oSIST prEN IEC 61788-23:2023
(Main)Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of cavity-grade Nb superconductors
Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of cavity-grade Nb superconductors
Supraleitfähigkeit - Teil 23: Messung des Restwiderstandsverhältnisses - Restwiderstandsverhältnis von hochreinen Nb-Supraleitern für Kavitäten
Supraconductivité - Partie 23: Mesurage du rapport de résistance résiduelle - Rapport de résistance résiduelle des supraconducteurs de Nb à cavités
Superprevodnost - 23. del: Meritve deleža preostale upornosti - Delež preostale upornosti niobijskih superprevodnikov
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN IEC 61788-23:2023
01-september-2023
Superprevodnost - 23. del: Meritve deleža preostale upornosti - Delež preostale
upornosti niobijskih superprevodnikov
Superconductivity - Part 23: Residual resistance ratio measurement - Residual
resistance ratio of cavity-grade Nb superconductors
Supraleitfähigkeit - Teil 23: Messung des Restwiderstandsverhältnisses -
Restwiderstandsverhältnis von hochreinen Nb-Supraleitern für Kavitäten
Supraconductivité - Partie 23: Mesurage du rapport de résistance résiduelle - Rapport de
résistance résiduelle des supraconducteurs de Nb à cavités
Ta slovenski standard je istoveten z: prEN IEC 61788-23:2023
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
oSIST prEN IEC 61788-23:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN IEC 61788-23:2023
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oSIST prEN IEC 61788-23:2023
90/503/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61788-23 ED3
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2023-06-09 2023-09-01
SUPERSEDES DOCUMENTS:
90/499/RR
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.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In So me Countries”
clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for
submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).
TITLE:
Superconductivity - Part 23: Residual resistance ratio measurement - Residual resistance ratio of
cavity-grade Nb superconductors
PROPOSED STABILITY DATE: 2030
NOTE FROM TC/SC OFFICERS:
Copyright © 2023 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.
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1 CONTENTS
2 FOREWORD . 4
3 INTRODUCTION . 6
4 1 Scope . 7
5 2 Normative references . 7
6 3 Terms and definitions . 7
7 4 Principle . 8
8 5 Measurement apparatus . 9
9 5.1 Mandrel or base plate . 9
10 5.2 Cryostat and support of mandrel or base plate . 9
11 6 Specimen preparation . 10
12 7 Data acquisition and analysis . 11
13 7.1 Data acquisition hardware . 11
14 7.2 Resistance (R ) at room temperature . 11
1
15 7.3 Residual resistance (R ) just above the superconducting transition . 11
2
16 7.4 Validation of the residual resistance measurement . 13
17 7.5 Residual resistance ratio . 13
18 8 Uncertainty of the test method . 13
19 9 Test report . 13
20 9.1 General . 13
21 9.2 Test information . 13
22 9.3 Specimen information . 14
23 9.4 Test conditions . 14
24 9.5 RRR value . 14
25 Annex A (informative) Additional information relating to the measurement of RRR . 15
26 A.1 Considerations for specimens and apparatus . 15
27 A.2 Considerations for specimen mounting orientation . 16
28 A.3 Alternative methods for increasing temperature of specimen above
29 superconducting transition temperature . 16
30 A.3.1 General . 16
31 A.3.2 Heater method . 16
32 A.3.3 Controlled methods. 16
33 A.4 Other test methods . 16
34 A.4.1 General . 16
35 A.4.2 Measurement of resistance versus time . 17
36 A.4.3 Comparison of ice point and room temperature . 17
37 A.4.4 Extrapolation of the resistance to 4,2 K . 17
38 A.4.5 Use of magnetic field to suppress superconductivity at 4,2 K . 18
39 A.4.6 AC techniques . 18
40 Annex B (informative) Uncertainty considerations . 19
41 B.1 Overview. 19
42 B.2 Definitions. 19
43 B.3 Consideration of the uncertainty concept . 20
44 B.4 Uncertainty evaluation example for IEC TC 90 standards . 22
45 Annex C (informative) Uncertainty evaluation for resistance ratio measurement of Nb
46 superconductors . 24
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47 C.1 Evaluation of uncertainty . 24
48 C.1.1 Room temperature measurement uncertainty . 24
49 C.1.2 Cryogenic measurement uncertainty . 25
50 C.1.3 Estimation of uncertainty for typical experimental conditions . 27
51 C.2 Inter-laboratory comparison summary . 28
52 Bibliography . 29
53
54 Figure 1 – Relationship between temperature and resistance near the superconducting
55 transition . 8
56 Figure A.1 – Determination of the value of R from a resistance versus time plot . 17
2
57 Figure C.1 – Graphical description of the uncertainty of regression related to the
58 measurement of R . 27
2
59
60 Table B.1 – Output signals from two nominally identical extensometers . 20
61 Table B.2 – Mean values of two output signals . 20
62 Table B.3 – Experimental standard deviations of two output signals . 21
63 Table B.4 – Standard uncertainties of two output signals . 21
64 Table B.5 – Coefficients of variation of two output signals . 21
65 Table C.1 – Uncertainty of measured parameters . 27
66 Table C.2 – RRR values obtained by inter-laboratory comparison using liquid helium . 28
67
68
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69 INTERNATIONAL ELECTROTECHNICAL COMMISSION
70 ____________
71
72 SUPERCONDUCTIVITY –
73
74 Part 23: Residual resistance ratio measurement –
75 Residual resistance ratio of cavity-grade Nb superconductors
76
77 FOREWORD
78 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
79 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
80 co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
81 in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
82 Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
83 preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
84 may participate in this preparatory work. International, governmental and non-governmental organizations liaising
85 with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
86 Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
87 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
88 consensus of opinion on the relevant subjects since each technical committee has representation from all
89 interested IEC National Committees.
