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1、BRITISH STANDARD BS EN 61788-3:2001 Superconductivity Part 3: Critical current measurement DC critical current of Ag-sheathed Bi-2212 and Bi-2223 oxide superconductors The European Standard EN 61788-3:2001 has the status of a British Standard ICS 17.220; 29.050 ? Licensed Copy: sheffieldun sheffield
2、un, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 61788-3:2001 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 12 March 2003 BSI 12 March 2003 ISBN 0 580 41379 9 National foreword This British Standard is the offici
3、al English language version of EN 61788-3:2001. It is identical with IEC 61788-3:2000. There has been no UK participation in the preparation of this document. This standard is published as part of the UKs obligation to give the status of a national standard to all standards prepared by CENELEC. Any
4、enquiries on the text should be sent to the Head of Standards International content. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering syst
5、em to the other, publications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Ind
6、ex”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. 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 does not of itself con
7、fer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 22, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issue
8、d since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARDEN 61788-3 NORME EUROPENNE EUROPISCHE NORMMarch 2001 CENELEC European Committee for Electrotechnical Standardization Comit Europen de
9、Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2001 CENELEC -All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61788-3:2001 E ICS 17.220;29.050 Englis
10、h version Superconductivity Part 3: Critical current measurement - DC critical current of Ag-sheathed Bi-2212 and Bi-2223 oxide superconductors (IEC 61788-3:2000) Supraconductivit Partie 3: Mesure du courant critique - Courant critique continu des oxydes supraconducteurs Bi-2212 et Bi-2223 avec gain
11、e en argent (CEI 61788-3:2000) Supraleitfhigkeit Teil 3: Messen des kritischen Stromes - Kritischer Strom (Gleichstrom) von Ag-ummantelten oxidischen Bi-2212 und Bi-2223-Supraleitern (IEC 61788-3:2000) This European Standard was approved by CENELEC on 2000-12-01. CENELEC members are bound to comply
12、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 Central Secret
13、ariat 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 Central Secretariat has the same status as th
14、e official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffiel
15、dun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Foreword The text of document 90/80/FDIS, future edition 1 of IEC 61788-3, prepared by IEC TC 90, Superconductivity, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61788-3 on 2000-12
16、-01. 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)2001-10-01 latest date by which the national standards conflicting with the EN have to be withdrawn(dow)2003-12-01 Annexes d
17、esignated “normative“ are part of the body of the standard. Annexes designated “informative“ are given for information only. In this standard, annex ZA is normative and annexes A and B are informative. Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IE
18、C 61788-3:2000 was approved by CENELEC as a European Standard without any modification. _ Page 2 EN 617883:2001 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 68718-CEI 3:0200(E) 3 CONTENTS Page INTRODUCTION.4 Clause 1Scope .5 2Normative re
19、ferences5 3Terminology6 4Requirements6 5Apparatus .7 6Specimen preparation .7 7Measurement procedure .8 8Precision and accuracy of the test method 9 9Calculation of results 10 10 Test report 11 Annex A (informative) Additional information relating to clauses 1 to 9.13 Annex B (informative) Magnetic
20、hysteresis of the critical current of high-temperature oxide superconductors19 Annex ZA (normative) Normative references to international publications with their corresponding European publications .21 Bibliography22 Figure 1 Intrinsic U-I characteristic.12 Figure 2 U-I characteristic with a current
21、 transfer component.12 Figure A.1 Illustration of a measurement configuration for a short specimen of a few hundred A class conductors 18 Figure A.2 Illustration of superconductor simulator circuit 18 Table A.1 Thermal expansion data of Bi-oxide superconductor and selected materials 17 Page 3 EN 617
22、883:2001 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 68718-3 CEI:0200(E) INTRODUCTION In 1986 J.G. Bednorz and K.A. Mueller discovered that some Perovskite type Cu-containing oxides show superconductivity at temperatures far above thos
23、e which metallic superconductors have shown. Since then, extensive R Bi2Sr2CaCu2Ox ( x = 8), Bi-2223; (Bi,Pb)2Sr2Ca2Cu3Ox ( x = 10). 4 Requirements The critical current of a superconductor shall be measured by applying a direct current (I) to the superconductor specimen and then measuring the voltag
