Brazing of Mo to Glidcop Dispersion Strengthened Copper for Accelerating Structures

Alumina dispersion-strengthened copper, Glidcop, is used widely in high-heat-load ultra-high-vacuum components for synchrotron light sources (absorbers), accelerator components (beam intercepting devices), and in nuclear power plants. Glidcop has similar thermal and electrical properties to oxygen free electrical (OFE) copper, but has superior mechanical properties, thus making it a feasible structural material; its yield and ultimate tensile strength are equivalent to those of mild-carbon steel. The purpose of this work has been to develop a brazing technique to join Glidcop to Mo, using a commercial Cu-based alloy. The effects of the excessive diffusion of the braze along the grain boundaries on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazed joints, has been investigated. In order to prevent the diffusion of the braze into the Glidcop alloy, a copper barrier layer has been deposited on Glidcop by means of RF-sputtering

Thermostructural characterization and structural elastic property optimization of novel high luminosity LHC collimation materials at CERN

The CERN Large Hadron Collider is currently being upgraded to operate at a stored beam energy of 680 MJ through the High Luminosity upgrade. The LHC performance is dependent on the functionality of beam collimation systems, essential for safe beam cleaning and machine protection. A dedicated beam experiment at the CERN High Radiation to Materials facility is created under the HRMT-23 experimental campaign. This experiment investigates the behavior of three collimation jaws having novel composite absorbers made of copper diamond, molybdenum carbide graphite, and carbon fiber carbon, experiencing accidental scenarios involving the direct beam impact on the material. Material characterization is imperative for the design, execution, and analysis of such experiments. This paper presents new data and analysis of the thermostructural characteristics of some of the absorber materials commissioned within CERN facilities. In turn, characterized elastic properties are optimized through the development and implementation of a mixed numerical-experimental optimization technique.peer-reviewe

Microchannel cooling for the LHCb VELO Upgrade I

The LHCb VELO Upgrade I, currently being installed for the 2022 start of LHC Run 3, uses silicon microchannel coolers with internally circulating bi-phase \cotwo for thermal control of hybrid pixel modules operating in vacuum. This is the largest scale application of this technology to date. Production of the microchannel coolers was completed in July 2019 and the assembly into cooling structures was completed in September 2021. This paper describes the R\&D path supporting the microchannel production and assembly and the motivation for the design choices. The microchannel coolers have excellent thermal peformance, low and uniform mass, no thermal expansion mismatch with the ASICs and are radiation hard. The fluidic and thermal performance is presented.Comment: 31 pages, 27 figure

Death and the Societies of Late Antiquity

Ce volume bilingue, comprenant un ensemble de 28 contributions disponibles en français et en anglais (dans leur version longue ou abrégée), propose d’établir un état des lieux des réflexions, recherches et études conduites sur le fait funéraire à l’époque tardo-antique au sein des provinces de l’Empire romain et sur leurs régions limitrophes, afin d’ouvrir de nouvelles perspectives sur ses évolutions possibles. Au cours des trois dernières décennies, les transformations considérables des méthodologies déployées sur le terrain et en laboratoire ont permis un renouveau des questionnements sur les populations et les pratiques funéraires de l’Antiquité tardive, période marquée par de multiples changements politiques, sociaux, démographiques et culturels. L’apparition de ce qui a été initialement désigné comme une « Anthropologie de terrain », qui fut le début de la démarche archéothanatologique, puis le récent développement d’approches collaboratives entre des domaines scientifiques divers (archéothanatologie, biochimie et géochimie, génétique, histoire, épigraphie par exemple) ont été décisives pour le renouvellement des problématiques d’étude : révision d’anciens concepts comme apparition d’axes d’analyse inédits. Les recherches rassemblées dans cet ouvrage sont articulées autour de quatre grands thèmes : l’évolution des pratiques funéraires dans le temps, l’identité sociale dans la mort, les ensembles funéraires en transformation (organisation et topographie) et les territoires de l’empire (du cœur aux marges). Ces études proposent un réexamen et une révision des données, tant anthropologiques qu’archéologiques ou historiques sur l’Antiquité tardive, et révèlent, à cet égard, une mosaïque de paysages politiques, sociaux et culturels singulièrement riches et complexes. Elles accroissent nos connaissances sur le traitement des défunts, l’emplacement des aires funéraires ou encore la structure des sépultures, en révélant une diversité de pratiques, et permettent au final de relancer la réflexion sur la manière dont les sociétés tardo-antiques envisagent la mort et sur les éléments permettant d’identifier et de définir la diversité des groupes qui les composent. Elles démontrent ce faisant que nous pouvons véritablement appréhender les structures culturelles et sociales des communautés anciennes et leurs potentielles transformations, à partir de l’étude des pratiques funéraires.This bilingual volume proposes to draw up an assessment of the recent research conducted on funerary behavior during Late Antiquity in the provinces of the Roman Empire and on their borders, in order to open new perspectives on its possible developments. The considerable transformations of the methodologies have raised the need for a renewal of the questions on the funerary practices during Late Antiquity, a period marked by multiple political, social, demographic and cultural changes. The emergence field anthropology, which was the beginning of archaeothanatology, and then the recent development of collaborative approaches between various scientific fields (archaeothanatology, biochemistry and geochemistry, genetics, history, epigraphy, for example), have been decisive. The research collected in this book is structured around four main themes: Evolution of funerary practices over time; Social identity through death; Changing burial grounds (organisation and topography); Territories of the Empire (from the heart to the margins). These studies propose a review and a revision of the data, both anthropological and archaeological or historical on Late Antiquity, and reveal a mosaic of political, social, and cultural landscapes singularly rich and complex. In doing so, they demonstrate that we can truly understand the cultural and social structures of ancient communities and their potential transformations, based on the study of funerary practices

