National Repository of Grey Literature 23 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Analysis of photon data from neutron capture on 170Tm
Špringlová, Kamila ; Krtička, Milan (advisor) ; Vorobel, Vít (referee)
The subject of this thesis is to study modes of γ decay of 170 Tm; knowledge of quan- tities describing γ decay form an important step in understanding an atomic nucleus. A description of γ decay of excited states of a heavy atomic nucleus above excitation energy of a few MeV is usually performed within the statistical model using the level density and photon strength functions. There have been numerous attempts to introduce models for these quantities, however, there are still contradictions with experimental data. This thesis focuses on analyzing experimental data from γ decay of excited 170 Tm nucleus formed by a slow neutron capture on 169 Tm. Specifically, the so-called sum-energy and multistep γ cascade spectra were prepared and the impact of several parameters used in the data processing was tested. The γ rays emitted from the radiative neutron capture were detected with a highly-segmented high-efficiency scintillation detector DANCE at Los Alamos National Laboratory. The full analysis is then completed by comparing the experimental data with predictions based on various level density and photon strength functions models. The whole process is very complex and its first step is a conversion of raw data to the form that can be compared with simulations, which is the subject of this thesis. 1
Two- neutrino double beta decay of 150Nd in the NEMO-3 experiment and scintillator characterization for the SUPER NEMO
Žukauskas, Aivaras ; Vorobel, Vít (advisor) ; Lokajíček, Miloš (referee) ; Wagner, Vladimír (referee)
The half-life of two-neutrino double beta decay of 150 Nd has been measured with data taken by the NEMO-3 experiment at the Modane Underground Laboratory. Using 1918.5 days of data recorded with 36.55 g of 150 Nd the half-life of this process is measured to be T2ν 1/2 = (8.99 ± 0.18 (stat.) ± 0.71 (syst.)) × 1018 y. SuperNEMO is the successor to NEMO-3 and will be one of the next generation of 0νββ experiments. It aims to measure 82 Se with an half-life sensitivity of 1026 yr corresponding to ⟨mββ⟩ < 50 - 100 meV. In order to achieve this target, a testing apparatus for the scintillator characterization has been developed and 140 scintillator blocks were characterized for the calorimeter of the SuperNEMO. It was determined that none of the blocks violate defined criteria of uniformity (± 3% for the energy resolution at 1 MeV) nor the criteria of energy resolution (< 16% at 1 MeV). The average uniformity of the blocks was found to be 0.7% and the average energy resolution of these blocks is 12% at 1 MeV. However, it was discovered during the visual tests that 23 out of 140 blocks contain more than 20 visible dust specks, thus alarming the possible contamination of these blocks with the natural radioactive isotopes.
Precise measurement of the electron antineutrino oscillation
Pěč, Viktor ; Vorobel, Vít (advisor) ; Trávníček, Petr (referee) ; Vénos, Drahoslav (referee)
The Daya Bay experiment is designed to precisely measure short-baseline disappearance of reactor antineutrinos from reactor cores at the Daya Bay nuclear power plant complex in the Guangdong Province of China. It pre- sented the most precise measurements of oscillation parameters sin2 2θ13 = 0.084 ± 0.005 and |∆m2 ee| = (2.42 ± 0.11) × 10−3 eV2 . Background to the antineutrino signals is mainly created by cosmic muons and is effectively suppressed by use of water Cherenkov and RPC muon detectors. This thesis describe testing of RPC detectors prior to their installation at the experi- mental site. Part of the cosmic muons stop in the experiment's antineutrino detectors, and they decay or are captured by 12 C producing 12 B. Isotope 12 B contribute to accidental background. Rates of muon decays in the detectors are estimated in the thesis. The experiment can register electron antineutri- nos from supernova with expected signals around 20 MeV. Energy scale of the detectors at 53 MeV is determined.
Monitoring of the energy scale in the KATRIN neutrino experiment
Slezák, Martin ; Vénos, Drahoslav (advisor) ; Štekl, Ivan (referee) ; Vorobel, Vít (referee)
The question of the absolute mass scale of neutrinos is of particular interest for particle physics, astrophysics, and cosmology. The KATRIN experiment (KArlsruhe TRItium Neutrino experiment) aims to address the effective electron antineutrino mass from the shape of the tritium β-spectrum with an unprecedented sensitivity of 0.2 eV/c2 . One of the major systematic effects concerns the experimental energy scale, which has to be stable at the level of only a few parts in a million. For its calibration and monitoring the monoener- getic electrons emitted in the internal conversion of γ-transition of the metastable isotope 83m Kr will be extensively applied. The aim of this thesis is to address the problem of KA- TRIN energy scale distortions and its monitoring in detail. The source of electrons based on 83m Kr embedded in a solid as well as the source based on gaseous 83m Kr are studied. Based on the experimental results an approach for the continuous stability monitoring is proposed. 1
Zdroj monoenergetických elektronů pro monitorování spektrometru v neutrinovém experimentu KATRIN
Slezák, Martin ; Vénos, Drahoslav (advisor) ; Vorobel, Vít (referee)
The international project KATRIN (KArlsruhe TRItium Neutrino experiment) is a next- generation tritium beta decay experiment. It is designed to measure the electron antineutrino mass by means of a unique electron spectrometer with sensitivity of 0.2 eV/c2 . This is an improvement of one order of magnitude over the last results. Important part of the measurement will rest in continuous precise monitoring of high voltage of the KATRIN main spectrometer. The monitoring will be done by means of conversion electrons emitted from a solid source based on 83 Rb decay. Properties of several of these sources are studied in this thesis by means of the semiconductor gamma-ray spectroscopy. Firstly, measurement of precise energy of the 9.4 keV nuclear transition observed in 83 Rb decay, from which the energy of conversion electrons is derived, is reported. Secondly, measurement of activity distribution of the solid sources by means of the Timepix detector is described. Finally, a report on measurement of retention of 83 Rb decay product, the isomeric state 83m Kr, in the solid sources is given.
Studium urychlování vysokoenergetických částic v extragalaktických objektech
Štefánik, Stanislav ; Nosek, Dalibor (advisor) ; Vorobel, Vít (referee)
Title: Study of Cosmic-Ray Acceleration in Extragalactic Objects Author: Stanislav tefnik Department: Institute of Particle and Nuclear Physics Supervisor: RNDr. Dalibor Nosek, Dr. Abstract: This thesis deals with production processes of cosmic γ-rays in astro- physical objects and methods of their detection. Possible interactions leading to the emission of high energy γ-rays in the active galaxy Centaurus A are discussed in this context. Cherenkov Telescope Array is presented as a new experiment fo- cused on the detection of air showers initiated by cosmic γ-rays. Cherenkov light of air showers is studied in the simulations done by CORSIKA simulation tool. Method of data analysis within the framework of Cherenkov telescopes is descri- bed and performed on the dataset of the active galaxy PKS 2155-304. The results include statistical tests of γ-ray source presence and its time variability. Keywords: Cosmic rays, gamma rays, astroparticle physics, high energy astro- physics, acceleration, CTA experiment

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