A possibility of wall-protecting cold-plasma layer formation in a tokamak reactor

Igitkhanov, Yu.; Kukushkin, A.S.; Stakhanov, I. P.

doi:10.1088/0029-5515/18/3/009

Cited by 6 publications

(4 citation statements)

References 2 publications

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“…A cold gas target high-density divertor concept (that later evolved into the radiatively detached divertor) was known from the 1970s [39]. It was first implemented and developed in the 1980s [40][41][42][43][44][45][46]. Significant research progress was made in the 1990s: the radiative detachment was studied in large tokamaks with high input power, density control via cryopumping, and large divertor radiated power fractions relevant to reactor-like conditions [7,8,19,23].…”

Section: Concepts Overview Via Historical Perspectivementioning

confidence: 99%

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

Soukhanovskii

2017

Plasma Phys. Control. Fusion

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The present vision for a plasma-material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertor configurations are divided into four categories based on their salient qualitative features: (1) multiple standard X-point divertors; (2) divertors with higher order nulls; (3) divertors with multiple X-points; and (4) long poloidal leg divertors (and also with multiple X-points). This paper reviews experiments and modeling in the area of radiative detachment in the advanced magnetic divertor configurations.

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Section: Concepts Overview Via Historical Perspectivementioning

confidence: 99%

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

Soukhanovskii

2017

Plasma Phys. Control. Fusion

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“…They are solved as function of electron temperature T e at given input parameters or functions 7 ( T e ) , & , Si7 Sselj-sput., = 1. 3…”

Section: ( 5 )mentioning

confidence: 99%

Sheath Potential Drop in the Presence of Impurities

Igitkhanov

Naujoks

1996

Contrib. Plasma Phys.

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A b s t r a c tThe effect of secondary electron emission and sputtered impurity ions on the sheath potential drop has been studied. An analytical model has been developed which allows a self-consistent description of the above mentioned effects. In the analysis different materials (two kinds of graphite and tungsten) have been compared and a considerable dependence of the potential drop on the material choice has been observed. It is shown t h a t the most of energy coming from the plasma t o the target is carried by electrons because of both t h e decrease of potential drop caused by SEE and the enhancement of electron current t o the plate caused by sputtering. I n t r o d u c t i o nIn this paper the sheath potential drop at the target in the presence of secondary electron emission and impurity ions sputtered from the target is considered self-consistently. It is shown that the sputtering a t the target can increase the potential drop when impurities cause strong increases of electron upstream density. Impurity flux to the target as far as the secondary electron emission (SEE) from the target can only reduce the potential drop. The SEE yield saturates due to space charge limitations and can not be used to reduce completely the unfavourable effect on sputtering yield of the acceleration by the potential drop even when a dilution effect of positive impurity ions is taken into account. The coinparison of t w o types of carbon (with different SEE) shows considerably different. values of potential drop and eventually results in different sputtering yields. For materials such as tungsten with a high electron emissivity the effect of SEE prevails over the effect of sputtering and leads t o a substantial decrease of the potential drop. The sputtering (and self-sputtering) of tungsten starts t o be significant at some critical electron temperature (which depends on the level of impurity recycling at the target). At a temperature higher than this critical temperature, self-sputtering above 1 can occur. The exact value will depend also on details of the impurity orbits in the sheath electric field. Further, the energy transmission coeffcients for the different species (electrons, plasma ions, impurity ions) have been calculated. Model a n d AssumptionsA schematic of the plasma flow to the target is shown in Fig. 1. We consider a steady state 1-D model with only four species. The background electrons are assumed to be a truncated Maxwellian, so for primary electron density one has:

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“…It should also be noted that, since the S p /g p ratio in Eqs (10) to (14) does not depend on the toroidal geometry of the pumping duct openings owing to the toroidal symmetry of the problem, this geometry can be arbitrary unless it limits the neutral particle penetration into the duct.…”

Section: W =mentioning

confidence: 99%

“…The 2-D calculations in the present paper have been made using the HELIUM code, where the helium transport is modelled on the D-T plasma background computed with the DDC83 code [14]. The transport of He + and He ++ ions is modelled in a simplified rectangular geometry (Fig.…”

Section: Computational Modelmentioning

confidence: 99%

Helium transport in the edge plasma of a tokamak reactor

1991

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A simple linear diffusive/convective model is proposed for helium transport in the edge plasma of a tokamak reactor. Kinetic effects related to weak collisionality of the plasma are assessed. Results of two-dimensional numerical modelling of helium transport in the edge plasma are presented. Issues of ITER divertor optimization with respect to helium exhaust are considered, with a realistic geometry of the divertor plates taken into account.

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A possibility of wall-protecting cold-plasma layer formation in a tokamak reactor

Cited by 6 publications

References 2 publications

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

Sheath Potential Drop in the Presence of Impurities

Helium transport in the edge plasma of a tokamak reactor

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