Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of Nb superconductors (IEC 61788-23:2018)

This part of IEC 61788 addresses a test method for the determination of the residual resistance
ratio (RRR), rRRR , of cavity-grade niobium. This method is intended for high-purity niobium
grades with 15 < rRRR < 600. The test method should be valid for specimens with rectangular or
round cross-section, cross-sectional area greater than 1 mm2 but less than 20 mm2, and a
length not less than 10 nor more than 25 times the width or diameter.

Supraleitfähigkeit – Teil 23: Messung des Restwiderstandsverhältnisses – Restwiderstandsverhältnis von Nb-Supraleitern

Supraconductivité - Partie 23: Mesurage du rapport de résistance résiduelle - Rapport de résistance résiduelle des supraconducteurs de Nb

IEC 61788-23:2018 spécifie une méthode d'essai pour la détermination du rapport de résistance résiduelle (RRR) du niobium à cavités. Il convient que la méthode d’essai soit valide pour des éprouvettes à sections rectangulaires ou circulaires, de surface de section supérieure à 1 mm2 mais inférieure à 20 mm2, et dont la longueur n’est pas inférieure à 10 fois ni supérieure à 25 fois la largeur ou le diamètre.

Superprevodnost - 23. del: Meritve razmerja preostale upornosti - Razmerje preostale upornosti Nb superprevodnikov (IEC 61788-23:2018)

Ta del standarda IEC 61788 obravnava preskusno metodo za določanje razmerja preostale upornosti (RRR), rRRR, niobija po stopnjah vdolbin. Metoda je predvidena za izjemno čiste vsebnosti niobija z vrednostjo 15 < rRRR < 600. Preskusno metodo je treba uporabljati za vzorce s pravokotnim ali okroglim prečnim prerezom, pri čemer mora biti površina prečnega prereza od 1 mm2 do 20 mm2 in dolžina od 10- do 25-kratna vrednost širine ali premera.

General Information

Status
Published
Public Enquiry End Date
31-Aug-2017
Publication Date
14-Oct-2018
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
10-Oct-2018
Due Date
15-Dec-2018
Completion Date
15-Oct-2018

Relations

Buy Standard

Standard
EN IEC 61788-23:2018 - BARVE
English language
31 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day
Draft
prEN 61788-23:2017
English language
26 pages
sale 10% off
Preview
sale 10% off
Preview
e-Library read for
1 day

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 61788-23:2018
01-december-2018
Superprevodnost - 23. del: Meritve razmerja preostale upornosti - Razmerje
preostale upornosti Nb superprevodnikov (IEC 61788-23:2018)
Superconductivity - Part 23: Residual resistance ratio measurement - Residual
resistance ratio of Nb superconductors (IEC 61788-23:2018)
Ta slovenski standard je istoveten z: EN IEC 61788-23:2018
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
SIST EN IEC 61788-23:2018 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN IEC 61788-23:2018

---------------------- Page: 2 ----------------------

SIST EN IEC 61788-23:2018


EUROPEAN STANDARD EN IEC 61788-23

NORME EUROPÉENNE

EUROPÄISCHE NORM
October 2018
ICS 17.220; 29.050

English Version
Superconductivity - Part 23: Residual resistance ratio
measurement - Residual resistance ratio of Nb superconductors
(IEC 61788-23:2018)
Supraconductivité - Partie 23: Mesurage du rapport de Supraleitfähigkeit - Teil 23: Messung des
résistance résiduelle - Rapport de résistance résiduelle des Restwiderstandsverhältnisses - Restwiderstandsverhältnis
supraconducteurs de Nb von Nb-Supraleitern
(IEC 61788-23:2018) (IEC 61788-23:2018)
This European Standard was approved by CENELEC on 2018-07-10. 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, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 61788-23:2018 E

---------------------- Page: 3 ----------------------

SIST EN IEC 61788-23:2018
EN IEC 61788-23:2018 (E)
European foreword
The text of document 90/400/FDIS, future edition 1 of IEC 61788-23, prepared by IEC/TC 90
"Superconductivity" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN IEC 61788-23:2018.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2019-04-10
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2021-07-10
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 61788-23:2018 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 61788-4:2016 NOTE Harmonized as EN 61788-4:2016 (not modified)
IEC 61788-10:2006 NOTE Harmonized as EN 61788-10:2006 (not modified)

2

---------------------- Page: 4 ----------------------

SIST EN IEC 61788-23:2018
EN IEC 61788-23:2018 (E)
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where 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 - - -
Part 815: Superconductivity




