A position-sensitive microchannel plate (MCP) detector has been installed at the Canadian Penning Trap (CPT) mass spectrometer located at the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory in order to carry out Phase-Imaging Ion Cyclotron Resonance (PI-ICR) measurements. With this new measurement method, proof-of-principle mass measurements of five nuclei were made to a precision of $\delta m/m \approx 10^{-7}$. The PI-ICR results are found to be consistent with previous Time-of-Flight Ion Cyclotron Resonance (ToF-ICR) measurements. The content of this thesis covers the entire mass measurement process beginning with beam production at CARIBU through to ion detection at the CPT and a comparison of the ToF-ICR and PI-ICR measurement methods. The future of mass measurements at the CPT with this new technique will also be discussed. / May 2016

Magister Scientiae - MSc (Physics) / Electron-mediated nuclear plasma interactions (NPIs), such as Nuclear Excitation by Electron Capture (NEEC) or Transition (NEET), can have a signi cant impact on nuclear cross sections in High Energy Density Plasmas (HEDPs). HEDP environments are found in nuclear weapons tests, National Ignition Facility (NIF) shots and in the cosmos where nucleosynthesis takes place. This thesis explores the impact of NPIs on highly excited nuclei. This impact is understood to be more intense in highly-excited nuclei states in the quasi-contiuum which is populated by nuclear reactions prior to their decay by spontaneous -ray emission.

The ejecta following the collision and merging of two neutron stars (kilonova) are currently considered promising sites for nucleosynthesis of r-process elements. Since the observed kilonova in 2017, GW2017817, astrophysicists have been working to analyze the collected electromagnetic spectra, trying to identify r-process elements. However, a lack of fundamental atomic data has been holding the efforts back. Motivated by spectral modelling of kilonovae out of equilibrium, this project aims to create a tool that uses line lists of spectroscopic accuracy from the Vienna Atomic Line Database (VALD) to generate energy level lists automatically for any ion. VALD in particular is used because it has wavelengths accurate enough for line identification purposes. The resulting level lists are compared to equivalent level lists from the database managed by the National Institute for Standards and Technology (NIST), in order to both ensure that the tool worked, and identify discrepancies between the databases. A number of problems with the VALD data were identified, mostly resulting in duplicate and missing energy levels. Finally, we also test the data in computations of kilonova expansion opacities in a complete solar r-process abundance mixture. Further work is needed to evaluate how damaging these problems are when modelling kilonovae, and when necessary remedy said problems. / Ejektat från en kollision och sammanslagning av två neutronstjärnor (kilonova) betraktas som lovande platser för nukleosyntes av r-processämnena. Sedan den observerade kilonovan år 2017, GW2017817, har astrofysiker försökt analysera de insamlade elektromagnetiska spektrumen för att försöka identifiera r-processämnen. Denna analys har dock hindrats på grund av en brist på fundamental atomisk data. Motiverat av spektralmodellering av kilonovor utanför ekvilibrium, syftar detta projekt på att utveckla ett verktyg för att utifrån spektroskopiskt noggranna linjelistor från Vienna Atomic Line Database (VALD) gererera listor över energinivåer automatiskt för godtycklig jon. VALD används på grund av att den har våglänger som är noggranna nog för linjeidentifiering. De resulterande nivålistorna jämförs med motsvarande nivålistor från databasen som sköts av National Institute for Standards and Technology (NIST), detta för att dels säkerställa att verktyget fungerade, dels identifiera skillnader mellan databaserna. Ett antal problem med VALD identifierades, vilka oftast resulterade i dubbletter eller avsaknad av energinivåer. Slutligen testades datan i beräkningar av kilonova-expansionsopaciteter i en komplett solär r-process-ämnesblandning. Vidare arbete krävs för att evaluera hur skadliga dessa problem är för modellering av kilonovor, och vid behov åtgärda problemen.

