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1

Damage and modification of materials produced by pulsed ion and plasma streams in Dense Plasma Focus device

Pimenov V. N., Demina E. V., Ivanov L. I., Gribkov V. A., Dubrovsky A. V., Ugaste U., Laas T., Scholz M., Miklaszewski R., Kolman B., Tartari A.

Nukleonika

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2008

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Vol. 53, No. 3

111-121

EN

The Dense Plasma Focus (DPF) devices PF-1000, PF-6 and PF-5M working with different gases and in dissimilar irradiation modes were used to carry out experimental investigations of irradiation of a number of materials by powerful pulsed ion and high-temperature plasma streams. The materials under test were designed for application in structural and functional components of thermonuclear fusion devices with magnetic (MPC) and inertial (IPC) plasma confinement, as well as for working chambers of plasma and accelerator devices. The main features of the materials are low-activation and radiation-resistant properties. On the basis of the investigations a significant progress was achieved in understanding of dynamics of high-energy nano- and micro-second pulsed streams in DPF from one side as well as on the mechanisms of their influence upon materials under irradiation from the other one. We demonstrated that this approach can be useful for certain tests of plasma-facing materials (e.g. W for MPC and stainless steels for IPC) and of structural (construction) elements of the above-mentioned devices subjected to pulsed high-energy radiation streams. The results obtained suggest also that DPF devices can be used in new pulse technologies for material treatment by means of powerful nanosecond and microsecond pulses of plasma and ion streams.

2

Coloured-noise-induced transitions in nonlinear structures

Mankin R., Laas T., Soika E., Sauga A., Rekker A., Ainsaar A., Ugaste U.

Nukleonika

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2008

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Vol. 53, No. 3

127-134

EN

In a stochastic framework, macroscopic approaches are sought to describe microscopic interaction between different species. Coloured-noise-induced transitions in stochastic N-species Lotka-Volterra systems are considered analytically as an appropriate model extendable to many natural and nano-technological processes. All the results discussed are computed by means of a dynamical mean-field approximation. It is demonstrated that interplay of coloured noise and interaction intensities of species can generate a variety of cooperation effects, such as discontinuous transitions of the mean population density, noise-induced Hopf bifurcations and relaxation oscillation. The necessary conditions for the cooperation effects are also discussed. Particularly, it is established that, in the case of the Beddington functional response, in certain parameter regions of the model an increase in noise correlation time can cause multiple transitions (more than two) between relaxation oscillatory regimes and equilibrium states.

3

Surface and bulk processes in materials induced by pulsed ion and plasma beams at Dense Plasma Focus devices

Pimenov V., Maslyaev S., Ivanov L., Dyomina E., Gribkov V., Dubrovsky A., Scholz M., Miklaszewski R., Ugaste U., Kolman B.

Nukleonika

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2006

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Vol. 51, nr 1

71-78

EN

A review of results and new data on the interaction of pulsed ion and dense plasma beams with metals in different Dense Plasma Focus (DPF) devices are presented. Different irradiation conditions with microsecond pulses of the power density in the range of 105 109 W/cm2 were applied. The most interesting thermal and radiation effects observed in both surface and bulk of the material positioned at the cathode part of the DPF device have been considered. Advanced directions of DPF use for scientific and applied problems of radiation material science were determined.

4

Colored-noise-induced anomalous transport in periodic structures

Laas T., Sauga A., Mankin R., Ainsaar A., Ugaste U., Rekker A.

Nukleonika

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2006

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Vol. 51, nr 1

63-69

EN

Colored-noise-induced anomalous transport phenomena of overdamped particles in a tilted periodic sawtooth potential driven by a nonequilibrium three-level noise and an additive thermal noise are considered analytically. All the physical results discussed are computed by means of exact formulas. It is demonstrated that the particles exhibit anomalous transport properties, such as, multiple change in the sign of the particle flow, absolute negative mobility, negative differential mobility, hypersensitive transport, and hypersensitive differential response. The necessary conditions for various anomalous transport properties are found. It is established that in certain parameter regions an increase in noise parameters (noise-flatness, correlation time, temperature) can facilitate the conversion of noise energy into mechanical work - i.e., the dependence of the efficiency of energy transformation on noise parameters exhibits a bellshaped (resonance) form. Some possible applications to fluctuation-induced separation of particles as well as to the amplification of small signals are also discussed. Our results provide some new perspectives to support elaboration of a model of interaction between plasma beams and construction materials in plasma focus devices.

5

Influence of powerful pulses of hydrogen plasma upon materials in PF-1000 device

Pimenov V., Gribkov V., Dubrovsky A., Mezzetti F., Scholz M., Ugaste U., Dyomina E., Ivanov L., Maslyaev S., Miklaszewski R., Borowiecki M., De Chiara P., Pizzo L., Szydlowski A., Volobuev I. V.

Nukleonika

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2002

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Vol. 47, nr 4

155-162

EN

The results of experimental investigations of powerful hydrogen plasma jets and fast ion beams interaction with various materials (austenitic chromium-manganese steels, pure vanadium, tungsten, graphite, copper, and their alloys: Cu-4 mass% Ni and Cu-10 mass% Ga) are presented. The materials were placed on the discharge axis of the PF-1000 device and irradiated with fluxes of fast ions (of energy in the range from tens keV up to several MeV) and with plasma streams (of power flux density q~(108 109) W/cm2). It was found that the fast ions and plasma streams caused different damages to the aforementioned materials. A diverse character of the damages to the individual investigated material was revealed. Some peculiarities of the process as well as the correlation between the surface density of the "macroscopic" structural defects (blisters and craters) and the fluence of the fast ions implanted in the specimen are discussed.