TUNL Seminar Series

If you have any questions about upcoming seminars or would like to suggest a future speaker, please contact the chair of the TUNL Seminar Committee, Julieta Gruszko.

Spring 2022

May 5, 2022

Walter Pettus

Assistant Professor, Indiana University

The Project 8 Neutrino Mass Experiment

Although the existence of neutrino mass is firmly established, the precise neutrino mass scale remains unknown.  To directly probe this property, measurements of the endpoint of the tritium beta spectrum have achieved the greatest sensitivity, recently reaching the sub-eV scale.  In this talk, I will present Project 8, an experimental concept based on the novel Cyclotron Radiation Emission Spectroscopy (CRES) technique.  Project 8 has recently completed its first measurements of the tritium beta spectral endpoint and demonstrated its high precision spectroscopy using krypton calibration.  An R&D campaign is now underway to demonstrate scalability of the CRES technique and to develop the atomic tritium source required.  Building on these successes, a next-generation experiment is envisioned with neutrino mass sensitivity down to 40 meV.


Previous seminars

Spring 2022

February 10, 2022

Miguel Marques

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

February 17, 2022

Mitch Allmond

Physics Division, Oak Ridge National Laboratory

The FRIB Decay Station initiator (FDSi)

The Facility for Rare Isotope Beams (FRIB) will provide unprecedented access to exotic nuclei; approximately 80% of the isotopes predicted to exist up to uranium (Z = 92) will be produced. The FRIB Decay Station (FDS) — an efficient, granular, and modular multi-detector system designed under a common infrastructure — will have a transformative impact on our understanding of nuclear structure, nuclear astrophysics, fundamental symmetries, and isotopes of importance to applications.

The FRIB Decay Station Initiator (FDSi), led by the FDSi Coordination Committee and supported by the FDSi Group and Working Groups, is the initial stage of the FRIB Decay Station (FDS). The FDSi is primarily an assembly of the best detectors currently available in the community within an integrated infrastructure for Day One FRIB decay studies, ultimately providing a means for FRIB users to conduct world-class decay spectroscopy experiments with the best equipment possible and to transition to the FDS without interruption to the user program. The FDSi infrastructure will remain intact at FRIB, ready to receive community detectors that will nominally travel.

An overview of the FDSi and scientific program approved by the first FRIB PAC will be given.

*This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.

February 24, 2022

John Wilkerson - Cancelled

March 3, 2022

Raquel Castillo Fernandez

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. 

March 10, 2022

Duke/NCCU Spring Break

March 17, 2022

NCSU/UNC Spring Break

March 24, 2022

Sam Hedges

Duke University/ Triangle Universities Nuclear Laboratory

Neutrino-Nucleus Interactions at the Spallation Neutron Source 

The Spallation Neutron Source (SNS) provides an intense pulsed source of low energy (tens of MeV) neutrinos. The COHERENT collaboration has deployed several detectors to the SNS to study neutrino interactions, including coherent elastic neutrino-nucleus scattering (CEvNS). CEvNS is a neutral-current process, predicted by the standard model, in which an entire nucleus recoils as a result of a neutrino interaction. The process has a large cross section, but the resulting low energy recoils can be difficult to detect. The collaboration has also deployed detectors to study inelastic charged-current neutrino-nucleus interactions, which have relevance for solar and supernova neutrino detection. An overview of COHERENT will be provided, with emphasis on detectors seeking to measure neutrino interactions with lead, iron, and NaI[Tl]. 

March 31, 2022

Jon Engel

Professor, University of North Carolina at Chapel Hill

Quantum Computing for Nuclear-Structure Theory

After introducing the theory of quantum computing and algorithms, I turn to the Variational Quantum Eigensolver, a hybrid classical-quantum approach to computing energies of quantum systems.  I show how to apply a version of the approach to closed-shell nuclei in a schematic model and to open shell nuclei in the usual shell model.  The method scales well with the number of nucleons, making it promising for use on near-term quantum devices.

