Permeability of hollow glass microspheres for inertial confinement fusion targets by dried-gel method

To investigate the deuterium permeation properties of hollow glass microspheres (HGMs) for inertial confinement fusion (ICF) targets, HGMs with different initial glass composition were fabricated by dried gel method under different atmosphere compositions in the furnace, temperatures, and lengths of refining zone. The permeability of HGMs with different wall-thicknesses to deuterium gas under ambient condition was tested. The results show that when the refining temperature is lower than 1400 ℃, the initial glass composition has notable effects on the deuterium-gas permeability of HGMs. However, the volatilization rates of alkali oxides in liquid glass bubbles increase with the temperature and the length of the refining zone, consequently, the permeability coefficients of HGMs made with different initial glass compositions increase and gradually approach to that of silica glass. With the total gas pressure unchanged, increasing the volume ratio of helium gas to argon gas in the furnace can enhance the permeability of HGMs. The permeability coefficient of HGMs to deuterium gas decreases with the increasing of the HGMs wall thickness.