IPAC2011 - List of Authors (Tomas, R.)

Paper

Title

Page

Status of the ATF2 Lattices

1027

E. Marin, R. Tomás
CERN, Geneva, Switzerland
P. Bambade
LAL, Orsay, France
T. Okugi, T. Tauchi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
A. Seryi
JAI, Oxford, United Kingdom
G.R. White, M. Woodley
SLAC, Menlo Park, California, USA

The latest status for the ATF2 Nominal and Ultra-low beta lattices designs obtained to minimize the detrimental effect of the measured multipoles are presented in this paper. A set of correction knobs for the most important aberrations at the IP have been obtained for both lattices in order to perform the tuning under realistic imperfections. Starting from the tuned ATF2 Nominal lattice a squeeze sequence reducing beta_y is performed to reach the ultra-low beta lattice. Tuning results are shown for both options.

TUPZ001

90 m Optics Commissioning

1795

S. Cavalier
LAL, Orsay, France
H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger
CERN, Geneva, Switzerland

Special β* = 90 m optics have been developed for the two very high luminosity insertions of the LHC, as a first step towards to allow for very low angle precision measurements of the proton-proton collisions in the LHC. These optics were developed to be compatible with the standard LHC injection and ramp optics. The target value of β* = 90 m is reached by an un-squeeze from the injection β* = 11 m. We describe the implementation of this optics in the LHC and the first experience in the commissioning of these optics.

TUPZ006

Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan

1810

R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann
CERN, Geneva, Switzerland
M. Alabau
IFIC, Valencia, Spain

A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in σs of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.

TUPZ009

LHC Machine Protection against Very Fast Crab Cavity Failures

1816

T. Baer, R. Tomás, J. Tückmantel, J. Wenninger, F. Zimmermann
CERN, Geneva, Switzerland
T. Baer
Uni HH, Hamburg, Germany
R. Calaga
BNL, Upton, Long Island, New York, USA

For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is essential to compensate the geometric luminosity loss due to the crossing angle. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a CC quench), the voltage and/or phase of a CC can change significantly with a fast time constant of the order of a LHC turn. This can lead to large, global betatron oscillations of the beam. Against the background of machine protection, the influence of a CC failure on the beam dynamics is discussed. The results from dedicated tracking studies, including the LHC upgrade optics, are presented. Necessary countermeasures to limit the impact of CC failures to an acceptable level are proposed.

TUPZ026

Alternative Working Point(s) at Injection for the LHC

1861

R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
R. Tomás
CERN, Geneva, Switzerland
G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands

Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP).
At present, the LHC operates with a different fractional tunes at injection and at collision energy due to improved dynamic aperture indicated by tracking studies. Therefore, a tune swing crossing the 10th order resonance is needed during the beta-squeeze. A new proposal to alter the working point to collision tunes already at injection and during an energy ramp is foreseen to avoid the tune jump. Simulations and measurements of the optics along with the beam emittances and lifetime are compared to the nominal injection tunes. Feasibility for a working point close to the 1/2 integer is also attempted.

TUPZ027

Beta* Measurement in the LHC Based on K-modulation

1864

R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
R. Tomás
CERN, Geneva, Switzerland
G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands

Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP).
Accurate knowledge of the collision point optics is crucial to equalize the luminosities at the different experiments. K-modulation was successfully applied at several accelerators for measuring the lattice beta functions. In the LHC, it was proposed as an alternative method to compute the beta* at the collision points. Results of beta* measurements in the LHC based on the K-modulation technique are presented with comparisons to nominal segment-by-segment method.

TUPZ034

Impact of Arc Phase Advance on Chromatic Optics in RHIC

1885

R. Calaga, R. Miyamoto, G. Robert-Demolaize, S.M. White
BNL, Upton, Long Island, New York, USA
R. De Maria, R. Tomás
CERN, Geneva, Switzerland
G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands

Funding: This work is partially supported by the US Department of Energy through the LHC Accelerator Research program (LARP).
The phase advance between the two interaction points in RHIC is optimized for dynamic aperture for a initial design beta-star. This may not hold true as RHIC presently operates with a considerably reduced beta-star. Additionally the reduction of the available beam aperture due to an enlarged chromatic beta-beating is evident. Results from phase advance scans between the two IPs to reduce the chromatic beta-beating in model and measurements are presented. Impact on the single beam lifetime and momentum aperture is compared to the nominal optics.