90 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
91 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
92 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
93 misinterpretation by any end user.
94 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
95 transparently to the maximum extent possible in their national and regional publications. Any divergence between
96 any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
97 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
98 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
99 services carried out by independent certification bodies.
100 6) All users should ensure that they have the latest edition of this publication.
101 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
102 members of its technical committees and IEC National Committees for any personal injury, property damage or
103 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
104 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
105 Publications.
106 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
107 indispensable for the correct application of this publication.
108 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
109 rights. IEC shall not be held responsible for identifying any or all such patent rights.
110 IEC 61788-23 has been prepared by IEC technical committee 90: Superconductivity. It is an
111 International Standard.
112 This second edition cancels and replaces the first edition published in 2018. This edition
113 constitutes a technical revision.
114 This edition includes the following significant technical changes with respect to the previous
115 edition:
116 a) The scope of this standard was modified to restrict the range of residual resistance ratio to
117 that encountered by providers of material for superconducting radio-frequency cavities.
118 b) The references to technical material were updated and corrected.
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119 The text of this International Standard is based on the following documents:
FDIS Report on voting
90/478/FDIS 90/482/RVD
120
121 Full information on the voting for its approval can be found in the report on voting indicated in
122 the above table.
123 The language used for the development of this International Standard is English.
124 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
125 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
126 at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
127 described in greater detail at www.iec.ch/standardsdev/publications.
128 A list of all parts in the IEC 61788 series, published under the general title Superconductivity,
129 can be found on the IEC website.
130 The committee has decided that the contents of this document will remain unchanged until the
131 stability date indicated on the IEC website under webstore.iec.ch in the data related to the
132 specific document. At this date, the document will be
133 • reconfirmed,
134 • withdrawn,
135 • replaced by a revised edition, or
136 • amended.
137
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.
138
139
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140 INTRODUCTION
141 High-purity niobium is the chief material used to make superconducting radio-frequency cavities.
142 Similar grades of niobium may be used in the manufacture of superconducting wire.
143 Procurement of raw materials and quality assurance of delivered products often use the residual
144 resistance ratio (RRR) to specify or assess the purity of a metal. RRR is defined for non-
145 superconducting metals as the ratio of electrical resistance measured at room temperature
146 (293 K) to the resistance measured for the same specimen at low temperature (~4,2 K). The
147 low-temperature value is often called the residual resistance. Higher purity is associated with
148 higher values of RRR.
149 Niobium presents special problems due to its transformation to a superconducting state at ~9 K,
150 so DC electrical resistance is effectively zero below this temperature. The definition above
151 would then yield an infinite value for RRR. This document describes a test method to determine
152 the residual resistance value by using a plot of the resistance to temperature as the test
153 specimen is gradually warmed through the superconducting transition in the absence of an
154 applied magnetic field. This results in a determination of the residual resistance at just above
155 superconducting transition, ~10 K, from which RRR is subsequently determined.
156 International Standards also exist to determine the RRR of superconducting wires. In contrast
157 to superconducting wires, which are usually a composite of a superconducting material and a
158 non-superconducting material and the RRR value is representative of only the non-
159 superconducting component, here the entire specimen is composed of superconducting niobium.
