The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.The French contribution to X-IFU is funded by CNES, CNRS and CEA. This work has been also supported by ASI (Italian Space Agency) through the Contract 2019-27-HH.0, and by the ESA (European Space Agency) Core Technology Program (CTP) Contract No. 4000114932/15/NL/BW and the AREMBES - ESA CTP No.4000116655/16/NL/BW. This publication is part of grant RTI2018-096686-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. This publication is part of grant RTI2018-096686-B-C21 and PID2020-115325GB-C31 funded by MCIN/AEI/10.13039/501100011033

Development of experiments aimed at the production of aluminum alloy castings with controlled defect and microstructure, for the validation of numerical model of gas and shrinkage porosity prediction

Nei processi di progettazione e produzione tramite tecnologie di colata di componenti in alluminio ad elevate prestazioni, risulta fondamentale poter prevedere la presenza e la quantità di difetti correlabili a design non corretti e a determinate condizioni di processo. Fra le difettologie più comuni di un getto in alluminio, le porosità con dimensioni di decine o centinaia di m, note come microporosità, hanno un impatto estremamente negativo sulle caratteristiche meccaniche, sia statiche che a fatica. In questo lavoro, dopo un’adeguata analisi bibliografica, sono state progettate e messe a punto attrezzature e procedure sperimentali che permettessero la produzione di materiale a difettologia e microstruttura differenziata, a partire da condizioni di processo note ed accuratamente misurabili, che riproducessero la variabilità delle stesse nell’ambito della reale produzione di componenti fusi. Tutte le attività di progettazione delle sperimentazioni, sono state coadiuvate dall’ausilio di software di simulazione del processo fusorio che hanno a loro volta beneficiato di tarature e validazioni sperimentali ad hoc. L’apparato sperimentale ha dimostrato la propria efficacia nella produzione di materiale a microstruttura e difettologia differenziata, in maniera robusta e ripetibile. Utilizzando i risultati sperimentali ottenuti, si è svolta la validazione di un modello numerico di previsione delle porosità da ritiro e gas, ritenuto ad oggi allo stato dell’arte e già implementato in alcuni codici commerciali di simulazione del processo fusorio. I risultati numerici e sperimentali, una volta comparati, hanno evidenziato una buona accuratezza del modello numerico nella previsione delle difettologie sia in termini di ordini di grandezza che di gradienti della porosità nei getti realizzati.The possibility to predict defects in aluminium alloy cast component, from the very beginning of the design and production phases is a crucial issue. Among the most common defects of a casting, microporosities (i.e. porosities with dimension up to hundreds of m) are highly detrimental for mechanical performances. In this work, after an in-depth bibliographic research, experimental casting devices and procedures were designed in order to produce specimen with controlled defects and microstructure, related to process condition which could be varied in the range of the actual ones, measured on the shop floor. The whole design phase of the casting devices and procedure was carried out using process simulation software which were extensively fine tuned through experimental activities. The experiment proved to be effective in producing specimen with controlled defects and microstructure, in a consistent way. Numerical models for the prediction of gas and shrinkage porosity were evaluated in terms of accuracy in the description of all of the phenomena involving nucleation and growth of porosity and possibility of implementation on industrial cases. The one considered at the state of the art underwent a validation process with the experimental data. The comparison of numerical results and experimental data showed a good match, thus the good capability of the model to predict porosity, both in magnitude and trend throughout the casting

Investigation on the design of a novel selective laser melted insert for extrusion dies with conformal cooling channels

The thermal control and the maintenance of a uniform temperature in the extrusion process of aluminum alloys is a crucial task in order to generate sound profiles with high press productivities. This can be accomplished through liquid nitrogen flowing in conformal cooling channels (CCC). The SLM additive technology offer an optimal solution for an unlimited flexibility of the cooling system, thus allowing tailored cooling strategies. In the present work, a smart thermally controlled die made by AISI H13 was designed aimed at maximize and regulate the cooling efficiency by means of CCC. In the novel die concept, the expensive SLM insert with CC channels, has been integrated into a steel housing conventionally machined. A comprehensive numerical investigation has been performed in order to check the insert designs mechanical and thermal performances both in uncooled and cooled conditions. Then, eight inserts were additively manufactured by means of the SLM (Selective Laser Melting) process with the aim to preliminary verify their experimental feasibility and overall quality. As main results, it was numerically proved the capability of the novel insert design to allow a significantly increase of the production rate and it was experimentally demonstrated the insert manufacturability throughout the SLM technology

Effects of cooling rate on microstructure in EN-AC43000 gravity castings and related T6 mechanical properties.

