SIST EN 61788-4:2016

SLOVENSKI STANDARD
SIST EN 61788-4:2016
01-julij-2016
1DGRPHãþD
SIST EN 61788-4:2011
Superprevodnost - 4. del: Meritve razmerja preostale upornosti - Preostala
upornost za superprevodnike iz kompozita Nb-Ti in Nb3Sn (IEC 61788-4:2016)
Superconductivity - Part 4: Residual resistance ratio measurement - Residual resistance
ratio of Nb-Ti and Nb3Sn composite superconductors (IEC 61788-4:2016)
Ta slovenski standard je istoveten z: EN 61788-4:2016
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
SIST EN 61788-4:2016 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61788-4:2016

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SIST EN 61788-4:2016


EUROPEAN STANDARD EN 61788-4

NORME EUROPÉENNE

EUROPÄISCHE NORM
April 2016
ICS 17.200.20; 29.050 Supersedes EN 61788-4:2011
English Version
Superconductivity - Part 4: Residual resistance ratio
measurement - Residual resistance ratio of Nb-Ti and Nb3Sn
composite superconductors
(IEC 61788-4:2016)
Supraconductivité - Partie 4: Mesurage du rapport de Supraleitfähigkeit - Teil 4: Messung des
résistance résiduelle - Rapport de résistance résiduelle des Restwiderstandsverhältnisses - Restwiderstandsverhältnis
composites supraconducteurs de Nb-Ti et de Nb3Sn von Nb-Ti und Nb3Sn Verbundsupraleitern
(IEC 61788-4:2016) (IEC 61788-4:2016)
This European Standard was approved by CENELEC on 2016-02-23. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.



European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 61788-4:2016 E

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SIST EN 61788-4:2016
EN 61788-4:2016
European foreword
The text of document 90/359/FDIS, future edition 4 of IEC 61788-4, prepared by IEC/TC 90
"Superconductivity" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN 61788-4:2016.
The following dates are fixed:
(dop) 2016-11-23
• latest date by which the document has to be implemented at
national level by publication of an identical national
standard or by endorsement
• latest date by which the national standards conflicting with (dow) 2019-02-23
the document have to be withdrawn

This document supersedes EN 61788-4:2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.
Endorsement notice
The text of the International Standard IEC 61788-4:2016 was approved by CENELEC as a European
Standard without any modification.
2

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SIST EN 61788-4:2016
EN 61788-4:2016

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-815 -  International Electrotechnical Vocabulary - -
(IEV) -- Part 815: Superconductivity

3

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SIST EN 61788-4:2016

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SIST EN 61788-4:2016




IEC 61788-4

®


Edition 4.0 2016-01




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Superconductivity –

Part 4: Residual resistance ratio measurement – Residual resistance ratio of

Nb-Ti and Nb Sn composite superconductors

3



Supraconductivité –

Partie 4: Mesurage du rapport de résistance résiduelle – Rapport de résistance


résiduelle des composites supraconducteurs de Nb-Ti et de Nb Sn
3













INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 17.220.20; 29.050 ISBN 978-2-8322-3129-6



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61788-4:2016
– 2 – IEC 61788-4:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
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 . 8
5.3 Cryostat for the resistance (R ) measurement . 9
2
6 Specimen preparation . 9
7 Data acquisition and analysis . 9
7.1 Resistance (R ) at room temperature . 9
1
*
7.2 Resistance (R or R ) just above the superconducting transition . 9
2 2
7.2.1 Correction of strain effect . 9
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
2
strain . 12
7.4 Residual resistance ratio (RRR) . 12
8 Uncertainty and stability of the test method . 12
8.1 Temperature . 12
8.2 Voltage measurement . 12
8.3 Current . 13
8.4 Dimension . 13
9 Test report . 13
9.1 RRR value . 13
9.2 Specimen . 13
9.3 Test conditions . 14
9.3.1 Measurements of R and R . 14
1 2
9.3.2 Measurement of R . 14
1
9.3.3 Measurement of R . 14
2
Annex A (informative) Additional information relating to the measurement of RRR . 15
A.1 Recommendation on specimen mounting orientation . 15
A.2 Alternative methods for increasing temperature of specimen above
superconducting transition temperature . 15
*
A.3 Alternative measurement methods of R or R . 15
2 2
A.4 Bending strain dependency of RRR for Nb-Ti composite superconductor . 18
A.5 Procedure of correction of bending strain effect . 21
Annex B (informative) Uncertainty considerations . 23
B.1 Overview. 23
B.2 Definitions. 23
B.3 Consideration of the uncertainty concept . 23

