HB2012 - List of Authors (Cauchi, M.)

Paper	Title	Page
MOP242	Experimental Verification for a Collimator with In-jaw Beam Position Monitors	146
	D. Wollmann, O. Aberle, R.W. Aßmann, A. Bertarelli, C.B. Boccard, R. Bruce, F. Burkart, M. Cauchi, A. Dallocchio, D. Deboy, M. Gasior, O.R. Jones, V. Kain, L. Lari, A.A. Nosych, S. Redaelli, A. Rossi, G. Valentino CERN, Geneva, Switzerland
	At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.

MOP245	Quench Tests at the Large Hadron Collider with Collimation Losses at 3.5 Z TeV	157
	S. Redaelli, R.W. Aßmann, G. Bellodi, K. Brodzinski, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, B. Dehning, E.B. Holzer, J.M. Jowett, E. Nebot Del Busto, M. Pojer, A. Priebe, A. Rossi, M. Sapinski, M. Schaumann, R. Schmidt, M. Solfaroli Camillocci, G. Valentino, R. Versteegen, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	The Large Hadron Collider (LHC) has been operating since 2010 at 3.5 TeV and 4.0 TeV without experiencing quenches induced by losses from circulating beams. This situation might change at 7 TeV where the reduced margins in the superconducting magnets. The critical locations are the dispersion suppressors (DSs) at either side of the cleaning and experimental insertions, where dispersive losses are maximum. It is therefore crucial to understand in detail the quench limits with beam loss distributions alike those occurring in standard operation. In order to address this aspect, quench tests were performed by inducing large beam losses on the primary collimators of the betatron cleaning insertion, for proton and lead ion beams of 3.5 Z TeV, to probe the quench limits of the DS magnets. Losses up to 500 kW were achieved without quenches. The measurement technique and the results obtained are presented, including observations of heat loads in the cryogenics system.

Paper

Title

Page

Experimental Verification for a Collimator with In-jaw Beam Position Monitors

146

D. Wollmann, O. Aberle, R.W. Aßmann, A. Bertarelli, C.B. Boccard, R. Bruce, F. Burkart, M. Cauchi, A. Dallocchio, D. Deboy, M. Gasior, O.R. Jones, V. Kain, L. Lari, A.A. Nosych, S. Redaelli, A. Rossi, G. Valentino
CERN, Geneva, Switzerland

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.

MOP245

Quench Tests at the Large Hadron Collider with Collimation Losses at 3.5 Z TeV

157

S. Redaelli, R.W. Aßmann, G. Bellodi, K. Brodzinski, R. Bruce, F. Burkart, M. Cauchi, D. Deboy, B. Dehning, E.B. Holzer, J.M. Jowett, E. Nebot Del Busto, M. Pojer, A. Priebe, A. Rossi, M. Sapinski, M. Schaumann, R. Schmidt, M. Solfaroli Camillocci, G. Valentino, R. Versteegen, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

The Large Hadron Collider (LHC) has been operating since 2010 at 3.5 TeV and 4.0 TeV without experiencing quenches induced by losses from circulating beams. This situation might change at 7 TeV where the reduced margins in the superconducting magnets. The critical locations are the dispersion suppressors (DSs) at either side of the cleaning and experimental insertions, where dispersive losses are maximum. It is therefore crucial to understand in detail the quench limits with beam loss distributions alike those occurring in standard operation. In order to address this aspect, quench tests were performed by inducing large beam losses on the primary collimators of the betatron cleaning insertion, for proton and lead ion beams of 3.5 Z TeV, to probe the quench limits of the DS magnets. Losses up to 500 kW were achieved without quenches. The measurement technique and the results obtained are presented, including observations of heat loads in the cryogenics system.