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CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL contains 13 half-wave resonator (HWR) low beta cavities (β= 0.09) at 176 MHz and 14 HWR high-beta cavities (β = 0.18) at 176 MHz. The low-beta and high-beta series were qualified in 2021 and 2022 respectively. This contribution will focus on the observation of the multipactor barriers for all cavi-ties. It will present series of data obtained during the conditioning of these cavities, Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

CEA, KEK and Marui Galvanizing Company have been collaborating to apply the Vertical Electropolishing (VEP) process of elliptical SRF cavities to a 704MHz single-cell ESS-type cavity, using a rotating so called and patented "Ninja" cathode. First presented results* were promising with a gradient of 27MV/m achieved, without any heat treatment applied. The performance has been pushed further since. The cavity has undergone a heat treatment at 650°C during 10h, followed by a final VEP sequence and a baking at 120°C during 48h hours. The achieved gradient at 2K was 44MV/m (power limitation), and the quality factor Q₀ exceeding 5·10¹⁰ up to 10 MV/m. The superiority of VEP compared to standard "BCP" chemical treatment is demonstrated and we intend now to scale the process to 5-Cell β=0.86 ESS cavity. We also intend to push further the performance by applying "2-step baking" (75°C and 120°C) proposed by FNAL, which was successfully applied at CEA Saclay on 1300MHz single-cell resonators with gradients above 50MV/m achieved after VEP bulk treatment., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL consists in four cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β= 0.09) at 176 MHz. The last two identical cryomodules will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The low-beta prototypes was qualified in 2019. Low-beta series manufacturing is on-going. The high-beta prototype was first tested in 2019 but failed. A new prototype was tested in the end of 2020. This contribution will present the results of the tests for low- and high-beta SARAF cavities, series and prototypes., Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

The excitation of Higher Order Modes (HOM) or Lower Order Modes (LOM) has been performed for years on multi-cell superconducting accelerating cavities as a mean to coarsely locate a quench, a defective area or ignite a plasma for surface cleaning. Moreover, such multi-mode testing is very useful to understand more accurately the frequency dependence of the surface resistance in a wide range of surface magnetic fields (0, Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

Vertical Electro-Polishing (VEP) of elliptical cavities using rotating Ninja cathodes (Marui Company patented technology) has continually been improved since 2012 and successfully applied for 1300MHz multicell ILC-type resonators. The goal of the presented study is to apply this technology to 704 MHz ESS-type resonators with both better Q₀ and accelerating gradients in mind. We intend to demonstrate the superiority of VEP compared to standard Buffer Chemical Polishing (BCP), for possible applications such as MYRRHA accelerator. We describe here the promising results achieved on β=0.86 single-cell cavity after 200 µm uniform removal. The cavity quenched at 27 MV/m without any heat treatment. The surface resistance achieved was less than 5nΩ at 1.8K. Substantial performance improvement is expected after heat treatment of the cavity and additional 20 µm VEP sequence. A cathode for 5-Cell ESS cavity is concomitantly under design stage., Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

Studying flux expulsion during superconducting cavities test increases the need for exhaustive magnetometric cartography. The use of Anistropic Magneto Resistance (AMR) sensors, much cheaper than commercial fluxgates, allows the use of tens of sensors simultaneously. Such sensors are developed and sold for room temperature application but are resistant to cryogenic temperatures. However, they need proper calibration, which is more difficult at cryogenic temperature. Actually, this calibration uses the flip of the magnetization of the anisotropic ferromagnetic element, which coercitive field is increased at low temperature. We will present the development of method and software carried out at CEA for the use of such sensors, as well as the preliminary design of a rotating magnetometric device destined to elliptical cavities., Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

For the development of efficient superconducting cavi-ties, field emission is an important parasitic phenomena to monitor. A diagnostic system composed of Geiger-Mueller (G-M) probes, NaI(Tl) scintillators are placed in the cryomodule test stand. Collected data is analysed and confronted to particle tracking simulation and electro magnetic shower code. With such systematic analysis we aim to identify the most probable field emission location and hence help to improve clean procedures during as-sembly and operation., Proceedings of the 20th International Conference on RF Superconductivity, SRF2021, East Lansing, MI, USA

International audience; 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 resonant 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.

International audience; 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 up to the final energy at 2 GeV. 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. CEA Saclay is in charge of the cavity prototypes that is designing, manufacturing, testing and integrating them into demonstrator cryomodules. We have manufactured 6 medium beta and 5 high beta cavities and we present here the latest results concerning these activities.

