We investigated the feasibility of establishing a state-of-the-art research program by bringing together the nuclear-science expertise of the Lawrence Livermore National Laboratory and the Soreq Nuclear Research Center in Israel. We concluded that there are three promising research topics that would benefit both laboratories and would take advantage of the capabilities available at the Soreq Applied Research Accelerator Facility, specifically state-of-the-art light-ion and neutron beams for research in low-energy nuclear physics. The three research topics are (1) precision beta-decay studies to test the Standard Model of particle physics and the solar neutrino flux, (2) direct and indirect determinations of (n,2n) reactions required as benchmarks for nuclear data needs, and (3) direct measurements of neutron-capture cross sections of importance to nuclear astrophysics. Our research was instrumental in enabling scientists of the two facilities to work together on these topics to determine feasible goals for future collaborations.
At the Soreq Nuclear Research Center (SNRC), the Soreq Applied Research Accelerator Facility (SARAF) provides light-ion and neutron beams for research in low-energy nuclear physics (Mardor et al. 2018). The first half of this facility, SARAF-I, was built primarily to test novel technologies for generating the highest-intensity beams and will run a campaign of science experiments until the end of 2019. The facility provides neutron beams with energies up to 20 MeV using a lithium fluoride thick target (Hirsh et al. 2012) and with an energy distribution similar to that of the 30-keV Maxwellian-averaged flux distribution, which is of interest for slow neutron-capture process (s-process) nucleosynthesis (whereby repeated neutron-capture reactions and beta decays build up elements over thousands of years, mostly in asymptotic giant branch stars [Tessler et al. 2015]). The facility is poised to deliver beams of radioactive noble gases (such as 6He) and a variety of unstable neon isotopes that can be delivered to experimental end-user stations (Marder et al. 2018). The second half of the facility, SARAF-II, is anticipated to come online in approximately five years and will serve as a user facility delivering neutron and light-ion beams, in some cases at intensities surpassing those of any other facility in the world.
At Lawrence Livermore National Laboratory, we are interested in a variety of experiments to study nuclear beta decay and measure nuclear-reaction cross sections that are achievable with these types of beams. A collaborative effort between Livermore and SNRC researchers could result in high-impact programs that use the capabilities of SARAF. During this study, we attempted to lay the groundwork for just such a collaboration by performing initial experimental investigations on three topics:
Our research began the process of establishing strong partnerships between nuclear science researchers at Livermore and SNRC. We envision these partnerships opening up new opportunities to perform measurements of interest to Livermore’s future nuclear science missions. A strong collaboration with researchers at SNRC and Israeli universities can provide access to the state-of-the-art light-ion and neutron beams available at SARAF that are currently of limited availability or are not available in the U.S. Livermore researchers can also benefit from the expertise developed in Israel for carrying out low-energy nuclear science experiments.
The SARAF facility at SNRC in Israel has begun delivering high-intensity neutron and light-ion beams that would benefit a variety of nuclear-science programs, ranging from studies of nuclear beta decay to the determination of neutron-induced reaction cross sections. We worked with SNRC to determine the feasibility of performing these types of measurements at SARAF. These efforts led to the planning and design of an experiment to measure the 23Ne beta-decay transition intensities, a novel method to calibrate silicon detectors (which resulted in a joint LLNL-SNRC publication), as well as the initiation of a Livermore-SNRC collaborative effort to investigate neutron-induced reactions using surrogate-reach approaches at Texas A&M University and direct-measurement approaches at SARAF. We hope to obtain support to carry out experiments at SARAF to measure the 23Ne beta-decay transition intensities and to utilize the high-intensity neutron beams to directly measure neutron-induced reaction cross sections. We envision that there will be a great benefit to continuing to foster this collaboration so that Livermore will be well-positioned to use the unique capabilities that will become available when SARAF-II comes online in the coming years.
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——— . 2018. "The Use of Cosmic-Ray Muons in the Energy Calibration of the Beta-decay Paul Trap Silicon-Detector Array." Nuclear Instruments and Methods in Physics Research A 887, 122–127. oi: 10.1016/j.nima.2018.01.021.
Mardor, I., et al. 2018. "The Soreq Applied Research Accelerator Facility (SARAF): Overview, Research Programs and Future Plans." European Physics Journal A 54, 1–32.
Tessler, M., et al. 2015. "Stellar 30-keV Neutron Capture in 94,96Zr and the 90Zr(γ,η)89Zr Photonuclear Reaction with a High-Power Liquid-Lithium Target." Physics Letters B 751, 418–422. doi: 10.1016/j.physletb.2015.10.058.
Hirsh, T. Y., et al. 2018. "The Use of Cosmic-Ray Muons in the Energy Calibration of the Beta-Decay Paul Trap Silicon-Detector Array." Nuclear Instruments and Methods in Physics Research A 887, 122–127. LLNL-JRNL-732612.