3

---------------------- Page: 5 ----------------------

SIST EN IEC 61788-23:2018

---------------------- Page: 6 ----------------------

SIST EN IEC 61788-23:2018




IEC 61788-23

®


Edition 1.0 2018-06




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Superconductivity –

Part 23: Residual resistance ratio measurement – Residual resistance ratio of Nb

superconductors



Supraconductivité –

Partie 23: Mesurage du rapport de résistance résiduelle – Rapport de résistance


résiduelle des supraconducteurs de Nb













INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 17.220; 29.050 ISBN 978-2-8322-5719-7



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

---------------------- Page: 7 ----------------------

SIST EN IEC 61788-23:2018
– 2 – IEC 61788-23:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Principle . 8
5 Measurement apparatus . 9
5.1 Mandrel or base plate . 9
5.2 Cryostat and support of mandrel or base plate . 9
6 Specimen preparation . 10
7 Data acquisition and analysis . 11
7.1 Data acquisition hardware . 11
7.2 Resistance (R ) at room temperature . 11
1
7.3 Residual resistance (R ) just above the superconducting transition . 11
2
7.4 Validation of the residual resistance measurement . 13
7.5 Residual resistance ratio . 13
8 Uncertainty of the test method . 13
9 Test report . 13
9.1 General . 13
9.2 Test information . 13
9.3 Specimen information . 13
9.4 Test conditions . 14
9.5 RRR value . 14
Annex A (Informative) Additional information relating to the measurement of RRR . 15
A.1 Considerations for specimens and apparatus . 15
A.2 Considerations for specimen mounting orientation . 16
A.3 Alternative methods for increasing temperature of specimen above
superconducting transition temperature . 16
A.3.1 General . 16
A.3.2 Heater method . 16
A.3.3 Controlled methods. 16
A.4 Other test methods . 16
A.4.1 General . 16
A.4.2 Measurement of resistance versus time . 17
A.4.3 Comparison of ice point and room temperature . 17
A.4.4 Extrapolation of the resistance to 4,2 K . 17
A.4.5 Use of magnetic field to suppress superconductivity at 4,2 K . 18
A.4.6 AC techniques . 18
Annex B (informative) Uncertainty considerations . 19
B.1 Overview. 19
B.2 Definitions. 19
B.3 Consideration of the uncertainty concept . 19
B.4 Uncertainty evaluation example for TC 90 standards . 21

---------------------- Page: 8 ----------------------

SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 3 –
Annex C (informative) Uncertainty evaluation for resistance ratio measurement of Nb
superconductors . 23
C.1 Evaluation of uncertainty . 23
C.1.1 Room temperature measurement uncertainty . 23
C.1.2 Cryogenic measurement uncertainty . 24
C.1.3 Estimation of uncertainty for typical experimental conditions . 26
C.2 Round robin test summary . 26
Bibliography . 28

Figure 1 – Relationship between temperature and resistance near the superconducting
transition . 8
Figure A.1 – Determination of the value of R from a resistance versus time plot . 17
2
Figure C.1 – Graphical description of the uncertainty of regression related to the
measurement of R . 25
2


Table B.1 – Output signals from two nominally identical extensometers . 20
Table B.2 – Mean values of two output signals . 20
Table B.3 – Experimental standard deviations of two output signals . 20
Table B.4 – Standard uncertainties of two output signals . 21
Table B.5 – Coefficient of variations of two output signals . 21
Table C.1 – Uncertainty of measured parameters . 26
Table C.2 – RRR values obtained by round robin test . 27

---------------------- Page: 9 ----------------------

SIST EN IEC 61788-23:2018
– 4 – IEC 61788-23:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

SUPERCONDUCTIVITY –

Part 23: Residual resistance ratio measurement –
Residual resistance ratio of Nb 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 61788-23 has been prepared by IEC technical committee 90:
Superconductivity.
The text of this International Standard is based on the following documents:
FDIS Report on voting
90/400/FDIS 90/403/RVD

Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61788 series, published under the general title Superconductivity,
can be found on the IEC website.

---------------------- Page: 10 ----------------------

SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 5 –
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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

