Fundamental Research on Light Triggered Switching Element of Oxide Superconductor for Power Apparatus

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1. It is confirmed in oxide superconductor that light irradiation promotes the transition form superconducting state to normal state. Spectroscopic study revealed that uv component is more effective for S-N transition. Light absorption coefficient of specimen is almost constant through the examined range of wave length, therefore thermal mechanism is considered not to be involved.2. The deviation of voltage measured in V-I characteristics becomes significantly large under light irradiation. Light irradiation is considered to cause temperature rise of about 0.5 K from computer simulation. However temperature rise alone, which is realized by pressurizing of liquid nitrogen under dark condition, does not increase the deviation of voltage. It suggests that electronic mechanism is dominant.3. The increase in current causes the increase in voltage under light irradiation, but does not change time response for light pulse. The increase in light intensity causes the increase in voltage and hastens time response. Additionally it is clarified that voltage increase by light irradiation depends on the position of irradiation.4. YBCO thin film shows larger and quicker response than Bi bulk specimen. Response time of 10 mus delay was obtained for 50 mus wide light pulse.5. Voltage increase by light irradiation is not affected by magnetic field up to 500 gauss, unless voltage under dark condition is the same. However the deviation of voltage under light irradiation decreases with magnetic field.