The heat transfer performance of the Helium-cooled Multi-jet (HEMJ) divertor was investigated. The HEMJ design uses impinging jets to significantly enhance its heat transfer capability. The convective heat transfer coefficient predicted by computational fluid dynamics software packages is on the order of 50,000 W/(m2-K). The high predicted values of the convective heat transfer coefficient necessitated experimental validation, which was the focus of this investigation. A test section which simulates the thermal performance of the HEMJ divertor was designed, constructed, and instrumented for testing an in air flow loop. The operating conditions of the air flow loop were chosen to match the non-dimensional operating conditions expected for the HEMJ divertor in a post-ITER fusion power plant. The air flow loop experiments were performed for mass flow rates of 2.0 g/s to 8.0 g/s and with incident nominal heat fluxes of 0.8 MW/m2 and 1.0 MW/m2. The angular variation of the heat transfer coefficient was also investigated. Numerical simulations which matched the experimental operating conditions were performed using the computational fluid dynamics software package, FLUENT® 6.2. Comparisons of the experimental and numerical pressure drop, temperature, and heat transfer coefficient were made. The experimental results agreed with the numerical predictions for all operating conditions in this investigation. This provided a strong degree of confidence in using the FLUENT® software package to analyze the HEMJ divertor design.

Fusion energy is a potential candidate for sustain-able steady-state energy supply. However, a fully functional fusion reactor is not yet available and several remaining challenges need to be addressed before fusion becomes a reliable source. One of the remaining challenges with fusion is the plasma-induced modification of the inner wall of the tokamak, i.e. the structures surrounding hot plasma. Due to the rarity of tritium, an important element in future fusion fuel, the plasma facing component (PFC) should have as low fuel retention as possible. In this thesis, methods for controlling ion accumulation in a material sample have been developed. Using the new system, a molybdenum (42Mo) target has been implanted with deuterium (2H) and the retention has been measured with ion beam analysis. The experiment was carried out using particle accelerators at the Ångström Laboratory at Uppsala University. Following tasks were completed before the experiment took place: (a) automation of the target position regulator, (b) development of control software, and (c) calibration and testing of the system. The deuterium dose was estimated at the level of1.9·1017 atoms/cm2.The deuterium concentration in molybdenum was found to be around 28·1015 atoms/cm2. This corresponds to a retention rate of around (15±3)%. / Fusion är en potentiell kandidat för hållbar kontinuerlig energi. Tyvärr är en fullt fungerande fusionsreaktor inte tillgänglig ännu och flera utmaningar kvarstår att lösa innan det blir en tillförlitlig källa. En av dessa utmaningar är plasma- inducerad modifikation av den inre väggen, dvs. strukturen närmast det heta plasmat i en tokamak. Tritium är en viktig komponent i ett framtida fusionsbränsle och väldigt sällsynt. Därför måste mängden bränsle som fastnar i väggen minimeras. I detta arbete har metoder för jonbestrålning av ett materialprov utvecklats. Med hjälp av det nya systemet har molybden (42Mo) bestrålats med deuterium (2H) och bibehållandet av deuterium har mätts med jonstråleanalys. Experimentet utfördes med hjälp av partikelacceleratorer i Ångströmlaboratoriet vid Uppsala Universitet. Följande uppgifter utfördes innan experimentet ägde rum: (a) automatisering av provmanipulatorn, (b) utveckling av programvara för styrning och (c) kalibrering och test av systemet. I ett avslutande test uppskattades den implanterade dosen till 1, 9 · 1017 atomer/cm2. Proverna var därefter analyserade och med kärnreaktionsanalys hittades ungefär 28 · 1015 atomer/cm2. Detta motsvarar ett bibehållnade på ungefär (12 ± 3)%. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

Durant cette thèse, les difficultés rencontrées pour la mesure de température de surface des composants métalliques face au plasma dans les tokamaks sont présentés. Les méthodes de thermographie infrarouge nécessitent de connaitre l'émissivité du matériau et la contribution de l'environnent pour les matériaux de faible émissivité. Des méthodes ont été développées afin de s'affranchir de ces difficultés mais elles répondent à des configurations particulières et aucune n'est adaptée pour une mesure de température de surface de matériaux métalliques dans un tokamak.La méthode de pyrométrie active présentée dans cette étude réalise des mesures de température de surface indépendamment du flux réfléchi et de l'émissivité en utilisant l'effet photothermique. La validation de cette technique en laboratoire sur des matériaux métalliques avec un flux réfléchi pour les régimes impulsionnel et modulé s'est accompagnée d'une modélisation de la variation de température induite par l'effet photothermique et de l'évolution temporelle des signaux obtenus pour optimiser les paramètres de la source et de la chaine d'acquisition. Les résultats expérimentaux ont déterminé les domaines d'application en température et en longueur d'onde de détection.Le dimensionnement d'une installation de pyrométrie active sur tokamak avec une caméra infrarouge bicolore a été réalisé pour une mesure de température sans contact.La méthode de pyrométrie active est une technique complémentaire des méthodes classiques utilisées dans le cadre de la thermographie en environnement tokamak qui permet de réaliser des mesures de température de surface locale et 2D indépendantes du flux réfléchi et de l'émissivité. / During this PhD, the challenges on the non-intrusive surface temperature measurements of metallic plasma facing components in tokamaks are reported. Indeed, a precise material emissivity value is needed for classical infrared methods and the environment contribution has to be known particularly for low emissivities materials. Although methods have been developed to overcome these issues, they have been implemented solely for dedicated experiments. In any case, none of these methods are suitable for surface temperature measurement in tokamaks.The active pyrometry introduced in this study allows surface temperature measurements independently of reflected flux and emissivities using pulsed and modulated photothermal effect. This method has been validated in laboratory on metallic materials with reflected fluxes for pulsed and modulated modes. This experimental validation is coupled with a surface temperature variation induced by photothermal effect and temporal signal evolvement modelling in order to optimize both the heating source characteristics and the data acquisition and treatment. The experimental results have been used to determine the application range in temperature and detection wavelengths.In this context, the design of an active pyrometry system on tokamak has been completed, based on a bicolor camera for a thermography application in metallic (or low emissivity) environment.The active pyrometry method introduced in this study is a complementary technique of classical infrared methods used for thermography in tokamak environment which allows performing local and 2D surface temperature measurements independently of reflected fluxes and emissivities.