cross section measurement, the standard LHC physics optics has been modified for the ATLAS experiment in the so-called high beta optics with a beta star of 2600m. The high beta optics takes into account the whole LHC ring. Protons are, then, tracked from the Interaction Point to the detectors. Tolerances on the beta star are given and the effect of misalignment errors is checked. We show the final High beta optics used and the impact of the misalignment effect on the measurement.

• S.M. White, E. Bravin
  CERN, Geneva

The LHC collision rate monitors (BRAN) will be used to monitor and optimize the luminosity at the four interaction points (IP). Depending on the expected level of luminosity for a given IP two different designs have been developed for LHC. At IP1 and IP5, the high luminosity experiments, the BRAN consist of fast ionization chambers and at IP2 and IP8, where the collision rate will be smaller, they consist of fast polycristalline-CdTe detectors. A better understanding of the performances of those detectors can be provided by detailed tracking simulations of the collision products coming from the IP within the detector. Here we report about the results of simulations done with FLUKA as well as a comparison with measurements done in the SPS.

• B. Salvant
  EPFL, Lausanne
• G. Arduini, H. Burkhardt, H. Damerau, W. Höfle, E. Métral, G. Papotti, G. Rumolo, B. Salvant, R. Tomás, S.M. White
  CERN, Geneva
• R. Calaga, R. De Maria
  BNL, Upton, Long Island, New York

The upgrade of the CERN Large Hadron Collider (LHC) would require a four- to fivefold increase of the single bunch intensity presently obtained in the Super Proton Synchrotron (SPS). Operating at such high single bunch intensities requires a detailed knowledge of the sources of SPS beam coupling impedance, so that longitudinal and transverse impedance reduction campaigns can be planned and performed effectively if needed. In this paper, the transverse impedance of the SPS is studied by injecting a single long bunch into the SPS, and observing its decay without RF. This particular setup enhances the resolution of the frequency analysis of the longitudinal and transverse bunch signals acquired with strip line couplers connected to a fast data acquisition. It also gives access to the frequency content of the transverse impedance. Results from measurements with short and long bunches in the SPS performed in 2008 are compared with simulations and theoretical predictions.