Efficiency Of Ultraviolet Radiation Research Articles

Ultraviolet radiation (UV-C): a potential tool for the control of biofouling on marine optical instruments

In an effort to develop a tool for controlling biofouling of marine optical instruments, the efficiency of ultraviolet radiation (UVR – 254 nm) in preventing biofouling was evaluated by conducting in situ experiments at different intensities (14.7, 9.6, 7.3 Wm−2) and exposure times (continuous, on for 30, 15, 5, 1 min h−1) using glass as test coupons. Although there was significant seasonal variation in environmental conditions and phytoplankton composition among each experiment, the amount of biofilm relative to the internal control demonstrated consistent trends. The efficiency of UVR in preventing biofouling increased significantly with increase in intensity and exposure time. UVR was effective even in reducing the population of microfoulers from already developed biofilms. UVR exposure for 30 min h−1 at all intensities as well as for 5 and 15 min h−1 at the highest intensity was found to be most effective. It was observed that UVR dose is not the sole determinant of UVR effectiveness. The reduction in transmission level of the UVR treated coupons was < 5% irrespective of exposure time except for 1 min h−1. These results reveal that UV-C radiation can be used as a potential biofouling control tool for optical instruments.

Evaluation of improved efficiency with a diamond coating for a plasma display panel electrode

Application of diamond to electrode coating of a plasma display panel (PDP) is evaluated, since we expect diamond to emit much secondary electron due to the Auger neutralization induced by Xe ions. In a conventional magnesium oxide-xenon (MgO/Xe) system, the most abundant Xe+ produced in the discharge does not effectively cause the secondary electron emission, because the condition of the Auger neutralization is not satisfied. In order to increase the efficiency of ultraviolet (UV) radiation, being especially important for engineering, we should avoid such inefficiency. Under suitable conditions in diamond/Xe system the Auger neutralization can occur. Further, if the electron affinity χ is negative, i.e., negative electron affinity (NEA), the condition of the Auger neutralization in diamond/Xe system is sufficiently satisfied. First, we calculate the coefficients of the secondary electron emission on diamond of clean surface or of hydrogenated surface where the dangling bonds are terminated, on the basis of the Hagstrum model. If the NEA with the electron affinity χ=−0.5 is realized, the high ion-induced secondary electron coefficients such as γXe=0.25 and γNe=0.32 are obtained. Next, we carry out a one-dimensional fluid simulation of the electric discharge in which the two secondary electron emission coefficients of Ne and Xe obtained theoretically are set. Results are presented with changing the sustaining voltage, the fraction of Xe, and the duration of the zero-voltage phase. For 10%Xe mixture, it is shown that the efficiency of UV radiation in the diamond coating increases two times higher than that in the MgO coating. An unnecessarily spontaneous breakdown during the zero-voltage phase, which is peculiar to high secondary electron emission materials, is observed. A mechanism of the breakdown is discussed and means to suppress it are proposed. Taking the zero-voltage phase short and increasing the fraction of Xe up to 50%, in comparison with MgO, a maximum improvement of 3.5 times in the efficiency of UV radiation can be performed. The high secondary electron emission due to Xe ion brings about a decrease in the sustaining voltage, and the sustaining voltage can be further lowered by shortening the duration of the zero-voltage phase. The operation with an increase of Xe fraction becomes attainable. The feasibility of the high performance operation on the ac type PDP by utilizing the materials including diamond with high secondary electron emission for Xe is quantitatively shown.

プラズマディスプレイパネルの紫外線発光効率の計算機シミュレーションによる研究

プラズマディスプレイパネルの紫外線発光効率の計算機シミュレーションによる研究