Measurement of the $^7$Li($\gamma$,t)$^4$He reaction between 4 and 11 MeV*

The discrepancy in the primordial $^7$Li abundance, as derived from stellar observations and nucleosynthesis calculations at WMAP baryonic density, is sensitive to alpha capture rates on $^3$He and $^3$H. The $^3$He($\alpha$,$\gamma$)$^7$Be reaction has been well studied over a wide range of energies, but for $^3$H($\alpha$,$\gamma$)$^7$Li discrepancies exist in measurements below $E_{CM}=1$ MeV, and limited data above 1.2 MeV do not sufficiently constrain the contribution from higher-lying resonances at astrophysical energies. To contribute to the understanding of this process we have measured cross sections and angular distributions for the time-reversed $^7$Li($\gamma$,$\alpha$)$^3$H reaction. The measurement was performed at the HIGS facility at the Triangle Universities Nuclear Laboratory (TUNL) using quasi-monoenergetic ($\sim$3$\%$ resolution) photon energies between 4 and 11 MeV. Tritons and alpha particles were detected in silicon detectors of SIDAR surrounding the $^7$Li target, and the beam intensity was monitored using multiple techniques. Details of the measurement, including the challenges of charged-particle measurements with gamma-ray beams, and preliminary results will be presented.