The aim of this work is to asses a correlation law between local cooling rate and SDAS for the EN AC43000 cast alloy. Bars 200 mm long with a double T cross section (suitable for tensile testing) were sand cast under controlled processing conditions. Chillers of different dimensions and materials, including water cooled ones, were placed at one side of the casting in order to obtain mono-dimensional heat flux and different cooling rates throughout the casting length. Thermocouples were used to acquire local cooling curves. A campaign of FE simulations was run to fine tune boundary conditions and to obtain a reliable cooling rate distribution throughout the whole casting. A correlation between experimental SDAS and simulated cooling rates was assessed. Finally, mechanical properties from extracted specimens in T6 condition were related to local SDAS and Cooling Rate

Modellazione di processo, previsione di microstruttura e proprietà meccaniche nella colata in conchiglia di testate motore in lega di alluminio

In questo lavoro è stata portata a termine un‟analisi numerica di un processo di colata in conchiglia in gravità di una testa motore V8 in lega A356, attualmente in fase di produzione. Il sistema complessivo di colata, composto da sette parti stampo e un elevato numero di anime in sabbia è stato studiato numericamente, mediante un modello agli elementi finiti costituito da 11.8*106 elementi tetraedrici. Le analisi delle fasi di riempimento e solidificazione del getto sono state condotte cercando di replicare in maniera accurata tutte le variabili di processo misurate durante il ciclo di produzione. Le caratteristiche microstrutturali, sono state valutate mediante le correlazioni esistenti tra i valori di SDAS e le velocità locali di raffreddamento, mentre la distribuzione di porosità percentuale è stata stimata numericamente mediante il ricorso ad un modello numerico del software. La validazione delle simulazioni è stata effettuata comparando i dati ottenuti con quelli ricavati da un accurato studio microstrutturale svolto su oltre 2000 micrografie. Questo è stato indirizzato a definire, oltre ai valori di SDAS e area percentuale dei difetti, anche la dimensione e morfologia del silicio eutettico. E‟ stata quindi applicata una relazione empirica, appositamente sviluppata, in grado di valutare le proprietà meccaniche puntuali nella testata motore, noti i soli parametri microstrutturali ottenibili attraverso la simulazione numerica e i valori di durezza del materiale dopo trattamento termico. I valori di resistenza così calcolati hanno mostrato un‟ ottima rispondenza con quelli ottenuti attraverso prove meccaniche su campioni estratti dal componente

Microstructure and mechanical properties of heavy section ductile iron castings: experimental and numerical evaluation of effects of cooling rates

This paper focuses on thedevelopment of experimental relationships between themicrostructure and mechanical properties of a sand cast ductile iron and on the design of a direct ‘in mould’ thermal analysis system for heavy section castings. The casting system was developed in order to obtain different thermal modules, and it has been studied by numerical simulation. The microstructure was estimated through numerical models implemented in a commercial casting simulation code and validated by comparing simulated and experimental data obtained from more than 2000 optical micrographs considering nodularity, density and size of nodules, fractions of graphite, ferrite and pearlite. Empirical relationships between the microstructure and mechanical properties were developed and then implemented in the simulation software in order to evaluate the localmechanical properties. The results of hardness and tensile tests carried out on samples extracted from the castings showed good accordance between predicted and measured mechanical properties

SLM printed steel conformal cooled insert for extrusion dies with anti-wear bearings

Aim of the project: control and maximize extrusion dies cooling efficiency; increase their life by means of the development of wear resistant (harder) material (i.e. material enriched with Tungsten Carbides WC) through the additive manufacturing technology (AM); develop cost-efficient extrusion dies desig