In this issue:
- Director’s Corner
- Coherent Photoproduction Probes Kaon Couplings
- Half-life of 71Ge and the Gallium Anomaly
- GRETA Makes Its First Move
- Researchers Demonstrate Robotic Inspection for Nuclear Safeguards
- NSD Hosts 15th Workshop on Critical Point Onset of Deconfinement (CPOD2024)
- The Nuclear Science Division welcomes a cohort of summer interns
- Fragments
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Director’s Corner
The goats are back at the Lab, so it must be summer. It is also the time to welcome nine summer interns who are working with teams across the Division.
There was much to celebrate since the last newsletter. It was a pleasure to join, together with several NSD members, the flag raising ceremony to celebrate Pride Month. An important reminder of our commitment to fostering a workplace culture where everyone feels welcome and valued. We also celebrate several NSD members who were recognized for their outstanding work. Congratulations to Wick Haxton, Erich Leistenschneider, Gabriel Orebi Gann, and Xin-Nian Wang on their respective well deserved awards (see Fragment for more details).
On the science side, we can celebrate the breakthrough by our Heavy Element team, who in collaboration with their international partners succeeded to produce two events of Element 116 (livermorium) by bombarding a plutonium target with a titanium-50 beam at the 88-Inch Cyclotron. Based on the measured production rate the search for new Element 120 using titanium beam seems feasible.
In this issue of the NSD Newsletter we are featuring recent physics results from ALICE, led by NSD scientists, that investigate the coherent photoproduction of pairs of kaons in ultra-peripheral collisions (UPCs) of relativistic lead nuclei, which for the first time gave access to the photon-kaon coupling strength. We also learn about a remarkable measurement of the 71Ge half-life, which rules out potential explanation of the so-called “gallium anomaly”, leaving the door open for potentially more physics beyond-the-standard model in the neutrino sector. Another exciting development we learn about, is how machine learning methods, automation, and robotics are being used for nuclear safeguards applications. Finally, the GRETA project has achieved another major milestone by safely completing the challenging move of the main mechanical structures from the 88-Inch high bay to the laboratory ‘K-area’ space in the basement level of Bldg. 88 where the final assembly, systems integration and testing will take place. The move was a real team effort of the LBNL riggers with support of the 88-Inch mechanical crew. Congratulations. The pictures in this issue of the newsletter only tell part of the story.
Overall, it is fantastic to see the progress and celebrate these achievements, the recognition of our people, and the commitment to the lab’s stewardship values and IDEA principles. Wishing everyone an enjoyable summer.
Sincerely,
Figure 1: The Berkeley Lab community showed its support and joined members of the Lambda Alliance employee resource group, for a flag-raising ceremony to kick off Pride Month. -
Coherent Photoproduction Probes Kaon Couplings
Photons are important probes because they couple to all charged particles. The coupling strength is determined by measuring photon splitting into particle-antiparticle pairs. These strengths have been previously measured for electrons, for quarks, and for one type of meson – the pion. In a paper published in Physical Review Letters,, the ALICE Collaboration reports on the first measurement of coherent photoproduction of a charged kaon pair (K+K–). The data allows us to compare the behavior of heavier mesons, containing strange quarks (kaons) with lighter mesons composed only of up and down quarks (pions). The study found that the coupling of kaons and pions was comparable, after accounting for the large mass difference.
The data came from ultra-peripheral collisions (UPCs) of relativistic lead nuclei, produced at CERNs Large Hadron Collider (LHC). In UPCs, the two nuclei do not physically collide, but interact at long range, via photon exchange. A photon from one nucleus can fluctuate to a virtual (evanescent) K+K– meson pair (particle and antiparticle) and then one of the kaons can scatter elastically (and coherently) from the other nucleus, emerging as a real K+K– pair. The final state kaon pairs have a very low transverse momentum (pT), as is seen in the figure. This showed that the kaon-nucleus scattering was coherent (elastic), with coupling to all of the protons and neutrons in the target. The analysts – the Relativistic Nuclear Collision program’s Minjung Kijm, Spencer Klein and Mateusz Ploskon – applied stringent particle identification cuts to select a pure sample of kaon pairs.
