Influence of the Surface-Laver Structure in Outgassing and Photo-Irradiation Effect

SURFACE LAYER STRUCTUREThe surfacw LAYER structure of aluminum alloys which are mainconstructional materials of large accelerators and storage rings已开始投资。following results已受污染。(1)In case of electrochemical polishing，initial oxide layer formed on a magnesium-containing aluminum alloy has an amorphous hydroxide，它dehydrates during vacuum heating. Radial distribution function obtained from electrondiffraction revealed the structure being <gamma>- al_2_3 . (2) Short-circuit diffusion of magnesiumthrough the oxid occured and MgO phase appeared at the top surface at a low temperature of 150 C asthe baking temperature.2. INFLUENCE OF the SURFACE LAYER STRUCTURE ON OUTGASSINGThermal描述spectrum measured to investigate an influence of the surface layer structure on outgassingcharacteristic and a baking effect. The results obtained are follows. (1) When The surfacepolished electrochemically was heated，rapid gas evolution occured due to thermal decomposition of the surface layer. (2) the oxidizedsurface of a 2.3% aluminum-magnesium alloy may adsorb gases(h_2o, h_2, co_2) except for CO when(3) A correlation between the surface layer structure and outgassing characteristichas been observed.characteristic has been observed.3. OUTGASSING DURING PHOTO-IRRADIATION AND A ROLESURFACE LAYER STRUCTUREA照片-irradiation experiment was undertaken to investigate amechanism of outgassing and to find an influence of the surface layer structure. the following1 . Outgassing rate depends on the surface which was prepared with different Outgassing rate depends on the surface which was prepared with differenttreatments, that is, anodic oxidation, electrochemical polishing,and thermal oxidation (500c, 10torr pure oxygen,1h).描述产生的规范化by photon number(2)影响surface layer结构和一个化学nature(a degree of hydrate) on outgassing character has been found experimenally

1. SURFACE LAYER STRUCTUREThe surfacw layer structure of aluminum alloys which are main constructional materials of large accelerators and storage rings has been investigated. The following results have been obtained. (1) In case of electrochemical polishing, an initial oxide layer formed on a magnesium-containing aluminum alloy has an amorphous hydroxide, and it dehydrates during vacuum heating. Radial distribution function obtained from electron diffraction revealed the structure being <gamma>-Al_2O_3. (2) Short-circuit diffusion of magnesium through the oxid occured and MgO phase appeared at the top surface at a low temperature of 150゜C as the baking temperature.2. INFLUENCE OF THE SURFACE LAYER STRUCTURE ON OUTGASSINGThermal desorption spectrum was measured to investigate an influence of the surface layer structure on outgassing characteristic and a baking effect. The results obtained are as follows. (1) When the surface polished electrochemically was heated, rapid gas evolution occured due to thermal decomposition of the surface layer. (2) The oxidized surface of a 2.3% aluminum-magnesium alloy may adsorb gases(H_2O,H_2,CO_2) except for CO when exposed to air. (3) A correlation between the surface layer structure and outgassing characteristic has been observed.characteristic has been observed.3. OUTGASSING DURING PHOTO-IRRADIATION AND A ROLE OF THE SURFACE LAYER STRUCTUREA photo-irradiation experiment was undertaken to investigate a mechanism of outgassing and to find an influence of the surface layer structure. The following results were obtained. (1) Outgassing rate depends on the surface which was prepared with different treatments,that is, anodic oxidation,electrochemical polishing, and thermal oxidation (500゜C,10 Torr pure oxygen,1h). Desorption yield normalized by photon number changes in order of the above order. (2) Effect of the surface layer structure and a chemical nature(a degree of hydrate) on outgassing character has been found experimenally.