IPAC2011 - Classification: 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques / A10 Damping Rings

Paper

Title

Page

Updates to the International Linear Collider Damping Rings Baseline Design

32

S. Guiducci, M.E. Biagini
INFN/LNF, Frascati (Roma), Italy
G. Dugan, M.A. Palmer, D. L. Rubin
CLASSE, Ithaca, New York, USA
J. Gao, D. Wang
IHEP Beijing, Beijing, People's Republic of China
M.T.F. Pivi, Y. Sun
SLAC, Menlo Park, California, USA
J. Urakawa
KEK, Ibaraki, Japan

A new baseline design for the International Linear Collider (ILC) damping rings has been adopted which reduces the ring circumference to 3.2 km from 6.4 km. This design change is associated with a revised plan to operate the ILC with one half the beam current originally specified in the ILC Reference Design Report. We describe the new layout and lattice that has been developed for the shorter ring. In addition, we discuss features of the new design that will allow operation at a 10Hz repetition rate which is twice the rate specified for baseline operation. Finally, we examine the implications for restoring operation with the originally specified beam current while maintaining the smaller ring circumference.

Slides MOOCA03 [2.381 MB]

TUYB02

The Challenges of Ultra-low Emittance Damping Rings

956

D. L. Rubin
CLASSE, Ithaca, New York, USA

Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538.
In this paper we review the state of the art of the design of damping rings for linear colliders, as supported by the experimental data from ATF and CESR test damping rings. We consider implications of measurements of electron cloud dynamics and mitigation in a radiation dominated ring. The techniques developed for tuning for ultra-low emittance in these rings are summarized. Other dynamics manifested in the ultra-low emittance regime where collective effects are important are discussed.

Slides TUYB02 [7.198 MB]

TUPC046

Alignment Tolerances for Vertical Emittance

1102

K.P. Wootton, R.P. Rassool, G. Taylor
The University of Melbourne, Melbourne, Australia
M.J. Boland, R.T. Dowd, G. LeBlanc, Y.E. Tan
ASCo, Clayton, Victoria, Australia
Y. Papaphilippou
CERN, Geneva, Switzerland

Alignment tolerances for the CLIC main damping ring magnetic lattice elements are presented. Tolerances are defined by the design equilibrium vertical emittance of 1 pm rad. The sensitivity of the uncorrected lattice to magnet misalignments is presented. Misalignments considered included quadrupole vertical offsets and rolls, sextupole vertical offsets, and main dipole rolls. Seeded simulations were conducted in MAD-X, and compared with expectation values calculated from theory. The lattice was found to be sensitive to betatron coupling as a result of sextupole vertical offsets in the arcs. Alignment tolerances, BPM and corrector requirements are presented also. For the same misalignment types, the equilibrium emittance of the corrected lattice is simulated. These are compared with expectation values calculated from theory. The vertical alignment tolerance of arc sextupoles is again demanding.

TUPC049

Optics considerations for the Delay Loop in the CLIC Damping Rings Complex

1108

P. Zisopoulos, F. Antoniou, H. Bartosik, Y. Papaphilippou
CERN, Geneva, Switzerland

For the recombination of the two trains coming from the CLIC damping rings, a delay loop will be used in order to obtain the nominal 0.5~ns bunch spacing. The optics design of the loop is based upon an isochronous ring, in order to preserve the longitudinal beam distribution. Analytical expressions for achieving isochronous conditions in high order for Theoretical Minimum Emittance cells are obtained. A parametrisation of the quadrupole settings for achieving these conditions is presented, along with general considerations regarding the choice of bending magnet characteristics.

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.

TUPC052

Normal Mode BPM Calibration for Ultralow-Emittance Tuning in Lepton Storage Rings

1114

A. Wolski
The University of Liverpool, Liverpool, United Kingdom
D. L. Rubin, D. Sagan, J.P. Shanks
CLASSE, Ithaca, New York, USA

BPMs capable of high-resolution turn-by-turn measurements offer the possibility of new techniques for tuning for ultra-low beam emittance. In this paper, we describe how signals collected from individual buttons during resonant beam excitation can be used to calibrate BPMs to read the beam position in a normal mode coordinate system. This allows for rapid minimization of the mode II emittance, simply by correcting the mode II dispersion. Simulations indicate that the technique is effective and robust, and has the benefit of being insensitive to BPM gain and alignment errors that can limit the effectiveness of other techniques.

