M. Meddahi

Proton-driven plasma wakefield acceleration: a path to the future of high-energy particle physics

New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN—the AWAKE experiment—has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator.

Cern Neutrinos to Gran Sasso (CNGS): results from commissioning

The CNGS project (CERN Neutrinos to Gran Sasso) aims at directly detecting vmu - vtau oscillations. An intense vmu beam is generated at CERN and directed towards LNGS (Laboratori Nazionali del Gran Sasso) in Italy where vtau will be detected in large and complex detectors. An overview of the CNGS beam facility is given. Results from the primary and secondary beam line commissioning performed in summer 2006 are presented. Measurements of proton beam parameters are compared with expectations.

Injection and lessons for 2012

Injection of 144 bunches into the LHC became fully operational during the 2011 run and one nominal injection of 288 bunches was accomplished. Several mitigation solutions were put in place to minimise losses from the Transfer Line (TL) collimators and losses from kicking debunched beam during injection. Nevertheless, shotby-shot and bunch-by-bunch trajectory variations, as well as long terms drifts, were observed and required a regular resteering of the TL implying a non negligible amount of time spent for injection setup. Likely sources of instability have been identified (i.e. MKE and MSE ripples) and possible cures to optimise 2012 operation are presented. Well defined references for TL steering will be defined in a more rigorous way in order to allow a more straightforward and faster injection setup. Encountered and potential issues of the injection system, in particular the injection kickers MKI, are discussed also in view of injections with a higher number of bunches.

Can the proton injectors meet the HL-LHC requirements after LS2?

The LIU project has as mandate the upgrade of the LHC injector chain to match the requirements of HLLHC. The present planning assumes that the upgrade work will be completed in LS2, for commissioning in the following operational year. The known limitations in the different injectors are described, together with the various upgrades planned to improve the performance. The expected performance reach after the upgrade with 25 and 50 ns beams is examined. The project planning is discussed in view of the present LS1 and LS2 planning. The main unresolved questions and associated decision points are presented, and the key issues to be addressed by the end of 2012 are detailed in the context of the machine development programs and hardware construction activities. HL-LHC REQUIREMENTS AFTER LS2 The stated performance objective of HL-LHC is to accumulate 3000 fb of integrated p-p luminosity at 14 TeV centre of mass collision energy [1]. In order to achieve this, an annual figure of 250-300 fb has been posited, requiring instantaneous luminosity capability of around 7–8×10 cms, levelling to 5×10 cms and high machine efficiency [2]. The present paper covers the first of these challenging requirements: how to deliver the beam from the injector complex for these luminosities almost an order of magnitude above LHC design. The HL-LHC project has previously outlined possible parameter sets for 25 and 50 ns spacing which give the required luminosity, summarised in Tab. 1, adapted from [2]. Strictly speaking the HL-LHC needs the specified beams from the SPS after LS3, when the major work for the HL-LHC project is planned. The LIU work will take place largely in LS2, so that the period LS2 to LS3 will be an important one in terms of achieving the maximum performance from the injector chain. The figures quoted are for beams at the start of the collision process at 7 TeV – any beam loss or emittance dilution after extraction from the SPS is not included. The assumptions on the beam loss and emittance dilution for all machines are given in Tab. 2, where it can be seen that the total assumed beamloss -ΔI/I0 is 27%, and the emittance growth Δε/ε0 is 33%, corresponding to a brightness which is reduced to 55% of the original value. Table 1: Parameters and requirements from HL-LHC Parameter Nom. HL 25 ns HL 50 ns N [e11 p+] 1.15 2.0 3.3

High intensity commissioning of SPS LSS4 extraction for CNGS

The SPS LSS4 fast extraction system will serve both the anti-clockwise ring of the LHC and the CERN Gran Sasso Neutrino project (CNGS). CNGS requires 2 fast extractions of 10.5 microsecond long batches, 50 milliseconds apart. Each batch will consist of 2.4 times 1013 protons at 400 GeV. These intensities are factor of 10 above the equipment damage limit in case of beam loss. Active (interlock system) and passive protection systems have to be in place to guarantee safe operation and to respect the radiation limits in zones close to the extraction region. In summer 2006 CNGS was commissioned including extraction with high intensity. A thorough setting-up of the CNGS extraction was carried out as part of the CNGS commissioning, including aperture and beam loss measurements, and defining and checking of interlock thresholds for extraction trajectory, beam loss monitors and radiation monitors. The relevant systems and risks are introduced in this paper, the commissioning results are summarised and comparisons with simulation predictions are presented.

Injection and dump considerations for a 16.5 TeV HE-LHC

Injection and beam dumping is considered for a 16.5 TeV hadron accelerator in the current LHC tunnel, with an injection energy in the range 1 - 1.3 TeV. The present systems are described and the possible upgrade scenarios investigated for higher beam rigidity. In addition to the required equipment performance, the machine protection related aspects are explored. The expected constraints on the machine layout are also given. The technological challenges for the different equipment subsystems are detailed, and areas where R&D is necessary are highlighted.

First Operational Experience Of The CNGS Facility

The CNGS project (CERN Neutrinos to Gran Sasso) aims at directly detecting νμ−ντ oscillation. An intense muon‐neutrino beam (1017νμ/day) is generated at CERN and directed towards the Gran Sasso National Laboratory, LNGS, in Italy, where the ντ will be detected in large and complex detectors. An overview of the CNGS beam facility is given. The performance of the primary and secondary beam line during beam commissioning and physics operation is discussed. Modifications on the magnetic focusing lenses (horn and reflector) are described.