IPAC2015 - List of Authors (Tomas, R.)

Paper	Title	Page
MOBC1	Towards Ultra-Low β^* in ATF2	38
	M. Patecki, A.V. Aloev, D.R. Bett, M. Modena, R. Tomás CERN, Geneva, Switzerland K. Kubo, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan E. Marín, G.R. White SLAC, Menlo Park, California, USA
	The Accelerator Test Facility 2 (ATF2) has already demonstrated the feasibility of Final Focus Systems based on the local chromaticity correction scheme and its focusing capabilities by reaching a vertical beam size at the virtual Interaction Point (IP) of less than 50 nm. The value of the chromaticity in ATF2 is comparable with the expected chromaticity in ILC, but 4 times lower than in a design of CLIC. ATF2 gives the unique possibility to test operation at CLIC chromaticity values by reducing the vertical beta function at the IP by a factor of 4 (the inverse proportionality of chromaticity with beta function value at IP is assumed). The experience collected in this way would be beneficial for both ILC and CLIC projects. Simulations show that the multipolar errors and Final Doublet fringe fields spoil the IP beam sizes at ATF2. Either increasing a value of the horizontal beta function or installing a pair of octupole magnets mitigate the impact of these aberrations. This paper summarizes the studies towards the realization of the ultra-low β^* optics in ATF2 and reports on the progress of the construction of the octupoles.
	Slides MOBC1 [1.566 MB]
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MOPWA059	Dynamic Aperture Studies for the FCC-ee	258
	L.E. Medina Medrano DCI-UG, León, Mexico R. Martin, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland R. Martin Humboldt University Berlin, Berlin, Germany
	Funding: Work supported by the Beam Project (CONACYT, Mexico). Dynamic aperture (DA) studies have been conducted on the latest Future Circular Collider - ee (FCC-ee) lattices as a function of momentum deviation. Two different schemes for the interaction region are used, which are connected to the main arcs: the crab waist approach, developed by BINP, and an update to the CERN design where the use of crab cavities is envisioned. The results presented show an improvement in the performance of both designs.
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MOPJE052	Observations of an Anomalous Octupolar Resonance in the LHC	412
	F.S. Carlier, J.M. Coello de Portugal, A. Langner, E.H. Maclean, T. Persson, R. Tomás, R. Westenberger CERN, Geneva, Switzerland
	While linear LHC dynamics is mostly understood and under control, non-linear beam dynamics will play an increasingly important role in the challenging regimes of future LHC operation. In 2012, turn-by-turn measurements of large betatron excitations of LHC Beam 2 at injection energy were carried out. These measurements revealed an unexpectedly large spectral line in the horizontal motion with frequency Qx+2Qy. Detailed analyses and simulations are presented to unveil the nature of this spectral line.
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MOPJE054	Developments of the Segment-by-Segment Technique for Optics Corrections in the LHC	419
	A. Langner, J.M. Coello de Portugal, P.K. Skowroński, R. Tomás CERN, Geneva, Switzerland
	Optics correction algorithms will become even more critical for the operation of the LHC at 6.5 TeV. For the computation of local corrections the segment-by-segment technique is used. We present improvements to this technique and an advanced error analysis, which increase the sensitivity for finding local corrections. Furthermore, we will investigate limitations of this method for lower beta-star optics as they will be used in the high-luminosity LHC (HL-LHC) upgrade.
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MOPJE056	OMC Software Improvements in 2014	426
	J.M. Coello de Portugal, F.S. Carlier, A. Langner, T. Persson, P.K. Skowroński, R. Tomás CERN, Geneva, Switzerland
	We present the LHC Optics Measurement and Corrections (OMC) software developments done during 2014 on stability, performance and usability. This software is used to analyze turn-by-turn data and compute optics corrections to get the best performance of the LHC. The main developments have been an automatic local correction script to get faster and more accurate corrections in the interaction regions, a self contained test for the whole software package to avoid mistakes during the software development and the improvements in the software quality and efficiency of the Segment by Segment technique script. We also present a study of the code quality in its current status.
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MOPJE057	Optics Measurement using the N-BPM Method for the ALBA Synchrotron	430
	A. Langner, J.M. Coello de Portugal, R. Tomás CERN, Geneva, Switzerland G. Benedetti, M. Carlà, U. Iriso, Z. Martí ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	The N-BPM method recently developed for the LHC has significantly improved the precision of optics measurements which are based on beam position monitor (BPM) turn-by-turn data. The main improvement is owed to the consideration of correlations for statistical and systematic error sources, as well as increasing the amount of BPM combinations for one measurement. We present how this technique can be applied at light sources like ALBA, and compare the results with other methods.
