IPAC2016 - List of Authors (Haerer, B.)

Paper	Title	Page
THPOR001	Tolerance Studies and Dispersion Free Steering for Extreme Low Emittance in the FCC-ee Project	3759
	S. Aumon, A. Doblhammer, B. Härer, B.J. Holzer CERN, Geneva, Switzerland B. Härer KIT, Karlsruhe, Germany K. Oide KEK, Ibaraki, Japan
	The FCC-ee study is investigating the design of a 100 km e⁺/e⁻ circular collider for precision measurements and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities in the order of 10³⁵ cm^-2s^-1. In order to reach such performances, an extreme focusing of the beam is required in the interaction regions with a low vertical beta function of 2 mm at the IP. Moreover, the FCC-ee physics program requires very low emittances never achieved in a collider with 2 nm for ε_x and 2 pm for ε_y, reducing the coupling ratio to 1/1000. With such requirements, any field errors and sources of coupling will introduce spurious vertical dispersion which degrades emittances, limiting the luminosity of the machine. This paper describes the tolerance study and the impact of errors will affect the vertical emittance. In order to preserve the FCC-ee performances, in particular ε_y, a challenging correction scheme is proposed to keep the coupling and the vertical emittance as low as possible.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR001
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THPOR003	Tapering Options and Emittance Fine Tuning for the FCC-ee Collider	3767
	B. Härer, A. Doblhammer, B.J. Holzer CERN, Geneva, Switzerland
	The lepton collider version of the FCC study describes a future electron-positron collider with a circumference in the order of 100 km, optimised for operation with collision energies in the range of 90 GeV to 350 GeV (FCC- ee). This paper presents the layout of the machine and the constraints on the design of the arc lattice in the context of the four different beam energies that are foreseen for beam operation. Special emphasis is put on the compensation of the effect of the strong synchrotron radiation losses. The beam orbit as well as the optics have to be re-optimised for a given operation energy in order to achieve the foreseen emittance of ε = 1 nm in the horizontal and 1 pm in the vertical plane. Counter measures of the so-called saw-tooth effect of the design orbit are needed as well as a compensation of the energy loss on the beam optics. The paper summarizes different scenarios of how to achieve this goal as well as the need for additional emittance fine tuning using wiggler magnets.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR003
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THPOR022	Design of Beam Optics for the FCC-ee Collider Ring	3821
	K. Oide, K. Ohmi, D. Zhou KEK, Ibaraki, Japan M. Aiba PSI, Villigen PSI, Switzerland S. Aumon, M. Benedikt, H. Burkhardt, A. Doblhammer, B. Härer, B.J. Holzer, J.M. Jowett, M. Koratzinos, L.E. Medina Medrano, Y. Papaphilippou, J. Wenninger, F. Zimmermann CERN, Geneva, Switzerland A.P. Blondel DPNC, Genève, Switzerland A.V. Bogomyagkov, I. Koop, E.B. Levichev, P.A. Piminov, D.N. Shatilov, D.B. Shwartz, S.V. Sinyatkin BINP SB RAS, Novosibirsk, Russia M. Boscolo INFN/LNF, Frascati (Roma), Italy Y. Cai, M.K. Sullivan, U. Wienands SLAC, Menlo Park, California, USA
	A design of beam optics will be presented for the FCC-ee double-ring collider. The main characteristics are 45 to 175 GeV beam energy, 100 km circumference with two IPs/ring, 30 mrad crossing angle at the IP, crab-waist scheme with local chromaticity correction system, and "tapering" of the magnets along with the local beam energy. An asymmetric layout near the interaction region suppresses the critical energy of synchrotron radiation toward the detector at the IP less than 100 keV, while keeping the geometry as close as to the FCC-hh beam line. A sufficient transverse/longitudinal dynamic aperture is obtained to assure the lifetime with beamstrahlung and top-up injection. The synchrotron radiation in all magnets, the IP solenoid and its compensation, nonlinearity of the final quadrupoles are taken into account.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR022
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THPOR002	Chromaticity Compensation Schemes for the Arc Lattice of the FCC-ee Collider	3763
SUPSS048	use link to see paper's listing under its alternate paper code
	B. Härer KIT, Karlsruhe, Germany A. Doblhammer, B.J. Holzer CERN, Geneva, Switzerland
	FCC-ee is an 100 km e⁺/e⁻ collider that is being designed within the Future Circular Collider Study organised by CERN. It's layout is optimised for precision studies and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities in the order of 10³⁵ cm^-2s^-1. Extremely small vertical beta functions of 1 - 2 mm are required at the two interaction points to reach this goal. The strong focusing required in the final doublet quadrupoles drives the chromaticity to more than -2000 units, far beyond the values that had been achieved in previous storage rings. As a consequence a pure linear chromaticity compensation scheme will not be sufficient to obtain the required ± 2 % energy acceptance. A state of the art multi-family sextupole scheme will have to be combined with a local chromaticity correction. This paper presents the design of the arc lattice, optimised for highest momentum acceptance and the results of systematic studies of the sextupole scheme in the arcs in order to gain highest chromaticity performance.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR002
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Paper

