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Laboratory of Physics of Ionic Crystals and Laboratory of X-Ray Spectroscopy

“ Prospects of increasing the radiation resistance in the bulk and at the surface of dielectric materials for fusion reactors ” Prof. A leksandr Lushchik (luch@fi.tartu.ee). Institute of Physics University of Tartu (IPUT), Estonia. Laboratory of Physics of Ionic Crystals and

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Laboratory of Physics of Ionic Crystals and Laboratory of X-Ray Spectroscopy

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  1. “Prospects of increasing the radiation resistance in the bulk and at the surface of dielectric materials for fusion reactors”Prof. AleksandrLushchik (luch@fi.tartu.ee) Institute of Physics University of Tartu (IPUT), Estonia Laboratory of Physics of Ionic Crystals and Laboratory of X-Ray Spectroscopy Estonian Target-financed project “Fundamental Phenomena in Wide-Gap Materials and Their Prospects of Application”, PI A.Lushchik, permanent scientific staff 16 (PhD and DSc)

  2. ITER, • DEMO, PROTO • For industrial powerful high-temperature thermonuclear reactors it is necessary: • to increase the radiation resistance of construction materials (including dielectric ones), • to elaborate new thermo-stable blanket ceramic materials for tritium reproduction and heat removal by a flow of helium.

  3. Formation mechanisms of radiation defects 1. Impact(knock-out)mechanisms 2. Non-impact mechanisms Ionisation energy losses- decay of electronic excitations: Radiative decay Non-radiative decay Non-radiative decay Creation of Frenkel pairs and groups of defects Emission of light (luminescence) Heat release (phonon package)

  4. Our General Goals:  Search for the prospects of the suppression of the non-impact defect creation processes connected with the decay of electronic excitations (EEs) formed by 4-2000 eV-photons or fast particles in pure and doped with luminescent impurities MgO, Al2O3, SiO2, LiF etc.  Investigation of the peculiarities of defect creation in the tracks of swift ions (core and peripheral regions).  Investigation of the peculiarities of EEs and radiation processes in lithium-containing materials for breeding blanket (e.g., Li4SiO4).  Spectroscopic and thermoactivation diagnostics of materials.

  5. Experimental approach:  Complex study of electronic excitations and defects by means of low-temperature (down to 2 K) VUV-XUV spectroscopy methods.  Complex study of the origin and annealing processes of defects by means of absorption, luminescence and EPR spectroscopy methods. Methods of irradiation: Selective VUV radiation (IPUT) and synchrotron facilities atMAX-lab, Lund and HASYLAB at DESY, Hamburg:4-2000eV Single electron pulses (3 ns, 300 keV, 10-120 A/cm2) and an electron beam (1-30 keV, T = 6-500 K), IPUT. Heavyand light swift ions 238U, 198Au, 82Pb, 78Kr, 58Ni - Gesellschaft für Schwerionenforschung (GSI, Darmstadt, Germany).

  6. Tracks of swift ions in LiF

  7. Investigation of the structure of swift ion tracks in single crystals using VUV and thermoactivation spectroscopy methods

  8. Mechanisms of defect creation in the crystals with Eg < EFD: Recombination of relaxed (cold) electrons and holes Recombination of non-relaxed (hot) electrons and holes

  9. Dielectric materials with high radiation resistance(Eg< EFD) BeOSiO2ZrO2 Y2O3 MgO Al2O3 MgAl2O4 YAlO3 CaO Sc2O3 CaAl2O4 Y3Al5O12 Spectra of hole intraband luminescence (IBL) Novel experimental method of the study of the width and structure of a valence band A simplified energy-band diagram of a crystal with EFD = Ed > Eg:

  10. Luminescent defence against defect creation at the hot recombination of carriers in the materials with Ed > Eg. Crystal doping with some impurity ions causes the direct energy transfer by hot carriers to impurity centres, resulting in the excitation of impurity luminescence and the drastic decrease of the probability of hot recombination of electrons and holes. Direct energy transfer by hot holes to Cr3+ and Ge2+ centres takes place in MgO. This process causes essential difference of the excitation spectra of Cr3+ emission with respect to that for purely recombination emission of Al3+vc centres. Excitation spectra of Cr3+ and Al3+vc emissions

  11. Function mechanisms of high-melting Li4SiO4 ceramics – promising blanket materials for fusion reactors Synthesis of pure and doped Li4SiO4. Investigation of the electron-hole and interstitial-vacancy processes at 6-750 K.  Experimental modelling of the tritium release from Li4SiO4via the investigation of the release of deuterium and hydrogen from the irradiated Li4SiO4(D) and Li4SiO4(H) ceramics. Pre-irradiationand radiation traps for electrons and holes bind tritium, formed in irradiated Li4SiO4. Ceramics heating above 500 K causes the release of the tritium. TSL is observed after the irradiation by electrons (1-30 keV), X-rays (50 keV) and 9-30 eV photons Novel method of the investigation of e-h processes in Li4SiO4 (Eg 9 eV). Thermally stimulated luminescence after ceramic irradiation by 20-keV electrons at 6 K (a, = 10 K/min) or X-irradiation at 295 K (b = 2.9 K/s). Creation spectrum of the centres of photostimulated luminescence at 10 K

  12. Thank you for your attention

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