K. Izui

In-situ observation of damage evolution in SiC crystals during He+ and H2+ dual-ion beam irradiation

Using the new system of in-situ observation during dual-ion beam irradiation recently developed at JAERI, effects of simultaneous 12 keV He + and 15 keV H 2 + ion irradiation at room temperature on the formation of bubbles in SiC crystals were examined. It was found that hydrogen atoms gave quite a different effect on the formation of helium bubbles according to whether they were pre-injected or simultaneously injected with the helium atoms. Bubble formation is enhanced by pre-injection of hydrogen atoms, whereas it is little influenced by simultaneous injection of hydrogen atoms and helium atoms.

In-situ observation of damage evolution in TiC crystals during helium ion irradiation

Abstract In-situ observations were performed on bubble formation and growth in TiC during 20 keV helium ion irradiation over the wide range of irradiation temperatures from 12 to 1523 K. No amorphization occurred over this temperature range. The bubble densities and sizes were almost independent of irradiation temperatures from 12 to 1273 K. Remarkable growth and coalescence occurred during irradiation at high temperature above 1423 K and during annealing above 1373 K after irradiation.

In situ observation of the damage evolution in ß-SiC crystals during helium and hydrogen dual-ion irradiations

Abstract In situ observations were performed on the bubble formation in s-SiC crystals during three kinds of ion irradiations: (a) single helium ion irradiation, (b) hydrogen ion pre-irradiation followed by helium ion irradiation, and (c) simultaneous irradiation of helium and hydrogen ions. The bubble formation and growth in s-SiC, at the same level of irradiation fluences, were remarkably depressed in the case of simultaneous helium- and hydrogen-ion irradiations compared to the other two cases. The effect of simultaneous ion irradiation on the bubble formation is discussed with respect to the diffusion of the incident ions and the number of nucleation sites for helium bubbles.

In-situ observation of the migration and growth of helium bubbles in aluminum

Abstract Brownian motion of helium bubbles, their disappearance, and coalescence in high purity aluminum were demonstrated in real time by electron microscopy and the recording of these whole processes on VTR. It was experimentally established for the first time that the mean square of the migration distance of the bubble during the time duration, t , is proportional to t at least for t ≥ 1 min. The growth of the bubble was caused by the coalescence between bubbles during Brownian motion and also by annealing at higher temperature unless the coalescence takes place. A dependence of the diffusivity of the bubble on its diameter and a rapid formation of new bubble by the coalescence of two bubbles seem to be supported through the surface diffusion of aluminum on the bubble surface.

Evolution of structural damage in aluminum alloys irradiated with helium ions

Abstract Microstructural evolution in pure Al and alloys during He+ ion irradiation and subsequent annealing was examined by in situ observations. Irradiation was performed over a wide temperature range from 17 to 473 K with fluxes of 3 × 1017 and 6 × 1016 m−2 s−1. In pure Al and alloys irradiated at lowtemperature and subsequently annealed, the number density of interstitial loops and bubbles is higher for a higher ion flux. For high temperature irradiation, the corresponding densities are higher at a lower flux irradiation. Also, the density of bubbles depends largely on the irradiation temperature for high flux irradiation of pure Al and alloys doped with 0.1 at.% Si or Mg.

In-situ observation of structural changes in aluminum during He+ and H2+ dual-ion beam irradiation

Abstract The dual-ion beam irradiation facility at JAERI, which allows in-situ observation, was used to investigate the main factors influencing bubble formation in aluminum. Irradiation employed both (1) single ion beam irradiations with He+ and H2+ and (2) simultaneous He+ and H2+ ion irradiations at room temperature. It was found that both vacancy production rate and gas atom injection rate were important in determining the bubble nucleation, number density and sizes.