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Title: Space dependent, full orbit effects on runaway electron dynamics in tokamak plasmas

Authors:
 [1]; ORCiD logo [1];  [1];  [1]; ORCiD logo [1]
  1. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1375656
Alternate Identifier(s):
OSTI ID: 1420618
Resource Type:
Journal Article: Published Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 4; Related Information: CHORUS Timestamp: 2017-08-21 09:22:13; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Carbajal, L., del-Castillo-Negrete, D., Spong, D., Seal, S., and Baylor, L.. Space dependent, full orbit effects on runaway electron dynamics in tokamak plasmas. United States: N. p., 2017. Web. doi:10.1063/1.4981209.
Carbajal, L., del-Castillo-Negrete, D., Spong, D., Seal, S., & Baylor, L.. Space dependent, full orbit effects on runaway electron dynamics in tokamak plasmas. United States. doi:10.1063/1.4981209.
Carbajal, L., del-Castillo-Negrete, D., Spong, D., Seal, S., and Baylor, L.. Tue . "Space dependent, full orbit effects on runaway electron dynamics in tokamak plasmas". United States. doi:10.1063/1.4981209.
@article{osti_1375656,
title = {Space dependent, full orbit effects on runaway electron dynamics in tokamak plasmas},
author = {Carbajal, L. and del-Castillo-Negrete, D. and Spong, D. and Seal, S. and Baylor, L.},
abstractNote = {},
doi = {10.1063/1.4981209},
journal = {Physics of Plasmas},
number = 4,
volume = 24,
place = {United States},
year = {Tue Apr 18 00:00:00 EDT 2017},
month = {Tue Apr 18 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4981209

Citation Metrics:
Cited by: 3works
Citation information provided by
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  • Cited by 3
  • In this paper, the secular full-orbit simulations of runaway electrons with synchrotron radiation in tokamak fields are carried out using a relativistic volume-preserving algorithm. Detailed phase-space behaviors of runaway electrons are investigated in different dynamical timescales spanning 11 orders. In the small timescale, i.e., the characteristic timescale imposed by Lorentz force, the severely deformed helical trajectory of energetic runaway electron is witnessed. A qualitative analysis of the neoclassical scattering, a kind of collisionless pitch-angle scattering phenomena, is provided when considering the coupling between the rotation of momentum vector and the background magnetic field. In large timescale up to 1 s,more » it is found that the initial condition of runaway electrons in phase space globally influences the pitch-angle scattering, the momentum evolution, and the loss-gain ratio of runaway energy evidently. However, the initial value has little impact on the synchrotron energy limit. It is also discovered that the parameters of tokamak device, such as the toroidal magnetic field, the loop voltage, the safety factor profile, and the major radius, can modify the synchrotron energy limit and the strength of neoclassical scattering. The maximum runaway energy is also proved to be lower than the synchrotron limit when the magnetic field ripple is considered.« less
  • A test particle description of the runaway dynamics [J.R. Mart{acute i}n-Sol{acute i}s {ital et al.}, Phys. Plasmas {bold 5}, 2370 (1998)] is extended to investigate the behavior of runaway electrons in the presence of fluctuations of electric and magnetic fields. The interaction with the fluctuations is accounted for via a friction force with an effective {open_quotes}collision{close_quotes} frequency determined by the fluctuation induced radial diffusion coefficient. It is shown that both the runaway generation process and the maximum runaway energy can be noticeably affected by magnetic fluctuations. The test particle model is then used to discuss a proposed runaway control schememore » via induced magnetic turbulence, with particular emphasis to situations like major disruptions, where a large number of runaway electrons and high runaway energies are expected. It is found that the efficiency of such scheme can in some cases be jeopardized by drift orbit effects as well as by the coexistence of stochastic magnetic regions with good magnetic surfaces. {copyright} {ital 1999 American Institute of Physics.}« less
  • The dynamics of high energy runaway electrons is analyzed for plasmas with high impurity content. It is shown that modified collision terms are required in order to account for the collisions of the relativistic runaway electrons with partially stripped impurity ions, including the effect of the collisions with free and bound electrons, as well as the scattering by the full nuclear and the electron-shielded ion charge. The effect of the impurities on the avalanche runaway growth rate is discussed. The results are applied, for illustration, to the interpretation of the runaway electron behavior during disruptions, where large amounts of impuritiesmore » are expected, particularly during disruption mitigation by massive gas injection. The consequences for the electron synchrotron radiation losses and the resulting runaway electron dynamics are also analyzed.« less
  • In this paper, it will be shown that the runaway phenomenon in tokamak plasmas cannot be reduced to a one-dimensional problem, based on the competence between electric field acceleration and collisional friction losses in the parallel direction. A Langevin approach, including collisional diffusion in velocity space, will be used to analyze the two-dimensional runaway electron dynamics. An investigation of the runaway probability in velocity space will yield a criterion for runaway, which will be shown to be consistent with the results provided by the more simple test particle description of the runaway dynamics [Fuchs et al., Phys. Fluids 29, 2931more » (1986)]. Electron perpendicular collisional scattering will be found to play an important role, relaxing the conditions for runaway. Moreover, electron pitch angle scattering perpendicularly broadens the runaway distribution function, increasing the electron population in the runaway plateau region in comparison with what it should be expected from electron acceleration in the parallel direction only. The perpendicular broadening of the runaway distribution function, its dependence on the plasma parameters, and the resulting enhancement of the runaway production rate will be discussed.« less