Width of the Stochastic Layer

Confinement improvement during detached phase with RMP application in deuterium plasmas of LHD

Nuclear Fusion ◽

10.1088/1741-4326/ac42f3 ◽

2021 ◽

Author(s):

Masahiro Kobayashi ◽

Ryosuke Seki ◽

Yuki Hayashi ◽

Tetsutarou Oishi ◽

Kanji Tanaka ◽

...

Keyword(s):

Heat Load ◽

Field Application ◽

Edge Plasma ◽

Magnetic Fluctuations ◽

Transport Barrier ◽

Radiation Level ◽

Hydrogen Plasmas ◽

Core Plasma ◽

Load Increase ◽

Stochastic Layer

Abstract In order to explore compatibility of good core plasma performance with divertor heat load mitigation, interaction between cold edge plasma and core plasma transport including edge transport barrier (ETB) has been analysed in the divertor detachment discharges of deuterium plasmas in LHD with RMP (resonant magnetic perturbation) field application. The RMP application introduces widened edge stochastic layer and sharp boundary in the magnetic field structure between the confinement region and the edge stochastic layer. The widened edge stochastic layer enhances impurity radiation and provides stable detachment operation as compared with the case without RMP. It is found that ETB is formed at the confinement boundary at the onset of detachment transition. However, as the detachment deepens resistive pressure gradient driven MHD mode is excited, which degrade the ETB. At the same time, however, the core transport decreases to keep global plasma stored energy (Wp) unchanged, showing clearly core-edge coupling. After gradual increase of density fluctuation during the MHD activity, spontaneous increase of Wp and recovery of ETB are observed while the detachment is maintained. Then the coherent MHD mode ceases and ELM like bursts appear. In the improved mode, the impurity decontamination occurs, and the divertor heat load increase slightly. Key controlling physics in the interplay between core and cold edge plasma is discussed. Comparison between deuterium and hydrogen plasmas show that the hydrogen plasmas exhibit similar features as the deuterium ones in terms of density and magnetic fluctuations, impurity decontamination toward higher confinement etc. But most of the features are modest in the hydrogen plasmas and thus no clear confinement mode transition with clear ETB formation is defined. Better global confinement is obtained in the deuterium plasmas than the hydrogen ones at higher radiation level.

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Motion in a stochastic layer described by symbolic dynamics

Chaos An Interdisciplinary Journal of Nonlinear Science ◽

10.1063/1.166303 ◽

1998 ◽

Vol 8 (1) ◽

pp. 248-256 ◽

Cited By ~ 13

Author(s):

J. H. Misguich ◽

J.-D. Reuss ◽

Y. Elskens ◽

R. Balescu

Keyword(s):

Symbolic Dynamics ◽

Stochastic Layer

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Rescaling invariance and anomalous transport in a stochastic layer

Physical Review E ◽

10.1103/physreve.60.r6287 ◽

1999 ◽

Vol 60 (6) ◽

pp. R6287-R6290 ◽

Cited By ~ 13

Author(s):

S. S. Abdullaev ◽

K. H. Spatschek

Keyword(s):

Anomalous Transport ◽

Stochastic Layer

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Effects of varying stochastic layer on edge plasma and impurity transport in 3D EMC3-EIRENE simulations of LHD

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2017.04.088 ◽

2017 ◽

Vol 125 ◽

pp. 625-630 ◽

Cited By ~ 1

Author(s):

Shuyu Dai ◽

M. Kobayashi ◽

G. Kawamura ◽

Q. Shi ◽

Y. Feng ◽

...

Keyword(s):

Edge Plasma ◽

Impurity Transport ◽

Stochastic Layer

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Stochastic layer in nonlinear NMR

Radiophysics and Quantum Electronics ◽

10.1007/bf01034404 ◽

1987 ◽

Vol 30 (6) ◽

pp. 558-562 ◽

Cited By ~ 1

Author(s):

A. I. Ugulava

Keyword(s):

Stochastic Layer

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The simple map for a single-null divertor tokamak

Journal of Plasma Physics ◽

10.1017/s0022377800019474 ◽

1996 ◽

Vol 56 (3) ◽

pp. 569-603 ◽

Cited By ~ 18

Author(s):

Alkes Punjabi ◽

Arun Verma ◽

Allen Boozer

Keyword(s):

Safety Factor ◽

Single Degree Of Freedom ◽

Divertor Plate ◽

Divertor Tokamak ◽

Magnetic Perturbations ◽

Stochastic Layer ◽

Field Lines ◽

Basic Features ◽

Area Preserving

We present the simple map for a single-null divertor tokamak. The simple map is an area-preserving map based on the idea that magnetic field lines are a single-degree- of-freedom time-dependent Hamiltonian system, and that the basic features of such systems near the X-point are generic. We obtain the properties of this map and the resulting footprints of field lines on the divertor plate. These include the width of the stochastic layer, the edge safety factor, the area of the footprint and the amount of magnetic flux diverted. We give the safety factor profile, the average and median values of strike angles, lengths and the Liapunov exponents. We describe how the effects of magnetic perturbations can be included in the simple map. We show how the map can be applied to the problem of the determination of heat flux on the divertor plate in tokamaks.

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