超导量子干涉放大器常被用于读出微弱的磁通以及电流信号,可以将微弱信号转化成为大的电压信号.但是对于单个超导量子干涉放大器而言,其输出电压太小不能直接与室温放大器相连,我们考虑将相同参数的超导量子干涉放大器串联到一起,使其输出电压足够大并达到可直接与室温放大器连接的要求.我们已经制备并测试了约瑟夫森结,过阻尼约瑟夫森结,不同输入线圈的单个超导量子干涉放大器以及既有调制线圈又有反馈线圈的串联超导量子干涉放大器,获得了较好的伏安特性曲线,调制曲线以及将调制曲线进行傅里叶变换后的幅频特性曲线.通过分析约瑟夫森结的伏安特性曲线可知我们的制备工艺流程比较稳定.制备与测试超导量子干涉放大器对于以后将其应用于读出微弱信号领域具有重要的意义.
SQUID amplifier is used to read out the weak signal,such as flux and current,Moreover,it can transfer the weak signal to a great voltage.Since the output voltage of single SQUID is too small to connect with the room temperature preamps,we should connect the same SQUIDs and make the output voltage so large that it can be directly connected to the room temperature amplifier.Josephson junction,overdamped Josephson junction,a single SQUID with different modulation coils and series of SQUIDs with modulation coils and feedback coils have been fabricated and tested.We get Ⅰ-Ⅴ characteristics,modulation curves and then achieve the amplitude frequency curve from the FFT of the modulation curve.From theⅠ-Ⅴ characteristics,we can see that the fabrication technology is very stable.The fabrication and the test of SQUID have a great significance for the readout of the weak signal.
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