Dense Deuterium Plasma Research Articles

Повреждаемость и деформационные эффекты в поверхностных слоях меди и сплава системы медь – галлий при импульсном облучении в установке Плазменный фокус

The results of experiments concerning the irradiation of copper and Cu-10% Ga alloys by pulsed fluxes of deuterium plasma (DP) and deuterium ions (DI) performed using a Plasma Focus (PF) unit are presented. The technique of investigation is described. Damage and deformation effects in the surface layers of the mentioned materials after the irradiation of each material in two modes are studied. In one case, the irradiation is performed by a pulsed deuterium plasma at a power density of qpl = 107 W/cm2 and at pulse duration of τpl = 100 ns. In another case, the pulsed fluxes of deuterium ions at qi = 108–1011 W/cm2, τi = 50 ns act simultaneously with a dense deuterium plasma at qpl = 108–109 W/cm2, τpl = 100 ns. Under a less severe irradiation mode (only plasma flux), the levels of damage in the case of both materials are close to each other. In the melted surface layer (SL), there are an undulated surface, craters, and micropores. Under the influence of thermal stresses, a plastic deformation is observed in the SL of the alloy, whereas in the case of pure copper this process is not observed under this irradiation mode. Damage to both materials in a more severe irradiation mode with the pulsed fluxes of deuterium ions and deuterium plasma is enhanced and accompanied by the SL erosion and sometimes by a deposition of microparticles of elements contained in the functional materials of the PF chamber onto the irradiated surface. The most significant damage is observed in the SL of Cu–10% Ga alloy, which, along with the action of powerful plasma beam fluxes, experiences a shock-wave impact. In this irradiation mode, plastic deformation is observed in the SL of each of the materials under consideration. In the case of pure copper (at q = 108–109 W/cm2), the plastic deformation is observed in separate local microvolumes of SL, whereas in the case of copper-gallium alloy at q = 1010–1011 W/cm2 this process occurs within the entire irradiated SL. In this case, plastic deformation occurs both under the action of shock-wave mechanical loads and under the action of thermal stresses.

Effect of Deuterium Plasma Irradiation on V–Ga Alloys

Indentation tests are used to investigate the effect of high-power nanosecond deuterium ion pulses (~100 keV, ~1010 W/cm2) and dense deuterium plasma (~100 eV, ~107 W/cm2) generated by a Plasma Focus machine on the mechanical properties of vanadium-based alloys such as V–5Ti–5Cr, V–5Ga–5Cr, V–5Ga, and V–5Ga–0.1Ce. It is established that the V–Ga–Cr alloys have a higher resistance to embrittlement during radiation-thermal exposure than that of V–Ti–Cr alloys. X-ray diffraction analysis shows that the structure of solid solution is retained in all investigated alloys after pulsed ion and plasma irradiation. No signs of solid solution decomposition and the precipitation of second phases are found. It is established that pulsed ion-plasma irradiation suppresses the rolling texture that is typical of the alloys in the initial state and decreases the lattice parameter of the alloys, which in the case of the V–Ga alloy can be explained by the escape of gallium from the recast surface layer. Doping with a rare earth element (cerium) increases the radiation resistance of the V–Ga alloy, which results in the stability of the mechanical properties and the lattice parameter after irradiation.

Effect of power pulses of deuterium plasma on the structure and mechanical properties of chromium steel

The effect of high-power nanosecond pulsed fluxes of deuterium ions and dense deuterium plasma (108 W/cm2) generated in the Plasma Focus apparatus on the mechanical properties of chromium steel is investigated. It is found that the replacement of carbon in composition of the ferrite 12 Cr–2 W–0.1 C steel by nitrogen leads to dramatic embrittlement and softening of the steel caused apparently by formation of brittle nitrides of iron and/or tungsten. Irradiation with powerful pulses of hot plasma improves the mechanical properties of nitrous ferrite steel owing to dissolution of the brittle precipitations of nitride phases and formation of nanoscale particles of W, which is confirmed by X-ray analysis of irradiated steel. Ferrite chromium steels without nitrogen and austenitic manganese steels show a high stability of the mechanical properties under irradiation with powerful pulses of deuterium plasma.

Deposition of multicomponent filmlike coating on metal substrate using plasma focus device

Results of the investigation of multicomponent coating deposition on the metal substrate in the cathode part of a dense plasma focus device are presented. The features of the processes accompanying the coating are considered: evaporation of elements of chromium-manganese austenite 25Cr12Mn20W tube, which was located along the axis of the plasma focus PF-1000 chamber, under high temperature dense deuterium plasma and deposition of the elements on the model material in form of a copper arc. It is shown that, in the realized exposure mode (the power density of the plasma flow qp = 108–109 W/cm2 in the zone of its impact on the tube and qp = 106 W/cm2 in the region of interaction of the plasma with the copper substrate), the proposed method makes it possible to obtain a coating of submicron thickness on the substrate surface, which includes the evaporated elements of the steel tube. The combined action of powerful streams of fast deuterons and hot plasma in the central part of the copper arc was examined. The structural state, elemental composition, mechanical characteristics, and possible mechanisms for hardening of the deposited film coating are discussed.

Behavior and microstructural changes in different tungsten-based materials under pulsed plasma loading

In this study, morphological, microstructural and phase changes of four types of tungsten materials after exposure to dense deuterium plasma were examined. The microstructures of the prepared materials mutually differ by the porosity, grain size and phase content. It was found that inherent porosity of sintered materials leads to a specific mechanism of erosion and might be a significant source of dust in the case of materials with higher porosity. Further, a preferential erosion of the dispersed particles by melting and evaporation and subsequent formation of thin film on the surface of W-Y2O3 was described as well.

Comparison of damages in tungsten and tungsten doped with lanthanum-oxide exposed to dense deuterium plasma shots

Changes in the surface and structure of tungsten and tungsten doped with 1% lanthanum-oxide samples irradiated by powerful deuterium plasma shots are investigated. Comparative analysis of the samples microroughness, the damage factor estimated from SEM images, and the hardness of cross-sections has been carried out. It can be concluded that the doping of tungsten with 1% lanthanum-oxide may decrease the development of a mesh of microcracks on the irradiated surface. However, this doping may increase the microroughness of the sample surface.

Unipolar arc damage of materials in a hot, dense deuterium plasma

We have determined the damage kinetics of unipolar arcing in a shock tube environment with an ion temperature of about 600 eV and a particle flux of about 10 23 ions/cm β s. Included in our study are the stainless steels AISI 304, 316 and Nimonic PE-16; the refractory metals Nb, Nb-751, T-111, Mo-TZM and W and isotropic reactor grade graphite. We find, for example, that unipolar arcing is a significant damage mechanism that is observed to occur on all materials tested; that arcing produces cathode spots preferentially at microstructural heterogeneities, that, with certain exceptions, differences in the chemistry of widely different metals and alloys did not result in resolvable differences in area coverage owing to arcing and that powder metallurgical W, martensitic 4130 and isotropic, bulk graphite are much more susceptible to arcing than the other materials. The results are discussed with respect to anticipated impurity fluxes into plasmas and with respect to arc theory.