IPAC2013 - List of Authors (Wenninger, J.)

Paper

Title

Page

Proton-nucleus Collisions in the LHC

49

J.M. Jowett, R. Alemany-Fernandez, P. Baudrenghien, D. Jacquet, M. Lamont, D. Manglunki, S. Redaelli, M. Sapinski, M. Schaumann, M. Solfaroli Camillocci, R. Tomás, J.A. Uythoven, D. Valuch, R. Versteegen, J. Wenninger
CERN, Geneva, Switzerland

Following the high integrated luminosity accumulated in the first two Pb-Pb collision runs in 2010 and 2011, the LHC heavy-ion physics community requested a first run with p-Pb collisions. This almost unprecedented mode of collider operation was not foreseen in the baseline design of the LHC whose two-in-one magnet design imposed equal rigidity and, hence, unequal revolution frequencies, during injection and ramp. Nevertheless, after a successful pilot physics fill in 2012, the LHC provided 31 nb^-1 of p-Pb luminosity per experiment, at an energy of 5.02 TeV per colliding nucleon pair, with several variations of the operating conditions, in early 2013. Together with a companion p-p run at 2.76 TeV, this was the last physics before the present long shutdown. We summarise the beam physics, operational adaptations and strategy that resulted in extremely rapid commissioning. Finally, we give an account of the progress of the run and provide an analysis of the performance.

Slides MOODB201 [6.547 MB]

MOPEA058

CNGS, CERN Neutrinos to Gran Sasso, Five Years of Running a 500 Kilowatt Neutrino Beam Facility at CERN

211

E. Gschwendtner, K. Cornelis, I. Efthymiopoulos, A. Pardons, H. Vincke, J. Wenninger
CERN, Geneva, Switzerland
I. Krätschmer
HEPHY, Wien, Austria

The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon to tau neutrino oscillations where an intense muon-neutrino beam (10¹⁷ muon-neutrinos/day) is generated at CERN and directed over 732km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. The CNGS facility (CNGS Neutrinos to Gran Sasso) started with the physics program in 2008 and delivered until the end of the physics run 2012 more than 80% of the approved protons on target (22.5·10¹⁹ pot). An overview of the performance and experience gained in operating this 500kW neutrino beam facility is described. Major events since the commissioning of the facility in 2006 are summarized. Highlights on the CNGS beam performance are given.

MOPFI060

Beam Transfer to LHC with the Low Gamma-transition SPS Optics

419

G. Vanbavinckhove, W. Bartmann, H. Bartosik, C. Bracco, L.N. Drøsdal, B. Goddard, V. Kain, M. Meddahi, V. Mertens, Y. Papaphilippou, J.A. Uythoven, J. Wenninger
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, USA

A new low gamma-transition optics with a lower integer tune, was introduced in the SPS to improve beam stability at high intensity. For transferring the beam to the LHC, the extraction bumps, extraction kickers and transfer lines needed to be adapted to the new optics. In particular, the transfer lines were re-matched and re-commissioned with the new optics. The first operational results are discussed for the SPS extraction, the transfer lines and the LHC injection. A detailed comparison is presented between the old and the new optics of the trajectories, dispersion, losses and other performance aspects.

MOPWO033

Analysis of LHC Transfer Line Trajectory Drifts

960

L.N. Drøsdal, W. Bartmann, H. Bartosik, C. Bracco, B. Goddard, V. Kain, Y. Papaphilippou, J.A. Uythoven, G. Vanbavinckhove, J. Wenninger
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, USA

The LHC is filled from the SPS via two 3km long transfer lines. In the first years of LHC operation large trajectory variations were discovered. The sources of bunch-by-bunch and shot-by-shot trajectory variations had been identified and improved by the 2012 LHC run. The origins of the longer term drifts were however still unclear and significant time was spent correcting the trajectories. In the last part of the 2012 run the optics in the SPS was changed to lower transition energy. Trajectory stability and correction frequency will be compared between before and after the optics change in the SPS. The sources of the variations have now been identified and will be discussed in this paper. Remedies for operation after the long shutdown will be proposed.

