阻尼型高温直流超导量子干涉器磁强计的设计

理论分析了超导环路与一个电阻并联结构的直流超导量子干涉器(dc-SQUID)的特性.给出了这种阻尼型dc-SQUID的电压噪声谱密度、传输函数和磁通噪声谱密度随偏置电流变化的曲线.与无阻尼型高温器件比较，调制参量β大于1的阻尼型高温dc-SQUID磁强计具有高稳定性和易调试等优点.当β大于4时，因传输函数的增大，阻尼型dc-SQUID还能降低它的磁通噪声谱密度从而提高磁强计的检测灵敏度.根据现有高温超导薄膜器件的工艺条件，设计了β等于4的阻尼型高温dc-SQUID磁强计的芯片、其磁通噪声和磁场噪声的理论值 关键词：

DESIGN OF THE HIGH-Tc dc-SQUID MAGNETOMETER WITH A RESISTIVELY SHUNTED INDUCTANCE

The properties of dc-SQUIDs with a resistively shunted inductance(Rdc-SQUID) were theoretically analyzed. The dependencies of S_v,S^1/2_,and dv-/d_a on the bias current i_b for Rdc-SQUID were presented. The advantages of the high-T_c dc-SQUID magnetometer with using Rdc-SQUID have been discussed. A chip of high-T_c dc-SQUID magnetometer with modulation parameter β=4 and damping parameter γ=0.5 was designed under the conditions of the depositing and lithographic technology in laboratory. A gold thin film (≈50nm thickness and 10μm width) was deposited on the superconductive loop as the damping resistance. The theoretical values of S^1/2_Φ and S^1/2_B for the magnetometer are respectively 2.4×10^-6Φ₀/Hz and 200fT/Hz. Comparing the properties between dc-SQUID and Rdc-SQUID,the experimental value S^1/2_B,which is about 400 fT/Hz,for the magnetometer directly coupling with a 8 mm- input coil was estimated.