The 2020 update of the European Strategy for Particle Physics emphasised the importance of an intensified and well-coordinated programme of accelerator R&D, supporting the design and delivery of future particle accelerators in a timely, affordable and sustainable way. This report sets out a roadmap for European accelerator R&D for the next five to ten years, covering five topical areas identified in the Strategy update. The R&D objectives include: improvement of the performance and cost-performance of magnet and radio-frequency acceleration systems; investigations of the potential of laser / plasma acceleration and energy-recovery linac techniques; and development of new concepts for muon beams and muon colliders. The goal of the roadmap is to document the collective view of the field on the next steps for the R&D programme, and to provide the evidence base to support subsequent decisions on prioritisation, resourcing and implementation.

The IFMIF accelerator aims to provide an acceleratorbased D-Li neutron source to produce high intensity highenergy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. A prototype of the low energy part of the accelerator (LIPAc) is under construction at Rokkasho Fusion Institute in Japan [1]. It includes one cryomodule containing eight half-wave resonators (HWR) operating at 175 MHz and eight focusing solenoids. This article covers the progress of developments in the IFMIF/EVEDA cryomodule: the qualification of eight cavities, the RF conditioning results of eight high-power couplers, the manufacturing and test of the eight superconducting solenoids and the high power tests of fully dressed cavities performed at Saclay. The assembling status of the cryomodule at Rokkasho site is also reported. THE IFMIF LIPAC SRF LINAC The IFMIF/EVEDA SRF Linac mostly consists of one cryomodule designed to be as short as possible along the beam axis to meet the beam dynamic requirements. As depicted in Fig. 1, it is made of a rectangular section vacuum vessel, a warm magnetic shield, a thermal shield cooled with helium gas. A titanium frame supports the cold mass made of a cylindrical phase separator with cryogenic piping, the cavities and the solenoids. Figure 1: The IFMIF LIPAc cryomodule. All the components have been manufactured and qualified. One of the main challenge during the manufacturing phase was to comply with the Japanese regulatory requirements with regard to HPGSL (High Pressure Gas Safety Law). It has been agreed in the collaboration that all components containing helium gas or liquid during operation of the LIPAc have to be designed, manufactured and tested according to ASME standards. For stainless steel components, the rules to follow depends on the internal diameter. Parts with diameter than 6 inches have to respect ASME Boiler and Pressure Vessel Code (BPVC). It concerns the phase separator and the solenoid packages. For smaller parts – i.e. the currents leads and the piping – ASME B31.3 applies. The cavity was the most complicated part to be licensed due to the use of non-referenced materials (niobium, niobium-titanium alloy). Discussions started in 2013 between the Japanese Authorities (KHK) and the collaboration to define the licensing frame. Unexpected activities had to be performed, like numerical simulation and sample testing, to complete the application form of the half-wave resonator [2]. Finally, the document was approved by KHK in March 2016. Most of the components were delivered to Rokkasho in 2018 and beginning of 2019 where they are currently stored awaiting to be assembled. QUALIFICATION OF THE HALF-WAVE RESONATORS The IFMIF HWR is a 175 MHz 0.09 beta half-wave resonator whose nominal accelerating field is 4.5 MV/m. A Saclay type tuning system is installed on the cavity and applies a compressive force on its beam ports to shift the frequency by -50 kHz maximum [3]. A pre-series HWR has been completed and tested during the production of the subcomponents of the series cavities. A series of intermediate and qualification tests have been carried out for this HWR, between each major steps of the production. It included the qualification of the differential etching technique to correct the frequency of the niobium cavity [4]. The series cavities have been manufactured and tested following the licensing requirements described in the approved application form. Each bare cavity has been tested in vertical cryostat before heat treatment and integration of the helium tank. A qualification test was performed on each jacketed cavity. Table 1 and Fig. 2 present the vertical test results for all the cavities. All the qualification tests were carried out up to at least Eacc=5.5 MV/m that is to say with 20% safety margin with respect of the nominal accelerating field of 4.5 ___________________________________________ * E-mail: nicolas.bazin@cea.fr 19th Int. Conf. on RF Superconductivity SRF2019, Dresden, Germany JACoW Publishing ISBN: 978-3-95450-211-0 doi:10.18429/JACoW-SRF2019-WETEA3 SRF Technology Cryomodule cryomodule assembly WETEA3 737 Co nt en tf ro m th is w or k m ay be us ed un de rt he te rm so ft he CC BY 3. 0 lic en ce (© 20 19 ). A ny di str ib ut io n of th is w or k m us tm ai nt ai n at tri bu tio n to th e au th or (s ), tit le of th e w or k, pu bl ish er ,a nd D O I.

