ICF plasma based measurements of the T + ⁴He cross section

Inertial Confinement Fusion (ICF) implosions provide a relatively new platform for studying nuclear astrophysics. Unlike beam-target accelerator measurements, nuclear reactions occurring in these implosion experiments are a direct surrogate for astrophysical systems as the reactions occur at comparable plasma conditions. The tritium (T) + 4He reaction is important for big-bang nucleosynthesis (BBN) production of 7Li which has a notable abundance anomaly. Observations of metal-poor halo stars [1] show approximately one third of the 7Li abundance from predictions that match the abundance inferred from the cosmic microwave background. [2] The important energy range for BBN is a center of mass energy (Ecm) between 60-160 keV [3], corresponding to a range in temperature of 13 − 50 keV. The lower end of this range can be easily studied with implosions conducted at ICF facilities. The T + 4He reaction produces 7Li and a 2.4 MeV gamma, the latter of which can be measured using gamma detectors based on the Cherenkov mechanism. Experiments conducted at the OMEGA laser facility are described along with preliminary results. This research can potentially impact the BBN modeling community by improving confidence in the reaction rate at relevant energies.

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[2] M. Tegmark et al. (SDSS Collaboration), Cosmological parameters from sdss and wmap, Phys. Rev. D, 69, 103501 (2004).

[3] S. Burles et al., Sharpening the predictions of big-bang nucleosynthesis, Phys. Rev. Lett., 82, 4176 (1999).