Infrared thermography in metallic environments of WEST and ASDEX Upgrade

Aumeunier, M.-H.; Gerardin, J.; Talatizi, C.; Bohec, M. Le; Yaala, M. Ben; Marot, L.; Loarer, T.; Mitteau, R.; Gaspar, J.; Rigollet, Fabrice; Courtois, X.; Houry, M.; Herrmann, A.; Faitsch, M.; Team, West

doi:10.1016/j.nme.2020.100879

Cited by 21 publications

(13 citation statements)

References 13 publications

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“…The deposited heat flux is estimated from these data using the TEDDY code [11]. The main limitations in this inversion can result from both the reflected radiance at low surface temperature [12] and the non-uniform emissivity observed on the PFCs [13]. To overcome these difficulties a procedure has been implemented in the TEDDY code to determine the effective emissivity and background reflections (supposed constant during the discharge) using the IR measurements just prior the plasma and the TC measurements [11].…”

Section: Heat Load Diagnostics Set-up and Heat Flux Databasementioning

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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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: Heat Load Diagnostics Set-up and Heat Flux Databasementioning

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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“…This toroidal pattern was observed in all misaligned PFUs measured with or without chamfer. The increase observed at the trailing edge (~30 mm) is due to the chamfer, which is a cold area shadowed from the plasma, prone to redeposition, and seen by the VHR with an inclination of the surface that are expected to enhance the emissivity [28] during the measurements (see Figure 6). In addition, it is possible to see the variation between extrapolated and measured emissivity.…”

Section: Poloidal Leading Edgementioning

confidence: 99%

Interpretation of temperature distribution observed on W-ITER-like PFUs in WEST monitored with a very-high-resolution IR system

Grosjean

Aumeunier

Corre

et al. 2021

Fusion Engineering and Design

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“…It is important to stress that the conducted energy plotted here have no consideration on heat flux decay length and the spatial resolution of the figure corresponds to the IR spatial resolution on these PFUs. One can note that the maximum cumulated energy is located between r=2.11 m and 2.15 m (corresponding to MB15-18) and r=2.21 m and 2.28 m (MB [25][26] for ISP and OSP respectively. The figures 3 and 4 illustrate the large variation of the emissivity during C4, especially on the inner side.…”

Section: Evolution Of the Emissivity Distribution Along The Divertor ...mentioning

confidence: 99%

Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

Gaspar¹,

Corre²,

Rigollet³

et al. 2022

Nucl. Fusion

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This paper summarizes the emissivity measurements performed on the plasma facing units (PFU) of the WEST lower divertor during the first phase of WEST running with a mix of actively cooled ITER-like PFUs made of bulk tungsten and inertially cooled PFUs made of graphite with a coating of tungsten. In-situ assessment of the emissivity and laboratory measurements after removing the W-coated graphite and ITER-grade PFUs from the WEST device are shown. The measurements exhibit a complex pattern with strong emissivity variation as function of space and time mainly explained with the variation of magnetic equilibrium (strike point location) as well as the plasma performances during the experimental campaigns. The exposed ITER-grade PFU exhibits sharp spatial variation of the emissivity from 0.05 to 0.85 at a monoblock scale (12mm) at the transition of the erosion (strike point location) and deposition (next to the strike point location) areas on the high field side. In the low field side, the emissivity varies from 0.12, at the strike point location, to 0.2 few cm away in the low field side direction. This emissivity range after exposure is much higher than the emissivity variation of unexposed PFU with emissivity from 0.09 to 0.15. In-situ observation performed on the W-coated graphite PFU shows a rapid evolution, typically few pulses, of the emissivity in the inner and outer strike point location. The whole spatial distribution is discussed as well as his variation due to the plasma operation from the start-up of WEST to the removal of the tungsten (W) coated graphite components.

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Infrared thermography in metallic environments of WEST and ASDEX Upgrade

Cited by 21 publications

References 13 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

Interpretation of temperature distribution observed on W-ITER-like PFUs in WEST monitored with a very-high-resolution IR system

Overview of the emissivity measurements performed in WEST: in situ and post-mortem observations

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