WEPC004

Comparison of the Action and Phase Analysis on LHC Orbits with Other Techniques

2004

J.F. Cardona
UNAL, Bogota D.C, Colombia
R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
R. Tomás
CERN, Geneva, Switzerland
G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands

Funding: DIB-Universidad Nacional de Colombia
Recently acquired turn-by-turn data of the LHC is analyzed using the action and phase jump technique. The results of this analysis show a visible variation of the action and phase plots at the interaction regions from which optic error estimations can be done. In this paper error estimations will be presented and comparisons with other existing techniques in the LHC, such as the recently implemented Segment-by-segment technique, will be discussed.

WEPC028

Record Low Beta-beat of 10% in the LHC

2061

G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands
M. Aiba
PSI, Villigen, Switzerland
R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
R. Tomás
CERN, Geneva, Switzerland

During the 2011 LHC run several measurements and correction campaigns were conducted. As a result a peak beta-beat of 10% level was achieved. This level, well below the specified tolerances of the LHC, improves the aperture margins and helps minimize the luminosity imbalance between the different experiments. A combination of local corrections at the insertion regions and an overall global correction were used to achieve this record low beta-beat. The sequence of the optics corrections and stability along the 2011 run are reported.

WEPC029

Accuracy of the LHC Optics Measurement based on AC Dipoles

2064

R. Miyamoto, R. Calaga
BNL, Upton, Long Island, New York, USA
R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland

Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
The tight tolerances in the LHC requires optics measurement with very good accuracy. Therefore, AC dipoles are employed as the primary devices to measure the LHC optics. The accuracy of the measurement is mainly determined by the length of the coherent signal, signal-to-noise ratio of the measurement, and the data processing to effectively suppress the noise. This paper presents numerical and experimental studies of how these factors affect the accuracy of the LHC optics measurement using the AC dipoles.

WEPC030

Measurement of Coupling Resonance Driving Terms in the LHC with AC Dipoles

2067

R. Miyamoto, R. Calaga
BNL, Upton, Long Island, New York, USA
M. Aiba
PSI, Villigen, Switzerland
R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland

Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP).
Transverse betatron coupling in the LHC is measured from Fourier analysis of turn-by-turn beam oscillations excited by AC dipoles. The use of the AC dipole for optics measurements induces a small systematic error which can be corrected with an appropriate data interpretation. An algorithm to apply this correction to the measurement of the coupling resonance driving terms is developed for the first time. This paper will review this new algorithm and present results of its application to the LHC.

WEPC032

First Measurements of Higher Order Optics Parameters in the LHC

2073

G. Vanbavinckhove
NIKHEF, Amsterdam, The Netherlands
M. Aiba
PSI, Villigen, Switzerland
R. Bartolini
Diamond, Oxfordshire, United Kingdom
R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
M. Giovannozzi, F. Schmidt, R. Tomás
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom

Higher order effects can play an important role in the performance of the LHC. Lack of knowledge of these parameters can increase the tune footprint and compromise the beam lifetime. First measurements of these parameters at injection and flattop have been conducted. Detailed simulations are compared to the measurements together with discussions on the measurement limitations.

WEPC078

Non-linear Chromaticity Studies of the LHC at Injection

2199

E.H. Maclean, M. Giovannozzi, F. Schmidt, R.J. Steinhagen, E. Todesco, R. Tomás, G. Vanbavinckhove
CERN, Geneva, Switzerland
R. Bartolini
JAI, Oxford, United Kingdom

The non-linear chromaticity of the LHC has been studied. Measurements of variation in tune with dp/p on both beams at injection optics are being compared with Q'' and Q''' as calculated with the LHC effective model. This model uses the best currently available measurements of magnetic field harmonics. An attempt is being made to optimize the b4 and b5 pool-pieces corrections in view of the corresponding chromaticity terms.