Covariant density functional theory (CDFT) is one of the modern theoretical tools for the description of finite nuclei and neutron stars. Its performance is defined by underlying covariant energy density functionals (CEDFs) which depend on a number of parameters. Several investigations within the CDFT framework using the relativistic Hartree-Bogoliubov (RHB) approach are discussed in this dissertation. Statistical errors in ground state observables and single-particle properties of spherical even-even nuclei and their propagation to the limits of nuclear landscape have been investigated in the covariant energy density functionals with nonlinear density dependency. The parametric correlations are studied in different classes of CEDFs; the elimination of these correlations reduces the number of independent parameters to five or six without affecting the performance of CEDFs on a global scale. Moreover, this study reveals the need to include information on deformed nuclei for the improvement of fitting protocols. A new technique for incorporating deformed nuclei data into the fitting protocol is described. Different CEDFs are optimized using this approach, resulting in a significant improvement in the nuclear mass description. A systematic investigation of the ground state and fission properties of even-even actinides and superheavy nuclei with proton numbers Z = 90 - 120 located between the two-proton and two-neutron drip lines has been performed. These results provide a necessary theoretical input for the modeling of the nuclear astrophysical rapid neutron capture process (r-process) taking place in the mergers of neutron stars. The state-of-the-art CEDFs, namely, DD-PC1, DD-ME2, NL3*, and PC-PK1, are employed in this study. Theoretical systematic uncertainties in the physical observables and their evolution as a function of proton and neutron numbers have been quantified and their major sources have been identified. The extension of the nuclear landscape to hyperheavy nuclei is investigated. The transition from ellipsoidal-like nuclear shapes to toroidal shapes is crucial for the potential expansion of the nuclear landscape to hyperheavy nuclei. The physical reasons for the stability of toroidal nuclei in the Z ~ 134 region are discussed.

Penning trap mass spectrometry (PTMS) can be used to test the Standard Model (SM) and to answer the questions related to the origin and abundance of the elements in the universe. There are several facilities worldwide specialized in PTMS and some of them can measure the masses of isotopes with half-lives in the range of milliseconds. TRIUMF’s ion trap for atomic and nuclear science (TITAN) is one such facility. In mass measurement the precision is linearly proportional to the charge state of the ion of interest. To increase the charge state, ions are charge-bred using an electron beam ion trap (EBIT) at TITAN. However, the charge breeding process introduces an energy spread among the ions which adversely affects the precision of the mass measurement. To overcome this problem a cooler Penning trap (CPET) was designed, assembled and is now being tested off-line. This thesis presents the first systematic test results of CPET. We also present the result of the first Penning trap mass measurement of the isotope 24Al, which is five times more precise than the previous atomic mass evaluation (AME2012) value. The precise and accurate mass of 24Al is important for both astrophysics and for test of the standard model (SM). The resonance energy (E_r) calculated for the 23Mg(p,gamma)24Al reaction using the ground state mass of 24Al reported in this thesis shows a 2s deviation from the direct measurement. On the other hand, tests of the SM by evaluating f_t values using isospin T = 1 nuclides have reached a high precision level. Effort is now shifting towards the T = 2 nuclides, which are far from stability compared to their T = 1 counterparts. For this reason, the ground state masses of T = 2 nuclides and of their decay products are required to be known with high precision. 24Al is the daughter of one such nucleus, 24Si. The ground state mass of 24Al reported in this thesis will be useful to test the SM. / October 2016

>Magister Scientiae - MSc / Electron-mediated nuclear plasma interactions (NPIs), such as Nuclear Excitation by Electron Capture (NEEC) or Transition (NEET), can have a signi cant impact on nuclear cross sections in High Energy Density Plasmas (HEDPs). HEDP environments are found in nuclear weapons tests, National Ignition Facility (NIF) shots and in the cosmos where nucleosynthesis takes place. This thesis explores the impact of NPIs on highly excited nuclei. This impact is understood to be more intense in highly-excited nuclei states in the quasi-contiuum which is populated by nuclear reactions prior to their decay by spontaneous -ray emission. Attempts thus far have failed in measuring the NEEC process [1, 2], while NEET process has been observed experimentally [3, 4]. Direct observation of NPIs is hindered by the lack of a clear signature of their effect in HEDP environments. Hence this should test a new signature [5] for NPIs for highly-excited nuclei by investigating isomeric to ground state feeding from the isomeric state. An experiment was performed using the reactions 197Au(13C, 12C)198Au and 197Au(13C, 12C2n)196Au at Lawrence Berkeley National Laboratory in inverse kinematics with an 197Au beam of 8.5 MeV/u energy. Several measurements were performed with different target configurations. The activated foils were counted at the low-background counting facility of Lawrence Livermore National Laboratory. From these data, the double isomeric to ground state ratio (DIGS) were extracted with the assistance of the decay equations that were included in the experiment. As the NPIs effects are rather small the lines for analysis had to be chosen carefully so that the extracted ratios would not contain significant errors. The measured DIGS ratios were then compared with the result of the theoretical DIGS ratios. The results showed that the calculated DIGS ratios deviated substantially from unity although this was with large uncertainties. Because of the large errors obtained, the DIGS ratios were found to be inconclusive as a signature for detecting the effects of NPIs such as angular momentum distribution changes in HEDP environmen

