beta-delayed proton decays of Sm-133 and Yb-149

Sm-133 was produced via fusion evaporation in the reaction Ca-40+Ru-96. Its P-delayed proton decay was studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of 133Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities Of Sm-133 were assigned to be 5/2(+) and 1/2(-), which is reconciled with our published simple (EC+beta(+)) decay scheme Of Sm-113 in 2001. In addition, our experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J., 2001, A12: 1-4 was also analyzed by using the same method. The spin and parity of Yb-149 was assigned to be 1/2-.

beta-delayed proton decays and spin assignments for Sm-133 and Yb-149

The proton-rich isotope Sm-133 was produced via the fusion evaporation reaction Ca-40 + Ru-96. Its beta-delayed proton decay was studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nucleus were determined. Comparing the observed beta-delayed proton branching ratios with statistical model calculations, the best agreement is found assuming that only one level with the spin of 3/2 in Sm-133 decays or two levels with the spins of 1/2 and 5/2 decay with similar half-lives. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated using the Woods-Saxon-Strutinsky method, which suggests a 1/2-ground state and a 5/2(+) isomer with an excitation energy of 120 keV. Therefore, the simple(EC+beta(+)) decay scheme of Sm-133 in Eur. Phys. J.A 11,277(2001) has been revised. In addition, our previous experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J. A 12,1 ( 2 0 0 1) was also analyzed using the same method. The spin-parity of Yb-149 is suggested to be 1/2(-).

~(153)Er, ~(157)Yb(EC+#beta#~+)衰变纲图的首次建立

用蒸发中子反应产生~(157)Tb和~(153)Er，收集活性样品，作x, #gamma# 单谱及符合谱测量，对~(157)Yb和~(153)Er的(EC+#beta#~+)衰变进行了研究，给出了~(157)Yb及~(153)Er的衰变纲图，其中~(157)Yb的衰变纲图包括25条新#gamma#射线，分析~(157)Yb的衰变纲图，~(153)Er的衰变纲图包括15条#gamma#射线，并指定出~(153)Er半衰变期值，该值与文献给出值符合得很好。指定了~(153)Er的衰变纲图中能级状况

Messung von Q beta-Werten neutronenreicher Tc- bis Pd-Isotope im Massenbereich A=110 bis A=117

In der vorliegenden Arbeit wurden zwölf Q(beta)-Werte von beta-instabilen Pd, Ru, Rh und Tc-Isotopen gemessen. Der betrachtete Massenbereich A=110 bis A=117 liegt am Rande des bekannten Gebiets der Nuklidkarte und umfasst sehr neutronenreiche kurzlebige Isotope dieser Elemente, die sich durch geringe Spalthäufigkeit auszeichnen. Durch die geringen (Spalt-)Häufigkeiten dieser Nuklide liegen kaum Daten vor, teilweise auch nicht über die Niveauschemata. Es ist daher notwendig, eine protoneninduzierte Spaltungsreaktion zur Darstellung dieser Isotope zu verwenden und die Spaltprodukte innerhalb kürzester Zeit für die Messung nach Massen aufzutrennen, wie dies am IGISOL in Jyväskylä/Finnland geschieht. Die aufgebaute Apparatur zur beta,gamma,X-Koinzidenz erlaubt es, während ein und desselben Experiments neben der Messung der Q(beta)-Werte gleichzeitig gamma,X-Koinzidenzen auszuwerten, die die benötigten Grundinformationen für die Q(beta)-Bestimmung über die beta,gamma-Koinzidenzen liefern. Es können somit nicht nur Q(beta)-Werte von Nukliden mit bereits bekannten Niveauschemata ermittelt, sondern auch erfolgreich Nuklide mit unvollständigen Niveauschemata einer ersten Messung unterzogen werden. Umgekehrt können beta,gamma-Koinzidenzdaten weitere Informationen zum Aufbau neuer Niveauschemata liefern. Mit Hilfe der beschriebenen Koinzidenzmessung konnten zwölf Q(beta)-Werte von sehr neutronenreichen Pd- bis Tc-Isotopen gemessen und daraus die Kernmassen, Massenüberschüsse und Neutronen-Separationsenergien bestimmt werden. Von diesen wurden acht Werte erstmalig bestimmt, ein weiterer Wert konnte bestätigt sowie die Fehler von drei weiteren Werten um den Faktor Zehn verringert werden. Die gewonnenen Daten sind von Interesse für die Beurteilung von Kernmassenmodellen und gehen ebenso in Modellrechnungen der nuklearen Astrophysik ein.