160 Frequently, niobium is procured as a sheet, bar, tube, or rod, and not as a wire. For such forms,
161 test specimens will likely be a few millimetres in the dimensions transverse to electric current
162 flow. This difference is significant when making electrical resistance measurements, since
163 niobium samples will likely be much longer than that for the same length-to-diameter ratio as a
164 wire, and higher electrical current may be required to produce sufficient voltage signals.
165 Guidance for sample dimensions and electrical connections is provided in Annex A. Test
166 apparatus should also take into consideration aspects such as the orientation of a test specimen
167 relative to the liquid helium surface, accessibility through ports on common liquid helium dewars,
168 design of current contacts, and minimization of thermal gradients over long specimen lengths.
169 These aspects distinguish this document from similar wire standards.
170 Other test methods have been used to determine RRR. Some methods use a measurement at
171 a temperature other than 293 K for the high resistance value. Some methods use extrapolations
172 at 4,2 K in the absence of an applied magnetic field for the low resistance value. Other methods
173 use an applied magnetic field to suppress superconductivity at 4,2 K. A comparison between
174 this document and some other test methods is presented in Annex A. Note that systematic
175 differences of up to 10 % are produced by these other methods, which is larger than the target
176 uncertainty of this document. It is therefore important to apply this document or the appropriate
177 corrections listed in Annex A according to the test method used.
178 Whenever possible, this test method should be transferred to vendors and collaborators who
179 also perform RRR measurements. To promote consistency, the results of inter-laboratory
180 comparisons are described in Clause C.2.
181
182
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183 SUPERCONDUCTIVITY –
184
185 Part 23: Residual resistance ratio measurement –
186 Residual resistance ratio of cavity-grade Nb superconductors
187
188
189
190 1 Scope
191 This part of IEC 61788 addresses a test method for the determination of the residual resistance
192 ratio (RRR), r , of cavity-grade niobium. This method is intended for high-purity niobium
RRR
193 grades with 150 < r < 600. The test method is valid for specimens with rectangular or round
RRR
2 2
194 cross-section, cross-sectional area greater than 1 mm but less than 20 mm , and a length not
195 less than 10 nor more than 25 times the width or diameter.
196 2 Normative references
197 The following documents are referred to in the text in such a way that some or all of their content
198 constitutes requirements of this document. For dated references, only the edition cited applies.
199 For undated references, the latest edition of the referenced document (including any
200 amendments) applies.
201 IEC 60050-815, International Electrotechnical Vocabulary – Part 815: Superconductivity
202 (available at: www.electropedia.org)
203 3 Terms and definitions
204 For the purposes of this document, the terms and definitions given in IEC 60050-815 and the
205 following apply.
206 ISO and IEC maintain terminological databases for use in standardization at the following
207 addresses:
208 • IEC Electropedia: available at http://www.electropedia.org/
209 • ISO Online browsing platform: available at http://www.iso.org/obp
210 3.1
211 residual resistance ratio
212 RRR
213 r
RRR
214 ratio of resistance at room temperature to the resistance just above the superconducting
215 transition
r = R / R
(1)
RRR 1 2
216
217 where
218 R is the resistance at 293 K;
1
219 R is the resistance just above the superconducting transition, at ~10 K.
2
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220
221
222 Figure 1 – Relationship between temperature and resistance near
223 the superconducting transition
224 Note 1 to entry: In this document, the room temperature is defined as 20 °C = 293 K, and is obtained as
r
RRR
225 follows: Figure 1 shows schematically resistance versus temperature data and the graphical procedure used to
226 determine the value of R . In Figure 1, the region of maximum slope is extrapolated upward in resistance, as shown
2
227 by line (a), and the region of minimum slope at temperatures above the transition temperature is extrapolated
228 downward in temperature, as shown by line (b). The intersection of these extrapolations at point A determines the
*
229 value of R as well as a temperature value T .
c
2
*
1
T
230 Note 2 to entry: The value is similar to the transition value defined in [1] , and should not be confused with the
c
*
T
231 value defined at the midpoint of the transition, called in [2].
c
232 Note 3 to entry: Some standards or documented techniques, e.g. [3], [4], [5], [6], define with the value of
r R
RRR 1
233 determined at a temperature other than 293 K, or the value of determined at a temperature below the
R
2
234 superconducting transition. The user of this document should be alert for such differences in definition.
235 4 Principle
236 The 4-point DC electrical resistance technique shall be performed both at room temperature
237 and at cryogenic temperature. The test of resistance shall be done as a function of temperature.
