SPL 704 MHz beta 0.65 cavities mechanical design for EUCARD.

International audienceThe optimizations, based on electromechanical simulations have been carried out in order the design 704 Mhz 5-cell elliptic superconducting cavity for the intermediate energy section (beta 0.65) for accelerating high intensity proton beams in pulsed mode

Mechanical Design of Triple Spoke cavity for Eurisol

International audienceWithin the framework of EURISOL programme, supported by European Union, IPN Orsay has proposed a 352 MHz triple Spoke superconducting cavity for the intermediate energy section beta 0.3 of high power proton linear accelerator. Triple Spoke cavity has a complicate geometry, 3D modeling with coupled electromagnetic and mechanic calculations were performed

Etude d'une cavite accélératrice supraconductrice Spoke pour les accélérateurs de protons de forte intensité

Since a few years, a lot of projects (especially dedicated to transmutation, radioactive beams production, spallation neutron sources or neutrinos factories) are based on high power proton linear accelerators. It has been demonstrated, thanks to their excellent RF performances, that superconducting elliptical cavities represent the best technological solution for the high energy part of these linacs (proton energy from typically 100 MeV). On the contrary, between 5 and 100 MeV, nothing is clearly settled and intensive studies on low-beta cavities are under progress. The main objective of this thesis deals with the study of a new low-beta cavity, called "spoke", which could be used in the low energy part of European XADS and EURISOL accelerators projects. A complete study of a beta 0.35 spoke cavity has been done: from its electromagnetic and mechanical optimization to warm and, above all, cold experimental tests: an accelerating field of 12.2 MV/m has been reached at T=4.2 K, that is to say one of the best value among the spoke cavities performances in the world. It has been shown that the specific ratio of a third, between the spoke bar diameter and the cavity length, led to optimize the surface electromagnetic fields. Moreover, spoke cavities can be used without any trouble, in the low energy part, due to their good rigidity. The experimental measurements performed on the cavity (which was produced by the CERCA company) have confirmed the theoretical calculations, especially, concerning the expected frequency and mechanical behavior. Another study, performed on elliptical cavities, gave an explanation of the discrepancies between the measured and calculated frequencies thanks to a precise 3D geometrical control. Keywords : spoke cavity, superconductivity, proton linear accelerator, geometrical controlLes accélérateurs linéaires (linacs) de protons de forte intensité sont, depuis quelques années, au coeur de nombreux projets internationaux (transmutation des déchets nucléaires, production de faisceaux radioactifs, sources de neutrons de spallation, usines à neutrinos...). Les cavités accélératrices supraconductrices, qui constituent une des pierres angulaires de ces accélérateurs, ont connu un essor très important grâce, en particulier, aux excellentes performances atteintes par les cavités dites « elliptiques ». Alors que le choix technologique concernant la partie haute énergie des linacs (énergie du proton supérieure à 100 MeV) semble maintenant clairement établi avec l'utilisation de ces cavités elliptiques, le débat reste encore ouvert au sujet de la partie intermédiaire (typiquement entre 5 et 100 MeV), pour laquelle différents types de cavités « faible bêta » sont actuellement à l'étude. Le thème central de cette thèse porte donc sur l'étude d'une nouvelle structure accélératrice faible bêta, appelée cavité « spoke », qui pourrait répondre aux différents critères fixés, dans le cadre des projets européens EURISOL (production de faisceaux radioactifs) et XADS (transmutation des déchets nucléaires), pour assurer un bon fonctionnement de l'accélérateur, mais aussi, contribuer à réduire le coût global de telles installations. L'étude complète d'une cavité spoke, bêta 0.35, a donc été réalisée : de sa conception, au moyen de logiciels de simulation électromagnétique et mécanique afin d'optimiser sa géométrie, jusqu'aux mesures expérimentales à chaud et à froid (T=4.2 K) où un excellent résultat a été obtenu, à savoir un champ accélérateur de 12.2 MV/m (une des meilleures performances atteintes avec une cavité spoke dans le monde). L'étude d'optimisation a notamment montré qu'un rapport 1/3 entre la barre centrale et la longueur de la cavité permettait de minimiser les champs électriques et magnétiques de surface pour un champ accélérateur donné. Elle a également établi que les cavités spoke pouvaient parfaitement être utilisées, dans la partie intermédiaire de l'accélérateur jusqu'à un bêta de 0.15, du fait de leur très grande rigidité. Les tests expérimentaux à chaud réalisés sur la cavité (fabriquée par l'entreprise CERCA) ont confirmé les prédictions théoriques attendues (fréquence, profil de champ et caractéristiques mécaniques). Une autre étude, portant sur le contrôle dimensionnel en 3D de cavités monocellules elliptiques, a permis d'expliquer les écarts observés entre les fréquences mesurées et celles visées, issues des codes électromagnétiques

Etude d'une cavité accélératrice supraconductrice Spoke pour les accélérateurs de protons de forte intensité

STRASBOURG-Bib.Central Recherche (674822133) / SudocPARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Alternative RF Tuning Methods Performed on Spoke Cavities for ESS and MYRRHA Projects

