Previous Seminars

Samuel A. Giuliani Nuclear physics and r-process nucleosynthesis of heavy elements
Frank Leonel Bello Garrote Scissors Resonance in 254No
Luis Robledo Dynamic and Static Octupole Correlations
Mario Gómez-Ramos Study of "quenching factors" for (p,pn) and (p,2p) reactions through the Transfer to the Continuum formalism
Simon Sels Laser spectroscopy of radioactive isotopes at ISOLDE using MIRACLS
Michael Jentschel Gamma-ray Spectroscopy with Perfect Crystal Spectrometers
Gemma L. Wilson Studying beta-delayed neutron emission with recoil-ion spectroscopy
Sean Collins Primary standardisation of Th-227 – developing traceability and nuclear data for a novel alpha-emitting radiopharmaceutical
Steven W. Yates Probing the structure of the Ge nuclei with fast neutrons: Neutrinoless Double-Beta Decay and Shape Coexistence
Konstantin Mashtakov Study of the Pygmy Dipole Resonance in 96Zr following the beta decay of 96Y
Skyler Degenkolb Searching for permanent electric dipole moments
Jack Wilson Space-Based Measurement of the Neutron Lifetime using Data from the Neutron Spectrometers on NASA's MESSENGER and Lunar Prospector Missions
Antonio Márquez Romero Proton-neutron pairing description using symmetry-restored mean-field methods
David O'Donnell Measurements of the low-energy dipole strength in actinide nuclei
Ragnar Stroberg Can we do all of nuclear physics ab initio?
Pieter Van Isacker The Structure of Octupole Phonons in Nuclei
Mark Spieker Isospin symmetry around 56Ni
Ruben Pieter De Groote New frontiers in optical spectroscopy of radioactive nuclei
Kaitlin Cook Halo structure of the neutron-dripline nucleus 19B
Manuela Cavallaro Nuclear Reactions for neutrinoless double beta decay
Ruth Newton Quantum Entanglement in PET imaging
Sergio Cristallo The cosmic nucleosynthesis competition between low mass stars and neutron stars mergers
Carlo Barbieri Ab Initio Computations of Ground State Correlations and Optical Potentials in Nuclei
Robin Smith Nuclear structure and astrophysics with TPC detectors and gamma beams
Ryo Taniuchi In-beam gamma-ray spectroscopy of 78Ni revealed its double magicity and shape-coexistence
Daniel Doherty Shape Evolution and Triaxiality in Hitherto Inaccessible Regions of the Nuclear Chart
Lindsay Michelle Donaldson Resolving discrepancies between (p,p') and (γ,xn) reactions
Kyle Leach The BeEST Experiment: A Search for keV-Scale Neutrinos in the EC Decay of 7Be with Superconducting Quantum Sensors
David Sharp Probing single-particle structure near the Island of Inversion with the ISOLDE Solenoidal Spectrometer
Michael Bowry The Search for Nuclear Pear Shapes
Gregory Christian Particle-Gated Transfer Reactions to Understand Stellar Nucleosynthesis
Kelly Chipps Experimental Approaches for Constraining Nuclear Contributions to R-Process Uncertainties
Jack Henderson Testing modern microscopic calculations: Coulomb excitation of mirror pairs in the sd-shell
Benjamin Kay Solenoidal spectrometer techniques: HELIOS, ISS, and SOLARIS
Alessandro Pastore Neurons, Trees and Forests: A different approach to simple nuclear structure problems

Samuel A. Giuliani

Michigan State University

Nuclear physics and r-process nucleosynthesis of heavy elements
The modeling of nuclear structure properties of neutron-rich nuclei is a crucial ingredient for understanding the production of heavy elements during the rapid neutron capture process (or r-process). In order to properly interpret future kilonova observations, sensitivity studies addressing the impact of nuclear theoretical uncertainties are required. In this talk, I will present some recent network calculations based on nuclear input obtained within the Density Functional Theory (DFT) framework. In particular, I will focus in the role of nuclear masses and fission properties in the production of translead nuclei, and the possible implications for the electromagnetic counterparts produced during neutron star mergers. In the second part of this talk, I will introduce some recent advances regarding the large-scale DFT calculation of fission fragments distributions and the estimation of theoretical uncertainties using Bayesian machine-learning techniques.
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Frank Leonel Bello Garrote

