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 2024

Date Description

February 29, 2024

FEL Conference Room

1:20-2:30pm

Matt Morano, NC State

The neutron Electric Dipole Moment at the Spallation Neutron Source (nEDM@SNS) experiment was designed to set the nEDM upper limit at the ∼3 ×10−28 e · cm level. To reach this sensitivity, the Systematics and Observational Studies at the PULSTAR reactor (SOS@PULSTAR) apparatus began commissioning, with the goal of characterizing systematic effects present in nEDM@SNS. SOS@PULSTAR also provides a testbed for more rapidly developing hardware and experimental techniques, that can later be implemented in the nEDM@SNS apparatus. Carrying out a measurement involves performing Nuclear Magnetic Resonance (NMR) on Ultra-Cold Neutrons (UCNs), and 3He simultaneously. This means a single NMR pulse must be able to correctly manipulate both the UCN and 3He spins. To do this, an optimization algorithm based on simulated annealing was designed for tailoring NMR pulses. Achieving the desired sensitivity places strict requirements on the holding magnetic field homogeneity. For this reason, a system was constructed that can actively cancel magnetic fields down to the low nT level. Custom high precision, high stability current sources were also designed for use with shimming coils to further improve the homogeneity. And finally, for simulating systematic effects, a particle spin tracking code was developed which can be deployed on CPU and GPU based supercomputers.

March 7, 2024 Leah Broussard, Oak Ridge National Laboratory
March 28, 2024 Anthony Kuchera, Davidson College
April 4, 2024 Gustavo Nobre, Brookhaven National Laboratory
May 30, 2024 Ronald Fernando Garcia Ruiz, Massachusetts Institute of Technology

Past Seminars

Spring 2024

Date Description

Jan. 25, 2024

2-3pm

298 Physics Building (Faculty Lounge)

Janina Hakenmuller, Duke University

First detection of CEvNS on germanium by COHERENT


The COHERENT experiment at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory detects coherent elastic neutrino nucleus scattering (CEvNS) with a multitude of different detector technologies. In this process the neutrino interacts with the nucleus as a whole resulting in a low energy recoil. Neutrino energies below 50 MeV are required as provided by the pulsed beam of the SNS.In my talk, I will present the first detection of CEvNS with large-sized low threshold germanium spectrometers. We achieved a significance of 3.9 sigma with a total exposure of 7.47 GWh*kg and an ionization energy threshold of 1.5keV. I will cover the analysis in detail and also talk about future efforts within the COHERENT experiment.

Feb. 8, 2024

 

Zheng-Tian Lu, School of Physical Sciences, University of Science and Technology of China, Hefei National Laboratory

Identifying Old Ice and Water with Single-Atom Counting

 

The long-lived noble-gas isotope 81Kr is the ideal tracer for old water and ice with ages of 0.1 – 1 million years, a range beyond the reach of 14C.  81Kr-dating, a concept pursued over the past five decades, is now available to the earth science community at large.  This is made possible by the development of the Atom Trap Trace Analysis (ATTA) method, in which individual atoms of the desired isotope are captured and detected.  ATTA possesses superior selectivity, and is thus far used to analyze the environmental radioactive isotopes 81Kr, 85Kr, and 39Ar.  These three isotopes have extremely low isotopic abundances in the range of 10-17 to 10-11, and cover a wide range of ages and applications.  In collaboration with earth scientists, we are dating groundwater and mapping its flow in major aquifers around the world, and dating old ice from the deep ice cores of Antarctica, Greenland, and the Tibetan Plateau. For an update on this worldwide effort, please google “ATTA Primer”.

Feb. 15, 2024

 

Eve Armstong, New York Institute of Technology,  American Museum of Natural History

Predicting the behavior of sparsely sampled systems across astrophysics, neurobiology, and epidemiology

Inference is a term that encompasses many techniques including machine learning and statistical data assimilation (SDA). Unlike machine learning, which harnesses predictive power from extremely large data sets, SDA is designed for sparsely sampled systems.  This is the realm of study of any realistic system in nature.  SDA was invented for numerical weather prediction, an inherently nonlinear – and chaotic – problem.  My collaborators and I have taken SDA into new fields, to inform the role of neutrinos in astrophysics, biological neuronal networks, and an epidemiological population model tailored to the coronavirus SARS-CoV-2.  We use SDA to seek solutions that are consistent with both sparse measurements and a partially-known dynamical model of the system from which those measurements arose.  The versatility of SDA across vast disciplines (and vast temporal and spatial scales) shows how these “distinct” environments possess commonalities that can inform one another.

