IPAC2013 - List of Authors (Bravin, E.)

Paper	Title	Page
MOPME072	Performance Tests of a Short Faraday Cup Designed for HIE-ISOLDE	646
	E.D. Cantero, W. Andreazza, E. Bravin, M.A. Fraser, D. Lanaia, A.G. Sosa, D. Voulot CERN, Geneva, Switzerland
	Funding: E.D.C, D.L. and A.S. acknowledge CATHI Marie Curie ITN: EU-FP7-PEOPLE-2010-ITN Project number 264330. M.A.F acknowledges co-funding by the European Commission (Grant agreement PCOFUND-GA-2010-267194) The On-Line Isotope Mass Separator (ISOLDE) facility at CERN is being upgraded in order to deliver higher energy and intensity radioactive beams. The final setup will consist in replacing the energy variable part of the normal conducting REX post-accelerator with superconducting cavities. In order to preserve the beam emittance, the drift space between the cryomodules housing these cavities has been kept to a minimum. As a consequence, the longitudinal space available for beam diagnostics is severely limited in the inter-cryomodule regions. A Faraday cup (FC) will be installed to measure beam currents, and due to the tight spatial constraints, its length is much smaller than usual. This poses a great challenge when trying to avoid the escape of ion-induced secondary electrons, which would falsify the current measurement. Two prototypes of such a short FC have therefore been tested at REX-ISOLDE using several beam intensities and energies, with the aim of determining its accuracy. In this paper the experimental results obtained for the two prototype cups are presented together with numerical calculations of the electrostatic fields that are produced inside the cup.

MOPME075	Laser Based Stripping System for Measurement of the Transverse Emittance of H⁻ Beams at the CERN LINAC4	652
	T. Hofmann, E. Bravin, U. Raich, F. Roncarolo CERN, Geneva, Switzerland B. Cheymol ESS, Lund, Sweden
	Funding: LA3NET is funded by the European Commission under Grant Agreement Number GA-ITN-2011-289191 The new LINAC4 at CERN will accelerate H⁻ particles to 160 MeV and allow high brightness proton beam transfers to the Proton Synchrotron Booster, via a charge-exchange injection scheme. This paper describes the conceptual design of a laser system proposed for transverse profile and emittance measurements based on photon detachment of electrons from the H⁻ ions. The binding energy of the outer electron is only 0.75 eV and can easily be stripped with a laser beam. Measuring the electron signal as function of the laser position allows the transverse beam profile to be reconstructed. A downstream dipole can also be used to separate the laser neutralized H⁰ atoms from the main H⁻ beam. By imaging these H⁰ atoms as a function of laser position the transverse emittance can be reconstructed in the same way as in traditional slit-and-grid systems. By properly dimensioning the laser power and spot size, this method results in negligible beam losses and is therefore non-destructive. In addition, the absence of material intercepting the H⁻ beam allows the measurement of a full power H⁻ beam. This paper will focus on the general design and integration of both the laser and H⁰ detector systems.

TUPFI062	Operational Results of the LHC Luminosity Monitors until LS1	1490
	A. Ratti, S.C. Hedges, J. Jones, H.S. Matis, M. Placidi, W.C. Turner, V.K. Vytla LBNL, Berkeley, California, USA E. Bravin, F. Roncarolo CERN, Geneva, Switzerland R. Miyamoto ESS, Lund, Sweden
	Funding: Work funded by the US Department of Energy through the US- LARP program. The monitors for the high luminosity regions in the LHC have been operating since 2009 to optimize the LHC's luminosity. The devices are gas ionization chambers inside the neutral particle absorber 140 m from the interaction point and monitor showers produced by high energy neutral particles from the collisions. They have the ability to resolve the bunch-by-bunch luminosity as well as to survive the extreme level of radiation in the nominal LHC operation. The devices have operated on a broad range of luminosity, from the initial 10²⁸ until the levels well beyond 10³³ reached in 2012. We present operational results of the device during proton and lead ion operations until LS1, which include runs at 40 MHz bunch rate and with p-Pb collisions.

TUPFI063	Electromagnetic Coupling between High Intensity LHC Beams and the Synchrotron Radiation Monitor Light Extraction System	1493
	F. Roncarolo, W. Andreazza, A. Bertarelli, E. Bravin, F. Caspers, M. Garlaschè, A. Goldblatt, J-J. Gras, O.R. Jones, T. Lefèvre, E. Métral, A.A. Nosych, B. Salvant, G. Trad, R. Veness, C. Vollinger, M. Wendt CERN, Geneva, Switzerland
	The CERN LHC is equipped with two Synchrotron Radiation Monitor systems used to characterise transverse and longitudinal beam distributions. Since the end of the 2011 LHC run the light extraction system, based on a retractable mirror, has suffered deformation and mechanical failure that is correlated to the increase in beam intensity. Temperature probes have associated these observations to a strong heating of the mirror support with a dependence on the longitudinal bunch length and shape, indicating the origin as electromagnetic coupling between the beam and the structure. This paper combines all this information with the aim of characterising and improving the system in view of its upgrade during the current LHC shutdown. Beam-based observations are presented along with electromagnetic and thermomechanical simulations and complemented by laboratory measurements, including the study of the RF properties of different mirror bulk and coating materials.

