1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationSuperconductivityPart 11: Residual resistance ratio measurement Residual resistance ratio of Nb3Sn composite superconductorsBS EN 61788-11:2011National forewordThis British Stand
2、ard is the UK implementation of EN 61788-11:2011. It isidentical to IEC 61788-11:2011. It supersedes BS EN 61788-11:2003 which iswithdrawn.The UK participation in its preparation was entrusted to Technical CommitteeL/-/90, Super Conductivity.A list of organizations represented on this committee can
3、be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2011ISBN 978 0 580 70239 6ICS 17.220.20; 29.050Compliance with a British Standard cannot confer immunity fromlegal obl
4、igations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 30 September 2011.Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 61788-11:2011EUROPEAN STANDARD EN 61788-11 NORME EUROPENNE EUROPISCHE NORM August 20
5、11 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Management Centre: Avenue Marnix 17, B - 1000 Brussels 2011 CENELEC - All rights of exploitation in any form and by any means reserved w
6、orldwide for CENELEC members. Ref. No. EN 61788-11:2011 E ICS 17.220; 29.050 Supersedes EN 61788-11:2003English version Superconductivity - Part 11: Residual resistance ratio measurement - Residual resistance ratio of Nb3Sn composite superconductors (IEC 61788-11:2011) Supraconductivit - Partie 11:
7、Mesure du rapport de rsistance rsiduelle - Rapport de rsistance rsiduelle des supraconducteurs composites de Nb3Sn (CEI 61788-11:2011) Supraleitfhigkeit - Teil 11: Messung des Restwiderstandsverhltnisses - Restwiderstandsverhltnis von Nb3Sn-Verbundsupraleitern (IEC 61788-11:2011) This European Stand
8、ard was approved by CENELEC on 2011-08-15. 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 concerni
9、ng such national standards may be obtained on application to the Central Secretariat 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
10、 own language and notified to the Central Secretariat 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, France, Germany, Greece, Hungary, Iceland, I
11、reland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 61788-11:2011EN 61788-11:2011 - 2 - Foreword The text of document 90/268/FDIS, future edition 2 of IEC 61788-11, prepa
12、red by IEC TC 90, Superconductivity was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 61788-11:2011. The following dates are fixed: latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement
13、(dop) 2012-05-15 latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2014-08-15 This document supersedes EN 61788-11:2003. The main revisions are the addition of two new annexes “Uncertainty considerations“ (Annex B) and “Uncertainty evaluation in tes
14、t method of RRR for Nb3Sn“ (Annex C). 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
15、 Standard IEC 61788-11:2011 was approved by CENELEC as a European Standard without any modification. BS EN 61788-11:2011- 3 - EN 61788-11:2011 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are
16、 indispensable for the application 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 When an international publication has been modified by common modifications, indic
17、ated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 60050-815 - International Electrotechnical Vocabulary (IEV) - Part 815: Superconductivity - - BS EN 61788-11:2011 2 61788-11 IEC:2011 CONTENTS INTRODUCTION . 5 1 Scope . 6 2 Normative references . 6 3 Terms and definiti
18、ons . 6 4 Requirements . 7 5 Apparatus . 7 5.1 Material of measuring base plate . 7 5.2 Length of the measuring base plate . 7 5.3 Cryostat for the resistance, R2, measurement . 7 6 Specimen preparation. 8 7 Data acquisition and analysis 8 7.1 Resistance (R1) at room temperature 8 7.2 Resistance (R2
19、) just above the superconducting transition 8 7.3 Residual resistance ratio (RRR) 10 8 Uncertainty and stability of the test method 11 8.1 Temperature 11 8.2 Voltage measurement 11 8.3 Current 11 8.4 Dimension . 11 9 Test report 11 9.1 RRR value . 11 9.2 Specimen 11 9.3 Test conditions 12 Annex A (i
20、nformative) Additional information relating to the measurement of RRR . 13 Annex B (informative) Uncertainty considerations 15 Annex C (informative) Uncertainty evaluation in test method of RRR for Nb3Sn . 19 Figure 1 Relationship between temperature and resistance . 7 Figure 2 Voltage (U) versus te
21、mperature (T) curves and definitions of each voltage . 9 Table B.1 Output signals from two nominally identical extensometers 16 Table B.2 Mean values of two output signals . 16 Table B.3 Experimental standard deviations of two output signals 16 Table B.4 Standard uncertainties of two output signals
22、17 Table B.5 Coefficient of variations of two output signals. 17 Table C.1 Uncertainty of each measurement 20 Table C.2 Obtained values of R1, R2and RRR for three Nb3Sn samples 21 BS EN 61788-11:201161788-11 IEC:2011 5 INTRODUCTION Copper or aluminium is used as stabilizer material in multifilamenta
23、ry Nb3Sn superconductors and works as an electrical shunt when the superconductivity is interrupted. It also contributes to recovery of the superconductivity by conducting the heat generated in the superconductor to the surrounding coolant. The resistivity of copper used in the composite superconduc
24、tor in the cryogenic temperature region is an important quantity which influences the stability 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. In this Internatio
25、nal Standard, the test method for the residual resistance ratio of Nb3Sn composite superconductors is described. The curve method is employed for the measurement of the resistance just above the superconducting transition. Other methods are described in Clause A.3. BS EN 61788-11:2011 6 61788-11 IEC
26、:2011 SUPERCONDUCTIVITY Part 11: Residual resistance ratio measurement Residual resistance ratio of Nb3Sn composite superconductors 1 Scope This part of IEC 61788 covers a test method for the determination of the residual resistance ratio (RRR) of Nb3Sn composite superconductors. This method is inte
27、nded for use with superconductor specimens that have a monolithic structure with rectangular or round cross-section, RRR less than 350 and cross-sectional area less than 3 mm2, and have received a reaction heat-treatment. Ideally, it is intended that the specimens be as straight as possible; however