WEPC079

Beta-beating in the Effective Model of the LHC Using PTC

2202

M.C. Alabau Pons, F. Schmidt, R. Tomás
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom

An effective model of the LHC optics has been developed based on measurements of magnetic field, alignment errors and closed orbit. This model utilizes the Polymorphic Tracking Code with MAD-X as front-end to allow the inclusion of harmonics to an arbitrary order in thick lattice elements. Beta-beating calculations have been performed with this model at injection optics and at 3.5 TeV squeezed optics to 3.5 m beta-function at the interaction point. The model predictions are in remarkable agreement with the measurements performed in the 2010 LHC commissioning run.

WEPZ013

Design Status of LHeC Linac-Ring Interaction Region

2796

R. Tomás, J.L. Abelleira, S. Russenschuck, F. Zimmermann
CERN, Geneva, Switzerland
N.R. Bernard
UCLA, Los Angeles, California, USA

The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) based on the LHC, considers two options, using a ring accelerator like LEP on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an e^- beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate e^- and p beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detector-integrated combination-separation dipoles and challenging Nb3Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field “hole” to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We discuss synchrotron radiation fluxes and the chromatic correction for the lepton final focus.

THPPA01

EPS-AG Sacherer Prize: Beam Optics Developments for SPS, RHIC, LHC, CLIC and ATF2

2894

R. Tomás
CERN, Geneva, Switzerland

Highlights of linear and nonlinear optics studies are presented from various accelerators. At the LHC, optics correction is of critical importance to guarantee safe beam operation. Preparation for LHC optics measurements and corrections has been a major activity during the last decade. In particular, SPS and RHIC have served as excellent research and development machines to test new techniques and instrumentation, such as the measurement of resonance driving terms with and without AC dipoles. Together with a meticulous field quality specification, a careful installation strategy and an elaborate magnet model, these efforts have paid off in the LHC, where a record low beta-beating for hadron colliders below 10% has been achieved. Looking further into the future, the performance of the Final Focus System (FFS) is of critical importance for a future linear collider like CLIC, since it determines the IP beam spot sizes. The large chromatic aberrations required the development of novel non-linear optimization methods. Such techniques have successfully increased the CLIC design luminosity by 70% and an experimental test has been proposed for ATF2 to halve the design IP beam spot sizes.

Slides THPPA01 [1.514 MB]

MOPS068

Localization of Transverse Impedance Sources in the SPS using HEADTAIL Macroparticle Simulations

757

N. Biancacci, G. Arduini, E. Métral, D. Quatraro, G. Rumolo, B. Salvant, R. Tomás
CERN, Geneva, Switzerland
N. Biancacci, M. Migliorati, L. Palumbo
Rome University La Sapienza, Roma, Italy
R. Calaga
BNL, Upton, Long Island, New York, USA

In particle accelerators, beam coupling impedance is one of the main contributors to instability phenomena that lead to particle losses and beam quality deterioration. For this reason these machines are continuously monitored and the global and local amount of impedance needs to be evaluated. In this work we present our studies on the local transverse impedance detection algorithm. The main assumptions behind the algorithm are described in order to understand limits in reconstructing the impedance location. The phase advance response matrix is analyzed in particular for the SPS lattice, studying the different response from 90,180,270 degrees phase advance sections. The thin lenses scheme is also implemented and new analytical formulas for phase advance beating were derived. This avails us to put reconstructing lenses everywhere in the lattice, and to study their positioning scheme. Limits in linear response are analyzed. This sets the upper and lower limits in reconstruction to the phase advance measurement accuracy and the linear response regime limit.

WEPO031

The Magnetic Model of the LHC during Commissioning to Higher Beam Intensities in 2010-2011

2466

L. Deniau, N. Aquilina, L. Fiscarelli, M. Giovannozzi, P. Hagen, M. Lamont, G. Montenero, R.J. Steinhagen, M. Strzelczyk, E. Todesco, R. Tomás, W. Venturini Delsolaro, J. Wenninger
CERN, Geneva, Switzerland

The Field Description of the Large Hadron Collider (FiDeL) model is a set of semi-empirical equations linking the magnets behaviours established from magnetic measurements to the magnetic properties of the machine observed through beam measurements. The FiDeL model includes the parameterization of static components such as magnets residual magnetization, persistent currents, hysteresis and saturation as well as the decay and snap-back dynamic components. In the present paper, we outline the relationship between the beam observables (orbit, tune, chromaticity) and the model components during the commissioning to higher beam intensities in 2010-2011, with an energy of 3.5 TeV per beam. The main relevant issues are (i) the operation at 2 A/s and 10 A/s ramp rate and their influence on chromatic correction, (ii) the beta beating and its relation to the knowledge of the resistive quadrupoles transfer functions and (iii) the observed tune decay at injection energy and its possibles origins.