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SIST EN 61788-4:2016
IEC 61788-4:2016 © IEC 2016 – 3 –
B.4 Uncertainty evaluation example for TC 90 standards . 25
Annex C (informative) Uncertainty evaluation in test method of RRR for Nb-Ti and
Nb Sn composite superconductors . 27
3
C.1 Evaluation of uncertainty . 27
C.2 Summary of round robin test of RRR of a Nb-Ti composite superconductor . 30
C.3 Reason for large COV value in the intercomparison test on Nb Sn composite
3
superconductor . 31
Bibliography . 32

Figure 1 – Relationship between temperature and resistance. 8
Figure 2 – Voltage versus temperature curves and definitions of each voltage . 10
Figure A.1 – Definition of voltages . 17
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) . 19
Figure A.3 – Bending strain dependency of RRR value for round Cu wires . 19
Figure A.4 – Bending strain dependency of normalized RRR value for round Cu wires . 20
Figure A.5 – Bending strain dependency of RRR value for rectangular Cu wires . 20
Figure A.6 – Bending strain dependency of normalized RRR value for rectangular Cu
wires . 21
Figure C.1 – Distribution of observed r of Cu/Nb-Ti composite superconductor . 31
RRR

Table A.1 – Minimum diameter of the measurement mandrel for round wires . 21
Table A.2 – Minimum diameter of the measurement mandrel for rectangular wires. 21
Table B.1 – Output signals from two nominally identical extensometers . 24
Table B.2 – Mean values of two output signals . 24
Table B.3 – Experimental standard deviations of two output signals . 24
Table B.4 – Standard uncertainties of two output signals . 25
Table B.5 – COV values of two output signals . 25
Table C.1 – Uncertainty of each measurement . 30
Table C.2 – Obtained values of R , R and r for three Nb Sn samples . 31
1 2 RRR 3

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SIST EN 61788-4:2016
– 4 – IEC 61788-4:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

SUPERCONDUCTIVITY –

Part 4: Residual resistance ratio measurement –
Residual resistance ratio of Nb-Ti and Nb Sn
3
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 technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61788-4 has been prepared by IEC technical committee 90:
Superconductivity.
This fourth edition cancels and replaces the third edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the unification of similar test methods for residual resistance ratio (RRR) of Nb-Ti and
Nb Sn composite superconductors, the latter of which is described in IEC 61788-11.
3

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SIST EN 61788-4:2016
IEC 61788-4:2016 © IEC 2016 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
90/359/FDIS 90/360/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61788 series, published under the general title Superconductivity,
can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.

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SIST EN 61788-4:2016
– 6 – IEC 61788-4:2016 © IEC 2016
INTRODUCTION
Copper, Cu/Cu-Ni or aluminium is used as matrix material in Nb-Ti and Nb Sn composite
3
superconductors and works as an electrical shunt when the superconductivity is interrupted. It
also contributes to recovery of the superconductivity by conducting heat generated in the
superconductor to the surrounding coolant. The cryogenic-temperature resistivity of copper is
an important quantity, which influences the stability and AC losses of the superconductor. The
residual resistance ratio is defined as a ratio of the resistance of the superconductor at room
temperature to that just above the superconducting transition.
This part of IEC 61788 specifies the test method for residual resistance ratio of Nb-Ti and
Sn composite superconductors. The curve method is employed for the measurement of
Nb
3
the resistance just above the superconducting transition. Other methods are described in A.3.

