First analysis of the misaligned leading edges of ITER-like plasma facing units using a very high resolution infrared camera in WEST

Grosjean, A.; Corre, Y.; Dejarnac, R.; Gaspar, J.; Gunn, J.; Carpentier-Chouchana, S.; Courtois, X.; Delmas, E.; Temmerman, G. De; Diez, M.; Dubus, L.; Durocher, A.; Escourbiac, F.; Firdaouss, M.; Gerardin, J.; Houry, M.; Pitts, R.A.; Pocheau, C.; Tsitrone, E.

doi:10.1088/1741-4326/ab9fa6

Cited by 21 publications

(17 citation statements)

References 31 publications

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“…The main results are reported in [50,51]. It has to be noted that the thermal response of misaligned leading edges of ITER-grade PFUs, analysed with 3D finite elements modelling and IR imaging, is in agreement with the optical approximation of the parallel heat flux [52]. The damages were more severe for PFUs installed with a significant relative misalignment, for which poloidal leading edges were irradiated at near perpendicular incidence by the heat flux (measured misalignment up to 0.8 mm, to be compared with ITER specifications of 0.3 mm).…”

Section: First Evidence Of Damagesmentioning

confidence: 69%

Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation

Bucalossi

2022

Nucl. Fusion

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WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m−2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described.

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Section: First Evidence Of Damagesmentioning

confidence: 69%

Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation

Bucalossi

2022

Nucl. Fusion

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“…The deposits were retrieved on 2 PFUs, namely WJKA004 (located at position PFU10) and WERI002 (located at position PFU12), at the end of the C3 campaign (WERI002 was exposed during C3 only while WJKA004 was exposed during C1, C2 and C3). It should be noted that WERI002 was significantly misaligned during the C3 campaign (up to 0.8 mm in the OSP area), while WJKA004 was aligned within specifications (see [9] for a description of PFU misalignement during C3). In addition, deposits were collected at the end of the C4 campaign on PFU WEAN003, located at PFU17.…”

Section: Collection Proceduresmentioning

confidence: 99%

First post-mortem analysis of deposits collected on ITER-like components in WEST after the C3 and C4 campaigns

et al. 2021

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In order to map the complex plasma footprint observed on the lower divertor of the WEST experiment after its first phase of operation, we analysed deposits collected on ITER-like Plasma Facing Units (PFUs) exposed in the C3 (deuterium plasma) and C4 (deuterium and helium plasma) campaigns. Our results show that these deposits have multilayer structures mainly composed of tungsten, oxygen, boron and carbon, whose texture and composition vary along the radial direction. These traits allowed us to identify three types of deposits: deposits rich in boron (conditioning) in the low plasma flux area further away from the strike point, deposits rich in tungsten with traces of metallic compounds (Cu, Fe, Cr, Ni, Ag) in the high plasma flux area and deposits rich in boron and tungsten in the private flux area. In addition, we found more nanoparticles, voids and tungsten oxide layers in the deposits formed during C4 in comparison to that of C3.

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“…Emissivity and cumulated conducted energy before and after the pulse sequence (last pulse) are plotted in black and red respectively. The conducted energies for these pulses are: (a) 230 MJ for 12 similar pulses at R=2.27 m, (b) 720 MJ for 24 pulses at R=2.25 m, (c) 112 MJ for 8 pulses at R=2.29 m and (d) 2197 MJ for 106 pulses at R=2.235 m. These different periods correspond to experiment performed in the EU framework during C4 (a) PFU shaping experiment [28], (b) predamaged PFU experiment [29], (c) sustained melting experiment [30] and (d) the helium campaign [31]. The experiments (a), (b) and (c) have been performed with deuterium fueling and about 4 MW of LHCD heating, average core density was about 3.5 10 19 m -3 and Ip = 500 kA.…”

Section: Pulse To Pulse Emissivity Variation Near the Outer Strike Po...mentioning

confidence: 98%

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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First analysis of the misaligned leading edges of ITER-like plasma facing units using a very high resolution infrared camera in WEST

Cited by 21 publications

References 31 publications

Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation

Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation

First post-mortem analysis of deposits collected on ITER-like components in WEST after the C3 and C4 campaigns

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

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