The prototype IFMIF cryomodule encloses eight superconducting 175 MHz beta 0.09 Half-Wave Resonators (HWR). They are designed together with the power coupler to accelerate a high intensity deuteron beam (125 mA) from to 5 to 9 MeV. One prototype HWR and the 8 cavities to be hosted in the cryomodule have been manufactured, prepared and tested. The paper describes the phases of the cavities development, including fabrication, processing and RF frequency management. We focus on the results of the RF tests which have been performed for all bare and jacketed HWRs in a vertical cryostat.

In the framework of the IFMIF/EVEDA project, the cryomodule of the Linear IFMIF Prototype Accelerator (LIPAc) will be assembled then tested at Rokkasho in 2019. Eight Series Power Couplers (PC) operating at 175 MHz were manufactured under a CEA contract, in order to equip this Cryomodule. They were all successfully RF conditioned up to 100 kW CW in TW and SW configurations. All the high RF power tests were performed under CIEMAT responsibility in BTESA Company premises, according to the CEA requirements. In order to fix difficulties encountered during the fab process, manufacturing and quality control have been analyzed in depth. Thanks to the corrective actions implemented, every PC reached the performances targeted for qualification. This paper will give details about this manufacturing phase and provide an overview of the obtained RF test results.

The linear accelerator for the IFMIF-DONES facility (DEMO Oriented Neutron Source) will serve as a neutron source for the assessment of materials damage in future fusion reactors. The DONES accelerator, which is based on the design of IFMIF/EVEDA LIPac (Linear IFMIF Prototype Accelerator, which is under construction in Rokkasho, Japan [1]) will accelerate deuterons from 100 keV up to 40 MeV at full CW current of 125 mA. This paper presents the preliminary design of the superconducting linac which is based on five cryomodules. INTRODUCTION The DONES Facility will be a Plant containing all the necessary buildings and systems to house and run an accelerator-based D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume to simulate as closely as possible the first wall neutron flux and spectrum of future nuclear fusion reactors. The Facility will produce a 125 mA deuteron beam, accelerated up to 40 MeV and shaped to have a nominal cross section in the range from 100 mm x 50 mm to 200 mm x 50 mm, impinging on a liquid lithium target 25 mm thick cross-flowing at about 15 m/s in front of it. The stripping reactions generate a large number of neutrons that interact with the materials samples located immediately behind the Lithium Target, in the Test Modules. Figure 1 shows a 3D Model of the DONES Facility. Figure 1: 3D model of the DONES Plant. The DONES Plant is composed of five major areas [2]: the Accelerator Systems (AS) devoted to produce the high power beam, the Lithium Target Systems (LS) were are produced the neutrons, the Test Systems (TS) which include the irradiation test module(s) and the Test Cell, the Central Instrumentation and Control Systems (CI&CS) gathering the systems in charge of performing the global control of the Plant, and finally the Site, Building and Plant Systems (PS) which includes the buildings and the systems providing power, cooling, ventilation, remote handling of components and services to the other systems. THE IFMIF-DONES ACCELERATOR IFMIF-DONES baseline engineering design is based on the IFMIF engineering design developed in the framework of the EDA phase of the IFMIF/EVEDA project [3]. The low energy section of the IFMIF-DONES accelerator is similar to the IFMIF/EVEDA one: the Injector System produces and extracts a 140-mA deuteron beam at 100 keV by its Electron Cyclotron Resonance ion source. A Low Energy Beam Transport (LEBT) section guides the deuteron beam from the source to a Radio Frequency Quadrupole (RFQ) accelerator. This one bunches the beam and accelerates 125 mA to 5 MeV. The beam is injected through a Medium Energy Beam Transport (MEBT) section that conditions it in transverse mode with quadrupoles and in longitudinal mode with rebuncher cavities in order to properly match it to the superconducting linac where it is accelerated to a final energy of 40 MeV and directed to the neutron production target by a High Energy Beam Transport Line (HEBT). The HEBT, which consists of a series of magnetic optics elements, is required to tailor the beam to provide a flat rectangular beam profile on the flowing lithium target. SRF LINAC LAYOUT In order to minimize the beam losses to meet the ‘handson maintenance’ machine requirement, all the components of the linear accelerator as well as the distances between adjacent components are made as short as possible. This led to a very compact design of the accelerator. For the SRF Linac, distances between the successive components are subject to different constraints related to the RF coupler footprint, the amplitude of frequency tuner displacements, the flexible elements interleaved between the superconducting components, the room needed for the assembly and so on. Thanks to the developments already performed in the IFMIF/EVEDA project, as-built dimensions of the SRF Linac components (low beta cavities, solenoids, RF couplers, cold-warm transitions, etc.) are available. Consequently, dimensions of the second cryomodule (equipped with low-beta cavities too) can be precisely defined, and those of the cryomodules equipped with high-beta cavities may be easily extrapolated. By taking into account these as-built dimensions, lengths of 3 over 4 cryomodules of the reference SRF-Linacs [3] are increased. New beam dynamics studies performed with this updated design have given evidence of some weaknesses, mainly: beam losses in the cavities locally exceeds 19th Int. Conf. on RF Superconductivity SRF2019, Dresden, Germany JACoW Publishing ISBN: 978-3-95450-211-0 doi:10.18429/JACoW-SRF2019-MOP097 SRF Technology Cryomodule cryomodule design MOP097 311 Co nt en tf ro m th is w or k m ay be us ed un de rt he te rm so ft he CC BY 3. 0 lic en ce (© 20 19 ). A ny di str ib ut io n of th is w or k m us tm ai nt ai n at tri bu tio n to th e au th or (s ), tit le of th e w or k, pu bl ish er ,a nd D O I.