---------------------- Page: 11 ----------------------

SIST EN IEC 61788-23:2018
– 6 – IEC 61788-23:2018 © IEC 2018
INTRODUCTION
High-purity niobium is the chief material used to make superconducting radio-frequency cavities.
Similar grades of niobium may be used in the manufacture of superconducting wire.
Procurement of raw materials and quality assurance of delivered products often use the residual
resistance ratio (RRR) to specify or assess the purity of a metal. RRR is defined for
non-superconducting metals as the ratio of electrical resistance measured at room temperature
(293 K) to the resistance measured for the same specimen at low temperature (~4,2 K). The
low-temperature value is often called the residual resistance. Higher purity is associated with
higher values of RRR.
Niobium presents special problems due to its transformation to a superconducting state at ~9 K,
so DC electrical resistance is effectively zero below this temperature. The definition above
would then yield an infinite value for RRR. This document describes a test method to determine
the residual resistance value by using a plot of the resistance to temperature as the test
specimen is gradually warmed through the superconducting transition in the absence of an
applied magnetic field. This results in a determination of the residual resistance at just above
superconducting transition, ~10 K, from which RRR is subsequently determined.
International standards also exist to determine the residual resistance ratio of superconducting
wires. In contrast to superconducting wires, which are usually a composite of a superconducting
material and a non-superconducting material and the RRR value is representative of only the
non-superconducting component, here the entire specimen is composed of superconducting
niobium. Frequently, niobium is procured as a sheet, bar, tube, or rod, and not as a wire. For
such forms, test specimens will likely be a few millimeters in the dimensions transverse to
electric current flow. This difference is significant when making electrical resistance
measurements, since niobium samples will likely be much longer than that for the same
length-to-diameter ratio as a wire, and higher electrical current may be required to produce
sufficient voltage signals. Guidance for sample dimensions and electrical connections is
provided in Annex A. Test apparatus should also take into consideration aspects such as the
orientation of a test specimen relative to the liquid helium surface, accessibility through ports on
common liquid helium dewars, design of current contacts, and minimization of thermal gradients
over long specimen lengths. These aspects distinguish the present document from similar wire
standards.
Other test methods have been used to determine RRR. Some methods use a measurement at a
temperature other than 293 K for the high resistance value. Some methods use extrapolations at
4,2 K in the absence of an applied magnetic field for the low resistance value. Other methods
use an applied magnetic field to suppress superconductivity at 4,2 K. A comparison between this
document and some other test methods is presented in Annex A. It should be noted that
systematic differences of up to 10 % are produced by these other methods, which is larger than
the target uncertainty of this document. Care should therefore be taken to apply this document
or the appropriate corrections listed in Annex A according to the test method used.
Whenever possible, this test method should be transferred to vendors and collaborators who
also perform RRR measurements. To promote consistency, the results of inter-laboratory
comparisons are described in Annex C.

---------------------- Page: 12 ----------------------

SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 7 –
SUPERCONDUCTIVITY –

Part 23: Residual resistance ratio measurement –
Residual resistance ratio of Nb superconductors



1 Scope
This part of IEC 61788 addresses a test method for the determination of the residual resistance
ratio (RRR), r , of cavity-grade niobium. This method is intended for high-purity niobium
RRR
grades with 15 < r < 600. The test method should be valid for specimens with rectangular or
RRR
2 2
round cross-section, cross-sectional area greater than 1 mm but less than 20 mm , and a
length not less than 10 nor more than 25 times the width or diameter.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. 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.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
residual resistance ratio
RRR
ratio of resistance at room temperature to the resistance just above the superconducting
transition
 (1)
r = R / R
RRR 1 2
where is the resistance at 293 K and is the resistance just above the superconducting
R R
1 2
transition, at ~10 K.

---------------------- Page: 13 ----------------------

SIST EN IEC 61788-23:2018
– 8 – IEC 61788-23:2018 © IEC 2018
A
(b)
R
2
(a)
0
T *
Temperature
c

IEC
Figure 1 – Relationship between temperature and resistance near
the superconducting transition
Note 1 to entry: In this document, the room temperature is defined as 20 °C = 293 K, and is obtained as follows:
r
RRR
Figure 1 shows schematically resistance versus temperature data and the graphical procedure used to determine the
value of R . In this figure, the region of maximum slope is extrapolated upward in resistance, as shown by line (a),
2
and the region of minimum slope at temperatures above the transition temperature is extrapolated downward in
temperature, as shown by line (b). The intersection of these extrapolations at point A determines the value of R as
2
*
well as a temperature value T .
c
*
1
Note 2 to entry: The value T is similar to the transition value defined in [1] , and should not be confused with the
c
*
value defined at the midpoint of the transition, called in [2].
T
c
Note 3 to entry: Some standards or documented techniques, e.g. [3][4][5], define with the value of
r R
RRR 1
determined at a temperature other than 293 K, or the value of R determined at a temperature below the
2
superconducting transition. The user of this document should be alert for such differences in definition.
Note 4 to entry: This note applies to the French language only.
4 Principle
The 4-point DC electrical resistance technique shall be performed both at room temperature and
at cryogenic temperature. The test may be done either as a function of temperature or as a
function of time with increasing temperature.
The relative combined standard uncertainty of this method is 3 % with coverage factor 2.
Measurements shall have the following attributes:
a) Measuring current is sufficiently high to provide voltage signals of the order of 1 µV. For
-2
electrical safety, maximum current density should never exceed 1 A mm .
___________
1
Numbers in square brackets refer to the Bibliography.
Resistance

