Generation of suprathermal electrons during sawtooth crashes in a tokamak plasma

Klimanov, I.; Fasoli, A.; Goodman, T.; Team, the TCV

doi:10.1088/0741-3335/49/3/l01

Cited by 24 publications

(22 citation statements)

References 10 publications

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“…This may be explained by the relativistic beaming of the synchrotron or bremsstrahlung emitted by the electrons -that could provide direct evidence for the propagation direction -not yet being strong at these subrelativistic energies. Nevertheless, the energetic electrons are radially localized in the vicinity of the inversion radius, as seen for instance from elevated electron cyclotron emission from this region in Klimanov et al (2007); this is consistent with the picture of the energetic electrons being generated in the skin layer. In order to guide experimental observations, further high-fidelity numerical analysis will be necessary to explore the parameter regions where significant reverse runaway electron beams are to be expected to develop.…”

Section: Intact Core and The Role Of Heat Transportsupporting

confidence: 82%

Runaway dynamics in tokamak disruptions with current relaxation

2022

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The safe operation of tokamak reactors requires a reliable modelling capability of disruptions, and in particular the spatio-temporal dynamics of associated runaway electron currents. In a disruption, instabilities can break up magnetic surfaces into chaotic field line regions, causing current profile relaxation, as well as a rapid radial transport of heat and particles. Using a mean-field helicity transport model implemented in the disruption runaway modelling framework Dream, we calculate the dynamics of runaway electrons in the presence of current relaxation events. In scenarios where flux surfaces remain intact in parts of the plasma, a skin current is induced at the boundary of the intact magnetic field region. This skin current region becomes an important centre concerning the subsequent dynamics: it may turn into a hot ohmic current channel, or a sizeable radially localized runaway beam, depending on the heat transport. If the intact region is in the plasma edge, runaway generation in the countercurrent direction can occur, which may develop into a sizeable reverse runaway beam. Even when the current relaxation extends to the entire plasma, the final runaway current density profile can be significantly affected, as the induced electric field is reduced in the core and increased in the edge, thereby shifting the centre of runaway generation towards the edge.

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Section: Intact Core and The Role Of Heat Transportsupporting

confidence: 82%

Runaway dynamics in tokamak disruptions with current relaxation

2022

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“…8 In these experiments, an additional aluminum foil of thickness 308 m filtered the contribution of low-energy photons and the detector was filled with a krypton-methane gas mixture ͓the spectral response is shown in Fig. 2͑d͔͒.…”

Section: Resultsmentioning

confidence: 99%

High-resolution multiwire proportional soft x-ray diagnostic measurements on TCV

Sushkov

Андреев

Camenen

et al. 2008

Review of Scientific Instruments

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A multiwire proportional x-ray (MPX) detector is used on the TCV tokamak (Tokamak à configuration variable) as a high spatial and temporal resolution soft x-ray emissivity imaging diagnostic. The MPX system consists of 64 vertically viewing channels and has been designed to complement the existing TCV soft x-ray tomography system by enhancing the spatial resolution. The MPX detector is suitable for the measurement of fast and localized phenomena and can be used, for instance, for the observation of magnetohydrodynamic activity, for the characterization of transport barriers or for an improved determination of the electron cyclotron heating power deposition profile. The MPX detector operates in continuous-current mode and measures the plasma soft x-ray emission in the 3-30 keV range with a radial resolution of about 5 mm-1% of plasma diameter--and a frequency bandwidth of 50 kHz. A detailed description of the MPX detector construction and the principle of its operation are given. The properties of the detector in photon-counting and continuous-current operation modes are studied. The implementation of the system on TCV and experimental results illustrating the potential of the diagnostic are also presented.

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“…models has been applied to the study of MHDmediated suprathermal electron acceleration in conjunction with sawtooth crashes in a tokamak. 84 The oblique LFS detection geometry has also been exploited in the past decade in a handful of experiments. [85][86][87][88][89] The nature of the relativistic resonance condition is such that for a given frequency and k ʈ there is a maximum major radius from which radiation can be emitted in a toroidal device ͑corresponding to the maximum value of / ce seen near the right-hand boundary of Fig.…”

Section: F501-5mentioning

confidence: 99%

Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

Coda

2008

Review of Scientific Instruments

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Plasmas, both in the laboratory and in space, are often not in thermodynamic equilibrium, and the plasma electron distribution function is accordingly non-Maxwellian. Suprathermal electron tails can be generated by external drives, such as rf waves and electric fields, or internal ones, such as instabilities and magnetic reconnection. The variety and importance of the phenomena in which suprathermal electrons play a significant role explains an enduring interest in diagnostic techniques to investigate their properties and dynamics. X-ray bremsstrahlung emission has been studied in hot magnetized plasmas for well over two decades, flanked progressively by electron-cyclotron emission in geometries favoring the high-energy end of the distribution function ͑high-field-side, vertical, oblique emission͒, by electron-cyclotron absorption, by spectroscopic techniques, and at lower temperatures, by Langmuir probes and electrostatic analyzers. Continuous progress in detector technology and in measurement and analysis techniques, increasingly sophisticated layouts ͑multichannel and tomographic systems, imaging geometries͒, and highly controlled suprathermal generation methods ͑e.g., perturbative rf modulation͒ have all been brought to bear in recent years on an increasingly detailed, although far from complete, understanding of suprathermal electron dynamics.

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Generation of suprathermal electrons during sawtooth crashes in a tokamak plasma

Cited by 24 publications

References 10 publications

Runaway dynamics in tokamak disruptions with current relaxation

Runaway dynamics in tokamak disruptions with current relaxation

High-resolution multiwire proportional soft x-ray diagnostic measurements on TCV

Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

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