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Todesco, E.

Paper Title Page
MOPAN083 130 mm Aperture Quadrupoles for the LHC Luminosity Upgrade 350
  • E. Todesco, F. Borgnolutti
    CERN, Geneva
  • A. Mailfert
    ENSEM, Vandoeuvre les Nancy
  Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" program (CARE, contract number RII3-CT-2003-506395)

Studies for the LHC luminosity upgrade showed the need for quadrupoles with apertures much larger than the present baseline (70 mm). In this paper we focus on the design issues of a 130 mm aperture quadrupole. We first consider the Nb-Ti option, presenting the magnetic design with the LHC dipole cable. We study the Lorentz forces and we discuss the field quality constraints. For the Nb3Sn option we sketch two designs, the first based on the LARP 10 mm cable, and the second one on a 15 mm cable. The issue of the stress induced by the Lorentz forces, which is critical for the Nb3Sn, is discussed using both scaling laws and finite element models.

MOPAN084 Estimating Field Quality in Low-beta Superconducting Quadrupoles and its Impact on Beam Stability 353
  • E. Todesco, B. Bellesia, J.-P. Koutchouk
    CERN, Geneva
  • C. Santoni
    Universite Blaise Pascal, Clermont-Ferrand
  Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" program (CARE, contract number RII3-CT-2003-506395)

The aim of this analysis is to study if the field quality in a large aperture low-beta superconducting quadrupole for the LHC upgrade limits the beam performances due to increased geometric aberrations. Random field errors in superconducting quadrupoles are usually estimated by computing the effect of a random positioning of the coil blocks around the nominal position with an r.m.s. of 0.05 mm. Here, we review the experience acquired in the construction of 7 superconducting quadrupoles in the RHIC and in the LHC projects to estimate the precision in the block positioning, showing that there is no visible dependence on the magnet aperture. Different magnet models are then used to estimate the expected field quality in quadrupoles with apertures ranging from 50 to 200 mm. The impact on geometrical aberrations and scaling laws for their dependence on the aperture are finally evaluated.

THPAN072 A Concept for the LHC Luminosity Upgrade Based on Strong Beta* Reduction Combined with a Minimized Geometrical Luminosity Loss Factor 3387
  • E. Todesco, R. W. Assmann, J.-P. Koutchouk, E. Metral, G. Sterbini, F. Zimmermann, R. de Maria
    CERN, Geneva
  A significant increase of the LHC beam current touches physics limits as collective effects, electron-cloud, heat load, collimation and machine protection. We propose an upgrade scheme mainly based on a stronger focusing, with a beta* of 10 cm, requiring a triplet quadrupole aperture of around 130 mm. The performance is further improved if the triplet is based on the Nb3Sn technology. In the present baseline, this beta* reduction provides a negligible luminosity increase: this approach requires a drastic action to minimize the crossing angle, while the beam separation at the long-range encounters has to be increased. This is provided by an early separation scheme made of small dipoles inside the detectors. Optionally, a small angle crab cavity scheme may totally suppress the residual crossing angle. The quadrupole aperture is calculated to allow a larger gap for the collimator, suppressing their impedance limitation. This concept offers high performance while significantly reducing the risks associated to a beam current increase; it opens as well new issues that deserve further studies, such as the dipole integration in the detector, and the correction of the triplet aberrations.