87 citations · 1.2k across the 60 of their papers we have counts for
62 papers
Robust stellarator optimization via flat mirror magnetic fields
J. L. Velasco, I. Calvo, E. Sánchez +1
Stellarator magnetic configurations need to be optimized in order to meet all the required properties of a fusion reactor. In this work, it is shown that a flat-mirror quasi-isodyn…
Neoclassical transport in strong gradient regions of large aspect ratio tokamaks
Silvia Trinczek, Felix I. Parra, Peter J. Catto +2
We present a new neoclassical transport model for large aspect ratio tokamaks where the gradient scale lengths are of the size of the poloidal gyroradius. Previous work on neoclass…
Effect of mismatch on Doppler backscattering in MAST and MAST-U plasmas
Valerian H. Hall-Chen, Felix I. Parra, Jon C. Hillesheim +14
The Doppler backscattering (DBS) diagnostic, also referred to as Doppler reflectometry, measures turbulent density fluctuations of intermediate length scales. However, when the bea…
Validating and optimising mismatch tolerance of Doppler backscattering measurements with the beam model
Valerian H. Hall-Chen, Julius Damba, Felix I. Parra +11
We use the beam model of Doppler backscattering (DBS), which was previously derived from beam tracing and the reciprocity theorem, to shed light on mismatch attenuation. This atten…
Three-Dimensional Inhomogeneity of Electron-Temperature-Gradient Turbulence in the Edge of Tokamak Plasmas
J. F. Parisi, F. I. Parra, C. M. Roach +15
Nonlinear multiscale gyrokinetic simulations of a Joint European Torus edge pedestal are used to show that electron-temperature-gradient (ETG) turbulence has a rich three-dimension…
Finite orbit width effects in large aspect ratio stellarators
Vincent d'Herbemont, Felix I. Parra, Ivan Calvo +1
New orbit averaged equations for low collisionality neoclassical fluxes in large aspect ratio stellarators with mirror ratios close to unity are derived. The equations retain finit…
Beam model of Doppler backscattering
Valerian H Hall-Chen, Felix I Parra, Jon C Hillesheim
We use beam tracing -- implemented with a newly-written code, Scotty -- and the reciprocity theorem to derive a model for the linear backscattered power of the Doppler Backscatteri…
Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons
M. R. Hardman, F. I. Parra, C. Chong +6
Ion-gyroradius-scale microinstabilities typically have a frequency comparable to the ion transit frequency. Due to the small electron-to-ion mass ratio and the large electron trans…
Electrostatic gyrokinetic simulations in Wendelstein 7-X geometry: benchmark between the codes stella and GENE
A. González-Jerez, P. Xanthopoulos, J. M. García-Regaña +6
The first experimental campaigns have proven that, due to the optimization of the magnetic configuration with respect to neoclassical transport, the contribution of turbulence is e…
A model for the fast evaluation of prompt losses of energetic ions in stellarators
J. L. Velasco, I. Calvo, S. Mulas +4
A good understanding of the confinement of energetic ions in non-axisymmetric magnetic fields is key for the design of reactors based on the stellarator concept. In this work, we d…
Gyrokinetic simulations in stellarators using different computational domains
E. Sánchez, J. M. García-Regaña, A. Bañón Navarro +9
In this work, we compare gyrokinetic simulations in stellarators using different computational domains, namely, flux tube, full-flux-surface, and radially global domains. Two probl…
Fast simulations for large aspect ratio stellarators with the neoclassical code KNOSOS
J. L. Velasco, I. Calvo, F. I. Parra +5
In this work, a new version of KNOSOS is presented. KNOSOS is a low-collisionality radially-local, bounce-averaged neoclassical code that is extremely fast, and at the same time, i…
Turbulent transport of impurities in 3D devices
J. M. García-Regaña, M. Barnes, I. Calvo +5
A large diffusive turbulent contribution to the radial impurity transport in Wendelstein 7-X (W7-X) plasmas has been experimentally inferred during the first campaigns and numerica…
Turbulent impurity transport simulations in Wendelstein 7-X plasmas
J. M. García-Regaña, M. Barnes, I. Calvo +8
A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried ou…
Toroidal and slab ETG instability dominance in the linear spectrum of JET-ILW pedestals
Jason F. Parisi, Felix I. Parra, Colin M. Roach +9
Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for in the steep gradient regio…
Dependence on ion temperature of shallow-angle magnetic presheaths with adiabatic electrons
Alessandro Geraldini, Felix I Parra, Fulvio Militello
The magnetic presheath is a boundary layer occurring when magnetized plasma is in contact with a wall and the angle between the wall and the magnetic field is oblique…
Impact of main ion pressure anisotropy on stellarator impurity transport
Ivan Calvo, Felix I. Parra, J. L. Velasco +1
Main ions influence impurity dynamics through a variety of mechanisms; in particular, via impurity-ion collisions. To lowest order in an expansion in the main ion mass over the imp…
Intrinsic rotation driven by turbulent acceleration
Michael Barnes, Felix I. Parra
Differential rotation is induced in tokamak plasmas when an underlying symmetry of the governing gyrokinetic-Maxwell system of equations is broken. One such symmetry-breaking mecha…
: a mixed implicit-explicit, delta-f gyrokinetic code for general magnetic field configurations
Michael Barnes, Felix Parra-Diaz, Matt Landreman
Here we present details of a mixed implicit-explicit numerical scheme for the solution of the gyrokinetic-Poisson system of equations in the local limit. This scheme has been imple…
Solution to a collisionless shallow-angle magnetic presheath with kinetic ions
Alessandro Geraldini, Felix I. Parra, Fulvio Militello
Using a kinetic model for the ions and adiabatic electrons, we solve a steady state, electron-repelling magnetic presheath in which a uniform magnetic field makes a small angle $α\…
Stellarator impurity flux driven by electric fields tangent to magnetic surfaces
Ivan Calvo, Felix I. Parra, J. L. Velasco +2
The control of impurity accumulation is one of the main challenges for future stellarator fusion reactors. The standard argument to explain this accumulation relies on the, in prin…
Electromagnetic zonal flow residual responses
Peter J. Catto, Felix I. Parra, Istvan Pusztai
The collisionless axisymmetric zonal flow residual calculation for a tokamak plasma is generalized to include electromagnetic perturbations. We formulate and solve the complete ini…
Optimized up-down asymmetry to drive fast intrinsic rotation in tokamaks
Justin Ball, Felix I. Parra, Matt Landreman +1
Breaking the up-down symmetry of the tokamak poloidal cross-section can significantly increase the spontaneous rotation due to turbulent momentum transport. In this work, we optimi…
Semianalytical calculation of the zonal-flow oscillation frequency in stellarators
Pedro Monreal, Edilberto Sánchez, Iván Calvo +5
Due to their capability to reduce turbulent transport in magnetized plasmas, understanding the dynamics of zonal flows is an important problem in the fusion programme. Since the pi…