Development of New Vacuum Window Seal for ITER Optical Diagnostics

Abstract

Many windows will be required on ITER for optical, infrared, and microwave diagnostics. The diagnostic transmission systems will be incorporate labyrinths in port shielding blocks and so the windows will not be located in high levels of neutron and gamma radiation. Nevertheless it is necessary for the window seals to be able to withstand pressure transients, temperature excursions and mechanical shocks which are significantly different from those experienced on present-day tokamaks. The objective of the R&D is to develop suitable vacuum seal for ITER diagnostic windows concerning to mechanical capability. The main required features of the window specification for ITER diagnostics are the following. (1) Vacuum Seal:He Leak < 1 x 10^-10 Pa m³/s, (2) Capacity to Resist Inner Pressure Rise:> 5 atm, (3) Temperature;> 200 °C, (4) Temperature ramp rate:> 20 °C/hr, (5) Temperature gradients across windows:3∼4 points for each surface of window, (6) Mechanical acceleration of structure:> 15g, duration 10ms, 1000cycles., (7) Optical property