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

1. 在氧化物超导体中，光照射促进了超导态向正常态的转变。光谱研究表明紫外组分对S-N跃迁更有效。在所测波长范围内，试样的光吸收系数几乎是恒定的，因此认为不涉及热机制。在光照射下，V-I特性测量的电压偏差变得非常大。计算机模拟认为，光照射可引起约0.5 K的温升。然而，在黑暗条件下通过液氮加压实现的单独升温并不会增加电压偏差。这表明电子机制是主要的。电流的增加会引起光照射下电压的增加，但不会改变光脉冲的时间响应。光强的增加引起电压的增加，加速了时间响应。此外，还阐明了光照射电压的增加取决于照射的位置。YBCO薄膜表现出比Bi块体试样更大、更快的响应。对50 μ s宽的光脉冲，获得了10 μ s延迟的响应时间。光照增加的电压不受500高斯以下磁场的影响，除非在黑暗条件下电压相同。而光照射下的电压偏差随磁场的增大而减小。

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.