THPZ015

Synchrotron Radiation in the Interaction Region for a Ring-Ring and Linac-Ring LHeC

3717

N.R. Bernard
UCLA, Los Angeles, California, USA
R. Appleby, L.N.S. Thompson
UMAN, Manchester, United Kingdom
N.R. Bernard
ETH, Zurich, Switzerland
B.J. Holzer, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
M. Klein
The University of Liverpool, Liverpool, United Kingdom
P. Kostka
DESY Zeuthen, Zeuthen, Germany
B. Nagorny, U. Schneekloth
DESY, Hamburg, Germany

The Large Hadron electron Collider (LHeC) aims at bringing hadron-lepton collisions to CERN with center of mass energies in the TeV scale. The LHeC will utilize the existing LHC storage ring with the addition of a 60 GeV electron accelerator. The electron beam will be stored and accelerated in either a storage ring in the LHC tunnel (Ring-Ring) or a linac tangent to the LHC tunnel (Linac-Ring). Synchrotron Radiation (SR) in the Interaction Region (IR) of this machine requires an iterative design process in which luminosity is optimized while the SR is minimized. This process also requires attention to be given to the detector as the beam pipe must be designed such that damaging effects, such as out-gasing, are minimized while the tracking remains close to the IP. The machinery of GEANT4 has been used to simulate the SR load in the IR and also to design absorbers/masks to shield SR from backscattering into the detector or propagating with the electron beam. The outcome of these simulations, as well as cross checks, are described in the accompanying poster which characterizes the current status of the IR design for both the Ring-Ring and Linac-Ring options of the LHeC in terms of SR.

Paper	Title	Page
TUPC016	Status of the ATF2 Lattices	1027
	E. Marin, R. Tomás CERN, Geneva, Switzerland P. Bambade LAL, Orsay, France T. Okugi, T. Tauchi, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan A. Seryi JAI, Oxford, United Kingdom G.R. White, M. Woodley SLAC, Menlo Park, California, USA
	The latest status for the ATF2 Nominal and Ultra-low beta lattices designs obtained to minimize the detrimental effect of the measured multipoles are presented in this paper. A set of correction knobs for the most important aberrations at the IP have been obtained for both lattices in order to perform the tuning under realistic imperfections. Starting from the tuned ATF2 Nominal lattice a squeeze sequence reducing beta_y is performed to reach the ultra-low beta lattice. Tuning results are shown for both options.

TUPZ001	90 m Optics Commissioning	1795
	S. Cavalier LAL, Orsay, France H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger CERN, Geneva, Switzerland
	Special β* = 90 m optics have been developed for the two very high luminosity insertions of the LHC, as a first step towards to allow for very low angle precision measurements of the proton-proton collisions in the LHC. These optics were developed to be compatible with the standard LHC injection and ramp optics. The target value of β* = 90 m is reached by an un-squeeze from the injection β* = 11 m. We describe the implementation of this optics in the LHC and the first experience in the commissioning of these optics.

TUPZ006	Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan	1810
	R.W. Assmann, R. Bruce, M. Giovannozzi, G.J. Müller, S. Redaelli, F. Schmidt, R. Tomás, J. Wenninger, D. Wollmann CERN, Geneva, Switzerland M. Alabau IFIC, Valencia, Spain
	A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in σs of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.

TUPZ009	LHC Machine Protection against Very Fast Crab Cavity Failures	1816
	T. Baer, R. Tomás, J. Tückmantel, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland T. Baer Uni HH, Hamburg, Germany R. Calaga BNL, Upton, Long Island, New York, USA
	For the high-luminosity LHC upgrade program (HL-LHC), the installation of crab cavities (CCs) is essential to compensate the geometric luminosity loss due to the crossing angle. The baseline is a local scheme with CCs around the ATLAS and CMS experiments. In a failure case (e.g. a CC quench), the voltage and/or phase of a CC can change significantly with a fast time constant of the order of a LHC turn. This can lead to large, global betatron oscillations of the beam. Against the background of machine protection, the influence of a CC failure on the beam dynamics is discussed. The results from dedicated tracking studies, including the LHC upgrade optics, are presented. Necessary countermeasures to limit the impact of CC failures to an acceptable level are proposed.