TUPFI011

Study and Operational Implementation of a Tilted Crossing Angle in LHCb

1349

R. Alemany-Fernandez, F. Follin, B.J. Holzer, D. Jacquet, R. Versteegen, J. Wenninger
CERN, Geneva, Switzerland

The current crossing angle scheme at LHCb interaction point (horizontal crossing angle and vertical beam separation) prohibits the use of the LHCb dipole positive polarity for 25 ns bunch spacing operation since the beam separation at the first parasitic encounter is very small inducing unwanted beam encounters. To overcome this limitation a different crossing angle scheme was proposed in 2007 by W. Herr and Y. Papaphilippou. The new schema implies a vertical external crossing angle that together with the horizontal internal crossing angle, from the LHCb dipole and its three compensator magnets, defines a new tilted crossing and separation plane providing enough beam separation at the parasitic encounters. This paper summarizes the feasibility study of the new crossing scheme, the implementation in routine operation and analyzes the beam stability during the building up of the tilted crossing plane.

TUPFI033

Colliding During the Squeeze and β* Leveling in the LHC

1415

X. Buffat
EPFL, Lausanne, Switzerland
W. Herr, M. Lamont, T. Pieloni, S. Redaelli, J. Wenninger
CERN, Geneva, Switzerland

While more challenging operationally, bringing the beams into collisions during the β squeeze rather than after presents some advantages. The large tune spread arising from the non-linearity of head-on beam-beam interactions can damp impedance-driven instabilities much more efficiently than external non-linearity such as octupoles presently used in operation. Moreover, colliding during the squeeze allows to level the luminosity, optimizing the pile-up in the experiments without changing the longitudinal distribution of collisions. Operational issues are discussed and experimental results from the LHC are presented.

TUPFI034

Observations of Two-beam Instabilities during the 2012 LHC Physics Run

1418

T. Pieloni
EPFL, Lausanne, Switzerland
G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger
CERN, Geneva, Switzerland
S.M. White
BNL, Upton, Long Island, New York, USA

During the 2012 run coherent beam instabilities have been observed in the LHC at 4 TeV, during the betatron squeeze and in collision for special filling patterns. Several studies to characterize these instabilities have been carried out during operation and in special dedicated experiments. In this paper we summarize the observations collected for different machine parameters and the present understanding of the origin of these instabilities.

TUPFI038

Operation of the Betatron Squeeze at the LHC

1430

S. Redaelli, X. Buffat, M. Lamont, G.J. Müller, M. Solfaroli Camillocci, R. Tomás, J. Wenninger
CERN, Geneva, Switzerland
G.J. Müller
TU Dresden, Dresden, Germany

The betatron squeeze is one of the most delicate operational phases at the large Hadron collider as it entails changes of optics performed at top energy, with full intensities. Appropriate software was developed to handle the squeeze, which ensured an efficient commissioning down to a β^* of 60 cm and a smooth operation. Several optics configurations could be commissioned and put in operation for physics. The operational experience of the LHC runs from 2010 until 2012 is presented and the overall performance reviewed.

TUPFI041

Operating the LHC Off-momentum for p-Pb Collisions

1439

R. Versteegen, R. Bruce, J.M. Jowett, A. Langner, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, T. Persson, S. Redaelli, B. Salvachua, P. Skowroński, M. Solfaroli Camillocci, R. Tomás, G. Valentino, J. Wenninger
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom
M.J. McAteer
The University of Texas at Austin, Austin, USA
T. Persson
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
G. Valentino
University of Malta, Information and Communication Technology, Msida, Malta
S.M. White
BNL, Upton, Long Island, New York, USA

The first high-luminosity p-Pb run at the LHC took place in January-February 2013 at an energy of 4 Z TeV per beam. The RF frequency difference of proton and Pb is about 60 Hz for equal magnetic rigidities, which means that beams move slightly to off-momentum, non-central, orbits during physics when frequencies are locked together. The resulting optical perturbations ("beta-beating") restrict the available aperture and required a special correction. This was also the first operation of the LHC with low beta in all four experiments and required a specific collimation set up. Predictions from offline calculations of beta-beating correction are compared with measurements during the optics commissioning and collimator set up.

