Neste trabalho foram estudados os níveis excitados do 193Ir produzidos a partir do decaimento β do 193Os (T1/2 ~ 30h). Para a obtenção das amostras radioativas, ~ 5mg de Ósmio metálico (99% enriquecido em 192Os) foram irradiados no reator IEA-R1, sob um fluxo de nêutrons da ordem de 1012cm2 s1 e depois analisadas, empregando-se a técnica de espectroscopia γ simples (unidimensional) com espectrômetro γ de alta resolução, bem como as técnicas de espectroscopia de coincidência γγ e de correlação angular direcional γγ (θ) usando um sistema de aquisição multiparamétrica composto por 4 detectores HPGe. A partir destes dados, foi possível adicionar 28 transições a este esquema de decaimento, 11 das quais já eram conhecidas de outros estudos envolvendo reações nucleares, além de 17 observadas pela primeira vez. Também foram acrescentados 8 níveis excitados ao esquema de decaimento, sendo 3 conhecidos por outras reações e 5 completamente novos. Além disso, foi possível confirmar a suspeita encontrada na literatura de que os níveis a 848,93keV e 849,093keV são o mesmo, além de confirmar a existência de um nível excitado a 806,9keV. A análise de correlação angular direcional permitiu a definição do spin de do nível excitado a 874kev (5/2+), além de propor uma probabilidade de 79% do nível a 1078keV ter spin 5/2, e de restringir as possibilidades de spin para o nível novo a 960keV para duas (1/2 ou 3/2). Também foi possível determinar a razão de mistura multipolar (δLn+1/Ln) para 43 transições, sendo 19 pela primeira vez e praticamente todas as restantes com precisão melhor que a encontrada na literatura. Finalmente, foi feita uma tentativa de compreender o núcleo através de um modelo teórico, o qual reproduziu muito bem o estado fundamental e os dois primeiros estados excitados do 193Ir. / In this work, the excited levels of 193Ir populated by the β decay of 193Os (T1/2 30h) were investigated. For that purpose, 5mg samples of 99%-enriched 192Os were irradiated under a thermal neutron flux of 1012s1 and then analysed both using single gamma spectroscopy and a 4-detector multiparametric acquisition facility, which provided data for both a γγ coincidence analysis and a directional angular correlation γγ (θ) study. From these data, 28 transitions were added to this decay scheme, 11 of which were previously known from nuclear reactions and 17 observed for the first time. Eight excited levels were also added to the decay scheme, 3 of which were known from nuclear reaction studies the remaining 5 are suggested for the first time. Moreover, it was possible to confirm suspicions found in reference that the levels at 848.93keV and 849.093keV are indeed the same; it was also possible to confirm the existence of an excited level at 806.9keV, which had been inferred, but not experimentally confirmed in β decay studies to date. The angular correlation analysis allowed for the definition of the spin of the excited level at 874keV as 5/2+; moreover, the results showed a 79% probability that the spin of the 1078keV level is 5/2, and also restricted the spin possibilities for the new excited level at 960keV to two values (1/2 or 3/2). It was also possible to measure the multipolarity mixing ratio (δLn+1/Ln) for 43 transitions 19 of them for the first time and most of the others with a better precision than previously known. Finally, an attempt was made to understand the low-lying levels structure for this nucleus using a theoretical model, which reproduced the ground state and the two lowest-lying excited levels in 193Ir.