International audienceIn order to obtain the target frequency in operation, the resonant frequency of superconducting radiofrequency cavities is controlled and adjusted from the manufacturing to the end of preparation phase. Reaching this right frequency can be challenging due to the narrow frequency range defined by the tuning sensitivity of the cavity and the capability of the tuner. Mechanical deformation until plasticity is attained is of great interest to tune SRF cavities when large frequency shift is needed. But once a cavity is dressed with its helium tank, the only accessible part is its beam pipe, reducing the mechanical action to a push/pull action. This limited possibility has hence to be skilfully associated with chemical etching. An original mechanical tuning of Spoke dressed cavities consists in increasing the pressure inside the helium tank to induce a permanent deformation of the cavity walls. The frequency shift induced by nonlinear deformation is numerically evaluated in order to determine the pressure increments. Both methods were successfully performed on the cavities of the ESS accelerator and of the Myrrha project

Interface Challenges for the SRF Cryomodules for the European Spallation Source

International audienceThe European Spallation Source is currently under construction in Lund in southern Sweden. The main part of the accelerator will consist of two different types of cryomodules housing three different types of cavities ' double spoke cavities and two different elliptical cavities. The spoke cavities as well as the cryomodules will be provided by IPN Orsay, thus the external interfaces to the other accelerator systems have to be verified. While the procurement and assembly of the elliptical cryomodules will be performed by CEA Saclay, the cavities will be provided by INFN Milano and STFC Daresbury. Thus in addition to the external cryomodule interfaces, also the internal interfaces between cavities and cryomodules have to be taken care of. This contribution presents the challenges related to this work

Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement

International audienceThe multipactor effect can lead to thermal breakdown (quench), high field emission and limited accelerating gradient in superconducting accelerator devices. To determine the multipactor breakdown power level, multipactor simulations can be performed. The objective of this study is to compare the results given by different simulation codes with the results of vertical testing of SRF cavities. In this paper, Spark3D [1], MUSICC3D [2] and CST Studio PIC solver [3] have been used to simulate the multipactor effect in the single Spoke resonator developed within the framework of MYRRHA project [4]. Then, a benchmark of these three simulation codes has been made. The breakdown power level, the multipactor order and the most prominent location of multipactor are presented. Finally, the simulation results are compared with the measurements done during the vertical tests

Higher Order Modes Investigation in the PERLE Superconducting RF Cavity

International audienceThe regenerative Beam Break Up (BBU) excited by the dipole Higher Order Modes (HOMs) in superconducting RF (SRF) cavities is a crucial issue for continuous-wave high-current energy recovery linacs. Beam-induced monopole HOMs can increase the cryogenic losses of the linac also. One of the ways to limit these effects is to use HOM couplers on the beam tubes of cavities to absorb and untrap cavity eigenmodes. These couplers feature antennas designed to damp dangerous HOMs and adequately reject the fundamental mode. This study illustrates an investigation of the HOMs of a 5-cell 801.58 MHz elliptical SRF cavity designed for PERLE (Powerful Energy Recovery Linac for Experiments), a multi-turn energy recovery linac (ERL) currently under study and later to be hosted at IJCLab in Orsay. Time-domain wakefield and frequency-domain eigenmode simulations have been used to calculate the cavity broadband HOM impedance spectra and identify the dangerous BBU HOMs. The transmission characteristics of several coaxial HOM couplers have been studied. The efficiencies of several HOM-damping schemes have been compared to propose a HOM endgroup to be fabricated and added to the existing bare SRF cavity

Test Characterization Of Superconducting Spoke Cavities At Uppsala University

As part of the development of the ESS spoke linac, the FREIA Laboratory at Uppsala University, Sweden, hasbeen equipped with a superconducting cavity test facility. The cryogenic tests of a single and double spoke cavitydeveloped by IPN Orsay have been performed in the new HNOSS horizontal cryostat system. The cavities areequipped with a low power input antenna and a pick-up antenna. Different measurement methods wereinvestigated to measure the RF signal coupling from thecavity. Results from the tests confirm the possibility to transport the cavities from France to Sweden without consequences. We present the methods and preliminary study results of the cavity performance

RF test of ESS superconducting spoke cavities at Uppsala University

The European Spallation Source (ESS) is an accelerator-driven neutron spallation source built in Sweden. It will deliver the first protons to a rotating tungsten target by 2019 and will reach the full 5 MW average beam power in the following years. The superconducting Spoke cavities are considered compact structures at low frequencies and having an excellent RF performance in both low and medium velocity regimes, therefore ESS will include a total of 26 double-spoke cavities. The testing of the double-spoke prototype cavity at high power has been conceded to Uppsala University, Sweden, where the Facility for Research Instrumentation and Accelerator development (FREIA) has been equipped with superconducting cavity test facility.     A bare spoke cavity has been tested at the FREIA Laboratory with a self-exited loop at low power level to confirm its vertical test performance at IPNO. Similar test results as IPNO's previous test were obtained with FREIA system. In this paper we present the methods and preliminary study results of the cavity performance