Chemical vapor deposition diamond window as vacuum and tritium confinementbarrier for fusion application

A pressure resistant polycrystalline chemical vapor deposition (CVD) diamon d disk for a microwave window is used for a vacuum and a tritium confinemen t boundary in fusion applications. A pressure test of a CVD diamond window disk (2.25 mm in thickness and 100 mm in diameter) was carried out. It was demonstrated that the diamond window tolerated 1.0 MPa (10 atm) in the plen um. The displacement of the window center for both the growth and the nucle ation side on the unpressurized side is 40 +/-1 and 41 +/-1 mum, respective ly, at the pressure of 1.0 MPa, and these values agree well with those calc ulated. No damage in the disk and the braze, and no vacuum leakage in the a ssembly was observed. This result demonstrates that the diamond window asse mbly could tolerate up to 1.45 MPa. It was experimentally proved that the d iamond window satisfied the safety requirement of 0.5 MPa resistance for th e vacuum and the tritium confinement boundary of an International Thermonuc lear Experimental Reactor. The design prospect for the diamond window of th e electron cyclotron heating and current drive system is also discussed, ba sed on the stress analysis using the ABAQUS code. (C) 2000 American Institu te of Physics. [S0034-6748(00)01911-0].