Comprehensive Study and Optimized Redesign of the CERN's Antiproton Decelerator Target

El Antiproton Decelerator Target (AD-Target) es un dispositivo único responsable de la generación de Antiprotones en la Organización Europea para la Investigación Nuclear (CERN). En operación, intensos haces de protones con una energía de 26 GeV son impactados en su núcleo, un cilindro de 3 mm de diámetro constituido por un material de alta densidad como el iridio, creando partículas secundarias -entre ellas, antiprotones- como consecuencia de las reacciones nucleares inducidas en el interior de éste. La tesis profundiza en las características del target de producción de antiprotones, y en particular, en la respuesta mecánica de su núcleo, el cual está sometido a un incremento de temperatura de aproximademente 2000 grados centígrados en menos de 0.5 microsegundos cada vez que es impactado por el haz de protones primario. Para ello, una metodología combinando técnicas numéricas y experimentales ha sido llevada a cabo. Se han aplicado herramientas computacionales específicas, llamadas hydrocodes, para simular la respuesta dinámica originada en el núcleo del target y su matriz contenedora, hecha de grafito, indicando su potencial fragmentación como resultado de una onda radial de alta frecuencia de presión compresión-tracción generada después de cada impacto del haz de protones. Asimismo, se ha llevado a cabo un experimento llamado HiRadMat27. En éste, varios cilindros de materiales de alta densidad, candidatos para un futuro diseño del target, tales como Ir, W, W-La, Mo, TZM y Ta, han sido expuestos a condiciones dinámicas equivalentes a las alcanzadas en el AD-Target mediante impactos de haces de protones de 440 GeV en la instalación HiRadMat. Se ha usado instrumentación en línea para medir la onda radial pronosticada, confirmando la precisión de las simulaciones de hydrocodes. Todos los materiales irradiados excepto Ta sufrieron agrietamientos internos desde condiciones 5-7 veces menores a las presentes en el AD-Target, mientras que este último aparentemente sobrevivió. La información obtenida ha sido aplicada para proponer un nuevo diseño optimizado del target, el cual incluye un sistema de refrigeración de aire a presión, una nueva configuración en Ta de su núcleo, y una matriz contenedora hecha de grafito expandido (GE). Se han llevado a cabo cálculos de dinámica de fluidos computacional y elementos finitos para validar el sistema de refrigeración y la vida a fatiga del ensamblaje del target. Además, se ha construido un primer prototipo del núcleo del target y su matrix contenedora. Estas actividades marcan la senda para la fabricación de un nuevo lote de targets que garanticen la física de antiprotones en el CERN durante las siguientes décadas de operación.The Antiproton Decelerator Target (AD-Target) is a unique device responsible for the production of antiprotons at the European Organization for Nuclear Research (CERN). During operation, intense 26 GeV energy proton beams are impacted into its core, made of a 3 mm diameter rod of a high density material such as iridium, creating secondary particles -including antiprotons- from the nuclear reactions induced in its interior. This thesis delves into the characteristics of antiproton production and in particular in the mechanical response of the target core material, which is exposed to a rise of temperature of approximate 2000 degrees Celsius in less than 0.5 microseconds each time is impacted by the primary proton beam. A coupled numerical-experimental approach has been applied for this purpose. Specific computational tools, called hydrocodes, have been used for simulating the extreme dynamic response taking place in the target core and its containing graphite matrix, indicating their potential damage and fragmentation as a result of a high frequency radial compressive-to-tensile pressure wave generated after each proton beam impact. A challenging first-of-its-kind experiment called HRMT27 was carried out. Several rods of high density materials, candidate for a future optimized target design, such as Ir, W, W-La, Mo, TZM and Ta were brought to equivalent dynamic conditions as reached in the AD-Target core by impacting them with 440 GeV proton beams using the HiRadMat facility. Online instrumentation was used to measure the predicted radial wave, confirming the accuracy of the hydrocode simulations. All of the irradiated target materials except Ta showed internal cracking from conditions 5-7 times below the present in the AD-Target while the latter apparently survived. Lessons learned are applied for proposing a new optimized target design, including a pressurized-air cooling system, Ta core configuration, and a containing matrix made of expanded graphite (EG). Computational Fluid Dynamic and Structural Finite Element analyses have been carried out to validate the new cooling system and fatigue life of the target assembly. A first prototype of the target core and its containing EG matrix has been built. These activities lead the way into manufacturing a new set of antiproton targets to guarantee antiproton physics at CERN during next decades of operation.L'Antiproton Decelerator Target (AD-Target) és un dispositiu únic responsable de la generació d'Antiprotons a la Organització Europea per la Recerca Nuclear (CERN). En operació, intensos feixos de protons amb una energia de 26 GeV impacten contra el seu nucli, un cilindre de 3 mm de diámetre constituït per un material de densitat alta com l'iridi, creant partícules secundáries - entre elles, antiprotons - com a conseqüència de les reaccions nuclears induïdes a l'interior d'aquest. La tesis profunditza en les característiques del target de producció d'antiprotons i, en particular, a la resposta mecánica del seu nucli, el qual és sotmès a un increment de temperatura de aproximadement 2000 graus centígrads en menys de 0.5 microsegons cada vegada que és impactat pel feix de protons primari. Per aixó, s'ha portat a terme una metodologia que combina tècniques numèriques i experimentals. S'han utilitzat eines computacionals específiques, anomenades hydrocodes, per simular la resposta dinàmica originada al nucli del target i a la seva matriu contenidora, feta de grafit. La dita resposta, indica la seva potencial fragmentació com a resultat d'una ona radial d'alta freqüència de pressió compressió-tracció generada després de cada impact del feix de protons. Així mateix, s'ha portat a terme un experiment anomenat HiRadMat27. En aquest, varis cilindres de materials d'alta densitat, candidats per un futur diseny del target, tals com Ir, W, W-La, Mo, TZM i Ta, han estat exposats a condicions dinàmiques equivalents a les assolides a l'AD-Target mitjanant impactes de feixos de protons de 440 GeV a l'instalació HiRadMat. S'ha utilitzat instrumentació en línia per mesurar l'ona radial pronosticada, confirmant la precisió de les simulacions d'hydrocodes. Tots el materials irradiats excepte Ta van sofrir esquerdaments interns desde condicions de 5-7 vegades menors a les presents a l'AD-Target, mentres que aquest últim aparentment va sobreviure. L'informació obtinguda ha estat aplicada per proposar un nou diseny optimizat del target, el qual inclou un sistema de refrigeració de l'aire a pressió, una nova configuració en Ta del seu nucli, i una matriu contenidora feta de grafit expandit (GE). S'han portat a terme càlculs de dinàmica de fluids computacionals i elements finits per validar el sistema de refrigeració i la vida a fatiga de l'ensambladura del target. S'ha construit un primer prototip del nucli del target i la seva matriu contenidora. Totes aquestes activitats marquen la sendera per a la fabricació del nou lot de targets que garantitzin la física d'antiprotons al CERN durant les següents décades d'operació.Torregrosa Martín, CL. (2018). Comprehensive Study and Optimized Redesign of the CERN's Antiproton Decelerator Target [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/100489TESI

