1、BRITISH STANDARDBS EN 61788-10:2006Superconductivity Part 10: Critical temperature measurement Critical temperature of composite superconductors by a resistance methodThe European Standard EN 61788-10:2006 has the status of a British StandardICS 29.050g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g5
2、6g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 61788-10:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2006 BSI 20
3、06ISBN 0 580 49625 2National forewordThis British Standard was published by BSI. It is the UK implementation of EN 61788-10:2006. It is identical with IEC 61788-10:2006. It supersedes BS EN 61788-10:2002 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee
4、 L/-/90, Superconductivity.A list of organizations represented on L/-/90 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot co
5、nfer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPISCHE NORM CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de S
6、tassart 35, B - 1050 Brussels 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61788-10:2006 E Part 10: Critical temperature measurement - Critical temperature of composite superconductors by a resistance method (IEC 61788-10:
7、2006) Supraconductivit Partie 10: Mesure de la temprature critique - Temprature critique des composites supraconducteurs par une mthode par rsistance (CEI 61788-10:2006) Supraleitfhigkeit Teil 10: Messung der kritischen Temperatur - Kritische Temperatur von Verbundsupraleitern bestimmt durch ein Wid
8、erstandsmessverfahren (IEC 61788-10:2006) This European Standard was approved by CENELEC on 2006-09-01. 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 alterat
9、ion. Up-to-date lists and bibliographical references concerning 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 tran
10、slation under the responsibility of a CENELEC member into its 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, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Fr
11、ance, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. ICS 29.050 Superconductivity English version EUROPEAN STANDARD NORME EUROPENNE EN
12、61788-10 October 2006 Supersedes EN 61788-10:2002Foreword The text of document 90/191/FDIS, future edition 2 of IEC 61788-10, prepared by IEC TC 90, Superconductivity, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61788-10 on 2006-09-01. This European Standard supe
13、rsedes EN 61788-10:2002. Modifications made in this EN 61788-10:2006 mostly increase covered composite superconductors in this standard, i.e. Cu/Nb3Al and metal-sheathed MgB2composite superconductors and Yttrium- or rare-earth- based coated conductors are added. Furthermore, examples of technical ch
14、ange made are the base plate dimension and definition of the bending strain. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2007-06-01 latest date by which the national stand
15、ards conflicting with the EN have to be withdrawn (dow) 2009-09-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61788-10:2006 was approved by CENELEC as a European Standard without any modification. _ EN 61788-10:2006 2 CONTENTS INTRODUCTION.4 1
16、 Scope 5 2 Normative references .5 3 Terms and definitions .5 4 Determination of critical temperature.5 5 Requirements.6 6 Apparatus 6 7 Measurement procedure .7 8 Tcdetermination.9 9 Accuracy and stability.9 10 Test report .9 Annex A (informative) Additional information relating to measurement of c
17、ritical temperature12 Annex ZA (normative) Normative references to international publications with their corresponding European publications14 Figure 1 Determination of critical temperature (Tc)10 Figure 2 Typical voltage versus temperature curves for first and second runs11 EN 61788-10:2006 3 INTRO
18、DUCTION In addition to critical current and critical field, critical temperature is an important, basic property of materials that exhibit superconductivity. Also, critical temperature is practically important in applications of superconductors, since the higher the critical temperature is, the larg
19、er is temperature margin and the lower the cooling power consumption. Thus, standardization of the measurement method of critical temperature is quite beneficial to conductor users and is urgently required. There are a lot of test methods to measure the critical temperature of superconductors, inclu
20、ding the resistance method, d.c. susceptibility methods using a SQUID magnetometer and VSM (vibrating-sample magnetometer), a.c. susceptibility methods, specific heat methods etc. Test methods, other than the resistance method, may generally be more sensitive and informative compared to the resistan
21、ce method and may be more appropriate for non-homogeneous materials or for thick films, thin films, bulks and powders, for which the resistance method is difficult to apply. In this International Standard, however, the resistance measurement method is employed. This is because the resistance method
22、is simpler and more reliable and can be applied to most of the composite superconductors in industrial use. The outline of this standard was basically prepared by the Japan Fine Ceramics Association, a member institution of VAMAS (Versailles Project on Advanced Materials and Standards), TWA16 (Super
23、conducting materials). The extensive revisions of the outline were primarily made by the New Materials Center supervised by the Japan National Committee and VAMAS. EN 61788-10:2006 4 SUPERCONDUCTIVITY Part 10: Critical temperature measurement Critical temperature of composite superconductors by a re
24、sistance method 1 Scope This part of IEC 61788 specifies a test method for the resistive determination of the critical temperature of composite superconductors for industrial use. The composite superconductors covered in this standard include Cu/Nb-Ti, Cu/Cu-Ni/Nb-Ti and Cu-Ni/Nb-Ti composite superc
25、onductors, Cu/Nb3Sn and Cu/Nb3Al composite super-conductors, and metal-sheathed MgB2composite superconductors, and metal-stabilized Bi-system oxide superconductors and Yttrium- or rare-earth-based coated conductors that have a monolithic structure and a shape of round, flat or square wire containing
26、 mono- or multi-cores of superconductors. 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 amend
27、ments) applies. IEC 60050-815, International Electrotechnical Vocabulary (IEV) Part 815: Superconductivity IEC 61788-4, Superconductivity Part 4: Residual resistance ratio measurement Residual resistance ratio of Nb-Ti composite superconductors 3 Terms and definitions For the purposes of this standa
