National Repository of Grey Literature 5 records found  Search took 0.00 seconds. 
Sputtering of dust grains and its consequences for space processes.
Vyšinka, Marek ; Šafránková, Jana (advisor)
Title: Sputtering of dust grains and its consequences for space processes Author: Marek Vyšinka Department: Department of Surface and Plasma Science Supervisor: prof. RNDr. Jana Šafránková, DrSc., Department of Surface and Plasma Science Abstract: A great part of matter in a space has a form of dust grains, tiny pieces of rocks with the dimensions of hundreds nanometers to hundreds micrometers. In this environment dust grains undergo collisions with energetic particles (electron, ions, UV photons) that leads to their charging and modification. The presented thesis studies ion-dust interactions and is focussed on dust grain modification through ion implantation and its destruction via sputtering process. Two compu- ter models are presented - first for computing the ion implantation profile in the grain and second, for the shape of the sputtered grain lying on the surface of a bigger object. The resulting shape of the grain is compared with that obtained experimentally. Important results of the thesis are measured sputtering yields for spherical SiO2 grains at several surface potentials obtained by simultaneous ion and electron bombardments. Keywords: ions, dust grains, sputtering, sputtering yield, implantation profile 1
Sputtering of dust grains and its consequences for space processes.
Vyšinka, Marek ; Šafránková, Jana (advisor) ; Stöckel, Jan (referee) ; Wild, Jan (referee)
Title: Sputtering of dust grains and its consequences for space processes Author: Marek Vyšinka Department: Department of Surface and Plasma Science Supervisor: prof. RNDr. Jana Šafránková, DrSc., Department of Surface and Plasma Science Abstract: A great part of matter in a space has a form of dust grains, tiny pieces of rocks with the dimensions of hundreds nanometers to hundreds micrometers. In this environment dust grains undergo collisions with energetic particles (electron, ions, UV photons) that leads to their charging and modification. The presented thesis studies ion-dust interactions and is focussed on dust grain modification through ion implantation and its destruction via sputtering process. Two compu- ter models are presented - first for computing the ion implantation profile in the grain and second, for the shape of the sputtered grain lying on the surface of a bigger object. The resulting shape of the grain is compared with that obtained experimentally. Important results of the thesis are measured sputtering yields for spherical SiO2 grains at several surface potentials obtained by simultaneous ion and electron bombardments. Keywords: ions, dust grains, sputtering, sputtering yield, implantation profile 1
Proposal of ultrasonic trap
Bartoň, Petr ; Pavlů, Jiří (advisor) ; Vyšinka, Marek (referee)
Light scattering by dust grains is a complex problem when the size of the grain is about the wavelength of incident light. The Mie theory is often used to characterize such situtation, however, most of the materials lacks knowledge of neccessary material constants. Moreover, solution of Mie equations for general shapes is difficult and partly not known. Objective of this work is development of apparatus for light scattering measurements on small (micrometer ranged) ar- bitrary shaped dust grains levitating in the ultrasonic field. Trap parameters are obtained by survey of literature and by numeric simulations leading to design of reliable ultrasonic levitator including optical system. The results enable manu- facturing and completion of such apparatus. Eventually, this work can serve as guide "how to design ultrasonic levitator".
Ion attachment and ion emission of dust grains
Vyšinka, Marek ; Němeček, Zdeněk (advisor) ; Wild, Jan (referee)
Small dust grains could be found in many environments. Because of their size, their charge and the electric forces acting on them play an important role in their dynamics. The dust grain charge is influenced by many different processes. Among other methods, charging processes can be studied by trapping a single dust grain inside an electrodynamic quadrupole where it is put into specific environment (ion or electron beam, UV radiation). The progress of the charging process can be inferred from the changes in the grain charge. Our work contributed to the building of a new laboratory set-up for study of the charging processes. Specifically, a new Faraday cup for measurements and stabilization of the ion and electron gun currents is designed and its function verified. It solves the shortcomings of the previously used Faraday cups. Further, an amplifier for the ion gun current measurement is designed and constructed along with the design of digital stabilization of the current. The stabilization is neccesary for the interpretation of measurement results and its digitalization will allow more flexible adjustment and easier connection with the control computer. Finally, data acquired during the charging of dust grain with different ion species are evaluated in order to study the effect of different ions on surface...

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