TUPME032

Update on Beam Induced RF Heating in the LHC

1646

B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, W. Bartmann, P. Baudrenghien, O.E. Berrig, A. Bertarelli, C. Bracco, E. Bravin, G. Bregliozzi, R. Bruce, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, M. Deile, J.F. Esteban Müller, P. Fassnacht, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, S. Jakobsen, O.R. Jones, O. Kononenko, G. Lanza, L. Lari, T. Mastoridis, V. Mertens, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, R. Schmidt, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
H.A. Day
UMAN, Manchester, United Kingdom
L. Lari
IFIC, Valencia, Spain

Since June 2011, the rapid increase of the luminosity performance of the LHC has come at the expense of increased temperature and pressure readings on specific near-beam LHC equipment. In some cases, this beam induced heating has caused delays whilie equipment cools down, beam dumps and even degradation of these devices. This contribution gathers the observations of beam induced heating attributable to beam coupling impedance, their current level of understanding and possible actions that are planned to be implemented during the long shutdown in 2013-2014.

TUPWO048

Understanding the Tune, Coupling, and Chromaticity Dependence of the LHC on Landau Octupole Powering

1976

E.H. Maclean, M. Giovannozzi, W. Herr, Y.I. Levinsen, G. Papotti, T. Persson, P. Skowroński, R. Tomás, J. Wenninger
CERN, Geneva, Switzerland

During the 2012 LHC run there were several observations of unexpectedly large shifts to the tune, chromaticity, and coupling which were correlated with changes in the powering of Landau octupoles (MO). Understanding the chromaticity dependence is of particular importance given it's influence on instabilities. This paper summarizes the observations and our attempts to-date to understand the relationship between Q, Q', c- and the MO powering.

TUPWO050

Commissioning and Operation at β^* = 1000 m in the LHC

1982

H. Burkhardt, T. Persson, R. Tomás, J. Wenninger
CERN, Geneva, Switzerland
S. Cavalier
LAL, Orsay, France

We have developed a special optics with a β^* of 1000 m for two interaction regions (IR1 and IR5) in the LHC, to produce very low divergence beams required for elastic proton-proton scattering. We describe the design, commissioning and operation of this optics in the LHC. The β^* of 1000 m was reached by de-squeezing the beams using 17 intermediate steps beyond the β^* of 90 m, which had been the previous highest β^* value reached in the LHC. The optics was measured and the beta beating globally corrected to a level of 10 per cent.

WEPEA061

The First LHC p-Pb run: Performance of the Heavy Ion Production Complex

2648

D. Manglunki, M. E. Angoletta, H. Bartosik, G. Bellodi, A. Blas, M.A. Bodendorfer, T. Bohl, C. Carli, E. Carlier, S. Cettour Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, J.M. Jowett, D. Kuchler, M. O'Neil, Y. Papaphilippou, S. Pasinelli, R. Scrivens, G. Tranquille, B. Vandorpe, U. Wehrle, J. Wenninger
CERN, Geneva, Switzerland

TThe first LHC proton-ion run took place in January-February 2013; it was the first extension to the collider programme, as this mode was not included in the design report. This paper presents the performance of the heavy ion and proton production complex, and details the issues encountered, in particular the creation of the same bunch pattern in both beams.

THPEA040

Design of a Magnetic Bump Tail Scraping System for the CERN SPS

3228

Ö. Mete, J. Bauche, F. Cerutti, S. Cettour Cave, K. Cornelis, L.N. Drøsdal, F. Galleazzi, B. Goddard, L.K. Jensen, V. Kain, Y. Le Borgne, G. Le Godec, M. Meddahi, E. Veyrunes, H. Vincke, J. Wenninger
CERN, Geneva, Switzerland
A. Mereghetti
UMAN, Manchester, United Kingdom

The LHC injectors are being upgraded to meet the demanding beam specification required for High Luminosity LHC (HL-LHC) operation. In order to reduce the beam losses which can trigger the sensitive LHC beam loss interlocks during the SPS-to-LHC beam injection process, it is important that the beam tails are properly scraped away in the SPS. The current SPS tail cleaning system relies on a moveable scraper blade, with the positioning of the scraper adjusted over time according to the orbit variations of the SPS. A new robust beam tail cleaning system has been designed which will use a fixed scraper block towards which the beam will be moved by a local magnetic orbit bump. The design proposal is presented, together with the related beam dynamics studies and results from machine studies with beam.

