Beta-Layering of Solid Deuterium-Tritium in a Spherical Polycarbonate Shell

In this paper, the authors examine two of the variables that affect the beta-layering process in which nonuniform layers of solid deuterium-tritium (DT) are driven toward uniformity by beta-decay induced sublimation. For these experiments, a 9 mm diameter polycarbonate sphere was partially filled with a 50-50 mix of DT liquid, frozen, and then held at 17 K. The authors measured the equilibration time constant r as functions of solid layer thickness, He exchange gas pressure, and age. Solid layer thicknesses ranged from 200 {mu}m to 650 {mu}, exchange gas pressures from 0 to 600 torr, and age from 0 to 104 days. Results show a significant final solid layer anisotropy with exchange gas pressures above 5 torr, and r values that increased with age by 0.01 min/day for 200 {mu}m-thick layers, and by 0.5 min/day for 650 {mu}m-thick layers. The time constant is shown to be a weak function of exchange gas pressure.