University of Oslo

Scissors Resonance in 254No
The nuclear physics group at the University of Oslo primarily dedicates to perform experimental studies of the main average nuclear properties: the nuclear level density and the γ-ray strength function (γ-SF). These quantities are crucial inputs for calculating neutron capture rates relevant for stellar nucleosynthesis simulations. The scissors mode is a collective, magnetic dipole excitation that has been observed in the 2-4 MeV region of the γ-SF in a large group of deformed nuclides. The scissors mode could be of particular importance in the region of the heaviest elements, where the presence of a large resonance in the γ-SF could boost the neutron capture channel relative to fission. In this work, we obtained an experimental spectrum of 254No from which we estimate the strength of the scissors resonance and compare it to theoretical values and empirical formulas used in nuclear reaction codes.
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Luis Robledo

Universidad Autónoma de Madrid

Dynamic and Static Octupole Correlations
Static octupole correlations, which are associated with reflection symmetry breaking at the mean field level, are only present in a handful of nuclei scattered over the periodic table around specific proton and neutron numbers. This is in contrast with the well known prevalence of quadrupole-deformed over spherical shapes in nuclei. However, dynamical correlations, consequence of the relative softness of the nucleus against perturbation of octupole kind, are present in most of the nuclei. They play a role in understanding excitation energies and transition strengths of collective negative parity excitations. In this talk I will address the theoretical description of octupole correlations with techniques beyond the mean field, including symmetry restoration and configuration mixing. The results of calculations along that line will be analyzed.
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Mario Gómez-Ramos

TU Darmstadt

Study of "quenching factors" for (p,pn) and (p,2p) reactions through the Transfer to the Continuum formalism
Nucleon removal (p,pn) and (p,2p) reactions at intermediate energies have proven to be a strong tool to extract information from exotic nuclei. In this talk, several results for (p,pn)and (p,2p) reactions are presented, using the Transfer to the Continuum formalism for their description. Particular interest is devoted to the dependence of the so-called reduction factors Rs (ratios between experimental and theoretical cross sections) on the nuclear asymmetry ∆S, as this dependence shows inconsistencies between different reactions and is currently an open problem. The application of (p, pn) reactions to Borromean system is also explored, focusing on the measured 11Li(p,pn) and 14Be(p,pn) reactions.
Finally, (p,3p) reactions are a promising probe to populate and study very neutron-rich nuclei, as the population of the second 2+ state in 78Ni from 80Zn(p,3p) has shown. Unfortunately, the description of (p,3p) reactions is still unclear. As a first step to understand them, a simple kinematical study of (p,3p) reactions is presented.
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Simon Sels

KU Leuven

Laser spectroscopy of radioactive isotopes at ISOLDE using MIRACLS
Laser spectroscopy is a powerful and well-established technique for the study of nuclear ground-state properties at radioactive ion beam facilities. It provides access to the mean-square charge radii differences and electromagnetic moments of the nuclear ground state as well as of long-lived isomers by measuring the isotope shifts and hyperfine structures of the atoms’ spectral lines [1, 2]. While in-source laser spectroscopy in a hot cavity or in a gas cell are very sensitive methods that are able to measure rare isotopes with production rates below one ion per second [3,4], the spectral resolution of this method is limited by Doppler broadening. Collinear laser spectroscopy (CLS) on the other hand, provides an excellent spectral resolution. However, conventional fluorescence-based CLS requires yields of more than 100 or even 10,000 ions/s depending on the specific case and spectroscopic transition [5]. Techniques for both in-source as well as for collinear laser spectroscopy at radioactive ion beam facilities are being developed to push the limits of sensitivity and spectral resolution further than what is possible today. Some of these recent developments will be presented in this talk. Focus will be put on examples of in-gas-jet laser spectroscopy and MIRACLS-type collinear laser spectroscopy.
[1] K. Blaum, et al., Phys. Scr. T152, 014017 (2013)
[2] P. Campbell et al., Prog. Part. and Nucl. Phys. 86, 127-180 (2016)
[3] B. Marsh et al., Nature Physics 14, 1163-1167 (2018)
[4] M. Laatiaoui et al. Nature 538, 495-498 (2016)
[5] R. Neugart, J. Phys. G: Nucl. Part. Phys. 44 (2017)
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Michael Jentschel

Institut Laue-Langevin (ILL)

