Andrea Latina

Halo estimates and simulations for linear colliders

Halo simulations and estimates are important for the design of future linear accelerators. We describe the main processes with analytic estimates and present our generic simulations in application to the ILC.

Wakefield models for particle tracking codes

Wakefields have a considerable effect on beam dynamics and they must not be neglected for emittance growth studies, background estimates and other problems. The codes used for these problems are normally not capable of self-consistent wakefield calculations. They should thus be extended with either analytical models or export the wakefields numerically evaluated with other codes (such as GdfidL) when analytical models are not feasible. Both approaches are presented as well as their implementation in PLACET, MERLIN and BDSIM. The simulation results for the ILC and CLIC beam delivery systems are given as an example. Results produced with different codes are compared.

Collimation optimisation in the beam delivery system of the International Linear Collider

The collimation systems of the International Linear Collider (ILC) Beam Delivery System (BDS) must perform efficient removal of halo particles which lie outside the acceptable ranges of energy and spatial spread. An optimisation strategy based on earlier work is applied to the latest version of the BDS lattice. The resulting improvement in collimation performance is studied by halo tracking simulations, and the luminosity performance of the optimised lattice is also examined.

Dynamic effects during beam-based alignment

Complex beam-based alignment procedures are needed in future linear colliders to reduce the negative effects of static imperfections in the main linac on the beam emittance. The efficiency of these procedures could be affected by dynamic imperfections during their application. In this paper we study the resulting emittance growth.

Emittance preservation in the international linear collider ring to main linac transfer line

The very small vertical beam emittance in the International Linear Collider (ILC) can be degraded by dispersion, xy coupling, transverse wakefields, and time-varying transverse fields introduced by elements with misalignments, strength errors, xy rotation errors, or yz rotation errors in the Ring to Main Linac (RTML) transfer line. We present a plan for emittance preservation in this beamline which uses local, quasi-local, and global correction schemes. Results of simulations of the emittance preservation algorithm are also presented and discussed.

Beam dynamics studies in the CLIC Injector LINAC

The CLIC Injector Linac has to accelerate both electron and positron main beams from 200 MeV up to 2.42 GeV prior to their injection into the pre-damping rings. Its 26 accelerating structures operate at 1.5 GHz, with a loaded gradient of 17 MV/m. A FODO lattice that wraps the accelerating structures at the beginning of the linac, followed by a succession of triplet lattices between the accelerating structures, is proposed. The large normalized transverse emittance (9200 mm.mrad rms), bunch length (5 mm rms) and energy spread (7 MeV rms) of the e+ beam set constraints on the linac, in order to reach acceptable characteristics at 2.42 GeV for the injection into the pre- damping ring. The use of a bunch compressor at the linac entrance is an option in order to achieve good performance in both the longitudinal and transverse phase spaces. Tracking studies of both electron and positron beams in the linac have been performed and are presented.

Bunch compressor for beam-based alignment

Misalignments in the main linac of future linear colliders can lead to significant emittance growth. Beam-based alignment algorithms, such as Dispersion Free Steering (DFS), are necessary to mitigate these effects. We study how to use the bunch compressor to create the off-energy beams necessary to DFS and discuss the effectiveness of this method.

Comparison of ILC fast beam-beam feedback performance in the e - e - and e + e - modes of operation

Several feedback loops are required in the beam delivery system (BDS) of the international linear collider (ILC) to preserve the luminosity in the presence of dynamic imperfections. Realistic simulations have been carried out to study the performance of the beam-beam deflection based fast feedback system, for both e⁺e^- and e^-e^- modes of operation. The beam-beam effects in the e^-e^- collisions make both the luminosity and the deflections more sensitive to offsets at the interaction point (IP) than in the case of the e⁺e^- collisions. This reduces the performance of the feedback system in comparison to the standard e⁺e^- collisions, and may require a different beam parameter optimization.

Tuning of CLIC-Final Focus System 3 TeV Baseline Design Under Static and Dynamic Imperfections

In this paper we present the tuning study of the Compact Linear Collider - Final Focus System (CLIC-FFS) 3 TeV baseline design under static and dynamic imperfections for the first time. The motion of the FFS magnets due to ground motion and the impact of active and passive mechanisms envisaged to stabilize both e − and e + systems are described. It is found that the Pre-isolator required for stabilization of the Final Doublet drives the performance of the collider at the final stages of the tuning process. The obtained tuning performance depending on the stabilization techniques are discussed in detail.