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Title: Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks

Authors:
 [1];  [1];  [2]
  1. Universidad Carlos III, Madrid, Spain
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
931764
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 7
Country of Publication:
United States
Language:
English
Subject:
runaway electrons; radiation losses; disruptions; tokamaks

Citation Formats

Fernandez-Gomez, Isabel, Martin-Solis, Jose Ramon, and Sanchez, Raul. Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks. United States: N. p., 2007. Web. doi:10.1063/1.2746219.
Fernandez-Gomez, Isabel, Martin-Solis, Jose Ramon, & Sanchez, Raul. Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks. United States. doi:10.1063/1.2746219.
Fernandez-Gomez, Isabel, Martin-Solis, Jose Ramon, and Sanchez, Raul. Mon . "Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks". United States. doi:10.1063/1.2746219.
@article{osti_931764,
title = {Determination of the parametric region in which runaway electron energy losses are dominated by bremsstrahlung radiation in tokamaks},
author = {Fernandez-Gomez, Isabel and Martin-Solis, Jose Ramon and Sanchez, Raul},
abstractNote = {},
doi = {10.1063/1.2746219},
journal = {Physics of Plasmas},
number = 7,
volume = 14,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • It has been recently argued that, at sufficiently large parallel electric fields, bremsstrahlung radiation can greatly reduce the maximum energy that runaway electrons can gain in tokamaks [M. Bakhtiari et al., Phys. Plasmas 12, 102503 (2005)]. In this contribution, the work of these authors is extended to show that the region where bremsstrahlung radiation dominate runaway energy losses is however more restricted than reported by them. Expressions will be provided for the limits of this region within the parameter space spanned by the background density and parallel electric field, as a function of the rest of the plasma parameters. Itmore » will be shown that the background density has to be above a certain critical value and that the parallel electric field must lie within a range of values, below and above which synchrotron radiation dominate the runaway energy losses. Finally, it will be demonstrated that typical disruption parameters lie within this region and, as a result, bremsstrahlung losses still play an important role in controlling the runaway energy.« less
  • Bremsstrahlung radiation of runaway electrons is found to be an energy limit for runaway electrons in tokamaks. The minimum and maximum energy of runaway electron beams is shown to be limited by collisions and bremsstrahlung radiation, respectively. It is also found that a massive injection of a high-Z gas such as xenon can terminate a disruption-generated runaway current before the runaway electrons hit the walls.
  • No abstract prepared.
  • The dynamics of runaway electrons in tokamak plasmas is studied in momentum space. In this analysis the electrons are accelerated by an electric field while they are decelerated by collisional drag, synchrotron radiation, and bremsstrahlung radiation. It is shown that the inclusion of bremsstrahlung losses into the calculations is important for the interpretation of disruption-mitigation experiments where large amounts of high Z are injected into the plasma. The inclusion of bremsstrahlung reduces the maximum energy that the runaway electrons can gain from the electric field.
  • The synchrotron radiation emitted by runaway electrons in a fusion plasma provides information regarding the particle momenta and pitch-angles of the runaway electron population through the strong dependence of the synchrotron spectrum on these parameters. Information about the runaway density and its spatial distribution, as well as the time evolution of the above quantities, can also be deduced. In this paper, we present the synchrotron radiation spectra for typical avalanching runaway electron distributions. Spectra obtained for a distribution of electrons are compared with the emission of mono-energetic electrons with a prescribed pitch-angle. We also examine the effects of magnetic fieldmore » curvature and analyse the sensitivity of the resulting spectrum to perturbations to the runaway distribution. The implications for the deduced runaway electron parameters are discussed. We compare our calculations to experimental data from DIII-D and estimate the maximum observed runaway energy.« less