TUPZ026	Alternative Working Point(s) at Injection for the LHC	1861
	R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP). At present, the LHC operates with a different fractional tunes at injection and at collision energy due to improved dynamic aperture indicated by tracking studies. Therefore, a tune swing crossing the 10th order resonance is needed during the beta-squeeze. A new proposal to alter the working point to collision tunes already at injection and during an energy ramp is foreseen to avoid the tune jump. Simulations and measurements of the optics along with the beam emittances and lifetime are compared to the nominal injection tunes. Feasibility for a working point close to the 1/2 integer is also attempted.

TUPZ027	Beta* Measurement in the LHC Based on K-modulation	1864
	R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP). Accurate knowledge of the collision point optics is crucial to equalize the luminosities at the different experiments. K-modulation was successfully applied at several accelerators for measuring the lattice beta functions. In the LHC, it was proposed as an alternative method to compute the beta* at the collision points. Results of beta* measurements in the LHC based on the K-modulation technique are presented with comparisons to nominal segment-by-segment method.

TUPZ034	Impact of Arc Phase Advance on Chromatic Optics in RHIC	1885
	R. Calaga, R. Miyamoto, G. Robert-Demolaize, S.M. White BNL, Upton, Long Island, New York, USA R. De Maria, R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: This work is partially supported by the US Department of Energy through the LHC Accelerator Research program (LARP). The phase advance between the two interaction points in RHIC is optimized for dynamic aperture for a initial design beta-star. This may not hold true as RHIC presently operates with a considerably reduced beta-star. Additionally the reduction of the available beam aperture due to an enlarged chromatic beta-beating is evident. Results from phase advance scans between the two IPs to reduce the chromatic beta-beating in model and measurements are presented. Impact on the single beam lifetime and momentum aperture is compared to the nominal optics.

WEPC004	Comparison of the Action and Phase Analysis on LHC Orbits with Other Techniques	2004
	J.F. Cardona UNAL, Bogota D.C, Colombia R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands
	Funding: DIB-Universidad Nacional de Colombia Recently acquired turn-by-turn data of the LHC is analyzed using the action and phase jump technique. The results of this analysis show a visible variation of the action and phase plots at the interaction regions from which optic error estimations can be done. In this paper error estimations will be presented and comparisons with other existing techniques in the LHC, such as the recently implemented Segment-by-segment technique, will be discussed.

WEPC028	Record Low Beta-beat of 10% in the LHC	2061
	G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands M. Aiba PSI, Villigen, Switzerland R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA R. Tomás CERN, Geneva, Switzerland
	During the 2011 LHC run several measurements and correction campaigns were conducted. As a result a peak beta-beat of 10% level was achieved. This level, well below the specified tolerances of the LHC, improves the aperture margins and helps minimize the luminosity imbalance between the different experiments. A combination of local corrections at the insertion regions and an overall global correction were used to achieve this record low beta-beat. The sequence of the optics corrections and stability along the 2011 run are reported.

WEPC029	Accuracy of the LHC Optics Measurement based on AC Dipoles	2064
	R. Miyamoto, R. Calaga BNL, Upton, Long Island, New York, USA R. Tomás, G. Vanbavinckhove CERN, Geneva, Switzerland
	Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). The tight tolerances in the LHC requires optics measurement with very good accuracy. Therefore, AC dipoles are employed as the primary devices to measure the LHC optics. The accuracy of the measurement is mainly determined by the length of the coherent signal, signal-to-noise ratio of the measurement, and the data processing to effectively suppress the noise. This paper presents numerical and experimental studies of how these factors affect the accuracy of the LHC optics measurement using the AC dipoles.

