A synchrotron radiation diagnostic to observe relativistic runaway electrons in a tokamak plasma

Jaspers, R.; Cardozo, N.J. Lopes; Donné, A. J. H.; Widdershoven, H. L. M.; Finken, K. H.

doi:10.1063/1.1318245

Cited by 68 publications

(106 citation statements)

References 11 publications

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“…The view covers central part of the plasma with approximate dimensions of 30 × 30 cm. The registered spectral range is λ = 3 -5 µm, which makes this diagnostics sensitive to runaway electrons with energies above 20 MeV [40,41]. The system can record full images at a frequency of up to 394 Hz and reduced images at a frequency of up to 13 kHz.…”

Section: Description Of the Experimentsmentioning

confidence: 99%

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

Bozhenkov¹,

Lehnen²,

Finken³

et al. 2008

Plasma Phys. Control. Fusion

123

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Abstract. Runaway electrons represent a serious problem for the reliable operation of the future experimental tokamak ITER. Due to the multiplication factor of exp(50) in the avalanche even a few seed runaway electrons will result in a beam of high energetic electrons that is able to damage the machine. Thus suppression of runaway electrons is a task of high importance, for which reason we present here a systematic study of runaway electrons following massive gas injection in TEXTOR. Argon injection can cause generation of runaways carrying up to 30% of the initial plasma current, while disruptions triggered by injection of helium or of mixtures of argon (5, 10, 20%) with deuterium are runaway free. Disruptions caused by argon injection finally become runaway free for very large amounts of injected atoms. The appearance/absence of runaway electrons is related to the fraction of atoms delivered to the plasma center. This so called mixing efficiency is deduced from a 0D model of the current quench. The estimated mixing efficiency is: 3% for argon, 15% for an argon/deuterium mixture and about 40% for helium. A low mixing efficiency of high-Z impurities can have a strong implication for the design of the disruption mitigation system for ITER. However, a quantitative prediction requires a better understanding of the mixing mechanism.

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Section: Description Of the Experimentsmentioning

confidence: 99%

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

Bozhenkov¹,

Lehnen²,

Finken³

et al. 2008

Plasma Phys. Control. Fusion

123

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show abstract

“…Recent researches indicate that tokamak, a magnetic confinement fusion energy device, may be the largest artificial positron factory in the world [4,5]. In large tokamaks like JET and JT-60U, above 10 14 positrons are generated in a post-disruption plasma by runaway electrons [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The dynamics of these positrons after birth in tokamaks is a noteworthy question that may yield valuable information about the runaway dynamics and disruption process in tokamaks.…”

mentioning

confidence: 99%

What is the fate of runaway positrons in tokamaks?

et al. 2014

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Massive runaway positrons are generated by runaway electrons in tokamaks. The fate of these positrons encodes valuable information about the runaway dynamics. The phase space dynamics of a runaway position is investigated using a Lagrangian that incorporates the tokamak geometry, loop voltage, radiation and collisional effects. It is found numerically that runaway positrons will drift out of the plasma to annihilate on the first wall, with an in-plasma annihilation possibility less than 0.1%. The dynamics of runaway positrons provides signatures that can be observed as diagnostic tools.

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“…The X-rays produced by REs which strike PFCs, 5,11-13 neutrons which result from photonuclear reactions, 11,14 the electron cyclotron emission 15,16 and the synchrotron radiation [17][18][19] of the REs can be measured. Additionally, specialized probes are used to detect the REs at the plasma edge.…”

mentioning

confidence: 99%

Measurements of the runaway electron energy during disruptions in the tokamak TEXTOR

et al. 2012

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Calorimetric measurements of the total runaway electron energy are carried out using a reciprocating probe during induced TEXTOR disruptions. A comparison with the energy inferred from runaway energy spectra, which are measured with a scintillator probe, is used as an independent check of the results. A typical runaway current of 100 kA at TEXTOR contains 30 to 35 kJ of runaway energy. The dependencies of the runaway energy on the runaway current, the radial probe position, the toroidal magnetic field and the predisruptive plasma current are studied. The conversion efficiency of the magnetic plasma energy into runaway energy is calculated to be up to 26%. V C 2012 American Institute of Physics. [http://dx

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A synchrotron radiation diagnostic to observe relativistic runaway electrons in a tokamak plasma

Cited by 68 publications

References 11 publications

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

What is the fate of runaway positrons in tokamaks?

Measurements of the runaway electron energy during disruptions in the tokamak TEXTOR

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