Optics options for the 2015 LHC run

A review of the possible optics configurations for the 2015 LHC run will be made. The rationale behind the various scenarios will also be presented together with the latest results of the validation studies. Special runs, such as Van der Meer and high-beta, will be discussed too. Finally, the next steps and the related milestones will be discussed with the goal of achieving a consensual decision on the optics configuration to be used for the LHC in the coming weeks

Implementation of the proposed multi-turn extraction at the CERN Proton Synchrotron

Following the positive results of the three-year measurement campaign at the CERN Proton Synchrotron, concerning beam splitting with stable islands in the transverse phase space, a study of a possible implementation of the proposed Multi-Turn Extraction (MTE) was undertaken. The novel approach would allow a substantial reduction of beam losses, with respect to the present scheme, when delivering the high-intensity proton beams required for the planned CERN Neutrino to Gran Sasso Project (CNGS). Major modifications to the ring layout are foreseen, such as a new design of the extraction bumps including also the installation of three additional kickers to create a closed-bump over the five turns used to extract the split beam. The ring aperture was reviewed and improvements proposed to reduce possible beam losses during beam splitting and extraction. The goal consists of implementing the proposed changes by the end of the 2007/2008 PS shutdown and to commission the novel extraction during the 2008 physics run

Evaluation of the Dynamic Aperture of the CERN-LHC using Fast Indications of Long Term Stability

The dynamic of the particles in the CERN-LHC is largely dominated by the unavoidable magnetic errors of the superconducting magnets used to guide the particles along the 27km long circumference. Due to that, the volume of the phase space wherestable motion occurs shrinks, hence reducing dramatically the performance of the accelerator. We willfirst introduce the concept of thedynamic aperture, reviwing theoretical and computational issues. Different methods for a fast and accurate estimate of this quantity are discussed and compared. After that, the issueof finding effective fast indicators of the long term stability of the particle motion is discussed in detail. Dynamical quantities, like the variation with time of the instantaneous betatron frequency (tune) and the maximal value of the Lyapunov exponent are presented and used to detect the onset of chaotic motion. Their predictivity is extensively checked with the classical element-by-element computer tracking simulations over many turns. Advanced methods and large computational resources are required to achieve in a positive manner this ambitious goal

Computation of the Dynamic Aperture of 2D Generic Maps Using Invariant Manifolds

In this paper the phase-space of generic 2D area-preserving polynomial mappings is studied. These mappings modelize the transverse dynamics of a flat beam in a circular machine dominated by non-linear magnetic errors. In particular, the problem of computing the dynamic aperture, i.e., the region in phase-space where stable motion occurs, is considered. The main result is that the boundary of the stability domain is given by the invariant manifolds emanating from the outermost unstable fixed point of low period (one or two). This study extends previous results obtained for reversible area-preserving polynomial maps of the plane

Design and Tests of a Low-Loss Multi-Turn Ejector for the CERN PS

Following the positive results of a three-year measurement campaign at the CERN Proton Synchrotron, a study of a possible implementation of the proposed Multi-Turn Extraction (MTE) based on beam splitting with stable islands in the transverse phase space was undertaken. A substantial reduction of beam losses, with respect to the present extraction scheme, could be achieved with the proposed technique when delivering the high-intensity proton beams required for the planned CERN Neutrino to Gran Sasso Project. Major modifications to the ring layout are needed, such as a new design of the extraction bumps including also the installation of three additional kickers to create a closed-bump over the five turns used to extract the split beam. The ring aperture was reviewed and improvements are proposed to reduce possible beam losses between beam splitting and extraction. The goal is to implement the proposed changes by beginning of 2008 and to commission the novel extraction during the 2008 PS physics run

Study of the dynamic aperture of the 4D quadratic map using invariant manifolds

A 4D quadratic map can be used to represent the transfer map of a FODO cell with a sextupolar nonlinearity in the kick approximation. This map describes the transverse betatronic motion of a charged p article in a circular accelerator. The dynamic aperture of such a mapping is analysed, i.e., the domain in phase space where stable motion occurs, as a function of the linear tunes. Starting from the study of the stability properties of the fixed points of low period (one or two), it is shown that the dynamic aperture is related to the invariant manifolds emanating from unstalbe points. This repre nsets a generalisation of a similar result obtained for generic two-dimensional sympletic maps

Space-charge simulations using parallel algorithms

The evaluation of the space-charge effects on the beam dynamics requires CPU-time intensive numerical simulations. To obtain accurate results it is necessary to consider a distribution of particles an d to track them through the magnetic lattice. To reduce the real time needed by the simulations, a possible solution is to develop parallel algorithms. In this was, the computational burden can be dis tributed over many CPUs thus reducing the time to obtain results. In this paper parallel techniques to simulate space-charge effects are presented ; in particular we investigate the over-all performan ce of the algorithm and its scalability