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The RF system is the centrepiece of any future circular lepton collider. In particular, the system is required to support the high intensity beams needed for pushing the luminosity at the lower energy regimes of future energy-frontier circular lepton colliders (e.g. for operation in the Z peak and at the WW threshold). Capturing, storing the beam and replacing energy losses from synchrotron radiation demand low frequency, low shunt resistance cavities, low number of cells and high RF power per cell. Controlling the beam both transversely and longitudinally requires sophisticated beam control and timing systems. Additional RF systems are used to ensure transverse stability (feedback systems) and to increase the luminosity (crab cavities). Operation at high energies (such as the ZH and ${\mathrm{t}{\overline{\mathrm{t}}}}$ threshold) requires a very large accelerating voltage, since synchrotron radiation leads to significantly higher energy losses per turn which must be compensated. Since the RF system is to be optimised in size and energy efficiency for varying demands for the different operational modes, the spectrum of R&D; challenges covers a wide range of technologies.

The HL-LHC beams are injected, accelerated, and stored to their nominal energy of 7 TeV by the existing 400 MHz superconducting RF system of the LHC. A novel superconducting RF system consisting of eight cavities per beam for transverse deflection (aka crab cavities) of the bunches will be used to compensate the geometric loss in luminosity due to the non-zero crossing angle and the extreme focusing of the bunches in the HL-LHC. Due to doubling of the beam currents in the HL-LHC era, an optimal detuning scheme (aka full- detuning) is required to cope with the transient beam loading effects. A modulation of the klystron and cavity phase make the phase of bunches with respect to the RF clock to progressively slip along the bunch train, but then recover during the abort gap. With this scheme the klystron power is independent of the beam current and maintained constant over one full turn at the expense of bunch-to-bunch phase modulation. This scheme was experimentally tested in 2016 and operational since then in the LHC during the acceleration ramp and flat-top. During injection of the HL-LHC beams from the SPS in to the LHC, the original half-detuning scheme to strictly preserve the bunch-to-bunch spacing is a pre-requisite. The total available voltage with HL-LHC beams is therefore limited to approximately 6 MV with the available RF power at injection. Second harmonic RF system at 800 MHz for Landau damping and lower frequency accelerating RF system at 200 MHz in conjunction with the exiting 400 MHz cavities for improved capture from the SPS for intense and longer bunches were studied but are no longer considered for the HL-LHC.

The Beams Department hosts the Groups responsible for the beam generation, acceleration, diagnostics, controls and performance optimization for the whole CERN accelerator complex. This Report describes the 2018 highlights for the BE Department.

PERLE is a proposed high power Energy Recovery Linac, designed on multi-turn configuration, based on SRF technology, to be hosted at Orsay-France in a col-laborative effort between local laboratories: LAL and IPNO, together with an international collaboration involv-ing today: CERN, JLAB, STFC ASTeC Daresbury, Liverpool University and BINP Novosibirsk. PERLE will be a unique leading edge facility designed to push advances in accelerator technology, to provide intense and highly flexible test beams for component development. In its final configuration, PERLE provides a 500 MeV elec-tron beam using high current (20 mA) acceleration during three passes through 801.6 MHz cavities. This presenta-tion outlines the technological choices, the lattice design and the main component descriptions., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

This report discusses the feasibility and limitations for operating the LHC and HL-LHC at the ultimate beam energy of 7.5 TeV, corresponding to a main dipole magnetic field of 8.93 T and an operating current of 12748 A.

