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Author: Leopoldo Carbajal
Requested Type: Poster
Submitted: 2018-03-01 13:39:14

Co-authors: D. del-Castillo-Negrete

Contact Info:
Oak Ridge National Laboratory
1 Bethel Valley Rd
Oak Ridge, TN   37831

Abstract Text:
In this work we present the validation of theoretical models for the pitch-angle probability distribution functions (PDFs) of runaway electrons (RE) through simulations of synchrotron radiation (SR) of RE in DIII-D quiescent plasmas, that is, RE occurring in a hot (~keV) and low-density (<1019 m-3) plasma where the magnetic flux surfaces remain well formed. In these plasmas the energy PDF is known but the pitch-angle PDF is poorly understood [1]. The main features of the measured SR in DIII-D quiescent plasmas are recovered by our simulations when the spreading in the pitch-angle PDF is different to what is predicted by theoretical estimates that only consider the pitch-angle scattering driven by collisions balancing the pinching in pitch angle caused by the electric field. SR of RE in magnetically confinement fusion plasmas is important because it provides a limiting mechanism of the maximum energy that RE can reach, and because it can be used as a diagnostic to infer parameters of the RE energy and pitch-angle distribution functions. The accuracy of the inferred parameters strongly depends on the different physical effects included when interpreting the measurements. Recent studies [2,3] have shown that SR depends on the energy of the RE and their spatial distribution, but most importantly it is very sensitive to different models used for the pitch-angle.
*Research sponsored by the Office of Fusion Energy Sciences of the U.S. DOE at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725, and by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory.
[1] C. Paz-Soldan et al., Phys. Rev. Lett. 118, 255002 (2017)
[2] L. Carbajal et al., Plasma Phys. Control. Fusion 59, 124001 (2017)
[3] D. del-Castillo-Negrete et al., Phys. Plasmas, accepted (2017)