We have investigated the pre-baking effect for the outgassing property of a titanium alloy. The outgassing rate of the order of 10-12 Pa · m · s-1 is obtained after the modest baking condition, e.g. 100°C × 3 h. This value is lower than that of standard vacuum materials by two orders of magnitude after the ordinary baking condition, e.g. 180°C ×48 h. From the Arrhenius plots of the outgassing rate after the baking at 150°C × 20 h, the activation energy Eq for the outgassing is 0.45 eV. This value is smaller than that for the hydrogen diffusion dissolved in bulk titanium. It is interpreted that the very low hydrogen content occurs at the surface oxide layer by the modest pre-baking treatment.
