K. B. Abramova

Emission processes accompanying deformation and fracture of metals

Present-day physical methods of investigation reveal that the fracture and plastic deformation of metals is accompanied by emission processes, in particular, by luminescence and emission of electrons. All the metals studied thus far exhibit a capability of luminescence. The intensity, duration, and spectrum of mechanoluminescence are different for different metals. The intensity is determined by the mechanical and thermal characteristics. For a given metal, the intensity depends on dislocation density in the structure and the sample loading rate. The spectrum of noble metals is governed by the electronic structure of surface states. The dynamics of mechanoluminescence and electron emission (exoemission) depends on the rate of stress variation in the sample under study. This permits one to consider the mechanoluminescence and exoemission not only as physical characteristics but also as a potential tool for probing surface states in metals and the kinetics of emergence of mobile dislocations on the surface with a high time resolution.

Effect of the microstructure of a metal on the emission spectrum excited during destruction of current-carrying conductors by an MHD instability

The spectral characteristics of the radiation emitted during the destruction of copper conductors with different microstructures by a high-density current are investigated experimentally. The proposed mechanisms leading to radiation generation and the experimental results corresponding to these mechanisms are discussed.

Photon emission from metals under fast nondestructive loading

A study is reported of the mechanoluminescence excited on the backside of metal samples whose front side is irradiated by single laser pulses with an energy below the onset of spallation. The temporal and spatial distributions of temperature, thermal stresses, and thermal-stress variation rates are calculated. The temporal dependence of mechanoluminescence from metal targets is compared with calculations of the mechanical stresses initiated in the targets under pulsed loading. The dynamics of the emission process are shown to be governed by those of loading.

The emission of photons and the dynamics of submicrodefects on the surface of noble metals

The shape and concentration of defects, as well as the intensity of electroluminescence from the back side of Cu, Ag, and Au samples with their front side irradiated by a laser shot, are studied experimentally. It is shown that there exists a correlation between the electroluminescence intensity and the concentration of radiation-induced defects, which is consistent with the dislocation model of luminescence.

Mechanoluminescence and submicrorelief of a copper surface

Copper plates are irradiated with pulsed laser light on one side, and the opposite side is investigated with a scanning tunneling microscope. It is found that the submicrorelief of the back surface changes after irradiation. During irradiation it emits a light pulse. It is established that a relation exists between the luminescence intensity and the magnitude of the change in the surface submicrorelief.

Molding loose metal particles into briquettes with the use of short pulses of high density current

Theoretical estimates and experimental investigations were carried out on the process of molding a mixture of metal particles and a dielectric (air) into briquettes with the use of short pulses of high density current. Four groups of specimens were studied consisting of metal fragments and the dielectric in various proportions. In the experiments and the current and voltage oscillograms, the electrical resistance and the temperature of the specimens before and after passing the current were measured and their ultimate strength was determined. It has been found that the processes affecting the distribution of the current over the specimen cross section and the specimen inductance during the current pulse play an important role in molding briquettes of sufficient strength for transportation and processing.

Dynamics of photon emission due to strains in metals

Calculations of a photon emission pulse generated on the back side of a metallic sample laser-irradiated on its front side are performed. A detailed comparison with experimental data is made.

Multicharged ion source based on the Tornado closed magnetic confinement system

It is proposed to use the Tornado closed magnetic confinement system with microwave plasma heating for creating a pulsed source of multicharged ions. The plasma losses in closed confinement systems are determined by the diffusion across the magnetic field, which substantially increases the plasma lifetime as compared to mirror confinement systems. A plasma heating scenario with the successive switching-on of two oscillators is proposed: an oscillator operating at a frequency of 2.45 GHz produces the initial plasma, which is then heated at a frequency of 15 or 53 GHz. It is shown that it is possible to achieve the distribution of ions over charge states with a maximum at Ar16+ at a plasma density of 2×1013 cm−3. The extracted ion current in this case can attain 1 A.