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MOPJE063	Orbit Correction in the CERN PS Booster	449
	M. McAteer, E. Benedetto, C. Carli, G.P. Di Giovanni, B. Mikulec, R. Tomás CERN, Geneva, Switzerland
	Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no (PITN-GA-2011-289485-OPAC). Prior to the Long Shutdown of 2013-2014 (LS1), control of the closed orbit in the four rings of the CERN PS Booster (PSB) was achieved by adjusting the alignment of several focusing quadrupoles. After a set of orbit corrector dipoles was installed, a major realignment campaign was undertaken to remove these intentional quadrupole offsets and any other magnet misalignments. This paper summarizes the effects of the magnet realignment on the closed orbit in the PSB and the results of closed orbit correction with corrector dipoles.
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MOPJE065	Contribution of Optical Aberrations to Spot-size Increase with Bunch Intensity at ATF2	455
	M. Patecki, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan M. Patecki Warsaw University of Technology, Warsaw, Poland G.R. White SLAC, Menlo Park, California, USA
	A primary goal of ATF2 (Accelerator Test Facility) is to demonstrate a low vertical beam size at the interaction point (IP) of about 37 nm. Measurements over the past years indicate that the ATF2 vertical beam size strongly rises with bunch intensity. Several different origins of this increase are considered, e.g. wakefields occurring between the ATF damping ring and the IP, and/or intrabeam scattering (IBS) causing the increase of transverse emittances and energy spread in the damping ring with the increase of the bunch intensity. In this paper we address the second possibility. Past measurements and simulations of the IBS effects in the ATF are used to model the intensity-dependent initial emittances and energy spread at the entrance of the final focus. Particle tracking simulations predict the IP vertical beam size growth expected from the known optical aberrations for initial beam parameters corresponding to varying bunch intensities. Comparing simulation results with emittance measurements at different locations allows us to draw some conclusions about the impact of IBS in the damping ring on the IP spot size, and about possible single-bunch wakefields in the ATF2.
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MOPJE079	Tracking Studies in the LHeC Lattice	502
	E. Cruz Alaniz, D. Newton The University of Liverpool, Liverpool, United Kingdom E. Cruz Alaniz, D. Newton Cockcroft Institute, Warrington, Cheshire, United Kingdom R. Tomás CERN, Geneva, Switzerland
	Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485 The Large Hadron Electron Collider (LHeC) is a proposed upgrade of the LHC to provide electron-proton collisions and explore a new regime of energy and luminosity for nucleon-lepton scattering. A nominal design has previously been presented, featuring a lattice and optical configuration to focus one of the proton beams of the LHC (reaching a value of β^=10 cm) and to collide it head-on with an electron beam to produce collisions with the desired luminosity of L=10³³ cm^-2 s^-1. The proton beam optics is achieved with the aid of a new inner triplet of quadrupoles at L=10 m from the interaction point and the extension of the Achromatic Telescopic Squeezing (ATS) Scheme used for the High Luminosity-LHC project. The flexibility of this design has been studied in terms of minimising β^* and increasing L*. In this work, particle tracking is performed in a thin lens approximation of the LHeC proton lattice to compute the dynamic aperture and perform frequency map analysis for different types of chromatic correction schemes, in order to find the one who will provide the most beam stability and to study the effects of non linearities.
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MOPHA004	Oide Limit Mitigation Studies	781
	O.R. Blanco-García, P. Bambade LAL, Orsay, France R. Tomás CERN, Geneva, Switzerland
	Particle radiation when traversing a focusing quadrupole limits the minimum achievable beam size, known as the Oide limit. This effect may be compensated by a pair of multipoles which reduce the impact of the energy loss in the vertical beam size. Simulations in PLACET using the CLIC 3 TeV QD0 and L⃰ show a reduction of (4.3 ± 0.2)% in the vertical beam size.
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TUPTY001	Interaction Region for a 100 TeV Proton-Proton Collider	1996
	R. Martin, R. Tomás CERN, Geneva, Switzerland B. Dalena CEA/IRFU, Gif-sur-Yvette, France
	As part of its post-LHC high energy physics program, CERN is conducting a study for a new proton-proton collider, FCC-hh, running at center-of-mass energies of up to 100 TeV, pushing the energy frontier of fundamental physics to a new limit. At a circumference of 80-100 km, this machine is planned to use the same tunnel as FCC-ee, a proposed 90-350 GeV high luminosity electron-positron collider. This paper presents the design progress and technical challenges for the interaction region of FCC-hh.
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TUPTY032	Study of Muon Backgrounds in the CLIC Beam Delivery System	2075
	F.B. Pilicer, E. Pilicer, İ. Tapan UU, Bursa, Turkey H. Burkhardt, L. Gatignon, A. Latina, D. Schulte, R. Tomás CERN, Geneva, Switzerland
