Sökning: "Positron annihilation"

Visar resultat 1 - 5 av 25 avhandlingar innehållade orden Positron annihilation.

  1. 1. Modelling of radiation damage and positron annihilation in metallic materials

    Författare :Qigui Yang; Pär Olsson; Bernardo Barbiellini; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Radiation damage; First-principles; Positron annihilation spectroscopy; Cu precipitation; Two-component density functional theory; Tungsten; Transition metals; Kärnenergiteknik; Nuclear Engineering; Physics; Fysik;

    Sammanfattning : The radiation damage is one of the key concerns in the research of materials used in radiation environments. In this thesis, we theoretically investigate the radiation damage phenomenon by focusing on two important topics: the defect production and evolution, and the defect characterization. The first part aims at two aspects. LÄS MER

  3. 2. Investigation of Nuclear Materials with Positron Measurements

    Författare :Petty Bernitt Cartemo; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; depth profiling; positron beam; nuclear materials; radiation damage; positron lifetime measurements;

    Sammanfattning : Positron Annihilation Lifetime Spectroscopy can be used to characterize radia- tion-induced material defects to subsequently optimize nuclear materials with respect to radiation damage. Nuclear Systems of the future such as Generation IV and fusion concepts demand high performance from structural materials, comprising a material's stability in highly-radiative and hot environments. LÄS MER

  4. 3. Novel computational methods for image analysis and quantification using position sensitive radiation detectors

    Författare :Alejandro Sanchez Crespo; Stig A. Larsson; Magnus Dahlbom; Stockholms universitet; []
    Nyckelord :LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; SPET; PET; CMOS; spatial resolution; photon depth of interaction; positron annihilation; positron range; non-collinearity; scatter; attenuation; lung ventilation; lung perfusion; breast tumour; Medicine; Medicin;

    Sammanfattning : The major advantage of position sensitive radiation detector systems lies in their ability to non invasively map the regional distribution of the emitted radiation in real-time. Three of such detector systems were studied in this thesis, gamma-cameras, positron cameras and CMOS image sensors. LÄS MER

  5. 4. Particle Interferometry in e+e- Annihilation

    Författare :Raluca Muresan; Partikel- och kärnfysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; quantum field theory; DELPHI; Elementary particle physics; LEP; e e- annihilation; Interferometry; Correlation; Bose-Einstein; Elementarpartikelfysik; kvantfältteori; Fysicumarkivet A:2000:Muresan;

    Sammanfattning : This thesis is the result of three years of work in Lund University, as a member of DELPHI group, at the Elementary Particle Physics Department. The work concerns the study of Bose-Einstein correlations in electron-positron collisions at LEP. LÄS MER

  7. 5. Free Volume Determination in Polymers and Polymer Blends

    Författare :Camilla Wästlund; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; positronium formation; crystallinity; polymer blends; inhibition; polymers; free volume; positron annihilation; phase separation; distribution;

    Sammanfattning : The free volume of a polymer, which corresponds to the unoccupied regions accessible to segmental motions, is an important parameter for understanding and predicting many of its characteristic properties. The concept of free volume is the basis for understanding the molecular mobility in polymers. LÄS MER