Wide-range evaluation of the deposition layer thickness distribution on the first wall by reflection coefficient measurements

Motojima, G.; Yoshida, Naoki; Masuzaki, S.; Sakamoto, R.; Tokitani, M.; Tanaka, Hirohiko; Murase, T.; Nagata, Daisuke; Matsumoto, Kenji; Miyamoto, M.; Yajima, Miyuki; Sakamoto, M.; Yamada, H.; Morisaki, T.

doi:10.1016/j.nme.2017.04.018

Cited by 12 publications

(10 citation statements)

References 5 publications

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“…Depositions on these panels also provide useful informations about the material migrations over the first wall components interacting with the plasma. Measurements of the optical reflection of the Red, Green and Blue (RGB) colors have provided such informations in Large Helical Device [6]. Using this compact color analyzer, whole W7-X plasma vessel metal surfaces along the torus were mapped by taking ca.…”

Section: Optical Reflection Measurementsmentioning

confidence: 99%

Erosion and deposition investigations on Wendelstein 7-X first wall components for the first operation phase in divertor configuration

Dhard

Mayer

Brezinsek

et al. 2019

Fusion Engineering and Design

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In the stellarator Wendelstein 7-X with its twisted 3D magnetic field geometry, studies of material migration with respect to first wall components become very important in view of the envisioned long-pulse operation. A variety of erosion/deposition samples were installed on the plasma-facing components exposed at three different nominal heat load levels between 0.1 and 10 MW/m 2. After the first successful operation phase in divertor configuration, all the probes at higher and lower load levels were removed, whereas at the intermediate load levels, 352 out of 30 000 screws have been exchanged at selected locations along the toroidal and poloidal directions. The exchanged probes have been analyzed by various measurement techniques. At the higher load levels where the probes were installed within the divertor, heavy erosion has been observed presumably at the strike line positions. Both, erosion and deposition phenomena have been found on the screw heads. The optical reflection measurement profile of the whole plasma vessel show the deposition patterns at similar locations in all the five modules. At the low load level, the Siwafer probes are under investigation.

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Section: Optical Reflection Measurementsmentioning

confidence: 99%

Erosion and deposition investigations on Wendelstein 7-X first wall components for the first operation phase in divertor configuration

Dhard

Mayer

Brezinsek

et al. 2019

Fusion Engineering and Design

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“…This model considers the deposition thickness to be a function of the reflection rate (see section 2.3 for details). The compatibility of the single-layer model has been confirmed via a composition with specimen analysis results for the LHD [7]. The material composition of the plasma-facing components in W7-X is similar to that in the LHD.…”

Section: Process Used For Evaluating Thickness Distribution Of Deposition Layermentioning

confidence: 69%

“…In the second step, the RGB values were converted to a reflection rate using a linear relation. Ellipsometric measurements, which measured surface reflection rate, of specimens irradiated by LHD plasmas showed a linear relation between RGB values and the reflection rate [7]. Therefore, a linear relation was adopted in this study.…”

Section: Process Used For Evaluating Thickness Distribution Of Deposition Layermentioning

confidence: 99%

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In-vessel colorimetry of Wendelstein 7-X first wall components: variation of layer deposition distribution in OP1.2a and OP1.2b

Motojima¹,

Masuzaki²,

Dhard

et al. 2020

Phys. Scr.

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A colorimetry study of the first wall panels in the Wendelstein 7-X (W7-X) was carried out using a compact color analyzer after Operation Phases OP1.2a and OP1.2b, in which graphite test divertor units were used, to estimate the wide-range distribution of the deposition layer. The color analyzer was used to measure the intensities of the Red, Green and Blue (RGB) channels, which correspond to reflection rates, for all first-wall panels after OP1.2a and OP1.2b. A significant difference in the RGB values was found between OP1.2a and OP1.2b. The color pattern on the panels was roughly the same for all the five toroidal modules of W7-X. The deposition layer thickness was estimated from the RGB values using a single-layer model. A thin average deposition layer (10±6 nm) was estimated for OP1.2a. On the other hand, a thicker average deposition layer (25±8 nm) was estimated for OP1.2b.

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“…The neutron generation in the vacuum vessel of LHD produced radioactivated components in the torus hall. In the LHD vacuum vessel, more than 4,000 armor tiles are covering the inner wall and have been irradiated by high flux fast neutron 7,8) . These armor tiles can be damaged by the high heat and particle fluxes of high temperature plasma, which are normally confined by the magnetic field but can be fluctuated by the experimental conditions.…”

Section: Introductionmentioning

confidence: 99%

The Evaluation of a Simple Measurement Method using NaI(Tl) Scintillation Survey-Meter for Radiation Safety Management of Radioactivated Armor Tiles of LHD Vacuum Vessel

Kobayashi

Suzuki

Saze

et al. 2021

Radiat. Saf. Manage.

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In this study, the application of a simple measurement method using NaI(Tl) scintillation survey-meter to detect the gamma-rays in the armor tiles of LHD vacuum vessel exposed to fast neutrons during deuterium plasma experiments was evaluated to control the occupational exposure for the storage of huge numbers of the armor tiles. The gamma-ray spectrometry for an activated armor tile by high-purity germanium detector (HPGe) showed the gamma-ray peaks from 58 Co, 54 Mn and 60 Co. The detection efficiencies of these nuclides for HPGe were evaluated by PHITS to estimate the concentrations of these nuclides. The radiation transport model for HPGe in PHITS were validated by the gamma-ray measurements for sealed gamma-ray sources. Then, the detection efficiencies of these nuclides for NaI(Tl) scintillation survey-meter were also evaluated by the same manner using PHITS. The predicted dose rate of the activated armor tiles in NaI(Tl) scintillation survey-meter was consistent with the actual measurement. The predicted count rate in NaI(Tl) scintillation survey-meter for 60 Co, which will be a deterministic nuclide in the armor tile due to longer half-life, in the clearance level was sufficiently higher than the minimum detectable count rate of NaI(Tl) scintillation survey-meter with a simple shielding for environmental radiation.

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Wide-range evaluation of the deposition layer thickness distribution on the first wall by reflection coefficient measurements

Cited by 12 publications

References 5 publications

Erosion and deposition investigations on Wendelstein 7-X first wall components for the first operation phase in divertor configuration

Erosion and deposition investigations on Wendelstein 7-X first wall components for the first operation phase in divertor configuration

In-vessel colorimetry of Wendelstein 7-X first wall components: variation of layer deposition distribution in OP1.2a and OP1.2b

The Evaluation of a Simple Measurement Method using NaI(Tl) Scintillation Survey-Meter for Radiation Safety Management of Radioactivated Armor Tiles of LHD Vacuum Vessel

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