IPAC2011 - List of Authors (Salvant, B.)

Paper

Title

Page

Probing Intensity Limits of LHC-type Bunches in the CERN SPS with Nominal Optics

610

B. Salvant, G. Adrian, D.J. Allen, O. Andujar, T. Argyropoulos, J. Axensalva, J. Baldy, H. Bartosik, S. Cettour Cave, F. Chapuis, J.F. Comblin, K. Cornelis, D.G. Cotte, K. Cunnington, H. Damerau, M. Delrieux, J.L. Duran-Lopez, A. Findlay, J. Fleuret, F. Follin, P. Freyermuth, H. Genoud, S.S. Gilardoni, A. Guerrero, S. Hancock, K. Hanke, O. Hans, R. Hazelaar, W. Höfle, L.K. Jensen, J. Kuczerowski, Y. Le Borgne, R. Maillet, D. Manglunki, S. Massot, E. Matli, G. Metral, B. Mikulec, E. Métral, J.-M. Nonglaton, E. Ovalle, L. Pereira, F.C. Peters, A. Rey, J.P. Ridewood, G. Rumolo, J.L. Sanchez Alvarez, E.N. Shaposhnikova, R.R. Steerenberg, R.J. Steinhagen, J. Tan, B. Vandorpe, E. Veyrunes
CERN, Geneva, Switzerland

Some of the upgrade scenarios of the high-luminosity LHC require large intensity per bunch from the injector chain. Single bunch beams with intensities of up to 3.5 to 4·10¹¹ p/b and nominal emittances were successfully produced in the PS Complex and delivered to the SPS in 2010. This contribution presents results of studies with this new intense beam in the SPS to probe single bunch intensity limitations with nominal gamma transition. In particular, the vertical Transverse Mode Coupling Instability (TMCI) threshold with low chromaticity was observed at 1.6·10¹¹ p/b for single nominal LHC bunches in the SPS. With increased vertical chromaticity, larger intensities could be injected, stored along the flat bottom and accelerated up to 450 GeV/c. However, significant losses and/or transverse emittance blow up were then observed. Longitudinal and transverse optimization efforts in the PSB, PS and SPS were put in place to minimize this beam degradation and succeeded to obtain single 2.3·10¹¹ p/b LHC type bunches with satisfying parameters at extraction of the SPS.

MOPS010

Experimental Studies with Low Transition Energy Optics in the SPS

613

H. Bartosik, T. Argyropoulos, T. Bohl, S. Cettour Cave, K. Cornelis, J. Esteban Muller, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, J. Wenninger
CERN, Geneva, Switzerland

The optics of the SPS can be tuned to lower transition energy such that the slippage factor at injection is raised by a factor of almost 3. From theory, an increase of the intensity thresholds for transverse mode coupling, longitudinal coupled bunch and longitudinal instabilities due to the loss of Landau damping can be expected. In this paper, experimental studies in the SPS with single bunches of protons with intensities of up to 3.5·10¹¹ p/b on the flat bottom and at 450 GeV/c are presented. Longitudinal instabilities were studied with LHC-type beams with 50~ns spacing and injected intensities up to 1.8·10¹¹ p/b. The measurements address the increase of intensity thresholds and the achievable transverse emittances in the new low gamma transition optics with respect to the nominal SPS optics. The obtained results are compared with numerical simulations.

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.

MOPS070

Electromagnetic Modeling of C Shape Ferrite Loaded Kickers

763

C. Zannini
EPFL, Lausanne, Switzerland
E. Métral, G. Rumolo, B. Salvant, V.G. Vaccaro, C. Zannini
CERN, Geneva, Switzerland

The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of an intensity upgrade of the LHC. In this paper, analytical approach and CST Particle Studio time domain electromagnetic simulations are performed to obtain the longitudinal and transverse impedances/wake potentials of models of ferrite loaded kickers. It turns out that the existing models are not sufficient to characterize correctly these components from the coupling impedance point of view. In particular the results show that below few hundred MHz the real C-structure of the magnet cannot be neglected. Therefore an analytical model was developed and benchmarked with EM simulations to take into account the C-shape of the magnet.

MOPS073

Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime

772

N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini
CERN, Geneva, Switzerland
N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy
Q. Qin, N. Wang
IHEP Beijing, Beijing, People's Republic of China

Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.

