2004 Volume 45 Issue 4 Pages 1346-1349
In this work, we report a new and simple, but very useful, electron beam (EB) method for preventing the misting of inorganic materials. A law is suggested to predict the time required to achieve clear vision on misted transparent inorganic materials irradiated by an electron beam. Since the time to clear vision before the mist removal treatment (τo) is largely dominated by the thermal conductivity (λ), the time to clear vision (τc) as a function of EB irradiation dose (DEB) can be expressed by the following equation (τc — τ0 = (dτc/dDEB)DEB). Here, an initial rate (dτc/dDEB) of the time to clear vision against EB irradiation doses below 0.2 MGy is defined and evaluated for sapphire lens, silica glass and diamond windows. The initial rate for silica glass (6.5 × 10−5 s/Gy) is 6 ± 0.5 times higher than those of sapphire lens (1.2 × 10−5 s/Gy) and diamond windows (1.0 × 10−5 s/Gy). Charging, dangling bond formation and terminal atom conversion are the main factors in the success of the EB treatment for mist removal. When the contribution of adsorbed atom conversion and charging to the overall rate are 1.0 × 10−5 s/Gy and 0.2 × 10−5 s/Gy respectively, the contribution of dangling bonds should be 5.3 × 10−5 s/Gy.
