Aberrations in preliminary design of ITER divertor impurity influx monitor

Yatsuka

Ishikawa

et al. 2023

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The Japan domestic agency (JADA) is responsible for procuring five diagnostic systems for ITER: the microfission chamber (MFC), poloidal polarimeter (PoPola), edge Thomson scattering (ETS), divertor impurity monitor (DIM), and divertor infrared thermography (IRTh) systems. Components of these systems that will be installed in high radiation zones must undergo radiation resistance tests to ensure reliability. The JADA diagnostic group has been conducting gamma ray irradiation experiments on diagnostic components at QST since 2018. The MFC is a neutron diagnostic system that uses uranium fission chambers, the mineral-insulated cables of which were evaluated for corrosion resistance. In-situ observations of the MFC preamplifier have been launched. The PoPola provides the plasma current profile by detecting the polarizations of far-infrared laser beams at their inlets and outlets. Irradiation tests confirmed the durability of PoPola piezo actuators. The ETS is a laser-aided diagnostic to measure electron temperature and density in plasmas from scattered spectra. Laser-induced damages to the optical elements caused by irradiation were investigated. The DIM is a spectroscopic system having a wavelength range of 200 nm to 1000 nm. The effects of irradiation on optical devices, metal mirrors, and radiation-resistant optical fibers were investigated. The IRTh is an infrared thermography system to observe the surface temperature of the divertor. The optical elements and electrical devices of the IRTh have undergone irradiation experiments. The progress of the gamma ray irradiation experiments on the ITER diagnostic systems from JADA are reported.

Section: Dimmentioning

confidence: 99%

Progress of Gamma Ray Irradiation Experiments on ITER Diagnostics from JADA

Yatsuka

Ishikawa

et al. 2023

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“…The preliminary design of the DIM employs achromatic lenses in ISs and PCs and lens groups for spectroscopes in PCs [3]. Silica (SiO 2 ), fluorite (CaF 2 ), and Li-CAF (LiCaAlF 6 ) were chosen as vitreous materials for the irradiation experiments.…”

Section: Gamma Irradiation On Lens Materialsmentioning

confidence: 99%

“…observed is guided from the front-end optical system in the VV through ISs to PCs by using mirrors. The DIM system specifications are 50 mm for spatial resolution and 1 ms for time resolution, thus, very high optical performance is required, such as increasing the yield of light observed and suppressing aberration [3]. The DIM system observes 200 -400 nm UV light, which is affected by the reduction of light transmittance due to the formation of a color center under a high gamma ray radiation environment.…”

Section: Introductionmentioning

confidence: 99%

Gamma Ray Irradiation Effects on Optical Elements of ITER Divertor Impurity Monitor

Oikawa

Ogawa

et al. 2019

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The ITER divertor impurity monitor (DIM) is a diagnostic system that directly observes 200-1000 nm light emissions from nuclear fusion plasma. Because the DIM observes a wide range of light from infrared to ultraviolet using a single optical system, high optical performance, such as spatial resolution and aberration, is required for the DIM optical elements. The DIM must be highly robust against external environmental factors, such as temperature, humidity, vibration, and magnetic field. Components having high radiation resistance must be used because of the high radiation environment in ITER. In this study, DIM optical elements installed in the interspaces and the port cells are investigated because gamma ray irradiation can impact their optical performance. The irradiation experiments were performed at QST's gamma-ray irradiation facilities in Takasaki. The attenuation of transmittance due to gamma irradiation were evaluated for silica, fluorite, and LiCaAlF 6 as the glass material in the spectrometers to be installed in the port cell. The influence of irradiation on silica polka dot beam splitters was found to be negligible; however, the transmittance of high OH concentration fibres for measuring UV light decreased significantly due to irradiation and will thus require countermeasures. The information necessary for proceeding with the ITER DIM design was obtained from these experimental results.

“…The preliminary optical design for DIM has been performed [6]. According to this design, the mechanical design of the mirror box was developed.…”

Section: Conditionsmentioning

confidence: 99%

Preliminary Thermal Analysis of Critical Components in ITER Lower Port #02

Maruyama

Ogawa

et al. 2016

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ITER diagnostic lower ports will be used to exchange divertor cassettes and install diagnostic systems. Invessel components of diagnostic lower port #02 (LP#02) will be mounted on a divertor cassette and a support structure, so-called a diagnostic rack, to be removed and reinstalled collectively. Japan Domestic Agency is responsible for procurements of an integration engineering of LP#02 and a divertor impurity monitor, a main tenant system in LP#02. This paper presents preliminary thermal analyses for two critical components in LP#02, the diagnostic rack and a mirror box on the divertor cassette, which will be exposed to the harsh thermal load from plasma. Realistic fabrication methods for cooling the diagnostic rack and a required cooling path layout of the mirror box on the divertor cassette have been assessed to implement the preliminary design from the viewpoint of thermal analysis.