On self-consistent ray-tracing and Fokker–Planck modeling of the hard x-ray emission during lower-hybrid current drive in tokamaks

Bizarro, João P. S.; Peysson, Y.; Bonoli, P. T.; Carrasco, J.; Wit, T. Dudok de; Fuchs, V.; Hoang, G.T.; Litaudon, X.; Moreau, D.; Pocheau, C.; Shkarofsky, I. P.

doi:10.1063/1.860664

Cited by 29 publications

(38 citation statements)

References 14 publications

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“…V, mainly based on hard x-ray measurements. 20 In this section, simulations of ripple power losses, which are measured during LH current drive, are also presented. The predicted LH power deposition profiles and their respective energy dependences determined from raytracing plus Fokker-Planck calculations, including magnetic ripple perturbation, are used as an input for a kinetic model, 21 which allows us to estimate losses due to fast particles trapped in local magnetic mirrors during LH experiments.…”

Section: Introductionmentioning

confidence: 99%

Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks

et al. 1996

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Using ray tracing, a detailed investigation of the lower-hybrid ͑LH͒ wave propagation in presence of toroidal magnetic field ripple is presented. The local ray behavior is first depicted for a cylindrical equilibrium periodically modulated along the axial direction. Variations along ray trajectories in the component of the wave vector parallel to the equilibrium magnetic field are observed, with a maximum relative amplitude that is locally of the order of the ripple level. For the full rippled toroidal equilibrium, a similar local behavior is found when the ray trajectory crosses a high ripple region. Despite the modest amplitude of the local ray perturbation, its global influence on ray trajectories may be strong, as a consequence of the combined effects of toroidal and poloidal inhomogeneities. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the TORE SUPRA tokamak ͓Equipe TORE SUPRA, in . It is shown that magnetic ripple may induce significant modifications in the LH power deposition profiles, mainly in the ''few passes'' regime when the wave makes some, but not many, passes inside the plasma before being absorbed. The effect of magnetic ripple leads then to a broadening of the power deposition profile and a shift towards the center of the plasma, and a better coupling with high energy electrons. This behavior may be explained by an increase in the overall ray stochasticity. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations.

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Section: Introductionmentioning

confidence: 99%

Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks

et al. 1996

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“…37 In some ways, the approach considered here represents an intermediate modeling level between a crude parametric description of the fast electron distribution function and a full calculation of the quasilinear diffusion coefficient from the wave-field pattern estimated by raytracing, beam-tracing, or full-wave calculations. 38,39 It can give valuable details on the fast electron population and its interaction with rf waves without entering into the high complexity of an explicit modeling of the wave-particle physics. Important trends at the microscopic level can therefore be extracted from experimental data, from which consistent physical interpretations can be outlined beyond the methods based on conventional inversion techniques.…”

Section: A Hxr Emission During Lower Hybrid Current Drive In the Tokmentioning

confidence: 99%

Fast electron bremsstrahlung in axisymmetric magnetic configuration

Peysson

Decker

2008

Physics of Plasmas

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The nonthermal bremsstrahlung is calculated in a plasma with arbitrary axisymmetric magnetic configuration, taking into account the relativistic angular anisotropy of the radiation cross section at high photon energies, the helical winding of the field lines on the magnetic flux surfaces, and the poloidal variation of the electron distribution function including particle trapping effects. The fast electron dynamics during current drive in tokamaks and reverse field pinches can be investigated in detail by coupling this calculation to a bounce-averaged relativistic Fokker–Planck solver, which calculates the electron distribution function. The asymmetry between high- and low-field side hard x-ray emission intensity that has been measured on the Tore-Supra tokamak [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995) Vol. 1, IAEA-CN-60/A1-5 (Institute of Physics, Bristol, U.K., 1995), p. 105] is explained for the first time by the role of trapped electrons. A much stronger poloidal asymmetry is predicted for the line-integrated fast electron bremsstrahlung in the poloidal plane of the Madison Symmetric Torus [R. N. Dexter et al., Fusion Tech. 19, 131 (1991)], since the helical winding of the magnetic field lines is much larger for a reverse field pinch configuration. In this case, the hard x-ray emission is no longer a flux surface quantity, which prevents local reconstructions using a standard Abel inversion, whatever the geometrical arrangement of the lines of sight.

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“…The measurement of the FEB emission in the hard X-ray energy range is the most efficient means for the investigation of LHCD experiments in plasma physics [5]. It allows not only to determine the energy range of fast electrons built up by the LH waves, but also the details of momentum dynamics and the relativistic angular anisotropy in the direction of fast electrons flow, and the propagation, absorption of the LH wave [6,7]. Powerful FEB diagnostics have been developed in many tokamaks like JET [4], PBX-M [8], and Tore Supra [9,10] to assess the LHCD performance.…”

Section: Introductionmentioning

confidence: 99%