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SIST EN 61788-4:2016
IEC 61788-4:2016 © IEC 2016 – 7 –
SUPERCONDUCTIVITY –

Part 4: Residual resistance ratio measurement –
Residual resistance ratio of Nb-Ti and Nb Sn
3
composite superconductors



1 Scope
This part of IEC 61788 specifies a test method for the determination of the residual resistance
ratio (RRR) of Nb-Ti and Nb Sn composite superconductors with Cu, Cu-Ni, Cu/Cu-Ni and Al
3
matrix. This method is intended for use with superconductor specimens that have a monolithic
structure with rectangular or round cross-section, RRR value less than 350, and cross-
2
sectional area less than 3 mm . In the case of Nb Sn, the specimens have received a
3
reaction heat-treatment.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050-815, International Electrotechnical Vocabulary – Part 815: Superconductivity
(available at: www.electropedia.org)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-815 and the
following apply.
3.1
residual resistance ratio
RRR
ratio of resistance at room temperature to the resistance just above the superconducting
transition
Note 1 to entry: This note applies to the French language only.
Note 2 to entry: In this part of IEC 61788 for Nb-Ti and Nb Sn composite superconductors, the room temperature
3
is defined as 293 K (20 °C), and the residual resistance ratio is obtained in Formula (1), where the resistance (R )
1
at 293 K is divided by the resistance (R ) just above the superconducting transition.
2
R
1
r = (1)
RRR
R
2
Here r is a value of the residual resistance ratio, R is a value of the resistance measured in a strain-free
RRR 2
condition and zero external magnetic field.
Figure 1 shows schematically a resistance versus temperature curve acquired on a specimen while measuring the
cryogenic resistance.

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SIST EN 61788-4:2016
– 8 – IEC 61788-4:2016 © IEC 2016
(b)
A
R
2
(a)
0
T * T
c

IEC
The cryogenic resistance, R , is determined by the intersection, A, of two straight lines (a) and (b) at
2
*
temperature T .
c
Figure 1 – Relationship between temperature and resistance
4 Principle
The resistance measurement both at room and cryogenic temperatures shall be performed
with the four-terminal technique. All measurements are done without an applied magnetic field.
The target relative combined standard uncertainty of this method is defined as an expanded
uncertainty (k = 2) not to exceed 5 %.
The maximum bending strain induced during mounting and cooling the Nb-Ti specimen shall
not exceed 2 %. The measurement shall be conducted in a strain-free condition or in a
condition with allowable thermal strain for the Nb Sn specimen.
3
5 Apparatus
5.1 Material of measurement mandrel or of measurement base plate
Material of the measurement mandrel for a coiled Nb-Ti specimen or of the measurement
base plate for a straight Nb-Ti or Nb Sn specimen shall be copper, aluminium, silver, or the
3
like whose thermal conductivity is equal to or better than 100 W/(m·K) at liquid helium
temperature (4,2 K). The surface of the material shall be covered with an insulating layer
(tape or a layer made of polyethylene terephthalate, polyester, polytetrafluoroethylene, etc.)
whose thickness is 0,1 mm or less.
5.2 Diameter of the measurement mandrel and length of the measurement base plate
The diameter of the measurement mandrel shall be large enough to keep the bending strain of
the specimen less than or equal to 2 % for the Nb-Ti specimen. The Nb Sn specimen on a
3
base plate shall be measured in a strain-free condition or a condition with allowable thermal
strain.
The measurement base plate shall be at least 30 mm long in one dimension.

