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de Maria, R.

Paper Title Page
MOPLS016 LHC IR Upgrade: A Dipole First Option with Local Chromaticity Correction 571
 
  • R. de Maria, O.S. Brüning
    CERN, Geneva
  • P. Raimondi
    INFN/LNF, Frascati (Roma)
 
  In the framework of the LHC Luminosity Upgrade, we develop a new layout of the interaction region (IR) with betastar equal to 25cm in which the combination-separation dipoles come first with respect to the triplet assembly (dipole first) in opposition of the nominal layout (quadrupole first). The new layout presents several advantages (separate channel for multipole errors, straightforward crossing angle scheme, early separation of the beam). The payoff is a large beta function in the triplet, which enhances the chromaticity and other non-linear effects. We investigate options for local chromaticity correction and their effects on long-term stability.  
MOPLS017 A Low Gradient Triplet Quadrupole Layout Compatible with NbTi Magnet Technology and Betastar=0.25m 574
 
  • R. de Maria, O.S. Brüning
    CERN, Geneva
 
  The paper presents a triplet layout option with long (ca. 100 m total triplet length), low gradient (45 T/m to 70 T/m) quadrupole magnets. Assuming a maximum magnet diameter of 200mm, the peak coil field at the magnet coils still remains below 7 T which is still compatible with conventional NbTi magnet technology. The peak beta function inside the triplet magnets reaches 18 km and the configuration therefore requires an additional chromaticity correction scheme similar to a dipole first layout option. However, at the same time, the presented solution provides an interesting alternative to a high gradient triplet layout which requires the new Nb3Ti magnet technology.  
WEPCH092 Dynamical Aperture Studies for the CERN LHC: Comparison between Statistical Assignment of Magnetic Field Errors and Actual Measured Field Errors 2128
 
  • M. Giovannozzi, S.D. Fartoukh, S.S. Gilardoni, J.-B. Jeanneret, A.M. Lombardi, Y. Papaphilippou, T. Risselada, R. de Maria
    CERN, Geneva
 
  It is customary to evaluate the performance of a circular particle accelerator by computing the dynamical aperture, i.e., the domain in phase space where bounded single-particle motion occurs. In the case of the LHC the dynamical aperture computation is performed by assuming a statistical distribution of the magnetic field errors of various magnets' classes: the numerical computations are repeated for a given set of realisations of the LHC ring. With the progress in the magnet production and allocation of the available positions in the ring, the statistical approach has to be replaced by the computation of one single configuration, namely the actual realisation of the machine. Comparisons between the two approaches are presented and discussed in details.  
WEPLS107 Comparative Study of Inter-strand Coupling Current Models for Accelerator Magnets 2631
 
  • R. de Maria, B. Auchmann, S. Russenschuck
    CERN, Geneva
 
  "Inter-Strand Coupling Currents" (ISCCs) contribute to field errors and losses in Rutherford-type superconducting cables in the time- transient regime. The field change induces eddy currents in loops formed by the superconducting twisted strands and the resistive matrix. In the ROXIE program two models are implemented to simulate ISCCs in a magnet cross-section: A network model uses an electric circuit to represent the geometry of the twisted strands and their resistive contacts; an analytical model simplifies the network equations to determine an equivalent cable magnetization from an average field sweep over the cable. The implementation of the models in ROXIE allows to combine them with models for "Persistent Currents" and "Inter-Filament Coupling Currents". The non-linear iron yoke can be taken into account as well. The predictions of different ISCC models with regard to losses and field errors are compared for two design versions of the LHC main dipole. We find that as far as field quality is concerned, the models perform equally well. As for losses, however, the analytical model cannot capture the complexity of the problem and computes lower losses than the network model.