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 stochasiticity is naturally present in post-di...

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Bibliographic Details
Published in:arXiv.org 2016-06
Main Authors: Konsta Särkimäki, Hirvijoki, Eero, Decker, Joan, Varje, Jari, Kurki-Suonio, Taina
Format: Article
Language:English
Subjects:
Advection
Avalanches
Computer simulation
Diffusion
Diffusion coefficient
Disruption
Electron transport
Magnetic fields
Magnetic islands
Monte Carlo simulation
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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 stochasiticity 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:2331-8422
DOI:10.48550/arxiv.1606.04409