Stochastic broadening of the separatrix of a tokamak divertor

Punjabi, Alkesh; Verma, Arun Kumar; Boozer, Allen H.

doi:10.1103/physrevlett.69.3322

Cited by 84 publications

(66 citation statements)

References 4 publications

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“…This hypersurface is known in the dynamics literature as the stochastic separatrix, and for example is useful in defining confinement bottles in plasma tokomacs. 5 This hypersurface is a level surface of reaction probability, and so the reaction coordinate is logically defined as being orthogonal to it. This definition has resulted in one algorithm for identification of the reaction coordinate; one guesses at a reaction coordinate, holds these degrees of freedom fixed, and performs constrained molecular dynamics.…”

Section: The Stochastic Separatrix and The Transition State Ensemblementioning

confidence: 99%

The stochastic separatrix and the reaction coordinate for complex systems

Antoniou

Schwartz

2009

The Journal of Chemical Physics

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We present a new approach to the identification of degrees of freedom which comprise a reaction coordinate in a complex system. The method begins with the generation of an ensemble of reactive trajectories. Each trajectory is analyzed for its equicommittor position or transition state; then the transition state ensemble is identified as the stochastic separatrix. Numerical analysis of the points along the separatrix for variability of coordinate location correctly identifies the components of the reaction coordinate in a test system of a double well coupled to a promoting vibration and a bath of linearly coupled oscillators.

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Section: The Stochastic Separatrix and The Transition State Ensemblementioning

confidence: 99%

The stochastic separatrix and the reaction coordinate for complex systems

Antoniou

Schwartz

2009

The Journal of Chemical Physics

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“…We assume this energy loss channel is created by a change of the magnetic edge topology due to the ELM [26][27][28][29] , connecting the edge plasma with the divertor. A similar topology is observed when external or internal magnetic perturbations are present, e.g.…”

Section: Rotation Of Post-elm Filamentsmentioning

confidence: 99%

Application of AXUV diode detectors at ASDEX Upgrade

Bernert

Eich

Burckhart

et al. 2014

Review of Scientific Instruments

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In the ASDEX Upgrade tokamak a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight (LOS) and a time resolution of 5 µs was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. (IRD). The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV to 8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes (ELMs) is analyzed on fast timescales.

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“…That slab geometries, despite their popularity, are not suited for describing fluxes as plasma current density in slab magnetic islands grows with their width, in contradiction with the actual behaviour where stochasticity is precisely enhanced by cooling [16]. Even the, perhaps, most consistent archetypal tokamak map, the one parameter single null divertor map [17] remains disconnected from most of the physical significance of its variables and parameters. It is even affirmed that this map cannot address a particular device [18].…”

Section: Introductionmentioning

confidence: 91%

Mapping the intrinsic stochasticity of tokamak divertor configuration

Barocio¹,

Chávez-Alarcón²,

Gutiérrez-Tapia³

2006

Braz. J. Phys.

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Poloidal divertors are, more than ever before, a crucial topic for the advancement of magnetic fusion technology. Due to the often non linear and stochastic nature of the plasma edge phenomena, canonical mapping has provided a powerful method at modelling their characteristics, albeit many authors rely on heuristically adapted schemes. Thus, it is reported here a specific and physically consistent map model of the tokamak single null magnetic configuration, assuming plasma-field equilibrium, based on the construction of a fundamental Hamiltonian form. Then, the magnetohydrodynamically non ideal perturbations are introduced through the Rayleigh function of the system. As an illustration, the resulting compact canonical map is applied to the analysis of some of the most relevant features of the edge magnetic topology.

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Stochastic broadening of the separatrix of a tokamak divertor

Cited by 84 publications

References 4 publications

The stochastic separatrix and the reaction coordinate for complex systems

The stochastic separatrix and the reaction coordinate for complex systems

Application of AXUV diode detectors at ASDEX Upgrade

Mapping the intrinsic stochasticity of tokamak divertor configuration

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