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

Abstract

Developing avoidance or mitigation strategies of runaway electrons (REs) 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 REs 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 REs. We observe a strong dependence of the synchrotron emission measured by the camera on the pitch angle distribution of runaways, namely we find that crescent shapes of the spatial distribution of the SR asmore » 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 runaways and by approximately 60 times for mono-energetic distributions of runaways1.« less

Authors:
ORCiD logo [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE
OSTI Identifier:
1526627
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 12; Journal ID: ISSN 0741-3335
Country of Publication:
United States
Language:
English

Citation Formats

Carbajal, L., and del-Castillo-Negrete, D. On the synchrotron emission in kinetic simulations of runaway electrons in magnetic confinement fusion plasmas. United States: N. p., 2017. Web. doi:10.1088/1361-6587/aa883e.
Carbajal, L., & del-Castillo-Negrete, D. On the synchrotron emission in kinetic simulations of runaway electrons in magnetic confinement fusion plasmas. United States. https://doi.org/10.1088/1361-6587/aa883e
Carbajal, L., and del-Castillo-Negrete, D. 2017. "On the synchrotron emission in kinetic simulations of runaway electrons in magnetic confinement fusion plasmas". United States. https://doi.org/10.1088/1361-6587/aa883e.
@article{osti_1526627,
title = {On the synchrotron emission in kinetic simulations of runaway electrons in magnetic confinement fusion plasmas},
author = {Carbajal, L. and del-Castillo-Negrete, D.},
abstractNote = {Developing avoidance or mitigation strategies of runaway electrons (REs) 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 REs 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 REs. We observe a strong dependence of the synchrotron emission measured by the camera on the pitch angle distribution of runaways, 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 runaways and by approximately 60 times for mono-energetic distributions of runaways1.},
doi = {10.1088/1361-6587/aa883e},
url = {https://www.osti.gov/biblio/1526627}, journal = {Plasma Physics and Controlled Fusion},
issn = {0741-3335},
number = 12,
volume = 59,
place = {United States},
year = {2017},
month = {10}
}