DANSK DSF/PREN IEC 61788-22-2 PDF

The IEC61788-22 series defines international standards on superconductor electronic devices. Superconductivity offers various possibilities of realizing sensors and detectors for a variety of measurands. Several types of superconductor sensors and detectors have been developed, using such features as superconducting energy gaps, sharp normal-superconducting transition, nonlinear current-voltage characteristics, superconducting coherent states and quantization of magnetic flux. Superconductors are influenced by interaction with electromagnetic fields, photons, ions, etc. The superconductor sensors and detectors have extremely high performance in resolution, time response and sensitivity, which cannot be realized by any other sensors and detectors. The IEC standard IEC 61788-22-1 lists various types of superconductor sensors and detectors. A key element of some sensors and detectors is Josephson junction. The superconductor material types used for Josephson junctions are divided into two categories: low-Tc superconductor (LTS) and high-Tc superconductor (HTS). This International Standard IEC61788-22-2 defines a measurement method of normal state resistance (Rn) and intrinsic critical current (Ici) of high-Tc Josephson Junctions. HTS Josephson junctions are used for magnetic measurement with Superconductor Quantum Interference Device (SQUID), detection of millimetre to terahertz band radiation and other applications. The measurement method covered in this standard is intended to give an appropriate and agreeable technical base for those engineers working in a field of superconductor technology. Although the mechanism of high-Tc superconductivity is under investigation, the occurrence of the Josephson effect in such weak link structures as bicrystal, step-edge and ramp edge is reliable, and characteristic parameters of conventional low-Tc Josephson junctions are valid also for high-Tc Josephson junctions. The important parameters of high-Tc Josephson junctions for designing superconductor devices are normal state resistance (Rn) and critical current (Ic), which are combined as IcRn product that is obtained experimentally. At this moment, most of high-Tc Josephson junctions exhibit a non-hysteretic characteristic voltage-current (U-I) curve, which is typical for superconductor/normal-conductor/superconductor (SNS) junctions. On U-I curves, two types of distortions are often observed: noise-rounding and self-heating effects. Especially, maximum current values without voltage drop on the U-I curves are often considerably reduced because of the noise-rounding effect, and therefore it is difficult to estimate an intrinsic value. This standard provides a method to obtain intrinsic values by selecting a data set region to eliminate the distortions and by fitting a model function even when two effects are present. The critical current obtained by this standard method is therefore called intrinsic critical current (Ici) without noise-rounding on U-I curves. The Rn is insensitive to the noise rounding and it is possible to avoid the self-heating effect, so that the variable symbol Rn is used. The IciRn product is more essential for designing superconductor devices than the IcRn product. Ici values estimated by this standard for ideal U-I curves without noise are usually higher than experimental Ic values. Practical application of this