THPEA045

Beam Induced Quenches of LHC Magnets

3243

M. Sapinski, T. Baer, M. Bednarek, G. Bellodi, C. Bracco, R. Bruce, B. Dehning, W. Höfle, A. Lechner, E. Nebot Del Busto, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland

In the years 2009-2013 LHC was operating with the beam energy of 3.5 and 4 TeV instead of the nominal 7 TeV, with the corresponding currents in the superconducting magnets also half nominal. To date only a small number of beam-induced quenches have occurred, with most being due to specially designed quench tests. During normal collider operation with stored beam there has not been a single beam induced quench. This excellent result is mainly explained by the fact that the cleaning of the beam halo worked very well and, in case of beam losses, the beam was dumped before any significant energy was deposited in the magnets. However, conditions are expected to become much tougher after the long LHC shutdown, when the magnets will be working at near nominal currents in the presence of high energy and intensity beams. This paper summarizes the experience to date with beam-induced quenches. It describes the techniques used to generate controlled quench conditions which were used to study the limitations. Results are discussed along with their implication for LHC operation after the first Long Shutdown.

THPEA046

Machine Protection at the LHC - Experience of Three Years Running and Outlook for Operation at Nominal Energy

3246

D. Wollmann, R. Schmidt, J. Wenninger, M. Zerlauth
CERN, Geneva, Switzerland

With above 22fb-1 integrated luminosity delivered to the experiments ATLAS and CMS the LHC surpassed the results of 2011 by more than a factor 5. This was achieved at 4TeV, with intensities of ~2e14p per beam. The uncontrolled loss of only a small fraction of the stored beam is sufficient to damage parts of the sc. magnet system, accelerator equipment or the particle physics experiments. To protect against this a correct functioning of the complex LHC machine protection (MP) systems through the operational cycle is essential. Operating with up to 140MJ stored beam energy was only possible due to the experience and confidence gained in the two previous running periods, where the intensity was slowly increased. In this paper the 2012 performance of the MP systems is discussed. The strategy applied for a fast, but safe, intensity ramp up and the monitoring of the MP systems during stable running periods are presented. Weaknesses in the reliability of the MP systems, set-up procedures and setting adjustments for machine development periods, discovered in 2012, are critically reviewed and improvements for the LHC operation after the up-coming long shut-down of the LHC are proposed.

THPWO080

Operational Performance of the LHC Proton Beams with the SPS Low Transition Energy Optics

3945

Y. Papaphilippou, G. Arduini, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, C. Bracco, S. Cettour-Cave, K. Cornelis, L.N. Drøsdal, J.F. Esteban Müller, B. Goddard, A. Guerrero, W. Höfle, V. Kain, G. Rumolo, B. Salvant, E.N. Shaposhnikova, H. Timko, D. Valuch, G. Vanbavinckhove, J. Wenninger
CERN, Geneva, Switzerland
E. Gianfelice-Wendt
Fermilab, Batavia, USA

An optics in the SPS with lower integer tunes (20 versus 26) was proposed and introduced in machine studies since 2010, as a measure for increasing transverse and longitudinal instability thresholds, especially at low energy, for the LHC proton beams. After two years of machine studies and careful optimisation, the new “Q20” optics became operational in September 2012 and steadily delivered beam to the LHC until the end of the run. This paper reviews the operational performance of the Q20 optics with respect to transverse and longitudinal beam characteristics in the SPS, enabling high brightness beams injected into the LHC. Aspects of longitudinal beam stability, transmission, high-energy orbit control and beam transfer are discussed.