Development of radiation sources based on CAD models for the nuclear analysis of IFMIF-DONES lithium loop

This study has been financed/supported by the University of Granada (Spain), the Regional Government of Andalusia through the project "TAN19_UGR_IFMIF-DONES" and the European Regional Development Fund (ERDF) "A way to make Europe"/ "Andalusia moves with Europe".IFMIF-DONES is a neutron source designed to irradiate materials to be used in future fusion power reactors such as DEMO. The facility is based on a deuteron beam impinging onto a liquid lithium jet to generate the neutron flux. Lithium and Corrosion Products will get activated and produce Be-7 and Activated Corrosion Products (ACP). These products will be distributed along the lithium loop, both dissolved in lithium and deposited locally. This complex gamma source should be properly represented to perform radiological safety studies. A new tool, called CAD2CDGS, was created to represent these sources. This tool creates decay gamma sources based on CAD geometries and codifies them into CDGS format. Sources are specified in the CAD model, allowing a user-friendly approach. The tool is based on Open-Source tools (FreeCAD) and EUROfusion codes (cR2S European SDDR tool). In this article the CAD2CDGS tool methodology, inputs and workflow are explained. Two verification tests have been done to check the correctness. Finally, it is demonstrated the applicability of the tool to IFMIF-DONES, with the radiological zoning analysis of the rooms surrounding the Lithium Loop Cell impact by the Be-7 and ACP.University of GranadaRegional Government of Andalusia "TAN19_UGR_IFMIF-DONES"European Regional Development Fund (ERDF