---------------------- Page: 14 ----------------------

SIST EN IEC 61788-23:2018
IEC 61788-23:2018 © IEC 2018 – 9 –
b) Contact resistance for current leads is sufficiently low to avoid excessive heating of the
sample. Typical cryogenic measurement conditions require power dissipation at contacts to
be less than 1 mW.
c) Sample sizes shall be sufficiently large to minimize effects from cutting and handling
2
damage. Typical samples are 1 mm to 3 mm in cross-section dimension and > 5 mm in
cross-sectional area.
d) Sample length shall be at least 10 times and not more than 25 times the width or diameter.
Annex A discusses considerations for sample dimensions and measuring current.
5 Measurement apparatus
5.1 Mandrel or base plate
A straight mandrel or base plate shall be used to support the specimen. Possible materials of
construction include pure copper, pure aluminum, pure silver, electrical grades of Cu-Zr,
Cu-Cr-Zr, Cu-Be, and other copper alloys, electrical grades of Al-Mg, Al-Ag, and other aluminum
alloys, and electrical grades of silver alloys. These provide high thermal conductivity and serve
to remove thermal gradients during measurement. Care should be taken to insulate the
specimen from the mandrel. Possible insulating materials include polyethylene terephthalate,
polyester, and polytetrafluoroethylene, which may be applied as foils, tapes, or coatings.
Glass-fiber reinforced epoxy or other composite materials with good thermal conductivity at
cryogenic temperature may also be used.
The base plate should have a clean and smooth surface finish. There should be no burrs, ridges,
seams, or other asperities that may affect the specimen. High purity niobium specimens are soft
and are susceptible to indentation by surface flaws, and such indentations may alter the sample
and invalidate the resistance measurement.
The mandrel or base plate shall support the entire length and width of the specimen. Mandrel or
base plate geometry should not impose a bending strain of more than 0,2 % on the sample.
A thermometer accurate to 0,1 K is helpful but not required. The mandrel or base plate may
incorporate a mounting for a cryogenic thermometer directly against the body of the mandrel or
base plate and near the center of the test specimen.
Practical base plates are at least 30 mm in length to accommodate assembly of pieces and
handling of samples by human hands. Multiple samples may be mounted against a single base
plate.
5.2 Cryostat and support of mandrel or base plate
The apparatus shall make provisions for mechanical support of the mandrel or base plate. In
addition, such support shall provide electrical leads to carry currents for samples and
thermometers, and measure their voltages. For R and R measurements, the support shall
1 2
permit current to flow through only the sample, so that the entire resulting voltage measured is
only that generated by the sample.
The support structure shall permit measurement of both R and R without dismounting or
1 2
remounting the test specimen. Measurement of R shall require the use of a cryostat, which
2
shall, moreover, integrate with the support.

---------------------- Page: 15 ----------------------

SIST EN IEC 61788-23:2018
– 10 – IEC 61788-23:2018 © IEC 2018
The cryostat shall include a liquid helium reservoir at the bottom of a substantial vertical column.
A support structure shall ac
...

SLOVENSKI STANDARD
oSIST prEN 61788-23:2017
01-september-2017
Superprevodnost - 23. del: Meritve razmerja preostale upornosti - Razmerje
preostale upornosti superprevodnikov iz niobija (Nb)
Superconductivity - Part 23: Residual resistance ratio measurement - Residual
resistance ratio of Nb superconductors
Ta slovenski standard je istoveten z: prEN 61788-23:2017
ICS:
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
oSIST prEN 61788-23:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 61788-23:2017

---------------------- Page: 2 ----------------------
oSIST prEN 61788-23:2017
90/387/CDV

COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61788-23 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2017-05-26 2017-08-18
SUPERSEDES DOCUMENTS:
90/380/CD,90/385/CC

IEC TC 90 : SUPERCONDUCTIVITY
SECRETARIAT: SECRETARY:
Japan Mr Jun Fujikami
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:


Other TC/SCs are requested to indicate their interest, if any, in
this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.

This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

TITLE:
Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of Nb
superconductors


NOTE FROM TC/SC OFFICERS:

Copyright © 2017 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions. You
may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without permission
in writing from IEC.