	We describe the detailed modelling of muon background generation and absorption in the CLIC beam delivery system. The majority of the background muons originates in the first stages of halo collimation. We also discuss options to use magnetised cylindrical iron shields to reduce the muon background flux reaching the detector region.
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TUPTY040	Comparison of Beam Sizes at the Collimator Locations from Measured Optics and Beam-based Collimator Alignment at the LHC	2101
	G. Valentino, R. Bruce, A. Langner, S. Redaelli, R. Tomás CERN, Geneva, Switzerland
	At the LHC, the collimation hierarchy is defined in units of the betatron beam size using the sizes at each collimator location. The beam size at a given collimator can be inferred from the gap measurement during beam-based alignment campaigns, when the collimator touches a reference beam halo defined with the primary collimators. On the other hand, the beta functions at each collimator are also measured as a part of the standard LHC optics validation. This paper presents a comparison of the beam size measurements at the collimator locations applying these two techniques for different machine configurations. This work aims at determining which is the most reliable method for setting the collimator gaps at the LHC.
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TUPTY042	Non-linear Coupling Studies in the LHC	2105
	T. Persson, Y.I. Levinsen, E.H. Maclean, R. Tomás CERN, Geneva, Switzerland E.H. Maclean JAI, Oxford, United Kingdom
	The amplitude detuning has been observed to decrease significantly as the horizontal and vertical tunes are approaching each other. This effect is potentially harmful since it might cause a loss of Landau damping, hence giving rise to instabilities. The measured tune split (Qx-Qy) versus amplitude is several times bigger than what can be explained with linear coupling. In this paper we present studies performed to identify the dominant sources of the non-linear coupling observed in the LHC.
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TUPTY043	Analysis of Intensity-dependent Effects on LHC Transverse Tunes at Injection Energy	2108
	R. De Maria, M. Giovannozzi, T. Persson, R. Tomás CERN, Geneva, Switzerland Y. Wei IHEP, Beijing, People's Republic of China
	The LHC Run I has provided a huge amount of data that can be used to deepen the understanding of the beam behaviour. In this paper the focus is on the analysis of transverse tunes at injection energy to detect signs of intensity-dependent effects. BPM data, recording the injection oscillations of the operational beams during the ring-filling phase, have been analysed in detail to enable extracting useful information about the tune shift vs. injected beam intensity. The data processing and the results are discussed in detail, including also possible implications for future operation.
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TUPTY060	The FCC-ee Study: Progress and Challenges	2165
	M. Koratzinos DPNC, Genève, Switzerland S. Aumon, C. Cook, A. Doblhammer, B. Härer, B.J. Holzer, R. Tomás, F. Zimmermann CERN, Geneva, Switzerland A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov BINP SB RAS, Novosibirsk, Russia M. Boscolo INFN/LNF, Frascati (Roma), Italy L.E. Medina Medrano UGTO, Leon, Mexico U. Wienands SLAC, Menlo Park, California, USA
	The FCC (future circular collider) study represents a vision for the next large project in high energy physics, comprising a 80-100 km tunnel that can house a future 100TeV hadron collider. The study also includes a high luminosity e⁺e⁻ collider operating in the centre-of-mass energy range of 90-350 GeV as a possible intermediate step, the FCC-ee. The FCC-ee aims at definitive electro-weak precision measurements of the Z, W, H and top particles, and search for rare phenomena. Although FCC-ee is based on known technology, the goal performance in luminosity and energy calibration make it quite challenging. During 2014 the study went through an exploration phase and during the next three years a conceptual design report will be prepared.
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TUPTY061	Combined Operation and Staging Scenarios for the FCC-ee Lepton Collider	2169
	M. Benedikt, B.J. Holzer, E. Jensen, R. Tomás, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov BINP SB RAS, Novosibirsk, Russia K. Ohmi, K. Oide KEK, Ibaraki, Japan U. Wienands SLAC, Menlo Park, California, USA
	FCC-ee is a proposed high-energy electron positron circular collider that would initially occupy the 100-km FCC tunnel that will eventually house the 100 TeV FCC-hh hadron collider. The parameter range for the e⁺/e⁻ collider is large, operating at a cm energy from 90 GeV (Z-pole) to 350 GeV (t-tbar production) with the maximum beam current ranging from 1.5 A to 6 mA for each beam, corresponding to a synchrotron radiation power of 50 MW and a radiative energy loss varying from ~30 MeV/turn to ~7500 MeV/turn. This presents challenges for the rf system due to the varying rf voltage requirements and beam loading conditions. In this paper we present a possible gradual evolution of the FCC-ee complex by step-wise expansion, and possibly reconfiguration, of the superconducting RF system. The performance attainable at each step is discussed, along with the possible advantages and drawbacks.
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Paper