Title

Page

Tolerance Studies and Dispersion Free Steering for Extreme Low Emittance in the FCC-ee Project

3759

S. Aumon, A. Doblhammer, B. Härer, B.J. Holzer
CERN, Geneva, Switzerland
B. Härer
KIT, Karlsruhe, Germany
K. Oide
KEK, Ibaraki, Japan

The FCC-ee study is investigating the design of a 100 km e⁺/e⁻ circular collider for precision measurements and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities in the order of 10³⁵ cm^-2s^-1. In order to reach such performances, an extreme focusing of the beam is required in the interaction regions with a low vertical beta function of 2 mm at the IP. Moreover, the FCC-ee physics program requires very low emittances never achieved in a collider with 2 nm for ε_x and 2 pm for ε_y, reducing the coupling ratio to 1/1000. With such requirements, any field errors and sources of coupling will introduce spurious vertical dispersion which degrades emittances, limiting the luminosity of the machine. This paper describes the tolerance study and the impact of errors will affect the vertical emittance. In order to preserve the FCC-ee performances, in particular ε_y, a challenging correction scheme is proposed to keep the coupling and the vertical emittance as low as possible.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR001

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THPOR003

Tapering Options and Emittance Fine Tuning for the FCC-ee Collider

3767

B. Härer, A. Doblhammer, B.J. Holzer
CERN, Geneva, Switzerland

The lepton collider version of the FCC study describes a future electron-positron collider with a circumference in the order of 100 km, optimised for operation with collision energies in the range of 90 GeV to 350 GeV (FCC- ee). This paper presents the layout of the machine and the constraints on the design of the arc lattice in the context of the four different beam energies that are foreseen for beam operation. Special emphasis is put on the compensation of the effect of the strong synchrotron radiation losses. The beam orbit as well as the optics have to be re-optimised for a given operation energy in order to achieve the foreseen emittance of ε = 1 nm in the horizontal and 1 pm in the vertical plane. Counter measures of the so-called saw-tooth effect of the design orbit are needed as well as a compensation of the energy loss on the beam optics. The paper summarizes different scenarios of how to achieve this goal as well as the need for additional emittance fine tuning using wiggler magnets.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR003

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THPOR022

Design of Beam Optics for the FCC-ee Collider Ring

3821

K. Oide, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
M. Aiba
PSI, Villigen PSI, Switzerland
S. Aumon, M. Benedikt, H. Burkhardt, A. Doblhammer, B. Härer, B.J. Holzer, J.M. Jowett, M. Koratzinos, L.E. Medina Medrano, Y. Papaphilippou, J. Wenninger, F. Zimmermann
CERN, Geneva, Switzerland
A.P. Blondel
DPNC, Genève, Switzerland
A.V. Bogomyagkov, I. Koop, E.B. Levichev, P.A. Piminov, D.N. Shatilov, D.B. Shwartz, S.V. Sinyatkin
BINP SB RAS, Novosibirsk, Russia
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
Y. Cai, M.K. Sullivan, U. Wienands
SLAC, Menlo Park, California, USA

A design of beam optics will be presented for the FCC-ee double-ring collider. The main characteristics are 45 to 175 GeV beam energy, 100 km circumference with two IPs/ring, 30 mrad crossing angle at the IP, crab-waist scheme with local chromaticity correction system, and "tapering" of the magnets along with the local beam energy. An asymmetric layout near the interaction region suppresses the critical energy of synchrotron radiation toward the detector at the IP less than 100 keV, while keeping the geometry as close as to the FCC-hh beam line. A sufficient transverse/longitudinal dynamic aperture is obtained to assure the lifetime with beamstrahlung and top-up injection. The synchrotron radiation in all magnets, the IP solenoid and its compensation, nonlinearity of the final quadrupoles are taken into account.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR022

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THPOR002

Chromaticity Compensation Schemes for the Arc Lattice of the FCC-ee Collider

3763

SUPSS048

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

B. Härer
KIT, Karlsruhe, Germany
A. Doblhammer, B.J. Holzer
CERN, Geneva, Switzerland

FCC-ee is an 100 km e⁺/e⁻ collider that is being designed within the Future Circular Collider Study organised by CERN. It's layout is optimised for precision studies and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities in the order of 10³⁵ cm^-2s^-1. Extremely small vertical beta functions of 1 - 2 mm are required at the two interaction points to reach this goal. The strong focusing required in the final doublet quadrupoles drives the chromaticity to more than -2000 units, far beyond the values that had been achieved in previous storage rings. As a consequence a pure linear chromaticity compensation scheme will not be sufficient to obtain the required ± 2 % energy acceptance. A state of the art multi-family sextupole scheme will have to be combined with a local chromaticity correction. This paper presents the design of the arc lattice, optimised for highest momentum acceptance and the results of systematic studies of the sextupole scheme in the arcs in order to gain highest chromaticity performance.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR002

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