2022
3.
Muir, Dean; Pfefferlé, David; Qu, Zhisong; Hole, Matthew; Hegland, Markus
Numerical Integration of Particle Orbits in Discontinuous Fields Using VENUS-LEVIS and SPEC Journal Article
In: Computer Physics Communications, vol. 271, pp. 108191, 2022, ISSN: 0010-4655.
Abstract | Links | BibTeX | Tags: discontinuous fields, full-orbit, numerical method, SPEC, VENUS-LEVIS
@article{muirNumericalIntegrationParticle2022,
title = {Numerical Integration of Particle Orbits in Discontinuous Fields Using VENUS-LEVIS and SPEC},
author = {Dean Muir and David Pfefferl\'{e} and Zhisong Qu and Matthew Hole and Markus Hegland},
doi = {10.1016/j.cpc.2021.108191},
issn = {0010-4655},
year = {2022},
date = {2022-02-01},
urldate = {2022-02-01},
journal = {Computer Physics Communications},
volume = {271},
pages = {108191},
abstract = {The orbit code VENUS-LEVIS is adapted to follow particles in plasma equilibria with discontinuous fields generated by the Stepped Pressure Equilibrium Code (SPEC). The latter is an implementation of the Multi-Region relaxed MHD model, which efficiently computes Taylor states in a series of nested toroidal volumes and supports the formation of magnetic islands and chaotic field regions. To adapt VENUS-LEVIS, an event location procedure is implemented in the existing numerical integrator, which ensures the particle sees the correct field along its trajectory, regardless of the discontinuities present in the Stepped Pressure Equilibrium model. The algorithm is tested in the case where the magnetic field is uniform in the upper and lower half-spaces but has a discontinuity in its direction (shear) on the plane z=0. Particle drifts due to the discontinuity are studied. The convergence properties of the numerical scheme are highlighted by the numerical accuracy, and conservation of the system's invariants, such as energy and momentum. Simulations and convergence studies using the SPEC-LEVIS interface in axisymmetric geometry are then presented. Finally, illustrative particle drifts due to the discontinuity are studied and explained: we examine drifts associated with the change in Larmor radius of passing particles with small excursion from flux surfaces.},
keywords = {discontinuous fields, full-orbit, numerical method, SPEC, VENUS-LEVIS},
pubstate = {published},
tppubtype = {article}
}
The orbit code VENUS-LEVIS is adapted to follow particles in plasma equilibria with discontinuous fields generated by the Stepped Pressure Equilibrium Code (SPEC). The latter is an implementation of the Multi-Region relaxed MHD model, which efficiently computes Taylor states in a series of nested toroidal volumes and supports the formation of magnetic islands and chaotic field regions. To adapt VENUS-LEVIS, an event location procedure is implemented in the existing numerical integrator, which ensures the particle sees the correct field along its trajectory, regardless of the discontinuities present in the Stepped Pressure Equilibrium model. The algorithm is tested in the case where the magnetic field is uniform in the upper and lower half-spaces but has a discontinuity in its direction (shear) on the plane z=0. Particle drifts due to the discontinuity are studied. The convergence properties of the numerical scheme are highlighted by the numerical accuracy, and conservation of the system's invariants, such as energy and momentum. Simulations and convergence studies using the SPEC-LEVIS interface in axisymmetric geometry are then presented. Finally, illustrative particle drifts due to the discontinuity are studied and explained: we examine drifts associated with the change in Larmor radius of passing particles with small excursion from flux surfaces.
2020
2.