---------------------- Page: 3 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -2- 90/387/CDV

1 CONTENTS
2
3
4 FOREWORD . 3
5 INTRODUCTION . 5
6 1 Scope . 6
7 2 References . 6
8 3 Terms and definitions . 6
9 4 Principle . 7
10 5 Measurement apparatus . 8
11 5.1 Mandrel or base plate . 8
12 5.2 Cryostat and support of mandrel or base plate . 8
13 6 Specimen preparation . 9
14 7 Data acquisition and analysis . 9
15 7.1 Data acquisition hardware . 9
16 7.2 Resistance ( R ) at room temperature . 10
1
17 7.3 Residual resistance ( R ) just above the superconducting transition . 10
2
18 7.4 Validation of the residual resistance measurement . 11
19 7.5 Residual resistance ratio . 11
20 8 Uncertainty and Stability of the Test Method . 11
21 9 Test Report . 11
22 9.1 Test information . 11
23 9.2 Specimen information . 12
24 9.3 Test conditions . 12
25 9.4 RRR value . 12
26 Annex A (Informative) Additional information relating to the measurement of RRR . 13
27 A.1 Considerations for specimens and apparatus . 13
28 A.2 Considerations for specimen mounting orientation . 13
29 A.3 Alternative methods for increasing temperature of specimen above superconducting
30 transition temperature . 14
31 A.4 Other test methods . 14
32 Annex B (informative) Uncertainty considerations . 17
33 B.1 Overview . 17
34 B.2 Definitions . 17
35 B.3 Consideration of the uncertainty concept . 17
36 B.4 Uncertainty evaluation example for TC 90 standards . 19
37 Annex C (informative) Uncertainty evaluation for resistance ratio measurement of Nb
38 superconductors . 21
39 C.1 Evaluation of uncertainty . 21
40 C.2 Round-robin test summary . 24
41 Bibliography . 26
42

---------------------- Page: 4 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -3- 90/387/CDV

43

44 INTERNATIONAL ELECTROTECHNICAL COMMISSION
45 ____________
46
47 SUPERCONDUCTIVITY –
48
49 Part 23: Residual resistance ratio measurement –
50 Residual resistance ratio of Nb superconductors
51
52 FOREWORD
53 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national
54 electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all
55 questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC
56 publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and
57 Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC
58 National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental
59 and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with
60 the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between
61 the two organizations.
62 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus
63 of opinion on the relevant subjects since each technical committee has representation from all interested IEC National
64 Committees.
65 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in
66 that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC
67 cannot be held responsible for the way in which they are used or for any misinterpretation by any end user.
68 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to
69 the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and
70 the corresponding national or regional publication shall be clearly indicated in the latter.
71 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment
72 services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by
73 independent certification bodies.
74 6) All users should ensure that they have the latest edition of this publication.
75 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its
76 technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature
77 whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of,
78 or reliance upon, this IEC Publication or any other IEC Publications.
79 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable
80 for the correct application of this publication.
81 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC
82 shall not be held responsible for identifying any or all such patent rights.
83 International Standard IEC 61788-23 has been prepared by IEC technical committee 90:
84 Superconductivity.
85 This standard deals with the test method of RRR of high-purity Nb superconductor used to make
86 superconducting radio-frequency cavities, composite superconducting wires, and other components
87 where Nb purity is essential.
88 The text of this standard is based on the following documents:
FDIS Report on voting
90/XX/FDIS 90/XX/RVD
89
90 Full information on the voting for the approval of this standard can be found in the report on voting
91 indicated in the above table.

---------------------- Page: 5 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -4- 90/387/CDV

92
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
93 A list of all parts of the IEC 61788 series, published under the general title Superconductivity, can be
94 found on the IEC website.
95 The committee has decided that the contents of this publication will remain unchanged until the stability
)
1
96 date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific
97 publication. At this date, the publication will be
98 • reconfirmed;
99 • withdrawn;
100 • replaced by a revised edition, or
101 • amended.
102
103

1)
The National Committees are requested to note that for this publication the stability date is 2023

---------------------- Page: 6 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -5- 90/387/CDV