L’observation de la double désintégration bêta sans neutrinos (0ν2β) impliquerait la violation de la conservation du numéro leptonique, signe d’une nouvelle physique au-delà du Modèle Standard, et permettrait d’établir la nature de Majorana des neutrinos. Les bolomètres scintillants cryogéniques sont parmi les détecteurs les plus prometteurs pour rechercher ce processus nucléaire extrêmement rare dans des noyaux qui sont théoriquement entre les plus favorables.Des scintillateurs de ZnMoO₄ ayant une masse de ∼ 0.3 kg, ainsi que des cristaux de Zn¹⁰⁰ MoO₄ enrichi dans l’isotope ¹⁰⁰Mo, ont été produits pour la première fois en utilisant la technique de Czochralski à faible gradient thermique. Les propriétés optiques et de luminescence des cristaux produits ont été étudiées pour évaluer le progrès de la qualité de la croissance des cristaux. Des tests à basse température avec un scintillateur de 313 g de ZnMoO₄et deux scintillateurs de Zn¹⁰⁰ MoO₄ enrichis ont été réalisées en surface au Centre de Sciences Nucléaires et de Sciences de la Matière. On a aussi mené des mesures à faible fond radioactif avec trois cristaux de ZnMoO₄ naturels et deux détecteurs enrichis, installés dans le setup d’ EDELWEISS au Laboratoire Souterrain de Modane.Pour optimiser la collecte de la lumière dans des bolomètres scintillants cryogénique de ZnMoO₄, nous avons simulé par une méthode Monte Carlo la collecte des photons de scintillation dans un module de détection pour différentes géométries, en utilisant le logiciel GEANT4. La réponse à la désintégration 2ν2β de ¹⁰⁰Mo a été simulée pour des détecteurs enrichis de Zn¹⁰⁰ MoO₄ avec forme et masse différente, avec le but de comprendre la structure des spectres 2ν2β en fonctionne de la forme des cristaux. Nous avons simulé aussi la performance de 48 cristaux de Zn¹⁰⁰ MoO₄ ayant une taille de Ø60 × 40 mm et installés dans le cryostat d’EDELWEISS. La contribution au fond de la contamination radioactive interne des cristaux, l’activation cosmogénique et la contamination radioactive du setup ont été simulées.Tenant compte de la modeste résolution temporelle des bolomètres à basse température, nous avons également étudié la contribution au fond à l'énergie Q₂β déterminé par des coïncidences aléatoires de signaux, en particulier du à la décroissance 2ν2β, qui est l'une des sources de fond les plus dangereuses dans les bolomètres cryogéniques. Des méthodes pour le rejet d’événements coïncidant par hasard ont été développées et comparées. Nous avons également analysé la dépendance de l'efficacité de rejet à l’égard des performances du détecteur cryogénique. / Observation of neutrinoless double beta (0ν2β) decay would imply the violation of lepton number conservation and definitely new physics beyond the Standard Model, establishing the Majorana nature of neutrinos. Cryogenic scintillating bolometers look the most promising detectors to search for this extremely rare nuclear process in a few theoretically the most favorable nuclei.ZnMoO₄ scintillators with a mass of ∼ 0.3 kg, as well as Zn¹⁰⁰ MoO₄ crystals enriched in the isotope ¹⁰⁰Mo were produced for the first time by using the low-thermal-gradient Czochralski technique. The optical and luminescent properties of the produced crystals were studied to estimate the progress in crystal growth quality. The low-temperature tests with a 313 g ZnMoO₄ scintillator and two enriched Zn¹⁰⁰ MoO₄ were performed aboveground in the Centre de Sciences Nucléaires et de Sciences de la Matière. The low background measurements with a three ZnMoO₄ and two enriched detectors installed in the EDELWEISS set-up at the Laboratoire Souterrain de Modane were carried out.To optimize the light collection in ZnMoO₄ cryogenic scintillating bolometers, we have simulated the collection of scintillation photons in a detector module for different geometries by Monte Carlo method using the GEANT4 package. Response to the 2ν2β decay of ¹⁰⁰Mo was simulated for the enriched Zn¹⁰⁰ MoO₄ detectors of different shape and mass to understand the dependence of 2ν2β decay spectra on crystal shape. We have simulated 48 Zn¹⁰⁰ MoO₄ crystals with a size of Ø60 × 40 mm installed in the EDELWEISS cryostat. The contribution to background from the internal radioactive contamination of the crystals, cosmogenic activation and radioactive contamination of the set-up were simulated.Taking into account the poor time resolution of the low temperature bolometers, we also studied contribution to background at the Q₂β energy of random coincidences of signals, in particular of 2ν2β decay, which is one of the most valuable sources of background in cryogenic bolometers. Methods of the randomly coinciding events rejection were developed and compared. We have also analyzed dependence of the rejection efficiency on a cryogenic detector performance.