Lazerson, Samuel A; Ford, Oliver P; Nuehrenberg, Carolin; Äkäslompolo, Simppa; Poloskei, Peter Zs.; Machielsen, Mike; McNeely, Paul; Vanó, Lilla; Rust, Norbert; Bozhenkov, Sergey; Neelis, Tristan W C; Graves, Jonathan P; Pfefferlé, David; Spanier, Annabelle; Hartmann, Dirk; Marushchenko, Nikolai; Turkin, Yuriy; Hirsch, Matthias; Chaudhary, Neha; Hoefel, Udo; Stange, Torsten; Weir, Gavin; Pablant, Novimir; Langenberg, Andreas; Traverso, Peter; Valson, Pranay; Knauer, Jens; Brunner, Kai Jakob; Pasch, Ekkehard; Beurskens, Marc; Damm, Hannes; Fuchert, Golo; Nelde, Philipp; Scott, Evan; Hergenhahn, Uwe; Pavone, Andrea; Rahbarnia, Kian; Andreeva, Tamara; Schilling, Jonathan; Brandt, Christian; Neuner, Ulrich; Thomsen, Henning; Jakubowski, Marcin; Ali, Adnan; Gao, Yu; Niemann, Holger; Sitjes, Aleix Puig; Koenig, Ralf; and, Robert Wolf C
Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X Journal Article
In: Nuclear Fusion, vol. 60, no. 7, pp. 076020, 2020.
Abstract | Links | BibTeX | Tags: fast particles, full-orbit, guiding-centre, neoclassical transport, stellarator
@article{lazerson-2020,
title = {Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X},
author = {Samuel A Lazerson and Oliver P Ford and Carolin Nuehrenberg and Simppa \"{A}k\"{a}slompolo and Peter Zs. Poloskei and Mike Machielsen and Paul McNeely and Lilla Van\'{o} and Norbert Rust and Sergey Bozhenkov and Tristan W C Neelis and Jonathan P Graves and David Pfefferl\'{e} and Annabelle Spanier and Dirk Hartmann and Nikolai Marushchenko and Yuriy Turkin and Matthias Hirsch and Neha Chaudhary and Udo Hoefel and Torsten Stange and Gavin Weir and Novimir Pablant and Andreas Langenberg and Peter Traverso and Pranay Valson and Jens Knauer and Kai Jakob Brunner and Ekkehard Pasch and Marc Beurskens and Hannes Damm and Golo Fuchert and Philipp Nelde and Evan Scott and Uwe Hergenhahn and Andrea Pavone and Kian Rahbarnia and Tamara Andreeva and Jonathan Schilling and Christian Brandt and Ulrich Neuner and Henning Thomsen and Marcin Jakubowski and Adnan Ali and Yu Gao and Holger Niemann and Aleix Puig Sitjes and Ralf Koenig and Robert Wolf C and},
url = {https://doi.org/10.1088%2F1741-4326%2Fab8e61},
doi = {10.1088/1741-4326/ab8e61},
year = {2020},
date = {2020-06-01},
journal = {Nuclear Fusion},
volume = {60},
number = {7},
pages = {076020},
publisher = {IOP Publishing},
abstract = {The neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were reconstructed. These discharges scanned the magnetic configurations and plasma densities of W7-X. The equilibrium reconstructions were performed using STELLOPT which calculates three-dimensional self-consistent ideal magnetohydrodynamic equilibria and kinetic profiles. These reconstructions leveraged new capabilities to incorporate electron cyclotron emission and x-ray imaging diagnostics in the STELLOPT code. The reconstructed equilibria and profiles served as inputs for BEAMS3D calculations of neutral beam deposition in W7-X. It is found that if reconstructed kinetic profiles are utilized, good agreement between measured and simulated beam attenuation is found. As deposition models provide initial conditions for fast-ion slowing down calculations, this work provides a first step towards validating our ability to predict fast ion confinement in stellarators.},
keywords = {fast particles, full-orbit, guiding-centre, neoclassical transport, stellarator},
pubstate = {published},
tppubtype = {article}
}
The neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were reconstructed. These discharges scanned the magnetic configurations and plasma densities of W7-X. The equilibrium reconstructions were performed using STELLOPT which calculates three-dimensional self-consistent ideal magnetohydrodynamic equilibria and kinetic profiles. These reconstructions leveraged new capabilities to incorporate electron cyclotron emission and x-ray imaging diagnostics in the STELLOPT code. The reconstructed equilibria and profiles served as inputs for BEAMS3D calculations of neutral beam deposition in W7-X. It is found that if reconstructed kinetic profiles are utilized, good agreement between measured and simulated beam attenuation is found. As deposition models provide initial conditions for fast-ion slowing down calculations, this work provides a first step towards validating our ability to predict fast ion confinement in stellarators.