104 INTRODUCTION
105 High-purity niobium is the chief material used to make superconducting radio-frequency cavities.
106 Similar grades of niobium may be used in the manufacture of superconducting wire. Procurement of
107 raw materials and quality assurance of delivered products often use the residual resistance ratio (RRR)
108 to specify or assess the purity of a metal. RRR is defined for non-superconducting metals as the ratio
109 of electrical resistance measured at room temperature (293 K) to the resistance measured for the same
110 specimen at low temperature (~4,2 K). The low-temperature value is often called the residual
111 resistance. Higher purity is associated with higher values of RRR.
112 Niobium presents special problems due to its transformation to a superconducting state at ~9 K, so DC
113 electrical resistance is effectively zero below this temperature. The definition above would then yield an
114 infinite value for RRR. This International Standard describes a test method to determine the residual
115 resistance value by using a plot of the resistance to temperature as the test specimen is gradually
116 warmed through the superconducting transition. This results in a determination of the residual
117 resistance at just above superconducting transition, ~10 K, from which RRR is subsequently determined.
118 International standards also exist to determine the residual resistance ratio of superconducting wires.
119 In contrast to superconducting wires, which are usually a composite of a superconducting material and a
120 non-superconducting material and the RRR value is representative of only the non-superconducting
121 component, here the entire specimen is composed of superconducting niobium. Frequently, niobium is
122 procured as a sheet, bar, tube, or rod, and not as a wire. For such forms, test specimens will likely be
123 a few millimeters in the dimensions transverse to electric current flow. This difference is significant
124 when making electrical resistance measurements, since niobium samples will likely be much longer than
125 that for the same length-to-diameter ratio as a wire, and higher electrical current may be required to
126 produce sufficient voltage signals. Guidance for sample dimensions and electrical connections is
127 provided in Annex A. Test apparatus should also take into consideration aspects such as the
128 orientation of a test specimen relative to the liquid helium surface, accessibility through ports on common
129 liquid helium dewars, design of current contacts, and minimization of thermal gradients over long
130 specimen lengths. These aspects distinguish the present International Standard from the similar wire
131 standards.
132 Other test methods have been used to determine RRR. Some methods use a measurement at a
133 temperature other than 293 K for the high resistance value. Some methods use extrapolations at 4,2 K
134 for the low resistance value. A comparison between the standard and some other test methods is
135 presented in Annex A. It should be noted that systematic differences of up to 10% are produced by
136 these other methods, which is larger than the target uncertainty of this standard. Care should therefore
137 be taken to apply the standard or the appropriate corrections listed in Annex A according to the test
138 method used.
139 Whenever possible, this test method should be transferred to vendors and collaborators who also
140 perform RRR measurements. To promote consistency, the results of inter-laboratory comparisons are
141 also described in Annex C.
142

---------------------- Page: 7 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -6- 90/387/CDV

143
144 SUPERCONDUCTIVITY –
145
146 Part 23: Residual resistance ratio measurement –
147 Residual resistance ratio of Nb superconductors
148
149
150
151 1 Scope
152 The following document addresses a test method for the determination of the residual resistance ratio
153 (RRR), r , of cavity-grade niobium. This method is intended for high-purity niobium grades with
RRR
154 15 < < 600. The test method should be valid for specimens with rectangular or round cross-section,
r
RRR
2 2
155 cross-sectional area greater than 1 mm but less than 20 mm , and a length not less than 10 nor more
156 than 25 times the width or diameter.
157 2 References
158 (1) IEC 60050-815, International Electrotechnical Vocabulary (IEV) – Part 815: Superconductivity
159 (available at: www.electropedia.org)
160 (2) IEC 61788-4 Ed.4 Superconductivity – Part 4: Residual resistance ratio measurement –Residual
161 resistance ratio of Nb-Ti and Nb Sn composite superconductors
3
162 (3) IEC 61788-10 Ed.2 Superconductivity – Part 10: Critical temperature measurement - Critical
163 temperature of composite superconductors by a resistance method
164 (4) ASTM B393-09e1, Standard Specification for Niobium and Niobium Alloy Strip, Sheet, and Plate,
165 ASTM International, West Conshohocken, PA, 2009, www.astm.org
166 (5) GOODRICH L. F, STAUFFER T. C., SPLETT J. D., and VECCHIA D. F., Measuring Residual
167 Resistivity Ratio of High-Purity Nb, NIST publication 31484, also published in Advances in Cryogenic
168 Engineering (Materials) 50A, 41 (2004)
169 (6) SINGER W., ERMAKOV A., and SINGER X., RRR-measurement techniques on high purity niobium
170 Tesla Technology Collaboration report 2010-02 (2010) at
171 http://flash.desy.de/reports_publications/tesla_reports/ttc_reports_2010/.
172 3 Terms and definitions
173 For the purpose of this document, the terms and definitions given in IEC 60050-815 and the following
174 apply:
175 residual resistance ratio
176 RRR
177 the ratio of resistance at room temperature to the resistance just above the superconducting transition.
178 r = R / R (1)
RRR 1 2
179 where R is the resistance at 293 K and R is the resistance just above the superconducting transition,
1 2
180 at ~10 K.
181 Note 1 to entry: In this standard, the room temperature is defined as 20 °C = 293 K, and r is obtained as follows:
RRR
182 Figure 1 shows schematically resistance versus temperature data and the graphical procedure used to determine the value of
183 R . In this figure, the region of maximum slope is extrapolated upward in resistance as shown by line (a), and the region of
2

