Optics Studies for Diffractive Physics at the LHC

Forward protons with momenta close to the beam-momentum arise either from elastic scattering or from single or double diffraction. These protons are very close to the beamline and can only be measured downstream using "beam close detectors". In this paper we present a complete study of the optics (low, medium and high beta), possible locations of the detectors and running scenarios for these measurements at insertions IR1 and IR5 of the LHC. These optics are compatible with the latest layout of the LHC insertions and the commissioning beam parameters

Precise measurement of the total cross section and the Coulomb scattering at the LHC

A precise measurement of the total cross section and the coulomb scattering at the LHC requires the observation of elastically scatteredparticles at extremely small angles (14 microrad, -t < 0.01 GeV**2 for the first case; 3 microrad, -t<0.0006 GeV**2 for the second one). In this paper a very high-beta insertion optics is presented. A feasibility study, including the acceptance of the detectors, for an experiment to be installed in IR1 or IR5, is also presented.Comment: 3 pages, 4 figures, 7th European Particle Accelator Conferenc

Measurement of Driving Terms

In 2000 a series of MDs has been performed at the SPS to measure resonance driving terms. Theory predicts that these terms can be determined by harmonic analysis of BPM data recorded after applying single kicks at various amplitudes. Strong sextupoles were introduced to create a sizeable amount of nonlinearities. Experiments at injection energy (26 GeV) with single bunch as well as one experiment at 120 GeV with 84 bunches were carried out. The expected nonlinear content is compared to the experimenteal observation

Limits of chromaticity correction

The LHC luminosity upgrade supposes from the point of view of the optics the upgrade of the Interaction Regions (IR) of the main experiments ATLAS and CMS. This upgrade is expected to provide a of 25 cm instead of the 50 cm of the nominal one. This decreasing in implies an increasing of the maximum in the low-quadrupoles and subsequently a more dif cult chromaticity correction. In this report we analyze ¡the limits and possible strategies on the chromaticity correction for the different optics proposed for the upgrade of the IR

Luminosity, beamstrahlung energy loss and beam-beam deflections for e+e−e^+e^- collisions at the ILC with 500 GeV and varying transverse beam sizes

At the interaction point of the International Linear Collider, beam-beam effects due to the strong electromagnetic fields that the bunches experience during collisions cause a mutual focusing called pinch effect, which enhances the luminosity in the case of $e^+e^-$ collisions. The opposite is true for $e^+e^-$ collisions. In this case the luminosity is reduced by mutual defocusing, or anti-pinching. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are also different for both modes of operation. The dependence of these quantities with transverse beam sizes are presented for the case of $e^+e^-$ collisions

Optimization of the e-e- option for the ILC

The e-e- running mode is one of the interesting physics options at the International Linear Collider (ILC). The luminosity for e-e- collisions is reduced by the beam-beam effects. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are different compared to the e+e- collisions. In this paper, the dependence of these observables with the offset for different beam sizes has been analyzed to optimize performances for the e-e- mode, taking into account the requirements of the beam-beam deflection based intra-train feedback system. A first study of the implications for the final focus and extraction line optics is also presented for the cases of the 20 mrad and 2 mrad ILC base line crossing angle geometries

Luminosity, beamstrahlung energy loss and beam-beam deflections for e+e- and e-e- collisions at the ILC with 500 GeV and varying transverse beam sizes

At the interaction point of the International Linear Collider, beam-beam effects due to the strong electromagnetic fields that the bunches experience during collisions cause a mutual focusing called pinch effect, which enhances the luminosity in the case of $e^+e^-$ collisions. The opposite is true for $e^+e^-$ collisions. In this case the luminosity is reduced by mutual defocusing, or anti-pinching. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are also different for both modes of operation. The dependence of these quantities with transverse beam sizes are presented for the case of $e^+e^-$ collisions

Decreasing the LHC impedance with a nonlinear collimation system

A two-stage nonlinear collimation system based on a pair of skew sextupoles is presented for the LHC.We show the details of the optics design and study the halo cleaning efficiency of such a system. This nonlinear collimation system would allow opening up collimator gaps, and thereby reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, the transverse coherent tune shifts of rigid-dipole coupled-bunch modes are computed for both the baseline linear collimation system and the proposed nonlinear one. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping

Modelling Nonlinear Optics in the CERN SPS

Nonlinear fields arising from eddy currents in the vac-uum chamber and remanent fields in the magnets of the CERN SPS vary with time and with the acceleration cycle. We describe a procedure of constructing a nonlinear op-tics model for the SPS, by considering sextupolar, octupo-lar, and decapolar field errors in the dipole and quadrupole magnets, respectively, whose strengths are adjusted so as to best reproduce the measured nonlinear chromaticities up to third order in the momentum deviation. Applying this procedure to SPS chromaticity measurements taken at 26 GeV/c, we have obtained a refined optics model. The tune shifts with the transverse amplitude predicted by this model are consistent with a direct measurement