Observation of the loss of pre-disruptive runaway electrons in KSTAR ohmic plasma disruptions

Cheon, MunSeong; Kim, Jung-Hee; An, Younghwa; Seo, D. C.

doi:10.1088/0029-5515/56/12/126004

Cited by 6 publications

(13 citation statements)

References 15 publications

(16 reference statements)

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“…Scintillators can also be used to detect photo-neutrons; these can have fairly high time response (< 1µs) but have the disadvantage of measuring both neutrons and HXRs, so baseline subtraction is usually needed to separate photo-neutron from HXR signals [213]. Photo-neutron Cherenkov radiation has also been used to develop a measurement of RE-wall strikes with fast (several µs) time response in KSTAR [214]. Photo-neutron signal is typically used as evidence of the loss of highenergy REs from the plasma, without any energy resolution, although a more detailed study including the measurement of the photo-neutron spectrum with a 3 He counter was done in the PLT tokamak.…”

Section: Mev For 12 C [212]mentioning

confidence: 99%

Physics of runaway electrons in tokamaks

et al. 2019

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Of all electrons, runaway electrons have long been recognized in the fusion community as a distinctive population. They now attract special attention as a part of ITER mission considerations. This review covers basic physics ingredients of the runaway phenomenon and the ongoing efforts (experimental and theoretical) aimed at runaway electron taming in the next generation tokamaks. We emphasize the prevailing physics themes of the last 20 years: the hot-tail mechanism of runaway production, runaway electron interaction with impurity ions, the role of synchrotron radiation in runaway kinetics, runaway electron transport in presence of magnetic fluctuations, micro-instabilities driven by runaway electrons in magnetized plasmas, and vertical stability of the plasma with runaway electrons. The review also discusses implications of the runaway phenomenon for ITER and the current strategy of runaway electron mitigation.

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Section: Mev For 12 C [212]mentioning

confidence: 99%

Physics of runaway electrons in tokamaks

et al. 2019

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“…In this paper we analyze the effects of geometry and the spatial distribution of runaway synchrotron radiation on synchrotron radiation images, which in typical runaway scenarios are experimentally observed in the visible and infra-red spectral ranges. The pioneering measurements of synchrotron radiation from runaway electrons were made already in the 1990's [4,5] and since then such measurements have become a routine diagnostic used in many tokamaks around the world, including TEXTOR [6,7], FTU [8,9], Alcator C-Mod [10], ASDEX Upgrade [11], TCV [11], COMPASS [12] DIII-D [13], EAST [14], and KSTAR [15].…”

Section: Introductionmentioning

confidence: 99%

SOFT: a synthetic synchrotron diagnostic for runaway electrons

et al. 2018

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Improved understanding of the dynamics of runaway electrons can be obtained by measurement and interpretation of their synchrotron radiation emission. Models for synchrotron radiation emitted by relativistic electrons are well established, but the question of how various geometric effects -such as magnetic field inhomogeneity and camera placement -influence the synchrotron measurements and their interpretation remains open. In this paper we address this issue by simulating synchrotron images and spectra using the new synthetic synchrotron diagnostic tool SOFT (Synchrotron-detecting Orbit Following Toolkit). We identify the key parameters influencing the synchrotron radiation spot and present scans in those parameters. Using a runaway electron distribution function obtained by Fokker-Planck simulations for parameters from an Alcator C-Mod discharge, we demonstrate that the corresponding synchrotron image is well-reproduced by SOFT simulations, and we explain how it can be understood in terms of the parameter scans. Geometric effects are shown to significantly influence the synchrotron spectrum, and we show that inherent inconsistencies in a simple emission model (i.e. not modeling detection) can lead to incorrect interpretation of the images.

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“…Synchrotron radiation from runaway electrons was first studied on the TEXTOR tokamak [9] and has since been applied to many other tokamaks to study the runaway electron distribution function [10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Basic interpretation of the synchrotron radiation data obtained in experiments has been done ever since the first synchrotron radiation measurements, but in 1996 the first deeper analysis of the synchrotron radiation spot shape seen in camera images was carried out by Pankratov [24], and later in 1999 the effects of the toroidal geometry on the synchrotron radiation spectrum were also considered [25].…”

Section: Introductionmentioning

confidence: 99%

Interpretation of runaway electron synchrotron and bremsstrahlung images

Hoppe¹,

Embréus²,

Paz-Soldan³

et al. 2018

Nucl. Fusion

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The crescent spot shape observed in DIII-D runaway electron synchrotron radiation images is shown to result from the high degree of anisotropy in the emitted radiation, the finite spectral range of the camera and the distribution of runaways. The finite spectral camera range is found to be particularly important, as the radiation from the high-field side can be stronger by a factor 10 6 than the radiation from the lowfield side in DIII-D. By combining a kinetic model of the runaway dynamics with a synthetic synchrotron diagnostic we see that physical processes not described by the kinetic model (such as radial transport) are likely to be limiting the energy of the runaways. We show that a population of runaways with lower dominant energies and larger pitch-angles than those predicted by the kinetic model provide a better match to the synchrotron measurements. Using a new synthetic bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager (GRI) diagnostic used at DIII-D to resolve the spatial distribution of runaway-generated bremsstrahlung.

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Observation of the loss of pre-disruptive runaway electrons in KSTAR ohmic plasma disruptions

Cited by 6 publications

References 15 publications

Physics of runaway electrons in tokamaks

Physics of runaway electrons in tokamaks

SOFT: a synthetic synchrotron diagnostic for runaway electrons

Interpretation of runaway electron synchrotron and bremsstrahlung images

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