Neste trabalho foram estudados os níveis excitados do 193Ir produzidos a partir do decaimento β do 193Os (T1/2 ~ 30h). Para a obtenção das amostras radioativas, ~ 5mg de Ósmio metálico (99% enriquecido em 192Os) foram irradiados no reator IEA-R1, sob um fluxo de nêutrons da ordem de 1012cm2 s1 e depois analisadas, empregando-se a técnica de espectroscopia γ simples (unidimensional) com espectrômetro γ de alta resolução, bem como as técnicas de espectroscopia de coincidência γγ e de correlação angular direcional γγ (θ) usando um sistema de aquisição multiparamétrica composto por 4 detectores HPGe. A partir destes dados, foi possível adicionar 28 transições a este esquema de decaimento, 11 das quais já eram conhecidas de outros estudos envolvendo reações nucleares, além de 17 observadas pela primeira vez. Também foram acrescentados 8 níveis excitados ao esquema de decaimento, sendo 3 conhecidos por outras reações e 5 completamente novos. Além disso, foi possível confirmar a suspeita encontrada na literatura de que os níveis a 848,93keV e 849,093keV são o mesmo, além de confirmar a existência de um nível excitado a 806,9keV. A análise de correlação angular direcional permitiu a definição do spin de do nível excitado a 874kev (5/2+), além de propor uma probabilidade de 79% do nível a 1078keV ter spin 5/2, e de restringir as possibilidades de spin para o nível novo a 960keV para duas (1/2 ou 3/2). Também foi possível determinar a razão de mistura multipolar (δLn+1/Ln) para 43 transições, sendo 19 pela primeira vez e praticamente todas as restantes com precisão melhor que a encontrada na literatura. Finalmente, foi feita uma tentativa de compreender o núcleo através de um modelo teórico, o qual reproduziu muito bem o estado fundamental e os dois primeiros estados excitados do 193Ir. / In this work, the excited levels of 193Ir populated by the β decay of 193Os (T1/2 30h) were investigated. For that purpose, 5mg samples of 99%-enriched 192Os were irradiated under a thermal neutron flux of 1012s1 and then analysed both using single gamma spectroscopy and a 4-detector multiparametric acquisition facility, which provided data for both a γγ coincidence analysis and a directional angular correlation γγ (θ) study. From these data, 28 transitions were added to this decay scheme, 11 of which were previously known from nuclear reactions and 17 observed for the first time. Eight excited levels were also added to the decay scheme, 3 of which were known from nuclear reaction studies the remaining 5 are suggested for the first time. Moreover, it was possible to confirm suspicions found in reference that the levels at 848.93keV and 849.093keV are indeed the same; it was also possible to confirm the existence of an excited level at 806.9keV, which had been inferred, but not experimentally confirmed in β decay studies to date. The angular correlation analysis allowed for the definition of the spin of the excited level at 874keV as 5/2+; moreover, the results showed a 79% probability that the spin of the 1078keV level is 5/2, and also restricted the spin possibilities for the new excited level at 960keV to two values (1/2 or 3/2). It was also possible to measure the multipolarity mixing ratio (δLn+1/Ln) for 43 transitions 19 of them for the first time and most of the others with a better precision than previously known. Finally, an attempt was made to understand the low-lying levels structure for this nucleus using a theoretical model, which reproduced the ground state and the two lowest-lying excited levels in 193Ir.

The UCNA Experiment at the Los Alamos Neutron Science Center (LANSCE) is the first measurement of the β-decay asymmetry parameter A0 using polarized ultracold neutrons (UCN). A0 , which represents the parity-violating angular correlation between the direction of the initial neutron spin and the emitted decay electron’s momentum, determines λ = gA /gV , the ratio of the weak axial-vector and vector coupling constants. A high-precision determination of λ is important for weak interaction physics, and when combined with the neutron lifetime it permits an extraction of the CKM matrix element Vud solely from neutron decay. At LANSCE, UCN are produced in a pulsed, spallation driven solid deuterium source and then polarized via transport through a 7 T magnetic field. Their spins can then be flipped via transport through an Adiabatic Fast Passage spin flipper located in a low-field-gradient 1 T field region prior to transport to a decay storage volume situated within a 1 T solenoidal spectrometer. Electron detector packages located at each end of the spectrometer provide for the measurement of decay electrons. Previous UCNA results (based on data collected in 2010 and earlier) were limited by systematic uncertainties, in particular those from the UCN polarization, calibration of the electron energy, electron backscattering, and angular acceptance of events. This dissertation will present a background of neutron decay, an overview of the UCNA Experiment, followed by a detailed report on the entire analysis process for data acquired during run periods in 2011-2012 and 2012-2013.

