Introduction des contraintes de propagation et rayonnement électromagnétiques dans l'étude et la conception d'émetteurs/récepteurs de puissance

Les phénomènes de propagation et de rayonnement électromagnétique doivent être pris en compte dès la phase de conception des modules émetteur-récepteur radar (T/R modules) afin d'augmenter leur compatibilité électromagnétique (CEM). Après un rappel de l'architecture générale d'un radar et des T/R modules, nous avons évoqué les aspects de CEM d'un point de vue fonctionnel et normatif. Une bonne conception des T/R modules nécessite la connaissance des phénomènes électromagnétiques, en particulier la caractérisation des sources et des chemins de propagation des perturbations. A l'aide de simulations et de mesures nous avons pu caractériser certains de ces phénomènes. A cet effet, nous avons développé un banc de mesure champ proche électromagnétique permettant la caractérisation de modules complets et la mise en évidence de désadaptations de circuits. Cet outil de mesure a été validé et caractérisé à l'aide de circuits passifs dont le comportement électromagnétique est connu. Face aux éventuelles perturbations électromagnétiques, il faut mettre en place des solutions de blindage, de filtrage et respecter certaines règles de design. Nous avons alors proposé une méthodologie de conception des T/R modules qui tient compte des phénomènes électromagnétiques en préconisant notamment l'utilisation des outils de mesure et de simulation.The electromagnetic radiation and propagation phenomena have to be taken into account in the conception phase of Transmit/ Receive modules (T/R modules) for radar applications in order to increase their electromagnetic compatibility (EMC). After a quick review of radar and T/R module architecture, we have dealt with the EMC aspects from a working and standard point of view. An optimal T/R module conception needs the knowledge of electromagnetic phenomena, in particular the characterization of perturbation sources and propagation paths. With simulation and measurement tools, we have characterized some phenomena. To that effect, we have developed an electromagnetic near field measurement bench allowing the characterization of complete modules and circuits mismatchings. This measurement tool has been validated and characterized with passive circuits whose electromagnetic behavior is known. To avoid electromagnetic perturbations, shielding, filtering solutions and design rules are necessary. So we have proposed a methodology of T/R module conception that takes electromagnetic phenomena, simulation and measurement tools into account.ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Conditioning of the Power Couplers for the ESS Elliptical Cavity Prototypes

International audienceIn the framework of the European Spallation Source (ESS), some power couplers have been designed and manufactured to supply, with RF power, the medium-beta (β=0.67) elliptical cavities of the cryomodule demonstrator. The power couplers work at 704.4 MHz and are tested up to 1.2 MW (repetition rate=14 Hz, RF pulse width close to 3.6 milliseconds). The CEA Saclay is in charge of the design, the manufacturing, the preparation and the conditioning of these power couplers. In this paper, after a general presentation of the power couplers used in the ESS LINAC and their characteristics, we give some détails about the manufacturing and then we describe the different steps of the preparation (cleaning), the assembly of the couplers on the coupling box in cleanroom, the baking of the couplers and the conditioning procedure. Finally, the experimental results obtained in travelling and standing waves on the first pairs of couplers will be shown

Performance Analysis from ESS Cryomodule Testing at CEA

International audienceCEA Saclay is in charge of the production of 30 elliptical cavities cryomodule as part of the in Kind contribution to the ESS superconducting. The two medium and high beta prototypes and the three first of each type of the series cryomodules have been tested at CEA in slightly different conditions than at ESS (both in terms of cryogenic operation as well as RF conditions). The goal of these tests was to validate the assembly procedure before the delivery of the series to ESS where the final acceptance tests are performed. This paper summarizes the main results obtained during the tests at CEA with a particular attention to the field emission behaviour

Conditioning of the First Mass Production Power Couplers for the ESS Elliptical Cavities

International audienceIn the framework of the European Spallation Source (ESS), CEA Paris-Saclay is in charge of the delivery of 9 medium beta (β = 0.67) and 21 high beta (β = 0.86) cryomodules. Each cryomodule is composed of 4 cavities equipped with RF (Radio Frequency) power couplers (704.42 MHz, 1.1 MW maximum peak power, repetition rate=14 Hz, RF pulse width > 3.1 ms). Ten prototype power couplers have been manufactured to validate the design and the performance. Currently the mass production of the 120 couplers started and the six first pre-series medium beta couplers have been successfully conditioned. The achievement of this milestone allowed us to launch the production of the remaining 30 medium beta couplers. This paper presents the conditioning of the pre-series couplers

ESS MEDIUM BETA CAVITY PROTOTYPES MANUFACTURING

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. We describe here the procedures and numerical analysis leading from half-cells to a complete medium cavity assembly, which take into account not only the frequency of the fundamental accelerating mode but also the higher order modes near the machine line. The half-cell selection process to form dumb bells will be described, as well as the reshaping and trimming procedure

Status of the High Power Couplers for ESS Elliptical Cavities

International audienceIn the framework of the European Spallation Source (ESS), CEA Paris-Saclay is responsible for the delivery of 30 cryomodules (9 medium beta (β = 0.67) and 21 high beta (β = 0.86) ones). Each cryomodule contains 4 elliptical cavities equipped with a radio frequency power coupler. The ESS nominal pulse is 1.1 MW maximum peak power over a width of 3.6 ms at a repetition rate of 14 Hz. The design of the couplers for medium beta and for high beta cavities is the same, except a small difference of the antenna penetration to adjust the Q_{ext}. The mass production of the 120 couplers started and all the medium beta couplers have been conditioned at room temperature. The first cryomodules equipped with the power couplers were successfully tested at high RF power and with cavities at 2K reaching the ESS nominal pulse. The main issue at the start of the series production could be fixed and it was due to bad TiN coatings that caused abnormal dielectric losses in the window. Thus, this paper deals with the TiN coating defect, presents the conditioning procedure and gives a conditioning report of these 36 couplers

Status of the Power Couplers for the ESS Elliptical Cavity Prototypes

International audienceIn the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a superconducting section is being developed. This accelerator owns two kinds of cavities called “medium beta cavity” (β=0.67) and “high beta cavity” (β= 0.86). These cavities are equipped with RF power couplers whose main characteristics are: fundamental frequency: 704.42MHz, peak RF power: 1.1MW, repetition rate: 14Hz, RF pulse width>3.1ms. These couplers are common to the two cavities. The CEA Saclay is responsible for the design, the manufacture, the preparation and the conditioning of the couplers used for the Elliptical Cavities Cryomodule Technological Demonstrators (ECCTD). This work is performed in collaboration with ESS and the IPNO. This paper describes the coupler architecture, its different components, the main characteristics and the specific features of its elements (RF performance, dissipated power, cooling, coupler box test for the conditioning). The status of the manufacture of each coupler part is also presented

Results of the RF Power Tests of the ESS Cryomodules Tested at CEA

International audienceEight 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

ESS SRF Linear Accelerator Components Preliminary Results and Integration

International audienceThe 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

Preliminary Test Results of the First ESS Elliptical Cryomodule Demonstrator

International audienceTwo 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