Annual Continuation And Progress Report For Low-Energy Nuclear Physics Research At Lawrence Livermore National Laboratory

Technical Report · Tue Oct 27 00:00:00 EDT 2015

DOI:https://doi.org/10.2172/1239223· OSTI ID:1239223

Scielzo, N. D. ^[1]; Wu, C. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

(I)In this project, the Beta-­decay Paul Trap, an open-­geometry RFQ ion trap that can be instrumented with sophisticated radiation detection arrays, is used for precision β-­decay studies. Measurements of β-­decay angular correlations, which are sensitive to exotic particles and other phenomena beyond the Standard Model (SM) of particle physics that may occur at the TeV-­energy scale, are being performed by taking advantage of the favorable properties of the mirror ⁸Li and ⁸B β^± decays and the benefits afforded by using trapped ions. By detecting the β and two α particles emitted in these decays, the complete kinematics can be reconstructed. This allows a simultaneous measurement of the β-­n, β-­n-­α, and β-α correlations and a determination of the neutrino energy and momentum event by event. In addition, the ⁸B neutrino spectrum, of great interest in solar neutrino oscillation studies, can be determined in a new way. Beta-­delayed neutron spectroscopy is also being performed on neutron-­rich isotopes by studying the β-­decay recoil ions that emerge from the trap with high efficiency, good energy resolution, and practically no backgrounds. This novel technique is being used to study isotopes of mass-­number A~130 in the vicinity of the N=82 neutron magic number to help understand the rapid neutron-­capture process (r-­process) that creates many of the heavy isotopes observed in the cosmos. (II)A year-long CHICO2 campaign at ANL/ATLAS together with GRETINA included a total of 10 experiments, seven with the radioactive beams from CARIBU and three with stable beams, with 82 researchers involved from 27 institutions worldwide. CHICO2 performed flawlessly during this long campaign with achieved position resolution matching to that of GRETINA, which greatly enhances the sensitivity in the study of nuclear γ-­ray spectroscopy. This can be demonstrated in our results on ¹⁴⁴Ba and ¹⁴⁶Ba where the octupole deformation is evident from the measured B(E3; 3^-→0⁺) strengths that significantly greater than the theoretical predictions. We anticipate that CHICO2 will continue to be a viable charged-­particle detector for the research need of the low-­energy nuclear physics community.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC52-07NA27344
• OSTI ID: 1239223
• Report Number(s): LLNL-TR-678634; TRN: US1600561
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
RESEARCH PROGRAMS
BETA DECAY
BETA-DELAYED NEUTRONS
LAWRENCE LIVERMORE NATIONAL LABORATORY
BORON 8
ANGULAR CORRELATION
ALPHA PARTICLES
BETA PARTICLES
ENERGY RESOLUTION
NUCLEAR PHYSICS
BARIUM 144
BARIUM 146
INDIUM 130
LITHIUM 8
NEUTRON-RICH ISOTOPES
PROGRESS REPORT
ANL
R PROCESS
IONS
TRAPS
OCTUPOLES
NEUTRON SPECTROSCOPY
ACCURACY
NUCLEAR DEFORMATION
EFFICIENCY
MIRROR NUCLEI
RECOILS
SENSITIVITY
SPECTRA
TRAPPING
E3-TRANSITIONS
BRANCHING RATIO