Fig. 1. (a) Conceptual diagram of accelerator beam window. The target that produces the secondary particles is often placed in a target station filled with helium or nitrogen, and the accelerator vacuum and the target station are separated by a thin sheet of metal called a “beam window”. (b) Beam window at the J-PARC neutrino facility. Helium gas flows through a gap between two 0.4mm thick domed high-strength Ti-64 alloys to cool the heat generated by the beam. It is surrounded by an inflatable seal under pressure for remote handling. The maximum expected radiation damage to the Ti-64 window is approximately 2 dpa/year. (c) The microscope image of Ti-64 shows a mixture of dominant primary α(HCP)-phase and inter-granular β(BCC)-phase matrix. The ω-phase is fine precipitation with a Hexagonal structure in the mother β-phase with coordination relationships [0001]ω//[111]β, (11𝟐𝟐􀴥0)ω //(110)β.

Fig. 1. (a) Conceptual diagram of accelerator beam window. The target that produces the secondary particles is often placed in a target station filled with helium or nitrogen, and the accelerator vacuum and the target station are separated by a thin sheet of metal called a “beam window”. (b) Beam window at the J-PARC neutrino facility. Helium gas flows through a gap between two 0.4mm thick domed high-strength Ti-64 alloys to cool the heat generated by the beam. It is surrounded by an inflatable seal under pressure for remote handling. The maximum expected radiation damage to the Ti-64 window is approximately 2 dpa/year. (c) The microscope image of Ti-64 shows a mixture of dominant primary α(HCP)-phase and inter-granular β(BCC)-phase matrix. The ω-phase is fine precipitation with a Hexagonal structure in the mother β-phase with coordination relationships [0001]ω//[111]β, (11𝟐𝟐􀴥0)ω //(110)β.