E. L. Surmenko

Prospects for the LIBS study of films using an axicon optical system

The features of the application of an axicon optical system for the LIBS sampling are described. For the axicon sampling, the crater depth is less than that for a conventional spherical lens. The zone of thermal effect around a sampling point is also reduced. The results obtained indicate that the axicon optical system is promising for the thin-film study.

Laser forming of emitting structure of metal-porous cathodes

Metal-porous cathode is an electrovacuum EHF device, providing a high density of emission current. The emitting surface of the device is usually obtained by ion etching. The emitting layer is made of a porous sponge of a refractory metal, usually tungsten. Through the pores of the sponge alkaline earth metals and their oxides are delivered to the emitting surface. One of the most important parameters of the cathode is a uniformity of emission, depending on regularity of the location of pores. We describe a method of laser modification of metal-porous cathode surface, instead of traditional ion etching. The preferences of laser etching are uniformity of pores, absence of deformation of surface, opportunity to specify the necessary size of the pores and the distance between them. Laser structuring of the cathode surface was implemented by laser micrograving. The resulting structure is a field of pores, diameter 15 μm, with spacing of 20 μm.

Laser formation of tip emitting structures with high aspect ratio on glass-carbon field-emission cathodes

Paper describes the method of creating the sharp emitting tips on the surface of a field- emission cathode. The needle-shaped structures with a high aspect ratio on the glass-carbon plate are produced by means of nanosecond laser micromachining. The operations of laser scribing, milling and cleaning were applied for fabrication of the single- and multi-tip field-emission cathode. The special technique of laser rough and fine milling provided high tips with sharp and smooth apexes. As a result we obtained the tips with aspect ratio up to 600. The tests of cathodes showed that high density of current emission and a shorter technological route of production to be reached.

Model of mechanical effect of nanosecond laser radiation upon monolithic glassy carbon on formation of an emitting structure

A mathematical model of the mechanical effect of nanosecond laser pulse radiation on brittle materials is suggested. An analytic technique is developed for estimating the strength of monolithic glassy carbon on formation on its surface of an emitting structure by a series of nanosecond laser pulses with high energy density.

Spectroscopic study of demineralization and restoration processes in dental enamel

The spectroscopic study of dental enamel by LIBS (laser induced breakdown spectroscopy), FTIR (Fourier transform infrared) and XRD (X-ray diffraction) are represented. The changes of enamel structure and composition in process of natural (caries) and artificial demineralization and restoration were studied. In comparison of sound and carious enamel LIBS showed a decrease of the content of Ca, P and change of the content of some other macro-and trace elements (Mn, Na, Fe, Zn etc). The character of the elemental composition variation was stipulated by the concrete disease. Analysis of FTIR and XRD spectra of dental samples, subjected to artificial demineralization and restoration, showed that restoration action reveals slower, than demineralization. And in some cases the damage of crystals after restoration is more significant than after demineralization.

Laser microspectral analysis of superthin evaporations of unknown composition

Laser microspectral analysis is an effective method for determination of composition of thin films and evaporations. In the paper results on investigation of accidental superthin evaporations are described. The composition of evaporations allows one to make conclusion about their source.