Nanostructures in controlled thermonuclear fusion devices

Krauz, V. I.; Martynenko, Yu. V.; Svechnikov, N. Yu.; Smirnov, V. P.; Stankevich, V. G.; Khimchenko, L. N.

doi:10.3367/ufne.0180.201010c.1055

Cited by 34 publications

(18 citation statements)

References 57 publications

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“…46,47 Furthermore, analogous structures were observed in PECVD processing, for instance, during early stages of ultrananocrystalline diamond growth 48,49 or during growth of carbon nanowalls. 5,50 The exposures in Pilot-PSI stand out since they were performed at plasma flux at least 2 orders of magnitude higher than in the other experiments listed here.…”

Section: B Location and Structure Of The Redepositsmentioning

confidence: 86%

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Bystrov

Vegt

Temmerman

et al. 2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Fine-grain graphite samples were exposed to high density low temperature (ne∼1020 m−3, Te∼1 eV) hydrogen plasmas in the Pilot-PSI linear plasma generator. Redeposition of eroded carbon is so strong that no external precursor gas injection is necessary for deposits to form on the exposed surface during the bombardment. In fact, up to 90% of carbon is redeposited, most noticeably in the region of the highest particle flux. The redeposits appear in the form of carbon microparticles of various sizes and structures. Discharge parameters influence the efficiency of the redeposition processes and the particle growth rate. Under favorable conditions, the growth rate reaches 0.15 μm/s. The authors used high resolution scanning electron microscopy and transmission electron microscopy to study the particle growth mode. The columnar structure of some of the large particles points toward surface growth, while observation of the spherical carbon nanoparticles indicates growth in the plasma phase. Multiple nanoparticles can agglomerate and form bigger particles. The spherical shape of the agglomerates suggests that nanoparticles coalesce in the gas phase. The erosion and redeposition patterns on the samples are likely determined by the gradients in plasma flux density and surface temperature across the surface.

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Section: B Location and Structure Of The Redepositsmentioning

confidence: 86%

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Bystrov

Vegt

Temmerman

et al. 2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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show abstract

“…Eroded material enters the plasma and is then redeposited on the sur face. As a result, composite amorphous films [1,2] with the inhomogeneous surface having a stochastic shape such as, e.g., cauliflower are formed on the sur face of the chamber of the nuclear fusion facility. The granularity hierarchy of structures (fractality) from nanometers to micrometers is a characteristic property of the relief of such a surface.…”

Section: Introductionmentioning

confidence: 99%

“…The aim of this work is to study the fractal structure of the surface of films observed in tokamaks [1,2,5]. The self similarity of the stochastic relief of such frac tal films was analyzed in [1] using data obtained with a scanning tunneling microscope with a scanning field (spatial base of measurements) of 8 × 8 μm.…”

Section: Introductionmentioning

confidence: 99%

Long-range correlations in the structure of fractal films

et al. 2012

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“…If arcs are burning at the first wall liquid particles as a typical product of arc erosion will be ejected from the typical craters (figure 1) into the SOL [1,2,3,4,5]. During its flight through the plasma the particles will be evaporated [6,7] introducing wall material into the SOL and, eventually, some may even cross the LCFS thereby injecting a fraction of the impurity material into the confined central plasma column. If W was chosen as the principal PFC material (as in ASDEX Upgrade and JET realized and for ITER planned) any erosion resulting in macro-particle emission is important because it potentially bypasses the desired prompt re-deposition of W [8].…”

Section: Introductionmentioning

confidence: 99%

Modification of arc emitted W particles in a model scrape-off layer plasma

Laux

Balden

Siemroth³

2014

Phys. Scr.

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Abstract. In fusion machines (like e.g. ASDEX Upgrade and JET) equipped with W-coated plasma facing components (PFCs) arc tracks are observed post-mortem and W-particles are identified as a component of the dust. Results from laboratory arcing of W-coated PFC-material concerning the size, velocity, and direction of macro-particles are combined with model calculations of the heating, cooling, and evaporation of W particles flying through a simplified scrape-off layer (SOL) plasma to assess the role of arc produced particles as a source of W-impurities. W atoms or ions eroded from a macro-particle flying across the SOL plasma are not subject to prompt re-deposition onto a PFC. Therefore, macro-particles constitute an essential source of W in the SOL and even may result in an impurity input into the region of confined plasma if the particle succeeds to path the SOL and cross the last closed flux surface (LCFS). The main result of the modelling is that a W-particle from the large-size end of the distribution obtained in laboratory arcing and having a typical velocity (also known from laboratory experiment) is able to pass a SOL of 10cm thickness filled with a realistic plasma and, finally, inject a certain amount of Wmaterial into the confined plasma region.

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Nanostructures in controlled thermonuclear fusion devices

Cited by 34 publications

References 57 publications

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Long-range correlations in the structure of fractal films

Modification of arc emitted W particles in a model scrape-off layer plasma

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