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The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018, and will deliver 10 low-beta cryomodules as In-Kind Contribution to the PIP-II project, with cavities supplied by LASA-INFN and power couplers and tuning systems supplied by Fermilab. This paper presents the CEA scope of work that includes the design, manufacturing, assembly and tests of the cryomodules and the upgrade of the existing infrastructures to the PIP-II requirements., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Proton Improvement Plan II (PIP-II) that will be installed at Fermilab is the first U.S. accelerator project that will have significant contributions from international partners. CEA joined the international collaboration in 2018, and is responsible of the 650 MHz low-beta section made of 9 cryomodules, with the design of the cryostat (i.e the cryomodule without the cavities, the power couplers and the frequency tuning systems) and the manufacturing of its components, the assembly and tests of the pre-production cryomodule and the 9 series ones. This paper will present the design of the 650 MHz low-beta cryomodule., Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

Eight of the medium and high beta cryomodules deliv-ered to ESS by CEA are tested at CEA before delivery; the two medium and high beta prototypes and the three first of each type of the series. The goal of these tests is to validate the assembly and the performances on few cryomodules before the next cryomodules of the series are delivered to ESS. This paper summarizes the general results obtained during the tests at 2 K and at high RF power, Pmax = 1.1 MW. The cavities reach the ESS re-quirements, E_{acc} = 16.7 MV/m (Medium beta) and 19.9 MV/m (High beta) with an efficient compensation of the Lorentz detuning by the piezo tuner over the full RF pulse length of 3.6 ms at 14 Hz. After the successful tests at CEA, the first cryomodules have been shipped to ESS where the final acceptance test are performed., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

CEA in Kind contribution to the ESS superconducting LINAC includes 30 elliptical medium and high-beta cryomodules. CEA is in charge of the production of all the components (except the cavities delivered by LASA and STFC) as well as the assembly of the cryomodules and a few cryogenic and RF tests. The power couplers operating at a maximum power of 1.1MW on a 3.6ms pulse at 14Hz are conditioned at high RF power on a dedicated stand. The assembly of the cryomodules is performed at CEA by a private Company under the supervision of CEA. This paper presents the status of the cryomodules production and the infrastructure dedicated to this project at CEA Saclay., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The staged installation and commissioning of LIPAc is ongoing at Rokkasho Fusion Institute of QST, Japan for validating the low energy section of the IFMIF deuteron accelerator up to 9 MeV. The LIPAc Superconducting Radio Frequency accelerator (SRF) cryomodule is assembled under the responsibility of the EU Home Team, and the assembly work recently started at Rokkasho in March 2019. To fulfil the cleanliness requirements for the assembly process, QST took the responsibility to prepare the infrastructure of a cleanroom and associated devices. In this present paper, the details of the preparation work for the cryomodule assembly made by QST will be presented., Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany

CEA is in charge of the 30 elliptical medium and high-beta cryomodules to be installed in the ESS tunnel in Lund, Sweden. Before launching the assembly of the series cryomodules, CEA developed a medium-beta cryomodule technology demonstrator in a collaboration with IPNO, LASA and ESS. This paper briefly presents the cryomodule assembly and summarizes the main results of the high RF power tests performed in 2018 in a dedicated test stand in CEA Saclay. The main ESS requirements were reached: E_{acc} = 16.7 MV/m in cavities, Pforward = 1.1 MW in power couplers, RF pulses length = 3.6 ms at 14 Hz. The piezo tuners efficiently compensated the Lorentz forces detuning and could stabilize the accelerating field better than 1% over the full length of the expected ESS 2.86 ms beam pulse without any LLRF regulation system. Following this successful validation CEA started the assembly of the first ESS medium-beta series cryomodule, Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Two ESS elliptical cavities cryomodule prototypes are being developed and will be tested at CEA Saclay before starting the series production. This paper presents the preliminary test results of the first medium beta cavities cryomodule demonstrator M-ECCTD. The measurements of the cryogenic performances at 80 K and 2 K of the different cryomodule components and circuits are given. The first RF test results performed at low power are also reported., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Repair actions of different extent have been performed at 61 modules of the 100 accelerating series modules for the European XFEL to qualify them for the tunnel installation. Four modules could not be repaired in time. CEA Saclay managed to perform three major repairs in parallel to the series module integration, the residual repair actions took place at DESY Hamburg. In this paper we will give an overview on the various technical problems which required being fixed before the tunnel installation and on the repair actions performed., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

CEA Saclay in collaboration with IPN Orsay is in charge of the ESS elliptical cavities cryomodule design, prototyping and series production. Two cryomodule prototypes are being developed and will be tested at CEA Saclay before starting the series production. The main cryomodule design features are first reminded. We present the cavities and couplers test results and the achieved assembly sequences of the first medium beta cavities cryomodule demonstrator M-ECCTD. The progress on the preparation of the CEA cryomodule test station is given. The procurement status and development plan of the second high beta demonstrator H-ECCTD are also reported. Finally we give the components procurement progress and the assembly strategy of the 30 series cry-omodules to be integrated at CEA before delivery to ESS at Lund., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