28、, this is not always the case, thus care must be taken to measure the specimen in its as received condition. All measurements are done without an applied magnetic field. The method described in the body of this standard is the “reference” method and optional acquisition methods are outlined in Claus
29、e A.3. 2 Normative references The following referenced documents are indispensable for the application 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, Inte
30、rnational Electrotechnical Vocabulary Part 815: Superconductivity 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 the ratio of resistance at room temperature to the resistance just
31、above the superconducting transition NOTE In this standard for Nb3Sn composite superconductors, the room temperature is defined as 293K (20C), and the residual resistance ratio is obtained in Equation (1) below, where the resistance (R1) at 293K is divided by the resistance (R2) just above the super
32、conducting transition. 21RRRRR = (1) Figure 1 shows schematically a resistance versus temperature curve acquired on a specimen while measuring cryogenic resistance. Draw a line in Figure 1 where the resistance sharply increases (a), and draw also a line in Figure 1 where the resistance increases gra
33、dually (b) with temperature. The value of resistance at the intersection of these two lines at T=Tc*, A, is defined as resistance (R2) just above the superconducting transition. BS EN 61788-11:201161788-11 IEC:2011 7 R2A Temperature (b) (a) Resistance0 Tc* IEC 1603/11 Temperature Tc* is that at the
34、intersection point. Figure 1 Relationship between temperature and resistance 4 Requirements The resistance measurement both at room and cryogenic temperatures shall be performed with the four-terminal technique. The target relative combined standard uncertainty of this method is defined as an expand
35、ed uncertainty (k = 2) not to exceed 10% based on the coefficient of variation (COV) of 5% in the intercomparison test (see Clause C.2). 5 Apparatus 5.1 Material of measuring base plate Material of the measuring base plate shall be copper, aluminum, silver or the like whose thermal conductivity is e
36、qual to or better than 100W/(mK) 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 0,1mm or less. 5.2 Length of the measuring ba
37、se plate The measuring base plate shall be at least 30mm long in one dimension. 5.3 Cryostat for the resistance, R2, measurement The cryostat shall include a specimen support structure and a liquid helium reservoir for the resistance, R2, measurement. The specimen support structure shall allow the s
38、pecimen, which is mounted on a measurement base plate, to be lowered and raised into and out of a liquid helium bath. In addition, the specimen support structure shall be made so that a current BS EN 61788-11:2011 8 61788-11 IEC:2011 can flow through the specimen and the resulting voltage generated
39、along the specimen can be measured. 6 Specimen preparation The test specimen shall have no joints or splices, and shall be 30mm or longer. The distance between two voltage taps (L) shall be 25mm or longer. A thermometer for measuring cryogenic temperature shall be attached near the specimen. Some me
40、chanical method shall be used to hold the specimen against the insulated layer of the measurement base plate. Special care shall be taken during instrumentation and installation of the specimen on the measurement base plate so that no excessive force, which may cause undesired bending strain or tens
41、ile strain, shall be applied to the specimen. The specimen shall be instrumented with current contacts near each end of the specimen and a pair of voltage contacts over a central portion of the specimen. The specimen shall be mounted on a measurement base plate for these measurements. Both resistanc
42、e measure-ments, R1and R2, shall be made on the same specimen and the same mounting. 7 Data acquisition and analysis 7.1 Resistance (R1) at room temperature The mounted specimen shall be measured at room temperature (Tm (K), where Tmsatisfies the following condition 273 Tm 308. A specimen current (I
43、1(A) shall be applied so that the current density is in the range of 0,1A/mm2to 1A/mm2based on the total wire cross-sectional area, and the resulting voltage (U1(V), I1and Tmshall be recorded. Equation(2) below shall be used to calculate the resistance (Rm) at room temperature. The resistance (R1) a
44、t 293 K shall be calculated using equation (3) for a wire with Cu stabilizer. The value of R1shall be set equal to Rm, without any temperature correction, for wires that do not contain a pure Cu component. 11mIUR = (2) )( 2930,003931mm1+=TRR (3) 7.2 Resistance (R2) just above the superconducting tra
45、nsition 7.2.1 The specimen, which is still mounted as it was for the room temperature measurement, shall be placed in the cryostat for electrical measurement specified under 5.3. Alternate cryostats that employ a heating element to sweep the specimen temperature are described in Clause A.2. 7.2.2 Th
46、e specimen shall be slowly lowered into the liquid helium bath and cooled to liquid helium temperature over a time period of at least 5min. 7.2.3 During the acquisition phases of the low-temperature R2measurements, a specimen current (I2) shall be applied so that the current density is in the range
47、of 0,1A/mm2to 10 A/mm2based on the total wire cross-sectional area and the resulting voltage (U(V), I2(A), and specimen 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 BS EN 61788-11:20
48、1161788-11 IEC:2011 9 absolute value of resulting voltage above the superconducting transition exceeds 10 V. An illustration of the data to be acquired and its analysis is shown in Figure 2. U U*2+U*2U0+U0revU0U20+U20(b) (a) A 0 T IEC 1604/11 Voltages with subscripts + and are those obtained in the
49、first and second measurements under positive and negative currents, respectively, and U20+and U20are those obtained at zero current. For clarity, U0revis not shown coincident with U0. Voltages U2+* and U2-* with asterisk are those at the intersection points. Figure 2 Voltage (U) versus temperature (T) curves and definitions of each voltage 7.2.4 When the specimen is in superconducting state and test current (I2) is applied, two voltages shall be mea
