Using the transient current switch circuit in parallel with the energizing switching contacts for timely control of breaking operation, the increase of contact voltage is suppressed at the last stage of the breaking of electric contacts. Breaking contact voltage Vc and current Ic of electromagnetic relays with Ag contacting electrodes were measured with 12.5-50 V and 0.1-20 A for two hinge springs (Spring constants; 2 N/mm and 0.2 N/mm). The current-decreasing process was clearly measured at the melting voltage Um. After Vc=Um, the breaking time of contact current did not depend on mechanical motion controlled by the two hinge springs and energizing power-supply voltage, but depended on the contact current. The residue of melt electrode was observed optically as a white fusion spot, with radius depending on the energizing current.

Using the transient current switch circuit in parallel with the energizing contacts, the slow decay of the contact current due to thermal fusion of metal was observed just after the contact voltage exceeded the melting contact voltage Um. At that time, the contact voltage was higher than the boiling contact voltage Ub. These results contradict Holm's θ theory. A new melting model of breaking mechanical contact is proposed. The area surrounding a cluster of contacting a-spots melts, the melt metal diffuses, and the contact spot thermally shrinks. Including the metal phase transition from solid to liquid, the increase of contact resistance is introduced to the electric circuit analysis. The numerical analysis agrees qualitatively with measured V-I characteristics.

Anode activity in vacuum arc plays a very important role in both characteristics of vacuum arc and the interruption capacity of vacuum interrupters. In this paper, the transient thermal processes of anode in vacuum arc in a half of arc current cycle with frequency of 50 Hz are simulated by finite element analysis software, ANSYS. Some important phenomena of anode, e.g., the melt and solidification, mass loss due to evaporation, are investigated.

Materials for a new reinforcement method using an internal heating technique have been developed experimentally for fusion splices. The method employs a protective package of a carbon-fiber composite and a hot-melt adhesive in a heat-shrinkable tube. The most appropriate heating current and heating time were determined from a consideration of the decomposition temperature of the adhesive (300) and the complete shrinking temperature (115) and the minimum welding temperature of Nylon 12 (about 180). The protective package can be installed in less than 30 seconds at a power of 10 W. Air bubbles which might cause microbending were completely eliminated by using Nylon 12 as the hot-melt adhesive, irradiated polyethylene as the heat-shrinkable tube and a carbon-fiber-composite electrical heating rod which also acted a tension member. The key for preparing the carbon-fiber composite was to remove its impurities. Under the condition of temperature difference larger than 40 deg. between the shrinking temperature of the heat-shrinkable tube and the melting temperature of the hot-melt adhesive. Nylon 12 and irradiated polyethylene were needed for the complete elimination of residual bubbles. By using Nylon 12 as the hot-melt adhesive, a reliable protective package could be achieved for a fusion spliced optical fiber with a low excess loss of less than 0.06 dB/splice between -60 and +70 and a high tensile strength of 3.9 kg.

Amorphous films of YBCO and BSCCO (2212) sputtered on MgO substrate were crystallized using zonemelt technique. For YBCO films, thin Ag intermediate layer was found to be effective in enhancing crystal growth and preferred orientation. Zone-melted BSCCO films included both (2201) phase and Cu(Sr, Ca)O2 in a form of dendritic crystallites. Tc's obtained for YBCO and BSCCO films were 70 and 75 K, respectively.

Recent progress on photoexcited process applications to fabricating of VLSI and flat panel devices in Japan has been reviewed. The excimer laser melt technique makes it possible to form large-grain poly-Si film on a glass substrate, improving TFT electrical characteristics, and to fill metals into high-aspect-ratio contact holes in VLSI metallization. Scanning of CW laser in poly-Si film led to growth of a single-crystal Si layer on SiO2 to fabricate 3-D (dimensional) devices successfully. Direct writing with pyrolytic reaction was put into practice for interconnection restructuring. In the photochemical process, lower temperature epitaxial growth of Si and dry cleaning of a Si wafer employing Hg lamp irradiation were noted. Directional etching was performed by sidewall film formation, while resolution of better than 0.5 µm was difficult to obtain due to diffraction limit. It was proposed that higher resolution would be obtained by introduction of a nonlinear process which enhanced pattern contrast.