Paper	Title	Page
MOOCA03	Updates to the International Linear Collider Damping Rings Baseline Design	32
	S. Guiducci, M.E. Biagini INFN/LNF, Frascati (Roma), Italy G. Dugan, M.A. Palmer, D. L. Rubin CLASSE, Ithaca, New York, USA J. Gao, D. Wang IHEP Beijing, Beijing, People's Republic of China M.T.F. Pivi, Y. Sun SLAC, Menlo Park, California, USA J. Urakawa KEK, Ibaraki, Japan
	A new baseline design for the International Linear Collider (ILC) damping rings has been adopted which reduces the ring circumference to 3.2 km from 6.4 km. This design change is associated with a revised plan to operate the ILC with one half the beam current originally specified in the ILC Reference Design Report. We describe the new layout and lattice that has been developed for the shorter ring. In addition, we discuss features of the new design that will allow operation at a 10Hz repetition rate which is twice the rate specified for baseline operation. Finally, we examine the implications for restoring operation with the originally specified beam current while maintaining the smaller ring circumference.
	Slides MOOCA03 [2.381 MB]

TUYB02	The Challenges of Ultra-low Emittance Damping Rings	956
	D. L. Rubin CLASSE, Ithaca, New York, USA
	Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538. In this paper we review the state of the art of the design of damping rings for linear colliders, as supported by the experimental data from ATF and CESR test damping rings. We consider implications of measurements of electron cloud dynamics and mitigation in a radiation dominated ring. The techniques developed for tuning for ultra-low emittance in these rings are summarized. Other dynamics manifested in the ultra-low emittance regime where collective effects are important are discussed.
	Slides TUYB02 [7.198 MB]

TUPC046	Alignment Tolerances for Vertical Emittance	1102
	K.P. Wootton, R.P. Rassool, G. Taylor The University of Melbourne, Melbourne, Australia M.J. Boland, R.T. Dowd, G. LeBlanc, Y.E. Tan ASCo, Clayton, Victoria, Australia Y. Papaphilippou CERN, Geneva, Switzerland
	Alignment tolerances for the CLIC main damping ring magnetic lattice elements are presented. Tolerances are defined by the design equilibrium vertical emittance of 1 pm rad. The sensitivity of the uncorrected lattice to magnet misalignments is presented. Misalignments considered included quadrupole vertical offsets and rolls, sextupole vertical offsets, and main dipole rolls. Seeded simulations were conducted in MAD-X, and compared with expectation values calculated from theory. The lattice was found to be sensitive to betatron coupling as a result of sextupole vertical offsets in the arcs. Alignment tolerances, BPM and corrector requirements are presented also. For the same misalignment types, the equilibrium emittance of the corrected lattice is simulated. These are compared with expectation values calculated from theory. The vertical alignment tolerance of arc sextupoles is again demanding.

TUPC049	Optics considerations for the Delay Loop in the CLIC Damping Rings Complex	1108
	P. Zisopoulos, F. Antoniou, H. Bartosik, Y. Papaphilippou CERN, Geneva, Switzerland
	For the recombination of the two trains coming from the CLIC damping rings, a delay loop will be used in order to obtain the nominal 0.5~ns bunch spacing. The optics design of the loop is based upon an isochronous ring, in order to preserve the longitudinal beam distribution. Analytical expressions for achieving isochronous conditions in high order for Theoretical Minimum Emittance cells are obtained. A parametrisation of the quadrupole settings for achieving these conditions is presented, along with general considerations regarding the choice of bending magnet characteristics.

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.

TUPC052	Normal Mode BPM Calibration for Ultralow-Emittance Tuning in Lepton Storage Rings	1114
	A. Wolski The University of Liverpool, Liverpool, United Kingdom D. L. Rubin, D. Sagan, J.P. Shanks CLASSE, Ithaca, New York, USA
	BPMs capable of high-resolution turn-by-turn measurements offer the possibility of new techniques for tuning for ultra-low beam emittance. In this paper, we describe how signals collected from individual buttons during resonant beam excitation can be used to calibrate BPMs to read the beam position in a normal mode coordinate system. This allows for rapid minimization of the mode II emittance, simply by correcting the mode II dispersion. Simulations indicate that the technique is effective and robust, and has the benefit of being insensitive to BPM gain and alignment errors that can limit the effectiveness of other techniques.