Fall 2023

Date Description
August 31, 2023

Andrew Cooper, Los Alamos National Laboratory

Tomorrow’s experimental capabilities, today: The Neutron Target Demonstrator at LANSCE

The capability to directly measure neutron capture reactions on short-lived (𝑡!/#~ minutes) radionuclides would grant access to all s-process and some i-process reactions in the laboratory, along with many reactions of interest to nuclear energy applications. However, precision measurements in forward kinematics are currently prohibited because the radiation fields originating from stationary targets overwhelm the detection system, the target sample sizes are too small, or the target lifetimes are too short. These experimental challenges can be overcome by circulating the radioactive sample within an ion beam storage ring and through a thermal neutron field to induce capture reactions in inverse kinematics. We are pursuing such a neutron target facility consisting of a high-intensity, heavily moderated spallation neutron target coupled with a radioactive ion beam storage ring at the Los Alamos Neutron Science Center (LANSCE). First experiments with the Neutron Target Demonstrator (NTD) at LANSCE have received full support through the Laboratory Directed Research and Development (LDRD) program to validate this neutron target facility concept, and testing will begin this fall. The simulation, design, execution, and technical impact of these NTD experiments will be described, along with Monte Carlo N-Particle (MCNP) simulations of a future neutron target facility at LANSCE. We will close with a discussion of the NTD project timeline and collaboration opportunities.

September 28, 2023

Dieter Ries, Paul Scherrer Institute

Experiments with ultracold neutrons at PSI

The ultracold neutron (UCN) source at the Paul Scherrer Institut is
being successfully operated since 2011 and has provided UCN for example to the nEDM experiment, which has placed the tightest constraints to date on the neutron's electric dipole moment in 2020. Currently the successor experiment n2EDM is being commissioned at the same position. At the second beam port, the neutron lifetime experiment τSPECT, developed at Johannes Gutenberg University Mainz, is currently being set up for data taking. τSPECT is the first neutron lifetime experiment using spin-flip loading and 3-dimensional magnetic storage of neutrons.

In this talk, the status of both experiments and first results from
commissioning with neutrons will be presented.

October 5, 2023

Dipangkar Dutta, Mississippi State University


Searching for “heavy light”: what can electron scattering tell
us about the Atomki X(17) anomaly?


A recent series of experiments at the ATOMKI 5 MV Van de Graaff accelerator in Hungary have reported  > 6-sigma excess of e+e- pairs beyond the expectation of internal pair creation (IPC), in nuclear transitions of 8Be (M1), 4He (M0), and 12C (E1). These results are consistent with a new hypothetical particle with a mass of 16.84 MeV, dubbed X17- a protophobic,  spin-1, gauge boson,  that decays directly to a lepton pair. One such possibility is a 17 MeV dark photon. A new direct detection experiment to search for the X17 and other hidden sector particles via their e+e- decay, was recently approved at JLab. This experiment will use the magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle in the 3-60 MeV mass range. I will describe the ATOMKI results, motivate the connection to hidden sector particles, and highlight the new search experiment at JLab. I will also discuss some ideas for possible searches at TUNL/HIGS.

November 2, 2023

Stefan Bathe, Baruch College, CUNY and RIKEN Visiting Scientist

The Inaugural Run of the sPHENIX Experiment
 
After more than ten years in the making, the sPHENIX Experiment at RHIC has conducted its inaugural run earlier this year.  sPHENIX is the first new major experiment at RHIC in over 20 years.  Its mission is to study the QCD phenomena discovered at RHIC with unprecedented precision, with a focus on hard probes.  We will review the progress that has been made during this first year towards commissioning the new detector, outline the remaining challenges, and provide a glimpse at the physics capabilities of the experiment.
November 14, 2023

Steve Elliott, Los Alamos National Laboratory

 

Isomers and Dark Matter: 180mTa and 178mHf

180mTa is a rare nuclear isomer whose decay has never been observed with a half-life longer than 1019 years for beta and electron-capture decay channels. Its remarkably long lifetime is due to the large K-spin differences and small energy differences between the isomeric and lower energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter and K-spin violation. 178mHf is a high-energy isomer (half-life 31 years) that also may provide insight into dark matter. Although the existence of dark matter is well established, its nature is not well understood and constraints on the classic WIMP scenario have become restrictive. As a result, interest in a wider range of dark matter possibilities has increased. Isomers, with a possible exothermic reaction, are exciting targets for experiments testing specific dark matter models.

