Abstract
Radiation damage due to synchrotron radiation has been studied at the boundary of cooling water and metal related to vacuum chambers: oxygen free copper (OFC). The damage was evaluated by measuring the dissolved ion concentration in water, sampled from the pure water circulating system with a sample pipe (10 mm in inner diameter and 1 mm in thickness), irradiated by synchrotron radiation with photons (40–700 keV) of the order of 10 16 photons (MeV mA s) -1 in the TRISTAN e +e - colliding ring (bending radius of 246 m and beam energy of 29 GeV). OFC with an irradiated surface area of 10 mm 2 showed a Cu ion concentration of 6 mg 1 -1 after 1.3 A h irradiation (800 h operation, 5.3 x 10 20 photons mm -2). The ion concentration showed an increasing rate of t 1 3 − 1 2 before 500 h. After 500 h operation, it was roughly proportional to t. The time dependence of the concentration of the non-irradiated sample was t 1 3 before 10 3 h. The concentration increased from 0.01 before 10 3 h to 1 mg l -1 after 10 3 h. The relationship between the free energy of formation and the estimated dissolved ion concentration of OFC together with the one of aluminum alloys, a 10 μm thick silicon dioxide film inside an Al pipe, and stainless steel 316L at 10 A h (the dose of the materials ranging from 4.1 to 5.8 x 10 21 photons mm -2) gives that the higher the free energy of formation, the lower the dissolved ion concentration. Therefore, to obtain a radiation resistant surface, the stable oxide (with higher free energy of formation) should be selected.
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