Nuclear Science Division Newsletter, July 2022

The Facility for Rare Isotope Beams (FRIB) officially began operations and started its user program in May. A ribbon-cutting ceremony was held May 2, 2022 to officially mark the “start of FRIB’s scientific mission” with U. S. Secretary of Energy Jennifer Granholm and the president of Michigan State University Samuel Stanley in attendance. The first FRIB experiment, E21062, ran from May 10-18, 2022 and studied the decays of rare isotopes produced following the fragmentation of a high-intensity (1 kW) ⁴⁸Ca primary beam. The exotic nuclei produced in these reactions were delivered to the center of the FRIB Decay Station Initiator (FDSi), which is a detector system designed to provide discovery potential for the decay of isotopes reaching towards the limit of stability at the neutron dripline. The FDSi detector system for the first FRIB measurement included charged particle, gamma-ray, and neutron detection systems.

The first FRIB experiment was led by spokesperson Heather Crawford (LBNL) and co-spokespersons Mitch Allmond (ORNL), Ben Crider (Mississippi State University), Robert Grzywacz (University of Tennessee Knoxville) and Vandana Tripathi (Florida State University). The team included over 50 participants from ten universities and national laboratories. While the initial beam intensity for this measurement was just 10% of that planned for the ultimate experiment, the preliminary results nonetheless show a number of isotopes with newly measured half-lives. See Figure 1. The  red line in the figure separates nuclei with known half-lives – to the left – from those with no literature value – on the right.

Analysis of the data is now underway, with involvement from across the collaboration. Stay tuned for the first set of publications!

A team from LBNL’s Applied Nuclear Physics program, in collaboration with scientists from Argonne National Laboratory, have been working to realize a city-scale multi-sensor testbed with which to explore new techniques in intelligent, networked sensing for radiological and nuclear detection. Figure 1 shows a prototype system installed at LBNL for evaluation. In June and July, four sensor systems will be deployed in Chicago. A full network of up to twenty systems is scheduled for completion by Spring 2023.

The detection, identification, and localization of illicit radiological and nuclear material continues to be a key component of non-proliferation and nuclear security efforts around the world. LBNL researchers have long been at the forefront of developing new detector systems and algorithms for these important applications. One place where advances in telecommunications, edge computing, and cloud computing technologies can have a significant impact on these efforts is the development of networked radiation detectors. Deploying multi-sensor systems at strategic locations in urban environments has the potential to provide persistent radiological/nuclear monitoring with a high probability of detecting mobile radiological sources or nuclear material. These concepts can be enhanced through the development of new networked detection capabilities including the integration of contextual sensors to aid in the interpretation of radiological measurements, algorithms that are able to adapt to changing environmental conditions, and the fusion of data from across the network of sensors.

The LBNL-led ‘Platforms and Algorithms for Networked Detection and Analysis’ project (PANDA) and the Argonne ‘Domain Aware Waggle Network’ project (DAWN) have developed unique sensor systems that combine large-volume gamma-ray detectors with a suite of contextual sensors including video, Lidar, meteorological sensors, edge computers, and network connectivity.

Figure 2 shows an engineering drawing of a PANDA-DAWN sensor system.

In addition to developing these new sensor systems, the LBNL team has also been developing and implementing advanced algorithms for radiological anomaly detection, contextual sensor processing, and data fusion. The data collected with the PANDA-DAWN network, along with advances in algorithms, system design, and network infrastructure developed through these projects, will pave the way for next-generation radiological detection in the field and serve as a model and springboard for other sensing modalities such as chemical, biological, and environmental.

The PANDA project is led by Ren Cooper. Nico Abgrall, Mark Bandstra, Dan Hellfeld, Tenzing Joshi, Victor Negut, Dan Parker, Brian Quiter, Emil Rofors, and Marco Salathe have all made significant contributions. The project is supported by the Department of Energy, National Nuclear Security Administration, Office of Defense Nuclear Nonproliferation Research and Development.

Electron scattering is a powerful tool for studying hadron and nuclear structure.  In particular, one‑photon (OPE) and two‑photon exchange (TPE) mechanisms play an important role in the scattering of electrons on nuclei. The OPE mechanism is the dominant interaction, while the TPE is a small but sometimes critical contribution. In terms of the state of the art, the OPE has been well measured and is well understood but the TPE is not.

A simple but extremely powerful tool that experimentalists can use to refine our knowledge of the TPE mechanism is “single-proton knockout” which, as the name implies, involves knocking one and only one proton out of a target nucleus without interacting with the rest of the nucleus or creating new particles. Single-proton knockout is used to study the momentum distributions of protons in the nucleus. To make precision measurements of these distributions, the elastic electron-proton interaction must be well understood. This means having a precise knowledge of the proton electromagnetic form factors which encode the spatial distribution of charge and magnetization of the proton and, ultimately, determine the e-p elastic scattering cross section [1].

