Nucl. Fusion 59 (2019) 066029 (10pp) baffled cassette with mirrors was exposed at the main wall of JET for 23,6 plasma hours. No significant degradation of reflectivity was measured on mirrors located in the ducts.Predictive modeling was further advanced. A model for the particle transport, deposition and erosion at the port-plug was used in selecting an optical layout of several ITER diagnostics. These achievements contributed to the focusing of the first mirror research thus accelerating the diagnostic development. Modeling requires more efforts. Remaining crucial issues will be in a focus of the future work of the FM SWG.

No abstract

The efficient and reliable control and monitoring of the quality of the optical properties of mirrors is an open problem in laboratory plasmas. Until now, the measurement of the reflectance of the first mirrors was based on the methods that require additional light calibration sources. We propose a new technique based on the ratio of the red- and blue-shifted emission signals of the reflected hydrogen atoms which enables the in situ measurement of the spectral reflectance of metallic mirrors in low-density Ar-H or Ar-D plasmas. The spectral reflectance coefficients were measured for C, Al, Ag, Fe, Pd, Ti, Sn, Rh, Mo, and W mirrors installed in the linear magnetized plasma device PSI-2 operating in the pressure range of 0.01-0.1 Pa. The results are obtained for the H line using the emission of fast atoms induced by excitation of H atoms through Ar at a plasma-solid interface by applying a negative potential U = -80, …, -220 V to the mirror. The agreement between the measured and theoretical data of reflectance is found to be within 10% for the investigated materials (except for C). The spectra also allow us to efficiently determine the material of the mirror.

No abstract

A conservative engineering model of the impurity deposition on the diagnostic mirrors is proposed. The model is applied to analyze numerically the effect of protecting structures (ducts) with and without baffles in the conditions of the ITER main chamber. It was found that the gross deposition rate in the ducts with baffles, if they are long enough, can be made by an order of magnitude smaller than that in the ducts of an equivalent length without baffles. This model prediction can be tested experimentally. The calculated efficiency of the impurity flux attenuation depends strongly on the model assumption: the variation between the ‘best’ and ‘worst’ cases reaches two orders of magnitude. A case study with the real 3D geometry of one specific diagnostic, core-CXRS, is conducted. For this particular geometry, the effect of baffles is nearly marginal; that is, this is not a universal solution.