Title

Page

Towards Ultra-Low β^* in ATF2

38

M. Patecki, A.V. Aloev, D.R. Bett, M. Modena, R. Tomás
CERN, Geneva, Switzerland
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
E. Marín, G.R. White
SLAC, Menlo Park, California, USA

The Accelerator Test Facility 2 (ATF2) has already demonstrated the feasibility of Final Focus Systems based on the local chromaticity correction scheme and its focusing capabilities by reaching a vertical beam size at the virtual Interaction Point (IP) of less than 50 nm. The value of the chromaticity in ATF2 is comparable with the expected chromaticity in ILC, but 4 times lower than in a design of CLIC. ATF2 gives the unique possibility to test operation at CLIC chromaticity values by reducing the vertical beta function at the IP by a factor of 4 (the inverse proportionality of chromaticity with beta function value at IP is assumed). The experience collected in this way would be beneficial for both ILC and CLIC projects. Simulations show that the multipolar errors and Final Doublet fringe fields spoil the IP beam sizes at ATF2. Either increasing a value of the horizontal beta function or installing a pair of octupole magnets mitigate the impact of these aberrations. This paper summarizes the studies towards the realization of the ultra-low β^* optics in ATF2 and reports on the progress of the construction of the octupoles.

Slides MOBC1 [1.566 MB]

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MOPWA059

Dynamic Aperture Studies for the FCC-ee

258

L.E. Medina Medrano
DCI-UG, León, Mexico
R. Martin, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
R. Martin
Humboldt University Berlin, Berlin, Germany

Funding: Work supported by the Beam Project (CONACYT, Mexico).
Dynamic aperture (DA) studies have been conducted on the latest Future Circular Collider - ee (FCC-ee) lattices as a function of momentum deviation. Two different schemes for the interaction region are used, which are connected to the main arcs: the crab waist approach, developed by BINP, and an update to the CERN design where the use of crab cavities is envisioned. The results presented show an improvement in the performance of both designs.

