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Optical fiber sensors for measurement strain and vibration
Mikel, Břetislav; Helán, R.; Buchta, Zdeněk; Holík, M.; Jelínek, Michal; Číp, Ondřej
2015 - English
We present optical fiber sensors to measurement strain and vibration. The sensors are based on fiber Bragg gratings (FBG). We prepared construction of strain sensors with respect to its implementation on the outer surface of concrete structures and with compensation of potential temperature drifts. These sensors are projected with look forward to maximal elongation and strength which can be applied to the sensor. Each sensor contains two optical fibers with FBGs. One FBG is glued into the sensor in points of fixation which are in the line with mounting holes. This FBG is prestressed to half of measurement range, than the stretching and pressing can be measured simultaneously by one FBG. The second FBG is placed inside the sensor without fixation to measure temperature drifts. The sensor can be used to structure health monitoring.
Keywords:
fiber Bragg gratings; tilted fiber Bragg gratings; length measurement; vibration measurement; optical fiber sensors; fiber tapering
Available at various institutes of the ASCR
Optical fiber sensors for measurement strain and vibration
We present optical fiber sensors to measurement strain and vibration. The sensors are based on fiber Bragg gratings (FBG). We prepared construction of strain sensors with respect to its implementation ...
Iodine-frequency stabilized Telecom laser diode at 515 nm
Philippe, Ch.; Du Burck, F.; Acef, O.; Hrabina, Jan; Pham, Minh Tuan
2015 - English
We have developed an original frequency tripling process based on a compact Telecom laser diode operating around 1542 nm associated to PPLN nonlinear crystals. The optical setup is fully fibred and delivers up to 300 mW at 514 nm. This output generated green radiation is used to probe a molecular vapor inserted in a 20 cm long iodine cell developed by ISI lab. The frequency stability of that reference laser is daily controlled within few parts of 10-16 over 1000 s of integration time. Allan variance associated to the frequency stability of our iodine stabilized telecom laser diode decreases with a slope of 1.4x10-13 with a minimum value of 3x10-14 around 40 s.
Keywords:
laser standards; laser spectroscopy; metrology
Available at various institutes of the ASCR
Iodine-frequency stabilized Telecom laser diode at 515 nm
We have developed an original frequency tripling process based on a compact Telecom laser diode operating around 1542 nm associated to PPLN nonlinear crystals. The optical setup is fully fibred and ...
Interferometric coordinates measurement sytem for local probe microscopy nanometrology
Hrabina, Jan; Lazar, Josef; Klepetek, P.; Číp, Ondřej; Čížek, Martin; Holá, Miroslava; Šerý, Mojmír
2014 - English
We present an overview of new approaches to the design of nanometrology measuring system with a focus on methodology of nanometrology interferometric techniques and associated problems. The design and development of a nanopositioning setup with interferometric multiaxis monitoring and control involved for scanning probe microscopy techniques (primarily atomic force microscopy, AFM) for detection of the sample profile is presented. Coordinate position sensing allows upgrading the imaging microscope techniques up to quantified measuring. Especially imaging techniques in the micro- and nanoworld overcoming the barrier of resolution given by the wavelength of visible light are a suitable basis for design of measuring systems with the best resolution possible. The system is being developed in cooperation with the Czech metrology institute and it is intended to operate as a national nanometrology standard combining local probe microscopy techniques and sample position control with traceability to the primary standard of length.
Keywords:
Nanometrology; Interferometry; Traceability; Local probe microscopy; Nanopositioning
Available at various institutes of the ASCR
Interferometric coordinates measurement sytem for local probe microscopy nanometrology
We present an overview of new approaches to the design of nanometrology measuring system with a focus on methodology of nanometrology interferometric techniques and associated problems. The design and ...
Temperature Inversion and Heat Transport Against the Temperature Drop in Two-Phase Convection of Cryogenic Helium
Urban, Pavel; Schmoranzer, D.; Hanzelka, Pavel; Skrbek, L.
2014 - English
In the system of two bodies A and B connected by a two-phase vapour-liquid system consisting only of cryogenic helium, we observed anomalous heat transport from the colder but heated body B to the warmer but cooled body A. We noticed this effect during the process of liquid evaporation inside a cylindrical pressure convection cell used for study of Rayleigh-Bénard convection. This anomalous heat transfer occurs under non-equilibrium conditions, owing to the phase transitions that take place inside the cell while temperature inversion develops between the heated but cooler bottom plate and the cooled but warmer top plate. This process is, by virtue of the system being open with respect to heat transport, in no contradiction to the second law of thermodynamics, and a numerical model was formulated that describes the observations with good agreement.