Free neutron and nuclear beta decay spectroscopy serves as a robust laboratory for investigations of the Standard Model of Particle Physics. Observables such as decay product angular correlations and energy spectra overconstrain the Standard Model and serve as a sensitive probe for Beyond the Standard Model physics. Improved measurement of these quantities is necessary to complement the TeV scale physics being conducted at the Large Hadron Collider. The UCNB, 45Ca, and Nab experiments aim to improve upon existing measurements of free neutron decay angular correlations and set new limits in the search for exotic couplings in beta decay. To achieve these experimental goals, a highly-pixelated, thick silicon detector with a 100 nm entrance window has been developed for precision beta spectroscopy and the direct detection of 30 keV beta decay protons. The detector has been characterized for its performance in energy reconstruction and particle arrival time determination. A Monte Carlo simulation of signal formation in the silicon detector and propagation through the electronics chain has been written to develop optimal signal analysis algorithms for minimally biased energy and timing extraction. A tagged-electron timing test has been proposed and investigated as a means to assess the validity of these Monte Carlo efforts. A universal platform for data acquisition (DAQ) has been designed and implemented in National Instrument's PXIe-5171R digitizer/FPGA hardware. The DAQ retains a ring buffer of the most recent 400 ms of data in all 256 channels, so that a waveform trace can be returned from any combination of pixels and resolution for complete energy reconstruction. Low-threshold triggers on individual channels were implemented in FPGA as a generic piecewise-polynomial filter for universal, real-time digital signal processing, which allows for arbitrary filter implementation on a pixel-by-pixel basis. This system is universal in the sense that it has complete flexible, complex, and debuggable triggering at both the pixel and global level without recompiling the firmware. The culmination of this work is a system capable of a 10 keV trigger threshold, 3 keV resolution, and maximum 300 ps arrival time systematic, even in the presence of large amplitude noise components.

There is an intense interest in the availability of radioactive isotopes that could be developed into nuclear batteries. Promethium-147 is one of the isotopes of interest for use in nuclear batteries as well as in other compact low power applications. Pm-147 is a pure beta (β-) emitter with a half-life of 2.62 years. For this research, Pm-147 was produced from enriched Nd-146 via the neutron capture method in the Hydraulic Tube facility of HFIR at the Oak Ridge National Laboratory. Radioisotopic impurities produced via the neutron capture method have significant effects on its potential final use for nuclear battery applications. This research provides information on the co-production levels of the radioisotopic impurities in the samples containing Pm-147 and their effects on the required shielding. Gamma spectroscopy analysis served as the primary method in the evaluation of the impurities. Previous research had identified the presence of these impurities but it had not studied them in detail.