The European Particle Physics Strategy Update (EPPSU) process takes a bottom-up approach, whereby the community is first invited to submit proposals (also called inputs) for projects that it would like to see realised in the near-term, mid-term and longer-term future. National inputs as well as inputs from National Laboratories are also an important element of the process. All these inputs are then reviewed by the Physics Preparatory Group (PPG), whose role is to organize a Symposium around the submitted ideas and to prepare a community discussion on the importance and merits of the various proposals. The results of these discussions are then concisely summarised in this Briefing Book, prepared by the Conveners, assisted by Scientific Secretaries, and with further contributions provided by the Contributors listed on the title page. This constitutes the basis for the considerations of the European Strategy Group (ESG), consisting of scientific delegates from CERN Member States, Associate Member States, directors of major European laboratories, representatives of various European organizations as well as invitees from outside the European Community. The ESG has the mission to formulate the European Strategy Update for the consideration and approval of the CERN Council. The European Particle Physics Strategy Update (EPPSU) process takes a bottom-up approach, whereby the community is first invited to submit proposals (also called inputs) for projects that it would like to see realised in the near-term, mid-term and longer-term future. National inputs as well as inputs from National Laboratories are also an important element of the process. All these inputs are then reviewed by the Physics Preparatory Group (PPG), whose role is to organize a Symposium around the submitted ideas and to prepare a community discussion on the importance and merits of the various proposals. The results of these discussions are then concisely summarised in this Briefing Book, prepared by the Conveners, assisted by Scientific Secretaries, and with further contributions provided by the Contributors listed on the title page. This constitutes the basis for the considerations of the European Strategy Group (ESG), consisting of scientific delegates from CERN Member States, Associate Member States, directors of major European laboratories, representatives of various European organizations as well as invitees from outside the European Community. The ESG has the mission to formulate the European Strategy Update for the consideration and approval of the CERN Council.

The Beams Department hosts the Groups responsible for the beam generation, acceleration, diagnostics, controls and performance optimization for the whole CERN accelerator complex. This Report describes the 2017 highlights for the BE Department.

PERLE (Powerful ERL for Experiments) is a novel ERL test facility, initially proposed to validate choices for a 60 GeV ERL foreseen in the design of the LHeC and the FCC-eh. Its main thrust is to probe high current, CW, multi-pass operation with superconducting cavities at 802 MHz (and perhaps testing other frequencies of interest). With very high virtual beam power (~ 10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERL design; becoming a ‘stepping stone' between present state-of-art 1 MW ERLs and future 100 MW scale applications. PERLE design features Flexible Momentum Compaction lattice architecture for six vertically stacked return arcs and a high-current, 6 MeV, photo-injector. With only one pair of 4 cavity cryomodules, 400 MeV beam energy can be reached in 3 re-circulation passes, with beam currents in excess of 15 mA. The beam is decelerated in 3 consecutive passes back to the injection energy, transferring virtually stored energy back to the RF. This unique facility will serve as a test-bed for high current ERL technologies, as well as a user facility in low energy electron and photon physics., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Particle accelerators are precious tools, not only for high-energy and nuclear physics, but also for many other areas of science, medicine, and security. They do, however, have a substantial energy consumption, which makes it important to design them to make best use of the consumed energy. Maximizing the energy efficiency of an accelerator means minimizing not only the energy consumption and the environmental impact, but also allowing for smaller installations. The concepts and technologies developed to improve the energy efficiency of particle accelerators are not limited to accelerators, but will have a significant impact on energy systems generally. These developments include smart power grids and short-term energy storage devices, better energy conversion efficiencies for subsystems, efficient cryogenic systems, and, ultimately, the recovery of unused energy in more valuable forms than low-temperature heat. Energy recovery linacs are the prime example for good efficiency, since they accelerate, use, and decelerate a continuous beam, using the energy recovered during deceleration for acceleration., CERN Yellow Reports: School Proceedings, Vol 1 (2018): Proceedings of the CAS-CERN Accelerator School on Free Electron Lasers and Energy Recovery Linacs

The Beams Department hosts the Groups responsible for the beam generation, acceleration, diagnostics, controls and performance optimization for the whole CERN accelerator complex. This Report describes the 2016 highlights for the BE Department.

This is the first report of a three volume study on the full energy exploitation of the LHC. The report summaries the necessary preparations and consolidation work and the potential performance reach for operating the LHC at its nominal beam energy of 7TeV.

This talk tries an overview of recent developments in RF sources for linear accelerators of different scales and for various applications, spanning a frequency range from about 100 MHz to X-band, spanning duty factors from about 10⁻³ to CW, and spanning power levels from a few kW up to hundreds of MW average. Exciting recent trends include new bunching concepts for klystrons promising a significant increase of efficiency and better power combiners paving the way to MW-class solid state power amplifiers., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

Over a two-day period, March 8-9, 2017 the Office of High Energy Physics convened a workshop in Gaithersburg, MD to seek community input on development of a radiofrequency (RF) research ten-year roadmap to guide the General Accelerator Research and Development Program (GARD). As described in the charge, the roadmap should reflect the Particle Physics Project Prioritization Panel strategy and the subsequent HEPAP Accelerator Subpanel recommendations. The charge for the workshop can be found in Appendix A. At the workshop, proponents of superconducting radiofrequency technology (SRF) and normal conducting radiofrequency technology (NCRF), along with invited university and laboratory experts, critically discussed opportunities, gaps, and requirements relevant to the development of a roadmap. The roadmap workshop was preceded by preparatory workshops at SLAC on NCRF and Fermilab on SRF.

The Beams Department hosts the Groups responsible for the beam generation, acceleration, diagnostics, controls and performance optimization for the whole CERN accelerator complex. This Report describes the 2015 highlights for the BE Department.

We present a first rough estimate for the electrical power consumption of the FCC-ee lepton collider. This electrical power is dominated by the RF system, which provides the motivation for the ongoing R&D on highly efficient RF power sources. Other contributions come from the warm arc magnets, the cryogenics systems, cooling, ventilation, general services, the particle-physics detectors, and the injector complex., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The Beams Department hosts the Groups responsible for the beam generation, acceleration, diagnostics, controls and performance optimization for the whole CERN accelerator complex. This Report describes the 2014 highlights for the BE Department.

FCC-ee is a proposed high-energy electron positron circular collider that would initially occupy the 100-km FCC tunnel that will eventually house the 100 TeV FCC-hh hadron collider. The parameter range for the e⁺/e⁻ collider is large, operating at a cm energy from 90 GeV (Z-pole) to 350 GeV (t-tbar production) with the maximum beam current ranging from 1.5 A to 6 mA for each beam, corresponding to a synchrotron radiation power of 50 MW and a radiative energy loss varying from ~30 MeV/turn to ~7500 MeV/turn. This presents challenges for the rf system due to the varying rf voltage requirements and beam loading conditions. In this paper we present a possible gradual evolution of the FCC-ee complex by step-wise expansion, and possibly reconfiguration, of the superconducting RF system. The performance attainable at each step is discussed, along with the possible advantages and drawbacks., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The future circular colliders (FCC) will require superconducting RF systems for the proton-proton, electron-positron and lepton-hadron modes of the collider operation. The SCRF systems will accelerate the protons beams to 50 TeV and the lepton beams from 45.5 to 175 GeV in a staged approach with a possible 60 GeV energy recovery linac for the lepton-hadron to option as an intermediate step. The expected stored beam currents in some modes exceed 1 A with very short bunch lengths. A first conceptual design of the FCC RF system is proposed along with highlights of specfic R&D topics to reach the design performance. Challenges related to RF structure design, intensity limitations due to beam loading, RF powering and higher order modes are addressed. Synergies between the different collider modes and the present LHC are identified., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

New particle accelerator based research facilities tend to be much more productive, but often in coincidence with much higher energy consumption. The total energy consumption of mankind is steeply rising, while some European countries decided to terminate nuclear power generation and to switch to renewable energy production. Also the CO2 problem gives rise to new approaches for energy production and in all strategies the efficiency of utilization of electrical energy plays an important role. For the public acceptance of particle accelerator projects it is thus very important to optimize them for best utilization of electrical energy and to show these efforts to funding bodies and to the public. Within the European accelerator development program Eucard-2 we organise a network EnEfficient that aims at improving the energy efficiency of accelerators. In this paper we give some background information on the political situation, we describe the power flow in accelerator facilities and we give examples for developments of efficient accelerator systems, such as magnets, RF generation and beam acceleration, heat recovery and energy management., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Place holder for possible Plenary Paper upload…, Proceedings of the 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, ERL2015, Stony Brook, NY, USA

