Role of divertor geometry on detachment and core plasma performance in JT60U

Asakura, N.; Hosogane, N.; Itami, K.; Sakasai, A.; Sakurai, S.; Shimizu, K.; Shimada, M.; Kubo, H.; Higashijma, S.; Takenaga, H.; Tamai, Hiroshi; Konoshima, S.; Sugie, Toshiharu; Masaki, K.; Koide, Y.; Naito, O.; Shirai, Hiroshi; Takizuka, T.; Ishijima, Tatsuo; Suzuki, Shingo; Kumagai, A.

doi:10.1016/s0022-3115(98)00818-6

Cited by 72 publications

(54 citation statements)

References 12 publications

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“…Experiments in different divertor configurations have confirmed these general trends and were also shown to be consistent with code predictions [5,6,8,9,10,11,13]. Theretbre, though a detailed numerical analysis is required in any particular case, these aspects can be considered as in principle well understood.…”

Section: Impact On Neutralssupporting

confidence: 54%

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Geometry effects in the SOL and divertor

Borraß

1998

Czech J Phys

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Geometry effects in the SOL and divertor, which are the main focus of a variety of present tokamaks, are reviewed. Since divertor detachment constitutes a central element in this context, some basic results on divertor detachment are also summarised. The discussion of issues that played a role in recent experimental campaigns and their theoretical and numerical analysis form a major part of the paper. Emphasis is placed on gas target related effects. An attempt is made to reduce the impact of geometry to a small number of basic mechanisms. 1 Introduction Studies of divertor and SOL related geometry effects have a long history in fusion research and include topics such as: o The impact of different divertor concepts (Single null versus double null, poloidal versus toroidal divertors) o The impact of plasma shape (elongation, triangularity, flux geometry in the divertor) o The impact of divertor geometry -Impact of divertor chamber shape (Divertor closure, open versus slot or box divertor) -Impact of plate geometry (Plate inclination)While the comparison of different divertor concepts has played an important role during the previous generation of divertor tokamaks (ASDEX, DITE, JFT-2M, etc.) the single null poloidal divertor has now become the prevailing option. The impact of plasma shape is normally covered by the question of how SOL related phenomena (e.g., density limits) depend on shaping parameters. Currently, the main interest is in impact of divertor geometry and this will be the main topic of this paper. This development is intimately related to the discovery and understanding of divertor detachment during the past years. While in attached, low temperature regimes the plasma experiences the surrounding walls merely through the target, neutrals provide an intensive interaction between divertor plasma and even remote parts of the wall, when detachment occurs. This provides a variety of subtle ways how divertor geometry may come into play and makes divertor detachment an essential ingredient of the topic under discussion. We will therefore summarise some elements of detachment physics, relevant in this context, in a separate section.Effects of divertor geometry are naturally discussed with a view to their impact on the basic performance requirements a divertor has to meet in a next generation device such as 1TER, namely [1]:(i) Neutral retainment to keep neutrals away from the main chamber to avoid main chamber

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Section: Impact On Neutralssupporting

confidence: 54%

“…This has triggered extensive divertor programmes, particularly on JET [5,6], ASDEX Upgrade [7,8], JT60U [9], ALCATOR C-Mod [10,11] and TdeV [12,13], which were devoted to the study of geometrical effects in particular. During the design and operation of these various divertor options modelling played an important role.…”

Section: Introductionmentioning

confidence: 99%

Geometry effects in the SOL and divertor

Borraß

1998

Czech J Phys

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“…Despite the large increase in radial transport associated with the ELM event, the poloidal footprint of the ELM power flux at the outer divertor does not show a significant broadening when compared to the inter-ELM power flux profile at the divertor [179,2,31,180]. A histogram summarising the results of a statistical analysis of the ELM power width (characterised by the full width at half maximum) at the outer divertor during the ELM is shown in Fig.…”

Section: Spatial Characteristics Of the Divertor Target Heat Flux Promentioning

confidence: 99%

“…Divertor closure is influenced by the divertor plasma parameters through their effects on the ionisation mean free paths but also by the conductance of neutrals through and past the divertor structure to the main plasma chamber [69]. Experiments in many divertor tokamaks have shown that increasing the divertor closure has led to larger divertor neutral pressures [211,212,179,62,213], as shown in Fig In general, the predictions with respect to the behaviour of deuterium neutral and recycling impurity exhaust by edge modelling codes have been confirmed by the experiments in tokamaks. In particular, the dependences of the neutral particle and impurity exhaust on the details of the divertor geometry and on the local magnetic flux surfaces have been confirmed [214,69,215,65,216,217].…”

Section: Neutral Pressure Controlmentioning

confidence: 99%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

282

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Abstract.Progress, since the ITER Physics Basis publication, in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are : energy transport in the SOL in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low and high Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas : refinement of the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a 2 major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral-neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma-materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed. Introduction.This chapter outlines the significant progress achieved since the ITER Physics Basis in understanding basic scrape-off layer (SOL) and divertor processes in a tokamak. The interaction of plasma with first-wall surfaces will have considerable impact on the performance of fusion plasmas, the lifetime of plasma facing components, and the retention of tritium in next step Burning Plasma E...

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“…The flat density profile in the outer SOL region has been observed, which is often referred to the second SOL. Such an extended density of plasmas in the second SOL attributes to increase of impurities and recycling rate on the first wall [32], therefore, the mechanism of density profile formation in the second SOL should be explored.…”

Section: Edge/sol Turbulence and Blob Transportmentioning

confidence: 99%

Disparate Scale Nonlinear Interactions in Edge Turbulence

Yagi

Itoh

et al. 2008

Contrib. Plasma Phys.

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In this topical review, we explain the recent achievement in the study of nonlinear interactions, putting an emphasis on the relevance to edge turbulence. First, we start from the survey of the essence in the nonlinear theory of drift wave -zonal flows systems, and visit the experimental observations of the nonlinear interactions of tokamak edge turbulence. Secondly, the universality of intermittent convective transport in the SOL of different magnetic devices are shown. Then, we discuss evolution of collisional drift wave instability in the linear plasma configuration, which is bounded by end plates having analogy to SOL plasmas. By introducing the Numerical Linear Device, the intermittent evolution of large-amplitude instabilities, generation mechanism of the poloidal flow and other nonlinear process are examined.

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Role of divertor geometry on detachment and core plasma performance in JT60U

Cited by 72 publications

References 12 publications

Geometry effects in the SOL and divertor

Geometry effects in the SOL and divertor

Chapter 4: Power and particle control

Disparate Scale Nonlinear Interactions in Edge Turbulence

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