Gamma-ray Spectroscopy with Perfect Crystal Spectrometers
The ILL operates one of the most intense neutron sources for research in the world. Although primarily used for neutron scattering there exist a long-standing history of gamma ray spectroscopy at the ILL. The availability of well collimated intense neutron beams and in-pile sample irradiation positions allowed to develop quite unique instruments and applications of gamma ray spectroscopy. In a first part I will give a brief overview on ILL’s nuclear physics instrument suite.
Amongst the operating gamma ray instruments the ultra-high-resolution gamma ray spectrometers GAMS played a particular role due to their outstanding energy resolution and dynamic range. The instruments are based on perfect crystal Laue diffraction of gamma rays yielding an energy resolution down to a few eV at MeV energies. The instruments contributed in the past to many different fields in physics: nuclear structure, metrology, photon matter interaction, crystallography and astrophysics. In a second part the talk will review some highlights from the recent years of operation of these instruments.
In 2020 the ILL decided to decommission the GAMS spectrometers. Therefore, in the third and last part of the talk I will try to give an outlook in which field the techniques and technology of the GAMS spectrometers could be used in the future. In this respect I will focus mainly on the combination of such devices with a Laser-Compton source for NRF experiments.
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Gemma L. Wilson

Louisiana State University/Argonne National Laboratory

Studying beta-delayed neutron emission with recoil-ion spectroscopy
In nuclear β decay, β-delayed neutron (βn) emission is a viable process if the Qβ value of the parent (precursor) nucleus is greater than the neutron separation energy Sn in the daughter (emitter) nucleus, making it a common decay mode in neutron-rich nuclei. The lack of experimental βn data is being addressed with experimental efforts at radioactive ion facilities worldwide, including recoil-ion time-of-flight spectroscopy.
The use of trapped ions for βn spectroscopy is a relatively new and powerful technique. By design this technique avoids any difficulties inherent in neutron detection, but instead infers all neutron information from a distinct signature of the recoiling emitter nucleus. The Beta-decay Paul Trap (BPT) at Argonne National Laboratory (ANL) is used to confine ions to a small volume (~1 mm3) and decay products are detected by a simple detector system. From the detection of the β, the recoiling nucleus and any γ rays, β decay can be distinguished from βn decay, and a neutron energy spectrum can be inferred. The measurements are relatively low in background and can potentially be made with beam intensities as low as ~0.1 ions/s, which opens up a wide range of exotic nuclei for study.
Following the success of this technique with the BPT, the next generation of trap and detector array for recoil-ion time-of-flight spectroscopy has been designed for use with beams from the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) at ANL, and has been fully funded by the US DOE Office of Nuclear Physics. The BEtARecoil ion trap, or BEARtrap, is a dedicated setup, which incorporates improvements on the BPT that have been investigated using simulations with GEANT4 and SimIon.
This talk will discuss details of this technique and present the various physical phenomena that influence the reconstruction of the βn energy inferred from the trapped ion technique. The finalized design of BEARtrap will be presented, including results from simulations, and details of approved upcoming experiments and future prospects.
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Sean Collins

National Physical Laboratory/University of Surrey

Primary standardisation of Th-227 – developing traceability and nuclear data for a novel alpha-emitting radiopharmaceutical
The National Physical Laboratory (NPL) is the National Metrology Institute (NMI) for the UK. As an NMI it has a key role to provide traceability for pre-clinical and clinical administrations of radiopharmaceuticals through primary standardisation of radioactivity. These primary standardisations are typically performed through coincidence counting techniques, which negate the need for any prior knowledge of the detection efficiency or of nuclear data. Thorium-227 (T1/2 = 18.697 d) is one such radionuclide with potential as a therapeutic radionuclide for applications in targeted alpha-radioimmunotherapy. Through binding of Th-227 to a monoclonal antibody this radiopharmaceutical has been shown as a having proficient tumour killing capabilities for a range of lymphoma, leukaemia, breast, and ovarian tumour cells. To provide nuclear medicine departments involved in Phase I clinical trials traceability the NPL has developed a primary standard for Th-227. To manufacture this radiopharmaceutical before administration to patients, the decay progeny must be removed initially to create a radiochemically pure starting material. This poses complications for accurate activity measurements, since transient equilibrium is not reached until well after 200 days, as the ingrowth and decay of the decay progeny must be corrected for as well as determining the effective time zero of the radiochemical separation. As a consequence of the temporal relationship of Th-227 with its decay progeny accurate and precise nuclear data are required for accurate activity measurements, which at the start of this project were not available. In this presentation, we will discuss the realisation of the Th-227 primary standardisation along with determinations of the half-lives and absolute gamma-ray emission intensities of Th-227 and its decay progeny.
Missing first 5 minutes, please see attached slides.
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Steven W. Yates