With the completion of the 12-GeV upgrade at JLab, a new generation of precision nuclear structure measurements have been performed that are capable of exploring new kinematic regions. JLab E12-07-108 was one of the first experiments after the completion of the upgrade, and the experiment made an extensive set of precision elastic e-p scattering measurements for momentum transfers from 2 to 16 GeV². These data provide an improved understanding of the proton form factors and electromagnetic structure, the input needed for new proton knockout measurements, and strong experimental constraints on the impact of higher-order two-photon exchange (TPE) corrections in high-energy electron scattering. See Figure 1.

To effectively extract the elusive TPE contributions from other effects in the data, the team examined the impact of improved radiative corrections that go beyond the OPE. They found that these improved procedures reduced the discrepancy associated with TPE corrections in prior measurements by one-third but still require TPE contributions with a 4% angular dependence for Q² from 6 to 16 GeV² [2]. See Figure 2.

[1] “Review of two-photon exchange in electron scattering,” J. Arrington, P. G. Blunden, W. Melnitchouk, Prog. Part. Nucl. Phys. 66 (2011) 782

[2] “Form factors and two-photon exchange in high-energy elastic electron-proton scattering,” M. E. Christy, et al., Phys. Rev. Lett. 128 (2022) 102002.

The Electron Ion Collider (EIC) will be the next major facility in Nuclear Physics and LBNL’s Relativistic Nuclear Collisions (RNC) group is playing a leading role in its development. The EIC will be constructed at Brookhaven National Laboratory (BNL) and begin data taking in the 2030s, enabling detailed studies of protons, neutrons and atomic nuclei. Key science questions the EIC will address include: How do the nucleonic properties such as mass and spin emerge from partons and their underlying interactions? How do the quark-gluon interactions create nuclear binding? What are the properties of the dense gluonic matter that exists deep inside heavy nuclei?

While the EIC complex will have two interaction regions with the potential to host two large-scale detectors, the initial scope of the EIC construction project includes only one day-one detector.  In December 2021, BNL solicited proposals from collaborations interested in participating in the program and three proposals were received:  ECCE, ATHENA, and CORE. The proposals were reviewed by the Detector Proposal Advisory Panel (DPAP) in March and a primary recommendation of the DPAP was that each of these collaborations was too small for the final task and they encouraged all three collaborations to merge into a single “Detector One” collaboration. 

LBNL took a major role in the design, optimization, and tracking implementation for the silicon tracking and vertexing system in ATHENA, and in the optimization of the far-forward detector systems.  It is likely that a derivative of these systems will be used in the new detector.  In addition, the DPAP endorsed the re-use of the existing BaBar magnet (1.5 Tesla) and the recently completed sPHENIX hadronic calorimeter as proposed by the ECCE collaboration.  Additional detector elements are expected to be designed and optimized according to the experience retained by the three former collaborations. 

The RNC group took a major role in developing the ATHENA concept and proposal. Barbara Jacak was a member of the ATHENA steering committee and proposal writing committee, Ernst Sichtermann was chair of the Institutional Board, and John Arrington, Spencer Klein & Ernst were conveners for different detector and physics working groups.  Extensive simulations were carried out by Rey Cruz Torres, Shujie Li, Wenqing Fan, and other RNC postdocs, students and staff members. Going forward, RNC will be a major contributor to the final design and construction of Detector One.

Best Practices for Hybrid Meetings

As we enter a new phase in the pandemic when more and more people are able to safely work together at the lab, our use of fully remote meetings may be coming to a close. Now many of us find ourselves in the situation of holding meetings with in-person participants as well as remote participants  —  so-called hybrid meetings.

At the first hybrid NSD staff meeting on May 3rd 2022, we discussed and demonstrated how we can implement the principles of IDEA in this new context. We emphasized that at stake are both inclusion — that all attendees are able to access and participate in the meeting — and equity — that all are respected and treated fairly in the process. Important steps to take include testing the technology beforehand so that both in-person and remote attendees can hear and see presentations, and assigning a specific “Zoom monitor” who can facilitate communication between in-person and remote participants. Also important is in being clear about how the meeting will run, such as by circulating an agenda in advance and by laying ground rules for how in-person and remote attendees can interact with speakers and one another.

Other ideas generated from our discussion on May 3^rd are that, if possible, it is helpful both to have a camera on the in-person attendees so the remote participants can see the in-person attendees, and to have a secondary display in the room so that the videos of remote participants can be shown. In addition, when in-room participants ask questions or make comments, it was suggested that the person or host in the room identify the person who asked the question for the benefit of the remote participants. Thanks for everyone’s insights and wishing us all the best in this new phase of work!

Recent DEI topics @ NSD Staff Meetings

May 31, 2022 – FAIR Office overview
May 17, 2022 – Bias and Its Extremes
May 3, 2022 – Hybrid Meetings with Zoom – Best Practices
April 19, 2022 – Autism Awareness Month
April 5, 2022 – Utilizing URM Targeted Job Posting Boards
March 22, 2022 – The General Sciences Mentoring Program

Luminary Cards 

You may recognize your co-workers with a Luminary Card for any action fostering inclusion, diversity, equity, and accountability within our LBNL community.  The following people received a Luminary Card this quarter:

Larry Phair, Xin-Nian Wang, Joselyn Delgado, Jenn Tang, Morgan Morse, Cameron Geddes, Polly Arnold, Jayson Vavrek, Paul Adams