2015
1.
Pfefferlé, D; Graves, J P; Cooper, W A
Hybrid guiding-centre/full-orbit simulations in non-axisymmetric magnetic geometry exploiting general criterion for guiding-centre accuracy Journal Article
In: Plasma Physics and Controlled Fusion, vol. 57, no. 5, pp. 054017, 2015.
Abstract | Links | BibTeX | Tags: fast particles, full-orbit, guiding-centre, neoclassical transport, neutral beam injection, VENUS-LEVIS
@article{pfefferle-hybrid,
title = {Hybrid guiding-centre/full-orbit simulations in non-axisymmetric magnetic geometry exploiting general criterion for guiding-centre accuracy},
author = {D Pfefferl\'{e} and J P Graves and W A Cooper},
url = {http://stacks.iop.org/0741-3335/57/i=5/a=054017},
doi = {10.1088/0741-3335/57/5/054017},
year = {2015},
date = {2015-04-15},
journal = {Plasma Physics and Controlled Fusion},
volume = {57},
number = {5},
pages = {054017},
abstract = {To identify under what conditions guiding-centre or full-orbit tracing should be used, an estimation of the spatial variation of the magnetic field is proposed, not only taking into account gradient and curvature terms but also parallel currents and the local shearing of field-lines. The criterion is derived for general three-dimensional magnetic equilibria including stellarator plasmas. Details are provided on how to implement it in cylindrical coordinates and in flux coordinates that rely on the geometric toroidal angle. A means of switching between guiding-centre and full-orbit equations at first order in Larmor radius with minimal discrepancy is shown. Techniques are applied to a MAST (mega amp spherical tokamak) helical core equilibrium in which the inner kinked flux-surfaces are tightly compressed against the outer axisymmetric mantle and where the parallel current peaks at the nearly rational surface. This is put in relation with the simpler situation B(x, y, z) = B0[sin(kx)ey + cos(kx)ez], for which full orbits and lowest order drifts are obtained analytically. In the kinked equilibrium, the full orbits of NBI fast ions are solved numerically and shown to follow helical drift surfaces. This result partially explains the off-axis redistribution of neutral beam injection fast particles in the presence of MAST long-lived modes (LLM).},
keywords = {fast particles, full-orbit, guiding-centre, neoclassical transport, neutral beam injection, VENUS-LEVIS},
pubstate = {published},
tppubtype = {article}
}
To identify under what conditions guiding-centre or full-orbit tracing should be used, an estimation of the spatial variation of the magnetic field is proposed, not only taking into account gradient and curvature terms but also parallel currents and the local shearing of field-lines. The criterion is derived for general three-dimensional magnetic equilibria including stellarator plasmas. Details are provided on how to implement it in cylindrical coordinates and in flux coordinates that rely on the geometric toroidal angle. A means of switching between guiding-centre and full-orbit equations at first order in Larmor radius with minimal discrepancy is shown. Techniques are applied to a MAST (mega amp spherical tokamak) helical core equilibrium in which the inner kinked flux-surfaces are tightly compressed against the outer axisymmetric mantle and where the parallel current peaks at the nearly rational surface. This is put in relation with the simpler situation B(x, y, z) = B0[sin(kx)ey + cos(kx)ez], for which full orbits and lowest order drifts are obtained analytically. In the kinked equilibrium, the full orbits of NBI fast ions are solved numerically and shown to follow helical drift surfaces. This result partially explains the off-axis redistribution of neutral beam injection fast particles in the presence of MAST long-lived modes (LLM).