MOPS074

Stabilization of the LHC Single-bunch Transverse Instability at High-energy by Landau Octupoles

775

E. Métral, B. Salvant
CERN, Geneva, Switzerland
N. Mounet
EPFL, Lausanne, Switzerland

When the first ramp was tried on Saturday 15/05/2010 with a single bunch of about nominal intensity (i.e. ~ 10¹1 p/b), the bunch became unstable in the horizontal plane at ~ 2 TeV. The three main observations were: (i) a “Christmas tree” in the transverse tune measurement application (with many synchrotron sidebands excited), (ii) beam losses (few tens of percents) in IR7, and (iii) an increase of the bunch length. This transverse coherent instability has been stabilized successfully with Landau octupoles. Comparing all the measurements performed during this first year of LHC commissioning with the theoretical and simulation predictions reveals a good agreement.

MOPS078

Coaxial Wire Measurements of Ferrite Kicker Magnets

784

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.

MOPS080

Comparison of the Current LHC Collimators and the SLAC Phase 2 Collimator Impedances

790

H.A. Day, R.M. Jones
UMAN, Manchester, United Kingdom
F. Caspers, H.A. Day, E. Métral, B. Salvant
CERN, Geneva, Switzerland

One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

TUPC050

Impedance Effects in the CLIC Damping Rings

1111

E. Koukovini, K.S.B. Li, N. Mounet, G. Rumolo, B. Salvant
CERN, Geneva, Switzerland

Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity proved that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive-wall wake fields on the transverse impedance budget is finally discussed.

THOBA01

Electron Cloud Observations in LHC

2862

G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann
CERN, Geneva, Switzerland
C.M. Bhat
Fermilab, Batavia, USA
U. Iriso
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
N. Mounet, C. Zannini
EPFL, Lausanne, Switzerland

Operation of LHC with bunch trains different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build-up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as a strong instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity and/or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with existing models will be presented. The efficiency of scrubbing and scrubbing strategies to improve the machine running performance will be also briefly discussed.

Slides THOBA01 [2.911 MB]

MOPS071

Simulations of the Impedance of the New PS Wire Scanner Tank

766

B. Salvant
EPFL, Lausanne, Switzerland
W. Andreazza, F. Caspers, A. Grudiev, J.F. Herranz Alvarez, E. Métral, G. Rumolo
CERN, Geneva, Switzerland

The CERN PS is equipped with 4 wire scanners. It was identified that the small aperture of the current wire scanner tank causes beam losses and a new tank design was needed. The interaction of the PS bunches with the beam coupling impedance of this new tank may lead to beam degradation and wire damage. This contribution presents impedance studies of the current PS tank as well as the new design in order to assess the need to modify the design and/or install lossy materials plates dedicated to damp higher order cavity modes and reduce the total power deposited by the beam in the tank.

TUPS026

Specification of New Vacuum Chambers for the LHC Experimental Interactions

1584

R. Veness, R.W. Assmann, A. Ball, A. Behrens, C. Bracco, G. Bregliozzi, R. Bruce, H. Burkhardt, G. Corti, M.A. Gallilee, M. Giovannozzi, B. Goddard, D. Mergelkuhl, E. Métral, M. Nessi, W. Riegler, J. Wenninger
CERN, Geneva, Switzerland
N. Mounet, B. Salvant
EPFL, Lausanne, Switzerland

The apertures for the vacuum chambers at the interaction points inside the LHC experiments are key both to the safe operation of the LHC machine and to obtaining the best physics performance from the experiments. Following the successful startup of the LHC physics programme the ALICE, ATLAS and CMS experiments have launched projects to improve physics performance by adding detector layers closer to the beam. To achieve this they have requested smaller aperture vacuum chambers to be installed. The first periods of LHC operation have yielded much information both on the performance of the LHC and the stability and alignment of the experiments. In this paper, the new information relating to the aperture of these chambers is presented and a summary is made of analysis of parameters required to safely reduce the vacuum chambers apertures for the high-luminosity experiments ATLAS and CMS.

