Design of the ITER VUV edge imaging spectrometer and R&D for the rotary motional vacuum feed-through

Abstract The ITER vacuum ultraviolet (VUV) spectrometer is aimed at monitoring impurity ion species in plasmas, and it consists of three systems, core survey, edge imaging, and divertor spectrometers depending on positions. In the VUV edge imaging spectrometer, a field mirror and a collimation mirror are used for imaging of the light onto the entrance slit of the VUV imaging spectrometer. To optimize the design of the field mirror box in the ITER port plug, the mirror box mock-up was developed to test installation and alignment. Especially, the mirror alignment using a special tilt stage was tested, and the motional feed-through with a double bellows was developed for the shutter operation. The preliminary qualification test for this rotary motional vacuum feed-through was performed to meet the functional requirement of ITER mechanical feed-through. Leak-tightness for over 15,000 times (larger than operation times) of 360 rotation and backward motion was tested for 1 N.m loading condition to the axis rod of the feed-through. In the test, the vacuum inside of the feed-through was monitored, and the feed-through showed good rotation function and leak-tightness during test.