---------------------- Page: 8 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -7- 90/387/CDV

Temperature


Figure 1 – Relationship between temperature and resistance near the superconducting
transition.
184 minimum slope at temperatures above the transition temperature is extrapolated downward in temperature as shown by line (b).
*
185 The intersection of these extrapolations at point A determines the value of R as well as a temperature value T .
2 c
*
186 Note 2 to entry: The value T is similar to the transition value defined in (2), and should not be confused with the value defined
c
*
187 at the midpoint of the transition, called T in (3).
c
188 Note 3 to entry: Some standards or documented techniques, e.g. (4)(5)(6), define r with the value of R determined at a
RRR 1
189 temperature other than 293 K, or the value of R determined at a temperature below the superconducting transition. The user
2
190 of this International Standard should be alert for such differences in definition.
191 4 Principle
192 The 4-point DC electrical resistance technique shall be performed both at room temperature and at
193 cryogenic temperature. The test may be done either as a function of temperature or as a function of
194 time with increasing temperature.
195 The relative combined standard uncertainty of this method is 3% with coverage factor 2.
196 Measurements shall have the following attributes:
197 a) Measuring current is sufficiently high to provide voltage signals of order 1 µV. For electrical safety,
-2
198 maximum current density should never exceed 1 A mm .
199 b) Contact resistance for current leads is sufficiently low to avoid excessive heating of the sample.
200 Typical cryogenic measurement conditions require power dissipation at contacts to be less than 1
201 mW.
202 c) Sample sizes shall be sufficiently large to minimize effects from cutting and handling damage.
2
203 Typical samples are 1 to 3 mm in cross-section dimension and > 5 mm in cross-sectional area.
204 d) Sample length shall be at least 10 times and not more than 25 times the width or diameter.
205 Annex A discusses considerations for sample dimensions and measuring current.

---------------------- Page: 9 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -8- 90/387/CDV

206 5 Measurement apparatus
207 5.1 Mandrel or base plate
208 A straight mandrel or base plate shall be used to support the specimen. Possible materials of
209 construction include pure copper, pure aluminum, pure silver, electrical grades of Cu-Zr, Cu-Cr-Zr,
210 Cu-Be, and other copper alloys, electrical grades of Al-Mg, Al-Ag, and other aluminum alloys, and
211 electrical grades of silver alloys. These provide high thermal conductivity and serve to remove thermal
212 gradients during measurement. Care should be taken to insulate the specimen from the mandrel.
213 Glass-fiber reinforced epoxy or other composite materials with good thermal conductivity at cryogenic
214 temperature may be used.
215 The base plate should have a clean and smooth surface finish. There should be no burrs, ridges, seams,
216 or other asperities that may affect the specimen. High purity niobium specimens are soft and are
217 susceptible to indentation by surface flaws, and such indentations may alter the sample and invalidate
218 the resistance measurement.
219 If the mandrel or base plate is metal, then the surface of the mandrel or base plate intended to lie against
220 the niobium specimen shall be covered with an electrically insulating material. Possible insulating
221 materials include polyethylene terephthalate, polyester, and polytetrafluoroethylene, which may be
222 applied as foils, tapes, coatings, etc.
223 The mandrel or base plate shall support the entire length and width of the specimen. Mandrel or base
224 plate geometry should not impose a bending strain of more than 0,2% on the sample.
225 A thermometer is helpful but not required. The mandrel or base plate may incorporate a mounting for a
226 cryogenic thermometer directly against the body of the mandrel or base plate and near the center of the
227 test specimen.
228 Practical base plates are at least 30 mm in length to accommodate assembly of pieces and handling of
229 samples by human hands. Multiple samples may be mounted against a single base plate.
230 5.2 Cryostat and support of mandrel or base plate
231 The apparatus shall make provisions for mechanical support of the mandrel or base plate. In addition,
232 such support shall provide electrical leads to carry currents for samples and thermometers, and measure
233 their voltages. For R and R measurements, the support shall permit current to flow through only the
1 2
234 sample, so that the entire resulting voltage measured is only that generated by the sample.
235 The support structure shall permit measurement of both R and R without dismounting or remounting
1 2
236 the test specimen. Measurement of R shall require the use of a cryostat, which shall, moreover,
2
237 integrate with the support.
238 The cryostat shall include a liquid helium reservoir at the bottom of a substantial vertical column. A
239 support structure shall accommodate the raising and lowering of the sample into or out of the helium bath.
240 In addition, anchoring of the sample position, either while immersed in liquid helium or suspended above
241 the surface of the liquid at an arbitrary height, shall be provided. Such suspension permits the
242 equilibration of temperature during measurement and slow increase of temperature with height above
243 the helium bath. Alternately, immersion of the sample into the bath followed by reduction of the bath
244 level via boil-off or pressurized transfer can also be used to vary temperature.
245 A heater may be employed to warm the mandrel or base plate. Care should be taken to distribute the
246 heater along the mandrel and avoid excessive power settings. For instance, a point source of 1 W heat
2
247 input operating at the center of a 1 cm mandrel upon which a 5 cm sample is mounted could produce
-1 -1
248 thermal gradients of 2,5 K along the sample if the thermal conductivity is 100 W m K .
249 Proper cryogenic techniques shall be followed for the construction of the cryostat and apparatus. This
250 includes the use of low thermal conductivity materials to prevent excessive boil-off due to heat
251 conduction from the surrounding laboratory, such as thin-walled stainless steel tubes, composite

