Uncertainty analysis for ablator areal density measurements using gamma-ray emission of imploded capsules at the OMEGA laser

Summary form only given. We measure the ablator areal density of plastic-shell implosions at the OMEGA laser¹ by comparing the intensity of 4.44-MeV gamma emission from ¹²C nuclei in the ablator to the yield of fusion neutrons, using the Gamma Reaction History instrument². Neutron yield is determined either from the nTOF experiment³ or from the intensity of fusion gammas from D+T reactions. The two methods of determining neutron yield have different sources of uncertainty, associated with absolute signal levels, absolute gamma detector sensitivities, and nTOF calibration (for the former), and the DT branching ratio B and relative gamma detector sensitivities (for the latter). We compare the achievable accuracy of the two methods as applied to recent data from OMEGA, using recent detector calibration data obtained at the Duke HIγS gamma-ray source⁴ and results from on-going efforts to measure B.