April 7, 2022

Aobo Li

COSMS Postdoctoral Fellow, University of North Carolina at Chapel Hill

First Search for Majorana Neutrino at the Inverted Mass Ordering Region with KamLAND-Zen

The discovery of neutrinoless double beta decay (0νββ) would shed light on the persistent puzzle surrounding the origin of neutrino mass and help explain the matter-dominated universe. As one of the leading experiments searching for 0νββ,  the KamLAND-Zen has provided a stringent constraint on the neutrinoless double-beta (0νββ) decay half-life in 136Xe using a xenon-loaded liquid scintillator. We report an improved search using an upgraded detector with almost double the amount of xenon and an ultra-low radioactivity container, corresponding to an exposure of 979kg yr of 136Xe. We have not observed 0νββ yet, but this search makes use of novel algorithms to perform beta-gamma separation using machine learning and tag spallation products on order day time scales. As a result, we obtain a lower limit for the 0νββ decay half-life of T > 2.29x10^26 yr at 90% C.L., corresponding to upper limits on the effective Majorana neutrino mass of 36 - 156 meV using commonly adopted nuclear matrix element calculations. Our improved sensitivity provides a limit that reaches below 50 meV for the first time and is the first search for 0νββ in the inverted mass ordering region.

April 14, 2022

Christian Iliadis

J. Ross Macdonald Distinguished Professor, University of North Carolina at Chapel Hill

Ashes to Dust: Meteoritic Grains from Stellar Explosions

The solar system formed from matter that was processed by nuclear reactions in countless stars of prior generations. Most of the matter mixed homogeneously, thereby erasing any peculiar nucleosynthesis imprints from individual host stars. But a tiny fraction retained the original isotopic fingerprints. These so-called "presolar stardust grains" have been detected in primitive meteorites and interstellar dust particles. At TUNL, we are particularly interested in presolar grains that formed in the ejecta of novae and supernovae. The measured isotopic ratios of these grains provide clues about the inner working of their host stars, the explosion mechanism, and the formation of dust in circumstellar outflows. However, this assumes knowledge of the thermonuclear reaction rates that gave rise to the isotopic imprints in the first place. I will discuss our measurement of the 29Si(p,gamma)30P reaction at LENA and its importance for silicon isotopic ratios measured in presolar stardust grains. For more information, see: https://arxiv.org/abs/2202.11568 .

Link to zoom recording

April 21, 2022

Ekaterina Korobkina

Research Professor, North Carolina State University

Growing solid deuterium crystal for Ultra Cold Neutron production

Process of freezing solid deuterium in small targets (cubic cm and mm) is well studied for different applications, i.e. quantum crystal studies, fusion, and neutrino mass.  Recently in neutron physics a new type of neutron sources for ultra low energy neutrons (UltraCold Neutrons, UCN)  were built, which utilize a volume of liters  of frozen solid ortho-deuterium. That implies additional problems for crystal growing due to the  large volume and geometry of the cryostat. We have experimentally studied growing a large (about 1 liter) solid ortho-deuterium crystal in a real UCN source cryostat and recorded the growing process optically using a camera.  Optimum conditions were found for both, obtaining an optically transparent crystal and cooling it down to the operational temperature with minimal damage. We found that quality, final shape and changes during annealing of the crystal are very much dependent on the temperature profile of the cryostat walls. In addition, our study helped to solve a mystery about  decreasing UCN yield at pulsed neutron sources.

April 28, 2022

Spencer Axani

Massachusets Institute of Technology

Exploring cosmic-ray physics with pocket-sized CosmicWatch desktop muon detectors

Cosmic ray muons carry a rich amount of physics that is now easily accessible to citizen and amateur scientists. The CosmicWatch Desktop Muon Detector is an MIT-based physics outreach project that aims to enable a broad audience to work with particle detectors, while also incorporating various aspects of electronics-shop and machine-shop technical development. This talk will focus on the technical aspects of particle detection principles and the detectors themselves, as well as how they can be used to explore the exciting field of astro/particle physics.



Fall 2021

September 23, 2021

Tom Clegg

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.

September 30, 2021

Wei Jia Ong

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.

October 7, 2021

Joule Othman

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.

October 14, 2021

DNP Meeting, no seminar this week

October 21, 2021

Rachel Carr

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/

October 28, 2021

Eric Wulf

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.

November 4, 2021

HIγS Celebration

Mohammad Ahmed

November 11, 2021

HIγS Celebration

Werner Tornow, Vladimir Litvinenko, Norbert Pietralla

November 18, 2021

SESAPS Meeting: no seminar

November 25, 2021

Thanksgiving, no seminar

December 2, 2021

Leendert Hayen

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.

December 9, 2021

Jon Engel

December 16, 2021