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1

Study of tungsten surface interaction with plasma streams at DPF-1000U

100%

Ladygina M. S., Skladnik-Sadowska E., Zaloga D. R., Malinowski K., Sadowski M. J., Kubkowska M., Kowalska-Strzeciwilk E., Paduch M., Zielinska E., Miklaszewski R., Garkusha I. E., Gribkov V. A.

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issue 2

293-296

EN

In this note experimental studies of tungsten (W) samples irradiated by intense plasma-ion streams are reported. Measurements were performed using the modified plasma focus device DPF-1000U equipped with an axial gas-puffing system. The main diagnostic tool was a Mechelle®900 optical spectrometer. The electron density of a freely propagating plasma stream (i.e., the plasma stream observed without any target inside the vacuum chamber) was estimated on the basis of the half-width of the Dβ spectral line, taking into account the linear Stark effect. For a freely propagating plasma stream the maximum electron density amounted to about 1.3 × 1017 cm−3 and was reached during the maximum plasma compression. The plasma electron density depends on the initial conditions of the experiments. It was thus important to determine first the plasma flow characteristics before attempting any target irradiation. These data were needed for comparison with plasma characteristics after an irradiation of the investigated target. In fact, spectroscopic measurements performed during interactions of plasma streams with the investigated W samples showed many WI and WII spectral lines. The surface erosion was determined from mass losses of the irradiated samples. Changes on the surfaces of the irradiated samples were also investigated with an optical microscope and some sputtering and melting zones were observed.

2

Identifying the crossover between growth regimesvia in-situconductance measurements in focused electron beam induced deposition

100%

Winhold M., Weirich P. M., Schwalb C. H., Huth M.

Nanofabrication

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2014

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vol. 1

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issue 1

EN

Focused electron beam induced deposition presents a promising technique for the fabrication of nanostructures. However, due to the dissociation of mostly organometallic precursor molecules employed for the deposition process, prepared nanostructures contain organic residues leading to rather low conductance of the deposits. Post-growth treatment of the structures by electron irradiation or in reactive atmospheres at elevated temperatures can be applied to purify the samples. Recently, an in-situ conductance optimization process involving evolutionary genetic algorithm techniques has been introduced leading to an increase of conductance by one order of magnitude for tungsten-based deposits using the precursor W(CO)6. This method even allows for the optimization of conductance of nano-structures for which post-growth treatment is not possible or desirable. However, the mechanisms responsible for the observed enhancement have not been studied in depth. In this work, we identified the dwell-time dependent change of conductivity of the samples to be the major contributor to the change of conductance. Specifically, the chemical composition drastically changes with a variation of dwelltime resulting in an increase of the metal content by 15 at% for short dwell-times. The relative change of growth rate amounts to less than 25 % and has a negligible influence on conductance. We anticipate the in-situ genetic algorithm optimization procedure to be of high relevance for new developments regarding binary or ternary systems prepared by focused electron or ion beam induced deposition.

3

Heat load and deuterium plasma effects on SPS and WSP tungsten

86%

Vilémová M., Matějíček J., Nevrlá B., Chernyshova M., Gasior P., Kowalska-Strzeciwilk E., Jäger A.

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issue 2

275-283

EN

Tungsten is a prime choice for armor material in future nuclear fusion devices. For the realization of fusion, it is necessary to address issues related to the plasma–armor interactions. In this work, several types of tungsten material were studied, i.e. tungsten prepared by spark plasma sintering (SPS) and by water stabilized plasma spraying (WSP) technique. An intended surface porosity was created in the samples to model hydrogen/helium bubbles. The samples were subjected to a laser heat loading and a radiation loading of deuterium plasma to simulate edge plasma conditions of a nuclear fusion device (power density of 108 W/cm2 and 107 W/cm2, respectively, in the pulse intervals up to 200 ns). Thermally induced changes in the morphology and the damage to the studied surfaces are described. Possible consequences for the fusion device operation are pointed out.

4

Overview of processing technologies for tungsten-steel composites and FGMs for fusion applications

86%

Matějíček J., Nevrlá B., Vilémová M., Boldyryeva H.

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issue 2

267-273

EN

Tungsten is a prime candidate material for the plasma-facing components in future fusion devices, e.g. ITER and DEMO. Because of the harsh and complex loading conditions and the differences in material properties, joining of the tungsten armor to the underlying construction and/or cooling parts is a complicated issue. To alleviate the thermal stresses at the joint, a sharp interface may be replaced by a gradual one with a smoothly varying composition. In this paper, several techniques for the formation of tungsten-steel composites and graded layers are reviewed. These include plasma spraying, laser cladding, hot pressing and spark plasma sintering. Structure, composition and selected thermal and mechanical properties of representative layers produced by each of these techniques are presented. A summary of advantages and disadvantages of the techniques and an assessment of their suitability for the production of plasma-facing components is provided.

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3 Nukleonika

1 Nanofabrication

3 2015

1 2014

2 Kowalska-Strzeciwilk E.

2 Matějíček J.

2 Nevrlá B.

2 Vilémová M.

1 Boldyryeva H.

1 Chernyshova M.

1 Garkusha I. E.

1 Gasior P.

1 Gribkov V. A.

1 Huth M.

1 Jäger A.

1 Kubkowska M.

1 Ladygina M. S.

1 Malinowski K.

1 Miklaszewski R.

1 Paduch M.

1 Sadowski M. J.

1 Schwalb C. H.

1 Skladnik-Sadowska E.

1 Weirich P. M.

1 Winhold M.

1 Zaloga D. R.

1 Zielinska E.

Study of tungsten surface interaction with plasma streams at DPF-1000U

Identifying the crossover between growth regimesvia in-situconductance measurements in focused electron beam induced deposition

Heat load and deuterium plasma effects on SPS and WSP tungsten

Overview of processing technologies for tungsten-steel composites and FGMs for fusion applications