University of Kentucky

Probing the structure of the Ge nuclei with fast neutrons: Neutrinoless Double-Beta Decay and Shape Coexistence
At the University of Kentucky Accelerator Laboratory, we observed γ rays following inelastic scattering of fast neutrons from several candidates for neutrinoless double-beta decay (0νββ), with our recent measurements focusing on 76Ge [1], 136Xe [2], and other nuclei in these regions. From these measurements, low-lying excited states were characterized, 0+ states and their decays were identified, level lifetimes were measured with the Doppler-shift attenuation method, multipole mixing ratios were established, and transition probabilities were determined.
The rate of 0νββ is approximately the product of three factors: the known phase- space factor for the emission of the two electrons, the effective Majorana mass of the electron neutrino, and a nuclear matrix element (NME) squared. The NMEs cannot be determined experimentally and, therefore, must be calculated from nuclear structure models. A focus of our recent measurements has been on providing detailed nuclear structure data to guide these model calculations in the Ge region, and a procedure for future work, which will lead to meaningful data for constraining calculations of NMEs, is suggested.
This material is based upon work supported by the U.S. National Science Foundation under grant no. PHY-1913028.
[1] S. Mukhopadhyay, et al., Phys. Rev. C 95, 014327 (2017).
[2] E.E. Peters, et al., Phys. Rev. C 98, 034302 (2018).
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Konstantin Mashtakov

University of the West of Scotland

Study of the Pygmy Dipole Resonance in 96Zr following the beta decay of 96Y
The pygmy dipole resonance (PDR) is a nuclear phenomenon which is associated with the movement of the ‘neutron skin’ of a nucleus against an isospin saturated proton-neutron core. The nature of the PDR is of particular interest due to its importance in many areas of nuclear and astrophysics.
Current experimental techniques used to study this phenomenon produce inconsistent results. This is mostly due to the unknown branching behaviour of the Jπ =1 levels, which form the PDR. The nuclear resonance fluorescence (NRF) technique, which is widely used to study low-lying E1 strength in stable nuclei, loses decay branches to lower-lying excited states to the atomic background. The latter effect leads to underestimated values of E1 strength of the PDR. Recently it was realised that electric dipole levels associated with the PDR could also be excited following the β decay of certain nuclei. The novel approach of using β decay to populate high-lying 1 states allows the extraction of branching transitions previously not resolved in NRF, which will recover missing E1 strength associated with the PDR.
In this work, the nature of the high-lying final levels of the 96Ygs beta decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum, has been investigated in high-resolution gamma-ray spectroscopy following the beta decay as well as in a campaign of inelastic photon scattering experiments. The combined data represents a comprehensive approach to the wavefunction of the 1 levels below the Qbeta value (7.1 MeV), which are also studied in the Quasiparticle Phonon Model. The calculations reveal that the components populated in beta decay contribute only with small amplitudes to the complex wavefunction of these 1 levels. A comparison of the beta decay results to data from total absorption gamma-ray spectroscopy demonstrates that high-resolution spectroscopy using modern detector arrays is capable to resolve the pandemonium effect.
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Skyler Degenkolb

Institut Laue–Langevin (ILL)

Searching for permanent electric dipole moments
Discrete symmetries provide a powerful means of classifying and constraining models in nuclear and particle physics, including the Standard Model. Although the Standard Model predicts finite values for CP-violating electromagnetic moments (both for fundamental particles and for composite systems), today's experiments are insufficiently sensitive -- by several orders of magnitude -- to test these predictions. Nevertheless, experimental limits consistent with zero have played an important role in constraining Standard Model parameters and extended models with new sources of CP violation. In particular, searches for permanent electric dipole moments (EDMs) test the Standard Model at high precision, provide diagnostic power for new sources of CP violation, and connect deeply to the symmetry-breaking mechanisms required for baryogenesis. I will survey the main target systems and experimental techniques that are employed in modern EDM measurements, with some emphasis on neutrons and the nuclei of diamagnetic atoms. I will also discuss the phenomenological interpretation of EDM limits, and in particular the "global analysis", or joint constraints, that are enabled by multiple experiments in complementary systems.
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