TUNL Seminar Series

May 4, 2023

298 Physics Building (Faculty Lounge)

Elevator talk by Michelle Lee at 3:30

Amy Nicholson

UNC Chapel Hill

"Unraveling the structure of the neutron for new physics searches"

There are a number of current and planned low-energy experimental searches for new physics which rely upon the use of neutrons or nuclei as laboratories. Theoretical input to these efforts is crucial for extracting and/or interpreting possible signatures. Lattice QCD is currently our only means for performing first-principle calculations of these inputs directly from the Standard Model. In this talk, I will present a series of lattice QCD calculations with impact for long-baseline neutrino, dark matter, and ultracold neutron experiments, with a focus on high-precision single nucleon observables. 

February 23, 2023

(Remote only)

SURF Webinar:

The broad physics program of the Majorana Demonstrator at SURF: Final results and new directions

Ian Guinn, University of North Carolina - Chapel Hill & Triangle Universities Nuclear Laboratory

Ralph Massarczyk, Los Alamos National Laboratory

Anna Reine, University of North Carolina - Chapel Hill & Triangle Universities Nuclear Laboratory 

Clint Wiseman,  University of Washington

Live webinar will be held on Thursday Feb. 23 at 3:30 pm EST

On the occasion of the publication of our final results, we are presenting a live webinar from SURF on the broad physics program of the MAJORANA DEMONSTRATOR at SURF. The MAJORANA Collaboration began a search for neutrinoless double-beta decay in 2015, and completed its search in 2021 when the enriched Ge-76 detectors were removed for use in the follow-on LEGEND-200 experiment. MAJORANA collaborators will describe the final results from our search for neutrinoless double-beta decay, the experiment’s background modeling, and additional searches for exotic dark matter, physics beyond the standard model, and tests of quantum mechanics. In 2022, the MAJORANA DEMONSTRATOR was reconfigured and began a search for the as-yet unobserved decay of Ta-180m. The webinar will feature a status update and new measurements from the Ta-180m decay search.

Further details on the webinar can be found on the SURF event page at https://sanfordlab.org/event/broad-physics-program-majorana-demonstrator-surf-final-results-and-new-directions

SURF requires registration for the Zoom webinar here: https://us06web.zoom.us/webinar/register/WN_-Uuz22ZlRjiKPPptuqmXVg

They will distribute the zoom link to registrants. 

March 9, 2023

LSRC B101 (Love Auditorium) 

Matt Mumpower

Los Alamos National Laboratory

"Forging the heaviest elements"
A complete understanding of the origin of the elements on the periodic table is one of the most challenging problems in all of physics. The elements of the periodic table are forged in the cosmos, but evidence shows that these elements are not generated at the same time nor the same place. Particularly difficult to describe is the origin of the heaviest elements (like uranium and thorium), which are thought to be synthesized via the rapid capture of free neutrons known as the "r process". This process may ensue in rare classes of supernovae or in compact object mergers such as neutron star-neutron-star binaries or neutron star-black hole binaries. 

March 23, 2023

LSRC B101 (Love Auditorium)

Augusto Machiavelli

Oak Ridge National Laboratory

The structure of exotic neutron-rich nuclei is one of the main science drivers in contemporary nuclear physics research. Our current knowledge of nuclear structure towards the driplines, has clearly established that the paradigm of magic numbers and doubly magic nuclei as we know it near stability changes across the nuclear landscape. Changes in the underlying single-particle structure are intimately related to specific aspects of the effective nuclear force, specifically to its central and tensor components. Thus, a detailed mapping of shell evolution and collectivity at the limits of isospin becomes a key element to understand the atomic nucleus and all its many-body intricacies.

The so-called Islands of Inversion at N= 8, 20, and 40 provide dramatic examples of the evolution of shell structure and collectivity, with its underlying physics mechanism driven by the important role of the neutron–proton force. The effect of isospin on the monopole average of the central and tensor components of the force changes the neutron effective single-particle energies (ESPEs) in such a way that expected shell closures are quenched, opening the door for the collective degrees of freedom to become relevant in the low-lying excitation spectra of these systems, where single-particle excitations were anticipated. Much experimental evidence has been obtained confirming the existence of deformed ground states.

In this seminar we will discuss the nuclei within the Islands of Inversion in the collective model. Our focus will be on the Nilsson assignments of the relevant single-particle states and the predicted level structures and electromagnetic properties. Special emphasis will be given to the comparison of spectroscopic factors, derived from direct reactions measurements, that directly probe the wavefunctions.