CEA Saclay is in charge of the cavity prototypes that is designing, manufacturing, testing and integrating them into demonstrator cryomodules. We have manufactured 6 medium beta and 5 high beta cavities. As part of these activities we are interested in field emission as one of the limiting factors for cavity performances. We are currently collecting data from cavities operated in vertical cryostat and inside cryomodules. Analysis are carried out by means of particle tracking simulation and comparison with radiation dose monitor and scintillators., Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany

CEA is committed to delivering a Medium Energy Beam Transfer line and a Super Conducting Linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons from 1.3MeV to 35MeV or deuterons from 2.6 MeV to 40.1MeV. The SCL consists in 4 cryomodules separated by warm section housing beam diagnostics. The two first identical cryomodules hosts respectively 6 and 7 half-wave resonator (HWR) low beta (0.091) cavities 176MHz. In order to test the cavity with its tuner and coupler and validate some design consideration, the Equipped Cavity Test Stand (ECTS) has been designed and will be presented., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5mA beam of either protons to 35 MeV or deuterons to 40 MeV. The SCL consists in 4 cryomodules. The first two cryomodules host 6 7 half-wave resonator (HWR) low beta cavities (β = 0.09) at 176 MHz, and the last two crymodules host 7 HWR medium beta cavities (β = 0.18). The low beta prototype was qualified, the medium beta is being qualified. The results of the RF tests will be presented in this poster., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The RF power coupler system for the RFQ of the ESS LINAC will feed 1.6 MW peak power through two coaxial loop couplers for a 352.21 MHz operation at the expected duty cycle. A specific test stand has been designed to condition the power couplers, and test the different auxiliary components in the nominal conditions of the RFQ. The power couplers were successfully assembled, installed and instrumented on the test cavity. This paper presents the general layout of the test stand, the installation and preparation of the power couplers for their conditioning at high RF power up to the ESS nominal conditions., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Marui Galvanizing Co.Ltd., and CEA have been studying Vertical Electro-Polishing (VEP) on Nb single-cell accelerating superconducting accelerator cavity with the goal of mass-production and cost-reduction, in collaboration with KEK within TYL-FJPPL Particle Physics Laboratory. Marui has invented and patented a rotative cathode called ‘i-Ninja'. The version 5 has been tested for the first time in Europe at CEA Saclay. The four wings of the cathode remove efficiently, bubbles of hydrogen, and the chosen parameters make it possible to achieve better surface and uniform material removal compared to VEP with a fixed cathode. The effect of the temperature of the cavity walls on current oscillations has been precisely studied. Two single-cell cavities have been electro-polished and tested at 2 K in vertical cryostat and the results will be presented., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The SaTHoRI test stand (Satellite de Tests Horizontal des Résonateurs IFMIF) aims to characterize a jacketed and fully dressed cavity with its coupler and tuner. A dedicated test cryostat has been manufactured and is connected to an existing horizontal test cryostat which provides the cryogenic coolant. A RF source ' provided by the IFMIF collaboration, one of the four RF sources which will be used for the cryomodule at Rokkasho ' has been installed and commissioned at CEA. This paper describes the test stand and presents the first results., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technology for Nb superconducting RF cavity in collaboration with KEK. In this collaboration, we developed a unique cathode namely Ninja cathode for VEP treatment of Nb cavities. We have already reported that longitudinal symmetry in niobium removal and surface state of a single cell cavity were improved after VEP using the Ninja cathode. In this article, we report a result of accelerating gradient evaluation for 1.3 GHz single cell RF cavity after VEP with Ninja cathode in collaboration with KEK and CEA Saclay., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy 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 is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz and eight focusing solenoids. This paper presents the status of the IFMIF SRF Linac., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

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+, 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 and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy 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 is under construction at Rokkasho in Japan. It includes one cryomodule containing 8 half-wave resonators (HWR) operating at 175 MHz .The first manufactured HWR has passed low power tests at 4.2K in vertical cryostat succesfully and exceeds the specifications. It has also been tested in the dedicated horizontal Sathori cryostat equiped with its cold tuning system. The serial production and qualification tests of the 8 cavities which will eventually equip the cryomodule are carried out in parallel. In this paper, we focus on the HWR preparation and test results and give a status of the manufacturing activities., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

