[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

FIRST EXPERIMENTS IN JET. Results obtained from JET since June 1983 are described which show that this large tokamak behaves in a similar manner to smaller tokamaks, but with correspondingly improved plasma parameters. Long-duration hydrogen and deuterium plasmas (>10 s) have been obtained with electron temperatures reaching > 4 keV for power dissipations < 3 MW and with * Euratom-IPP Association, Institut fur Plasmaphysik, Garching, Federal Republic of Germany. ** Euratom-ENEA Association, Centro di Frascati, Italy. *** Euratom-UKAEA Association, Culham Laboratory, Abingdon, Oxfordshire, United Kingdom. **** University of Dusseldorf, Dusseldorf, Federal Republic of Germany. + Euratom-Ris0 Association, Ris<f> National Laboratory, Roskilde, Denmark. ++ Euratom-CNR Association, Istituto di Física del Plasma, Milan, Italy. +++ Imperial College of Science and Technology, University of London, London, United Kingdom. ++++ Euratom-FOM Association, FOM Instituut voor Plasmafysica,. Nieuwegein, Netherlands. ® Euratom-Suisse Association, Centre de Recherches en Physique des Plasmas, Lausanne, Switzerland.

Plasma Physics and Controlled Nuclear Fusion Research

to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

A comprehensive review of zonal flow phenomena in plasmas is presented. While the emphasis is on zonal flows in laboratory plasmas, planetary zonal flows are discussed as well. The review presents the status of theory, numerical simulation and experiments relevant to zonal flows. The emphasis is on developing an integrated understanding of the dynamics of drift wave–zonal flow turbulence by combining detailed studies of the generation of zonal flows by drift waves, the back-interaction of zonal flows on the drift waves, and the various feedback loops by which the system regulates and organizes itself. The implications of zonal flow phenomena for confinement in, and the phenomena of fusion devices are discussed. Special attention is given to the comparison of experiment with theory and to identifying directions for progress in future research.

/pdf/zonal-flows-in-plasma-a-review-3byloag115.pdf

Zonal flows in plasma—a review

Astrophysical magnetic fields and nonlinear dynamo theory

This conference report summarizes the contributions to, and discussions at, the 1st Asia-Pacific Transport Working Group Meeting held in Toki, Japan, on 14–17 June 2011. The topics of the meeting were organized under four main headings: momentum transport, non-locality in transport, edge turbulence and L–H transition and 3D effects on transport physics. The events which initiated this meeting are also described in this report.

https://iopscience.iop.org/article/10.1088/0029-5515/52/2/027001/pdf

1st Asia-Pacific Transport Working Group (APTWG) Meeting

Bounds on edge shear layer persistence while approaching the density limit

A mean field Ohm’s law valid for collisionless plasmas is derived kinetically. It is shown that contrary to conventional thinking, the resulting hyperresistivity is significantly smaller than its fluid counterpart due to the fact that the turbulent decorrelation rate is linked to the rapid electron ballistic motion rather than the slower nonlinear mixing time. Moreover, the off‐diagonal contributions to the parallel electron momentum flux are shown to result in Ohm’s law renormalizations that dwarf the current diffusivity and break radial parity symmetry.

/pdf/a-mean-field-ohm-s-law-for-collisionless-plasmas-1dyyxrzeyf.pdf

A mean field Ohm's law for collisionless plasmas

We present a theory of turbulent elasticity, a property of drift-wave--zonal-flow (DW-ZF) turbulence, which follows from the time delay in the response of DWs to ZF shears. An emergent dimensionless parameter ${|\ensuremath{\langle}v\ensuremath{\rangle}}^{\ensuremath{'}}|/\ensuremath{\Delta}{\ensuremath{\omega}}_{k}$ is found to be a measure of the degree of Fickian flux-gradient relation breaking, where ${|\ensuremath{\langle}v\ensuremath{\rangle}}^{\ensuremath{'}}|$ is the ZF shearing rate and $\ensuremath{\Delta}{\ensuremath{\omega}}_{k}$ is the turbulence decorrelation rate. For ${|\ensuremath{\langle}v\ensuremath{\rangle}}^{\ensuremath{'}}|/\ensuremath{\Delta}{\ensuremath{\omega}}_{k}g1$, we show that the ZF evolution equation is converted from a diffusion equation, usually assumed, to a telegraph equation, i.e., the turbulent momentum transport changes from a diffusive process to wavelike propagation. This scenario corresponds to a state very close to the marginal instability of the DW-ZF system, e.g., the Dimits shift regime. The frequency of the ZF wave is ${\ensuremath{\Omega}}_{\mathrm{ZF}}=\ifmmode\pm\else\textpm\fi{}{\ensuremath{\gamma}}_{d}^{1/2}{\ensuremath{\gamma}}_{\mathrm{modu}}^{1/2}$, where ${\ensuremath{\gamma}}_{d}$ is the ZF friction coefficient and ${\ensuremath{\gamma}}_{\mathrm{modu}}$ is the net ZF growth rate for the case of the Fickian flux-gradient relation. This insight provides a natural framework for understanding temporally periodic ZF structures in the Dimits shift regime and in the transition from low confined mode to high confined mode in confined plasmas.

/pdf/elasticity-in-drift-wave-zonal-flow-turbulence-24rp57skom.pdf

Elasticity in drift-wave-zonal-flow turbulence.

Several new results in the physics of edge poloidal flows, turbulent stresses and momentum transport are reported. These are based on experiments on the HL-2A tokamak. Significant deviation from neoclassical prediction for mean poloidal flow in Ohmic and L mode discharges is deduced from direct measurements of the turbulent Reynolds stress. The deviation increases with heating power. The turbulent poloidal viscosity is synthesized from fluctuation data, and is found to be comparable to the turbulent particle diffusivity. The intrinsic poloidal torque is deduced from synthesis, for the first time. PDFs of particle flux and Reynolds stress are obtained. Both exhibit fat tails and large kurtosis, suggesting that the momentum transport process represented by the Reynolds stress is not well described by quasilinear calculations.

Patrick Diamond

Papers

1st Asia-Pacific Transport Working Group (APTWG) Meeting

Bounds on edge shear layer persistence while approaching the density limit

A mean field Ohm's law for collisionless plasmas

Elasticity in drift-wave-zonal-flow turbulence.

Studies of Reynolds Stress and the Turbulent Generation of Edge Poloidal Flows on the HL-@A Tokamak