Optical performance verification of the Impurity Influx Monitor (Divertor) for ITER

Iwamae, Atsushi; Ogawa, Hiroaki; Sugie, Tatsuo; Kusama, Yoshinori; Kasai, Satoshi*; Katsunuma, Atsushi*; Takeyama, Norihide*

We report the performance test of the trial optics of the Impurity Influx Monitor (Divertor) for ITER. The emission from the divertor plasma in UV and visible wavelength region will be collected with the head optics and the Cassegrain telescope. The focused light from the plasma is transmitted by the optical fiber to the spectrometers. Since the head optics is irradiated by the high fluxes of the -ray, neutron and high energy particles from the core plasma, we use molybdenum and aluminum metallic mirrors in the head optics. These mirrors are mounted in a module equipped with cooling channels to remove the nuclear heat. We have built metallic mirrors, a Cassegrain telescope, a micro-lens array and optical fiber light distributors for the optical performance test on an ITER-equivalent geometric scale. We expand the field of view along the magnetic field direction with introducing the micro-lens array in front of the fiber core. The light collection efficiency increased by three times at maximum with the micro-lens array. We have evaluated the line-of-sight integrated intensity of the impurity emission line in the divertor plasma with the collisional-radiative model. The estimated intensity of C IV line (581 nm) will be detectable in several lines of sight with the present designed optical system.