Nowadays we are all witnesses of a competition of facilities at different countries to study unknown regions of neutron rich nuclei. Much efforts are devoted to understand the role of neutron excess and its influence on nuclei in vicinity of closed neutron shells. One of the means to investigate nuclear structure is in beta-decay. Once a nucleus is proven to exist, its beta-decay properties, such as T1/2 and Pn (probability of beta-delayed neutron emission), which are relatively easy to measure, can provide the first hints on the nuclear structure. On the r-process site, "waiting points"(nuclei on closed neutron shells) has significant effects on the r-process dynamics and the abundance distribution. The actual side and the astrophysical conditions under which the nuclear synthesis takes place are still not certainly known - since r-process nuclei are difficult to produce and to study experimentally, input parameters for r-process calculations are mostly derived from theoretical models. As it has been seen lately, most of the theories have failed to reproduce newly measured data sets near shell closures. With new experimental data already (or shortly) available theoretical approaches can be adjusted. Since a beta-delayed neutron emission becomes strong if not dominating decaying channel for nuclei far stability, a proper neutron detector to study their properties is indispensable. To conduct the appropriate investigations, in the frame of the present thesis, in close collaboration with JINR (Dubna) a new detection system was constructed. It consists of 80 ³He-filled counters, 4π beta detector and a HPGe in order to measure simultaneously beta, gamma, neutron activity. The development of such a detection system system, currently installed at ALTO ISOL facility, was the first objective of the thesis. Then, during two experimental campaigns conducted to investigate beta decay properties of neutron rich nuclei in the neighborhood of N=50, N=82 the workability of the newly produced detection system was proven. In the vicinity of ⁷⁸Ni: half- lives and probability of beta-delayed neutron emission for ⁸º,⁸²,⁸³,⁸⁴Ga were measured. We were the first to observe the structure of ⁸¹,⁸² Ge via beta neutron gated gamma spectra. Thanks to the neutron detection channel the absolute intensities of beta decay were proposed for the first time. In the vicinity of ¹³²Sn the half lives of ¹²³Ag, ¹²⁴Ag, ¹²⁵Ag and ¹²⁷In, ¹²⁸In was measured. For the first time the beta delayed neutron emission was observed for ¹²⁶Cd, its Pn value also measured. Based on the data obtained we come to the conclusion that to figure out the relative contribution of allowed and forbidden decays more theoretical efforts should be done crossing the N=50 shell. Whereas in the vicinity of N=82 shell more experimental challenge are required.