With that, the ALICE collaboration found that the couplings were similar to those of pions (with only ¼ the mass), after adjustment for the different meson mass, showing that different mesons behave similarly, despite difference in quark content and mass. Looking ahead, with the upgraded ALICE data acquisition system, during LHC Runs 3 and 4, ALICE should collect more than 100 times more UPC events than were used here, allowing for precision measurements of kaon pairs, and also allowing us to look at pairs of heavier mesons, and even baryon pairs. A more comprehensive set of results will allow us to study trends based on meson masses and other properties.
Figure 1: The transverse momentum (pT, left) and daikon mass (right) spectra for the ALICE event sample. The pT spectrum shows that the production is coherent over the entire target. The production rate is above expectations from the ϕ meson alone.
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Half-life of 71Ge and the Gallium Anomaly
Experiments detecting neutrinos via the (νe, e−) reaction on 71Ga systematically observe lower than expected interaction rates. This unexplained phenomenon, demonstrated most recently by the BEST experiment with a high statistical significance [1], is known as the “gallium anomaly.” The discrepancy is so far unexplained and could be an exciting potential indicator of new neutrino physics [2,3]. However, it has been pointed out that a larger value of the half-life of 71Ge (12.5 – 13.5 days vs. 11.43 days measured in 1985 [4,5]) used to compute the neutrino cross sections on 71Ga could reduce or eliminate the anomaly [6] and that new measurements were needed [7].
This question is thoroughly addressed in E.B. Norman et al.’s new paper, “Half-life of 71Ge and the gallium anomaly,” published on May 30th 2024 in Physical Review C [8] as an Editor’s Suggestion. The authors from UC Berkeley, LBNL, and LLNL carried out three separate high-precision spectral measurements with planar HPGe detectors at the LLNL Nuclear Counting Facility: the rate of electron capture decay of 71Ge to 71Ga was measured directly, as well as in relation to 57Co and 55Fe radioactive standards. In the latter technique, fitting the ratio of the 71Ge activity to that of the well-known standard provides a measure of the difference in their decay rates, while eliminating many systematic effects. Figs. 2 and 3 show the spectra and the decay rate fits, respectively.
Both germanium oxide and crystalline High Purity germanium samples were utilized, with the latter prepared at LBNL’s Semiconductor Detector Laboratory (SDL) by NSD Research Scientist Alexey Drobizhev. The material was irradiated in the graphite reflector of the McClellan Nuclear Research Center (MNRC) TRIGA reactor at UC Davis to create the relatively short-lived 71Ge isotope. The samples were counted continuously for over two months at LLNL. NSD’s Yury Kolomensky contributed to the high quality statistical analysis featured in this paper.
The final result gives a 71Ge half-life of 11.468 ± 0.008 days—fully consistent with prior measurements (Fig. 1), while significantly more precise. Importantly, it rules out the longer half-life values that would be needed to explain the neutrino event deficit seen by gallium experiments. Thus, the gallium anomaly remains a mystery with potential for more beyond-the-standard model physics in the neutrino sector.