Cyclicity Near Infinity in Piecewise Linear Vector Fields Having a Nonregular Switching Line

Altres ajuts: acords transformatius de la UABIn this paper we recover the best lower bound for the number of limit cycles in the planar piecewise linear class when one vector field is defined in the first quadrant and a second one in the others. In this class and considering a degenerated Hopf bifurcation near families of centers we obtain again at least five limit cycles but now from infinity, which is of monodromic type, and with simpler computations. The proof uses a partial classification of the center problem when both systems are of center type

Orbitally symmetric systems with applications to planar centers

We present a generalization of the most usual symmetries in differential equations known as the time-reversibility and the equivariance ones. We check that the typical properties are also valid for the new definition that unifies both. With it, we are able to present new families of planar polynomial vector fields having equilibrium points of center type. Moreover, we provide the highest lower bound for the local cyclicity of an equilibrium point of polynomial vector fields of degree 6, M(6) ≥ 48

Algebraic limit cycles in piecewise linear differential systems

This paper is devoted to study the algebraic limit cycles of planar piecewise linear differential systems. In particular we present examples exhibiting two explicit hyperbolic algebraic limit cycles, as well as some 1-parameter families with a saddle-node bifurcation of algebraic limit cycles. We also show that all degrees for algebraic limit cycles are allowed

Limit cycles via higher order perturbations for some piecewise differential systems

A classical perturbation problem is the polynomial perturbation of the harmonic oscillator, (x',y')=(-y + εf(x,y,ε),x εg(x,y,ε)). In this paper we study the limit cycles that bifurcate from the period annulus via piecewise polynomial perturbations in two zones separated by a straight line. We prove that, for polynomial perturbations of degree n, no more than Nn-1 limit cycles appear up to a study of order N. We also show that this upper bound is reached for orders one and two. Moreover, we study this problem in some classes of piecewise Li\'enard differential systems. When we restrict the analysis to some special class this upper bound never is attained and we show which is this upper bound for higher order perturbation in . The Poincar\'e--Pontryagin--Melnikov theory is the main technique used to prove all the results

Water deficit differentially modulates leaf photosynthesis and transpiration of fungus-tolerant Muscadinia x Vitis hybrids

Screening for drought performance among novel fungi-tolerant grapevine genotypes is a key point to consider in semiarid regions where water scarcity is a common problem during fruit ripening period. It is therefore important to evaluate the genotypes’ responses at the level of carbon metabolism and water demand, under water deficit conditions. This study aimed to characterize leaf and plant water use efficiency (respectively named WUEi and WUEpl) of novel INRAE fungi-tolerant genotypes (including LowSugarBerry (LSB) genotypes), under mild and high-water deficit (WD) and to decipher the photosynthetic parameters leading to higher WUEi. For this purpose, experiments were conducted on potted plants during one season using a phenotyping platform. Two stabilized soil moisture capacity (SMC) conditions, corresponding to mild (SMC 0.6) and high (SMC 0.3) WD, were imposed from the onset of berry ripening until the physiological ripeness stage, which was defined as the point at which fruits reach their maximum solutes and water content. At the whole plant level, all genotypes increased WUEpl under high WD. The highest WUEpl was reached for 3176N, which displayed both a high rate of non-structural carbon accumulation in fruits due to high fruit-to-leaf ratio and low plant transpiration because of low total leaf area. However, when normalizing the fruit-to-leaf ratio among the genotypes, G14 reached the highest normalized WUEpl_n under high WD. At the leaf level, WUEi also increased under high WD, with the highest value attained for G14 and 3176N and the lowest value for Syrah. The higher WUEi values for all genotypes compared to Syrah were associated to higher levels of photosynthesis and changes in light-harvesting efficiency parameters (ΦCO2, qP and qN), while no clear trend was apparent when considering the photosynthetic biochemical parameters (Vcmax, Jmax). Finally, a positive correlation between leaf and plant WUE was observed regardless of genotypes. This study allowed us to classify grapevine genotypes based on their grapes primary metabolite accumulation and water consumption during the critical sugar-loading period. Additionally, the study highlighted the potential drought adaptation mechanism of the LSB genotypes

