Inverse radiation problem with infrared images to monitor plasma-facing components temperature in metallic fusion devices

Talatizi, C.; Aumeunier, Marie-Hélène; Rigollet, Fabrice; Bohec, M. Le; Gerardin, J.; Gaspar, J.; Niliot, Christophe Le; Herrmann, A.

doi:10.1016/j.fusengdes.2020.111867

Cited by 9 publications

(7 citation statements)

References 9 publications

(10 reference statements)

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“…This upgrade could contribute to the comparison especially for He discharges where long discharges have been performed with high surface temperatures reaching up to 1000 °C. Then other approach is under development for the IR processing based on inverse method to have a better evaluation of the reflected light which could perturbate the IR inversion in the cold area [17].…”

Section: Fig 2amentioning

confidence: 99%

“…Measurements of the emissivity evolution with the temperature is foreseen on the different areas (low and high emissivity) to take into account this variation in the IR processing performed in the TEDDY. This upgrade could contribute to the comparison especially for He discharges where long discharges have been performed with high surface temperatures reaching up to 1000 • C. Then other approach is under development for the IR processing based on inverse method to have a better evaluation of the reflected light which could perturbate the IR inversion in the cold area [18]. This upgrade will improve the background heat flux estimated with the IR inversion (overestimated with at least factor two in comparison to the TC, FBG and bolometry measurements) and could modify the estimated λ t q from the IR data.…”

Section: Heat Load Intensity and Decay Length At The Targetmentioning

confidence: 99%

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Divertor power loads and scrape off layer width in the large aspect ratio full tungsten tokamak WEST

et al. 2021

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WEST is a full W tokamak with an extensive set of diagnostics for heat load measurements especially in the lower divertor. It is composed by infrared (IR) thermography, thermal measurement with thermocouples (TC) and fiber Bragg grating (FBG) embedded few mm below the surface and flush mounted Langmuir probes (LP). A large database including different magnetic equilibrium and input power is investigated to compare the heat load pattern (location, amplitude of the peak and heat flux decay length) on the inner and outer strike point regions as function of the continuous progress achieved in WEST : from the first ohmic diverted plasma (obtained during the second experimental campaign C2 in 2018) up to the high power (up to 8 MW total injected) and high energy (up to 90 MJ injected energy in lower single null configuration) steady state experiments performed in the last experimental campaign (C4 in 2019). Concerning the peak location, a good agreement (<1cm) is obtained between thermal inversions and flush-mounted LP measurements. The peak heat flux from the whole set of diagnostics is in good agreement and mainly in the ± 20% range, while the heat flux decay length reported on the target shows significant discrepancy between diagnostics and location in the machine (± 40% range). Despite such discrepancy, heat flux decay length at target is found to scale mainly with the magnetic flux expansion through the variation of the X-point height, as expected. The improved plasma performances achieved during C4 enabled to reach significant heat load in the divertor, up to 6 MW/m² with 4 MW of additional heating power showing the capability to reach the ITER relevant heat load (10 MW/m² steady state) with about 7 MW of additional power in L-mode discharge. The heat load distribution is clearly asymmetric with a 3/4 and 1/4 distribution on the outer and inner strike point region respectively for the parallel heat flux close to the 2/3 -1/3 commonly observed in forward-B divertor configuration.

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Section: Fig 2amentioning

confidence: 99%

Section: Heat Load Intensity and Decay Length At The Targetmentioning

confidence: 99%

Divertor power loads and scrape off layer width in the large aspect ratio full tungsten tokamak WEST

et al. 2021

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“…In addition to the work carried out on emissivity correction, some methods have been developed to estimate parasitic reflection that occurs during temperature measurement in highly reflective scenes 17,18 at high temperatures. This method are based on radiation models 19 .…”

Section: Active Thermo-reflectometry For Absolute Temperature Measure...mentioning

confidence: 99%

Active thermo-reflectometry for absolute temperature measurement by infrared thermography on specular materials

Lafargue-Tallet

Vaucelle²,

Caliot

et al. 2022

Sci Rep

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Knowledge of material emissivity maps and their true temperatures is of great interest for contactless process monitoring and control with infrared cameras when strong heat transfer and temperature change are involved. This approach is always followed by emissivity or reflections issues. In this work, we describe the development of a contactless infrared imaging technique based on the pyro-reflectometry approach and a specular model of the material reflection in order to overcome emissivities and reflections problems. This approach enables in situ and real-time identification of emissivity fields and autocalibration of the radiative intensity leaving the sample by using a black body equivalent ratio. This is done to obtain the absolute temperature field of any specular material using the infrared wavelength. The presented set up works for both camera and pyrometer regardless of the spectral range. The proposed method is evaluated at room temperature with several heterogeneous samples covering a large range of emissivity values. From these emissivity fields, raw and heterogeneous measured radiative fluxes are transformed into complete absolute temperature fields.

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“…In this paper, two direct models are tested and compared: a simplified model so-called Sec-tore (section 3.2.2) and a reduced model so-called RADIOS (section 3.3.3). In [7], the inversion method is tested in an inverse crime situation meaning that the synthetic data used to replace the experimental data come from the same forward model used for inversion, with an additive Gaussian white noise.…”

Section: Generating Ir Imagesmentioning

confidence: 99%

“…Nevertheless, as proven in [7], the temperature estimation becomes a linear problem by considering the radiance parameters L 0 (T) (related to the temperature T via the Planck function) in equation (3). Then, the radiance parameters can be directly computed with equation (5):…”

Section: Parameters Estimation Problemmentioning

confidence: 99%

Solving the infrared reflections contribution by inversion of synthetic diagnostics: First results on WEST

Talatizi

Aumeunier

Rigollet

et al. 2021

Fusion Engineering and Design

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Inverse radiation problem with infrared images to monitor plasma-facing components temperature in metallic fusion devices

Cited by 9 publications

References 9 publications

Divertor power loads and scrape off layer width in the large aspect ratio full tungsten tokamak WEST

Divertor power loads and scrape off layer width in the large aspect ratio full tungsten tokamak WEST

Active thermo-reflectometry for absolute temperature measurement by infrared thermography on specular materials

Solving the infrared reflections contribution by inversion of synthetic diagnostics: First results on WEST

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