IPAC2013 - List of Authors (Vollinger, C.)

Paper	Title	Page
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.

TUPWA042	Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers	1802
	E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings CERN, Geneva, Switzerland
	Beam-induced RF heating has been observed in several LHC components when the bunch/beam intensity was increased and/or the bunch length reduced. In particular eight bellows, out of the ten double-bellows modules present in the machine in 2011, were found with the spring, which should keep the RF fingers in good electrical contact with the central insert, broken. Following these observations, the designs of all the components of the LHC equipped with RF fingers have been reviewed. The lessons learnt and mitigation measures are presented in this paper.

WEPFI054	Enlargement of Tuning Range in a Ferrite-tuned Cavity through Superposed Orthogonal and Parallel Magnetic Bias	2812
	C. Vollinger, F. Caspers CERN, Geneva, Switzerland
	Conventional ferrite-tuned cavities operate either with bias fields that are orthogonal or parallel to the magnetic RF-field. For a cavity that tunes rapidly over an overall frequency range around 100-400 MHz with high Q, we use ferrite garnets exposed to an innovative new biasing method consisting of a superposition of perpendicular and parallel magnetic fields. This method leads to a significant enlargement of the high-Q cavity tuning range by defining an operation point close to the magnetic saturation and thus improving ferrite material behaviour. A further advantage of this technique is the fast tuning speed resulting from the fact that tuning is carried out either with pure parallel biasing, or together with a very small change of operating point from perpendicular bias. In this paper, several scaled test models of ferrite-filled resonators are shown; measurements on the set-ups are compared and discussed.

Paper

Title

Page

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.

TUPWA042

Lessons Learned and Mitigation Measures for the CERN LHC Equipment with RF Fingers

1802

E. Métral, O. Aberle, R.W. Aßmann, V. Baglin, M.J. Barnes, O.E. Berrig, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Carra, F. Caspers, H.A. Day, M. Ferro-Luzzi, M.A. Gallilee, C. Garion, M. Garlaschè, A. Grudiev, J.M. Jimenez, O.R. Jones, O. Kononenko, R. Losito, J.L. Nougaret, V. Parma, S. Redaelli, B. Salvant, P.M. Strubin, R. Veness, C. Vollinger, W.J.M. Weterings
CERN, Geneva, Switzerland

Beam-induced RF heating has been observed in several LHC components when the bunch/beam intensity was increased and/or the bunch length reduced. In particular eight bellows, out of the ten double-bellows modules present in the machine in 2011, were found with the spring, which should keep the RF fingers in good electrical contact with the central insert, broken. Following these observations, the designs of all the components of the LHC equipped with RF fingers have been reviewed. The lessons learnt and mitigation measures are presented in this paper.

WEPFI054

Enlargement of Tuning Range in a Ferrite-tuned Cavity through Superposed Orthogonal and Parallel Magnetic Bias

2812

C. Vollinger, F. Caspers
CERN, Geneva, Switzerland

Conventional ferrite-tuned cavities operate either with bias fields that are orthogonal or parallel to the magnetic RF-field. For a cavity that tunes rapidly over an overall frequency range around 100-400 MHz with high Q, we use ferrite garnets exposed to an innovative new biasing method consisting of a superposition of perpendicular and parallel magnetic fields. This method leads to a significant enlargement of the high-Q cavity tuning range by defining an operation point close to the magnetic saturation and thus improving ferrite material behaviour. A further advantage of this technique is the fast tuning speed resulting from the fact that tuning is carried out either with pure parallel biasing, or together with a very small change of operating point from perpendicular bias. In this paper, several scaled test models of ferrite-filled resonators are shown; measurements on the set-ups are compared and discussed.