Sökning: "Helium"

Visar resultat 1 - 5 av 114 avhandlingar innehållade ordet Helium.

  1. 1. Helium Filled Bubbles in Solids : Nucleation, Growth and Swelling

    Författare :Odd Runevall; Nils Sandberg; Charlotte Becquart; KTH; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Helium; Radiation Damage; DFT; molybdenum; MgO;

    Sammanfattning : When nuclear fuel, fabricated for the purpose of transmuting spent fuel is irradiated, significant amounts of He is produced from alpha particles mainly emitted when 242Cm decays into 238Pu. From irradiation experiments it is known that the presence of He in the solids alters the swelling behaviour of the material. LÄS MER

  2. 2. Double Excitations in Helium Atoms and Lithium Compounds

    Författare :Marcus Agåker; Jan-Erik Rubensson; Leif Karlsson; David Ederer; Uppsala universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; Atomic and molecular physics; Soft X-ray emission; resonant inelastic X-ray scattering; double excitations; lithium halide; helium; Atom- och molekylfysik;

    Sammanfattning : This thesis addresses the investigation of doubly excited 2l´nl states in helium atoms and double core excitations in solid lithium compounds.Measurements on He are made in field free environments and under the influence of electric and magnetic fields, using synchrotron based inelastic photon scattering. LÄS MER

  3. 3. Helium measuring system for on-line fuel and control rod integrity surveillance in BWRs

    Författare :Irina Larsson; Chalmers University of Technology; []
    Nyckelord :helium measurements; helium release; fuel and control rod failures;

    Sammanfattning : Accurate supervision of fuel and control rod integrity in a nuclear reactor core is very important for maintaining a safe and reliable operation of the reactor. Fuel rod failures can cause increased doses to personnel in the power plant, increased backend costs, limitations of the reactor operation and unplanned shut downs, which can lead to large economic losses. LÄS MER

  4. 4. Tailored process gases for laser powder bed fusion

    Författare :Camille Nicole Géraldine Pauzon; Chalmers University of Technology; []
    Nyckelord :Helium; Laser powder bed fusion; AM process productivity; Spatter particles; Residual oxygen; 316L stainless steel; Argon; Nitrogen; Additive manufacturing; Process atmosphere; Process stability; Residual stresses.; Ti-6Al-4V; Alloy 718;

    Sammanfattning : Metal laser powder bed fusion (L-PBF) allows for production of complex components using the energy from a laser to locally melt micron-sized powder following a layer-wise approach. Considerable scientific efforts are focused on addressing the influence of the process parameters on the melting stability and the control of material properties, while developing necessary monitoring and characterization tools. LÄS MER

  5. 5. Soft X-ray Scattering Dynamics Close to Core Ionization Thresholds in Atoms and Molecules

    Författare :Johan Söderström; Jan-Erik Rubensson; Lorenzo Avaldi; Uppsala universitet; []
    Nyckelord :Physics; Soft X-ray emission; Resonant inelastic X-ray scattering; Double excitations; Helium; X-ray-emission-threshold-electron coincidence; Fysik;

    Sammanfattning : In this Thesis studies of highly excited states in gas-phase atoms and molecules (He, Ne, N2, O2, N2O and CO2) using a variety of synchrotron-radiation based techniques are presented. The three techniques used most frequently are X-ray-emission-threshold-electron coincidence (XETECO), X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) and they are all given a brief introduction. LÄS MER