To study Ta, we repurposed the Majorana Demonstrator, an experimental search for the neutrinoless double beta decay of 76Ge using an array of high-purity germanium detectors, to search for the decay of 180mTa. Over 17 kilograms was installed within the ultra-low background detector array. For Hf, we exploited the existence of an isomer sample, produced 40 years ago to study possible applications of nuclear energy storage, to search for g-ray emission from excited states that might be populated by interaction with dark matter. This talk will describe the results of these two searches and their implications for dark matter.

November 16, 2023

Geon-Bo Kim, Lawrence Livermore National Laboratory

 

Magnetic Microcalorimeter and its Applications at LLNL

Magnetic microcalorimeter (MMC) is a cryogenic radiation and particle detector made of paramagnetic sensing materials and quantum magnetometers (SQUIDs, superconducting quantum interference devices). They are operated at tens of millikelvin temperatures and exhibit excellent energy resolution in radiation and particle detection. MMCs are currently being used in a wide variety of applications at the Lawrence Livermore National Laboratory (LLNL), including plutonium-based sterile neutrino search, development of diamond-based dark matter detectors, decay energy spectroscopy for high precision nuclear material analysis for international nuclear safeguards and rapid nuclear forensics, and improving 146Sm half-life for chronology of early solar system. This talk will provide an overview of how MMCs are utilized for various applications.

 

Spring 2023

Date Description

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.

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. 

 

Fall 2022

Date Description
October 13, 2022

Carlos Bertulani

Department of Physics and Astronomy, Texas A&M University - Commerce

Probing photonuclear reactions with heavy ions

Heavy ions provide strong electromagnetic fields that can be used to probe properties of interest in nuclear structure, nuclear astrophysics and particle physics. In this talk I will discuss new developments in understanding the role of the symmetry energy in the equation of state of nuclear matter, nuclear collective phenomena, QED and QCD processes, and other physics phenomena induced by photon-photon and photo-nuclear interactions in reactions with heavy ions.

October 20, 2022 

Johann Isaak

TU Darmstadt

Nuclear structure studies using photonuclear reactions with quasi-monoenergetic photon beams at HIγS

Photons provide a particular clean probe to study a variety of nuclear structure phenomena. Their interaction with the atomic nucleus is described by the electromagnetic interaction enabling the almost model-independent separation of the nuclear response from the details of the reaction mechanism.

In this talk, recent developments and experimental results obtained from photonuclear reaction studies with quasi-monoenergetic photon beams at HIγS are discussed in view of contradictory data sets when comparing data from real-photon scattering and particle-induced reactions. In addition, a model-independent approach is presented that allows the determination of photon strength functions in the photoabsorption and photon-emission channel in a single experiment testing the concept of the Brink-Axel hypothesis in the energy region below the neutron separation threshold.

November 3, 2022

Brad Sherrill

Michigan State University

Search for the Limits of Atomic Nuclei with the Facility for Rare Isotope Beams

Nuclear science attempts to understand strongly-interacting material. The atomic nucleus, which comes in perhaps 10,000 different varieties, is the most familiar example. Many aspects of atomic nuclei including the limits in terms of neutron and proton number are not well known. The Facility for Rare Isotope Beams, FRIB, will provide access to an unprecedented range of isotopes (the varieties) of the elements up to uranium. This is possible due to FRIB’s very high-power superconducting linear accelerator that can deliver 400 kW of beam power for all stable isotopes and FRIB’s efficient isotope production and also due to the efficient separation scheme employed. The talk will review our current understanding of the limits of nuclei and present resent results. The prospects for progress at FRIB will be presented. Some of the implications of our understanding of the limits will be presented.

November 10, 2022

Charlotte Van Hulse

University of Paris-Saclay and CNRS/IN2P3

Study of the hadron structure in ultra-peripheral collisions at the LHC

The internal hadron structure can be studied in lepton-hadron scattering and in hadron-hadron collisions. The former interaction offers the advantage of a clean, point-like probe.  The latter, in particular studied at the LHC, provides a complementary channel and the possibility to reach, with the currently existing or near-future planned facilities, higher energies and thus to study the hadron structure down to lower values of x-Bjorken.  An overview of measurements in ultra-peripheral collisions at the LHC, englobing exclusive processes as well as inclusive photoproduction and sensitive to the nucleon and nucleus structure, will be presented.  Where applicable parallels with measurements in lepton-hadron interactions will be highlighted.

 

Spring 2022

Date Description
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
March 31, 2022 Jon Engel
April 7, 2022 Aobo Li
April 14, 2022 Christian Illiadis
April 21, 2022 Ekaterina Korobkina
April 28, 2022 Spencer Axani
May 5, 2022 Walter Pettus
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
   

Fall 2021

Date Description
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