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

Paper

Title

Page

Performance Tests of a Short Faraday Cup Designed for HIE-ISOLDE

646

E.D. Cantero, W. Andreazza, E. Bravin, M.A. Fraser, D. Lanaia, A.G. Sosa, D. Voulot
CERN, Geneva, Switzerland

Funding: E.D.C, D.L. and A.S. acknowledge CATHI Marie Curie ITN: EU-FP7-PEOPLE-2010-ITN Project number 264330. M.A.F acknowledges co-funding by the European Commission (Grant agreement PCOFUND-GA-2010-267194)
The On-Line Isotope Mass Separator (ISOLDE) facility at CERN is being upgraded in order to deliver higher energy and intensity radioactive beams. The final setup will consist in replacing the energy variable part of the normal conducting REX post-accelerator with superconducting cavities. In order to preserve the beam emittance, the drift space between the cryomodules housing these cavities has been kept to a minimum. As a consequence, the longitudinal space available for beam diagnostics is severely limited in the inter-cryomodule regions. A Faraday cup (FC) will be installed to measure beam currents, and due to the tight spatial constraints, its length is much smaller than usual. This poses a great challenge when trying to avoid the escape of ion-induced secondary electrons, which would falsify the current measurement. Two prototypes of such a short FC have therefore been tested at REX-ISOLDE using several beam intensities and energies, with the aim of determining its accuracy. In this paper the experimental results obtained for the two prototype cups are presented together with numerical calculations of the electrostatic fields that are produced inside the cup.

MOPME075

Laser Based Stripping System for Measurement of the Transverse Emittance of H⁻ Beams at the CERN LINAC4

652

T. Hofmann, E. Bravin, U. Raich, F. Roncarolo
CERN, Geneva, Switzerland
B. Cheymol
ESS, Lund, Sweden

Funding: LA3NET is funded by the European Commission under Grant Agreement Number GA-ITN-2011-289191
The new LINAC4 at CERN will accelerate H⁻ particles to 160 MeV and allow high brightness proton beam transfers to the Proton Synchrotron Booster, via a charge-exchange injection scheme. This paper describes the conceptual design of a laser system proposed for transverse profile and emittance measurements based on photon detachment of electrons from the H⁻ ions. The binding energy of the outer electron is only 0.75 eV and can easily be stripped with a laser beam. Measuring the electron signal as function of the laser position allows the transverse beam profile to be reconstructed. A downstream dipole can also be used to separate the laser neutralized H⁰ atoms from the main H⁻ beam. By imaging these H⁰ atoms as a function of laser position the transverse emittance can be reconstructed in the same way as in traditional slit-and-grid systems. By properly dimensioning the laser power and spot size, this method results in negligible beam losses and is therefore non-destructive. In addition, the absence of material intercepting the H⁻ beam allows the measurement of a full power H⁻ beam. This paper will focus on the general design and integration of both the laser and H⁰ detector systems.

TUPFI062

Operational Results of the LHC Luminosity Monitors until LS1

1490

A. Ratti, S.C. Hedges, J. Jones, H.S. Matis, M. Placidi, W.C. Turner, V.K. Vytla
LBNL, Berkeley, California, USA
E. Bravin, F. Roncarolo
CERN, Geneva, Switzerland
R. Miyamoto
ESS, Lund, Sweden

Funding: Work funded by the US Department of Energy through the US- LARP program.
The monitors for the high luminosity regions in the LHC have been operating since 2009 to optimize the LHC's luminosity. The devices are gas ionization chambers inside the neutral particle absorber 140 m from the interaction point and monitor showers produced by high energy neutral particles from the collisions. They have the ability to resolve the bunch-by-bunch luminosity as well as to survive the extreme level of radiation in the nominal LHC operation. The devices have operated on a broad range of luminosity, from the initial 10²⁸ until the levels well beyond 10³³ reached in 2012. We present operational results of the device during proton and lead ion operations until LS1, which include runs at 40 MHz bunch rate and with p-Pb collisions.

TUPFI063

Electromagnetic Coupling between High Intensity LHC Beams and the Synchrotron Radiation Monitor Light Extraction System

1493

F. Roncarolo, W. Andreazza, A. Bertarelli, E. Bravin, F. Caspers, M. Garlaschè, A. Goldblatt, J-J. Gras, O.R. Jones, T. Lefèvre, E. Métral, A.A. Nosych, B. Salvant, G. Trad, R. Veness, C. Vollinger, M. Wendt
CERN, Geneva, Switzerland

The CERN LHC is equipped with two Synchrotron Radiation Monitor systems used to characterise transverse and longitudinal beam distributions. Since the end of the 2011 LHC run the light extraction system, based on a retractable mirror, has suffered deformation and mechanical failure that is correlated to the increase in beam intensity. Temperature probes have associated these observations to a strong heating of the mirror support with a dependence on the longitudinal bunch length and shape, indicating the origin as electromagnetic coupling between the beam and the structure. This paper combines all this information with the aim of characterising and improving the system in view of its upgrade during the current LHC shutdown. Beam-based observations are presented along with electromagnetic and thermomechanical simulations and complemented by laboratory measurements, including the study of the RF properties of different mirror bulk and coating materials.

TUPME032

Update on Beam Induced RF Heating in the LHC

1646

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

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