March 30, 2023

Special Time:

2 - 3pm

LSRC B101 (Love Auditorium)

Ingo Wiedenhoever

Florida State University

"Nuclear Astrophysics Research at the FSU accelerator laboratory"

The John D. Fox laboratory at FSU has developed unique experimental resources to study explosive nucleosynthesis, with the RESOLUT radioactive beam facility, the ANASEN active-target detector and the high-resolution Super-Enge Split Pole Spectrograph. Examples for research with these facilities will be presented, from Big-Bang to Nova and Supernova nucleosynthesis as well as future plans and ideas.   FSU, like TUNL, is a founding member of ARUNA, the association for Research with University Nuclear Accelerators. I will make a case that university-based laboratories are becoming more important to our field, which otherwise has consolidated into only two national user facilities. 

April 6, 2023

LSRC B101 (Love Auditorium)

Ben Jones

University of Texas at Arlington

"Single Barium Ion Identification Technologies for Background-Free Neutrinoless Double Beta Decay Searches"

The goal of future neutrinoless double beta decay experiments is to establish whether neutrino is its own antiparticle, by searching for an ultra-rare decay process with a half life that may be more than 10²⁸ years.  Such a discovery would have major implications for cosmology and particle physics, but requires multi-ton-scale detectors with backgrounds below 0.1 counts per ton per year.  This is a formidable technological challenge that seems likely to require unconventional solutions.  In this talk I will discuss new technologies emerging at the interfaces between nuclear physics, microscopy, AMO physics, and biochemistry that aim to identify the single 136Ba daughter nucleus produced in double beta decays of the isotope 136Xe. If these atoms or ions can be collected and imaged with sufficiently high efficiency, the radiogenic backgrounds limiting the sensitivity of all existing technologies could be entirely mitigated. This would enable a new class of large scale, ultra-low background neutrinoless double beta decay experiments.

April 13, 2023

LSRC B101 (Love Auditorium)

Elevator talk by Ethan Mancil at 3:30

Yutian Feng

Duke University

"Targeted Radionuclide Therapy and Production of Novel Radionuclides at the Duke Cyclotron Facility."

Targeted radionuclide therapy (TRT) is an attractive treatment option for many cancers, because it can selectively deliver curative radiation doses to cancer cells with minimum off target toxicity. Targeted radionuclide therapy deploys therapeutic radioisotopes that emit charged particles such as α-particles, β-particles or Meitner-Auger electrons (MAE), facilitated by targeting vectors that are recognized by receptors or other molecules that are overexpressed on cancer cells. Astatine-211 is one of the most promising α-particle emitters for TRT and Duke has been a leading force in the development of TRT agents containing At-211. Many preclinical and clinical evaluations of At-211-labeled TRT agents have demonstrated remarkable therapeutic efficacies against different cancers. On the other hand, Meitner-Auger electron emitters are an appealing alternative because of their short range and high cytotoxicity; however, efforts are needed to develop the production and purification chemistry for the MAE radionuclides.

April 20, 2023

LSRC B101 (Love Auditorium)

Elevator talk by Tyler Kowalewski at 3:30

Sanjana Curtis

University of Chicago

"Neutrinos, Nucleosynthesis and Kilonovae"

When neutron star binaries merge, they eject neutron-rich matter that undergoes r-process nucleosynthesis, producing some of the heaviest elements in our Universe. While this basic picture has been confirmed by the detection of the AT2017gfo kilonova, the details of heavy element nucleosynthesis remain elusive, and it remains unclear whether such mergers are the only site of the r-process. In this talk, I will provide an overview of the various components of merger ejecta and their respective compositions. In the extreme conditions produced during mergers, neutrino-matter interactions set the composition of the ejected material, and in turn set the properties of the electromagnetic transients we observe. I will present 3D simulations of post-merger remnants, performed using GRMHD with neutrino transport, and discuss the connection between the neutrino physics treatment, nucleosynthesis and kilonovae. The inclusion of accurate nuclear and neutrino physics in merger models is crucial for interpreting past and future observations of kilonovae and finally solving the mystery of the origin of heavy elements. 

