IEC 61788-4:2020

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
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: sales@iec.ch.
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
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its
...