Figure 1: Results from all reported measurements of the 71Ge half- life since 1985 [8]. Figure 2: Relevant portions of measured spectra, after 24h of counting. Top: 71Ge; middle: 71Ge + 55Fe; bottom: 71Ge + 57Co [8]. Figure 3: Decay curves from three measurements of the 71Ge half-life. Top: Ga K-shell x-rays from the standalone 71Ge source; middle: the ratio of Ga to Mn K-shell x-rays from 71Ge + 55Fe; bottom: ratio of Ga K-shell x-rays to 14-keV γ-rays from 71Ge + 57Co. Left and right plots represent two different analyses [8]. References
[1] V. V. Barinov et al., Results from the Baksan experiment on sterile transitions (BEST), Phys. Rev. Lett. 128, 232501 (2022) DOI: https://doi.org/10.1103/PhysRevLett.128.232501
[2] J. N. Abdurashitov et al., Measurement of the response of a Ga solar neutrino experiment to neutrinos from a 37Ar source, Phys. Rev. C 73, 045805 (2006) DOI: https://doi.org/10.1103/PhysRevC.73.045805
[3] M. Laveder, Unbound neutrino roadmaps, Nucl. Phys. B 168, 344 (2007) DOI: https://doi.org/10.1016/j.nuclphysbps.2007.02.037
[4] B. Singh and J. Chen, Nuclear structure and decay data for A = 71 isobars, Nucl. Data Sheets 188, 1 (2023) DOI: https://doi.org/10.1016/j.nds.2023.02.001
[5] W. Hampel and L. P. Remsberg, Half-Life of 71Ge, Phys. Rev. C 31, 666 (1985) DOI: https://doi.org/10.1103/PhysRevC.31.666
[6] C. Giunti, Y. F. Li, C. A. Ternes, and Z. Xin, Inspection of the detection cross section dependence of the gallium anomaly, Phys. Lett. B 842, 137983 (2023) DOI: https://doi.org/10.1016/j.physletb.2023.137983
[7] S. R. Elliott, V. Gavrin, and W. Haxton, The gallium anomaly, arXiv:2306.03299v1 DOI: https://doi.org/10.48550/arXiv.2306.03299
[8] E.B. Norman et al. “Half-life of 71Ge and the gallium anomaly.” Phys. Rev. C 109, 055501 (2024) DOI: https://doi.org/10.1103/PhysRevC.109.055501 -
GRETA Makes Its First Move
In May, the Gamma-Ray Energy Tracking Array (GRETA) project achieved a significant milestone with the move of the two mechanical assemblies that comprise the array structure. These structures moved from their assembly location in the high-bay of Bldg. 88 to the laboratory ‘K-area’ space where they will be integrated with the other technical systems of GRETA in the coming months.
This move happened in the beginning of May over the course of two days. Following detailed planning over several months with the LBNL rigging team led by Curt Howard and Taylor Silva, including the procurement of dedicated gantry cranes and measuring far more than twice, the move started bright and early at 8am on May 7, 2024. The planning more than paid off with an impressively smooth move of these >6000 lb assemblies. Figures 1 through 5 show a story-board of the move of the first structure. A lift onto a flatbed truck in the Bldg. 88 high-bay started the action, then travel around the building followed. A truck-mounted 50-ton crane was used to lift the structures off the flat-bed and to perform the delicate drop through the double doors into the K-area. The GRETA structures were then rolled into position alongside their final places and a coordinated lift and slide of the structures using the dedicated pair of gantry cranes completed the move on to the prepared plates. The pair of installed structures is shown in Figure 6. The LBNL riggers with support from the local Bldg. 88 mechanical crew, in particular John Garcia and Brian Bell, executed this complex move perfectly, twice.
Over the coming summer months, the GRETA structures will be built up with motion and cooling systems, aligned, and then load tested. Six GRETA Quad Module HPGe detectors will be installed in the August-September timeframe to demonstrate the performance of the array prior to completion of the DOE project and its ultimate delivery to the Facility for Rare Isotope Beams (FRIB) for scientific operation.
NSD scientist Paul Fallon is the GRETA Project Director and Heather Crawford is the manager for GRETA System Assembly, with staff from NSD and Engineering Division at LBNL, and from ANL, ORNL and FRIB on the project team.
Figure 1: The first half assembly of the GRETA mechanical structure being craned in the Bldg. 88 high-bay onto a flatbed truck for transport around the building.
Figure 2: The mechanical structure loaded on the flatbed and ready to roll with NSD DSC Jeff Bramble looking on.
Figure 3: The first half assembly staged on the west side of Bldg. 88 and ready for craning off the truck and into the K-area.
Figure 4: The first half assembly being craned down and through the double doors to the K-area at Bldg. 88. Figure 5: The first of the two GRETA mechanical assemblies being slid over on dedicated gantry cranes onto the prepared mounting surface.
Figure 6: The final pair of installed GRETA mechanical assemblies in the K-area at Bldg. 88.
