KNOSOS: A fast orbit-averaging neoclassical code for stellarator geometry

J. L. Velasco, I. Calvo, F. I. Parra, J. M. García-Regaña

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


KNOSOS (KiNetic Orbit-averaging SOlver for Stellarators) is a freely available, open-source code ( that calculates neoclassical transport in low-collisionality plasmas of three-dimensional magnetic confinement devices by solving the radially local drift-kinetic and quasineutrality equations. The main feature of KNOSOS is that it relies on orbit-averaging to solve the drift-kinetic equation very fast. KNOSOS treats rigorously the effect of the component of the magnetic drift that is tangent to magnetic surfaces, and of the component of the electrostatic potential that varies on the flux surface, φ1. Furthermore, the equation solved is linear in φ1, which permits an efficient solution of the quasineutrality equation. As long as the radially local approach is valid, KNOSOS can be applied to the calculation of neoclassical transport in stellarators (helias, heliotrons, heliacs, etc.) and tokamaks with broken axisymmetry. In this paper, we show several calculations for the stellarators W7-X, LHD, NCSX and TJ-II that provide benchmark with standard local codes and demonstrate the advantages of this approach.

Original languageEnglish (US)
Article number109512
JournalJournal of Computational Physics
StatePublished - Oct 1 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Numerical Analysis
  • Modeling and Simulation
  • Physics and Astronomy (miscellaneous)
  • General Physics and Astronomy
  • Computer Science Applications
  • Computational Mathematics
  • Applied Mathematics


  • Magnetic confinement fusion
  • Neoclassical theory
  • Optimisation
  • Stellarators
  • Transport


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