Simulating the impact of charge exchange on beam ions in MAST-U

Ollus, Patrik; Akers, R.; Colling, Bethany; El-Haroun, Hana; Keeling, D.; Kurki-Suonio, T.; Sharma, R.; Snicker, A.; Varje, J.

doi:10.1088/1361-6587/ac4856

Cited by 5 publications

(15 citation statements)

References 25 publications

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“…In devices with higher temperatures and higher neutral beam injection energies, CX losses are lower due to the strong decrease of the CX cross section as energy increases, and therefore usually neglected. However, in the case of TJ-II NBI plasmas, in particular if they are interesting from the point of view of Alfvén Eigenmodes (AEs) studies (relatively low plasma density), the density of neutrals atoms in the plasma makes the CX losses relevant and they need to be included if a reliable estimate of the fast ion slowing down distribution is desired [15]. In low density conditions, former guiding center calculations done with FAFNER [16] showed that CX losses in TJ-II plasmas can reach up to 30% of the port through power, which represents almost 70% of the available power due to the high level of shine through [17].…”

Section: Introductionmentioning

confidence: 99%

Validating neutral-beam current drive simulations in the TJ-II stellarator

Mulas¹,

Cappa²,

Martínez-Fernández³

et al. 2023

Preprint

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In this paper, we analyze the results of neutral-beam current drive (NBCD) experiments, performed in the TJ-II stellarator, with the aim of validating the theoretical predictions. Both parallel and anti-parallel injection with respect to the magnetic field were explored using co (NBI1) and counter (NBI2) beams at different injected beam power and plasma densities. The fast-ion current driven by both beams was simulated with the Monte Carlo code ASCOT and the electron response to the fast-ion current was calculated analytically using a model valid for an arbitrary magnetic configuration and a low collisionality plasma. The model reproduces with rather good agreement the toroidal current measured in NBI2 plasmas while the current driven by NBI1 is less than half the predicted one. Possible reasons for this discrepancy are discussed.

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Section: Introductionmentioning

confidence: 99%

Validating neutral-beam current drive simulations in the TJ-II stellarator

Mulas¹,

Cappa²,

Martínez-Fernández³

et al. 2023

Preprint

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“…Effects of resonant magnetic perturbations and CX on the fast ion behaviour (McClements et al 2018) in MAST (mega ampere spherical tokamak) have been simulated by the guiding-centre and full orbit code OMFC (Tani et al 2016). The TRANSP (Goldston et al 1981) code with its guiding-centre orbit-following module NUBEAM (Pankin et al 2004a,b), has been used to compute CX losses of fast ions in MAST (Tournianski et al 2005) and MAST-U (Ollus et al 2022). The impact of CX on NBI ion losses has been simulated in MAST-U (Ollus et al 2022) by using the ASCOT (Hirvijoki et al 2014) code.…”

Section: Introductionmentioning

confidence: 99%

“…The TRANSP (Goldston et al 1981) code with its guiding-centre orbit-following module NUBEAM (Pankin et al 2004a,b), has been used to compute CX losses of fast ions in MAST (Tournianski et al 2005) and MAST-U (Ollus et al 2022). The impact of CX on NBI ion losses has been simulated in MAST-U (Ollus et al 2022) by using the ASCOT (Hirvijoki et al 2014) code. The NBI ion losses induced by CX has also been simulated in COMPASS (Jaulmes, Westerhof & de Blank 2014) by using the full orbit code EBdyna (Jaulmes et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Guiding-centre orbit-following simulations of charge exchange loss of NBI ions with the finite Larmor radius effect

Xu,

Wang,

et al. 2023

J. Plasma Phys.

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Guiding-centre orbit-following simulations of the charge exchange (CX) loss of neutral beam injection (NBI) ions are presented. The finite Larmor radius (FLR) effect in the fast ion–neutral collision can be included in guiding-centre orbit-following simulations by using the gyroaverage method. It is proved that the neutralization probability of fast ions computed by using the gyroaverage method in the guiding-centre orbit simulation is roughly the same as that computed in the full-orbit simulation when the time step in the guiding-centre simulation is the order of the gyroperiod. The CX losses of NBI fast ions for two NBIs in the EAST tokamak have been simulated by the guiding-centre orbit-following code GYCAVA, and the FLR effect in the fast ion–neutral collision on CX losses has been numerically studied. The CX effect of the fast ion–neutral collision can significantly enhance NBI ion losses on EAST. The FLR effect in the fast ion–neutral collision can enhance the CX loss. Vertical asymmetry of localized heat loads induced by CX losses is found, which is related to the FLR effect of fast ions and the strong radial gradient of the neutral density near the plasma edge. Heat loads induced by CX losses are localized in the regions near the poloidal angle $\theta =-60^\circ$ , because the likelihood of exchanging charge is the largest at gyrophase $\xi ={\rm \pi}$ , and this leads to fast downwards moving neutrals. Fast ion loss fractions induced by CX increase with the neutral density increasing.

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Validating the simulation of beam-ion charge exchange in MAST Upgrade

Ollus,

Allan,

Harrison

et al. 2023

Plasma Phys. Control. Fusion

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Simulation of the impact of charge-exchange (CX) reactions on beam ions in the Mega Amp Spherical Tokamak (MAST) Upgrade was compared to measurements carried out with a fission chamber (neutron fluxes) and a fast ion deuterium-alpha (FIDA) diagnostic. A simple model was developed to reconstruct the outer-midplane neutral density based on measurements of deuterium-alpha emission from edge neutrals, and on Thomson scattering measurements of electron density and temperature. The main computational tools used were the ASCOT orbit-following code and the FIDASIM code for producing synthetic FIDA signals. The neutral density reconstruction agrees qualitatively with SOLPS-ITER modelling and yields a synthetic passive FIDA signal that is consistent with measurement. When CX losses of beam ions are accounted for, predicted neutron emission rates are quantitatively more consistent with measurement. It was necessary to account for CX losses of beam ions in simulations to reproduce the measured passive FIDA signal quantitatively and qualitatively. The results suggest that the neutral density reconstruction is a good approximation, that CX with edge neutrals causes significant beam-ion losses in MAST Upgrade, typically 20% of beam power, and that the ASCOT fast-ion CX model can be used to accurately predict the redistribution and loss of beam ions due to CX.

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Simulating the impact of charge exchange on beam ions in MAST-U

Cited by 5 publications

References 25 publications

Validating neutral-beam current drive simulations in the TJ-II stellarator

Validating neutral-beam current drive simulations in the TJ-II stellarator

Guiding-centre orbit-following simulations of charge exchange loss of NBI ions with the finite Larmor radius effect

Validating the simulation of beam-ion charge exchange in MAST Upgrade

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