April 27, 2023

298 Physics Building (Faculty Lounge)

Bob Runkle

Pacific Northwest National Laboratory

"Pacific Northwest Physics – a little bit about a lot of things: an overview of low-background detection at Pacific Northwest National Laboratory"

Physicists at Pacific Northwest National Laboratory have been developing low-background detection systems for decades. These patient people studied neutrinoless double beta decay and dark matter back in the 1980s. This presentation will overview the detection systems, including those housed in a specialized shallow underground laboratory, that support detector development, scientific experiments, and treaty verification. This is an age of physics discovery with vanguard opportunities in neutrinos and dark matter. It’s also a time of change for applied missions, in particular nuclear nonproliferation. This presentation will touch on key challenges in both domains, how they connect, and the work Pacific Northwest National Laboratory performs in support.

Physics Department, University of Texas Arlington

The practical beauty of neutrinos: uncovering the mysteries of the (anti)matter

Why is there more matter than anti-matter in the Universe? Do we know all the particles that constitute the Universe?

Neutrinos are the most abundant massive particle in the Universe. However, its properties have been challenging the knowledge we thought we had during the last decades. Still today, neutrinos remain as the most mysterious particle we know the existence of. We don’t know the origin of their mass, or if neutrinos can be their own anti-particle. Each neutrino property we unravel becomes a major breakthrough in science, and a new insight of new physics beyond the well stablished Standard Model. In this talk, we’ll walk through the neutrino properties and the unprecedented discoveries driven by them. In addition, we will also explore how the complexity of the interactions of this little tiny particles sculpts a precise understanding of the dynamics, from the atomic nuclei to neutron starts and the Big Bang, and how neutrino research opens new discussions and opportunities and will lead to new discoveries and a more coherent description of the Universe. 

Laboratoire de physique corpusculaire de Caen

The neutron as a building block: a challenge for experiment and theory

Already in the early 1960s, when physicists started to move away from the valley of stability, some ambitious ones tried to put several neutrons together and create "neutral nuclei" in their laboratories. They didn't succeed, but the task was a very difficult (while fascinating) one, both from the construction and the detection points of view. Fascination overcame difficulty and other physicists kept trying to find these objects, that would defy nuclear theory as we know it, all through the XX century. Finally, in this XXI century two signals of a possible tetraneutron state close to threshold were obtained, first at GANIL and then at RIKEN, that were weak but have not been contested yet. They have triggered a lot of new theoretical calculations, as well as new generation experiments that try to reveal something that has eluded firm evidence for sixty years already. I will review some of the most exotic experiments, highlight their merits and drawbacks, and show why the present ones think they will succeed where so many others have failed. See related research in https://link.springer.com/article/10.1140/epja/s10050-021-00417-8

Physics Division, Oak Ridge National Laboratory

The FRIB Decay Station initiator (FDSi)

UNC Chapel Hill

TUNL's History

Our seminar this week will be given by Tom Clegg and will provide a view of the formation and development of the nuclear physics activities amongst the Triangle area universities.

Lawrence Livermore National Laboratory

Presolar grains as constraints on the origin of the p-nuclei.

There are ~30 naturally existing nuclei on the proton-rich side of the valley of stability which origin cannot be explained by neutron-capture processes. The nuclear astrophysical process (or combination of processes) that lead to the synthesis of these nuclei is not well understood or constrained. Since these p-nuclei are less abundant than the other isotopes of the same elements, astronomical spectroscopy is currently a limited source of data that can be used to constrain the astrophysical environment of origin. Presolar grains, or stellar condensates, can preserve single-event nucleosynthetic signatures from their parent star and can be exploited as a source of information on the formation of the p-nuclei. I will discuss the ongoing cosmochemical and nuclear physics efforts to investigate the origin of the p-nuclei.

UNC Chapel Hill and TUNL

The CAGE Scanner: Investigating Surface Backgrounds in High-Purity
Germanium Detectors

The neutrino is an elusive particle that has challenged our models of the universe. With the discovery of neutrino oscillations, we know that neutrinos have mass, which disagrees with the Standard Model (SM) of particle physics. However, we still do not know the mechanism by which neutrinos obtain their mass.  The discovery of neutrinoless double-beta decay would have a profound impact on our understanding of neutrinos and the universe. It would show that the neutrino is its own antiparticle, ie. a Majorana particle, that lepton number is not a conserved quantity, and would give us insight into the matter-antimatter asymmetry. Next-generation searches for neutrinoless double-beta decay, such as LEGEND, are working to build ton-scale experiments with the goal of discovering neutrinoless double-beta decay.  To discover such a rare process, experiments must be extremely low-background to mitigate unwanted signals that may obscure the signal of interest from neutrinoless double-beta decay. This is accomplished primarily by locating experiments underground to shield against cosmic rays, using very radiopure materials, active vetos, and using pulse shape discrimination in analysis. The LEGEND experiment will operate 76Ge-enriched pointcontact High-Purity germanium (HPGe) detectors directly immersed in a liquid argon (LAr) active veto.