WEPC030	Measurement of Coupling Resonance Driving Terms in the LHC with AC Dipoles	2067
	R. Miyamoto, R. Calaga BNL, Upton, Long Island, New York, USA M. Aiba PSI, Villigen, Switzerland R. Tomás, G. Vanbavinckhove CERN, Geneva, Switzerland
	Funding: This work partially supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). Transverse betatron coupling in the LHC is measured from Fourier analysis of turn-by-turn beam oscillations excited by AC dipoles. The use of the AC dipole for optics measurements induces a small systematic error which can be corrected with an appropriate data interpretation. An algorithm to apply this correction to the measurement of the coupling resonance driving terms is developed for the first time. This paper will review this new algorithm and present results of its application to the LHC.

WEPC032	First Measurements of Higher Order Optics Parameters in the LHC	2073
	G. Vanbavinckhove NIKHEF, Amsterdam, The Netherlands M. Aiba PSI, Villigen, Switzerland R. Bartolini Diamond, Oxfordshire, United Kingdom R. Calaga, R. Miyamoto BNL, Upton, Long Island, New York, USA M. Giovannozzi, F. Schmidt, R. Tomás CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom
	Higher order effects can play an important role in the performance of the LHC. Lack of knowledge of these parameters can increase the tune footprint and compromise the beam lifetime. First measurements of these parameters at injection and flattop have been conducted. Detailed simulations are compared to the measurements together with discussions on the measurement limitations.

WEPC078	Non-linear Chromaticity Studies of the LHC at Injection	2199
	E.H. Maclean, M. Giovannozzi, F. Schmidt, R.J. Steinhagen, E. Todesco, R. Tomás, G. Vanbavinckhove CERN, Geneva, Switzerland R. Bartolini JAI, Oxford, United Kingdom
	The non-linear chromaticity of the LHC has been studied. Measurements of variation in tune with dp/p on both beams at injection optics are being compared with Q'' and Q''' as calculated with the LHC effective model. This model uses the best currently available measurements of magnetic field harmonics. An attempt is being made to optimize the b4 and b5 pool-pieces corrections in view of the corresponding chromaticity terms.

WEPC079	Beta-beating in the Effective Model of the LHC Using PTC	2202
	M.C. Alabau Pons, F. Schmidt, R. Tomás CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom
	An effective model of the LHC optics has been developed based on measurements of magnetic field, alignment errors and closed orbit. This model utilizes the Polymorphic Tracking Code with MAD-X as front-end to allow the inclusion of harmonics to an arbitrary order in thick lattice elements. Beta-beating calculations have been performed with this model at injection optics and at 3.5 TeV squeezed optics to 3.5 m beta-function at the interaction point. The model predictions are in remarkable agreement with the measurements performed in the 2010 LHC commissioning run.

WEPZ013	Design Status of LHeC Linac-Ring Interaction Region	2796
	R. Tomás, J.L. Abelleira, S. Russenschuck, F. Zimmermann CERN, Geneva, Switzerland N.R. Bernard UCLA, Los Angeles, California, USA
	The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) based on the LHC, considers two options, using a ring accelerator like LEP on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an e^- beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate e^- and p beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detector-integrated combination-separation dipoles and challenging Nb3Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field “hole” to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We discuss synchrotron radiation fluxes and the chromatic correction for the lepton final focus.

THPPA01	EPS-AG Sacherer Prize: Beam Optics Developments for SPS, RHIC, LHC, CLIC and ATF2	2894
	R. Tomás CERN, Geneva, Switzerland
	Highlights of linear and nonlinear optics studies are presented from various accelerators. At the LHC, optics correction is of critical importance to guarantee safe beam operation. Preparation for LHC optics measurements and corrections has been a major activity during the last decade. In particular, SPS and RHIC have served as excellent research and development machines to test new techniques and instrumentation, such as the measurement of resonance driving terms with and without AC dipoles. Together with a meticulous field quality specification, a careful installation strategy and an elaborate magnet model, these efforts have paid off in the LHC, where a record low beta-beating for hadron colliders below 10% has been achieved. Looking further into the future, the performance of the Final Focus System (FFS) is of critical importance for a future linear collider like CLIC, since it determines the IP beam spot sizes. The large chromatic aberrations required the development of novel non-linear optimization methods. Such techniques have successfully increased the CLIC design luminosity by 70% and an experimental test has been proposed for ATF2 to halve the design IP beam spot sizes.
	Slides THPPA01 [1.514 MB]