Examination and Assessment of Large Forged Structural Components for the Precompression Structure of the ITER Central Solenoid

Large structural forgings of complex shape are required for several components of the precompression structure of the ITER Central Solenoid, consisting of a stack of six electrically independent modules and featuring a total height of 18 m and a diameter of over 4 m. The precompression structure allows the vertical tensile loads to be reacted and adequate preload to be maintained, in order to insure the contact between the modules during plasma operation. Several components of the precompression structure such as tie plates, lower and upper key blocks, lower and upper components are machined from open die forgings of an unprecedented combination of complex shape and large size. The selected material is FXM-19, a high strength nitrogen bearing austenitic stainless steel. A specific manufacturing schedule including redundant multidirectional forging is applied in order to achieve the required properties and microstructure of the final parts. The paper summarises the lessons learned from the series production of the components. The achievement of a fine and homogeneous microstructure, which is of paramount importance for final inspectability of the parts and to obtain the mechanical properties, is particularly challenging taking into account their large size. It requires a perfect mastering of the whole manufacturing process, from the steelmaking route, based in some cases on sequential remelting of electrodes from different master heats to create large Electroslag Remelted (ESR) ingots, to the sequence of the thermomechanical steps, from the initial upsetting of the ingots to the final solution annealing of the as-forged parts. Non-Destructive Examinations are based on stringent acceptance criteria. A fine microstructure is indispensable to allow full volumetric inspection with sufficient lateral resolution. Indeed, inspectability of the full thickness of the parts by Ultrasonic Testing, compatible with the criteria imposed by the technical specification and the structural requirements of the single components, is only possible in absence of unrecrystallised areas or excessive grain growth

Brazing of Mo to Glidcop Dispersion Strengthened Copper for Accelerating Structures

Alumina dispersion-strengthened copper, Glidcop, is used widely in high-heat-load ultra-high-vacuum components for synchrotron light sources (absorbers), accelerator components (beam intercepting devices), and in nuclear power plants. Glidcop has similar thermal and electrical properties to oxygen free electrical (OFE) copper, but has superior mechanical properties, thus making it a feasible structural material; its yield and ultimate tensile strength are equivalent to those of mild-carbon steel. The purpose of this work has been to develop a brazing technique to join Glidcop to Mo, using a commercial Cu-based alloy. The effects of the excessive diffusion of the braze along the grain boundaries on the interfacial chemistry and joint microstructure, as well as on the mechanical performance of the brazed joints, has been investigated. In order to prevent the diffusion of the braze into the Glidcop alloy, a copper barrier layer has been deposited on Glidcop by means of RF-sputtering

Brazing of Mo to a CuZr alloy for the production of bimetallic raw materials for the CLIC accelerating structures

Future linear accelerators, as CLIC (Compact Linear Collider), are extremely demanding in terms of material properties. Traditionally accelerating structure is made of brazed OFE copper parts. For the high conducting regions submitted to mechanical fatigue, CuZr would represent an improved selection than pure copper while for regions where the highest electric field is applied a refractory metal, i.e. Mo, could result in a better performance. The feasibility of joining such materials, namely CuZr (UNS C15000) and pure Mo has been investigated. The joining method developed and investigated here consists in a vacuum brazing process exploiting a Cu-based brazing filler applied under appropriate vacuum conditions. Apparent shear strength (adapted from ASTM B898) on the joined samples was about 200 MPa. (C) 2010 Elsevier B.V. All rights reserved

Investigation of Materials and Welds for the Precompression Structure of the ITER Central Solenoid

The Central Solenoid (CS) is the backbone of the ITER magnet system. It consists of six independent coils held together by a vertical pre-compression structure that must react tensile loads and provide sufficient preload to maintain coil-to-coil contact during all stages of plasma operation. Material selection and specifications applicable to the structural components of the pre-compression structure are particularly demanding. These include large forgings manufactured from a high strength austenitic stainless steel (FXM-19) with a stringent specification in terms of microstructure and maximum allowed magnetic permeability. Stringent requirements are also imposed on all welded joints. In particular, the attachment welds of the cooling pipes to the structure are subject to challenging restrictions in terms of weld imperfections and geometry. They must induce limited distortion of the components and are submitted to inspections carried out in accordance with the most severe acceptance levels of applicable standards. The results of extensive characterizations based on non-destructive and destructive evaluation of samples from different components and welds are reported in this paper, particularly focusing on the quality achieved at the microstructural and macrostructural level. The influence of the microstructure on the properties and on the inspectability of the material by non-destructive examinations is discussed