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Stable Ce4+ centres - a tool to optimize cathodoluminescence performance in garnet scintillators
Lalinský, Ondřej; Schauer, Petr; Rathaiah, M.; Kučera, M.
2018 - English
Garnet single crystals are widely used as scintillators in electron detectors. Cerium activated lutetium aluminum garnet Cex:Lu3-xAl5O12 (LuAG:Ce) is a promising example of such material for these applications. This is mainly due to its high light yield (LY) of 25 kph/MeV, short decay time of 60–80 ns, high atomic density (6.7 g/cm3), and high radiation stability with no hygroscopicity. The cathodoluminescence (CL) performance can be improved by Ga and Gd doping the garnet matrix. Proper admixture of these elements can increase the LY to 50–60 kph/MeV in addition to eliminating unwanted slower decay components. There was an idea that further decay acceleration can be achieved by doping the garnet with monovalent (Li+) or divalent ions (Mg2+, Ca2+). This should increase the valency of some Ce3+ centres to Ce4+ which should better compete with electron traps, and thus accelerate the decay. Our previous work proved the same decay trend, however, at a price of the LY. Such LY loss may induce the idea, if the stable Ce4+ centres are really participating in Ce3+ emission.
Keywords:
garnet scintillators; cathodoluminescence performance
Available at various institutes of the ASCR
Stable Ce4+ centres - a tool to optimize cathodoluminescence performance in garnet scintillators
Garnet single crystals are widely used as scintillators in electron detectors. Cerium activated lutetium aluminum garnet Cex:Lu3-xAl5O12 (LuAG:Ce) is a promising example of such material for these ...
Optofluidic techniques for directed evolution of enzymes
Pilát, Zdeněk; Ježek, Jan; Samek, Ota; Zemánek, Pavel; Buryška, T.; Damborský, J.; Prokop, Z.
2018 - English
Enzymes are highly versatile and ubiquitous biological catalysts. They can greatly accelerate\nlarge variety of reactions, while ensuring appropriate catalytic activity and high selectivity.\nThese properties make enzymes attractive biocatalysts for a wide range of industrial and\nbiomedical applications. Over the last two decades, directed evolution of enzymes has\ntransformed the field of protein engineering.
Keywords:
optofluidics; Raman spectroscopy; enzymes
Available at various institutes of the ASCR
Optofluidic techniques for directed evolution of enzymes
Enzymes are highly versatile and ubiquitous biological catalysts. They can greatly accelerate\nlarge variety of reactions, while ensuring appropriate catalytic activity and high selectivity.\nThese ...
Real time observation of strain in the SEM sample
Piňos, Jakub; Frank, Luděk
2018 - English
The SEM with various detector arrangements and analytical attachments represents an\nirreplaceable tool in material research. One of the techniques available in most contemporary\nmicroscopes is the scanning low energy electron microscopy (SLEEM) with biased specimen, marketed as the beam deceleration mode, gentle beam and others. The SLEEM allows\ncontrolling the information depth of the backscatter electron (BSE) imaging within a wide\nrange by altering the landing energy of electrons.
Keywords:
SEM; SLEEM; deformation
Available at various institutes of the ASCR
Real time observation of strain in the SEM sample
The SEM with various detector arrangements and analytical attachments represents an\nirreplaceable tool in material research. One of the techniques available in most contemporary\nmicroscopes is the ...
Grazing incidence interferometer for form measurement of hollow cylinders
Šarbort, Martin; Řeřucha, Šimon; Holá, Miroslava; Lazar, Josef
2018 - English
Optical metrology of cylindrical specimens represents an interesting task in scientific and\nindustrial practice. The most precise measurement methods use principles of laser\ninterferometry where the phase difference between the reference wave and the object wave reflected from the tested surface is detected. The form measurement of hollow cylindrical tubes can be advantageously realized by an object wave with conical wavefronts generated by an axicon lens or an equivalent diffractive optical element. An axicon characterized by large apex angle forms a conical wave that fulfills the conditions of the grazing incidence, which results in suppression of the speckle noise. The previous experimental setups were relatively complex since they involved a pair of mutually reversed axicons or a pair of diffractive optical elements that transform the object wave from planar to conical and vice\nversa.
