National Repository of Grey Literature 3 records found  Search took 0.00 seconds. 
Study of gamma decay in 168Er from neutron capture
Knapová, Ingrid ; Krtička, Milan (advisor) ; Gunsing, Frank (referee) ; Veselý, Petr (referee)
The γ-ray emission process in highly-excited nuclei is typically described within the statistical model of nucleus using the two main ingredients - the level density (LD) and the photon strength functions (PSFs). The knowledge of LD and PSFs is essential in the modeling of nuclear reactions with applications in astrophysics or advanced nuclear reac- tors. In this work, we studied the multi-step γ-ray cascade spectra following the radiative neutron capture 167 Er(n, γ)168 Er measured with the Detector for Advanced Neutron Cap- ture Experiments in Los Alamos National Laboratory. The experimental γ-ray spectra were compared with the simulated spectra exploiting the dicebox Monte Carlo code for simulation of radiative decay to test different models of LD and PSFs. Furthermore, the measured spectra allowed us to determine the population of the isomeric state in 168 Er with 109 ns half-life and compare it with the simulated isomeric population, which provides an important test of the applicability of the statistical model. The simulated isomeric population was found to be significantly lower than the experi- mental one if no structure effects are assumed above the excitation energy of the isomer. If we adopt the decay scheme up to excitation energy well above 2 MeV, we obtain the simulated isomeric ratio...
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.
Influence of the Detection Threshold on the Response of the C6D6 Detectors
Knapová, Ingrid ; Krtička, Milan (advisor) ; Pěč, Viktor (referee)
Scintillation C6D6 detectors are used for radiative capture cross-section measurements in various neutron time-of-flight facilities (n_TOF in CERN, GELINA in IRMM Geel). To determinate cross-section with the help of Pulse Height Weighting Technique we usually neglect influence of undetectable energy, derived from two phenomena - internal conversion and detection threshold for low photon energies. However, in some cases their impact cannot be completely omitted and due to lack of knowledge it has not been the subject of research yet. The purpose of this thesis is to study the influence of these two effects from simulations of neutron radiative capture induced photon spectra. Two nuclei: 197 Au and 238 U were used for testing.

See also: similar author names
1 Knapová, Iva
1 Knapová, Ivana
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