---------------------- Page: 10 ----------------------
oSIST prEN 61788-23:2017
IEC CDV 61788-23 © IEC 2017 -9- 90/387/CDV

252 materials, ceramics, and insulation. A can or shield may surround the base plate or mandrel with
253 mounted sample to improve thermal stability. Provisions for pressure relief and vacuum isolation of the
254 liquid helium should be incorporated with the apparatus.
255 6 Specimen preparation
256 High-purity niobium is quite malleable, and even the slightest force can produce deformation of the
257 material. Since dislocations are one source of electron scattering, specimen deformation may
258 inadvertently contribute to the residual resistivity and affect the test result. Therefore, special protocols
259 shall be observed when preparing the specimen. Cutting techniques shall avoid heat and strain to the
260 extent possible. Discharge machining, fluid-jet cutting, or low-speed conventional machining are
261 acceptable and widely-used techniques for applications using high-purity niobium. Specimens cut from
262 larger pieces should be protected and immobilized against a support piece during transport.
263 Operations to de-burr samples should be done with great care to not bend, excessively heat, or
264 otherwise damage the sample. Light sanding with fine paper is one acceptable approach.
265 Specimens should be rectangular or circular bars with uniform cross-section. Long sides of the
266 specimen shall be parallel. Any twisting or curvature shall be avoided to ensure that bending or torsion
267 is not applied to the test specimen during mounting to the mandrel or base plate. Specimens that form
268 an arc or a “U” shape are acceptable provided that the entire curvature can be supported on a plane,
269 without applying torsion to the bent specimen.
270 The specimen shall be clean and have no trace of residues from cutting fluids or any other surface
271 contaminants. Degreasing with solvents, followed by ultrasonic cleaning using a mild water-based
272 detergent, followed by rinsing with distilled or ultra-pure water, then drying in air, is preferred for cleaning
273 residues. Chemical etching to clean the surface has a risk of introducing contaminants, especially
274 hydrogen and oxygen, and should be avoided. Gentle mechanical polishing of the regions where
275 voltage taps and current leads attach is usually sufficient to remove surface oxides. Coating these
276 regions with indium foil or another metal, e.g. by evaporation or sputtering, is an acceptable method to
277 protect polished contacts provided care is taken to avoid coating the entire specimen.
278 The test specimen shall be a single piece and shall not include any joints or splices.
279 A mechanical method shall be used to affix the test specimen to the mandrel or base plate. Special care
280 shall be taken during the installation and instrumentation of the specimen to ensure that there is no
281 excessive force, bending strain, tensile strain, or torsion applied to the specimen.
282 The test specimen shall be instrumented with current contacts near each end of the specimen and a pair
283 of voltage contacts over the central portion between the current contacts (i.e. a 4-point measurement
284 technique). The voltage contacts shall be separated from the current contacts by a distance no smaller
285 than to the largest dimension (width, thickness, or diameter) perpendicular to the specimen length.
286 7 Data acquisition and analysis
287 7.1 Data acquisition hardware
288 Modern power supplies can be computer controlled and come with a variety of features that permit
289 remote control of the current output. Use of such power supplies is not required but could greatly
290 enable automation of the data acquisition. Pulsed modes permit application of current only when
291 voltage signals are being acquired, thereby removing heat generated in the sample during the off cycle.
292 If pulsed current application is used, the pulse duration shall include ample periods for voltage signals to
293 settle and be filtered.
294 Some power supplies incorporate an internal shunt to regulate the output current. If such a power
295 supply is used, the internal shunt shall be calibrated periodically with an external shunt and voltage
296 measure
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.