IEC 61788-7-2020 pdf free download – Superconductivity – Part 7: Electronic characteristic measurements – Surface resistance of high‑temperature superconductors at microwave frequencies.
Thispart of IEC 61788 describes measurement of the surface resistance (Rs) ofsuperconductors at microwave frequencies by the standard two-resonator method.The object
of measurement is the temperature dependence ofRs at the resonant frequency.
The applicable measurement range of Rs for this method is as follows:
-Frequency:
8 GHz< f < 30 GHz
-Measurement resolution:
0.01 m Q at 10 GHz
The Rs data at the measured frequency,and that scaled to 10 GHz, assuming the f2 rule forcomparison, is reported.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.
For undated’ references,the latestedition of the referenced document (including anyamendments) applies.
IEC 60050-815,International Electrotechnical Vocabulary (IEV) – Part 815: Superconductivity
3Terms and definitions
For the purposes of this document, the terms and definitions given in lEC 60050-815 apply.
ISO and IEC maintain terminological databases for use in standardization at the followingaddresses;
-IEC Electropedia: available at http://www.electropedia.orgl
– Iso Online browsing platform: available at http://www.iso.orgl/obp
4Requirements
The Rs of a superconductor film shall be measured by applying a microwave signal to a dielectric
resonator with the superconductor film specimen and then measuring the attenuation of theresonator at each frequency.The frequency shall be swept around the resonant frequency as
the centre，and the attenuation-frequencycharacteristics shall be recorded to obtainthe o-value, which corresponds to the loss.
The target relative combined standard uncertainty of this method is less than 20 % for themeasurement temperature range from 20 K to 80 K.
lt is the responsibility of the user of this document to establish appropriate safety and healthpractices and to determine the applicability of regulatory limitations prior to use.
Hazards exist in this type of measurement. The use of a cryogenic system is essential to cool the superconductors to allow transition into the superconducting state.Direct contact of skinwith cold apparatus components can cause immediate freezing，as can direct contact with aspilled cryogen. The use of an RF generator is also essentialto measure high-frequencyproperties’ of materials. lf its power is too high，direct contact to human bodies can cause animmediate burn.
5 Apparatus
5.1 Measurement system
Figure 1 shows a schematic diagram of the system required for the microwave measurement.
The system consists of a network analyzer system for transmission measurement,ameasurement apparatus,and a thermometer for monitoring the measuring temperature.
An incident power generated from a suitable microwave source such as a synthesized sweeper is applied to the dielectric resonator fixed in the measurement apparatus. The transmissioncharacteristics are shown on the display of the network analyzer. The measurement apparatus is fixed in a temperature-controlled cryocooler.
For the measurement of R s for superconductor films, a vector network analyzer is recommended. A vector network analyzer has better measurement accuracy than a scalar network analyser due to its wide dynamic range. The performance requirements of the vector network analyzer are specified in 7.1.
5.2 Measurement apparatus for R s Figure 2 shows a schematic of a typical measurement apparatus (closed type resonator) for the R s of HTS films deposited on a substrate with a flat surface. The upper HTS film is pressed down by a spring, which is made of phosphor bronze. The plate type spring should be used for the improvement of measurement uncertainty. This type of spring reduces the friction between the spring and the other part of the apparatus, and allows the smooth movement of superconductor films due to the thermal expansion of the dielectric rod. In order to minimize the measurement uncertainty, the sapphire rod and the copper ring shall be arranged coaxially.IEC 61788-7 pdf download.