Paper	Title	Page
MOODB201	Proton-nucleus Collisions in the LHC	49
	J.M. Jowett, R. Alemany-Fernandez, P. Baudrenghien, D. Jacquet, M. Lamont, D. Manglunki, S. Redaelli, M. Sapinski, M. Schaumann, M. Solfaroli Camillocci, R. Tomás, J.A. Uythoven, D. Valuch, R. Versteegen, J. Wenninger CERN, Geneva, Switzerland
	Following the high integrated luminosity accumulated in the first two Pb-Pb collision runs in 2010 and 2011, the LHC heavy-ion physics community requested a first run with p-Pb collisions. This almost unprecedented mode of collider operation was not foreseen in the baseline design of the LHC whose two-in-one magnet design imposed equal rigidity and, hence, unequal revolution frequencies, during injection and ramp. Nevertheless, after a successful pilot physics fill in 2012, the LHC provided 31 nb^-1 of p-Pb luminosity per experiment, at an energy of 5.02 TeV per colliding nucleon pair, with several variations of the operating conditions, in early 2013. Together with a companion p-p run at 2.76 TeV, this was the last physics before the present long shutdown. We summarise the beam physics, operational adaptations and strategy that resulted in extremely rapid commissioning. Finally, we give an account of the progress of the run and provide an analysis of the performance.
	Slides MOODB201 [6.547 MB]

MOPEA058	CNGS, CERN Neutrinos to Gran Sasso, Five Years of Running a 500 Kilowatt Neutrino Beam Facility at CERN	211
	E. Gschwendtner, K. Cornelis, I. Efthymiopoulos, A. Pardons, H. Vincke, J. Wenninger CERN, Geneva, Switzerland I. Krätschmer HEPHY, Wien, Austria
	The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon to tau neutrino oscillations where an intense muon-neutrino beam (10¹⁷ muon-neutrinos/day) is generated at CERN and directed over 732km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. The CNGS facility (CNGS Neutrinos to Gran Sasso) started with the physics program in 2008 and delivered until the end of the physics run 2012 more than 80% of the approved protons on target (22.5·10¹⁹ pot). An overview of the performance and experience gained in operating this 500kW neutrino beam facility is described. Major events since the commissioning of the facility in 2006 are summarized. Highlights on the CNGS beam performance are given.

MOPFI060	Beam Transfer to LHC with the Low Gamma-transition SPS Optics	419
	G. Vanbavinckhove, W. Bartmann, H. Bartosik, C. Bracco, L.N. Drøsdal, B. Goddard, V. Kain, M. Meddahi, V. Mertens, Y. Papaphilippou, J.A. Uythoven, J. Wenninger CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, USA
	A new low gamma-transition optics with a lower integer tune, was introduced in the SPS to improve beam stability at high intensity. For transferring the beam to the LHC, the extraction bumps, extraction kickers and transfer lines needed to be adapted to the new optics. In particular, the transfer lines were re-matched and re-commissioned with the new optics. The first operational results are discussed for the SPS extraction, the transfer lines and the LHC injection. A detailed comparison is presented between the old and the new optics of the trajectories, dispersion, losses and other performance aspects.

MOPWO033	Analysis of LHC Transfer Line Trajectory Drifts	960
	L.N. Drøsdal, W. Bartmann, H. Bartosik, C. Bracco, B. Goddard, V. Kain, Y. Papaphilippou, J.A. Uythoven, G. Vanbavinckhove, J. Wenninger CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, USA
	The LHC is filled from the SPS via two 3km long transfer lines. In the first years of LHC operation large trajectory variations were discovered. The sources of bunch-by-bunch and shot-by-shot trajectory variations had been identified and improved by the 2012 LHC run. The origins of the longer term drifts were however still unclear and significant time was spent correcting the trajectories. In the last part of the 2012 run the optics in the SPS was changed to lower transition energy. Trajectory stability and correction frequency will be compared between before and after the optics change in the SPS. The sources of the variations have now been identified and will be discussed in this paper. Remedies for operation after the long shutdown will be proposed.

TUPFI011	Study and Operational Implementation of a Tilted Crossing Angle in LHCb	1349
	R. Alemany-Fernandez, F. Follin, B.J. Holzer, D. Jacquet, R. Versteegen, J. Wenninger CERN, Geneva, Switzerland
	The current crossing angle scheme at LHCb interaction point (horizontal crossing angle and vertical beam separation) prohibits the use of the LHCb dipole positive polarity for 25 ns bunch spacing operation since the beam separation at the first parasitic encounter is very small inducing unwanted beam encounters. To overcome this limitation a different crossing angle scheme was proposed in 2007 by W. Herr and Y. Papaphilippou. The new schema implies a vertical external crossing angle that together with the horizontal internal crossing angle, from the LHCb dipole and its three compensator magnets, defines a new tilted crossing and separation plane providing enough beam separation at the parasitic encounters. This paper summarizes the feasibility study of the new crossing scheme, the implementation in routine operation and analyzes the beam stability during the building up of the tilted crossing plane.