Resistance

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SIST EN 61788-4:2016
IEC 61788-4:2016 © IEC 2016 – 9 –
5.3 Cryostat for the resistance (R ) measurement
2
The cryostat shall include a specimen support structure and a liquid helium reservoir for
measurement of the resistance R . The specimen support structure shall allow the specimen,
2
which is mounted on a measurement mandrel or a measurement base plate, to be lowered
into and raised out of a liquid helium bath. In addition, the specimen support structure shall be
made so that a current can flow through the specimen and the resulting voltage generated
along the specimen can be measured.
6 Specimen preparation
The test specimen shall have no joints or splices with a length of 30 mm or longer. The
specimen shall be instrumented with current contacts near each of its ends and a pair of
voltage contacts over its central portion. The distance between two voltage taps (L) shall be
25 mm or longer. A thermometer for measuring cryogenic temperature shall be attached near
the specimen.
Some mechanical method shall be used to hold the specimen against the insulated layer of
the measurement mandrel or base plate. Special care should be taken during instrumentation
and installation of the specimen on the measurement mandrel or base plate so that no
excessive force, which may cause undesired bending strain or tensile strain, would be applied
to the specimen. Ideally, it is intended that the Nb Sn specimen be as straight as possible;
3
however, this is not always the case, thus care should be taken to measure the specimen in
its as received condition.
The specimen shall be mounted on a measurement mandrel or on a measurement base plate
for these measurements. Both resistance measurements, R and R , shall be made on the
1 2
same specimen and the same mounting.
7 Data acquisition and analysis
7.1 Resistance (R ) at room temperature
1
The mounted specimen shall be measured at room temperature (T (K)), where T satisfies

m m
the following condition: 273 K ≤ T ≤ 308 K. A specimen current (I (A)) shall be applied so

m 1
2 2
that the current density is in the range of 0,1 A/mm to 1 A/mm based on the total wire cross-
sectional area, and the resulting voltage (U (V)), I and T shall be recorded. Formula (2)
1 1 m
) at room temperature. The resistance (R )
below shall be used to calculate the resistance (R
m 1
at 293 K (20 °C ) shall be calculated using Formula (3) for a wire with Cu matrix. The value of
R shall be set equal to R without any temperature correction, for wires that do not contain a
1 m,
pure Cu component.
U
1
 (2)
R =
m
I
1
R
m
R = (3)
1
1+×0,00393 T – 293 
( )
m
 
*
7.2 Resistance (R or R ) just above the superconducting transition
2 2
7.2.1 Correction of strain effect
*
Under a strained condition of the Nb-Ti specimen, the measured cryogenic resistance, R , is
2
not a correct value for R . The corresponding correction of the strain effect is described in 7.3.
2

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SIST EN 61788-4:2016
– 10 – IEC 61788-4:2016 © IEC 2016
7.2.2 Data acquisition of cryogenic resistance
The specimen, which is still mounted as it was for the room temperature measurement, shall
be placed in the cryostat for electrical measurement specified in 5.3. Horizontal mounting of
the specimen is recommended in A.1. Alternate cryostats that employ a heating element to
sweep the specimen temperature are described in A.2. The specimen shall be slowly lowered
into the liquid helium bath and cooled to liquid helium temperature over a time period of at
least 5 min.
*
During the acquisition phases of the low-temperature R measurements, a specimen current
2
2 2
(I ) shall be applied so that the current density is in the range 0,1 A/mm to 10 A/mm based
2
on the total wire cross-sectional area, and the resulting voltage (U (V)), I (A), and specimen
2
temperature (T (K)) shall be recorded. In order to keep the ratio of signal to noise high enough,
the measurement shall be carried out under the condition that the absolute value of the
resulting voltage above the superconducting transition exceeds 10 µV. An illustration of the
data to be acquired and its analysis is shown in Figure 2.
U
U *
2+
(b)
A
(a)
U
0+
U
20+
U U
0rev 20–
0
T
U
0–
U *
2–
IEC

NOTE Voltages with subscripts + and – are those obtained in the first and second measurements under positive
and negative currents, respectively, and U and U are those obtained at zero current. For clarity, U
20+ 20– 0rev
measured at zero current is not shown coincident with U . Straight line (a) is drawn
...