Neutron-induced background by an alpha-beam incident on a deuterium gas target and its implications for the study of the 2H(alpha,gamma)6Li reaction at LUNA

Abstract

The production of the stable isotope Li-6 in standard Big Bang nucleosynthesis has recently attracted much interest. Recent observations in metal-poor stars suggest that a cosmological Li-6 plateau may exist. If true, this plateau would come in addition to the well-known Spite plateau of Li-7 abundances and would point to a predominantly primordial origin of Li-6, contrary to the results of standard Big Bang nucleosynthesis calculations. Therefore, the nuclear physics underlying Big Bang Li-6 production must be revisited. The main production channel for Li-6 in the Big Bang is the 2H(alpha,gamma)6Li reaction. The present work reports on neutron-induced effects in a high-purity germanium detector that were encountered in a new study of this reaction. In the experiment, an α-beam from the underground accelerator LUNA in Gran Sasso, Italy, and a windowless deuterium gas target are used. A low neutron flux is induced by energetic deuterons from elastic scattering and, subsequently, the 2H(d,n)3He reaction. Due to the ultra-low laboratory neutron background at LUNA, the effect of this weak flux of 2-3 MeV neutrons on well-shielded high-purity germanium detectors has been studied in detail. Data have been taken at 280 and 400 keV alpha-beam energy and for comparison also using an americium-beryllium neutron source.

Submitted to EPJA; 13 pages, 8 figures

References in corpus (17)

• The Primordial Lithium Problem
• A probable stellar solution to the cosmological lithium discrepancy
• Particle physics catalysis of thermal Big Bang Nucleosynthesis
• Big Bang Nucleosynthesis as a Probe of New Physics
• LUNA: Nuclear Astrophysics Deep Underground
• 3He(alpha,gamma)7Be cross section at low energies
• Ultra-sensitive in-beam gamma-ray spectroscopy for nuclear astrophysics at LUNA
• High-energy break-up of 6Li as a tool to study the Big-Bang nucleosynthesis reaction 2H(alpha,gamma)6Li
• Feasibility of low energy radiative capture experiments at the LUNA underground accelerator facility
• ${}^6$Li Production by the Radiative Decay of Long-Lived Particles
• {Once more about astrophysical $S$ factor for the $\alpha +d\to {}^6\mathrm{Li}+\gamma$ reaction
• An actively vetoed Clover gamma-detector for nuclear astrophysics at LUNA
• 6Li/7Li estimates for metal-poor stars
• Neutron Inelastic Scattering Processes as Background for Double-Beta Decay Experiments
• Discrimination of gamma rays due to inelastic neutron scattering in AGATA
• Neutron Interactions as Seen by A Segmented Germanium Detector
• Lithium synthesis in microquasar accretion

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• Setup commissioning for an improved measurement of the D(p,gamma)3He cross section at Big Bang Nucleosynthesis energies
• First $\beta$-decay spectroscopy of ${}^{135}$In and new $\beta$-decay branches of ${}^{134}$In
• A new ultra low-level HPGe activity counting setup in the Felsenkeller shallow-underground laboratory