TUPFI033	Colliding During the Squeeze and β* Leveling in the LHC	1415
	X. Buffat EPFL, Lausanne, Switzerland W. Herr, M. Lamont, T. Pieloni, S. Redaelli, J. Wenninger CERN, Geneva, Switzerland
	While more challenging operationally, bringing the beams into collisions during the β squeeze rather than after presents some advantages. The large tune spread arising from the non-linearity of head-on beam-beam interactions can damp impedance-driven instabilities much more efficiently than external non-linearity such as octupoles presently used in operation. Moreover, colliding during the squeeze allows to level the luminosity, optimizing the pile-up in the experiments without changing the longitudinal distribution of collisions. Operational issues are discussed and experimental results from the LHC are presented.

TUPFI034	Observations of Two-beam Instabilities during the 2012 LHC Physics Run	1418
	T. Pieloni EPFL, Lausanne, Switzerland G. Arduini, X. Buffat, R. Giachino, W. Herr, M. Lamont, N. Mounet, E. Métral, G. Papotti, B. Salvant, J. Wenninger CERN, Geneva, Switzerland S.M. White BNL, Upton, Long Island, New York, USA
	During the 2012 run coherent beam instabilities have been observed in the LHC at 4 TeV, during the betatron squeeze and in collision for special filling patterns. Several studies to characterize these instabilities have been carried out during operation and in special dedicated experiments. In this paper we summarize the observations collected for different machine parameters and the present understanding of the origin of these instabilities.

TUPFI038	Operation of the Betatron Squeeze at the LHC	1430
	S. Redaelli, X. Buffat, M. Lamont, G.J. Müller, M. Solfaroli Camillocci, R. Tomás, J. Wenninger CERN, Geneva, Switzerland G.J. Müller TU Dresden, Dresden, Germany
	The betatron squeeze is one of the most delicate operational phases at the large Hadron collider as it entails changes of optics performed at top energy, with full intensities. Appropriate software was developed to handle the squeeze, which ensured an efficient commissioning down to a β^* of 60 cm and a smooth operation. Several optics configurations could be commissioned and put in operation for physics. The operational experience of the LHC runs from 2010 until 2012 is presented and the overall performance reviewed.

TUPFI041	Operating the LHC Off-momentum for p-Pb Collisions	1439
	R. Versteegen, R. Bruce, J.M. Jowett, A. Langner, Y.I. Levinsen, E.H. Maclean, M.J. McAteer, T. Persson, S. Redaelli, B. Salvachua, P. Skowroński, M. Solfaroli Camillocci, R. Tomás, G. Valentino, J. Wenninger CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom M.J. McAteer The University of Texas at Austin, Austin, USA T. Persson Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden G. Valentino University of Malta, Information and Communication Technology, Msida, Malta S.M. White BNL, Upton, Long Island, New York, USA
	The first high-luminosity p-Pb run at the LHC took place in January-February 2013 at an energy of 4 Z TeV per beam. The RF frequency difference of proton and Pb is about 60 Hz for equal magnetic rigidities, which means that beams move slightly to off-momentum, non-central, orbits during physics when frequencies are locked together. The resulting optical perturbations ("beta-beating") restrict the available aperture and required a special correction. This was also the first operation of the LHC with low beta in all four experiments and required a specific collimation set up. Predictions from offline calculations of beta-beating correction are compared with measurements during the optics commissioning and collimator set up.

