ITER relevant multi-emissive sheaths at normal magnetic field inclination

Tolias, Panagiotis; Komm, M.; Ratynskaia, S.; Podolník, A.

doi:10.1088/1741-4326/acaabd

Cited by 8 publications

(4 citation statements)

References 67 publications

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“…Melting of the monoblocs edges and thermionic emission was evidenced in several reports 5,6 . These experimental observations have lead to further numerical works emphasizing the importance of sheaths at the vicinity hot tungsten surfaces in ELMs phases for modeling the melt motion induced by fast transients 7 .…”

Section: Introductionmentioning

confidence: 91%

“…Other effects can strengthen J s though, such that the Schottky correction to the material work-function 31 , or secondary electron emission (see eg. 7 and references therein). If included in our numerical model, these effects would lead to an increase of the emitted current with respect to the one calculated with the Richardson formula and have an impact on the temperature at which the sheath limited regime appears.…”

Section: Introductionmentioning

confidence: 99%

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Thermionic emission of a tungsten surface in high heat flux plasma: PIC simulations

Moritz,

Heuraux,

Lemoine

et al. 2023

Physics of Plasmas

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The surface temperature of a tungsten surface facing hot hydrogen plasma is evaluated, thanks to 1d/3v particle-in-cell simulations in floating wall conditions. At each iteration, the plasma heat flux to the cathode is equalized with the outgoing one, which is due to thermionic emission, surface radiation, and heat conduction through the wall. The thermal conductivity is chosen within the range 35–160 W m−1 K−1 in the different simulations in order to take into account the surface condition. A transition from a cold temperature surface to a hot one arises for a critical thermal conductivity, whose value depends on the plasma parameters. This transition is very abrupt and leads to a space charge limited regime where the thermionic current penetrating the plasma has reached its maximal value and is about three times the Bohm current. Changing the initial conditions in the code, more particularly, the timing of electron emission, can lead to a very different final surface temperature. This history effect and the associated hysteresis are evidenced by means of fluid calculations, which are in a good agreement with the simulation results as well as with previous experimental measurements.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Thermionic emission of a tungsten surface in high heat flux plasma: PIC simulations

Moritz,

Heuraux,

Lemoine

et al. 2023

Physics of Plasmas

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“…Regarding SEE, the same model implemented in the SPICE2 code by Tolias et al [15,16] is here considered. This distinguishes between back-scattered electrons, which feature a probability η bse , and true secondary electrons, produced with a yield δ tse .…”

Section: Electron Wall Emission Modelmentioning

confidence: 99%

“…These differences are due to the self-consistent electric field considered by the PIC and are expected to grow if collisional effects are also included. Recent PIC studies [13][14][15][16] have also dedicated particular attention to the effect of the electron wall emission on the ion flux to the divertor wall. Thermionic and electron-induced SEE processes contribute to the reduction of the sheath potential drop, and in extreme cases, to the formation of a potential well or virtual cathode and inverse sheath [13,17], when either the wall temperature is very large or when the average SEE yield becomes larger than 1.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional collisional particle model of the divertor sheath with electron emissive walls

Cichocki,

Sciortino,

Giordano

et al. 2023

Nucl. Fusion

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A novel two-dimensional particle-in-cell code, named DESPICCO and developed at CNR-ISTP, is capable of simulating the thin plasma layer of several millimeters, adjacent to the divertor tiles of a Tokamak fusion reactor. Here, kinetic effects and non-neutral plasma physics in the Debye sheath can be self-consistently captured by the Particle-in-Cell approach. The code is firstly benchmarked against literature one-dimensional codes and additional theoretical predictions for a magnetized sheath. Then, it is applied to a realistic divertor scenario featuring an attached plasma with monoblocks radial misalignment and gaps, to compute the energy flux amplification factor at the exposed monoblock edge. A non-ambipolar local current density close to the leading edge and an average sheath heat transmission coefficient larger than the one predicted by classical sheath theory, are found. The effects of electron wall emission and plasma-gas collisions on the ion Mach number and on particle and energy fluxes to the walls are finally estimated to determine future guidelines for simulations. Ion collisions with recycled neutrals and both secondary and thermionic electron emission from the wall are found to have a relevant impact, with the overall effect of reducing by 25% the average ion impact energy, and by 15-20% the total heavy particles energy flux to the walls, with relevant implications on the divertor wall erosion.

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