A 1.3 GHz single-cell niobium (Nb) coupon cavity was vertically electropolished (VEPed) with three different Ninja cathodes which were specially designed for VEP of 1.3 GHz superconducting RF elliptical (ILC/Tesla type) cavities. The cathodes were fabricated to have different surface areas and different distances between cathode surface and the equator. The Ninja cathode prepared with an enhanced cathode surface area was covered with a meshed shield to avoid bubble attack on the surface of the cavity cell. It has been turned out that the anode-cathode distance and the cathode area affect surface morphology of the equator. A smooth equator surface was obtained in the cases in which the cathode surface was geometrically close to the equator or instead the cathode surface area was sufficiently larger. Two 1.3 GHz ILC/Tesla type single-cell cavities VEPed with the Ninja cathodes and using optimized conditions showed good performance in vertical tests., 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 X-ray Free Electron Laser (E-XFEL) will use reentrant beam position monitors (BPMs) in about one quarter of the superconducting cryomodules. This BPM is composed of a radiofrequency (RF) reentrant cavity with 4 antennas and an RF signal processing electronics. Hybrid couplers, near the cryomodules, generate the analog sum and difference of the raw pickup signals coming from two pairs of opposite RF feedthroughs. The resulting sum (proportional to bunch charge) and difference signals (proportional to the product of position and charge) are then filtered, down-converted by an RF front-end (RFFE), digitized, and digitally processed on an FPGA board. The task of CEA/Saclay was to cover the design, fabrication and beam tests and deliver these reentrant cavity BPMs for the E-XFEL linac in collaboration with DESY and PSI. This paper gives an overview of the reentrant BPM sys-tem with focus on the last version of the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at the DESY FLASH2 linac and in the E-XFEL injector are presented., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

Le présent texte porte sur la question du ressort ou mobile (« Triebfeder ») de l’action morale chez Kant. L’interprétation qui y est soutenue consiste à dire qu’il n’y a pas qu’un seul ressort de ce type chez Kant, comme le soutiennent maints commentateurs, mais plutôt deux : la loi morale et le sentiment de respect. Le nerf argumentatif de cette thèse réside dans la prise en compte systématique des aspects des facultés de l’esprit humain impliquées dans la question du ressort moral chez Kant. Deux éléments jouent ici un rôle particulièrement important : (i) les deux sens explicites attribués par Kant au mot « volonté », mot qui peut signifier (a) la raison pratique et (b) la faculté de désirer, et (ii) la division de la faculté de désirer en (a) (libre) arbitre et (b) raison pratique. Plus d’une douzaine d’interprétations, réparties sur plus d’un siècle, sont analysées de manière critique, et deux modifications du manuscrit allemand de la « Critique de la raison pratique » sont proposées pour le chapitre « Des ressorts de la raison pure pratique »., This text focuses on the question of the incentive (“Triebfeder“) of moral action in Kant’s philosophy. The interpretation that is supported here is that there isn’t only one incentive of this sort in Kantian morality, as argued by many commentators, but rather two: the moral law and the feeling of respect. The argumentative nerve of this thesis lies in the systematic consideration of aspects of the faculties of the human mind involved in the question of the moral incentive in Kant. Two elements are here particularly important: (i) the two meanings explicitly assigned by Kant to the word “will”, a word which can mean (a) practical reason and (b) the faculty of desire, and (ii) the division of the faculty of desire in (a) (free) power of choice (“Willkür”) and (b) practical reason. More than a dozen interpretations spread over a century are critically analyzed, and two changes of the German manuscript of the “Critique of practical reason” are also proposed, in the chapter “Incentives of the pure practical reason”.

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

Two prototypes of elliptical superconducting cavities have been designed and manufactured in the frame of the French-Swedish agreement for ESS. These 5-cell cavities have a beta value of 0.86 and their frequency is 704.42 MHz. The nominal accelerating gradient on the ESS accelerator is 19.9 MV/m at 2K. We present the manufacturing status of the cavities by two different vendors as well as the specific means which have been developed for the cavity treatments performed at CEA after delivery. We emphasis the activities performed on the first bare cavities recently received at CEA such as the RF measurement and tuning operations, the cleaning and chemical treatments and the clean room assembly including high pressure rinsing. Finally, first test results at 2K in vertical cryostat are reported., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

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 up to the final energy at 2 GeV. 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. CEA Saclay is in charge of the cavity prototypes that is designing, manufacturing, testing and integrating them into demonstrator cryomodules. We have manufactured 6 medium beta and 5 high beta cavities and we present here the latest results concerning these activities., Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany

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 resonant 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., Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany