This Preliminary Design Report is the main deliverable of the Design Study phase period 2011-2014 and served as a reference for the international Cost and Schedule Review called by the CERN Director of Accelerators and Technology in March 2015. Following the very positive results of the reviews, the CERN management endorsed the cost and plan (with some changes mainly related to civil engineering and the financial profile) and the CERN Council approved the project in September 2015 (formal approval for the MTP period 2016-2020, and endorsement of the full Cost-to-Completion until 2026). The project leadership is particularly grateful to the CERN management for its continuous support and encouragement and in particular to the Director-General Rolf Heuer for his personal engagement in having the project initiated and approved during his mandate.

The new European Strategy for Particle Physics, adopted by the special CERN Council of Brussels on 30 May 2013, placed HL-LHC as a first priority project for the next decade. Consequently, CERN management inserted the project in the Medium Term Plan (5-year plan) and a kick off meeting of HL-LHC as a construction project was organized in Daresbury on 11 November 2013. The HL-LHC project is accompanied by upgrade projects of all LHC Experiments and by the LHC Injector Upgrade Project (LIU). The Experiment upgrade projects are dealt with by their International Collaborations. The LIU project has a separate management, project structure and budget line and plans for a complete implementation during Long Shutdown 2 (LS2), by the end of 2020. The Experiments upgrade and LIU projects are not covered by this TDR.A Cost and Schedule Review series, reviewing both the HL-LHC and LIU projects and reporting to the CERN Director of Accelerators and Technology, Dr. Frédérick Bordry, started in March 2015, with C&SR-I. Following the very positive results of the review, the CERN management endorsed the cost and planning. In September 2015 the CERN Council approved the MTP 2016-2020, containing the funding for the project for that period and envisaging the full Cost-to-Completion (CtC) of the project by 2026. Finally in June 2016, the CERN management had the High Luminosity LHC project, i.e. the upgrade of the collider and its infrastructure, formally approved by the CERN Council, with full financing till 2026. The approved CtC is 950 MCHF of material budget in CERN accounting.In August 2016, a re-baselining of the HL-LHC project was approved by CERN management (and endorsed by the C&SR-II of October 2016) in order to keep the CtC ceiling while accommodating extra cost in the technical infrastructure (mainly in the civil engineering). The present TDR reflects the design of the project at the time of approval by the CERN council, June 2016, with the modifications introduced in the re-baselining exercise in summer 2016.The project leadership is particularly grateful to the CERN management for its continuous support and encouragement and in particular to the CERN Director of Accelerators and Technology, Dr. Frédérick Bordry for his continuous support and guidance from the beginning of the project, to former Director-General Dr. Rolf Heuer for his engagement in having the project initiated and started the funding during his mandate, as well as to the present Director-General Dr. Fabiola Gianotti, for having pursued and obtained the full approval of the entire HL-LHC project by the Council in June 2016, the first CERN project with such status after the LHC.

The ESS Design: Accelerator 6The ESS Design: Target 66The ESS Design: Controls 93The ESS Design: Conventional Facilities 109Physica ScriptaPhys. Scr. 93 (2018) 014001 (121pp) https://doi.org/10. 1088/1402-4896/aa9bff This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercialNoDerivs 3.0 licence. Content from this work may be used under the terms of the Creative Commons Attribution-NonCommercialNoDerivs 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Neutron scattering is a well-developed and extensively used means to get access to fundamental properties of biological matter as well as of physical materials. Until the end of the twentieth century that was mainly practiced with-and limited in performance by-the continuous flux of neutrons from ageing nuclear reactors (e.g. the Institut Laue-Langevin (ILL), the flagship of neutron research in Europe and in the world) [1]). Looking forward to the following two decades, an OECD report published in 1998 diagnosed the foreseeable decrease of the number of operational facilities [2] and the need to progress in performance. Considering the high scientific interest and the increasing importance of the subject for society at large, the report concluded by strongly recommending the construction of next generation neutron sources in America, Europe and Asia. Pulsed spallation neutron sources (SNS) using a proton beam power exceeding 1 MW were specifically mentioned as the most interesting high performance facilities in the future landscape of neutron laboratories.The USA was the first country to follow this advice by building the SNS in the Oak Ridge National Laboratory (ORNL) which started in 2006 [3, 4]. Japan followed in 2009 with the Japan Proton Accelerator Research Centre (J-PARC) in Tokai [5,6]. In Europe, the subject was part of a concerted effort to further develop the European world-leading largescale research infrastructures suite. In 2003, the European Strategy Forum for Research Infrastructures (ESFRI), set up by the Research Ministries of the Member States and associated countries, concluded that a 5 MW long-pulse, single target station layout with nominally 22 'public' instruments was the optimum technical reference design for an European Spallation Source (ESS) that would meet the needs of the European science community in the second quarter of the century [7].Six years later, in 2009, it materialised in a real project with the adoption of the site of Lund (Sweden). A preconstruction phase followed until the end of 2013 during which the design was finalised [8]. Construction then started with the first neutron beams planned to be available in 2019, and the ESS facility to be operational at full performance in 2025.2 Description 2.1 Principle and specifics. The high level parameters of ESS are shown in table 1. As at SNS and J-PARC, neutrons at ESS are produced by spallation, when the 2 GeV protons hit the meta...

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