IEC 61788-17-2021 pdf free download – Superconductivity – Part 17: Electronic characteristic measurements – Local critical current density and its distribution in large-area superconducting films.
This part of lEC 61788 specifies the measurements of the local critical current density (J.) andits distribution in large-area high-temperature superconducting (HTS) films by an inductivemethod using third-harmonicvoltages. The most important consideration for precisemeasurements is to determine J。 at liquid nitrogen temperatures by an electric-field criterionand obtain current-voltage characteristics from its frequency dependence. Although it ispossible to measure J。in applied DC magnetic fields [2o] [21], the scope of this document islimited to the measurement without DC magnetic fields.
This technique intrinsically measures the critical sheet current that is the product of Jc and thefilm thickness d. The range and measurement resolution for J .d of HTS films are as follows.
– Jcd: from 200 A/m to 32 kA/m (based on results，not limitation).
– Measurement resolution: 100 A/m (based on results，not limitation).
Normative 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 latest edition of the referenced document (including anyamendments) applies.
IEC 60050-815,International Electrotechnical Vocabulary – Part 815: Superconductivity(available at <http://www.electropedia.org>)
3Terms and definitions
For the purposes of this document, the terms and definitions given in lEC 60050-815 apply,some of which are repeated here for convenience.
ISo and lEC 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.orglobp3.1
critical currentlc
maximum direct current that can be regarded as flowing without resistance practicallyNote 1 to entry: ‘ is a function of magnetic field strength, temperature and strain.
[SouRCE:IEC 60050-815:2015,815-12-01]
3.2
critical current criterionlcriterion
criterion to determine the critical current，1c, based on the electric field strength，E,or theresistivity , p
Note 1 to entry: E m 10 uV/m or E m 100 uv/m is often used as electric field criterion，and p m 10-14 Q ·m orp = 10-13 o – m is often used as resistivity criterion.
[SoURCE: IEC 60050-815:2015,815-12-02]
3.3
critical current densityJ。
electric current density at the critical current using either the cross-section of the wholeconductor (overall) or of the non-stabilizer part of the conductor if there is a stabilizer
Note 1 to entry: The overall current density is called engineering current density (symbol:J.)-
[SOURCE: IEC 60050-815:2015,815-12-03]
3.4
transport critical current densityJct
critical current density obtained by a resistivity or a voltage measurement
[SOURCE: IEC 60050-815:2015,815-12-04]
3.5
r-value
<superconductor> exponent obtained in a specific range of electric field strength or resistivitywhen the voltagelcurrent U () curve is approximated by the equation U x [”
[SOURCE: IEC 60050-815:2015,815-12-10]
4Requirements
The critical current density J。 is one of the most fundamental parameters that describe thequality of large-area HTs films. In this document,J。 and its distribution are measured non-destructively via an inductive method by detecting third-harmonic voltages ugcos(3ot + 0).A
small coil, which is used both to generate AC magnetic fields and detect third-harmonic voltages,is mounted just above the HTs film and used to scan the measuring area.To measure Jc
precisely with an electric-field criterion,the threshold coil currents l, at which Ug starts toemerge，are measured repeatedly at different frequencies and the E-J characteristics aredetermined from their frequency dependencies.
The target relative combined standard uncertainty in the method used to determine the absolutevalue of J is less than 10 %. However, the target uncertainty is less than 5 % for the purposeof evaluating the homogeneity of J。distribution in large-area superconducting thin films.IEC 61788-17 pdf download.