チタン合金の低放射化真空材料としての可能性について

概要

論文の詳細を見る
In the field of high intensity beam accelerators, activation of the vacuum components has been a big problem. Until now, such materials as aluminum alloys and pure titanium have been used as low activation vacuum materials. However, the problem is that they have lower mechanical strength than stainless steel, which is generally used as a vacuum component material. As a candidate for a low activation vacuum material with high mechanical strength, we measured the radioactivity and vacuum characteristics of titanium alloy Ti-6Al-4V. For the radioactivity characteristics, we carried out proton beam irradiation experiments at 200 and 400 MeV beam energy. As a result, the dose rate of Ti-6Al-4V was found to decrease faster than that of stainless steel. Further, it was found that the relatively short half-life nuclides 44mSc(t1/2=58 h), 46Sc(t1/2=43 h), and 48V(t1/2=15d) are generated. It means that Ti-6Al-4V is a low activation material. To characterize the vacuum performance, the hydrogen concentration in a bulk of Ti-6Al-4V was measured. As a result, by performing the vacuum firing at 700℃ for 9 hours, the hydrogen concentration can be reduced to about 1 ppm, which is 1/70 of the untreated case. These experimental results suggest that it is possible to use Ti-6Al-4V as an ultra-high vacuum material with low activation.