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IEC 61788-4
Edition 5.0 2020-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Superconductivity –
Part 4: Residual resistance ratio measurement – Residual resistance ratio of
Nb-Ti and Nb Sn composite superconductors
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IEC 61788-4
Edition 5.0 2020-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Superconductivity –
Part 4: Residual resistance ratio measurement – Residual resistance ratio of
Nb-Ti and Nb Sn composite superconductors
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20; 29.050 ISBN 978-2-8322-8033-1
– 2 – IEC 61788-4:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Principle . 8
5 Apparatus . 8
5.1 Material of measurement mandrel or of measurement base plate . 8
5.2 Diameter of the measurement mandrel and length of the measurement base
plate . 9
5.3 Cryostat for the resistance ( ) measurement . 9
R
6 Specimen preparation . 9
7 Data acquisition and analysis . 9
7.1 Resistance ( R ) at room temperature . 9
*
7.2 Resistance ( R or R ) just above the superconducting transition . 10
2 2
7.2.1 Correction of strain effect . 10
7.2.2 Data acquisition of cryogenic resistance . 10
7.2.3 Optional acquisition methods . 12
*
7.3 Correction on measured R of Nb-Ti composite superconductor for bending
strain . 12
7.4 Residual resistance ratio (RRR) . 13
8 Uncertainty and stability of the test method . 13
8.1 Temperature . 13
8.2 Voltage . 13
8.3 Current . 13
8.4 Dimension . 13
9 Test report . 14
9.1 RRR value . 14
9.2 Specimen . 14
9.3 Test conditions . 15
9.3.1 Measurements of R and R . 15
1 2
9.3.2 Measurement of R . 15
9.3.3 Measurement of R . 15
Annex A (informative) Additional information relating to the measurement of RRR . 16
A.1 Recommendation on specimen mounting orientation . 16
A.2 Alternative methods for increasing temperature of specimen above
superconducting transition temperature . 16
*
A.3 Alternative measurement methods of R or R . 16
2 2
A.4 Bending strain dependency of RRR for Nb-Ti composite superconductor . 19
A.5 Procedure of correction of bending strain effect . 22
Annex B (informative) Uncertainty considerations . 24
B.1 Overview. 24
B.2 Definitions. 24
B.3 Consideration of the uncertainty concept . 24
B.4 Uncertainty evaluation example for IEC TC 90 standards . 26
Annex C (informative) Uncertainty evaluation in test method of RRR for Nb-Ti and
Nb Sn composite superconductors . 28
C.1 Evaluation of uncertainty . 28
C.2 Summary of round robin test of RRR of a Nb-Ti composite superconductor . 31
C.3 Reason for large COV value in the intercomparison test on Nb Sn composite
superconductor . 32
Bibliography . 34
Figure 1 – Relationship between temperature and resistance. 8
Figure 2 – Voltage versus temperature curves and definitions of each voltage . 11
Figure A.1 – Definition of voltages . 18
Figure A.2 – Bending strain dependency of RRR value for pure Cu matrix of Nb-Ti
composite superconductors (comparison between measured values and calculated
values) . 20
Figure A.3 – Bending strain dependency of RRR value for round Cu wires . 20
Figure A.4 – Bending strain dependency of normalized RRR value for round Cu wires . 21
Figure A.5 – Bending strain dependency of RRR value for rectangular Cu wires . 21
Figure A.6 – Bending strain dependency of normalized RRR value for rectangular Cu
wires . 22
Figure C.1 – Distribution of observed r of Cu/Nb-Ti composite superconductor . 32
RRR
Table A.1 – Minimum diameter of the measurement mandrel for round wires . 22
Table A.2 – Minimum diameter of the measurement mandrel for rectangular wires. 22
Table B.1 – Output signals from two nominally identical extensometers . 25
Table B.2 – Mean values of two output signals . 25
Table B.3 – Experimental standard deviations of two output signals . 25
Table B.4 – Standard uncertainties of two output signals . 26
Table B.5 – COV values of two output signals . 26
Table C.1 – Uncertainty of each measurement . 31
Table C.2 – Obtained values of R , R and r for three Nb Sn samples .
1 2 RRR 3
Table C.2 – Obtained values of RRR for six Nb Sn specimens . 33
Table C.3 – Average, standard deviation and coefficient of variation for six specimens . 33
– 4 – IEC 61788-4:2020 RLV © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 4: Residual resistance ratio measurement –
Residual resistance ratio of Nb-Ti and Nb Sn
composite superconductors
FOREWORD
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