28、rd, the definitions given in IEC 60050-815 and the following definitionapply. 3.1 critical temperature (of a superconductor) temperature below which a superconductor exhibits superconductivity at zero magnetic field strength and zero electric current 4 Determination of critical temperature In this s
29、tandard, the critical temperature (Tc) is determined as the mid-point of the resistive transition from the normal state to the superconducting state with a minimum of d.c. transport current (specimen current) and at no applied magnetic field strength except for geomagnetic field. EN 61788-10:2006 5
30、Figure 1 shows schematically a curve of resistance versus temperature for a composite superconductor. Draw a tangential line with 100 % height to the part of the curve in the normal state region. The value of the temperature at the intersection of the transition curve and a line with 50 % of the hei
31、ght of the tangential line is Tc. Draw also two lines with heights equalling 10 % and 90 % of the tangential line. The temperatures at the respective intersections with the transition curve, denoted by Tc0,1 and Tc0,9, respectively, are determined as shown in Figure 1. The transition width, Tcis def
32、ined as Tc0,9 Tc0,1. NOTE There are other possible definitions of critical temperature, which are not covered in this standard (see Clause A.1). 5 Requirements The resistance measurement shall be performed with the four-terminal technique. Tcshall be less than 3 % of Tc. In the case that Tcexceeds 3
33、 % of Tc, see Clause A.1. The target precision of this method, the coefficient of variation (COV) in an inter-comparison test, shall be 3 % or less. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and to determine the applicabili
34、ty of regulatory limitations prior to use. Specific precautionary statements are given below. Hazards exist in this type of measurement. Direct contact of skin with cold liquid transfer lines, storage dewars or apparatus components can cause immediate freezing, as can direct contact with a spilled c
35、ryogen. It is imperative that safety precautions for handling cryogenic liquids be observed. 6 Apparatus The apparatus consists of a base plate for specimen mounting, a specimen support structure, a liquid cryogen reservoir, a temperature control/measurement system and a resistance measurement syste
36、m. The specimen shall be mounted on a properly designed base plate. The material used for the base plate shall be a non-ferromagnetic material, for instance copper, aluminum, silver or the like, whose thermal conductivity is equal to or better than 100 W/(mdeg.) at 4,2 K. The surface of the plate sh
37、all be covered with an insulating layer (tape or a layer made of polyester, poly tetra-fluoro-etylene, etc.) whose thickness is 0,1 mm or less. The base plate dimension shall be the sample length plus at least 5 mm long in length and more than twice as wide as the sample width in width. The specimen
38、 mounted on the base plate is inserted with a specimen support structure into a cryostat filled with an appropriate amount of liquid cryogen. The specimen is placed above the level of the liquid cryogen where balancing the cooling of evaporated cryogen gas with the heat coming from outside the cryos
39、tat controls its temperature. Alternative temperature control methods, described in clause A.2, may be employed. EN 61788-10:2006 6 The specimen support structure shall be made so that a current can flow through the specimen and the resulting voltage generated along the specimen can be measured. For
40、 the cooling system mentioned above, the specimen support structure shall allow the specimen to be lowered and raised into and out of the liquid cryogen bath. The cryogen shall be selected from liquid helium, liquid hydrogen, liquid neon and liquid nitrogen. The boiling point of the cryogen selected
41、, however, shall be at least 10 % lower than Tcof the specimen. A thermal anchor to maintain a uniform temperature shall be used in the case of the measurement below 20 K. The cryogen can be used as the thermal anchor. The thermal anchor shall be connected to the base plate with a material with good
42、 thermal conductivity. 7 Measurement procedure 7.1 Mounting of specimen The test specimen shall be a straight length, 10 mm or longer, with a uniform cross section. The distance between two voltage taps shall be 5 mm or longer and shall exceed the longest cross-sectional dimension. Current and volta
43、ge taps should have a low resistance, e.g. by using copper wires and solder contacts in order to avoid noise and voltage fluctuations. The specimen shall be instrumented with current contacts near each end of the specimen and a pair of voltage taps over a central portion of the specimen. The specime
44、n shall be mounted on the base plate for the measurement. Special care shall be taken during instrumentation and installation of the specimen on the base plate to ensure that no excessive force is applied to the specimen, since this may cause undesired bending strain or tensile strain. The applied s
45、train shall be kept within 0,1 %. In some cases, the specimen might be slightly bent or deformed during the reaction heat treatment. Do not straighten the specimen in the case that the resulting strain exceeds 0,1 %. Here, the bending/unbending strain (b) is defined as b = 100 (r /R)( %), where r is
46、 a half of the overall thickness or diameter for the specimen. R is the bending radius on the base plate. At least two calibrated temperature sensors for measuring cryogenic temperature shall be used. One shall be placed near the specimen and the other shall be placed near the base plate. Temperatur
47、e sensors shall be selected from the resistance type: Pt, Pt-Rh, Pt-Co, Rh-Fe, Ge, C, C-glass and metal-oxynitride or the thermo-couple type: Au-Fe/Ni-Cr, Au-Fe/Ag-Au and Au-Fe/Cu. 7.2 Measurement 7.2.1 Voltage versus temperature curves Figure 2 shows schematically two curves of voltage versus tempe
48、rature and the initial voltages U0+and U0 at the starting temperatures for the first (U+-T) and the second (U-T) runs, respectively EN 61788-10:2006 7 7.2.2 First run The specimen shall be slowly lowered into the liquid cryogen bath and cooled to liquid cryogen temperature over a time period of at l
49、east 5 min. A specimen current with a positive polarity shall be applied and the resulting voltage U+(V) between the voltage taps and temperatures T (K) and Tb(K) from the sensors near the specimen and the base plate, respectively, shall be recorded. The specimen current values shall be determined under the condition that the resulting voltage just above the superconducting transition does not exceed 5 mV/m, to avoid an excess joule heat, but exceeds 2 mV/m to obtain enough normal voltage to discriminate the transiti