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Researchers Demonstrate Robotic Inspection for Nuclear Safeguards
Researchers from NSD’s Applied Nuclear Physics Program recently visited the Nevada National Security Site (NNSS) to perform data collections in support of two projects focused on using computer vision technology to automatically identify nuclear material containers. The Container Counting project has developed software that analyzes camera images to automatically locate specific instances of nuclear material containers within a three-dimensional model. The Inventory Verification through Detectors on Robotic Inspection Platforms (IV-DRIP) project has begun leveraging the products from the Container Counting project and coupling them with radiological measurements and robotic autonomy.
The primary goal of the NNSS visit was to acquire data to validate the counting and container-type classification techniques for the Container Counting project, and to collect data for inventory verification with nuclear radiation mapping, both in handheld mode and on robotic platforms (mainly Unmanned Aerial Systems (UAS) and Boston Dynamics’ quadruped robot SPOT dog). The data collection was performed at container storage facilities and the low level nuclear waste facility.
The team utilized machine learning to perform object recognition and enable the robotic systems to autonomously navigate to, and investigate, radiation sources in the nuclear material containers. The two platforms were mounted with ANP-developed sensor systems referred to as Localization And Mapping Platforms (LAMPs) [1], allowing for precise detection of radioactive materials within a given area. The team’s visit to NNSS not only enhanced existing measurement capabilities but also demonstrated the effectiveness of automation in nuclear safeguards scenarios. The team looks forward to further advancements and continued collaboration with NNSS in the future.
The Container Counting and IV-DRIP projects are supported by the Department of Energy National Nuclear Security Administration (NNSA), Defense Nuclear Nonproliferation Research and Development (DNN R&D) Nuclear Safeguards portfolio. The Container Counting and IV-DRIP projects are led by Marco Salathe and Brian Quiter, respectively. Marco Salathe, Brian Quiter, Karthika Balan, and Emil Rofors took part in the measurement campaign at NNSS.
Figure 1: ANP researcher Karthika Balan operating a SPOT robot dog equipped with an ANP-developed multi-sensor system.
Figure 2: A multi-sensor radiation detection system mounted on a Unmanned Aerial System surveys a stack of containers.
References
[1] R. Pavlovsky et al., 3-D Radiation Mapping in Real-time with the Localization and Mapping Platform from Unmanned Aerial Systems and Man-portable Configurations, arXiV:1901.05038 (2018)
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NSD Hosts 15th Workshop on Critical Point Onset of Deconfinement (CPOD2024)
In May, NSD hosted the 15th Workshop on Critical Point and Onset of Deconfinement (CPOD2024) at LBNL. CPOD is a series of international meetings which focus on the physics of the QCD phase structure in high-energy nuclear collisions, especially in the region of high baryon density where a possible phase transition and a critical point are conjectured to be located.
A total of 95 participants enjoyed an exciting scientific program that included experimental and theoretical topics. Many experimental results were reported by international collaborations including ALICE at CERN, HADES at GSI, SHIAN(NA61) at SPS and STAR at BNL. The STAR experiment released the awaited new results on higher moments of the proton and anti-proton distributions from the RHIC beam energy scan phase II. The proton(anti-proton) high order correlations are believed to be sensitive to the QCD critical point. At the center of collision energy of 20 GeV, the experiment observed a 4-5sigma deviation of the data from known non-critical model calculations. The data points to the change of structure of the medium created in the heavy-ion collisions. The new results have stimulated engaged discussions during the workshop and on the internet.
Theorists also presented predictions on the location of the QCD critical point. Calculations from Lattice Gauge Theory, Functional Method, Holographic and Thermodynamic approaches were presented and, interestingly, all results point to the high baryon density regions around the baryon chemical potential of mu_B ~ 600 MeV and the temperature of T ~ 100 MeV. Recent theoretical progress regarding the inner structure of compact stars and its relation to high-energy nuclear collisions are also discussed in the meeting.NSD scientists Xin Dong, Volker Koch, Grazyna Odynier, and Nu Xu were the local organizers of the workshop.
