No abstract

X-ray flash radiography is an effective diagnostic in implosive research. While scattering reduces the contrast of radiography, the anti-scattering grids can effectively intercept the scattered radiation and acquire better images. A focused sub-megavolt grid is elaborately manufactured with the combination of lithography, etching, and laser drilling. The consistency of Monte Carlo simulations and radiographic experiments suggests a transmission of about 36% and a 1000 times improvement for the signal to scatter ratio of the grid.

An experimental method is developed for the purpose of simulating plutonium aerosol source terms with conventional metals in laboratory. In this method, metal samples are aerosolized by high explosive detonation in a containment vessel. Aerosols having aerodynamic diameter (AD) less than 10 mm are then collected by a cascade impactor and analyzed by atomic absorption spectroscopy. Two sets of experiments were conducted. In the first set, five candidate metal samples (Ag, W, Sn, Ce, and V) were tested. It is found that the cumulative mass distribution of silver under certain conditions was in good agreement with that of plutonium from the Operation Roller Coaster-Double Track experiment. Thus, silver is chosen as a surrogate to simulate the plutonium aerosol source term. In the second set, silver aerosol source term was studied in detail with different test configurations. The results demonstrate that the peak of the mass-size distribution of silver is in the AD range 1.1-3.3 mm. The amount and fraction of relatively small silver aerosols decrease significantly with time due to coagulation and deposition. Interestingly, the amount of silver in aerosols could be expressed as a quadratic function of the peak detonation pressure.