Verification and validation of the high-performance Lorentz-orbit code for use in stellarators and tokamaks (LOCUST)

Ward, Simon; Akers, R.; Jacobsen, A. S.; Ollus, Patrik; Pinches, S. D.; Tholerus, Emmi; Vann, R. G. L.; Zeeland, Michael Van

doi:10.1088/1741-4326/ac108c

Cited by 7 publications

(6 citation statements)

References 47 publications

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“…To ensure accuracy when extrapolating to ITER, we tested the implementation of 3D magnetic fields in LOCUST by applying it to an already operating device where the impact of RMPs on NBI fast-ion confinement has been assessed experimentally and by other modelling tools. The code has previously been shown [17] to compare well with other fast-ion codes and experiment in a variety of scenarios with axisymmetric plasmas, including those with ITER-similar shapes such as DIII-D shot #157418 [7]. Here we study DIII-D shot #157418 again, including the n 0 = 3 RMP applied during the discharge.…”

Section: D Magnetic Fields In Locustmentioning

confidence: 98%

“…This bottlenecks attempts to systematically simulate the ITER system without significant computational resources, making the optimisation problem difficult. However, the Lorentz-orbit code for use in stellarators and tokamaks (LOCUST) code [17] is a novel kinetic fast-ion algorithm that is designed to make reactor-scale systems tractable on desktop hardware. While this could potentially provide a way of discovering new physics, in this context LOCUST also enables the routine study of ITER at high fidelity, allowing for precise optimisation-for example through the minimisation of localised, component-specific power loads.…”

Section: Introductionmentioning

confidence: 99%

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LOCUST-GPU predictions of fast-ion transport and power loads due to ELM-control coils in ITER

Ward

Akers

et al. 2022

Nucl. Fusion

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The LOCUST-GPU code has been applied to study the fast-ion transport and loss caused by resonant magnetic perturbations in the high-performance Q= 10 ITER baseline scenario. The unique computational efficiency of the code is exploited to calculate the impact of the application of the ITER ELM-control-coil system on neutral beam heating efficiency, as well as producing detailed predictions of the resulting plasma-facing component power loads, for a variety of operational parameters—the toroidal mode number n0, mode spectrum and absolute toroidal phase of the imposed perturbation. The feasibility of continually rotating the perturbations is assessed and shown to be effective at reducing the time-averaged power loads.Through careful adjustment of the relative phase of the applied perturbation in the three rows of coils, peak power loads are found to correlate with reductions in NBI heating efficiency for n= 3 fields. Adjusting the phase this way can increase total NBI system efficiency by approximately 2-3% and reduce peak power loads by up to 0.43 MWm-2. From the point of view of fast-ion confinement, n= 3 ELM control fields are preferred overall to n= 4 fields.In addition, the implementation of 3D magnetic fields in LOCUST is also verified by comparison with the SPIRAL code for a DIII-D discharge with ITER-similar shaping and n= 3 perturbation.

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Section: D Magnetic Fields In Locustmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

LOCUST-GPU predictions of fast-ion transport and power loads due to ELM-control coils in ITER

Ward

Akers

et al. 2022

Nucl. Fusion

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“…The distribution function was calculated by cumulatively binning the fast ion markers on the CPU every 100 ns. This process results in the calculation of the steady-state distribution function through sum reduction by using the entire history of one set of markers from birth until thermalisation or loss from the plasma [22].…”

