Effect of misaligned edges and magnetic field orientation on plasma deposition into gaps during ELMs on ITER

Dejarnac, R.; Komm, M.; Gunn, J.; Pekarek, Z.

doi:10.1016/j.jnucmat.2010.09.042

Cited by 18 publications

(26 citation statements)

References 6 publications

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“…Larmor-orbit motion effects were recently considered in detail for the case of misalignments in ITER [11,12]. For cases, where the Larmor orbit radii (ρ L ) are comparable or larger in size than half the misalignment (0.5d) in question the projected heat loads vary significantly from the OA, instead spreading part of the heat load over a larger area on the top-surface of the misaligned block (so-called Larmor smoothing).…”

Section: Introductionmentioning

confidence: 99%

Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI linear devices

Morgan¹,

Berg²,

Temmerman³

et al. 2017

Nucl. Fusion

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For the final design of the ITER divertor it is important to determine whether shaping of each tungsten monoblock to eliminate leading edges is required or not. In order to aid this decision, two experiments were performed in DIFFER's linear plasma devices to study heat loads on misaligned water cooled blocks at glancing incidence. First, a series of tungsten blocks were exposed to a high parallel heat flux (26 MW m −2 ) hydrogen plasma beam in the Magnum-PSI linear device. The blocks were exposed at an oblique angle between 4 • and 7 • with respect to the plasma beam, approaching the low angle of incidence expected in the ITER divertor strike-point regions. One block was vertically misaligned with respect to the others by a value between 0 and 1.2 mm, and the surface temperature evolution monitored. This was compared to a finite element thermo-mechanical model of the system, to investigate any discrepancies between the two. The importance of Larmor orbit smoothing effects could also be considered, as the Larmor radius was larger than half the misalignment height. Next, a row of identical tungsten blocks were exposed at an angle of 3 • to ∼500-700 μs pulsed hydrogen plasmas of peak power between 275-625 MW m −2 in the Pilot-PSI linear device, to simulate the effect of edge localized mode (ELM) transients. One block was misaligned with respect to the others by 1 mm. In all cases, the model and experiment were found to be in excellent agreement (to ∼1%), demonstrating clearly that an optical approximation for plasma power loading on misaligned edges is appropriate. A simple model including Larmor smoothing was applied, the results of which give a similar prediction to the optical approximation for the temperature of the misaligned edges, within the error of the temperature measurements, though a small decrease in edge temperature is calculated. Therefore it can be concluded that the application of the optical approximation is generally appropriate as an input physics assumption for the study of shaping alternatives.

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Section: Introductionmentioning

confidence: 99%

Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI linear devices

Morgan¹,

Berg²,

Temmerman³

et al. 2017

Nucl. Fusion

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“…Particle-incell (PIC) simulations show that the power deposition profile around a LE generally differs from the OA when the height of the misalignment is smaller than two Larmor radii, i.e. h < 2rL [31]. Hence, the OA is expected to be valid for electrons, while for ions, the ion Larmor radii should impact the heat flux distribution on chamfered PFUs (h ≤ 0.6 mm).…”

Section: Summary Of the Results And Discussionmentioning

confidence: 99%

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

Grosjean¹,

Corre²,

Dejarnac³

et al. 2020

Nucl. Fusion

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Twelve ITER-like plasma-facing units made of tungsten were exposed in the WEST tokamak divertor, with three PFUs significantly overexposed to plasma heat flux: one sharp-edged PFU (vertical misalignment h = 0.8 mm) and two chamfered PFUs (h = 0.6 mm and 0.3 mm, respectively). This paper describes the first temperature analysis obtained with a very high spatial resolution infrared camera (pixel size ~ 0.1 mm) on the misaligned PFU edges and shows the consistency obtained on the parallel heat flux derived from these measurements. The analysis is focused on the hottest areas of the PFU misaligned leading edges, since the temperature detection threshold of the VHR camera is high (Tthreshold,BB ≈ 370°C). The heat flux parallel to the magnetic field lines is assessed by matching the toroidal temperature profile in the vicinity of the leading edge with 3D finite element modelling. The tungsten emissivity assumed in this study is 0.6, consistent with laboratory measurements for damaged PFUs. For the three PFUs studied (with different vertical misalignments, incident angles, geometries), the derived parallel heat flux is similar, and consistent with independent measurements by a Fiber Bragg grating embedded in a graphite PFU at another toroidal location, giving confidence in future experiments using the same settings.

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“…For such plasma conditions and B t = 3.8 T, the deuterium Larmor radius is r L = 0.9 mm. The misalignment being smaller than the ion gyro-radius (d/r L = 0.22), an important smoothing of the flux falling on the leading edge is expected [2]. The power deposition profile on the protruding tile is computed using a 2D PIC model, which describes charge particles trajectories in a self-consistent electric field [3].…”

Section: The Larmor Radius Smoothing Effectmentioning

confidence: 99%

“…The Larmor radius smoothing effect for TS geometry (d = 0.2 mm, gap size = 2 mm, a = 1°) and edge plasma condition is described in Section 3. In this section we compare the center-guide ballistic modelling, based on projection of the parallel heat flux on the PFC with 2D particle-in-cell (PIC) modelling [2,3] which takes into account the Larmor radius of incident particles. Numerical heat load distributions are coupled with 2D thermal modeling in order to simulate the temperature distribution on top and side of the tile.…”

Section: Introductionmentioning

confidence: 99%

Heat flux distribution and gyro-radius smoothing effect on misaligned CFC tile in the Tore Supra tokamak

Corre

Dejarnac

Gardarein

et al. 2015

Journal of Nuclear Materials

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Effect of misaligned edges and magnetic field orientation on plasma deposition into gaps during ELMs on ITER

Cited by 18 publications

References 6 publications

Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI linear devices

Power deposition on misaligned castellated tungsten blocks in the Magnum-PSI and Pilot-PSI linear devices

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

Heat flux distribution and gyro-radius smoothing effect on misaligned CFC tile in the Tore Supra tokamak

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