Energy Deposition from ELMs in Fusion Devices

Loarte, A.

doi:10.1007/3-540-27362-x_3

Cited by 9 publications

(14 citation statements)

References 38 publications

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“…Already after the experiment a layer by layer growth of the damage was postulated utilising high resolution imagery, this can now be confirmed by fig 11. the melt material is transport from the central part of the lamella to the high-field side following the jxB force direction.…”

Section: Post -Mortem Analysis -Ilw-1 Leading Edge Lamellamentioning

confidence: 64%

“…The high stored energies of which ITER will be capable means that even with all PFC edges protected, shallow surface melting can still occur under uncontrolled plasma disruptions and ELM transients. ‡ The impact and physics of ‡ ELMs are transient relaxation of the edge gradients in the fusion plasma, causing expulsion of particles and heat [11] to the first Wall of a fusion device. The Particle and heat-fluxes typically follow the magnetic field and thus impact the divertor where the fields lines impinge the tungsten components.…”

Section: Introductionmentioning

confidence: 99%

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Transient induced tungsten melting at the Joint European Torus (JET)

et al. 2017

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Melting is one of the major risks associated with Tungsten Plasma-Facing Components (PFCs) in tokamaks like JET or ITER. These Components are designed such that leading edges and hence excessive plasma heat loads deposited at near normal incidence are avoided. Due to the high stored energies in ITER discharges, shallow surface melting can occur under insufficiently mitigated plasma disruption and so called Edge Localised Modes -Power load transients.A dedicated program was carried out at the Joint European Torus (JET) to study the physics and consequences of W transient melting. Following initial exposures in 2013 (ILW-1) of a Tungsten-lamella with leading edge, new experiments have been performed on a sloped surface (15 • slope) during the 2015/2016 (ILW-3) campaign. This new experiment allows significantly improved Infrared thermography measurements and thus resolved important issue of power loading in the context of the previous leading edge exposures. The new lamella was monitored by local diagnostics: spectroscopy, thermography and high resolution photography in between discharges. No impact on the main plasma was observed despite a strong increase of the local W source consistent with evaporation. In contrast to the earlier exposure, no droplet emission was observed from the sloped surface. Topological modifications

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Section: Post -Mortem Analysis -Ilw-1 Leading Edge Lamellamentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Transient induced tungsten melting at the Joint European Torus (JET)

et al. 2017

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“…Tokamak experiments have been pursuing the identification of power flows during disruptions to provide guidance for ITER [21][22][23][24][25][26][27][28][29] .…”

Section: Off-normal Heat Loadingmentioning

confidence: 99%

“…VDEs have a release of about half the stored energy at wall contact over energy confinement time scales of 1-2 s, and then the rest is lost in the TQ, while in the MD it can be assumed that up to 100% of the plasma stored energy is lost in the TQ, particularly for our aggressive plasma configurations 21 . The timescale for the TQ has been correlated with plasma volume, giving a range of Δt TQ = 1.5-2.75 ms 26 . Just like ELMs, the heat load has an asymmetric triangle waveform, rising in about Δt TQ , and falling in ~2-4 of these time scales.…”

Section: Off-normal Heat Loadingmentioning

confidence: 99%

“…The area of the outboard first wall to receive the energy is 396 m 2 , and with a peaking factor of 2x, we reduce this to 198 m 2 . Since the heat fluxes are so large, reaching levels where melting is anticipated, the timescale to be used in the expression for the temperature rise should be the full duration of the "above melting threshold", and so for these calculations we use 4xΔt TQ for the duration and remove the 2/3 factor associated with the rise phase 26 . Using the same semi-infinite expression for the temperature rise, we find values in the divertor (assuming 10x expansion of deposition area, Δt TQ = 2 ms, and 65% to each divertor) of 2250-11260 o K for tungsten, well beyond melting at the high end, while just reaching melting at the low end.…”

Section: Off-normal Heat Loadingmentioning

confidence: 99%

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The Evaluation of the Heat Loading from Steady, Transient and Off-Normal Conditions in ARIES Power Plants

Kessel

Tillack

Blanchard

2013

Fusion Science and Technology

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Overview of JET results

2005

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High density and high confinement operation in ELMy H-mode is confirmed at or above the normalized parameters foreseen for the ITER operating point (H 98(y,2) ∼ 1, n/n GW ∼ 1, β N > 1.8 at q 95 ∼ 3). The scaling of the ELMy H-mode with β N could be more favourable than that predicted by the IPB98(y,2) scaling. In ELMy H-mode, ion cyclotron current drive (ICCD) control of large sawteeth stabilized by fast particle has been demonstrated and the underlying neo-classical tearing modes (NTMs) and sawtooth physics is being refined. At high-density, Type I ELMy H-modes show trends that would lead to marginally acceptable ELMs on ITER. Type II ELM regime has been produced, though under very restrictive conditions. Type III ELMy operation with radiation fractions up to 95% has been demonstrated by seeding of N 2 in H-modes and could extrapolate to Q = 10 ITER operation, albeit at high current (17 MA). The mitigation of Type I ELMs, nevertheless, remains a challenge. Considerable progress has been obtained in internal transport barrier (ITB) plasmas, with operation at central densities close to the Greenwald density or/and low toroidal rotation or/and high triangularity. Demonstrations of full current drive and successful simultaneous real time control of safety factor and temperature profiles have been achieved in ITB plasmas. Physics of resistive wall modes (RWMs) has been compared with theory, showing favourable scaling for ITER. High β N ∼ 2.8 operation of hybrid modes (also called improved H-modes) has been obtained with dominant neutral beam heating. Hybrid modes with dominant ion cyclotron resonance heating (ICRH) have also been achieved.Trace tritium experiments yielded valuable information on particle transport in H-mode, ITB and hybrid regimes. In Type I ELMy plasmas, successful tests of the conjugate-T ICRH scheme have been achieved as well as lower hybrid coupling at ITER-relevant 10-11 cm distances. Reduced D and T fuel retention has been observed, which could relate to operation with vertical targets in the divertor and/or lower (ITER-like) vessel temperature. It is confirmed that erosion occurs predominantly on the main chamber surfaces, with possible benefits for T retention in ITER, although consequences for the metallic first wall lifetime need to be assessed. Disruption and ELM studies indicate that transient power deposition could be less constraining than expected for the ITER divertor, but more challenging for the metallic first wall. Alpha particle tomography and direct observation of alpha particle slowing down have been made possible by γ -spectroscopy. Measurements of Alfvén cascades have been improved by a new interferometric technique. Promising tests of ITER relevant neutron counting detectors have been conducted.

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Energy Deposition from ELMs in Fusion Devices

Cited by 9 publications

References 38 publications

Transient induced tungsten melting at the Joint European Torus (JET)

Transient induced tungsten melting at the Joint European Torus (JET)

The Evaluation of the Heat Loading from Steady, Transient and Off-Normal Conditions in ARIES Power Plants

Overview of JET results

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