EuCARD² is an Integrating Activity Project for coordinated Research and Development on Particle Accelerators, co-funded by the European Commission under the FP7 Capacities Programme. Within the network EnEfficient we address topics around energy efficiency of research accelerators. The ambitious scientific research goals of modern accelerator facilities lead to high requirements in beam power and beam quality for those research accelerators. In conjunction with the user’s needs the power consumption and environmental impact of the research facilities becomes a major factor in the perception of both funding agencies and the general public. In this Network we combine and focus the R&D done individually at different research centers into a series of workshops. We cover the topics “Energy recovery from cooling circuits “, “Higher electronic efficiency RF power generation“, “Short term energy storage systems”, “Virtual power plants” and “Beam transfer channels with low power consumption”. Our network activities are naturally open to external participants. With this work we will introduce our energy efficiency topics to interested participants and contributors from the whole community., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The baseline electron accelerator for LHeC and one option for FCC-he is an Energy Recovery Linac. To prepare and study the necessary key technologies, CERN has started – in collaboration with JLAB and Mainz University – the conceptual design of an ERL Test Facility (ERL-TF). Staged construction will allow the study under different conditions with up to 3 passes, beam energies of up to about 1 GeV and currents of up to 50 mA. The design and development of superconducting cavity modules, including coupler and HOM damper designs, are also of central importance for other existing and future accelerators and their tests are at the heart of the current ERL-TF goals. The ERL-TF could also provide a unique infrastructure for several applications that go beyond developing and testing the ERL technology at CERN. In addition to experimental studies of beam dynamics, operational and reliability issues in an ERL, it could equally serve for quench tests of superconducting magnets, as physics experimental facility on its own right or as test stand for detector developments. This contribution will describe the goals and the concept of the facility and the status of the R&D;.

The modern concept of an Energy Recovery Linac allows providing large electron currents at large beam energy with low power consumption. This concept is used in FEL’s, electron-ion colliders and electron coolers. CERN has started a Design Study of an ERL Test Facility with the purpose of 1) studying the ERL principle, its specific beam dynamics and operational issues, as relevant for LHeC, 2) providing a test bed for superconducting cavity modules, cryogenics and integration, 3) studying beam induced quenches in superconducting magnets and protection methods, 4) providing test beams for detector R&D and other applications. It will be complementary to existing or planned facilities and is fostering international collaboration. The operating frequency of 802 MHz was chosen for performance and for optimum synergy with SPS and LHC; the design of the cryomodule has started. The ERL Test Facility can be constructed in stages from initially 150 MeV to ultimately 1 GeV in 3 passes, with beam currents of up to 80 mA. Parameters to serve the above-mentioned purposes are well defined and possible lattice designs have well advanced., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The High luminosity upgrade to the LHC (HL-LHC) calls for crab cavities to reduce the luminosity loss due to the crossing angle and help provide luminosity levelling. The 4 Rod Crab Cavity (4RCC) is one of three proposed options under consideration. A bare cavity has been prototyped and has undergone recent vertical tests and the results are presented. The dressed cavity includes a power coupler, a lower order mode coupler and two HOM couplers will be presented and discussed., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

For the special requirements related to particle accelerators, knowledge of the different material parameters of dielectrics and other materials are needed in order to carry out simulations during the design process of accelerator components. This includes also properties of magnetically biased ferrites of which usually little information is available about material characteristics, especially in magnetic bias fields. Several methods of measurement are discussed and compared of which some require delicate sample preparation whereas others can work with unmodified material shapes that makes those methods also suited for acceptance checks on incoming materials delivered by industry. Applications include characterization of different materials, as absorbers in which dielectric losses play an increasing role, as well as low frequency measurements on ferrites that are used for tunable cavities. We present results obtained from both broadband and resonant measurements on different materials determined in the same sample holder. Where possible, the results were confirmed with alternative methods., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Travelling structures for accelerating the high-current (4.2 A) CLIC Drive Beam to an energy of 2.37 GeV are presented. The structures are optimised for efficiency (full beam loading operation) and a desired filling time. Higher order modes are studied and are reduced by detuning along the structure and by damping with silicon carbide loads.