Keywords:
cryogenic helium; two-phase convection; temperature inversion; rain formation; Cryogenics
Available at various institutes of the ASCR
Temperature Inversion and Heat Transport Against the Temperature Drop in Two-Phase Convection of Cryogenic Helium
In the system of two bodies A and B connected by a two-phase vapour-liquid system consisting only of cryogenic helium, we observed anomalous heat transport from the colder but heated body B to the ...
Design and Testing of Low Temperature Part of an UHV – SPM Microscope
Frolec, Jiří; Vonka, J.; Hanzelka, Pavel; Králík, Tomáš; Musilová, Věra; Urban, Pavel
2014 - English
We have developed low temperature part of an ultra high vacuum scanning probe microscope (UHV-SPM) working at variable temperature within the range from 20 K to 700 K. To achieve the required temperature range, a flow cooling system using cryogenic helium (approximately 5 K) as a coolant was designed. The system consists of a flow cryostat and a flexible low-loss transfer line connecting a Dewar vessel with the flow cryostat. We have also tested liquid nitrogen (approximately 77 K) as an alternative low-cost coolant. Using nitrogen, the microscope can operate at temperatures of about 100 K and higher. As the flow of the coolant through the cryostat can cause thermally induced two-phase flow fluctuations resulting in instability in temperatures, preliminary tests were done in order to find ways of avoiding the temperature oscillations and optimising the cooling process.
Keywords:
flow cryostat; VT-SPM; LT-SPM; low conductive support; cryogenics
Available at various institutes of the ASCR
Design and Testing of Low Temperature Part of an UHV – SPM Microscope
We have developed low temperature part of an ultra high vacuum scanning probe microscope (UHV-SPM) working at variable temperature within the range from 20 K to 700 K. To achieve the required ...
Measurement of current density distribution in shaped e-beam writers
Horáček, Miroslav; Bok, Jan; Kolařík, Vladimír; Urbánek, Michal; Matějka, Milan; Krátký, Stanislav
2014 - English
The ZrO W(100) Schottky cathode is used in our e-beam writing system working with a rectangular-shaped electron beam. The homogeneous angular current density distribution is crucial for quality of exposures of the shaped beam lithography systems. Two basic types of the angular emission distribution can be observed in dependence on the microscopic final end form shape of the emitter tip, with bright centre and more common dark centre. The stable operation of the cathode thus stable end form shape requires a delicate balance of parameters inside the gun which however can slightly change during cathode life time. This implies the necessity of analysing and periodical monitoring the current density distribution in e-beam. Four methods enabling this measurement are presented.
Keywords:
e-beam writer; current density
Available at various institutes of the ASCR
Measurement of current density distribution in shaped e-beam writers
The ZrO W(100) Schottky cathode is used in our e-beam writing system working with a rectangular-shaped electron beam. The homogeneous angular current density distribution is crucial for quality of ...
Ultra-low-energy STEM in SEM
Frank, Luděk; Nebesářová, J.; Müllerová, Ilona
2014 - English
Examination of thin samples in TEM or STEM has been performed at hundreds of keV. This energy range offered high resolution but low contrasts which meant that tissue sections had to be contrasted with heavy metal salts. Recent TEM with aberration correctors preserve an acceptable resolution down to 20 keV and provide enhanced contrasts. The LVTEM device is operated at 5 keV on samples thinner than 20 nm. STEM attachments to SEMs have become widespread [3] profiting from an image contrast substantially increasing even for light elements at tens or units of keV. The methods for the preparation of ultrathin sections of various substances are capable of producing layers at and even below 10 nm which enables one to further decrease the energy of the electrons provided the image resolution is maintained. When using the STEM technique virtually all transmitted electrons can be utilised for imaging, while in TEM we are restricted to using electrons capable of forming the final image at acceptable quality. This forces us to narrow the ranges of the angular and energy spreads of electrons that enter the image-forming lenses. Consequently, the STEM technique promises higher contrasts at comparable resolutions. Unlimited reduction of the energy of the illuminating electrons is possible by employing the cathode lens principle. This consists of biasing the sample together with its holder (made flat on both sides) to a high negative potential that retards the incident electrons before they land on the sample surface and accelerates backscattered and transmitted electrons to their respective detectors above and below the sample. Calculations have shown a final spot size only moderately extended even at units of eV so that quality-consistent micrographs can be recorded over the full energy scale.
