An advection-diffusion model for cross-field runaway electron transport in perturbed magnetic fields

Disruption-generated runaway electrons (RE) present an outstanding issue for ITER. The predictive computational studies of RE generation rely on orbit-averaged computations and, as such, they lack the effects from the magnetic field stochasticity. Since stochasticity is naturally present in post-dis...

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Bibliographic Details
Published in:Plasma physics and controlled fusion 2016-12, Vol.58 (12), p.125017
Main Authors: Särkimäki, Konsta, Hirvijoki, Eero, Decker, Joan, Varje, Jari, Kurki-Suonio, Taina
Format: Article
Language:English
Subjects:
advection
diffusion
radial transport
runaway electron
stochastic magnetic field
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Summary:Disruption-generated runaway electrons (RE) present an outstanding issue for ITER. The predictive computational studies of RE generation rely on orbit-averaged computations and, as such, they lack the effects from the magnetic field stochasticity. Since stochasticity is naturally present in post-disruption plasma, and externally induced stochastization offers a prominent mechanism to mitigate RE avalanche, we present an advection-diffusion model that can be used to couple an orbit-following code to an orbit-averaged tool in order to capture the cross-field transport and to overcome the latter's limitation. The transport coefficients are evaluated via a Monte Carlo method. We show that the diffusion coefficient differs significantly from the well-known Rechester-Rosenbluth result. We also demonstrate the importance of including the advection: it has a two-fold role both in modelling transport barriers created by magnetic islands and in amplifying losses in regions where the islands are not present.
ISSN:0741-3335
1361-6587
1361-6587
DOI:10.1088/0741-3335/58/12/125017