Impurity transport and bulk ion flow in a mixed collisionality stellarator plasma

Abstract

The accumulation of impurities in the core of magnetically confined plasmas, resulting from standard collisional transport mechanisms, is a known threat to their performance as fusion energy sources. Whilst the axisymmetric tokamak systems have been shown to benefit from the effect of temperature screening, that is an outward flux of impurities driven by the temperature gradient, impurity accumulation in stellarators was thought to be inevitable, driven robustly by the inward pointing electric field characteristic of hot fusion plasmas. We have shown in Helander et. al. (2017b) that such screening can in principle also appear in stellarators, in the experimentally relevant mixed collisionality regime, where a highly collisional impurity species is present in a low collisionality bulk plasma. Details of the analytic calculation are presented here, along with the effect of the impurity on the bulk ion flow, which will ultimately affect the bulk contribution to the bootstrap current.

References in corpus (9)

• Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas
• An improved current potential method for fast computation of stellarator coil shapes
• The effect of tangential drifts on neoclassical transport in stellarators close to omnigeneity
• Impurity transport in a mixed-collisionality stellarator plasma
• Moderation of neoclassical impurity accumulation in high temperature plasmas of helical devices
• Stellarator bootstrap current and plasma flow velocity at low collisionality
• Impurities in a non-axisymmetric plasma: transport and effect on bootstrap current
• Optimizing stellarators for large flows
• Flow damping in stellarators close to quasisymmetry

Cited by in corpus (12)

• Collisional transport of impurities with flux-surface varying density in stellarators
• Strategies for Advantageous Differential Transport of Ions in Magnetic Fusion Devices
• Quasilinear particle transport from gyrokinetic instabilities in general magnetic geometry
• Study on impurity hole plasmas by global neoclassical simulation
• Maximum-Entropy States for Magnetized Ion Transport
• MITNS: Multiple-Ion Transport Numerical Solver for Magnetized Plasmas
• Heat Pump via Charge Incompressibility in a Collisional Magnetized Multi-Ion Plasma
• The importance of the classical channel in the impurity transport of optimized stellarators
• Generalized Impurity Pinch in Partially Magnetized Multi-Ion Plasma
• Trace Impurity Transport in Multi-Species Plasmas with Large Particle Fluxes
• Temperature Screening and Cross-Field Impurity Accumulation from a Thermodynamic Perspective
• Optimization of flux-surface density variation in stellarator plasmas with respect to the transport of collisional impurities