Keywords:
interferometry; surface metrology; hollow cylinders
Available at various institutes of the ASCR
Grazing incidence interferometer for form measurement of hollow cylinders
Optical metrology of cylindrical specimens represents an interesting task in scientific and\nindustrial practice. The most precise measurement methods use principles of laser\ninterferometry where the ...
Imaging via multimode optical fiber: recovery of a transmission matrix using internal references
Šiler, Martin; Jákl, Petr; Traegaardh, Johanna; Ježek, Jan; Uhlířová, Hana; Tučková, Tereza; Zemánek, Pavel; Čižmár, Tomáš
2018 - English
Current research of life shows a great desire to study the mechanics of biological processes\ndirectly within the complexity of living organisms. However, majority of practical techniques\nused nowadays for tissue visualization can only reach depths of a few tens of micrometres as\nthe issue obscures deep imaging due to the random light scattering. Several imaging\ntechniques deal with this problems from different angels, such as optical coherence\ntomography, light sheet microscopy or structured light illumination A different and promising strategy to overcome the turbid nature of scattering tissues is to employ multimode optical fibers (MMF) as minimally invasive light guides or endoscopes to provide optical access inside. Although the theoretical description of light propagation through such fibers has been developed a long time ago it is frequently considered inadequate to describe real MMF. The inherent randomization of light propagating through MMFs is typically attributed to undetectable deviations from the ideal fiber structure. It is a commonly believed that this\nadditional chaos is unpredictable and that its influence grows with the length of the fiber.\nDespite this, light transport through MMFs remains deterministic and can be characterized by a transmission matrix (TM) which connects the intensity and phase patterns on the fiber input and output facets. Once the TM is known it can be used to create focus in any desired 3D\ncoordinates beyond the distal fiber facet, see figure 1, and perform e.g. fluorescence based\nlaser scanning microscopy or optical trapping.
Keywords:
multimode optical fiber
Available at various institutes of the ASCR
Imaging via multimode optical fiber: recovery of a transmission matrix using internal references
Current research of life shows a great desire to study the mechanics of biological processes\ndirectly within the complexity of living organisms. However, majority of practical techniques\nused ...
Electron beam welding at ISI Brno
Dupák, Libor; Zobač, Martin; Vlček, Ivan; Zobačová, Jitka
2018 - English
In vacuum technology, and especially in UHV, we often encounter the necessity of joining\nparts of various metals in combination with the demand for perfect vacuum tightness,\ncleanness of joints and minimum deformations. Electron beam welding belongs to the\nbest technologies capable of fulfilling such requirements.\nThe principle of electron beam welding is based on the transfer of the kinetic energy of the\nincident accelerated electrons to the welded material in the form of heat. The temperature in\nthe spot rises with the beam power density. At power densities as high as 104 - 106 W/mm2,\nthe melted material at the center of the focal point evaporates. This produces a vapor capillary surrounded by melted material that allows the beam to penetrate deeper and melt more material. The speed of the penetration can be much higher than the heat transfer by\nconduction into the surrounding material. This results in narrow melted area and typical knifelike\nprofile of the weld. Thanks to this effect the thermal deformations of welded\npieces are highly reduced to almost none. Small heat affected zone also allows welding near\nheat sensitive parts like sensors, ceramic feed-throughs and brazed joints.
Keywords:
electron beam welding
Available at various institutes of the ASCR
Electron beam welding at ISI Brno
In vacuum technology, and especially in UHV, we often encounter the necessity of joining\nparts of various metals in combination with the demand for perfect vacuum tightness,\ncleanness of joints and ...
Possibilites of a secondary electrons bandpass filter for standard SEM
Mika, Filip; Pokorná, Zuzana; Konvalina, Ivo; Khursheed, A.
