Kinetic effects of partially screened impurities in runaway-electron mitigation scenarios
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2017

Runaway electrons constitute a significant threat to tokamak devices. Their mitigation by heavy-impurity injection has been experimentally shown to be more effective than would be expected from standard collisional theory [1]. In order to understand this effect and develop runaway mitigation schemes, more accurate kinetic models are needed to describe the interaction between electrons and partially ionized atoms. Such models require the partial screening of the nuclei by the bound electrons to be taken into account. In this contribution, we analyze the dynamics of fast electrons in plasmas containing partially ionized impurity atoms. A generalized collision operator is derived from first principles using quantum-mechanical models. We obtain analytical expressions for the deflection and slowing-down frequencies. Even at sub-relativistic energies, these are increased by more than an order of magnitude compared to the results obtained with complete screening. Moreover, we implement the generalized collision operator in the continuum kinetic-equation solver CODE [2, 3] and demonstrate that interaction with partially ionized atoms greatly affects fast-electron dynamics by enhancing the rates of angular deflection and energy loss. In particular, we investigate the decay of a runaway-electron current coupled to a self-consistent electric field. The effect of the interaction with partially ionized impurities has important implications for the efficacy of mitigation strategies for runaway electrons in tokamak devices. References [1] E. M. Hollmann et al., Physics of Plasmas 22, 056108 (2015). [2] M. Landreman, A. Stahl and T. Fülöp, Comp. Phys. Comm. 185, 847 (2014). [3] A. Stahl et al., Nuclear Fusion 56, 112009 (2016).

Författare

Linnea Hesslow

Chalmers, Fysik, Subatomär fysik och plasmafysik

Ola Embréus

Chalmers, Fysik, Subatomär fysik och plasmafysik

George Wilkie

Chalmers, Fysik, Subatomär fysik och plasmafysik

Adam Stahl

Chalmers, Fysik, Subatomär fysik och plasmafysik

Timothy Dubois

Chalmers, Fysik, Subatomär fysik och plasmafysik

Sarah Newton

Chalmers, Fysik, Subatomär fysik och plasmafysik

Tünde Fülöp

Chalmers, Fysik, Subatomär fysik och plasmafysik

International Sherwood Fusion Theory Conference, Annapolis, USA

Drivkrafter

Hållbar utveckling

Styrkeområden

Energi

Fundament

Grundläggande vetenskaper

Ämneskategorier

Fusion, plasma och rymdfysik

Mer information

Skapat

2017-12-29