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MOPJE052

Observations of an Anomalous Octupolar Resonance in the LHC

412

F.S. Carlier, J.M. Coello de Portugal, A. Langner, E.H. Maclean, T. Persson, R. Tomás, R. Westenberger
CERN, Geneva, Switzerland

While linear LHC dynamics is mostly understood and under control, non-linear beam dynamics will play an increasingly important role in the challenging regimes of future LHC operation. In 2012, turn-by-turn measurements of large betatron excitations of LHC Beam 2 at injection energy were carried out. These measurements revealed an unexpectedly large spectral line in the horizontal motion with frequency Qx+2Qy. Detailed analyses and simulations are presented to unveil the nature of this spectral line.

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MOPJE054

Developments of the Segment-by-Segment Technique for Optics Corrections in the LHC

419

A. Langner, J.M. Coello de Portugal, P.K. Skowroński, R. Tomás
CERN, Geneva, Switzerland

Optics correction algorithms will become even more critical for the operation of the LHC at 6.5 TeV. For the computation of local corrections the segment-by-segment technique is used. We present improvements to this technique and an advanced error analysis, which increase the sensitivity for finding local corrections. Furthermore, we will investigate limitations of this method for lower beta-star optics as they will be used in the high-luminosity LHC (HL-LHC) upgrade.

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MOPJE056

OMC Software Improvements in 2014

426

J.M. Coello de Portugal, F.S. Carlier, A. Langner, T. Persson, P.K. Skowroński, R. Tomás
CERN, Geneva, Switzerland

We present the LHC Optics Measurement and Corrections (OMC) software developments done during 2014 on stability, performance and usability. This software is used to analyze turn-by-turn data and compute optics corrections to get the best performance of the LHC. The main developments have been an automatic local correction script to get faster and more accurate corrections in the interaction regions, a self contained test for the whole software package to avoid mistakes during the software development and the improvements in the software quality and efficiency of the Segment by Segment technique script. We also present a study of the code quality in its current status.

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MOPJE057

Optics Measurement using the N-BPM Method for the ALBA Synchrotron

430

A. Langner, J.M. Coello de Portugal, R. Tomás
CERN, Geneva, Switzerland
G. Benedetti, M. Carlà, U. Iriso, Z. Martí
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

The N-BPM method recently developed for the LHC has significantly improved the precision of optics measurements which are based on beam position monitor (BPM) turn-by-turn data. The main improvement is owed to the consideration of correlations for statistical and systematic error sources, as well as increasing the amount of BPM combinations for one measurement. We present how this technique can be applied at light sources like ALBA, and compare the results with other methods.

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MOPJE063

Orbit Correction in the CERN PS Booster

449

M. McAteer, E. Benedetto, C. Carli, G.P. Di Giovanni, B. Mikulec, R. Tomás
CERN, Geneva, Switzerland

Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no (PITN-GA-2011-289485-OPAC).
Prior to the Long Shutdown of 2013-2014 (LS1), control of the closed orbit in the four rings of the CERN PS Booster (PSB) was achieved by adjusting the alignment of several focusing quadrupoles. After a set of orbit corrector dipoles was installed, a major realignment campaign was undertaken to remove these intentional quadrupole offsets and any other magnet misalignments. This paper summarizes the effects of the magnet realignment on the closed orbit in the PSB and the results of closed orbit correction with corrector dipoles.

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MOPJE065

Contribution of Optical Aberrations to Spot-size Increase with Bunch Intensity at ATF2

455

M. Patecki, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
M. Patecki
Warsaw University of Technology, Warsaw, Poland
G.R. White
SLAC, Menlo Park, California, USA

A primary goal of ATF2 (Accelerator Test Facility) is to demonstrate a low vertical beam size at the interaction point (IP) of about 37 nm. Measurements over the past years indicate that the ATF2 vertical beam size strongly rises with bunch intensity. Several different origins of this increase are considered, e.g. wakefields occurring between the ATF damping ring and the IP, and/or intrabeam scattering (IBS) causing the increase of transverse emittances and energy spread in the damping ring with the increase of the bunch intensity. In this paper we address the second possibility. Past measurements and simulations of the IBS effects in the ATF are used to model the intensity-dependent initial emittances and energy spread at the entrance of the final focus. Particle tracking simulations predict the IP vertical beam size growth expected from the known optical aberrations for initial beam parameters corresponding to varying bunch intensities. Comparing simulation results with emittance measurements at different locations allows us to draw some conclusions about the impact of IBS in the damping ring on the IP spot size, and about possible single-bunch wakefields in the ATF2.