The industrialized string and module assembly of 10³ European XFEL cryomodules has been performed at CEA-Saclay between September 2012 and the spring of 2016. The general features and achievements of this construction project will be reviewed, including lessons learned regarding organization, industrial transfer, quality control and assembly procedures. An overview of the cryomodule performance and RF test results will be presented., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+ [1], has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium beta elliptical cavity prototypes. We describe the cavity preparation procedure from buffer chemical polishing to vertical test. Finally magnetic probes (Fluxgate) were installed on the cavity to determine magnetic field background during vertical test. The latest vertical test results showed that our cavity design performance are beyond requirements., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

The European Spallation Source (ESS) accelerator is a large superconducting linac under construction in Lund, Sweden. A collaboration between CEA Saclay, IPN Orsay and ESS-AB is established to design the elliptical cavities cryomodule of the linac. It is foreseen to build and test two cryomodule demonstrators within the next two years. We present the design evolution and the fabrication status of the cryomodule components housing four cavities. The latest test results of two prototype cavities are shown. The cryomodule assembly process and the on-going testing infrastructures at CEA Saclay are also described., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

The main linac of the European XFEL will consist of 100 accelerator modules, i.e. 800 superconducting accelerator cavities operated at a design gradient of 23.6MV/m. In this context CEA-Saclay built an assembly facility designed to produce one module per week, ready to be tested at DESY. The facility overcame the foreseen production rate. We would like to highlight and discuss the critical fields: cleanliness and vacuum. A new assembly method to protect final assembly against particulates contamination has been implemented on the production line. Impact on cryomodule RF test is presented. Particle transport measurements on components used for the European XFEL accelerator module are presented. The results indicate that the nominal operation of the automated pumping and venting units will not lead to particle transport. Vacuum acceptance tests are of major interest: leak tests and residual gas analysis (RGA) are used to control the absence of air leak and contamination. The RGA specifications have been slightly relaxed to ensure the production rate., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

The 101 cryomodules of the XFEL cold linac will be integrated at Saclay under the CEA responsability by the industrial operator ALSYOM, at the production rate of cryomodule per week. Each cryomodule includes a string of 8 Niobium superconducting cavities and a BPM-quadripole unit (downstream end). To avoid particle contamination of the RF cavities, the strings are assembled in an ISO4 cleanroom by following strict cleaning and high-vacuum procedures. The major technical challenge of the string integration thus lies in the capacity to realize 25 connections in two weeks while protecting the cavity and coupler RF surfaces and to check their leak-tightness up to 10-10 hPA.l/s. The partial demonstration was made by the CEA team with the first pre-series module XM-3 which achieves a total accelerating voltage of 232 MV preserving the individual performances of cavities. In this paper the status and challenges of the production line is presented, including the quality management, equipment and operator training aspects. The optimisation process toward a faster assembly while preserving or actually decreasing the cavity exposure to contamination sources is also described., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The series production of the superconducting accelerator modules for the European XFEL requires a production rate of one module per week. For this, assembly procedures have to be well-defined and repeatable, and the punctual supply of parts from the contributing institutes has to be assured. Configuration management (CM) has been introduced for clarification of responsibilities and establishing procedures. CM provides unique identification of parts, part status and location tracking, versioning of documentation, and procedures for change control, auditing and handling non-conformities. The configuration database, which is based on DESY’s Engineering Data Management System, contains the entire information which is necessary for assembling the accelerator modules. The content ranges from work instructions how to build a cryomodule up to individual records of all produced parts. Workflow and reports help tracking production progress and establishing production quality. The presentation gives an overview of the CM solution which is in place for the assembly of the XFEL accelerator modules, and reports experience and lessons learned from series production of the first modules., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

6 pages; International audience; In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > Hc^Nb for magnetic shielding of bulk niobium to increase the breakdown magnetic field inside SC RF cavities [1]. We have deposited high quality "model" samples by magnetron sputtering on monocrystalline sapphire substrates. A 250 nm layer of niobium figures the bulk Nb. It was coated with a single and multi-stacks of NbN layers (25 or12 nm) separated by 15 nm MgO barriers, and characterized by X-Ray reflectivity and DC transport measurements. DC or AC measurement of HC1 is an important goal for multilayer evaluation during the sample evaluation phase. A clear increase of HC1 at low frequency is promising indication since HC1 is expected to increase with frequency (see e.g. [2] and references therein). We have measured the first penetration field (HP~HC1) on DC magnetization curves in a SQUID system. HP of NbN covered sample is increased compared to Nb alone. We have also developed a set-up that allows measuring a large range of field and temperature with a local probe method based on 3rd harmonic analysis. We have confirmed the screening behavior of a single 25 nm NbN layer placed on the top of a Nb Layer.