Keywords:
tissue section; biological STEM; low energy STEM; low energy electrons
Available at various institutes of the ASCR
Ultra-low-energy STEM in SEM
Examination of thin samples in TEM or STEM has been performed at hundreds of keV. This energy range offered high resolution but low contrasts which meant that tissue sections had to be contrasted ...
Photonic Crystal Structure of Butterfly Wing Scales Exhibiting Selective Wavelength Iridescence
Matějková-Plšková, J.; Mika, Filip; Jiwajinda, S.; Dechkrong, P.; Svidenská, S.; Shiojiri, M.
2014 - English
Characteristic patterns and the vivid coloration of the wing scales of butterflies have lately attracted considerable attention as natural photonic crystals. The coloration of butterflies that exhibit human visible iridescence from violet to green has been elucidated. A Sasakia charonda (S. charonda) or ‘great purple emperor’ butterfly was sampled in a woodland in Japan, and an Euploea mulciber (E. mulciber) or 'striped blue crow’ butterfly was reared from an egg at the Environmental Entomology Research and Development Center, Kasetsart University.
Keywords:
butterfly wing; coloration; SEM; TEM; photonic crystal structure
Available at various institutes of the ASCR
Photonic Crystal Structure of Butterfly Wing Scales Exhibiting Selective Wavelength Iridescence
Characteristic patterns and the vivid coloration of the wing scales of butterflies have lately attracted considerable attention as natural photonic crystals. The coloration of butterflies that exhibit ...
Progress in imaging techniques for characterization of polyelectrolyte complex microcapsules as encapsulation matrice for biocatalysts
Bučko, M.; Gemeiner, P.; Vikartovská, A.; Schenkmayerová, A.; Bertóková, A.; Lacík, I.; Chorvát Jr., D.; Neděla, Vilém
2014 - English
Polyelectrolyte complex microcapsules showed to be an univerzal encapsulation matrice for wide range of biocatalysts including viable, native and recombinant bacterial cells, non-viable bacterial cells as well as enzymes. Developed continuous encapsulation protocol based on the polyelectrolyte complexation of oppositely charged polymers enabled production of uniform microcapsules with a controlled shape, size, membrane thickness, permeability and mechanical resistance. The characterisation and control of the microcapsule properties including the inner structure and surface properties was inevitable to determine their proper function and predictability in important applications such as the stabilisation and reuse of encapsulated biocatalysts for more efficient production of valuable compounds. Recent utilisation of unique environmental scanning electron microscope enabled an innovative observation and characterization of capsule morphology in native and fully hydrated state. Achieved results and comparison with previously used conventional microscopic techniques will be presented.
Keywords:
ESEM; matrice for biocatalysts
Available at various institutes of the ASCR
Progress in imaging techniques for characterization of polyelectrolyte complex microcapsules as encapsulation matrice for biocatalysts
Polyelectrolyte complex microcapsules showed to be an univerzal encapsulation matrice for wide range of biocatalysts including viable, native and recombinant bacterial cells, non-viable bacterial ...
Analysis of the gas glow
Hladká, K.; Maxa, J.; Neděla, Vilém; Vyroubal, P.; Vaculík, S.; Hlavatá, P.
2014 - English
In order to optimize the shape of the Differentially pumped chamber in the area of the Primary Electron Beam passage for the current concept of the location of the foci of the Primary Electron Beam, it was necessary to adapt to the size and shape of the limitations of the existing structure. On fig. 1a is the total cross sectional view of the Differentially pumped chamber. Three variants were examined: Current concept with an easily machined shape of the passage of the primary beam, semi-closed concept with a conical shape, cone concept with a wider cone.
Keywords:
SEM; ESEM; gas glow; analysis
Available at various institutes of the ASCR
Analysis of the gas glow
In order to optimize the shape of the Differentially pumped chamber in the area of the Primary Electron Beam passage for the current concept of the location of the foci of the Primary Electron Beam, ...
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