The need of a neutron source for the qualification of materials to be used in future fusion power reactors have been recognized in the European (EU) fusion programme for many years. The construction and exploitation of this facility is presently considered to be in the critical path of DEMO. This issue prompted the EU to launch activities for the design and engineering of the IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented Neutron Source) facility based on and taking profit of the results obtained in the IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project, presently conducted in the framework of the EU-Japan Bilateral Agreement on the Broader Approach to Fusion. These activities and R&D work for the IFMIF-DONES Plant are presently taking place in the framework of a work package of the EUROfusion Consortium, in direct collaboration with the Fusion for Energy Organization. The main objective of these activities is to consolidate the design and the underlying technology basis in order to be ready for IFMIF-DONES construction as early as possible. The paper presents the main engineering results for a generic site obtained during the first years of design work, as indicated in the recently released IFMIF-DONES Preliminary Engineering Design Report, making emphasis on the design evolution from previous phases and on the critical issues to be further developed in the near future. The proposed European site to host the facility (Granada, Spain) is briefly introduced as well.

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent pulses in the 40-4 nm spectral range [1]. It comprises two types of accelerators connected to a single Free Electron Laser (FEL) for advanced seeding configurations (seeding with High order Harmonic in Gas, echo). A 400 MeV superconducting Linear Accelerator, adapted for studies of advanced FEL schemes, will enable future upgrade towards high repetition rate and multi-user operation by splitting part of the macropulse to different FEL lines. A 0.4 1 GeV Laser Wake Field Accelerator (LWFA) [2] will also be qualified by the FEL application. After the Conceptual Design Report, R&D has been launched on different sub components. Transport calculation of longitudinal and transverse manipulation of a LWFA electron beam enables to provide theoretical amplification, a test experiment is under preparation.

