Modeling and measurement of energetic particle slowing down in Wendelstein 7-X

Lazerson, S.; Pfefferlé, David; Drevlak, M.; Smith, H. M.; Geiger, J.; Äkäslompolo, S.; Xanthopoulos, P.; Dinklage, A.; Ford, O.; McNeely, P.; Rust, N.; Bozhenkov, S.; Hartmann, D.; Andreeva, T.; Schilling, J.; Brandt, C.; Neuner, U.; Thomsen, H.; Wolf, R. C.

doi:10.1088/1741-4326/ac0771

Cited by 21 publications

(26 citation statements)

References 26 publications

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“…A fast rise in stored energy on the order of 30 ms is present when the NBI is switched on. This is consistent with modeling of slowing down times for fast ions in W7-X [12]. A slower more asymptotic rise in the stored energy can be associated with the rise in density.…”

Section: Injection Into Ecrh Plasmassupporting

confidence: 88%

First neutral beam experiments on Wendelstein 7-X

Team¹,

Lazerson²,

Ford³

et al. 2021

Nucl. Fusion

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In the previous divertor campaign, the Wendelstein 7-X (W7-X) device injected 3.6 MW of neutral beam heating power allowing for the achievement of densities approaching 2 × 10 20 m −3 , and providing the first initial assessment of fast ion confinement in a drift optimized stellarator. The neutral beam injection (NBI) system on W7-X is comprised of two beam boxes with space for four radio frequency sources each. The 3.6 MW of heating reported in this work was achieved with two sources in the NI21 beam box. The effect of combined electron-cyclotron resonance heating (ECRH) and NBI was explored through a series of discharges varying both NBI and ECRH power. Discharges without ECRH saw a linear increase in the line-integrated plasma density, and strong peaking of the core density, over the

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Section: Injection Into Ecrh Plasmassupporting

confidence: 88%

First neutral beam experiments on Wendelstein 7-X

Team¹,

Lazerson²,

Ford³

et al. 2021

Nucl. Fusion

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“…In figure 7, they do not stand out as having improved confinement, but it should be cautioned that their triple products are likely underestimated, since port losses, shine-through, and fast ion losses were not taken into account when calculating their confinement times. Neutral beam power deposition simulations are still undergoing validation [41,42]. NBI results are discussed also in section 5.…”

Section: High-performance Discharges and Proof Of Neoclassical Optimi...mentioning

confidence: 99%

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Pedersen

2022

Nucl. Fusion

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We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ITG turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases.

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“…is the component of the velocity parallel to the magnetic field [18]. The effects of collisions and pitch angle scattering are included between integration time steps [29].…”

Section: Energetic Particle Simulationsmentioning

confidence: 99%

“…BEAMS3D's deposition model has been validated [30] and a preliminary validation and benchmarking of the slowing down model has been done [29]. The simulations for this work were done using a new feature created for BEAMS3D that models fusion births and uses the birth rates to initialize particles for simulation [19].…”

Section: Energetic Particle Simulationsmentioning

confidence: 99%

Energetic particle optimization of quasi-axisymmetric stellarator equilibria

et al. 2022

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An important goal of stellarator optimization is to achieve good confinement of energetic particles such as, in the case of a reactor, alphas created by Deuterium-Tritium (D-T) fusion. In this work, a fixed-boundary stellarator equilibrium was re-optimized for energetic particle confinement via a two-step process: first, by minimizing deviations from quasiaxisymmetry (QA) on a single flux surface near the mid-radius, and secondly by maintaining this improved quasi-axisymmetry while minimizing the analytical quantity ΓC , which represents the angle between magnetic flux surfaces and contours of J ||, the second adiabatic invariant. This was performed multiple times, resulting in a group of equilibria with significantly reduced energetic particle losses, as evaluated by Monte Carlo simulations of alpha particles in scaled-up versions of the equilibria. This is the first time that energetic particle losses in a QA stellarator have successfully been reduced by optimizing ΓC. The relationship between energetic particle losses and metrics such as QA error (E qa) and ΓC in this set of equilibria were examined via statistical methods and a nearly linear relationship between volume-averaged ΓC and prompt particle losses was found.

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Modeling and measurement of energetic particle slowing down in Wendelstein 7-X

Cited by 21 publications

References 26 publications

First neutral beam experiments on Wendelstein 7-X

First neutral beam experiments on Wendelstein 7-X

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Energetic particle optimization of quasi-axisymmetric stellarator equilibria

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