The electron antineutrino angular correlation coefficient a in free neutron decay: Testing the standard model with the aSPECT-spectrometer

The beta-decay of free neutrons is a strongly over-determined process in the Standard Model (SM) of Particle Physics and is described by a multitude of observables. Some of those observables are sensitive to physics beyond the SM. For example, the correlation coefficients of the involved particles belong to them. The spectrometer aSPECT was designed to measure precisely the shape of the proton energy spectrum and to extract from it the electron anti-neutrino angular correlation coefficient "a". A first test period (2005/ 2006) showed the “proof-of-principles”. The limiting influence of uncontrollable background conditions in the spectrometer made it impossible to extract a reliable value for the coefficient "a" (publication: Baessler et al., 2008, Europhys. Journ. A, 38, p.17-26). A second measurement cycle (2007/ 2008) aimed to under-run the relative accuracy of previous experiments (Stratowa et al. (1978), Byrne et al. (2002)) da/a =5%. I performed the analysis of the data taken there which is the emphasis of this doctoral thesis. A central point are background studies. The systematic impact of background on a was reduced to da/a(syst.)=0.61 %. The statistical accuracy of the analyzed measurements is da/a(stat.)=1.4 %. Besides, saturation effects of the detector electronics were investigated which were initially observed. These turned out not to be correctable on a sufficient level. An applicable idea how to avoid the saturation effects will be discussed in the last chapter.

Aplicação do método de Monte Carlo no estudo da padronização de radionuclídeos com esquema de desintegração complexos em sistema de coincidencias 4-pi-beta-gama

Tese (Doutoramento)

Running neutrino mass from six dimensions

In the present talk, we will discuss a six dimensional mass generation for the neutrinos. The SM neutrinos live on a 3-brane and interact via a brane localised mass term with a Weyl singlet neutrino residing in all the six dimensions. We present the physical neutrino mass spectrum and show that the active neutrino mass and the KK masses have a logarithmic cut-off dependence at the tree level. This translates in to a renormalisation group running of n -masses above the KK compactification scale coming from classical effects without any SM particles in the spectrum.This could have effects in neutrinoless double beta decay experiments.

Discovery of non-zero neutrino mixing angle θ_13 using Daya Bay antineutrino detectors

The Daya Bay Reactor Antineutrino Experiment observed the disappearance of reactor $\bar{\nu}_e$ from six $2.9~GW_{th}$ reactor cores in Daya Bay, China. The Experiment consists of six functionally identical $\bar{\nu}_e$ detectors, which detect $\bar{\nu}_e$ by inverse beta decay using a total of about 120 metric tons of Gd-loaded liquid scintillator as the target volume. These $\bar{\nu}_e$ detectors were installed in three underground experimental halls, two near halls and one far hall, under the mountains near Daya Bay, with overburdens of 250 m.w.e, 265 m.w.e and 860 m.w.e. and flux-weighted baselines of 470 m, 576 m and 1648 m. A total of 90179 $\bar{\nu}_e$ candidates were observed in the six detectors over a period of 55 days, 57549 at the Daya Bay near site, 22169 at the Ling Ao near site and 10461 at the far site. By performing a rate-only analysis, the value of $sin^2 2\theta_{13}$ was determined to be $0.092 \pm 0.017$.

Towards more accurate and reliable predictions for nuclear applications

The need for nuclear data far from the valley of stability, for applications such as nuclear as- trophysics or future nuclear facilities, challenges the robustness as well as the predictive power of present nuclear models. Most of the nuclear data evaluation and prediction are still performed on the basis of phenomenological nuclear models. For the last decades, important progress has been achieved in funda- mental nuclear physics, making it now feasible to use more reliable, but also more complex microscopic or semi-microscopic models in the evaluation and prediction of nuclear data for practical applications. In the present contribution, the reliability and accuracy of recent nuclear theories are discussed for most of the relevant quantities needed to estimate reaction cross sections and beta-decay rates, namely nuclear masses, nuclear level densities, gamma-ray strength, fission properties and beta-strength functions. It is shown that nowadays, mean-field models can be tuned at the same level of accuracy as the phenomenological mod- els, renormalized on experimental data if needed, and therefore can replace the phenomenogical inputs in the prediction of nuclear data. While fundamental nuclear physicists keep on improving state-of-the-art models, e.g. within the shell model or ab initio models, nuclear applications could make use of their most recent results as quantitative constraints or guides to improve the predictions in energy or mass domain that will remain inaccessible experimentally.

Cement As a Waste Form for Nuclear Fission Products: The Case of 90Sr and Its Daughters

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of ⁹⁰Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that ⁹⁰Sr is stable when it substitutes the Ca²⁺ ions in C-S-H, and so is its daughter nucleus ⁹⁰Y after β-decay. Interestingly, ⁹⁰Zr, daughter of ⁹⁰Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for ⁹⁰Sr storage.