Experimental results and strength model identification of pure iridium

Intense and high energy proton beams are impacted with fixed materials (targets) in order to produce new particles and secondary beams at CERN. In some of these targets, the requirement of reaching high yield production of secondary particles points out to the use of high density materials. The interaction of the beam with the atoms and nuclei of these materials produce extremely fast depositions of energy, highly soliciting them from thermo-structural point of view due to subsequent rise of temperature and pressure waves. Iridium is a good candidate material since exhibits very high density, high melting point, good strength and stability at high temperature, and resistance to thermal shock. The main goal of this study is the investigation of the mechanical behaviour at different temperatures and strain-rates in tensile loading condition of pure iridium. A series of tests at room temperature at different strain-rates (from 10-3 s-1 up to 104 s-1) was performed in order to obtain information about strain and strain-rate sensitivity of the material. In addition, a series of tests at different temperatures in both quasistatic and high strain-rate loading conditions was performed in order to obtain information about the thermal softening of the material (from room temperature up to 1250 °C). The experimental data were used to identify a strength model able to predict the material behaviour over wide ranges of variation of the variables of interest

CERN antiproton target: Hydrocode analysis of its core material dynamic response under proton beam impact

Antiprotons are produced at CERN by colliding a 26 GeV=c proton beam with a fixed target made of a3 mm diameter, 55 mm length iridium core. The inherent characteristics of antiproton production involveextremely high energy depositions i nside the target when impacted by each primary proton beam, making it one of the most dynamically demanding among high energy solid targets in the world, with a risetemperature above 2000 °C after each pulse impact and successive dynamic pressure waves of the order of GPa¿s. An optimized redesign of the current target is foreseen for the next 20 years of operation. As a first step in the design procedure, this numerical study delves into the fundamental phenomena present in the target material core under proton pulse impact and subsequent pressure wave propagation by the use of hydrocodes. Three major phenomena have been identified, (i) the dominance of a high frequency radial wave which produces destructive compressive-to-tensile pressure response (ii) The existence of end-ofpulse tensile waves and its relevance on the overall response (iii) A reduction of 44% in tensile pressure could be obtained by the use of a high density tantalum cladding.Torregrosa Martín, CL.; Perillo Marcone, A.; Calviani, M.; Muñoz-Cobo González, JL. (2016). CERN antiproton target: Hydrocode analysis of its core material dynamic response under proton beam impact. Physical Review Special Topics: Accelerators and Beams. 19(7):1-12. doi:10.1103/PhysRevAccelBeams.19.073402S11219

FIB-SEM investigation and uniaxial compression of flexible graphite

Flexible graphite (FG) with 1 - 1.2 g/cm$^3$ density is employed as beam energy absorber material in the CERN's Large Hadron Collider (LHC) beam dumping system. However, the increase of energy deposited expected for new HL-LHC (High-Luminosity LHC) design demanded for an improvement in reliability and safety of beam dumping devices, and the need for a calibrated material model suitable for high-level FE simulations has been prioritized. This work sets the basic knowledge to develop a material model for FG suitable to this aim. A review of the FG properties available in literature is first given, followed by FIB-SEM (Focused Ion Beam - Scanning Electron Microscopy) microstructure investigation and monotonic and cyclic uniaxial compression tests. Similarities with other well-known groups of materials such as crushable foams, crumpled materials and compacted powders have been discussed. A simple 1D phenomenological model has been used to fit the experimental stress-strain curves and the accuracy of the result supports the assumptions that the graphite-like microstructure and the crumpled meso-structure play the major role under out-of-plane uniaxial compression.Comment: Pre-print template, 57 pages, 14 figure