2018 - English
Secondary electron filtering in Scanning Electron Microscope (SEM) has been in use for over\na decade. This technique uncovers interesting contrasts in an otherwise ordinary SEM image\nwhich can possibly be used for dopant concentration mapping or for discerning the slight molecular weight differences in apparently homogeneous organic materials. Secondary\nelectron filtering of semiconductor samples seems very promising as it may shed light on the mechanism of SEM image contrast between p-doped and n-doped semiconductors, possibly\nallowing to determine dopant concentration from SEM image alone.
Keywords:
secondary electron; filtering; imaging
Available at various institutes of the ASCR
Possibilites of a secondary electrons bandpass filter for standard SEM
Secondary electron filtering in Scanning Electron Microscope (SEM) has been in use for over\na decade. This technique uncovers interesting contrasts in an otherwise ordinary SEM image\nwhich can ...
Secondary electron hyper spectral imaging in helios nanolab - mapping materials properties or artefacts?
Rodenburg, C.; Masters, R.; Abrams, K.; Dapor, M.; Krátký, Stanislav; Mika, Filip
2018 - English
A link between peaks in secondary electron (SE) spectra and Electron Energy Loss Spectra\n(EELS) was shown decades ago. Also, materials properties (bulk modulus, band gap)\ncorrelate with the bulk plasmon position in EELS, and local modulus maps in carbon fibres\nhave been presented. If any features as result of plasmon decay into SE can be identified,\nSE spectroscopy combined with hyperspectral imaging could transform the SEM into a tool\nfor mapping materials properties with ground-breaking potential for nanotechnology. To\nbecome a reality, we first need to establish SE collection conditions spectra that represent a\nmaterial reliably. Second, we need to gain a better understanding of the processes involved in the SE emission processes.
Keywords:
secondary electrons; polymers; hyperspectral imaging
Available at various institutes of the ASCR
Secondary electron hyper spectral imaging in helios nanolab - mapping materials properties or artefacts?
A link between peaks in secondary electron (SE) spectra and Electron Energy Loss Spectra\n(EELS) was shown decades ago. Also, materials properties (bulk modulus, band gap)\ncorrelate with the bulk ...
Thickness determination of a cathodoluminescence active nanoparticles by means of Quantitative STEM imaging
Skoupý, Radim; Krzyžánek, Vladislav
2018 - English
Labeling of specimens by nanoscale probes is common approach of complex biological\nsystems exploration. Namely gold nanoparticles immuno-staining is well established method\nin electron microscopy. However, if more than two label sizes are used, the differentiation of\nindividual nanoparticles becomes difficult.\nThis can be overcome by cathodoluminescence (CL) active particles – nanophosphors where\nlabels recognition is done by wavelength of emitted light. This gives a great opportunity to\nuse advanced multi probe labeling within one sample.\nThere is a huge variety of nanophosphors: green fluorescent protein, quantum dots, ZnO\nnanoparticles, organic molecules, rare earth-doped nanophosphors etc. Therefore, in order\nto choose best type of nanophosphors for a given task, it is important to measure particles\nsize/thickness, as the CL intensity is proportional to the probe volume.
Keywords:
quantitative imaging; Monte Carlo
Available at various institutes of the ASCR
Thickness determination of a cathodoluminescence active nanoparticles by means of Quantitative STEM imaging
Labeling of specimens by nanoscale probes is common approach of complex biological\nsystems exploration. Namely gold nanoparticles immuno-staining is well established method\nin electron microscopy. ...
Gel Polymer Electrolytes Modified Nanoparticles or Copolymers and Polymerized in Magnetic and Electric Fields
Jahn, M.; Veselková, I.; Sedlaříková, M.; Zatloukal, M.; Bartušek, Karel
2018 - English
Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of electrochemistry. The gel polymer electrolyte is composed of a conductive component (liquid electrolyte) and the polymer component (methacrylate-based polymer). In this paper, I present fundamental characteristics of gel polymer electrolytes modified nanoparticles or copolymers and preparation of these gel polymer materials with nanoparticles or copolymers polymerized in electric and magnetic fields.
Keywords:
magnetic and electric fields; gel polymer electrolytes; nanoparticles
Available at various institutes of the ASCR
Gel Polymer Electrolytes Modified Nanoparticles or Copolymers and Polymerized in Magnetic and Electric Fields
Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of ...
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