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Study of gamma rays in decay of 83Rb/83mKr
Zach, František ; Šefčík, Michal (advisor) ; Valenta, Stanislav (referee)
In this work, the energies and intensities of gamma rays in the radioactive decay of 83 Rb were measured. The intermediate product, 83m Kr, is an important calibration source for several experiments. For the measurements, germanium (HPGe) and silicon (SiLi) detectors were used and calibrated with the radioactive standards 55 Fe, 133 Ba, 152 Eu and 241 Am. Part of the work was also to measure the shielding caused by the emitters housings and the escape of 83m Kr gas from the sample before its decay. The DEIMOS program was used for the primary processing of the measurements.
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Studies of the K-shell double vacancy production in the electron capture decays of 55Fe, 54Mn and 65Zn using hybrid pixel detectors
Kaplan, Martin ; Bergmann, Benedikt (advisor) ; Valenta, Stanislav (referee)
The presented thesis provides an experimental study of the K-shell double vacancy production in the electron capture decays of 55 Fe, 54 Mn, 65 Zn using a pair of Timepix3 detectors. Measured data are preprocessed and explored. The methodology for the cal- culation of the probability of K-shell double vacancy production in 55 Fe and 54 Mn is developed. Therefore, an extensive amount of signal and background processes were con- sidered during the development of the methodology. The measurement setup is defined and optimized in the Allpix2 framework for a simulation of detection efficiencies of par- ticles participating in the signal and background processes. The probability of K-shell double vacancy creation in the electron capture decay of 55 Fe was measured to be PKK = (1.406 ± 0.05) × 10−4 with a systematic error of ∆sys(PKK) =+0.030 −0.034 ×10−4 . The value of PKK for the electron capture decay of 54 Mn found to be PKK = (3.93 ± 0.44) × 10−4 with a systematic error of ∆sys(PKK) =+0.25 −1.11 ×10−4 . Resulting probabilities for K-shell double vacancy production in 55 Fe and 54 Mn are in agreement with the latest results. 1
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Study of statistical decay in well deformed rare-earth nuclei
Valenta, Stanislav ; Krtička, Milan (advisor) ; Pospíšil, Stanislav (referee) ; Veselý, Petr (referee)
The γ decay of highly excited nuclear levels can be described within the statistical model of nucleus in terms of the level density and a set of photon strength functions. The knowledge of these quantities enables more accurate calculations of reaction rates in many different reactions which are important especially in nuclear astrophysics and in the development of advanced nuclear reactors. Despite the fact that the photon strength functi- ons have been studied for decades, there are still contradicting experimental results regarding the low energy behavior of dipole strength. One of these ca- ses is the shape of electric dipole photon strength function and the strength of the scissors mode in well-deformed rare-earth nuclei. In this thesis the ana- lyses of γ-ray spectra measured by two different experimental setups are pre- sented. The two-step γ cascades measurements with odd gadolinium targets were performed at the research reactor LVR-15 at the Research Centre Řež. In the multi-step γ cascades experiments the γ rays following resonance ne- utron capture on 161−163 Dy targets were measured with the highly-segmented γ-ray calorimeter Detector for Advanced Neutron Capture Experiments in the Los Alamos Neutron Science Center at Los Alamos National Labora- tory. Experimental spectra were compared...
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Experimental determination of the gamma ray intensities in 83Rb/83mKr /83Kr decay chain
Zach, František ; Šefčík, Michal (advisor) ; Valenta, Stanislav (referee)
The aim of this work is to measure the intensities of gamma decays of 83 Rb, which decays into stable 83 Kr through a metastable 83m Kr with monoenergetic electron spectrum and is thus very suitable for calibration of experiments, such as KATRIN or XENON. Part of the work is also the calibration of the detector used for measurement (semiconductor HPGe, ie High Purity Germanium) using isotopes 241 Am, 152 Eu and 133 Ba with known intensities. The work managed to measure the values of the intensities of gamma transitions in the nucleus during the decay of 83 Rb to 83 Kr, together with the detector calibration and finding the dependence of the detection efficiency on energy.
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Study of statistical decay in well deformed rare-earth nuclei
Valenta, Stanislav ; Krtička, Milan (advisor) ; Pospíšil, Stanislav (referee) ; Veselý, Petr (referee)
The γ decay of highly excited nuclear levels can be described within the statistical model of nucleus in terms of the level density and a set of photon strength functions. The knowledge of these quantities enables more accurate calculations of reaction rates in many different reactions which are important especially in nuclear astrophysics and in the development of advanced nuclear reactors. Despite the fact that the photon strength functi- ons have been studied for decades, there are still contradicting experimental results regarding the low energy behavior of dipole strength. One of these ca- ses is the shape of electric dipole photon strength function and the strength of the scissors mode in well-deformed rare-earth nuclei. In this thesis the ana- lyses of γ-ray spectra measured by two different experimental setups are pre- sented. The two-step γ cascades measurements with odd gadolinium targets were performed at the research reactor LVR-15 at the Research Centre Řež. In the multi-step γ cascades experiments the γ rays following resonance ne- utron capture on 161−163 Dy targets were measured with the highly-segmented γ-ray calorimeter Detector for Advanced Neutron Capture Experiments in the Los Alamos Neutron Science Center at Los Alamos National Labora- tory. Experimental spectra were compared...
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Photon strength functuins in 177Lu from two-step gamma cascade measurement
Valenta, Stanislav ; Krtička, Milan (advisor) ; Kvasil, Jan (referee)
The subject of the study made in this work are photon strength functions. Many models, both based on theoretical as well as phenomenological approaches, were proposed for these quantities, describing the gamma decay of the nucleus, during last 50 year. However, the correctness of these models is still questionable and its verification is the subject of intensive experimental and theoretical activity at the present time. The results of the analysis of measurements of the two-step cascades following thermal neutron capture on the 176Lu nucleus are compared with the outputs of the Monte Carlo simulations based on the validity of the so-called Extreme Statistical Model. Comparison of experimental data with outcomes of simulations thus becomes the basic tool for studying correctness of theoretical models. The experiment analyzed in the present work provides information mainly about E1 and M1 photon strength functions, especially about the so-called scissors resonance.
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