A significant background expected in LEGEND is from radiation interacting near the surfaces of the detectors. Thin passivated surfaces are particularly susceptible to shallowly impinging alpha and beta radiation. To help further mitigate against surface backgrounds on passivated surfaces, dedicated test stands can help us understand the detector response to surface backgrounds and develop cuts to remove them from our data, maximizing our discovery sensitivity to neutrinoless double-beta decay. In this dissertation, we introduce the Collimated Alphas, Gammas, and Electrons (CAGE) test stand, which we built to study passivated surfaces for HPGe detector geometries that will be used in LEGEND. CAGE utilizes collimated radiation sources to study the effect of shallowly impinging radiation on specific locations on the passivated surfaces of HPGe detectors. We improve on previous surface scanning systems by offering more protection from infrared (IR) shine on passivated surfaces and more  flexibility in positioning the collimated source beam, most notably the ability to change the incidence angle of the source beam with respect to the passivated surface of the detector. We show that CAGE is able to operate stably and show the first results from a radial scan of a P-type Point-Contact detector using a 241Am alpha and gamma source. We present the results of a study of the risetimes of the 59.5 keV gamma from 241Am and show that certain risetime parameters can be useful in discriminating against surface backgrounds in LEGEND. We conclude by discussing the future goals of the CAGE test stand.

Assistant Professor, US Naval Academy

Title:  Results of the Nu Tools Study: Exploring Practical Roles for Neutrinos in Nuclear Energy and Security

Abstract:  For decades, physicists have used neutrinos from nuclear reactors to advance basic science. These pursuits have inspired many ideas for applications of neutrino detectors in nuclear energy and security. While developments in neutrino science are now making some of these ideas technically feasible, it has not been clear how practically they mesh with the needs, budgets, and other constraints of end users such as the International Atomic Energy Agency. In 2019, the National Nuclear Security Administration's Office of Defense Nuclear Nonproliferation R&D commissioned a community study on this question. The study, called Nu Tools, included extensive interviews with over 40 nuclear security and energy professionals. Perhaps surprisingly, these experts do see practical niches for neutrino detectors, but not in the places neutrino physicists have often seen them. This talk will review the Nu Tools study and findings, available in full at: https://nutools.ornl.gov/

Research Physicist, Naval Research Labs

From Novel Scintillators to Germanium for Space-based Gamma-Ray Astrophysics

Terrestrial and space based gamma-ray detection has an insatiable demand for improved detectors and electronics.  Two decades of Homeland Security funding has produced many new scintillators especially the elpasolites.  And mass production of LIDAR systems has helped to evolve cheap and efficient Silicon Photomultipliers (SiPM).  The Naval Research Laboratory is working to boost the Technology Readiness Level (TRL) of these materials and detectors to prepare them for current and future gamma-ray astrophysics missions by launching multiple satellite payloads in recent years.  An overview of the dectector work and these missions will be presented.

In addition, the Compton Spectrometer and Imager (COSI) Small Explorer was selected last week for a NASA mission.  The COSI readout electronics for the 16 double-side germanium strip detectors center around a 32-channel ASIC developed by NRL for silicon and germanium strip detectors.  A discussion of the COSI, the ASIC, and the readout electronics effort for COSI will be presented.

Mohammad Ahmed

Werner Tornow, Vladimir Litvinenko, Norbert Pietralla

Research Scientist, NCSU

The neutron as a gateway to new physics: plans and perspectives

Several anomalies currently exist within particle physics at large, compounded by open questions such as the matter-antimatter asymmetry or the nature of dark matter and neutrinos. Precise measurements of beta decays have both been at the inception of the current Standard Model and continue to be a model-independent pathway to looking for exotic physics. In the light of the current Cabbibo-Kobayashi-Maskawa non-unitarity indications, I will briefly introduce the shift in electroweak radiative corrections that initially caused it and shed light on new work. The Nab experiment at Oak Ridge National Lab measures the angular correlation between outgoing states following neutron beta decay and is is a central effort in this endeavour. I will outline its general principles and present the current status of detailed detector modeling work.