Elektronų prožektoriaus katodų pozicionavimo sistema.

The results of the investigations of the dual-stage cathode positioning system with more than 150 mm motion range and ±1 μm positioning accuracy are presented. The maximum allowable speed of the second stage actuator, securing the integrity of the cathode surface, of 10 mm/s was determined experimentally. The dynamic model of the cathode-probe system allowed to explore the dynamics of the interaction force and the dependencies of their character on the viscous friction

Augančio kondensato elektrinės varžos nustatymas.

The flow of the thermionic emission was used for non-invasive measurements of the growing condensate resistance. The mathematical and physical models were created for the simplification of the method of the resistance measuring. These models explain relationship between the alternation of the measured signal and the resistance of condensate. It was explored, that the extreme of the measured signal and the moment of its appearance depend on the input resistance of the measuring instrument. The instantaneous resistance of condensate was identified from the experimental signals. This method is right for the measuring of the condensate resistance, when the condensate is in the island stage

Operating point of Capacitive Micromachined Ultrasonic Transducers with Sub-structural Elements

CMUT FEM 2D electrostatic model was created to investigate dielectric surface roughness influence to the operating point. Three different form structures: triangle, halfcircle, rectangle were investigated. The highest electric field norm concentration on the triangle apex was found. For experiments, dielectric surface was etched by two etching steps to define the cavity: reactive ion etching and buffered oxide etching for smoothing the cavity bottom. Atomic force microscopy was used to monitor and control the roughness of the cavity bottom. The simulation showed the decrease of the effective gap by 0.6 % and 1.0 % in 10 and 20 nm RMS cases, respectively. Voltage-capacitance tests of the fabricated devices with known roughness values confirmed the assumptions about the roughness-induced operating point shifts