Paper	Title	Page
MOPS009	Probing Intensity Limits of LHC-type Bunches in the CERN SPS with Nominal Optics	610
	B. Salvant, G. Adrian, D.J. Allen, O. Andujar, T. Argyropoulos, J. Axensalva, J. Baldy, H. Bartosik, S. Cettour Cave, F. Chapuis, J.F. Comblin, K. Cornelis, D.G. Cotte, K. Cunnington, H. Damerau, M. Delrieux, J.L. Duran-Lopez, A. Findlay, J. Fleuret, F. Follin, P. Freyermuth, H. Genoud, S.S. Gilardoni, A. Guerrero, S. Hancock, K. Hanke, O. Hans, R. Hazelaar, W. Höfle, L.K. Jensen, J. Kuczerowski, Y. Le Borgne, R. Maillet, D. Manglunki, S. Massot, E. Matli, G. Metral, B. Mikulec, E. Métral, J.-M. Nonglaton, E. Ovalle, L. Pereira, F.C. Peters, A. Rey, J.P. Ridewood, G. Rumolo, J.L. Sanchez Alvarez, E.N. Shaposhnikova, R.R. Steerenberg, R.J. Steinhagen, J. Tan, B. Vandorpe, E. Veyrunes CERN, Geneva, Switzerland
	Some of the upgrade scenarios of the high-luminosity LHC require large intensity per bunch from the injector chain. Single bunch beams with intensities of up to 3.5 to 4·10¹¹ p/b and nominal emittances were successfully produced in the PS Complex and delivered to the SPS in 2010. This contribution presents results of studies with this new intense beam in the SPS to probe single bunch intensity limitations with nominal gamma transition. In particular, the vertical Transverse Mode Coupling Instability (TMCI) threshold with low chromaticity was observed at 1.6·10¹¹ p/b for single nominal LHC bunches in the SPS. With increased vertical chromaticity, larger intensities could be injected, stored along the flat bottom and accelerated up to 450 GeV/c. However, significant losses and/or transverse emittance blow up were then observed. Longitudinal and transverse optimization efforts in the PSB, PS and SPS were put in place to minimize this beam degradation and succeeded to obtain single 2.3·10¹¹ p/b LHC type bunches with satisfying parameters at extraction of the SPS.

MOPS010	Experimental Studies with Low Transition Energy Optics in the SPS	613
	H. Bartosik, T. Argyropoulos, T. Bohl, S. Cettour Cave, K. Cornelis, J. Esteban Muller, Y. Papaphilippou, G. Rumolo, B. Salvant, E.N. Shaposhnikova, J. Wenninger CERN, Geneva, Switzerland
	The optics of the SPS can be tuned to lower transition energy such that the slippage factor at injection is raised by a factor of almost 3. From theory, an increase of the intensity thresholds for transverse mode coupling, longitudinal coupled bunch and longitudinal instabilities due to the loss of Landau damping can be expected. In this paper, experimental studies in the SPS with single bunches of protons with intensities of up to 3.5·10¹¹ p/b on the flat bottom and at 450 GeV/c are presented. Longitudinal instabilities were studied with LHC-type beams with 50~ns spacing and injected intensities up to 1.8·10¹¹ p/b. The measurements address the increase of intensity thresholds and the achievable transverse emittances in the new low gamma transition optics with respect to the nominal SPS optics. The obtained results are compared with numerical simulations.

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.

MOPS070	Electromagnetic Modeling of C Shape Ferrite Loaded Kickers	763
	C. Zannini EPFL, Lausanne, Switzerland E. Métral, G. Rumolo, B. Salvant, V.G. Vaccaro, C. Zannini CERN, Geneva, Switzerland
	The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of an intensity upgrade of the LHC. In this paper, analytical approach and CST Particle Studio time domain electromagnetic simulations are performed to obtain the longitudinal and transverse impedances/wake potentials of models of ferrite loaded kickers. It turns out that the existing models are not sufficient to characterize correctly these components from the coupling impedance point of view. In particular the results show that below few hundred MHz the real C-structure of the magnet cannot be neglected. Therefore an analytical model was developed and benchmarked with EM simulations to take into account the C-shape of the magnet.

MOPS073	Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime	772
	N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini CERN, Geneva, Switzerland N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo Rome University La Sapienza, Roma, Italy Q. Qin, N. Wang IHEP Beijing, Beijing, People's Republic of China
	Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.

MOPS074	Stabilization of the LHC Single-bunch Transverse Instability at High-energy by Landau Octupoles	775
	E. Métral, B. Salvant CERN, Geneva, Switzerland N. Mounet EPFL, Lausanne, Switzerland
	When the first ramp was tried on Saturday 15/05/2010 with a single bunch of about nominal intensity (i.e. ~ 10¹1 p/b), the bunch became unstable in the horizontal plane at ~ 2 TeV. The three main observations were: (i) a “Christmas tree” in the transverse tune measurement application (with many synchrotron sidebands excited), (ii) beam losses (few tens of percents) in IR7, and (iii) an increase of the bunch length. This transverse coherent instability has been stabilized successfully with Landau octupoles. Comparing all the measurements performed during this first year of LHC commissioning with the theoretical and simulation predictions reveals a good agreement.