TUPME032	Update on Beam Induced RF Heating in the LHC	1646
	B. Salvant, O. Aberle, G. Arduini, R.W. Aßmann, V. Baglin, M.J. Barnes, W. Bartmann, P. Baudrenghien, O.E. Berrig, A. Bertarelli, C. Bracco, E. Bravin, G. Bregliozzi, R. Bruce, F. Carra, F. Caspers, G. Cattenoz, S.D. Claudet, H.A. Day, M. Deile, J.F. Esteban Müller, P. Fassnacht, M. Garlaschè, L. Gentini, B. Goddard, A. Grudiev, B. Henrist, S. Jakobsen, O.R. Jones, O. Kononenko, G. Lanza, L. Lari, T. Mastoridis, V. Mertens, N. Mounet, E. Métral, A.A. Nosych, J.L. Nougaret, S. Persichelli, A.M. Piguiet, S. Redaelli, F. Roncarolo, G. Rumolo, B. Salvachua, M. Sapinski, R. Schmidt, E.N. Shaposhnikova, L.J. Tavian, M.A. Timmins, J.A. Uythoven, A. Vidal, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland H.A. Day UMAN, Manchester, United Kingdom L. Lari IFIC, Valencia, Spain
	Since June 2011, the rapid increase of the luminosity performance of the LHC has come at the expense of increased temperature and pressure readings on specific near-beam LHC equipment. In some cases, this beam induced heating has caused delays whilie equipment cools down, beam dumps and even degradation of these devices. This contribution gathers the observations of beam induced heating attributable to beam coupling impedance, their current level of understanding and possible actions that are planned to be implemented during the long shutdown in 2013-2014.

TUPWO048	Understanding the Tune, Coupling, and Chromaticity Dependence of the LHC on Landau Octupole Powering	1976
	E.H. Maclean, M. Giovannozzi, W. Herr, Y.I. Levinsen, G. Papotti, T. Persson, P. Skowroński, R. Tomás, J. Wenninger CERN, Geneva, Switzerland
	During the 2012 LHC run there were several observations of unexpectedly large shifts to the tune, chromaticity, and coupling which were correlated with changes in the powering of Landau octupoles (MO). Understanding the chromaticity dependence is of particular importance given it's influence on instabilities. This paper summarizes the observations and our attempts to-date to understand the relationship between Q, Q', c- and the MO powering.

TUPWO050	Commissioning and Operation at β^* = 1000 m in the LHC	1982
	H. Burkhardt, T. Persson, R. Tomás, J. Wenninger CERN, Geneva, Switzerland S. Cavalier LAL, Orsay, France
	We have developed a special optics with a β^* of 1000 m for two interaction regions (IR1 and IR5) in the LHC, to produce very low divergence beams required for elastic proton-proton scattering. We describe the design, commissioning and operation of this optics in the LHC. The β^* of 1000 m was reached by de-squeezing the beams using 17 intermediate steps beyond the β^* of 90 m, which had been the previous highest β^* value reached in the LHC. The optics was measured and the beta beating globally corrected to a level of 10 per cent.

WEPEA061	The First LHC p-Pb run: Performance of the Heavy Ion Production Complex	2648
	D. Manglunki, M. E. Angoletta, H. Bartosik, G. Bellodi, A. Blas, M.A. Bodendorfer, T. Bohl, C. Carli, E. Carlier, S. Cettour Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, J.M. Jowett, D. Kuchler, M. O'Neil, Y. Papaphilippou, S. Pasinelli, R. Scrivens, G. Tranquille, B. Vandorpe, U. Wehrle, J. Wenninger CERN, Geneva, Switzerland
	TThe first LHC proton-ion run took place in January-February 2013; it was the first extension to the collider programme, as this mode was not included in the design report. This paper presents the performance of the heavy ion and proton production complex, and details the issues encountered, in particular the creation of the same bunch pattern in both beams.

THPEA040	Design of a Magnetic Bump Tail Scraping System for the CERN SPS	3228
	Ö. Mete, J. Bauche, F. Cerutti, S. Cettour Cave, K. Cornelis, L.N. Drøsdal, F. Galleazzi, B. Goddard, L.K. Jensen, V. Kain, Y. Le Borgne, G. Le Godec, M. Meddahi, E. Veyrunes, H. Vincke, J. Wenninger CERN, Geneva, Switzerland A. Mereghetti UMAN, Manchester, United Kingdom
	The LHC injectors are being upgraded to meet the demanding beam specification required for High Luminosity LHC (HL-LHC) operation. In order to reduce the beam losses which can trigger the sensitive LHC beam loss interlocks during the SPS-to-LHC beam injection process, it is important that the beam tails are properly scraped away in the SPS. The current SPS tail cleaning system relies on a moveable scraper blade, with the positioning of the scraper adjusted over time according to the orbit variations of the SPS. A new robust beam tail cleaning system has been designed which will use a fixed scraper block towards which the beam will be moved by a local magnetic orbit bump. The design proposal is presented, together with the related beam dynamics studies and results from machine studies with beam.

