38 citations · 112 across the 14 of their papers we have counts for
14 papers
Geodesic extended modes in low magnetic shear tokamaks and stellarators
Richard Nies, Felix Parra
Theories of ion-scale microinstabilities in tokamaks and stellarators typically assume that the passing electrons respond adiabatically due to their fast propagation speed. However…
Energetic-particle orbits near rational flux surfaces in stellarators: I. Passing particles
Thomas E. Foster, Felix I. Parra, Roscoe B. White +3
Recent simulations have shown that, even when the magnetic field of a stellarator possesses nested toroidal flux surfaces, the orbits of passing energetic particles can exhibit isl…
Modification of ion-temperature-gradient turbulence by impurities in stellarator plasmas
Ivan Calvo, Felix I. Parra, Hanne Thienpondt +1
Recent nonlinear gyrokinetic simulations have shown that impurities can strongly modify the turbulent heat flux in stellarator plasmas. Here, the ion-temperature-gradient (ITG) dis…
Characteristics of monotonic sheaths near a wall with grazing magnetic incidence
Alessandro Geraldini, Robert J. Ewart, Stephan Brunner +1
We consider a magnetised plasma in contact with an absorbing planar wall, where the angle between the magnetic field and the wall is small, (in radians) and the system…
Piecewise omnigenous stellarators with zero bootstrap current
Ivan Calvo, Jose Luis Velasco, Per Helander +1
Until now, quasi-isodynamic magnetic fields have been the only known stellarator configurations that, at low collisionality, give small radial neoclassical transport and zero boots…
Theory of zonal flow growth and propagation in toroidal geometry
Richard Nies, Felix Parra
The toroidal geometry of tokamaks and stellarators is known to play a crucial role in the linear physics of zonal flows, leading to e.g. the Rosenbluth-Hinton residual and geodesic…
Strong gradient effects on neoclassical electron transport and the bootstrap current
Silvia Trinczek, Felix I. Parra, Peter J. Catto
Standard approaches to neoclassical theory do not extend into regions of strong gradients in tokamaks such as the pedestal and internal transport barriers. Here, we calculate the m…
Sheath constraints on turbulent magnetised plasmas
Alessandro Geraldini, Stephan Brunner, Felix I. Parra
A solid target in contact with a plasma charges (negatively) to reflect the more mobile species (electrons) and thus keep the bulk plasma quasineutral. To shield the bulk plasma fr…
Sheath collapse at critical shallow angle due to kinetic effects
Robert J Ewart, Felix I Parra, Alessandro Geraldini
The Debye sheath is known to vanish completely in magnetised plasmas for a sufficiently small electron gyroradius and small angle between the magnetic field and the wall. This angl…
KNOSOS: a fast orbit-averaging neoclassical code for stellarator geometry
J. L. Velasco, I. Calvo, F. I. Parra +1
KNOSOS (KiNetic Orbit-averaging SOlver for Stellarators) is a freely available, open-source code (\href{https://github.com/joseluisvelasco/KNOSOS}{https://github.com/joseluisvelasc…
Electrostatic potential variations on stellarator magnetic surfaces in low collisionality regimes
Ivan Calvo, J. L. Velasco, Felix I. Parra +2
The component of the neoclassical electrostatic potential that is non-constant on the magnetic surface, that we denote by , can affect radial transport of highly charged i…
Large tangential electric fields in plasmas close to temperature screening
J. L. Velasco, I. Calvo, J. M. García-Regaña +4
Low-collisionality stellarator plasmas usually display a large negative radial electric field that has been expected to cause accumulation of impurities due to their high charge nu…
Parallel impurity dynamics in the TJ-II stellarator
J A Alonso, J L Velasco, I Calvo +12
We review in a tutorial fashion some of the causes of impurity density variations along field lines and radial impurity transport in the moment approach framework. An explicit and…
Equivalence of two independent calculations of the higher order guiding center Lagrangian
F. I. Parra, I. Calvo, J. W. Burby +2
The difference between the guiding center phase-space Lagrangians derived in [J.W. Burby, J. Squire, and H. Qin, Phys. Plasmas {\bf 20}, 072105 (2013)] and [F.I. Parra, and I. Calv…