Divertor impurity-influx monitor for ITER; Spectral throughput measurement on an optical prototype for the upper port and optimization of viewing chords based on computerized tomography

ITERダイバータ不純物モニター; 試作光学系に対する分光スループット計測

岩前 敦; 杉江 達夫; 小川 宏明; 草間 義紀

Iwamae, Atsushi; Sugie, Tatsuo; Ogawa, Hiroaki; Kusama, Yoshinori

We have developed a spectroscopic diagnostics system in ultraviolet and visible wavelength regions for monitoring ITER divertor plasmas. An equivalent-size prototype of the optical components for the upper port-viewing fan array chords has been assembled as a system to measure spectral light throughput coefficient (tendu). Collisional-radiative models for He and C are used to estimate the emission line intensities of helium ash and carbon impurity ions in a divertor plasma of a burning plasma. For the measurement of , the estimated line intensity of C =6-7 meets the time resolution of ITER requirement. A numerical simulation of the computerized tomographic (CT) reconstruction technique has been applied to the divertor plasma region. A Gaussian-type intensity model function with 100 mm (full-width-at-half-maximum) of the impurity emission observed by means of various pairs of fan array-viewing chords is applied based on the CT reconstructs. With the optimized pair of the upper port and the higher gap viewing chords resolve the model function with reasonable resolution. We measure the reflection of the surfaces of carbon-fiber-composite and tungsten blocks, which consist of the plasma-facing divertor target plate and the dome. The reflection of the surface of the tungsten divertor material at H 656.28 nm is 23%, sandblasting the tungsten surface reduces direct reflectance less than 0.7%.