Elias Métral

THE STUDY OF A EUROPEAN NEUTRINO FACTORY COMPLEX

The Neutrino Factory is a new concept for an accelerator that produces a high-intensity, high-energy beam of electron and muon neutrinos – the ultimate tool for neutrino oscillation studies and the only machine conceived up today that could help detect CP violation of leptons. The basic concept of the Neutrino Factory is the production of neutrinos from the decay of high-energy muons. Due to their short lifetime, these muons have to be accelerated very fast. Several new accelerator techniques, like a high-intenstiy proton linac, high-power targets, ionization cooling or recirculating muon linacs are required. This paper presents a snapshot of the accelerator design at CERN. Although some aspects of this European Neutrino Factory Scheme have been optimised for the CERN site, the basic principle is siteindependent.

COLLECTIVE EFFECTS IN THE CERN-PS BEAM FOR LHC

This paper is an updated review of the collective effects observed and predicted in the CERN-PS machine for the LHC beam.

Beam Instabilities in Hadron Synchrotrons

Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

Long Term Simulations of Space Charge and Beam Loss Observed in the CERN Proton Synchrotron

Long term storage of high intensity beams with small loss is required in the FAIR project at GSI as well as for JPARC. In this paper we discuss that an important contribution to the loss in bunched beams can be explained it terms of particles trapped into lattice and space charge driven islands. Dedicated experiments at the CERN‐Proton Synchrotron to confirm the theoretical model have shown the existence of an emittance growth dominated regime for working points sufficiently far from the lattice resonance, and of a beam loss dominated regime for tunes very close to the resonance. While the emittance growth dominated regime has been investigated in previous studies, we focus here on the beam loss dominated regime and compare simulation results with measurements made in the CERN‐Proton Synchrotron ring.

High Luminosity LHC: Challenges and plans

The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will undergo a major upgrade in the 2020s. This will increase its rate of collisions by a factor of five beyond the original design value and the integrated luminosity by a factor ten. The new configuration, known as High Luminosity LHC (HL-LHC), will rely on a number of key innovations that push accelerator technology beyond its present limits. Among these are cutting-edge 11–12 T superconducting magnets, including Nb3Sn-based magnets never used in accelerators before, compact superconducting cavities for longitudinal beam rotation, new technology and physical processes for beam collimation. The dynamics of the HL-LHC beams will be also particularly challenging and this aspect is the main focus of this paper.

Fifty years of the CERN Proton Synchrotron : Volume 2

This report sums up in two volumes the first 50 years of operation of the CERN Proton Synchrotron. After an introduction on the genesis of the machine, and a description of its magnet and powering systems, the first volume focuses on some of the many innovations in accelerator physics and instrumentation that it has pioneered, such as transition crossing, RF gymnastics, extractions, phase space tomography, or transverse emittance measurement by wire scanners. The second volume describes the other machines in the PS complex: the proton linear accelerators, the PS Booster, the LEP pre-injector, the heavy-ion linac and accumulator, and the antiproton rings.

Collective effects and final bunch rotation in a 2.2 GeV–44 MHz proton accumulator–compressor for a neutrino factory

This paper is a review of the collective effects and the final bunch rotation in the CERN scenario of a 4 MW proton driver for a neutrino factory.

Expected Impact of Hardware Changes on Impedance and Beam-induced Heating during Run 2

Following the significant impedance related issues that occurred during the LHC Run 1, all involved equipment groups made an impressive effort to assess and reduce the impedance of their near-beam components. Concerning beam induced RF heating, many problems in Run 1 were linked to unexpected non-conformities. Mitigations were put in place but new non-conformities are likely to appear in Run 2, and this is why efficient monitoring and alarms are currently put in place. Besides, known limitations that led to increase the bunch ength from 1 ns to 1.25 ns were removed, which would open the possibility to try and reduce the target bunch length at top energy. Regardless of the target bunch length, many components will need careful follow up in 2015 (e.g. TDI, BSRT, Roman pots, MKI, BGV). Concerning the LHC impedance, announced hardware changes are expected to be transparent, but the new TCTP and TCSP collimators with BPMs and ferrites should be monitored closely, as well as the modified Roman pots, new TCL4 and especially new TCL6 collimators if they approach the beam with very low gaps at high beam intensity.

JACoW : Simulation and Measurement of the TMCI Threshold in the LHC

The Transverse Mode Coupling Instability (TMCI) occurs in individual bunches when two transverse oscillation modes couple at high bunch intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3 · 1011 protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch regime, at low chromaticities.

Some Effects Near Transition

This paper discusses some general longitudinal and transverse beam dynamics effects that occur near the transition energy and when it is crossed, with application to the particular cases of the CERN Proton Synchrotron and Super Proton Synchrotron machines.