The LHC as a Nucleus-Nucleus Collider

This paper begins with a summary of the status of the Large Hadron Collider at CERN, including the lead-ion injector chain and the plans for the first phases of commissioning and operation with colliding proton beams. In a later phase, the LHC will collide lead nuclei at centre-of-mass energies of 5.5 TeV per colliding nucleon pair. This leap to 28 times beyond what is presently accessible will open up a new regime, not only in the experimental study of nuclear matter, but also in the beam physics of hadron colliders. Ultraperipheral and hadronic interactions of highly-charged beam nuclei will cause beam losses that dominate the luminosity decay and may quench superconducting magnets, setting upper limits on luminosity and stored beam current. Lower limits are set by beam instrumentation. On the other hand, coherent radiation by the nuclear charges should provide natural cooling to overcome intra-beam scattering. As with protons, a flexible, staged approach to full performance will test the limits and make optimal use of scheduled beam time. Submitted to Journal of Physics G, Nuclear Physic

Beam Dynamics at LEP

LEP has proved to be one of the most flexible e+e- colliders built to date. It has operated at various energies, in several modes, with ever increasing demands for luminosity in clean and precisely known beam conditions. Together with some unique features, LEP therefore has much in common with future e+e- factories. Beam-dynamical phenomena have been among the crucial determinants of LEP's performance. These include single-particle dynamics (optics design, dynamic aperture, radiation effects, etc.), a variety of beam-beam effects and collective instabilities. The strategies adopted to overcome these effects and maximise performance will be described with emphasis on those relevant to the design and operation of e+e- factories

Realistic prediction of dynamic aperture and optics performance for LEP

Over the two-decade lifetime of the LEP project, techniques for evaluating the quality of optical configurations have evolved considerably to exploit the growth in computer power and improved modelling of single-particle dynamics. These developments have culminated in a highly automated Monte-Carlo evaluation process whose stages include the generation of an ensemble of imperfect machines, simulation of the operational correction procedures, correlation studies of the optical functions and parameters of (both) beams, 4-dimensional dynamic aperture scans and tracking with quantum fluctuations to determine the beam core distribution. We outline the process, with examples, and explain why each step is necessary to realistically capture essential physics affecting performance. The mechanisms determining the vertical emittance, radial beam distribution and dynamic aperture are especially important. As a storage ring in which an unusual variety of optics have been tested, LEP provides a valuable test case for the predictive power of the methodology

Facilities for the Energy Frontier of Nuclear Physics

The Relativistic Heavy Ion Collider at BNL has been exploring the energy frontier of nuclear physics since 2001. Its performance, flexibility and continued innovative upgrading can sustain its physics output for years to come. Now, the Large Hadron Collider at CERN is about to extend the frontier energy of laboratory nuclear collisions by more than an order of magnitude. In the coming years, its physics reach will evolve towards still higher energy, luminosity and varying collision species, within performance bounds set by accelerator technology and by nuclear physics itself. Complementary high-energy facilities will include fixed-target collisions at the CERN SPS, the FAIR complex at GSI and possible electron-ion colliders based on CEBAF at JLAB, RHIC at BNL or the LHC at CERN.Comment: Invited talk at the International Nuclear Physics Conference, Vancouver, Canada, 4-9 July 2010, to be published in Journal of Physics: Conference Series. http://inpc2010.triumf.ca

The LHC as a Proton-Nucleus Collider

Following its initial operation as a proton-proton (p-p) and heavy-ion (208Pb82+-208Pb82+) collider, the LHC is expected to operate as a p-Pb collider. Later it may collide protons with other lighter nuclei such as 40Ar18+ or 16O8+. We show how the existing proton and lead-ion injector chains may be efficiently operated in tandem to provide these hybrid collisions. The two-in-one magnet design of the LHC main rings imposes different revolution frequencies for the two beams in part of the magnetic cycle. We discuss and evaluate the consequences for beam dynamics and estimate the potential performance of the LHC as a proton-nucleus collider

Phase-space Analysis by Multiple Resonance-Frequency Identification: Applications to the LHC and LEP

Many beam-dynamical phenomena are studied, experimentally or computationally, by means of spectral analysis of a time-series of values of a dynamical variable. When the underlying dynamics is regular, the frequencies appearing in the spectrum are integer combinations of a small set of basic frequencies, e.g., the three tunes in the case of single-particle orbital dynamics. For well-known reasons, identification of the frequencies can be ambiguous or subjective in practice. We present an algorithm that overcomes these difficulties by exploiting theoretical bounds on the spectral power density to transform time series into sets of labelled resonance lines. In our examples, the time series are orbits obtained by tracking single particles from many initial conditions. The method has been applied to off-momentum LHC injection optics. This is a deterministic Hamiltonian system. A second application, to orbits with strong quantum fluctuations in LEP2, shows that it also works well in a noisy, dissipative system

Damping rings for CLIC

The Compact Linear Colider (CLIC) is designed to operate at 3 TeV centre-of-mass energy with a total luminosity of 10^35 cm^-2 s^-1. The overall system design leads to extremely demanding requirements on the bunch trains injected into the main libac at frequency of 100 Hz. In particular, the emittances of the intense bunches have to be about an order of magnitude smaller than presently achieved. We describe our approach to finding a damping ring design capable of meeting these requirements. Besides lattice design, emittance and damping rate considerations, a number of scattering and instability effects have to be incorporated into the optimisation of parameters. Among these, intra-bem scattering and the electron cloud effect are two of the most significant