IPAC2016 - Classification: 01 Circular and Linear Colliders / A17 High Intensity Accelerators

Paper	Title	Page
WEPMW008	Possible Beam Parameters in Double RF Operation of the CERN LHC	2430
	E.N. Shaposhnikova, J.F. Esteban Müller CERN, Geneva, Switzerland
	The LHC operates using a 400 MHz SC RF system. A 200 MHz NC RF system was foreseen in the LHC Design Report to improve beam capture and the bare resonators were manufactured, but never installed. Later the second harmonic RF system was proposed to cure longitudinal beam instabilities in the absence of a dedicated wideband feedback system in the LHC. For nominal intensities the longitudinal beam stability is ensured by controlled emittance blow-up during the acceleration ramp. Recently slow growing instabilities were observed at the end of long fills at 6.5 TeV as bunches shrink due to synchrotron radiation damping. For High Luminosity LHC twice higher intensities should be kept stable with new equipment installed in the ring. Additional motivations for a second RF system in the LHC have also been considered. Operation with an extra RF system is limited by the required RF configuration (phase between the two RF systems) and longitudinal beam stability. In this work requirements for the double RF systems are analyzed together with a possible range of longitudinal beam parameters.
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WEPMW009	Towards a Mono-chromatization Scheme for Direct Higgs Production at FCC-ee	2434
SUPSS007	use link to see paper's listing under its alternate paper code
	M.A. Valdivia García, F. Zimmermann CERN, Geneva, Switzerland A. Faus-Golfe IFIC, Valencia, Spain
	Direct Higgs production in e⁺e⁻ collisions at the FCC is of interest if the centre-of-mass energy spread can be reduced by at least an order of magnitude. A mono-chromatization scheme, to accomplish this, can be realized with horizontal dispersion of opposite sign for the two colliding beams at the interaction point (IP). We review approaches from historical mono-chromatization studies, then derive a set of IP parameters which would provide the required performance in FCC e⁺e⁻ collisions at 63 GeV beam energy, compare these with the baseline optics parameters at neighbouring energies (45.6 and 80 GeV), comment on the effect of beamstrahlung, and, finally, discuss the modifications of the FCC-ee final-focus optics needed to obtain the required parameters.
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WEPMW010	Effect of Beamstrahlung on Bunch Length and Emittance in Future Circular e⁺e⁻ Colliders	2438
	M.A. Valdivia García, F. Zimmermann CERN, Geneva, Switzerland
	In future circular e⁺e⁻ colliders, beamstrahlung may limit the beam lifetime at high energies, and increase the energy spread and bunch length at low energies. If the dispersion or slop of the dispersion is not zero at the collision point, beamstrahlung will also affect the transverse emittance. In this paper, we first examine the beamstrahlung properties, and show that for the proposed FCC-ee, the radiation is fairly well modelled by the classical formulae describing synchrotron radiation in bending magnets. We then derive a set of equations describing the equilibrium beam parameters in the presence of a nonzero dispersion at the collision point. An example case from FCC-ee will serve as an illustration.
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Paper

Title

Page

Possible Beam Parameters in Double RF Operation of the CERN LHC

2430

E.N. Shaposhnikova, J.F. Esteban Müller
CERN, Geneva, Switzerland

The LHC operates using a 400 MHz SC RF system. A 200 MHz NC RF system was foreseen in the LHC Design Report to improve beam capture and the bare resonators were manufactured, but never installed. Later the second harmonic RF system was proposed to cure longitudinal beam instabilities in the absence of a dedicated wideband feedback system in the LHC. For nominal intensities the longitudinal beam stability is ensured by controlled emittance blow-up during the acceleration ramp. Recently slow growing instabilities were observed at the end of long fills at 6.5 TeV as bunches shrink due to synchrotron radiation damping. For High Luminosity LHC twice higher intensities should be kept stable with new equipment installed in the ring. Additional motivations for a second RF system in the LHC have also been considered. Operation with an extra RF system is limited by the required RF configuration (phase between the two RF systems) and longitudinal beam stability. In this work requirements for the double RF systems are analyzed together with a possible range of longitudinal beam parameters.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMW009

Towards a Mono-chromatization Scheme for Direct Higgs Production at FCC-ee

2434

SUPSS007

use link to see paper's listing under its alternate paper code

M.A. Valdivia García, F. Zimmermann
CERN, Geneva, Switzerland
A. Faus-Golfe
IFIC, Valencia, Spain

Direct Higgs production in e⁺e⁻ collisions at the FCC is of interest if the centre-of-mass energy spread can be reduced by at least an order of magnitude. A mono-chromatization scheme, to accomplish this, can be realized with horizontal dispersion of opposite sign for the two colliding beams at the interaction point (IP). We review approaches from historical mono-chromatization studies, then derive a set of IP parameters which would provide the required performance in FCC e⁺e⁻ collisions at 63 GeV beam energy, compare these with the baseline optics parameters at neighbouring energies (45.6 and 80 GeV), comment on the effect of beamstrahlung, and, finally, discuss the modifications of the FCC-ee final-focus optics needed to obtain the required parameters.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMW010

Effect of Beamstrahlung on Bunch Length and Emittance in Future Circular e⁺e⁻ Colliders

2438

M.A. Valdivia García, F. Zimmermann
CERN, Geneva, Switzerland

In future circular e⁺e⁻ colliders, beamstrahlung may limit the beam lifetime at high energies, and increase the energy spread and bunch length at low energies. If the dispersion or slop of the dispersion is not zero at the collision point, beamstrahlung will also affect the transverse emittance. In this paper, we first examine the beamstrahlung properties, and show that for the proposed FCC-ee, the radiation is fairly well modelled by the classical formulae describing synchrotron radiation in bending magnets. We then derive a set of equations describing the equilibrium beam parameters in the presence of a nonzero dispersion at the collision point. An example case from FCC-ee will serve as an illustration.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)