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Optical fibers for measuring ionizing radiation
Jelínek, Michal ; Mikel, Břetislav
Optical fiber ionising radiation measurements cannot be used to continuously measure high-energy ionising radiation, especially gamma radiation. Previously presented sensors and methods use optical fibers with a scintillator on/inside the fiber, optical fibers doped with a scintillator, etc. These methods are not suitable for measuring high-energy radiation mainly due to low efficiency. Therefore, we present a measurement method where optical fibers are used only to transport the scintillation radiation to the shielded detection electronics.
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SMV-2020-55: ADJ3 standard
Hrabina, Jan ; Jelínek, Michal ; Čížek, Martin ; Číp, Ondřej
The contractual research was oriented towards works on ADJ3-CESNET laser standard:\n- analysis and measurement of actual parameters of the system \n- reduction of electric noise (control system) \n- optical polarization stabilization (beat-note measurements) \n- upgrading of control SW \n- PID control optimalization, verification tests of the system
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Rozšíření české dubové standardní chronologie o letokruhové křivky ze subfosilních dubových kmenů z Polabí
Jelínek, Michal
Subfossil trunks are unfossilized woods which are discovered rarely in the Czech Republic. The aim of this work was to find, sampled and dated subfossil trunks from the Polabí region. Available Czech and foreign standard chronologies were used for dendrochronological dating of tree-ring series. Simultaneously, earlier sampled subfossil trunks from the study area were assembled. The chosen tree-ring series were used to extension and improvement of the Czech oak standard chronology. Selected samples, which were not possible to dendochronologically date, were sent for radiocarbon dating. For a purpose of this work, 122 new subfossil findings were dendrochronologically processed from the Polabí region and three samples were prepared and sent for radiocarbon dating. The major part of subfossil trunks was identified as an oak and only 5 samples as an elm. In total, 96 samples were successfully dated mostly into two periods: 3500 - 3200 BC and 133 BC - 155 AD. In Kostomlátky location, the oldest oak subfossil trunk in the Czech republic was found the tree-ring series covers the period 8181 7971 BC. Thanks to these subfossil findings, the Czech oak standard chronology could be extended.
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Optical Fibers Forming For Optical Sensors
Research
Jelínek, Michal
We present development of new methods and techniques of the splicing and shaping optical fibers with focusing to development new sensors. We developed new techniques of splicing for standard Single Mode (SM) and Multimode (MM) optical fibers and optical fibers with different diameters in the wavelength range from 532 to 1550 nm. Together with development these techniques we prepared other techniques to splicing and shaping special optical fibers like as Polarization-Maintaining (PM) or hollow core Photonic Crystal Fiber (PCF) and theirs cross splicing methods with focus to minimize backreflection and attenuation. Splicing special optical fibers, especially PCF fibers with standard telecommunication and other SM fibers, can be done by light adjustment of our developed techniques.
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Interferometric System for Length Calibration on a Metre Scale
Jedlička, Petr ; Mikel, Břetislav ; Řeřucha, Šimon ; Matěj, Z. ; Herman, O. ; Holá, Miroslava ; Jelínek, Michal ; Pavelka, Jan ; Číp, Ondřej ; Lazar, Josef
Interferometric system is designed to calibrate the measurement frame, used for periodic assessment of the inner geometry of the reactor active zone chassis. Calibration lenght is up to 3300mm.
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Stable optical frequency transfer between ISI and CESNET workplaces
Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Jelínek, Michal ; Hrabina, Jan ; Řeřucha, Šimon ; Mikel, Břetislav ; Lazar, Josef ; Číp, Ondřej ; Smotlacha, V. ; Havliš, O. ; Vojtěch, J.
The contribution reports on the current state of a 306km long experimental line for transfering stable optical frequency from a telecommunication band laser standard between ISI CAS (Brno) and CESNET (Prague). The bidirectional link uses a telecommunication fiber with a dedicated DWDM window of 1540-1546 nm.1540-1546 nm. In the Czech rep. this technology can be utilized currently in two fields: remote comparisons of optical frequency standards and remote callibration of instruments (optical spectral analyzers) in industrial applications that do not allow transporting the device to a specialized laboratory. The stability of the optical frequency transfer was evaluated. A long-term measurement of transport delay was conducted. \n
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Calibration of the FBG Measuring System by Laser Interferometer
Jelínek, Michal
This work deals with calibration method of the FBG based sensors and the nuclear power plant containment shape monitoring system. The design and the implementation of this system with the optical filter thermal compensation is described. The measurement of length changes is compared with the Michelson interferometer. The control system was programmed in LabVIEW.
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Optical fiber sensors for measurement strain and vibration
Mikel, Břetislav ; Helán, R. ; Buchta, Zdeněk ; Holík, M. ; Jelínek, Michal ; Číp, Ondřej
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.
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Special optical fibers and optical fiber sensors in Institute of Scientific Instruments of the CAS
Jelínek, Michal ; Mikel, Břetislav
Optical fiber sensors are applied in many industrial sectors. Great development of fiber optic sensors was focused to using fiber Brag gratings in the last years. Nowadays the primary focus is aimed to development fiber optic sensors using Raman or Brillouin scattering and microstructural fibers. Different types of optical sensors are currently used in many industrial sector from telecommunications, automotive, aerospace, oil industry to nuclear power systems and other critical infrastructures. We present our research of optical fiber sensors uses new technologies of measurements and optical fibers preparation.
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