Section: Modelling the Beam Ion Distribution Functionmentioning

confidence: 99%

Toroidal Alfvén eigenmodes observed in low power JET deuterium–tritium plasmas

Oliver,

Sharapov,

Štancar

et al. 2023

Nucl. Fusion

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The Joint European Torus recently carried out an experimental campaign using a plasma consisting of both deuterium (D) and tritium (T). We observed a high-frequency mode using a reflectometer and an interferometer in a D-T plasma heated with low power neutral beam injection, P N B I = 11.6 MW . This mode was observed at a frequency f = 156 kHz and was located at major radii 3.1 ⩽ R ( m ) ⩽ 3.3 . The observed mode was identified as a toroidal Alfvén eigenmode (TAE) using the linear MHD code, MISHKA. Beam ions and fusion-born alpha particles were modelled using the full orbit particle tracking code LOCUST, which produces smooth distribution functions suitable for stability calculations without analytical fits or the use of moments. We calculated the stability of the 21 candidate modes using the HALO code. These calculations revealed that beam ions can drive TAEs with toroidal mode numbers n ⩾ 8 with linear growth rates γ b / ω ∼ 1 % , while TAEs with n < 8 are damped by the beam ion population. Alpha particles drive modes with significantly smaller linear growth rates, γ α / ω ≲ 0.1 % due to the low alpha power generated almost exclusively by beam-thermal fusion reactions. Non-ideal effects were calculated using complex resistivity in the CASTOR code, leading to an assessment of radiative, collisional, and continuum damping for all 21 candidate modes. Ion Landau damping was modelled using Maxwellian distribution functions for bulk D and T ions in HALO. Radiative damping, the dominant bulk damping mechanism, suppresses modes with high toroidal mode numbers. Comparing the drive from energetic particles with damping from thermal particles, we find all but one of the candidate modes are damped. The single net-driven n = 9 TAE with a net growth rate γ n e t / ω = 0.02 % matches experimental observations with a lab frequency f = 163 kHz and location R = 3.3 m . The TAE was driven by co-passing particles through the v ∥ = v A / 5 resonance. Both co- and counter-passing alpha particles drive the TAE through the v ∥ = v A / 3 resonance. Additional sideband resonances contribute significant drive for both beam and alpha particles.

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“…2014), BEAMS3D (McMillan & Lazerson 2014), FOCUS (Clauser, Farengo & Ferrari 2019), LOCUST (Ward et al. 2021), OFMC (Tani et al. 1981), GNET (Masaoka & Murakami 2013), SPIRAL (Kramer et al.…”

Section: Introductionmentioning

confidence: 99%

Energetic particle tracing in optimized quasi-symmetric stellarator equilibria

Figueiredo,

Jorge,

Ferreira

et al. 2024

J. Plasma Phys.

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Recent developments in the design of magnetic confinement fusion devices have allowed the construction of exceptionally optimized stellarator configurations. The near-axis expansion in particular has been proven to enable the construction of magnetic configurations with good confinement properties while taking only a fraction of the usual computation time to generate optimized magnetic equilibria. However, not much is known about the overall features of fast-particle orbits computed in such analytical, yet simplified, equilibria when compared with those originating from accurate equilibrium solutions. This work aims to assess and demonstrate the potential of the near-axis expansion to provide accurate information on particle orbits and to compute loss fractions in moderate to high aspect ratios. The configurations used here are all scaled to fusion-relevant parameters and approximate quasi-symmetry to various degrees. This allows us to understand how deviations from quasi-symmetry affect particle orbits and what are their effects on the estimation of the loss fraction. Guiding-centre trajectories of fusion-born alpha particles are traced using gyronimo and SIMPLE codes under the NEAT framework, showing good numerical agreement. Discrepancies between near-axis and magnetohydrodynamic fields have minor effects on passing particles but significant effects on trapped particles, especially in quasi-helically symmetric magnetic fields. Effective expressions were found for estimating orbit widths and passing–trapped separatrix in quasi-symmetric near-axis fields. Loss fractions agree in the prompt losses regime but diverge afterwards.

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Verification and validation of the high-performance Lorentz-orbit code for use in stellarators and tokamaks (LOCUST)

Cited by 7 publications

References 47 publications

LOCUST-GPU predictions of fast-ion transport and power loads due to ELM-control coils in ITER

LOCUST-GPU predictions of fast-ion transport and power loads due to ELM-control coils in ITER

Toroidal Alfvén eigenmodes observed in low power JET deuterium–tritium plasmas

Energetic particle tracing in optimized quasi-symmetric stellarator equilibria

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