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MOPJE079

Tracking Studies in the LHeC Lattice

502

E. Cruz Alaniz, D. Newton
The University of Liverpool, Liverpool, United Kingdom
E. Cruz Alaniz, D. Newton
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R. Tomás
CERN, Geneva, Switzerland

Funding: This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485
The Large Hadron Electron Collider (LHeC) is a proposed upgrade of the LHC to provide electron-proton collisions and explore a new regime of energy and luminosity for nucleon-lepton scattering. A nominal design has previously been presented, featuring a lattice and optical configuration to focus one of the proton beams of the LHC (reaching a value of β^*=10 cm) and to collide it head-on with an electron beam to produce collisions with the desired luminosity of L=10³³ cm^-2 s^-1. The proton beam optics is achieved with the aid of a new inner triplet of quadrupoles at L*=10 m from the interaction point and the extension of the Achromatic Telescopic Squeezing (ATS) Scheme used for the High Luminosity-LHC project. The flexibility of this design has been studied in terms of minimising β^* and increasing L*. In this work, particle tracking is performed in a thin lens approximation of the LHeC proton lattice to compute the dynamic aperture and perform frequency map analysis for different types of chromatic correction schemes, in order to find the one who will provide the most beam stability and to study the effects of non linearities.

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MOPHA004

Oide Limit Mitigation Studies

781

O.R. Blanco-García, P. Bambade
LAL, Orsay, France
R. Tomás
CERN, Geneva, Switzerland

Particle radiation when traversing a focusing quadrupole limits the minimum achievable beam size, known as the Oide limit. This effect may be compensated by a pair of multipoles which reduce the impact of the energy loss in the vertical beam size. Simulations in PLACET using the CLIC 3 TeV QD0 and L⃰ show a reduction of (4.3 ± 0.2)% in the vertical beam size.

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TUPTY001

Interaction Region for a 100 TeV Proton-Proton Collider

1996

R. Martin, R. Tomás
CERN, Geneva, Switzerland
B. Dalena
CEA/IRFU, Gif-sur-Yvette, France

As part of its post-LHC high energy physics program, CERN is conducting a study for a new proton-proton collider, FCC-hh, running at center-of-mass energies of up to 100 TeV, pushing the energy frontier of fundamental physics to a new limit. At a circumference of 80-100 km, this machine is planned to use the same tunnel as FCC-ee, a proposed 90-350 GeV high luminosity electron-positron collider. This paper presents the design progress and technical challenges for the interaction region of FCC-hh.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY001

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TUPTY032

Study of Muon Backgrounds in the CLIC Beam Delivery System

2075

F.B. Pilicer, E. Pilicer, İ. Tapan
UU, Bursa, Turkey
H. Burkhardt, L. Gatignon, A. Latina, D. Schulte, R. Tomás
CERN, Geneva, Switzerland

We describe the detailed modelling of muon background generation and absorption in the CLIC beam delivery system. The majority of the background muons originates in the first stages of halo collimation. We also discuss options to use magnetised cylindrical iron shields to reduce the muon background flux reaching the detector region.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY032

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TUPTY040

Comparison of Beam Sizes at the Collimator Locations from Measured Optics and Beam-based Collimator Alignment at the LHC

2101

G. Valentino, R. Bruce, A. Langner, S. Redaelli, R. Tomás
CERN, Geneva, Switzerland

At the LHC, the collimation hierarchy is defined in units of the betatron beam size using the sizes at each collimator location. The beam size at a given collimator can be inferred from the gap measurement during beam-based alignment campaigns, when the collimator touches a reference beam halo defined with the primary collimators. On the other hand, the beta functions at each collimator are also measured as a part of the standard LHC optics validation. This paper presents a comparison of the beam size measurements at the collimator locations applying these two techniques for different machine configurations. This work aims at determining which is the most reliable method for setting the collimator gaps at the LHC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY040