The European Spallation Source (ESS) is a pan-European project and one of world's largest research infrastructures based on neutron sources. This collaborative project is funded by a collaboration of 17 European countries and is under construction in Lund, Sweden. The 5 MW, 2.86 ms long pulse proton accelerator has a repetition frequency of 14 Hz (4 % duty cycle), and a beam current of 62.5 mA. The Superconducting Radio-Frequency (SRF) linac is composed of three families of Superconducting Radio-Frequency (SRF) cavities, which are being prototyped, counting the spoke resonators with a geometric beta of 0.5, medium-beta elliptical cavities (beta_{g}=0.67) and high-beta elliptical cavities (beta_{g}=0.86). After a description of the ESS linear accelerator layout, this article will focus on the recent progress towards integration of the first test results of the main critical components to be assembled in cryomodules, then in the ESS tunnel.

The LIPAc (Linear IFMIF Prototype Accelerator) is a 9MeV – 125 mA CW deuteron accelerator [1]. It is designed and manufactured in most parts in Europe and is being installed in Japan. Among its main components, the MEBT (Medium Energy Beam Transport line) [2] will shape the 5 MeV beam before its injection into the SRF Linac that will accelerate it up to its end energy. This paper addresses the engineering issues associated with the integration of the MEBT supplied by CIEMAT and SRF Linac supplied by CEA and CIEMAT at the LIPAc facility. It considers the seismic analysis of the beamline components and the tests and alignment activities performed in Europe prior to shipping the components to Rokkasho. MOTIVATIONS The LIPAc project is a collaboration between European and Japanese contributors. The Japanese contributors are mainly responsible for the design, manufacture and installation of the building and conventional facilities, while the European contributors supply most of the accelerator components and several other related equipment. This sharing implies a number of constraints that have to be taken into account for the design and assembly of the machine. Since the LIPAc will be installed in Japan, seismic analyses are necessary to ensure the integrity of the accelerator in case of earthquake. Since the machine is being manufactured in Europe, it is highly desirable to assemble and test most of the equipment before shipment to Japan for two main reasons. The first is to maximise the reaction time to resolve technical issue close to the manufacturing site. The second is to avoid delaying the schedule on LIPAc site operations where many other concurrent activities related to installation and commissioning of other equipment are performed [3]. A balance has to be found with the constraints linked to the shipment. The vibrations and accelerations encountered during a sea trip from Europe to Japan are indeed significant. If the equipment cannot sustain then another option is to use air transportation. Nonetheless, if these constraints are still too high for airplane transportation or if the cost is not acceptable, the solution is to ship the components separately and realize the assembly in Japan. Another important constraint is the alignment of the equipment that depends not only on the accuracy of the machining, but also on the tools and methods used during assembly and installation. If possible, it is always better to carry out an alignment campaign during assembly of the equipment and before shipment to Japan. The installation inside the LIPAc building can then be carried out more rapidly using some of the external frame CCR’s (Corner Cube Reflector) and re-checking the rest. MEBT Seismic Analysis An RS (response spectrum) analysis was performed to check the behaviour of the MEBT in case of a seismic event. A simplified model prepared from the 3D CAD mock-up was introduced to the Ansys v14.5 – workbench environment. The first six calculated natural modes from the modal analysis fall below 20 Hz, three of them are located in the maximum acceleration range (2-10 Hz) of the excitation spectrum. These modes contribute in great part to the maximum displacements observed in the RS analysis results at the top of the valves linked to the turbo pumps. Figure 1: MEBT deformation from RS analysis and turbo pump design change. As a result of the analysis, the supports were redesigned fixing the turbo pumps rigidly instead of using springs, see Figure 1. The RS analysis did not reveal more points that could be a problem for the MEBT. Assembly Test of ACCT Due to the reduced space at the interface between the RFQ (Radio Frequency Quadrupole) and the MEBT where the ACCT (AC Current Transformer) is located, it was decided to perform an assembly test of the ACCT Proceedings of IPAC2016, Busan, Korea WEPMR045 07 Accelerator Technology T33 Subsystems, Technology and Components, Other ISBN 978-3-95450-147-2 2377 C op yr ig ht © 20 16 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s mounting, see Fig. 2. This operation requires dismounting the upper half of the first MEBT magnet in order to access to the ACCT screws. The difficulty is that these screws, that are accessible only by inserting a tool through the ACCT, have to be tightened alternatively by a quarter turn while the ACCT is displaced progressively. This is due to the presence of threaded holes on both side of the assembly, the ones on RFQ side having a chucking function whereas the ones on ACCT