Beam dynamic simulations of the CLIC crab cavity and implications on the BDS

Shinton, I.R.R.; Glasman, C.J.; Jones, R.M.; Wolski, A.

doi:10.1016/j.nima.2011.05.059

Cited by 2 publications

(6 citation statements)

References 5 publications

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“…In their own center of mass, they interact with zero crossing angle and a priori they suffer no luminosity loss [3]. Nevertheless, some luminosity degradation has been recently first observed in simulations for the CLIC baseline configuration [5]. The reasons for the loss of luminosity are explored and some possible cures are proposed.…”

Section: Introductionmentioning

confidence: 99%

Luminosity studies in a traveling waist regime in the Compact Linear Collider

García

Lacoma

García

2013

Phys. Rev. ST Accel. Beams

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The final focus system of the Compact Linear Collider (CLIC) features a crab cavity just before the final quadrupole doublet to ensure head-on collisions at the interaction point. A decrease in the expected luminosity with respect to the case without crossing angle has been recently observed in simulations for the CLIC baseline configuration. This effect is explained from the aberrations induced due to a z-dependent off-center horizontal orbit in the final focus sextupoles produced by the crab cavity. Three options to recover from this loss are explored. The effect of the longitudinal E-z correlation of the incoming beam from the linac is taken into account and its effect on the expected luminosity is evaluated.

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Section: Introductionmentioning

confidence: 99%

Luminosity studies in a traveling waist regime in the Compact Linear Collider

García

Lacoma

García

2013

Phys. Rev. ST Accel. Beams

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“…[95] and [96]. In previous studies with a single crab cavity located prior to the FD a luminosity loss of 5% with respect to L (head−on) of the CLIC baseline design was obtained [93]. The goal of the study in the present thesis is to understand this 5% luminosity loss and to look for solutions that allow to fully recover the design luminosity.…”

Section: Clic Bds Lattice Optimisationmentioning

confidence: 90%

“…32 shows, more details can be found in Refs. [95] and [96]. In previous studies with a single crab cavity located prior to the FD a luminosity loss of 5% with respect to L (head−on) of the CLIC baseline design was obtained [93].…”

Section: Clic Bds Lattice Optimisationmentioning

confidence: 99%

“…To prevent a luminosity loss due to the non-zero crossing angle a single crab cavity per beam line is foreseen to provide the head-on collisions at the IP. However, it has been recently found that the crab cavity only recovers up to 95% of the design luminosity [93] and in addition the vertical beam size increases by about 1%. In this section different solutions to recover the design luminosity are described.…”

Section: Ffs Lattice Design and Optimisationmentioning

confidence: 99%

“…x ≪ σ * z is satisfied, the reduction of the geometric luminosity is expressed by the following relation [93]:…”

Section: Clic Bds Lattice Optimisationmentioning

confidence: 99%

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Design and higher order optimisation of final focus systems for linear colliders

Marín Lacoma

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The accelerator and particle physics communities are considering a lepton Linear Collider LC as the most appropriate machine to carry out high precision particle physics research in the TeV energy regime. The Compact Linear Collider CLIC and the International Linear Collider ILC are the two proposals for the future e+e- LC. Both designs achieve a luminosity L above 10^(34) cm-2 s-1 at the interaction point IP, satisfying the particle physics requirements. The LC consists of different systems, being the Final Focus System FFS the last one before colliding the beam at the IP. It is responsible to focus the beams at sizes in the range of nanometres by means of the Final Doublet FD. The FFS designs of the CLIC and ILC projects are based on a new local chromaticity correction scheme which has never been experimentally tested before. The Accelerator Test Facility ATF2 at KEK (Japan) aims to experimentally verify the feasibility of the FFS based on this novel scheme. The present thesis is devoted to the design and higher order optimisation of FFS for linear colliders based on the local chromaticity correction scheme. The CLIC design luminosity L0 is 5.9·10^(34) cm-2 s-1 assuming head-on collisions. However the beams cross each other at the IP forming an angle of 20 mrad. Due to this crossing scheme the luminosity would be reduced by 90%. Crab cavities are dedicated to tilt the bunches in order to provide head-on like collisions preserving the design L0. In this thesis different solutions that recover the design luminosity for the CLIC FFS are proposed. The designs of a new ATF2 Nominal and Ultra-low beta* lattices, to test the feasibility of the ILC and CLIC FFS respectively, are presented in this thesis. The expected IP vertical beam sizes sy* for these lattices are 38 and 23 nm respectively, at this beam size regime the magnetic field quality of the FFS magnets is a concern. Indeed, the evaluated sy* with the measured multipole components is 100% for the Nominal lattice and 400% for the Ultra-low beta* lattice. The study of the higher order aberrations performed in this thesis is crucial for identifying possible cures that minimise the observed beam size growth. Different solutions have been studied: (i) replacing the FD by better field quality magnets, (ii) swapping the ATF2 quadrupole magnets according to their skew sextupole component and (iii) modifying the lattice optics. The new lattice designs ATF2 Bx2.5By1.0 and ATF2 Ultra-low betay* are based on the prosposed solutions. The impact of the multipoles components is effectively minimsed for both new designs, achieving a sy* equal to 38 and 27 nm ,respectively. The tuning study of the FFS determines its feasibility under realistic error conditions. 100 machines with different initial error configurations are used to address this problem. The tuning simulation study for the alternative CLIC FFS design takes into account BPM resolution, the effect of synchrotron radiation and the misalignment errors of the magnets, being the later a critical parameter on the tuning performance of the system. The motion of the magnetic centre when shunting the quadrupole magnet might represent a limiting factor for further improvement of its alignment. Dedicated measurements at ATF2 have shown a motion of the magnetic centre below 1 micrometre for a shunting variation of 20%. Under this alignment condition the tuning study of the CLIC FFS shows that 80% of the machines reach a L equal or above than L0. The errors included in the tuning study of the ATF2 lattices are misalignments, tilts and miss-powering of the ATF2 FFS magnets. The simulated tuning results show that 80% of the machines reach a final sy* that does not exceed in more than 11% and 35% the design sy* for the ATF2 Bx2.5By1.0 and Ultra-low beta_y* lattices respectively. These results demonstrate the theoretical feasebility of FFS based on the novel chromaticity correction scheme.

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Beam dynamic simulations of the CLIC crab cavity and implications on the BDS

Cited by 2 publications

References 5 publications

Luminosity studies in a traveling waist regime in the Compact Linear Collider

Luminosity studies in a traveling waist regime in the Compact Linear Collider

Design and higher order optimisation of final focus systems for linear colliders

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