Photon strength functions in Gd isotopes studied from resonance neutron capture

Title: Photon strength functions in Gd isotopes studied from resonance neutron capture Author: RNDr. Jiří Kroll Department: Intitute of particle and nuclear physics Supervisor: doc. Mgr. Milan Krtička, Ph.D., Intitute of particle and nuclear physics Abstract: Photon strength functions have been studied for more than sixty years. A number of theoretical models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at present time. In this thesis the analysis of spectra of γ rays following the radiative capture of neutrons on isolated neutron resonances of 152,154−158 Gd nuclei is used to study photon strength functions. Experimental data were measured using segmented DANCE calorimeter that is installed at Los Alamos Neutron Scattering Center in New Mexico, USA. Experimental spectra are then compared with the outputs of Monte Carlo simulation of nuclear elec- tromagnetic decay, performed by DICEBOX code, that is based on the validity of the so-called Extreme Statistical Model. The response of the detector system to generated γ cascades was subsequently calculated using the Geant4 code. An analysis of the data clearly indicates that magnetic..

Photon strength functuins in 160Tb from two-step gamma cascade measurement

Title: Photon strength functions in nucleus 160 Tb from the two-step γ cascades measurements Author: Jiří Kroll Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Milan Krtička, Ph.D. Supervisor's e-mail address: [email protected] Abstract: Photon strength functions have been a subject of a study for more than fifty years. A number of models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at the present time. In the present work the analysis of measurements of the two-step γ cascades following the slow neutron capture on the 159 Tb nucleus is used for study of photon strength functions. Results of the experimental data analysis are compared with the outputs of the Monte Carlo simulations based on the validity of so called Extreme Statistical Model. Comparison of experimental data with outcomes of simulations thus becomes the basic tool for studying correctness of theoretical models. Keywords: Photon strength function, Energy level density, Extreme Statistical Mode

Study of photon strength functuins from two-step cascade measurements

Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Photon strength functuins in 160Tb from two-step gamma cascade measurement

Title: Photon strength functions in nucleus 160 Tb from the two-step γ cascades measurements Author: Jiří Kroll Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Milan Krtička, Ph.D. Supervisor's e-mail address: [email protected] Abstract: Photon strength functions have been a subject of a study for more than fifty years. A number of models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at the present time. In the present work the analysis of measurements of the two-step γ cascades following the slow neutron capture on the 159 Tb nucleus is used for study of photon strength functions. Results of the experimental data analysis are compared with the outputs of the Monte Carlo simulations based on the validity of so called Extreme Statistical Model. Comparison of experimental data with outcomes of simulations thus becomes the basic tool for studying correctness of theoretical models. Keywords: Photon strength function, Energy level density, Extreme Statistical Mode

Photon strength functuins in 160Tb from two-step gamma cascade measurement

Title: Photon strength functions in nucleus 160 Tb from the two-step γ cascades measurements Author: Jiří Kroll Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Milan Krtička, Ph.D. Supervisor's e-mail address: [email protected] Abstract: Photon strength functions have been a subject of a study for more than fifty years. A number of models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at the present time. In the present work the analysis of measurements of the two-step γ cascades following the slow neutron capture on the 159 Tb nucleus is used for study of photon strength functions. Results of the experimental data analysis are compared with the outputs of the Monte Carlo simulations based on the validity of so called Extreme Statistical Model. Comparison of experimental data with outcomes of simulations thus becomes the basic tool for studying correctness of theoretical models. Keywords: Photon strength function, Energy level density, Extreme Statistical Mode

Fotonové silové pole v izotopech Gd studované rezonančním záchytem elektronů

Název práce: Fotonové silové funkce v izotopech Gd studované rezonančním záchytem neutronů Autor: RNDr. Jiří Kroll Katedra: Ústav částicové a jaderné fyziky Vedoucí disertační práce: doc. Mgr. Milan Krtička, Ph.D., Ústav částicové a jaderné fyziky Abstrakt: Studium fotonových silových funkcí probíhá již více než šedesát let. Za tuto dobu byla vytvořena celá řada teoretických modelů, které se pokoušejí objasnit experimentální výsledky. Korektnost těchto modelů je však stále velice diskutabilní a její ověření je v současné době předmětem intenzivní experimentální i teoretické činnosti. V předkládané práci studujeme fotonové silové funkce na základě analýzy spekter γ-záření doprovázejícího radiační záchyt neutronů na izolovaných neutronových rezonancních jader 152,154−158 Gd. Experimentální data byla nameřena pomocí segmentovaného kalorimetru DANCE, který je instalován v Los Alamos Neutron Scattering Center v Novém Mexiku, USA. Experimentální spektra jsou následně porovnána s výstupy Monte Carlo simulace elektromagnet- ického rozpadu jader DICEBOX, založené na předpokladu platnosti tzv. Ex- trémního Statistického Modelu. Odezva detektoru na vygenerované γ-kaskády je následně vypočtena pomocí...Title: Photon strength functions in Gd isotopes studied from resonance neutron capture Author: RNDr. Jiří Kroll Department: Intitute of particle and nuclear physics Supervisor: doc. Mgr. Milan Krtička, Ph.D., Intitute of particle and nuclear physics Abstract: Photon strength functions have been studied for more than sixty years. A number of theoretical models was proposed to describe experimental data during that time. However, the correctness of these models is still very questionable and its verification is the subject of very intensive experimental and theoretical activity at present time. In this thesis the analysis of spectra of γ rays following the radiative capture of neutrons on isolated neutron resonances of 152,154−158 Gd nuclei is used to study photon strength functions. Experimental data were measured using segmented DANCE calorimeter that is installed at Los Alamos Neutron Scattering Center in New Mexico, USA. Experimental spectra are then compared with the outputs of Monte Carlo simulation of nuclear elec- tromagnetic decay, performed by DICEBOX code, that is based on the validity of the so-called Extreme Statistical Model. The response of the detector system to generated γ cascades was subsequently calculated using the Geant4 code. An analysis of the data clearly indicates that magnetic...Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Measurements of neutron cross sections for advanced nuclear energy systems at n_TOF (CERN)

The n_TOF facility operates at CERN with the aim of addressing the request of high accuracy nuclear data for advanced nuclear energy systems as well as for nuclear astrophysics. Thanks to the features of the neutron beam, important results have been obtained on neutron induced fission and capture cross sections of U, Pu and minor actinides. Recently the construction of another beam line has started; the new line will be complementary to the first one, allowing to further extend the experimental program foreseen for next measurement campaigns

Neutron cross-sections for advanced nuclear systems: the n_TOF project at CERN

The study of neutron-induced reactions is of high relevance in a wide variety of fields, ranging from stellar nucleosynthesis and fundamental nuclear physics to applications of nuclear technology. In nuclear energy, high accuracy neutron data are needed for the development of Generation IV fast reactors and accelerator driven systems, these last aimed specifically at nuclear waste incineration, as well as for research on innovative fuel cycles. In this context, a high luminosity Neutron Time Of Flight facility, n_TOF, is operating at CERN since more than a decade, with the aim of providing new, high accuracy and high resolution neutron cross-sections. Thanks to the features of the neutron beam, a rich experimental program relevant to nuclear technology has been carried out so far. The program will be further expanded in the near future, thanks in particular to a new high-flux experimental area, now under construction