An efficient RF to beam energy transfer in the accelerating structures of the drive beam is one of the key points of the Compact Linear Collider (CLIC) RF power source. For this, the structures are fully beam-loaded, i.e. the accelerating gradient is nearly zero at the downstream end of each structure. In this way, about 96 % of the RF energy can be transferred to the beam. To demonstrate this mode of operation, 1.5 ..s long beam pulses are accelerated in six fully loaded structures in the CLIC Test Facility (CTF3) Linac. The final beam energy is compared to the input RF power of the structures, proving the efficient energy transfer.

This note presents the CLIC parameter set as of mid 2005 and describes the different sub-systems, stressing how the design of the different components is driven. This design emerged from a better understanding of limitations for normal conducting accelerating structures, which led to a new optimised design for the CLIC 30 GHz accelerating structure. The structure parameters and improvements in other sub-systems have resulted in a major revision of the parameters. The overall layout and efciencies for CLIC with this updated parameter-set are presented.

The Beta-Beam is a concept of large-scale facility that aims at providing pure electronic neutrino and antineutrino beams for the measurement of electron and muon neutrino oscillations. Beta-decaying nuclides are produced in large amounts in a facility of the scale of EURISOL, and are then post-accelerated and stored at large gamma in a racetrack decay ring. We present here a conceptual design of the accelerator chain of a Beta-Beam based at CERN.

The European Particle Physics Strategy Update (EPPSU) process takes a bottom-up approach, whereby the community is first invited to submit proposals (also called inputs) for projects that it would like to see realised in the near-term, mid-term and longer-term future. National inputs as well as inputs from National Laboratories are also an important element of the process. All these inputs are then reviewed by the Physics Preparatory Group (PPG), whose role is to organize a Symposium around the submitted ideas and to prepare a community discussion on the importance and merits of the various proposals. The results of these discussions are then concisely summarised in this Briefing Book, prepared by the Conveners, assisted by Scientific Secretaries, and with further contributions provided by the Contributors listed on the title page. This constitutes the basis for the considerations of the European Strategy Group (ESG), consisting of scientific delegates from CERN Member States, Associate Member States, directors of major European laboratories, representatives of various European organizations as well as invitees from outside the European Community. The ESG has the mission to formulate the European Strategy Update for the consideration and approval of the CERN Council., 254 p. Revised version (10 January 2020): Update of the Physics Briefing Book for the European Strategy for Particle Physics, to take account of comments received from the community, in time for the strategy drafting session that will take place in Bad Honnef (Germany) on 20-24 January 2020

The physics experiments at CLIC will require that the machine scans lower than nominal centre-of-mass energy. We present different options to achieve this and discuss the implications for luminosity and the machine design., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Le présent rapport résume la méthode adoptée par le groupe de l’étude FCC pour élaborer un scénario d’emplacement équilibré selon les trois piliers du projet 1) l’excellence scientifique, 2) la compatibilité territoriale et 3) les risques liés à la mise en œuvre du projet. Il décrit les exigences et les contraintes du processus d’élaboration d’un scénario et illustre par des exemples concrets la manière dont elles sont prises en compte lors de la détermination de la configuration et de l’emplacement. Le présent rapport montre également l’évolution du scénario étudié, entre le début de l’étude exploratoire en 2014 et la proposition d’un scénario de base pour l’emplacement en 2021. Ce scénario optimisé servira de référence pour approfondir les diverses composantes de l’étude de faisabilité (par exemple, études de la stabilité souterraine, propositions d’accès au site pendant les phases de construction et d’exploitation, scénarios pour la fourniture d’électricité et d’eau, approches pour la gestion des matériaux excavés, développement de potentiels de synergie locale, questions d’intégration paysagère, propositions de mesures d’accompagnement et de compensation). Après huit années de travaux d’étude par une équipe multidisciplinaire d'environ 100 membres, il apparaît que le scénario le plus équilibré est celui d’un collisionneur circulaire d’une circonférence de l’ordre de 91 km, comprenant huit sites de surface. Le processus d’élaboration itératif des scénarios est documenté dans le présent document. L’existence d’une communauté d’utilisateurs suffisamment importante s’engageant à exploiter l’infrastructure pendant plusieurs décennies est une condition préalable pour justifier une telle infrastructure de recherche. Les scénarios prévoyant un collisionneur nettement plus petit, c’est-à-dire d’une circonférence inférieure à 90 km, ne répondent pas aux exigences de performance d’un tel programme de recherche devant attirer une masse critique de scientifiques. Les propositions d’emplacement territorial adapté à des scénarios prévoyant un collisionneur d’une circonférence nettement supérieure à 91 km et comprenant plus de huit sites de surface se heurtent à des impossibilités de compatibilité territoriale et risques de réalisiation. Enfin, seules deux classes de configuration et d’emplacement avec un ensemble très limité de scénarios entrent dans le périmètre des limites de faisabilité géologique : entre 89 à 91 km avec huit sites de surface et entre 97 et 98 km avec douze sites de surface. À ce jour, seuls des scénarios à 91 km et huit sites de surface semblent pouvoir satisfaire aux trois exigences suivantes: performances scientifiques acceptables, compatibilité avec les contraintes territoriales et compatibilité avec les contraintes géologiques et techniques. On verra ici que l’un des scénarios (PA31), se détache, sur la base d’une analyse multicritères. Il est retenu pour des études approfondies qui nécessitent des activités sur place, des échanges étroites avec des services compétents dans les deux États Hôtes et avec les parties prenantes dans le périmètre de l'implantation.

