ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas

Lasa, A.; Borodin, D.; Canik, J.; Groth, M.; Kirschner, A.; Airila, Markus; Borodkina, I.; Ding, Rui

doi:10.1088/1741-4326/aa90c0

Cited by 12 publications

(9 citation statements)

References 44 publications

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“…Similar observations were made concerning stronger impurities production near the antennas and outer divertor [10]. Erosion-redeposition modelling of edge beryllium line spectroscopy of localized, ICRF sheath-enhanced emission at magnetically connected JET outer limiters was also shown to be consistent with increased local erosion [11,12]. An excellent overview of ICRF-induced plasma surface interaction was provided in [13], while a discussion about tungsten management for H-mode scenario's optimization in JET can be found in [14].…”

Section: Introductionmentioning

confidence: 54%

RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges

et al. 2021

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Plasma heating in the full Tungsten (W) Environment in Steady-state Tokamak (WEST) relies on electromagnetic waves in both Lower Hybrid (LH) and Ion Cyclotron Range of Frequencies (ICRF). The present study focuses mostly on the optimization of discharges heated with ICRF, by reporting different methods to first optimize wave coupling, optimize their absorption and reduce the impurity production. It is shown that ICRF coupling can be optimized either by moving the plasma closer to antennas, increasing the plasma density, wave frequency and LH power. We show that the absorption efficiency correlates with the hydrogen concentration with the existence of an optimum between 7 and 10% as expected for a minority heating scenario.Absolutely calibrated visible spectroscopy sightlines were used to monitor ion fluxes in different locations as part of an effort to quantitively estimate the contribution of different impurity sources to the core contamination by tungsten. It is typically found that in discharges with high total RF-power (above 5MW of LH and 3MW of ICRF), divertor and antenna limiter sources can reach similar order of magnitude during the ICRF phase.

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Section: Introductionmentioning

confidence: 54%

RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges

et al. 2021

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“…Such effects are understood as arising from local rectification of these fluctuating near-fields by the plasma near the local limiters, with the resulting potential acting then on the observed (remote) limiter via magnetic connection. Erosion modeling showed that the enhanced optical emission was consistent with increased local erosion of the Be limiter surface [3,4].…”

Section: Introductionmentioning

confidence: 83%

“…As such, this sightline (coming tangentially fro the left side) would glance by the antenna side of the limiter. This made the interpretation of the measurement challenging in the limiter surface erosion effort of Refs [3,4]. The shift of this spot back onto the limiter will also be of great value to the erosion modeling of this newer set of data.…”

Section: Experimental Arrangement and Approachmentioning

confidence: 99%

RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall

et al. 2017

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Abstract.A dedicated study on JET-ILW, deploying two types of ICRH antennas and spectroscopic observation spots at two outboard, beryllium limiters, has provided insight on long-range (up to 6m) RFenhanced plasma-surface interactions (RF-PSI) due to near-antenna electric fields. To aid in the interpretation of optical emission measurements of these effects, the antenna near-fields are computed using the TOPICA code, specifically run for the ITER-like antenna (ILA); similar modelling already existed for the standard JET antennas (A2). In the experiment, both antennas were operated in current drive mode, as RF-PSI tends to be higher in this phasing and at similar power (~0.5 MW). When sweeping the edge magnetic field pitch angle, peaked RF-PSI effects, in the form of 2-4 fold increase in the local Be source,are consistently measured with the observation spots magnetically connect to regions of TOPICAL-calculated high near-fields, particularly at the near-antenna limiters. It is also found that similar RF-PSI effects are produced by the two types of antenna on similarly distant limiters. Although this mapping of calculated near-fields to enhanced RF-PSI gives only qualitative interpretion of the data, the present dataset is expected to provide a sound experimental basis for emerging RF sheath simulation model validation.

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“…Concerning MD data for the interactions between pure Be and D, different works have already been carried out [15][16][17] and successfully used in ERO [15,18]. However, pure Be is easy to oxidize and a beryllium oxide (BeO) layer is expected to form on top of plasma-facing components.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics simulation of beryllium oxide irradiated by deuterium ions: sputtering and reflection

Hodille¹,

Byggmästar²,

Safi³

et al. 2019

J. Phys.: Condens. Matter

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The sputtering and reflection properties of wurtzite beryllium oxide (BeO) subjected to deuterium (D) ions bombardment at 300 K with ion energy between 10 eV and 200 eV is studied by classical molecular dynamics. Cumulative irradiations of wurtzite BeO show a D concentration threshold above which an 'unphysical dramatic' sputtering is observed. From the cumulative irradiations, simulation cells with different D concentrations are used to run non-cumulative irradiations at different concentrations. Using a D concentration close to the experimentally determined saturation concentration (0.12 atomic fraction), the simulations are able to reproduce accurately the experimental sputtering yield of BeO materials. The processes driving the sputtering of beryllium (Be) and oxygen (O) atoms as molecules are subsequently determined. At low irradiation energy, between 10 eV and 80 eV, swift chemical sputtering is dominant and produces mostly ODz molecules. At high energy, the sputtered molecules are mostly BexOy molecules (mainly BeO dimer). Four different processes are associated to the formation of such molecules: the physical sputtering of BeO dimer, the delayed swift chemical sputtering not involving D ions and the detachmentinduced sputtering. The physical sputtering of BeO dimer can be delayed if the sputtering event implies two interactions with the incoming ion (first interaction in its way in the material, the other in its way out if it is backscattered). The detachment-induced sputtering is a characteristic feature of the 'dramatic' sputtering and is mainly observed when the concentration of D is close to the threshold leading to this sputtering regime.

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ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas

Cited by 12 publications

References 44 publications

RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges

RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges

RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall

Molecular dynamics simulation of beryllium oxide irradiated by deuterium ions: sputtering and reflection

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