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TUPTY042

Non-linear Coupling Studies in the LHC

2105

T. Persson, Y.I. Levinsen, E.H. Maclean, R. Tomás
CERN, Geneva, Switzerland
E.H. Maclean
JAI, Oxford, United Kingdom

The amplitude detuning has been observed to decrease significantly as the horizontal and vertical tunes are approaching each other. This effect is potentially harmful since it might cause a loss of Landau damping, hence giving rise to instabilities. The measured tune split (Qx-Qy) versus amplitude is several times bigger than what can be explained with linear coupling. In this paper we present studies performed to identify the dominant sources of the non-linear coupling observed in the LHC.

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TUPTY043

Analysis of Intensity-dependent Effects on LHC Transverse Tunes at Injection Energy

2108

R. De Maria, M. Giovannozzi, T. Persson, R. Tomás
CERN, Geneva, Switzerland
Y. Wei
IHEP, Beijing, People's Republic of China

The LHC Run I has provided a huge amount of data that can be used to deepen the understanding of the beam behaviour. In this paper the focus is on the analysis of transverse tunes at injection energy to detect signs of intensity-dependent effects. BPM data, recording the injection oscillations of the operational beams during the ring-filling phase, have been analysed in detail to enable extracting useful information about the tune shift vs. injected beam intensity. The data processing and the results are discussed in detail, including also possible implications for future operation.

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TUPTY060

The FCC-ee Study: Progress and Challenges

2165

M. Koratzinos
DPNC, Genève, Switzerland
S. Aumon, C. Cook, A. Doblhammer, B. Härer, B.J. Holzer, R. Tomás, F. Zimmermann
CERN, Geneva, Switzerland
A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov
BINP SB RAS, Novosibirsk, Russia
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
L.E. Medina Medrano
UGTO, Leon, Mexico
U. Wienands
SLAC, Menlo Park, California, USA

The FCC (future circular collider) study represents a vision for the next large project in high energy physics, comprising a 80-100 km tunnel that can house a future 100TeV hadron collider. The study also includes a high luminosity e⁺e⁻ collider operating in the centre-of-mass energy range of 90-350 GeV as a possible intermediate step, the FCC-ee. The FCC-ee aims at definitive electro-weak precision measurements of the Z, W, H and top particles, and search for rare phenomena. Although FCC-ee is based on known technology, the goal performance in luminosity and energy calibration make it quite challenging. During 2014 the study went through an exploration phase and during the next three years a conceptual design report will be prepared.

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TUPTY061

Combined Operation and Staging Scenarios for the FCC-ee Lepton Collider

2169

M. Benedikt, B.J. Holzer, E. Jensen, R. Tomás, J. Wenninger, F. Zimmermann
CERN, Geneva, Switzerland
A.V. Bogomyagkov, E.B. Levichev, D.N. Shatilov
BINP SB RAS, Novosibirsk, Russia
K. Ohmi, K. Oide
KEK, Ibaraki, Japan
U. Wienands
SLAC, Menlo Park, California, USA

FCC-ee is a proposed high-energy electron positron circular collider that would initially occupy the 100-km FCC tunnel that will eventually house the 100 TeV FCC-hh hadron collider. The parameter range for the e⁺/e⁻ collider is large, operating at a cm energy from 90 GeV (Z-pole) to 350 GeV (t-tbar production) with the maximum beam current ranging from 1.5 A to 6 mA for each beam, corresponding to a synchrotron radiation power of 50 MW and a radiative energy loss varying from ~30 MeV/turn to ~7500 MeV/turn. This presents challenges for the rf system due to the varying rf voltage requirements and beam loading conditions. In this paper we present a possible gradual evolution of the FCC-ee complex by step-wise expansion, and possibly reconfiguration, of the superconducting RF system. The performance attainable at each step is discussed, along with the possible advantages and drawbacks.

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