side are present to prevent the screws from falling into the ACCT. A first test showed that it was not possible to install the ACCT without the use of special tooling. A dedicated temporary support for the ACCT was designed, manufactured and used during a second assembly test. Notwithstanding the remaining poor accessibility, the test was successful and validated the assembly sequence. Figure 2: Assembly test of the ACCT. Alignment Campaign Since the MEBT tolerates sea shipment, all the main components (five quadrupoles, two scrapers, two bunchers, the beamline with four Beam Position Monitors and three turbo pumps) were assembled on the MEBT frame. An alignment survey was performed on all the MEBT components except of the second buncher, see Figure 3. The assembly table of the MEBT incorporates specific features defining the assembly coordinate frame. These features have been surveyed in the first step of the assembly and a best fit process has been launched to find the best match between the coordinate of the surveyed features and the nominal coordinates as defined in the reference CAD model. This process implicitly guarantees the best coincidence between the CAD coordinate frame and the assembly bench. The second phase of the assembly consisted in the characterization of the components to be installed. In this phase, each part of the MEBT has been measured and a proper set of offset distances has been defined to take into account the differences between the mechanical and magnetic axis of each part. On the basis of these preliminary activities the proper assembly of the MEBT started. Two Hexagon Laser Trackers have been used simultaneously to drive the operators to lock the part under installation in its final position. Each tracker was put on continuous measuring mode such as to produce in real time a simplified window showing the difference between measured and target points. The procedure proved to be very useful and time saving. Alignment was considered satisfactory only when the difference between target point coordinates and measured point coordinates was less than the global uncertainty of the measuring process. For the adopted process and layout, this uncertainty was not higher than 20 microns with a confidence level of 95%. The last phase of the assembly was the full survey of the fiducial supports of the MEBT. More than 80 fiducial nests have been surveyed many times realizing a database of more than 500 measurements. These coordinates will be used to assess dilations due to transportation to Rokkasho and, if necessary, to re-align the components after the delivery. Figure 3: Two laser trackers and watch windows during MEBT alignment campaign. SRF LINAC Seismic Analysis Similarly to the MEBT, RS analyses were performed for the SRF Linac to examine its behaviour during a seismic event. The cold mass includes a frame supporting the cavities, solenoids, couplers and He phase separator, and hangs from the top of the vacuum vessel by ten vertical Ti alloy rods and four horizontal ones in lateral direction. The first analysis revealed a potential problem at the interface between the cold mass and its support. The analysis results show that the cold mass would move nearly 10 mm longitudinally, which could damage its supporting structures. The problem was solved by adding two locking systems in the middle of the cold mass frame, thereby reducing the longitudinal displacement. Figure 4: SRF Linac design optimisation following seismic analyses. A second analysis highlighted a further swinging motion of the cavities and couplers (again nearly 10 mm in WEPMR045 Proceedings of IPAC2016, Busan, Korea ISBN 978-3-95450-147-2 2378 C op yr ig ht © 20 16 C C -B Y3. 0 an d by th e re sp ec tiv e au th or s 07 Accelerator Technology T33 Subsystems, Technology and Components, Other the longitudinal direction), and also on the He phase separator (around 2 mm). The central beam located in the middle of the cold mass frame, and to which all the cavities/solenoids are fixed via invar rods, was too flexible (7 mm of the 10 mm deformation mentioned previously). In addition, the stresses observed in the invar rods were above the yield limit of this material. Four modifications were applied to the design in order to improve the SRF Linac seismic behaviour, see Figure 4. The central beam was reinforced by changing its geometry. The invar rod diameter was increased from 8 to 12 mm and its fixing system to the central beam modified. Dampers were fixed to the base of the vacuum vessel to limit the displacement of the couplers and as a result the cavities and solenoids. A longitudinal bar linking all He phase separator supports was added. A third RS analysis showed that the implemented changes were sufficient to reduce the displacements of all the components (see Figure 5) and validate the design from a seismic perspective. Figure 5: SRF Linac deformation after design optimization. Assembly and Shipment The assembly of the SRF Linac beam line (cavities, solenoids, couplers) was initially planned in the premises of CEA at Saclay prior to shipment to Rokkasho [4]. A risk analysis was performed to assess the viability of this solution. As a result the decision was taken to carry out the assembly task in Rokkasho under the full responsibility of F4E (Fusion for Energy). A first reason was linked to the weakness of the ceramic coupler windows. These fragile components support the RF antennas located i