MOPS068	Localization of Transverse Impedance Sources in the SPS using HEADTAIL Macroparticle Simulations	757
	N. Biancacci, G. Arduini, E. Métral, D. Quatraro, G. Rumolo, B. Salvant, R. Tomás CERN, Geneva, Switzerland N. Biancacci, M. Migliorati, L. Palumbo Rome University La Sapienza, Roma, Italy R. Calaga BNL, Upton, Long Island, New York, USA
	In particle accelerators, beam coupling impedance is one of the main contributors to instability phenomena that lead to particle losses and beam quality deterioration. For this reason these machines are continuously monitored and the global and local amount of impedance needs to be evaluated. In this work we present our studies on the local transverse impedance detection algorithm. The main assumptions behind the algorithm are described in order to understand limits in reconstructing the impedance location. The phase advance response matrix is analyzed in particular for the SPS lattice, studying the different response from 90,180,270 degrees phase advance sections. The thin lenses scheme is also implemented and new analytical formulas for phase advance beating were derived. This avails us to put reconstructing lenses everywhere in the lattice, and to study their positioning scheme. Limits in linear response are analyzed. This sets the upper and lower limits in reconstruction to the phase advance measurement accuracy and the linear response regime limit.

WEPO031	The Magnetic Model of the LHC during Commissioning to Higher Beam Intensities in 2010-2011	2466
	L. Deniau, N. Aquilina, L. Fiscarelli, M. Giovannozzi, P. Hagen, M. Lamont, G. Montenero, R.J. Steinhagen, M. Strzelczyk, E. Todesco, R. Tomás, W. Venturini Delsolaro, J. Wenninger CERN, Geneva, Switzerland
	The Field Description of the Large Hadron Collider (FiDeL) model is a set of semi-empirical equations linking the magnets behaviours established from magnetic measurements to the magnetic properties of the machine observed through beam measurements. The FiDeL model includes the parameterization of static components such as magnets residual magnetization, persistent currents, hysteresis and saturation as well as the decay and snap-back dynamic components. In the present paper, we outline the relationship between the beam observables (orbit, tune, chromaticity) and the model components during the commissioning to higher beam intensities in 2010-2011, with an energy of 3.5 TeV per beam. The main relevant issues are (i) the operation at 2 A/s and 10 A/s ramp rate and their influence on chromatic correction, (ii) the beta beating and its relation to the knowledge of the resistive quadrupoles transfer functions and (iii) the observed tune decay at injection energy and its possibles origins.

THPZ015	Synchrotron Radiation in the Interaction Region for a Ring-Ring and Linac-Ring LHeC	3717
	N.R. Bernard UCLA, Los Angeles, California, USA R. Appleby, L.N.S. Thompson UMAN, Manchester, United Kingdom N.R. Bernard ETH, Zurich, Switzerland B.J. Holzer, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland M. Klein The University of Liverpool, Liverpool, United Kingdom P. Kostka DESY Zeuthen, Zeuthen, Germany B. Nagorny, U. Schneekloth DESY, Hamburg, Germany
	The Large Hadron electron Collider (LHeC) aims at bringing hadron-lepton collisions to CERN with center of mass energies in the TeV scale. The LHeC will utilize the existing LHC storage ring with the addition of a 60 GeV electron accelerator. The electron beam will be stored and accelerated in either a storage ring in the LHC tunnel (Ring-Ring) or a linac tangent to the LHC tunnel (Linac-Ring). Synchrotron Radiation (SR) in the Interaction Region (IR) of this machine requires an iterative design process in which luminosity is optimized while the SR is minimized. This process also requires attention to be given to the detector as the beam pipe must be designed such that damaging effects, such as out-gasing, are minimized while the tracking remains close to the IP. The machinery of GEANT4 has been used to simulate the SR load in the IR and also to design absorbers/masks to shield SR from backscattering into the detector or propagating with the electron beam. The outcome of these simulations, as well as cross checks, are described in the accompanying poster which characterizes the current status of the IR design for both the Ring-Ring and Linac-Ring options of the LHeC in terms of SR.