EPAC08 - List of Authors (Arduini, G.)

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Arduini, G.

Paper	Title	Page
MOPC131	Ions for LHC: Towards Completion of the Injector Chain	376
	D. Manglunki, M. Albert, M.-E. Angoletta, G. Arduini, P. Baudrenghien, G. Bellodi, P. Belochitskii, E. Benedetto, T. Bohl, C. Carli, E. Carlier, M. Chanel, H. Damerau, S. S. Gilardoni, S. Hancock, D. Jacquet, J. M. Jowett, V. Kain, D. Kuchler, M. Martini, S. Maury, E. Métral, L. Normann, G. Papotti, S. Pasinelli, M. Schokker, R. Scrivens, G. Tranquille, J. L. Vallet, B. Vandorpe, U. Wehrle, J. Wenninger CERN, Geneva
	The CERN LHC experimental programme includes heavy ion physics with collisions between two counter-rotating Pb⁸²⁺ ion beams at a momentum of 2.76 TeV/c/nucleon per beam and luminosities as high as 1·10²⁷ cm^-2 s^-1. To achieve the beam parameters required for this operation the ion accelerator chain has undergone substantial modifications. Commissioning with beam of the various elements of this chain started in 2005 and in 2007 it was the turn of the final stage, the Super-Proton-Synchrotron (SPS) following extensive changes to the low-level RF hardware. The major limitations of this mode of operation of the SPS (space charge, intra-beam scattering) are presented, together with the performance reached so far. The status of the pre-injector performance will also be reviewed together with a description of the steps required to reach nominal performance.
TUPP065	Experimental Study of the Electron Cloud Instability in the CERN-SPS	1688
	G. Rumolo, G. Arduini, E. Benedetto, E. Métral, G. Papotti, E. N. Shaposhnikova CERN, Geneva R. Calaga BNL, Upton, Long Island, New York B. Salvant EPFL, Lausanne
	The electron cloud instability limits the performance of many existing proton and positron rings. A simulation study carried out with the HEADTAIL code revealed that the threshold for its onset decreases with increasing beam energy, if the 6D emittance of the bunch is kept constant and the longitudinal matching to the bucket is preserved. Experiments have been carried out at the CERN-SPS to study the dependence of the vertical electron cloud instability on the energy and on the beam size. The reduction of the physical transverse emittance as a function of energy is considered in fact to be the main reason for the unusual dependence of this instability on energy.
TUPP066	CERN SPS Impedance in 2007	1691
	E. Métral, G. Arduini, T. Bohl, H. Burkhardt, F. Caspers, H. Damerau, T. Kroyer, H. Medina, G. Rumolo, M. Schokker, E. N. Shaposhnikova, J. Tuckmantel CERN, Geneva R. Calaga BNL, Upton, Long Island, New York B. Salvant EPFL, Lausanne B. Spataro INFN/LNF, Frascati (Roma)
	Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet.
TUPP067	Transverse Mode-coupling Instability in the CERN SPS: Comparing MOSES Analytical Calculations and HEADTAIL Simulations with Experiments in the SPS	1694
	B. Salvant EPFL, Lausanne G. Arduini, E. Métral, G. Papotti, G. Rumolo, R. J. Steinhagen, R. Tomas CERN, Geneva R. Calaga BNL, Upton, Long Island, New York
	Since 2003, single bunches of protons with high intensity (1.2·10¹¹ protons) and low longitudinal emittance (0.2 eVs) have been observed to suffer from heavy losses in less than one synchrotron period after injection at 26 GeV/c in the CERN Super Proton Synchrotron (SPS) when the vertical chromaticity is corrected. Understanding the mechanisms underlying this instability is crucial to assess the feasibility of an anticipated upgrade of the SPS, which requires bunches of 4·10¹¹ protons. Analytical calculations from MOSES and macroparticle tracking simulations using HEADTAIL with an SPS transverse impedance modelled as a broadband resonator had already qualitatively and quantitatively agreed in predicting the intensity threshold of a fast instability. A sensitive frequency analysis of the HEADTAIL simulations output was then done using SUSSIX, and brought to light the fine structure of the mode spectrum of the bunch coherent motion. A coupling between the azimuthal modes -2 and -3 was clearly observed to be the reason for this fast instability. The aim of the present paper is to compare the HEADTAIL simulations with dedicated measurements performed in the SPS in 2007.
WEPP058	Optics Measurements and Matching of TT2-TT10 Line for Injection of the LHC Beam in the SPS	2650
	E. Benedetto, G. Arduini, A. Guerrero, D. Jacquet CERN, Geneva
	A well matched injection in the SPS is very important for preserving the emittance of the LHC beam. The paper presents the algorithms used for the analysis and the results of the optics measurements done in the transfer line TT2-TT10 and in the SPS. The dispersion is computed by varying the beam momentum and recording the offsets at the BPMs, while the Twiss parameters and emittance measurements in TT2-TT10 are performed with beam profile monitors equipped with OTR screens. These results are completed by those obtained with a matching monitor installed in the SPS as a prototype for the LHC. This device makes use of an OTR screen and a fast acquisition system, to get the turn by turn beam profiles right at injection in the ring, from which the beam mismatch is computed and compared with the results obtained in the line. Finally, on the basis of such measurments, a betatron and dispersion matching of TT2-TT10 for injection in the SPS has been performed and successfully put in operation.
WEPP065	Beam Commissioning of the SPS-to-LHC Transfer Line TI 2	2668
	J. A. Uythoven, G. Arduini, R. W. Assmann, N. Gilbert, B. Goddard, V. Kain, A. Koschik, T. Kramer, M. Lamont, V. Mertens, S. Redaelli, J. Wenninger CERN, Geneva
	The transfer line for the LHC Ring 1 was successfully commissioned with beam in the autumn of 2007. After extraction from the SPS accelerator and about 2.7 km of new transfer line, the beam arrived at the temporarily installed beam dump, about 50 m before the start of the LHC tunnel, without the need of any beam threading. This paper gives an overview of the hardware commissioning period and the actual beam tests carried out. It summarises the results of the beam test optics measurements and the performance of the installed hardware.