Rf SQUID in the nonhysteretic regime withk2Ql>1
Rf SQUID in the nonhysteretic regime withk2Ql>1
复制标题
Rf SQUID 处于非滞后状态且 k2Ql>1
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
V. V. Kartsovnik
中科院分区：
文献类型：
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作者：
I. M. Dmitrenko;G. Tsoi;V. Shnyrkov;V. V. Kartsovnik
在k2 Ql>1的条件下，对工作频率为30 MHz的rf SQUID在无滞环区（l=2π L0 I 0/π L0 <1）的电流-电压、电流-相位、幅频、相位-频率和信号特性进行了实验测量。其中I 0是弱连接的临界电流，L0是SQUID环电感，k是SQUID环与质量为Q的谐振回路的耦合系数，而λ 0是磁通量量子。数值分析的所有相关参数值接近实验条件下发生的上述特性进行定性比较与理论。与SQUID操作的传统非滞后状态（k2 Ql <1，l<1）的主要区别在于对应于rf幅度和相位的变化的磁通量-电压传递系数ηa和ηθ的强烈增加的可能性。已知η的增加减少了放大器噪声对SQUID能量分辨率的贡献。在4.2K温度下，在信号特性的单值区，实验估计出传递系数的最大值为η=（3±2）× 10 ~（12）V/Wb。结果表明，在k_2Q_1>1的情况下，rf SQUID的分辨率有可能得到显著提高。
Experimental measurements of current-voltage, current-phase, amplitude-frequency, phase-frequency, and signal characteristics of an rf SQUID operating at a frequency of 30 MHz in the nonhysteretic regime (l=2πL0I0/ф0<1) were carried out for the conditionk2Ql>1. HereI0 is the critical current of the weak link,L0 is the SQUID ring inductance,k is the coefficient of coupling of the SQUID ring to a resonant tank circuit of qualityQ, and ф0 is the magnetic flux quantum. A numerical analysis of the above characteristics for all relevant parameter values close to those occurring under experimental conditions was performed for qualitative comparison with theory. The main difference from the traditional nonhysteretic regime of SQUID operation (k2Ql<1,l<1) is the possibility of a strong increase in the magnetic flux-to-voltage transfer coefficients ηa and ηθ corresponding to changes in the rf amplitude and the phase. The increase in η is known to reduce the amplifier noise contribution to the SQUID energy resolution. At a temperature of 4.2 K the maximum value of the transfer coefficient was estimated experimentally as η=(3±2)×1012 V/Wb for the single-valued region of the signal characteristics. The results suggest that considerable improvement of rf SQUID resolution is possible in the regimek2Ql>1.