Aujourd'hui, nous sommes tous témoins d'une compétition des installations en pays différents pour étudier les régions inconnues de noyaux riches en neutrons. Beaucoup d'efforts sont consacrés à comprendre le rôle de l'excès de neutrons et son influence sur les noyaux dans les environs de coquilles de neutrons fermées. Un des moyens pour étudier la structure nucléaire est via la désintégration bêta. Une fois un noyau est prouvé d'exister, ses propriétés de désintégration bêta, comme T1/2 et Pn (probabilité de l'émission de neutrons de bêta-retardés), qui sont relativement faciles à mesurer, peuvent fournir les premiers indices sur la structure nucléaire. Sur le site de processus-r des «points d'attente» (noyaux sur des coquilles de neutrons fermés) ont des effets importants sur la dynamique processus-r ainsi que sur la distribution de l'abondance des éléments. Les conditions astrophysiques exactes en vertu de desquelles la synthèse nucléaire a lieu ne sont pas connus avec certitude. Parce que les noyaux participant en processus-r sont difficiles à synthétiser même aujourd'hui et à étudier expérimentalement, les paramètres nécessaires pour les calculs du processus-r sont principalement dérivés de modèles théoriques. Comme on l'a vu récemment, la plupart des théories n'ont pas réussi à reproduire des ensembles de données nouvellement mesurées près de fermetures de couche. Avec de nouvelles données expérimentales déjà (ou bientôt) disponibles les approches théoriques peuvent être ajustées. Comme émission de neutrons retardée bêta devient plus importante voie le canal dominant en désintégration des noyaux loin d'un stabilité, l'utilisation d'un détecteur de neutrons approprié afin d'étudier leurs propriétés est indispensable. C'est pour mener la recherche appropriée que dans le cadre de la thèse, en étroite collaboration avec le JINR (Dubna) un nouveau système de détection a été construit. Il se compose de 80 compteurs de ³He, un détecteur 4π de bêta et un HPGe afin de mesurer simultanément l'activité de gamma, bêta et neutrons. Le développement d'un tel système de détection, actuellement installé sur ALTO, a été le premier objectif de la thèse. Puis, au cours de deux campagnes expérimentales menées pour examiner les propriétés de désintégration bêta de noyaux riches en neutrons dans le proximité de N = 50, N = 82 la capacité de travail du système de détection produit a été prouvée. Dans le région de ⁷⁸Ni : le temps de vie et de la probabilité de l'émission de neutrons bêta retardés pour ⁸º,⁸²,⁸³,⁸⁴Ga ont été mesurés. Nous sommes les premiers à observer la structure de ⁸¹,⁸² Ge via spectroscopie gamma spectre conditionnée par bêta et par neutron. Grâce à la détection des neutrons les intensités absolues de la désintégration bêta ont été proposées pour la première fois. Dans le région de ¹³²Sn les temps de vie de ¹²³Ag, ¹²⁴Ag, ¹²⁵Ag et ¹²⁷In, ¹²⁸In ont été mesurées. Pour la première fois l'émission de neutrons retardés bêta a été observée pour le cas de ¹²⁶Cd, sa valeur Pn également mesurée. Sur la base des données obtenues, nous arrivons à la conclusion que, pour déterminer la contribution relative de désintégrations permises et interdites les efforts théoriques doivent être faites en traversant la couche N = 50. Alors que dans le région de N = 82 plus de données expérimentales sont nécessaires. / Nowadays we are all witnesses of a competition of facilities at different countries to study unknown regions of neutron rich nuclei. Much efforts are devoted to understand the role of neutron excess and its influence on nuclei in vicinity of closed neutron shells. One of the means to investigate nuclear structure is in beta-decay. Once a nucleus is proven to exist, its beta-decay properties, such as T1/2 and Pn (probability of beta-delayed neutron emission), which are relatively easy to measure, can provide the first hints on the nuclear structure. On the r-process site, "waiting points"(nuclei on closed neutron shells) has significant effects on the r-process dynamics and the abundance distribution. The actual side and the astrophysical conditions under which the nuclear synthesis takes place are still not certainly known - since r-process nuclei are difficult to produce and to study experimentally, input parameters for r-process calculations are mostly derived from theoretical models. As it has been seen lately, most of the theories have failed to reproduce newly measured data sets near shell closures. With new experimental data already (or shortly) available theoretical approaches can be adjusted. Since a beta-delayed neutron emission becomes strong if not dominating decaying channel for nuclei far stability, a proper neutron detector to study their properties is indispensable. To conduct the appropriate investigations, in the frame of the present thesis, in close collaboration with JINR (Dubna) a new detection system was constructed. It consists of 80 ³He-filled counters, 4π beta detector and a HPGe in order to measure simultaneously beta, gamma, neutron activity. The development of such a detection system system, currently installed at ALTO ISOL facility, was the first objective of the thesis. Then, during two experimental campaigns conducted to investigate beta decay properties of neutron rich nuclei in the neighborhood of N=50, N=82 the workability of the newly produced detection system was proven. In the vicinity of ⁷⁸Ni: half- lives and probability of beta-delayed neutron emission for ⁸º,⁸²,⁸³,⁸⁴Ga were measured. We were the first to observe the structure of ⁸¹,⁸² Ge via beta neutron gated gamma spectra. Thanks to the neutron detection channel the absolute intensities of beta decay were proposed for the first time. In the vicinity of ¹³²Sn the half lives of ¹²³Ag, ¹²⁴Ag, ¹²⁵Ag and ¹²⁷In, ¹²⁸In was measured. For the first time the beta delayed neutron emission was observed for ¹²⁶Cd, its Pn value also measured. Based on the data obtained we come to the conclusion that to figure out the relative contribution of allowed and forbidden decays more theoretical efforts should be done crossing the N=50 shell. Whereas in the vicinity of N=82 shell more experimental challenge are required.