MOPS078	Coaxial Wire Measurements of Ferrite Kicker Magnets	784
	H.A. Day, R.M. Jones UMAN, Manchester, United Kingdom M.J. Barnes, F. Caspers, H.A. Day, E. Métral, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	Fast kicker magnets are used to inject beam into and eject beam out of the CERN accelerator rings. These kickers are generally transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the yoke can provoke significant beam induced heating, especially for high intensities. In addition the impedance may contribute to beam instabilities. The results of longitudinal and transverse impedance measurements, for various kicker magnets, are presented and compared with analytical calculations: in addition predictions from a numerical analysis are discussed.

MOPS080	Comparison of the Current LHC Collimators and the SLAC Phase 2 Collimator Impedances	790
	H.A. Day, R.M. Jones UMAN, Manchester, United Kingdom F. Caspers, H.A. Day, E. Métral, B. Salvant CERN, Geneva, Switzerland
	One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.

TUPC050	Impedance Effects in the CLIC Damping Rings	1111
	E. Koukovini, K.S.B. Li, N. Mounet, G. Rumolo, B. Salvant CERN, Geneva, Switzerland
	Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity proved that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive-wall wake fields on the transverse impedance budget is finally discussed.

THOBA01	Electron Cloud Observations in LHC	2862
	G. Rumolo, G. Arduini, V. Baglin, H. Bartosik, P. Baudrenghien, N. Biancacci, G. Bregliozzi, S.D. Claudet, R. De Maria, J. Esteban Muller, M. Favier, C. Hansen, W. Höfle, J.M. Jimenez, V. Kain, E. Koukovini, G. Lanza, K.S.B. Li, G.H.I. Maury Cuna, E. Métral, G. Papotti, T. Pieloni, F. Roncarolo, B. Salvant, E.N. Shaposhnikova, R.J. Steinhagen, L.J. Tavian, D. Valuch, W. Venturini Delsolaro, F. Zimmermann CERN, Geneva, Switzerland C.M. Bhat Fermilab, Batavia, USA U. Iriso CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain N. Mounet, C. Zannini EPFL, Lausanne, Switzerland
	Operation of LHC with bunch trains different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build-up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as a strong instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity and/or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with existing models will be presented. The efficiency of scrubbing and scrubbing strategies to improve the machine running performance will be also briefly discussed.
	Slides THOBA01 [2.911 MB]

MOPS071	Simulations of the Impedance of the New PS Wire Scanner Tank	766
	B. Salvant EPFL, Lausanne, Switzerland W. Andreazza, F. Caspers, A. Grudiev, J.F. Herranz Alvarez, E. Métral, G. Rumolo CERN, Geneva, Switzerland
	The CERN PS is equipped with 4 wire scanners. It was identified that the small aperture of the current wire scanner tank causes beam losses and a new tank design was needed. The interaction of the PS bunches with the beam coupling impedance of this new tank may lead to beam degradation and wire damage. This contribution presents impedance studies of the current PS tank as well as the new design in order to assess the need to modify the design and/or install lossy materials plates dedicated to damp higher order cavity modes and reduce the total power deposited by the beam in the tank.

TUPS026	Specification of New Vacuum Chambers for the LHC Experimental Interactions	1584
	R. Veness, R.W. Assmann, A. Ball, A. Behrens, C. Bracco, G. Bregliozzi, R. Bruce, H. Burkhardt, G. Corti, M.A. Gallilee, M. Giovannozzi, B. Goddard, D. Mergelkuhl, E. Métral, M. Nessi, W. Riegler, J. Wenninger CERN, Geneva, Switzerland N. Mounet, B. Salvant EPFL, Lausanne, Switzerland
	The apertures for the vacuum chambers at the interaction points inside the LHC experiments are key both to the safe operation of the LHC machine and to obtaining the best physics performance from the experiments. Following the successful startup of the LHC physics programme the ALICE, ATLAS and CMS experiments have launched projects to improve physics performance by adding detector layers closer to the beam. To achieve this they have requested smaller aperture vacuum chambers to be installed. The first periods of LHC operation have yielded much information both on the performance of the LHC and the stability and alignment of the experiments. In this paper, the new information relating to the aperture of these chambers is presented and a summary is made of analysis of parameters required to safely reduce the vacuum chambers apertures for the high-luminosity experiments ATLAS and CMS.