|
|
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...
|
|
|
Photon strength functions in 196Pt from two-step gamma cascade measurement
Kloc, Michal ; Krtička, Milan (advisor) ; Cejnar, Pavel (referee)
Photon strength functions (PSFs), using the statistical approach to a nuclear decay, seem to be a suitable tool for the description of the electromagnetic transitions in a nucleus. Since the early 50's, when PSFs were first introduced, a plenty of theoretical models were proposed however their validity is still a question. In this work the data from the measurement of so called Two step cascades in the nucleus 196Pt using the reaction 195Pt(n,gamma)196Pt are processed. The experiment was performed at the Nuclear Physics Institute ASCR in Řež near Prague. We assume that these experimental spectra contain important information on PSFs. Comparison of the processed data with a few Monte Carlo simulations is also a part of this thesis.
|
|
|
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...
|
|
|
Photon strength functions in 168Er from multi-step gamma cascade measurement at DANCE
Knapová, Ingrid ; Krtička, Milan (advisor) ; Pěč, Viktor (referee)
Subject of the thesis is study of photon strength functions describing the gamma decay of the nucleus. During last 50 years a number of theoretical models for these quantities were proposed, however, their accuracy is still de- batable and its verification has recently been a subject of intensive experimental and theoretical research. In this work measurement of multi-step gamma cas- cades following the radiative neutron capture on target nucleus 167 Er is used to analyse photon strength functions. The experiment was performed with DANCE calorimeter located in Los Alamos Neutron Scattering Center. The experimen- tal spectra are compared with Monte Carlo simulations of electromagnetic decay using the DICEBOX algorithm, based on assumptions of Extreme Statistical Model. Comparison of experimental and simulated spectra is a fundamental tool for studying correctness of theoretical models of photon strength functions. This study provides information mainly about E1 and M1 photon strength functions, especially properties of the so-called scissor mode are analysed.
|
|
|
Photon strength functions in 196Pt from two-step gamma cascade measurement
Kloc, Michal ; Krtička, Milan (advisor) ; Cejnar, Pavel (referee)
Photon strength functions (PSFs), using the statistical approach to a nuclear decay, seem to be a suitable tool for the description of the electromagnetic transitions in a nucleus. Since the early 50's, when PSFs were first introduced, a plenty of theoretical models were proposed however their validity is still a question. In this work the data from the measurement of so called Two step cascades in the nucleus 196Pt using the reaction 195Pt(n,gamma)196Pt are processed. The experiment was performed at the Nuclear Physics Institute ASCR in Řež near Prague. We assume that these experimental spectra contain important information on PSFs. Comparison of the processed data with a few Monte Carlo simulations is also a part of this thesis.
|
guest ::
