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Correction of misalignment aberrations of a hexapole corrector using the differential algebra method
Radlička, Tomáš; Oral, Martin
2016 - English
Overcoming the limitations of the Schertzer theorem is a long story in electron microscopy. Although the basic principle of a spherical aberration (C3) correction was suggested as early as in 1947 the first experimental correctors of spherical aberration were only realized in the last decade of the 20th century. The recent multipole correctors are designed for high-energy\nTEM or STEM, where the corrector system enables reaching the atomic resolution. On the other\nhand, the corrector for low-energy SEM has been developed but this type of corrector must also contain chromatic aberration (Cc) correction to reduce the effect of the non-zero energy width. Recently, the energies of SEM reach 30 keV and transmission mode (TSEM) is a standard part of the instrument. Standard resolution in TSEM is about 0.6 nm and it is limited by C3. Reaching atomic resolution with this set-up is not a real expectation because of its instability, but the resolution of about 0.2 nm would increase the field of applications. Corrector for these type of instruments should be (a) simple, compact and cheap (b) only spherical aberration of the third,\noptionally the fifth order must be corrected (c) effect of the chromatic aberration may be reduced by energy filtering. We studied design based on Rose’s hexapole corrector.
Keywords:
electron microscopy; Schertzer theorem; TEM; STEM
Available at various institutes of the ASCR
Correction of misalignment aberrations of a hexapole corrector using the differential algebra method
Overcoming the limitations of the Schertzer theorem is a long story in electron microscopy. Although the basic principle of a spherical aberration (C3) correction was suggested as early as in 1947 the ...
Difraction in a scanning electron microscopie
Řiháček, Tomáš; Mika, Filip; Matějka, Milan; Krátký, Stanislav; Müllerová, Ilona
2016 - English
Manipulation with the primary beam phase in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) has drawn significant attention in the microscopy community in the recent years. Although a few applications were found long before, some are still subjects of a future research. One of them is the use of electron vortex beams, which has very promising potential. It ranges from probing magnetic materials and manipulating with nanoparticles to spin polarization of a beam in an electron microscope.\nThe methods for producing electron vortex beams have undergone a lot of development in recent years as well. The most versatile way is holographic reconstruction using computer-generated holograms modifying either phase or amplitude. As the method is\nbased on diffraction, beam coherence is a very important parameter here. It is usually performed in TEM at energies of about 100 – 300 keV which are well suited for diffraction on artificial structures for two reasons. The coherence of the primary beam is often reasonable, and the diffraction pattern is easily observed. This is however not the case for a standard scanning electron microscope (SEM) with typical energy up to 30 keV.
Keywords:
electron microscopy; TEM; STEM
Available at various institutes of the ASCR
Difraction in a scanning electron microscopie
Manipulation with the primary beam phase in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) has drawn significant attention in the microscopy community ...
Measurement of Concentration of Air Ions in the Cisarska Cave
Roubal, Z.; Szabó, Z.; Bartušek, Karel; Steinbauer, M.
2016 - English
It was confirmed that the concentration of light air ions has a positive influence on human health. In the Cisarska Cave is sanatorium for treatment of asthma. For analyse this cave was performed measurement of concentration of light negative ions. Using grounding was reduced measurement uncertainty.
Keywords:
air ions; measurement of concentration
Available at various institutes of the ASCR
Measurement of Concentration of Air Ions in the Cisarska Cave
It was confirmed that the concentration of light air ions has a positive influence on human health. In the Cisarska Cave is sanatorium for treatment of asthma. For analyse this cave was performed ...
Measurement of real-time gigacycle fatigue through real-time interferometry
Lazar, Josef; Holá, Miroslava; Hrabina, Jan; Číp, Ondřej
2015 - English
We present an interferometric method for measurement of strain induced deformation of metal samples in experiments inducing high-cycle fatigue. The motivation is to get real-time information about the deformation of a metal sample under test, its elongation imposed by fast vibrating actuator. Fatigue of materials is a process of degradation of a material due to repeated application of forces which includes nucleation and propagation of cracks and leads to the failure of the component. It may appear in all parts of machines or structures which rotate, vibrate, are repeatedly loaded, are subjected to temperature gradients etc., so statistically, fatigue is implied in about 80% of all industrial failures.
Keywords:
optical metrology; metallurgy
Available at various institutes of the ASCR
Measurement of real-time gigacycle fatigue through real-time interferometry
We present an interferometric method for measurement of strain induced deformation of metal samples in experiments inducing high-cycle fatigue. The motivation is to get real-time information about the ...
Absorption cells based on HC-PCF fibers
Oulehla, Jindřich
2015 - English
This work is oriented towards our research in the field of splicing and ending of optical frequency references based on hollow core photonics crystal fibers (HC-PCF). This type of references is very promising optical element to replacing c assic bulky absorption cells for laser frequency stabilizat on. We prepared and present methods of splicing HC-PCF to standard telecommunication fiber by a fiber splicer. A special care was taken to optimize the splicer setting and to find and obtain a splice with minimal optical losses between HC-PCF and SMF. The manufactured fiber cell was closed at one side by connecting to SMF and second fiber end was prepared for placing into the vacuum chamber with the help of vacuum-tightened connection to be used as a optical frequency reference based on the acetylene gas for frequency stabilization of the laser standards.
Keywords:
absorption cell; fiber; optical frequency reference; metrology
Available at various institutes of the ASCR
Absorption cells based on HC-PCF fibers
This work is oriented towards our research in the field of splicing and ending of optical frequency references based on hollow core photonics crystal fibers (HC-PCF). This type of references is very ...
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 ...
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