THPEA045	Beam Induced Quenches of LHC Magnets	3243
	M. Sapinski, T. Baer, M. Bednarek, G. Bellodi, C. Bracco, R. Bruce, B. Dehning, W. Höfle, A. Lechner, E. Nebot Del Busto, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland
	In the years 2009-2013 LHC was operating with the beam energy of 3.5 and 4 TeV instead of the nominal 7 TeV, with the corresponding currents in the superconducting magnets also half nominal. To date only a small number of beam-induced quenches have occurred, with most being due to specially designed quench tests. During normal collider operation with stored beam there has not been a single beam induced quench. This excellent result is mainly explained by the fact that the cleaning of the beam halo worked very well and, in case of beam losses, the beam was dumped before any significant energy was deposited in the magnets. However, conditions are expected to become much tougher after the long LHC shutdown, when the magnets will be working at near nominal currents in the presence of high energy and intensity beams. This paper summarizes the experience to date with beam-induced quenches. It describes the techniques used to generate controlled quench conditions which were used to study the limitations. Results are discussed along with their implication for LHC operation after the first Long Shutdown.

THPEA046	Machine Protection at the LHC - Experience of Three Years Running and Outlook for Operation at Nominal Energy	3246
	D. Wollmann, R. Schmidt, J. Wenninger, M. Zerlauth CERN, Geneva, Switzerland
	With above 22fb-1 integrated luminosity delivered to the experiments ATLAS and CMS the LHC surpassed the results of 2011 by more than a factor 5. This was achieved at 4TeV, with intensities of ~2e14p per beam. The uncontrolled loss of only a small fraction of the stored beam is sufficient to damage parts of the sc. magnet system, accelerator equipment or the particle physics experiments. To protect against this a correct functioning of the complex LHC machine protection (MP) systems through the operational cycle is essential. Operating with up to 140MJ stored beam energy was only possible due to the experience and confidence gained in the two previous running periods, where the intensity was slowly increased. In this paper the 2012 performance of the MP systems is discussed. The strategy applied for a fast, but safe, intensity ramp up and the monitoring of the MP systems during stable running periods are presented. Weaknesses in the reliability of the MP systems, set-up procedures and setting adjustments for machine development periods, discovered in 2012, are critically reviewed and improvements for the LHC operation after the up-coming long shut-down of the LHC are proposed.

THPWO080	Operational Performance of the LHC Proton Beams with the SPS Low Transition Energy Optics	3945
	Y. Papaphilippou, G. Arduini, T. Argyropoulos, W. Bartmann, H. Bartosik, T. Bohl, C. Bracco, S. Cettour-Cave, K. Cornelis, L.N. Drøsdal, J.F. Esteban Müller, B. Goddard, A. Guerrero, W. Höfle, V. Kain, G. Rumolo, B. Salvant, E.N. Shaposhnikova, H. Timko, D. Valuch, G. Vanbavinckhove, J. Wenninger CERN, Geneva, Switzerland E. Gianfelice-Wendt Fermilab, Batavia, USA
	An optics in the SPS with lower integer tunes (20 versus 26) was proposed and introduced in machine studies since 2010, as a measure for increasing transverse and longitudinal instability thresholds, especially at low energy, for the LHC proton beams. After two years of machine studies and careful optimisation, the new “Q20” optics became operational in September 2012 and steadily delivered beam to the LHC until the end of the run. This paper reviews the operational performance of the Q20 optics with respect to transverse and longitudinal beam characteristics in the SPS, enabling high brightness beams injected into the LHC. Aspects of longitudinal beam stability, transmission, high-energy orbit control and beam transfer are discussed.