Le présent rapport résume la méthode adoptée par le groupe de l’étude FCC pour élaborer un scénario d’emplacement équilibré selon les trois piliers du projet 1) l’excellence scientifique, 2) la compatibilité territoriale et 3) les risques liés à la mise en œuvre du projet. Il décrit les exigences et les contraintes du processus d’élaboration d’un scénario et illustre par des exemples concrets la manière dont elles sont prises en compte lors de la détermination de la configuration et de l’emplacement. Le présent rapport montre également l’évolution du scénario étudié, entre le début de l’étude exploratoire en 2014 et la proposition d’un scénario de base pour l’emplacement en 2021. Ce scénario optimisé servira de référence pour approfondir les diverses composantes de l’étude de faisabilité (par exemple, études de la stabilité souterraine, propositions d’accès au site pendant les phases de construction et d’exploitation, scénarios pour la fourniture d’électricité et d’eau, approches pour la gestion des matériaux excavés, développement de potentiels de synergie locale, questions d’intégration paysagère, propositions de mesures d’accompagnement et de compensation). Après huit années de travaux d’étude par une équipe multidisciplinaire d'environ 100 membres, il apparaît que le scénario le plus équilibré est celui d’un collisionneur circulaire d’une circonférence de l’ordre de 91 km, comprenant huit sites de surface. Le processus d’élaboration itératif des scénarios est documenté dans le présent document. L’existence d’une communauté d’utilisateurs suffisamment importante s’engageant à exploiter l’infrastructure pendant plusieurs décennies est une condition préalable pour justifier une telle infrastructure de recherche. Les scénarios prévoyant un collisionneur nettement plus petit, c’est-à-dire d’une circonférence inférieure à 90 km, ne répondent pas aux exigences de performance d’un tel programme de recherche devant attirer une masse critique de scientifiques. Les propositions d’emplacement territorial adapté à des scénarios prévoyant un collisionneur d’une circonférence nettement supérieure à 91 km et comprenant plus de huit sites de surface se heurtent à des impossibilités de compatibilité territoriale et risques de réalisiation. Enfin, seules deux classes de configuration et d’emplacement avec un ensemble très limité de scénarios entrent dans le périmètre des limites de faisabilité géologique : entre 89 à 91 km avec huit sites de surface et entre 97 et 98 km avec douze sites de surface. À ce jour, seuls des scénarios à 91 km et huit sites de surface semblent pouvoir satisfaire aux trois exigences suivantes: performances scientifiques acceptables, compatibilité avec les contraintes territoriales et compatibilité avec les contraintes géologiques et techniques. On verra ici que l’un des scénarios (PA31), se détache, sur la base d’une analyse multicritères. Il est retenu pour des études approfondies qui nécessitent des activités sur place, des échanges étroites avec des services compétents dans les deux États Hôtes et avec les parties prenantes dans le périmètre de l'implantation.