A Scenario of Pulsed Ecrh Wall Conditioning in Hydrogen for the Wendelstein 7-X Helias

Moiseenko, V.Е.; Beletskii, A. A.; Shapoval, A. M.; Wauters, T.; Goriaev, A.; Brunner, K. J.; Buttenschön, B.; Drewelow, P.; Winters, V.; Brakel, R.; Dinklage, A.; Brezinsek, S.; Stange, T.; Laqua, H. P.; Lazersson, S.; Team, West

doi:10.46813/2019-119-037

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…The trends of the final key parameter of the ECWC discharges are illustrated in figure 1(e). The D 2 density briefly spikes at the plasma breakdown phase due to an intense flux of low energy dissociation neutrals and the subsequent release of surface absorbants from the PFC's, as seen in [10]. Hereafter the gas density drops quickly to reach a steady value where valve and wall fuelling are balanced by vacuum and plasma pumping.…”

Section: Experiments and Analysis Setupmentioning

confidence: 98%

Characterisation of electron cyclotron wall conditioning plasma in ASDEX Upgrade

Wauters

Buermans²,

Cavalier

et al. 2023

Nucl. Fusion

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Electron Cyclotron Wall Condition (ECWC) discharges are characterised in ASDEX Upgrade with full tungsten plasma facing components and X2 polarised waves launched from the equatorial ports, relevant to ECWC conditions in ITER Pre-Fusion Power Operation phase 1. The characterisation of the deuterium plasmas is based on experimental inputs such as electron density measurements, in-vessel pressure measurements, poloidal field maps obtained from the measured coil currents, as well as advanced tomographic methods on camera images filtered at the hydrogen Balmer lines. TOMATOR-1D simulations and CTS radiometer spectra complement the findings. The cold, high density and partially ionized toroidal plasmas show significant levels of stray radiation. The measured radiation includes waves at half of the gyrotron frequency suggesting the occurance of parametric decay instabilities at 2nd harmonic upper hybrid resonance that locates at the LFS of the resonance. A displacement of the plasma emission along the resonance layer is observed at higher discharge power in discharges with a vertical poloidal magnetic field only. By optimizing the poloidal field pattern, along with the location of the ECH resonance, the strongest surface interaction regions for the charged particles can be controlled. Directing plasma flux to inner wall surfaces, and same for the inner divertor apron, is found less effective in ASDEX Upgrade due to magnetic mirror effects and outward convective flows. Modeling however predicts the presence of an intense and uniform flux of low energy atoms produced at the ECH absorption layer that may be effective for conditioning the high field side surfaces after use of the disruption mitigation system.

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Section: Experiments and Analysis Setupmentioning

confidence: 98%

Characterisation of electron cyclotron wall conditioning plasma in ASDEX Upgrade

Wauters

Buermans²,

Cavalier

et al. 2023

Nucl. Fusion

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“…An ECRH conditioning scenario without full ionization is tested at W7-X via fast repetition of ultra-short pulses (3 ms) aiming at a large uniform atomic hydrogen flux to the PFC [44].…”

Section: Conditioning By Ecrh Plasmamentioning

confidence: 99%

Wall conditioning in fusion devices with superconducting coils

Wauters¹,

Borodin

Brakel

et al. 2020

Plasma Phys. Control. Fusion

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Wall conditioning is essential in tokamak and stellarator research to achieve plasma performance and reproducibility. This paper presents an overview of recent conditioning results, both from experiments in present devices and modelling, in view of devices with superconducting coils, with focus on W7-X, JT-60SA and ITER. In these devices, the coils stay energised throughout an experimental day or week which demands for new conditioning techniques that work in presence of the nominal field, in addition to the proven conditioning methods such as baking, glow discharge conditioning (GDC) and low-Z wall coating through GDC-plasma, which do not work under such condition. The discussed techniques are RF conditioning without plasma current, both in the ion cyclotron and electron cyclotron range of frequencies, and diverted conditioning plasmas with nested magnetic flux surfaces.

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A Scenario of Pulsed Ecrh Wall Conditioning in Hydrogen for the Wendelstein 7-X Helias

Cited by 2 publications

References 5 publications

Characterisation of electron cyclotron wall conditioning plasma in ASDEX Upgrade

Characterisation of electron cyclotron wall conditioning plasma in ASDEX Upgrade

Wall conditioning in fusion devices with superconducting coils

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