<p>An experimental study of the two-neutrino double-beta (2&nu;&beta;&beta;) decay of <super>150</super>Nd to various excited final states of <super>150</super>Sm was performed at Triangle Universities Nuclear Laboratory (TUNL). Such data provide important checks for theoretical models used to predict 0&nu;&beta;&beta; decay half lives.</p> <p>The measurement was performed at the recently established Kimballton Underground Research Facility (KURF) in Ripplemeade, Virginia using the TUNL-ITEP double-beta decay setup. In this setup, two high-purity germanium detectors were operated in coincidence to detect the deexcitation gamma rays of the daughter nucleus. This coincidence technique, along with the location underground, provides a considerable reduction in background in the regions of interest.</p> <p>This study yields the first results from KURF and the first detection of the</p> <p>coincidence gamma rays from the 0<super>+</super>₁ excited state of <super>150</super>Sm. These gamma rays</p> <p>have energies of 334.0 keV and 406.5 keV, and are emitted in coincidence through a 0<super>+</super>₁&rarr;2<super>+</super>₁&rarr;0<super>+</super>_gs transition. The enriched Nd₂O₃ sample obtained from Oak Ridge</p> <p>National Laboratory consists of 40.13 g <super>150</sub>Nd. This sample was observed for 391 days, producing 29 raw events in the region of interest. This count rate gives a half life of T_1/2 = (0.72<super>+0.36</super>_&#8722;0.18 &plusmn; 0.04(syst.)) &times; 10<super>20</super> years, which agrees within error with</p> <p>another recent measurement, in which only the single deexcitation gamma rays were detected (i.e., no coincidence was employed). Lower limits were also obtained for decays to higher excited final states.</p> / Dissertation

The N=88 nuclei lie in a transitional region of the nuclear chart. Collective structure and nuclear deformation for this region is commonly occurring. Previously, some of the nuclei having 88 neutrons have been well studied, e.g., 148Nd, 150Sm, 152Gd, 154Dy; however, 156Er has not. To be able to understand the nuclei in this region one needs to extract all the systematics of these deformed nuclei and the relations between them. The structure of 156Er is the main focus in this thesis and the work seeks understanding of the N=88 nuclei and systematics among them. To accomplish this task, 156Tm to 156Er beta decay was studied. Many new levels and gamma transitions have been added to the existing scheme. The significance for detailed decay scheme studies far from stability is also discussed.

There is an intense interest in the availability of radioactive isotopes that could be developed into nuclear batteries. Promethium-147 is one of the isotopes of interest for use in nuclear batteries as well as in other compact low power applications. Pm-147 is a pure beta (β-) emitter with a half-life of 2.62 years. For this research, Pm-147 was produced from enriched Nd-146 via the neutron capture method in the Hydraulic Tube facility of HFIR at the Oak Ridge National Laboratory. Radioisotopic impurities produced via the neutron capture method have significant effects on its potential final use for nuclear battery applications. This research provides information on the co-production levels of the radioisotopic impurities in the samples containing Pm-147 and their effects on the required shielding. Gamma spectroscopy analysis served as the primary method in the evaluation of the impurities. Previous research had identified the presence of these impurities but it had not studied them in detail.

High-precision half-life and branching-ratio measurements for the superallowed beta+ emitter 26Alm were performed at the TRIUMF-ISAC radioactive ion beam facility located in Vancouver, Canada. The branching ratio measurement was performed with the 8pi Spectrometer, an array of 20 high-purity germanium detectors, in conjunction with SCEPTAR, a plastic scintillator array used to detect the emitted beta particles. An upper limit of <= 12 ppm at 90% confidence level was found for the second forbidden beta + decay of 26Alm to the first 2+ state at 1809 keV in 26Mg. An inclusive upper limit of <= 15 ppm at 90% confidence level was found when considering all possible non-analogue beta +/EC decay branches of 26Alm, resulting in a superallowed branching ratio of 100.0000+0−0.0015%. The half-life measurement was performed using a 4pi continuous-flow gas proportional counter and fast tape transport system. The resulting value for the 26Alm half-life, T1/2 = 6.34654(76) s, is consistent with, but 2.5 times more precise than, the previous world average, and represents the single most precisely measured half-life of any superallowed emitting nucleus to date. Combining these results with world-average Q-value measurements yields a superallowed beta -decay ft value of 3037.58(60) s, the most precisely determined ft value for any superallowed emitting nucleus to date. Combined with the small, and precisely quoted, theoretical isospin-symmetry-breaking corrections for this nucleus, the corrected Ft value for 26Alm of 3073.1(12) s is also the most precisely determined for any superallowed emitter by nearly a factor of two and now rivals the precision of all the other 12 precisely measured superallowed beta decays combined. The high-precision experimental ft value for 26Alm superallowed decay reported here provides a new benchmark to refine theoretical models of isospin-symmetry-breaking effects in superallowed Fermi beta decays.