On the synchrotron emission in kinetic simulations of runaway electrons in magnetic confinement fusion plasmas

Abstract

Developing avoidance or mitigation strategies of runaway electrons (RE) in magnetic confinement fusion (MCF) plasmas is of crucial importance for the safe operation of ITER. In order to develop these strategies, an accurate diagnostic capability that allows good estimates of the RE distribution function in these plasmas is needed. Synchrotron radiation (SR) of RE in MCF, besides of being one of the main damping mechanisms for RE in the high energy relativistic regime, is routinely used in current MCF experiments to infer the parameters of RE energy and pitch angle distribution functions. In the present paper we address the long standing question about what are the relationships between different RE distribution functions and their corresponding synchrotron emission simultaneously including: full-orbit effects, information of the spectral and angular distribution of SR of each electron, and basic geometric optics of a camera. We study the spatial distribution of the SR on the poloidal plane, and the statistical properties of the expected value of the synchrotron spectra of runaway electrons. We observe a strong dependence of the synchrotron emission measured by the camera on the pitch angle distribution of RE, namely we find that crescent shapes of the spatial distribution of the SR as measured by the camera relate to RE distributions with small pitch angles, while ellipse shapes relate to distributions of runaways with larger the pitch angles. A weak dependence of the synchrotron emission measured by the camera with the RE energy, value of the q-profile at the edge, and the chosen range of wavelengths is observed. Furthermore, we find that oversimplifying the angular dependence of the SR changes the shape of the synchrotron spectra, and overestimates its amplitude by approximately 20 times for avalanching RE and by approximately 60 times for mono-energetic distributions of runaways.

arXiv commentWork presented at the Sherwood Fusion Theory Conference 2017 as an invited talk

References in corpus (4)

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• Numerical calculation of the runaway electron distribution function and associated synchrotron emission
• Synchrotron radiation from a runaway electron distribution in tokamaks
• Multi-scale Full-orbit Analysis on Phase-space Behavior of Runaway Electrons in Tokamak Fields with Synchrotron Radiation

Cited by in corpus (8)

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• Spatiotemporal evolution of runaway electrons from synchrotron images in Alcator C-Mod
• Measurements of runaway electron synchrotron spectra at high magnetic fields in Alcator C-Mod
• Runaway electron synchrotron radiation in a vertically translated plasma
• Spatially-dependent modeling and simulation of runaway electron mitigation in DIII-D
• A fluid-kinetic framework for self-consistent runaway-electron simulations
• Feasibility of the EDICAM camera for runaway electron detection in JT-60SA disruptions