Figure 1. Attendees at the CPOD2024 workshop hosted at LBNL. -
Inclusion, Diversity, Equity and Accountability Moments
The Nuclear Science Division welcomes a cohort of summer interns.
The summer is upon us, and with the longer daylight hours, NSD has welcomed a new cohort of summer interns. This year, the division is hosting nine interns who come from universities all across the country and are working on projects in the 88-inch Cyclotron, Neutrinos, Applied Nuclear Physics, and Low Energy programs.
Six of the summer students are sponsored by the underGraduate Research Educational Academic Traineeships in Nuclear Science (GREAT-NS) program, an outreach initiative funded by the DOE Office of Science (now the RENEW programs), and run by a collaboration of NSD staff. Others are participating in the DOE Office of Science’s Science Undergraduate Laboratory Internships (SULI) and the National Nuclear Security Administration’s Minority Serving Institutions Internship Program (MSIIP).
At a recent all-hands staff meeting we also heard a talk from Faith Dukes, who is the director of LBL’s K-12 STEM Education Programs office. She gave us tips for working with high school interns, such as what to expect of their educational profile, what software platforms they may be familiar with, and the need to communicate clear boundaries and expectations. And that to help them learn, we should allow them to work through hard problems while providing appropriate encouragement.
Best of luck to our summer students, we hope this summer is an inspiring and formative time. And for the staff, be sure to introduce yourselves and welcome our interns!
Figure 1: Last summer’s GREAT-NS students and their mentors. -
Fragments
Xin-Nian Wang, a Senior Scientist in NSD’s Theory program has been awarded a prestigious 2024 Humboldt Research Award in recognition of his academic record. Xin-Nian plans to use this award to continue collaborative research with physicists at Goethe-Universität Frankfurt am Main and other institutes in Germany. Further details can be found here.
NSD Faculty Scientist Gabriel Orebi Gann was awarded the 2024 Instrumentation Early Career Award from the International Committee for Future Accelerators (ICFA). Gabriel was presented with this award at the 2024 Pisa Meeting on Advanced Detectors in La Biodola, Isola d’Elba. Further details can be found here.
Wick Haxton, a Faculty Senior Scientist in NSD’s Theory program was recently elected to the American Philosophical Society. More information can be found here.
Erich Leistenschneider, a Staff Scientist in the Accelerator-Based Low Energy Research Program was selected as an award recipient for the 2024 Facility for Rare Isotope Beams (FRIB) Visiting Scholar Program for Experimental Science. This award acknowledges Erich’s outstanding record and potential impact on the FRIB science program. Further details can be found here.
Several graduate students who performed their research in NSD, or under the guidance of NSD staff, recently graduated with PhDs. Congratulations to Kalie Knecht (PhD, Nuclear Engineering), Jaewon Lee (PhD, Nuclear Engineering), Kenneth Vetter (PhD, Physics), Max Smiley (PhD Physics), Yang Lyu (PhD, Physics), and Edward Callaghan (PhD Physics).
Yukiya Saito, a former graduate student at the University of British Columbia who was co-supervised by NSD Division Director Reiner Kruecken has been awarded the 2023-2024 DNP PhD Thesis Prize by The Division of Nuclear Physics (DNP) of the Canadian Association of Physicists (CAP) for his thesis is entitled Development of Statistical Tools for Studies of the Rapid Neutron Capture Process.
NSD bids farewell to Zuting Lui, Kai Vetter, Xin-Nian Wang, and Don Gunter who all retired from LBNL in June. Thank you Ting, Kai, Xin-Nian, and Don for your many years of outstanding service!
We welcome new hires Corrigan Appleton (Postdoctoral Researcher), Mathis Wiedeking (Staff Scientist), Mark Regis (Electrical Engineering Associate), Rita Sadek (Postdoctoral Researcher), Javier Caravaca (Staff Scientist), David Konyndyk (Sr. Scientific Engineering Associate), Rachel Williams (Administrative Assistant), and Vance Siebert (Sr. Resource Analyst).
Tom Gallant has taken on the position of Division Deputy, Operations for the Nuclear Science Division. Congratulations on the new role, Tom!
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