238 Another test method of resistance as a function of time with increasing temperature is described
239 in Annex A.4.2.
240 The relative combined standard uncertainty of this method is 3 % with coverage factor 2.
241 Measurements shall have the following attributes.
242 a) Measuring current is sufficiently high to provide voltage signals of the order of 1 µV. For
−2
243 electrical safety, maximum current density should never exceed 1 A mm .
___________
1
Numbers in square brackets refer to the Bibliography.
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244 b) Contact resistance for current leads is sufficiently low to avoid excessive heating of the
245 sample. Typical cryogenic measurement conditions require power dissipation at contacts to
246 be less than 1 mW.
247 c) Sample sizes are sufficiently large to minimize effects from cutting and handling damage.
2
248 Typical samples are 1 mm to 3 mm in cross-section dimension and > 5 mm in cross-
249 sectional area.
250 d) Sample length is at least 10 times and not more than 25 times the width or diameter.
251 Annex A discusses considerations for sample dimensions and measuring current.
252 5 Measurement apparatus
253 5.1 Mandrel or base plate
254 A straight mandrel or base plate shall be used to support the specimen. Possible materials of
255 construction include pure copper, pure aluminium, pure silver, electrical grades of Cu-Zr,
256 Cu-Cr-Zr, Cu-Be, and other copper alloys, electrical grades of Al-Mg, Al-Ag, and other
257 aluminium alloys, and electrical grades of silver alloys. These provide high thermal conductivity
258 and serve to remove thermal gradients during measurement. The specimen shall be insulated
259 from the mandrel. Possible insulating materials include polyethylene terephthalate, polyester,
260 and polytetrafluoroethylene, which may be applied as foils, tapes, or coatings. Glass-fibre
261 reinforced epoxy or other composite materials with good thermal conductivity at cryogenic
262 temperature may also be used.
263 The base plate should have a clean and smooth surface finish. There should be no burrs, ridges,
264 seams, or other asperities that may affect the specimen. High-purity niobium specimens are
265 soft and are susceptible to indentation by surface flaws, and such indentations may alter the
266 sample and invalidate the resistance measurement.
267 The mandrel or base plate shall support the entire length and width of the specimen. Mandrel
268 or base plate geometry should not impose a bending strain of more than 0,2 % on the sample.
269 A thermometer accurate to 0,1 K is helpful but not required. The mandrel or base plate may
270 incorporate a mounting for a cryogenic thermometer directly against the body of the mandrel or
271 base plate and near the centre of the test specimen.
272 Practical base plates are at least 30 mm in length to accommodate assembly of pieces and
273 handling of samples by human hands. Multiple samples may be mounted against a single base
274 plate.
275 5.2 Cryostat and support of mandrel or base plate
276 The apparatus shall make provisions for mechanical support of the mandrel or base plate. In
277 addition, such support shall provide electrical leads to carry currents for samples and
278 thermometers, and measure their voltages. For R and R measurements, the support shall
1 2
279 permit current to flow through only the sample, so that the entire resulting voltage measured is
280 only that generated by the sample.
281 The support structure shall permit measurement of both R and R without dismounting or
1 2
282 remounting the test specimen. Measurement of R shall require the use of a cryostat, which
2
283 shall, moreover, integrate with the support.
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284 The cryostat shall include a liquid helium reservoir at the bottom of a substantial vertical column.
285 A support structure shall accommodate the raising and lowering of the sample into or out of the
286 helium bath. In addition, anchoring of the sample position, either when immersed in liquid helium
287 or suspended above the surface of the liquid at an arbitrary height, shall be provided. Such
288 suspension permits the equilibration of temperature during measurement and slow increase of
289 temperature with height above the helium bath. Alternatively, immersion of the sample into the
290 bath followed by reduction of the bath level via boil-off or pressurized transfer can also be used
291 to vary temperature.
292 A heater may be employed to warm the mandrel or base plate. The heater should be distributed
293 along the mandrel and excessive power settings should be avoided. For instance, a point source
2
294 of 1 W heat input operating at the centre of a 1 cm mandrel upon which a 5 cm sample is
295 mounted could produce temperature difference of 2,5 K along the sample if the thermal
−1 −1
296 conductivity is 100 W m K .
297 Proper cryogenic techniques shall be followed for the construction of the cryostat and apparatus.
298 This includes the use of low thermal conductivity materials such as thin-walled stainless steel
299 tubes, composite materials, ceramics, and insulation, to prevent excessive boil-off due to heat
300 conducti
...
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