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

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.

<p>Two separate experimental searches for second-order weak nuclear decays to excited final states were conducted. Both experiments were carried out at the Kimballton Underground Research Facility to provide shielding from cosmic rays. The first search is for the two-neutrino double-beta decay of 96Zr to excited final states of the daughter nucleus, 96Mo. As a by product of this experiment, the beta decay of 96Zr was also investigated. Two coaxial high-purity germanium detectors were used in coincidence to detect gamma rays produced by the daughter nucleus as it de-excited to the ground state. After collecting 1.92 years of data with 17.91 g of enriched 96Zr, half-life limits at the level of 10^20 yr were produced. Measurements of this decay are important to test neutrinoless double-beta decay nuclear matrix element calculations, which are necessary to extract the neutrino mass from a measurement of the neutrinoless double-beta decay half-life. </p><p>The second experiment is a search for the resonantly-enhanced neutrinoless double-electron capture decay of 156Dy to excited states in 156Gd. Double-electron capture is a possible experimental alternative to neutrinoless-double beta decay, which could distinguish the Dirac or Majorana nature of the neutrino. Two clover high-purity germanium detectors were used in coincidence to investigate the decay. A 213.5 mg enriched 156Dy sample was observed for 0.635 year, producing half-life limits of 10^17 yr. The limits produced by both of these experiments are currently the most stringent limits available for these decays.</p> / Dissertation

CP violation is an important condition to explain the preponderance of baryons in our universe, yet the available CP violation in the Standard Model (SM) via the so-called Cabibbo-Kobayashi-Maskawa mechanism seems to not provide enough CP violation. Thus searching for new sources of CP violation is one of the central tasks of modern physics. In this thesis, we focus on a new possible source of CP violation which generates triple-product correlations in momenta which can appear in neutron and nuclear radiative β decay. We show that at low energies such a CP violating correlation may arise from the exotic coupling of nucleon, photon and neutrino that was proposed by Harvey, Hill, and Hill (HHH). One specialty of such an exotic HHH coupling is that it does not generate the well-known CP-violating terms such as ``D-term'', ``R-term'', and neutron electric dipole moment, in which particle's spins play critical role. We show that such a new HHH-induced CP violating effect is proportional to the imaginary part of c5gv, where gv is the vector coupling constant in neutron and nuclear β decay, and c5 is the phenomenological coupling constant that appears in chiral perturbation theory at O(M-2) with M referring to the nucleon or nuclear mass. We consider a possible non-Abelian hidden sector model, which is beyond the SM and may yield a nontrivial Im(c5). The available bounds on both Im(c5) and Im(gv) are considered, and a better limit on Im(c5) can come from a direct measurement in radiative beta decay. We calculate the competitive effect that arises from the general parameterization of the weak interaction that was proposed by Lee and Yang in 1956. We also show that in the proposed measurements, the CP-violating effect can be mimicked by the SM via final-state interactions (FSI). For a better determination of the bound of Im(c5), we consider the FSI-induced mimicking effect in full detail in O(α) as well as in leading recoil order. To face ongoing precision measurements of neutron radiative β decay of up to 1% relative error, we sharpen our calculations of the CP conserving pieces of neutron radiative β decay by considering the largest contributions in O(α2): the final-state Coulomb corrections as well as the contributions from two-photon radiation.

While neutrino oscillations indicate that neutrino flavors mix and that neutrinos have mass, they do not supply information on the absolute mass scale of the three flavors of neutrinos. Currently, the only viable way to determine this mass scale is through the observation of the theoretically predicted process of neutrinoless double-beta decay (0νββ). This yet-to-be-observed decay process is speculated to occur in a handful of nuclei and has predicted half-lives greater than 10²⁵ years. Observation of 0νββ is the goal of several large-scale, multinational efforts and consists of detecting a sharp peak in the summed β energies at the Q-value of the reaction. An exceptional candidate for the observation of 0νββ is ⁷⁶Ge, which offers an excellent combination of capabilities and sensitivities, and two such collaborations, MAJORANA and GERDA, propose tonne-scale experiments that have already begun initial phases using a fraction of the material. The absolute scale of the neutrino masses hinges on a matrix element, which depends on the ground-state wave functions for both the parent (⁷⁶Ge) and daughter (⁷⁶Se) nuclei in the 0νββ decay and can only be calculated from nuclear structure models. Efforts to provide information on the applicability of these models have been undertaken at the University of Kentucky Accelerator Laboratory using gamma-ray spectroscopy following inelastic scattering reactions with monoenergetic, accelerator-produced fast neutrons. Information on new energy levels and transitions, spin and parity assignments, lifetimes, multipole mixing ratios, and transition probabilities have been determined for ⁷⁶Se, the daughter of ⁷⁶Ge 0νββ, up to 3.0 MeV. Additionally, inaccuracies in the accepted level schemes have been addressed. Observation of 0νββ requires precise knowledge of potential contributors to background within the region of interest, i.e., approximately 2039 keV for ⁷⁶Ge. In addition to backgrounds resulting from surrounding materials in the experimental setup, ⁷⁶Ge has a previously observed 3952-keV level with a de-exciting 2040-keV γ ray. This γ ray constitutes a potential background for 0νββ searches, if this level is excited. The cross sections for this level and, subsequently, for the 2040-keV γ ray has been determined in the range from 4 to 5 MeV.