Damaging of inclined/misaligned castellated tungsten surfces exposed to a large number of repetitive QSPA plasma loads

Makhlai, V.А.; Herashchenko, S.S.; Aksenov, N.N.; Byrka, O.V.; Garkusha, I.E.; Wirtz, M.; Spilker, B.

doi:10.1088/1402-4896/ab4e52

Cited by 13 publications

(26 citation statements)

References 24 publications

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“…Additionally, they possess some other plasma features that are not reproducible, e.g. with ebeams or lasers [15][16][17][18][19][20][21]. QSPA plasma streams provide large power (several GW m −2 ) and energy (up to 30 MJ m −2 ) fluxes that mimic conditions of transient events in fusion reactor.…”

Section: Introductionmentioning

confidence: 99%

Vapour shielding of liquid-metal CPS-based targets under ELM-like and disruption transient loading

et al. 2021

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This paper presents experimental studies of plasma-surface interactions during powerful plasma impacts of a quasi-stationary plasma accelerator (QSPA) on the Sn capillary porous systems (CPSs) in conditions simulating disruption and edge localized modes (ELM) like loads. Experiments were carried out using two QSPA devices. ELM-like plasma exposures were performed with QSPA-M test-bed facility. A large-scale QSPA Kh-50 device was used to simulate plasma disruptions and giant ELMs. Variation of the plasma stream energy density has been performed to study the onset of vapour shield. It is shown that during plasma exposures of a Sn-CPS target with the QSPA plasma load <1 MJ m −2 , single dust particles traces have been registered. A further increase in the heat load leads to the splashing of the eroded material. For ELM-like impacts, a rather weak melt motion was observed on the target surface. A post-mortem analysis has shown that the CPS structure was not destroyed in the course of many repetitive ELM-like pulses. Surface morphology has changed from a smooth surface to corrugation structures with the formation of some cavities in mesh cells due to the influence of the surface tension and capillary effects. Spectral lines of Sn I and Sn II have been identified by optical emission spectroscopy in the near-surface plasma. A plasma shield, that consists mostly of Sn neutrals appears at Q ∼ 0.1 MJ m −2 . An increase in the surface heat load resulted in the intensive emission of Sn II lines, which started to be observed at Q ∼ 0.3 MJ m −2 . The plasma electron density near the surface increases significantly at Q > 0.5 MJ m −2 , which corresponds to the strong vapour shielding of the exposed surface. A comparison between the obtained results on the vapour shielding of Sn CPS and available numerical simulation using the TOKES code has been performed.

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Section: Introductionmentioning

confidence: 99%

Vapour shielding of liquid-metal CPS-based targets under ELM-like and disruption transient loading

et al. 2021

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“…Additional insight into the hydrodynamic regimes described in section 3.1 can be gained by exploiting a crude analogy between the flows of interest and the development of Rayleigh-Taylor instabilities at the surface of a planar fluid film. This analogy consists in considering the liquid layer as if it were lying over a flat surface and subjected to a normal body force F ∼ ρ m v 2 /h, whose magnitude emulates the centrifugal force that appears in a reference frame following the rotation of the actual fluid across the corner [22][23][24]. Under this assumption, the dispersion relation of linearly unstable Rayleigh-Taylor modes for an inviscid film of thickness h [25],…”

Section: Classification By Weber Numbersmentioning

confidence: 99%

Simulations of liquid metal flows over plasma-facing component edges and application to beryllium melt events in JET

et al. 2022

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Navier-Stokes simulations of liquid beryllium flows over the straight edge of plasma-facing components are carried out in conditions emulating upper dump plate melting observed experimentally in JET. The results demonstrate the existence of three main hydrodynamic regimes featuring various degrees of downstream flow attachment to the underlying solid surface. Transitions between these regimes are characterized by critical values of the Weber number, which quantifies the relative strength of fluid inertia and surface tension, thereby providing a general stability criterion that can be applied to any instance of transient melt events in fusion devices. The predictive capabilities of the model are tested by comparing numerical output with JET data regarding the morphology of the frozen melt layers and the location of beryllium droplets splashed onto nearby vacuum vessel surfaces as a result of disruption current quench plasmas interacting with the solid beryllium tiles protecting the upper main chamber regions. Simulations accounting for the coupling between fluid flow and heat transfer confirm the key role played by re-solidification as a stabilizing process, as previously found through macroscopic melt dynamics calculations performed with the MEMOS-U code. The favourable agreement found between the simulations and the general characteristics of the JET beryllium upper dump plate melt splashing give confidence that the same approach can be applied to estimate the possibility of such mechanisms occurring during disruptions on ITER.

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“…For example, pools formed in the TEXTOR melting experiment, that featured a thermally insulated 2 mm thick W plate exposed to plasma over several Our discussion has been so far limited to evidence from contemporary fusion devices. A large number of experiments were also carried out in Quasi-Steady-State Plasma Accelerators (QSPAs), multiple mirror magnetic confinement and linear machines aiming to elucidate metal PCF behaviour under high transient heat flux loads (Tereshin et al 2003;Klimov et al , 2011Klimov et al , 2017Shoshin et al 2011;Kupriyanov et al 2015;Arzhannikov et al 2013;Morgan et al 2014;De Temmerman et al 2013;Makhlaj et al 2013;Garkusha et al 2007Garkusha et al , 2009Garkusha et al , 2014Garkusha et al , 2015Makhlai et al 2019Makhlai et al , 2020. Such experiments yield valuable data for the validation and benchmarking of models as they are often accompanied by direct observation of splashing events, providing information on the initial velocities and sizes of ejected droplets.…”

Section: Release Of Freshly Generated Dust and Dropletsmentioning

confidence: 99%

“…Caution must be exercised when extrapolating these results to other scenarios, since the heat loads might be comparable to those expected in future reactors, but the plasma conditions and specifics of plasma production are often not relevant to tokamaks. The current closure through the end plate in linear machines (providing a J × B volume force rotating the melt) De Temmerman et al ( 2013), the highin excess of MPa-plasma pressures in QSPAs (driving the molten layer unstable) Makhlai et al (2020) and the magnetic field inclination angle are a few characteristic examples.…”

Section: Release Of Freshly Generated Dust and Dropletsmentioning

confidence: 99%

Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

Ratynskaia

Bortolon

Krasheninnikov

2022

Rev. Mod. Plasma Phys.

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In this paper, we present a brief historic overview of the research on dust in fusion devices with carbon plasma-facing components and then highlight the most recent developments in the post-carbon era of the field. In particular, we consider how the metallic dust form, mobilize, and interact with fusion plasmas and plasma facing components. Achievements in wall conditioning and associated anomalous plasma transport modification, including ELM suppression, with the powder injection technique is another focus of the paper. Capabilities of the state-of-art simulation tools to describe different aspects of dust in fusion devices are exemplified and new directions for future dust studies are brought forward.

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Damaging of inclined/misaligned castellated tungsten surfces exposed to a large number of repetitive QSPA plasma loads

Cited by 13 publications

References 24 publications

Vapour shielding of liquid-metal CPS-based targets under ELM-like and disruption transient loading

Vapour shielding of liquid-metal CPS-based targets under ELM-like and disruption transient loading

Simulations of liquid metal flows over plasma-facing component edges and application to beryllium melt events in JET

Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

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