The Linear IFMIF Prototype Accelerator (LIPAc), which is presently under design and realization, aims to accelerate a 125 mA deuteron beam up to 9 MeV. Therefore, a low-beta 175 MHz Half-Wave Resonator (HWR) was initially designed and manufactured with a tuning system based on a capacitive plunger located in the electric field region. Following the results of the vertical tests at 4.2K, this tuning system was abandoned and replaced by a conservative solution based on the HWR wall deformation using an external mechanical tuner. This paper will focus on the manufacturing of the prototype cavity, the studies realized to explain the first test results and the solutions taken to overcome the difficulties, leading to the validation of the prototype. Then, we will present the new cavity design.

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft X-ray region. The project consists of a Free Electron Laser (FEL) line enabling the most advanced seeding configurations: High order Harmonic in Gas (HHG) seeding and Echo Enable Harmonic Generation (EEHG) with in-vacuum (potentially cryogenic) undulators of 15 and 30 mm period. Two accelerator types feed this FEL line : a 400 MeV Conventional Linear Accelerator (CLA) using superconducting cavities compatible with a future upgrade towards high repetition rate, for the investigations of the advanced FEL schemes; and a 0.4 1 GeV Laser Wake Field Accelerator (LWFA), to be qualified in view of FEL application, in the single spike or seeded regime. Two pilot user experiments for timeresolved studies of isolated species and solid state matter dynamics will take benefit of LUNEX5 FEL radiation and provide feedback of the performance of the different schemes under real user conditions.

LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, and coherent pulses in the soft x-ray region. The single Free Electron Laser (FEL) line fed either by a superconducting Linear Accelerator of 400MeV or a 0.4-1GeV Laser Wake Field Accelerator (LWFA) enables seeding (High order Harmonic in Gas seeding and Echo Enabled Harmonic Generation) for the advanced fourth generation source with the conventional accelerator, and single spike operation for the fifth generation source with the LWFA. Two pilot user experiments for time-resolved studies of isolated species and solid state matter will take benefit of LUNEX5 FEL.

A  = 0.5 5-cell 704 MHz cavity was developed in the framework of European R&D programs on high intensity pulsed proton injectors. Medium beta elliptical cavities are known to be sensitive to Lorentz detuning, which can become difficult to deal with in pulsed operation. The cavity was optimized to reduce the Lorentz detuning by means of two series of rings welded around the irises, and equipped with a piezo tuning system. In order to test the cavity in pulsed mode, a power coupler with 1 MW capability was connected to the cavity. We report here on the fully equipped cavity tests at 1.8 K carried out in the horizontal cryostat Cryholab at Saclay to study its RF and mechanical behavior in pulsed mode, mostly with 2 ms pulses at a 50 Hz repetition rate. The compensation of Lorentz force detuning has been achieved at an accelerating gradient of 13 MV/m (44 MV/m peak surface electric field).

The Spiral 2 project at GANIL aims at producing exotic ion beams for Nuclear Physics. The accelerator of the primary beam is a superconducting Linac designed to provide 5 mA deuteron beams at 40 MeV. It will also allow accelerating stable ions of different Q/A values ranging from protons to Q/A=1/6 heavy ions. The accelerator should be commissioned by the end of 2011, first beam in 2012. The first tests aiming to produce exotic beams are planned one year later. The superconducting LINAC consists of 12 low beta (0.07) quarter wave (88 MHz) superconducting (SC) cavities and 24 beta (0.14) SC cavities integrated in their cryomodule. The status of the low beta cryomodules, supplied by the Irfu institute of CEA Saclay, is reported in this paper. The RF full power tests were performed on the qualifying cryomodule at the end of 2008 and the beginning of 2009, and the tests of the first series cavity in vertical cryostat are in course.