24、e (U) generated along a section of the specimen. The current shall be increased from zero and the voltage-current (U-I) characteristic generated and recorded. The target precision of this method is a coefficient of variation (standard deviation divided by the average of the critical current determin
25、ations) that is less than 5 % for the measurement at 0 T and near 4,2 K or 77 K. The use of a common current transfer correction is excluded from this test method. Furthermore, if a current transfer signature is pronounced in the measurement, then the measurement shall be considered invalid. It is t
26、he responsibility of the user of this standard to consult and establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given below. Hazards exist in this type of measurement. Very large direct c
27、urrents with very low voltages do not necessarily provide a direct personal hazard, but accidental shorting of the current leads with another conductor, such as tools or transfer lines, can release significant amounts of energy and cause arcs or burns. It is imperative to isolate and protect current
28、 leads from shorting. Also the energy stored in the superconducting magnets commonly used for the background magnetic field can cause similar large current and/or voltage pulses or deposit a large amount of thermal energy in the cryogenic systems causing rapid boil-off or even explosive conditions.
29、The use of cryogenic liquids is essential to cool the superconductors, which allows the transition into the superconducting state. 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 cryogen
30、. It is imperative that safety precautions for handling cryogenic liquids be observed. Page 6 EN 617883:2001 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 68718-CEI 3:0200(E) 7 5 Apparatus 5.1 Measurement holder material The measurement ho
31、lder shall be made from an insulating material or from a conductive non- ferromagnetic material that is either covered or not covered with an insulating layer. The critical current may inevitably depend on the measurement holder material due to the strain induced by the differential thermal contract
32、ion between the specimen and the measurement holder. The total strain induced in the specimen at the measuring temperature shall be minimized to be within 0,1 %. If there is an excess strain due to the differential thermal contraction of the specimen and the holder, the critical current shall be not
33、ed to be determined under an excess strain state by identification of the holder material. Suitable measurement holder materials are recommended in A.4.1. Any one of these may be used. When a conductive material is used without an insulating layer, the leakage current through the holder shall be les
34、s than 1 % of the total current when the specimen current is at Ic (see 8.5). 5.2 Measurement holder construction The holder shall have a flat surface on which a straight specimen can be placed. The current contact shall be rigidly fastened to the measurement holder to avoid stress concentration in
35、the region of transition between the holder and the current contact. It is important to have no difference in level between the mounting surfaces of the current contacts and the mounting specimen holder. 6 Specimen preparation 6.1 Reaction heat treatment Reaction heat treatment shall be carried out
36、according to the manufacturers specification which includes reaction temperature, period and atmosphere, oxygen partial pressure, specimen cooling and warming rates, specimen protection method against mechanical strain, examination of deformation and surface condition of specimen and error limits wh
37、ich must not be exceeded. Temperature variations within the furnace shall be controlled such as not to exceed those limits. Reaction heat treatment can be skipped when it has already been carried out by the manufacturer. 6.2 Specimen mounting for measurement After the reaction heat treatment, the en
38、ds of the specimen shall be trimmed to suit the measurement holder. The specimen shall be mounted to the flat surface of the holder and both ends shall be soldered to the current contact blocks (see A.6 for solder material). Page 7 EN 617883:2001 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 0
39、9 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 8 68718-3 CEI:0200(E) For the test in magnetic fields, a low-temperature adhesive (such as epoxy) shall be used to bond the specimen to the measurement holder to reduce specimen motion against the Lorentz force. The bond shall be strong enough to
40、 keep the specimen in place against the Lorentz force, in the case where the applied magnetic field is perpendicular to the specimen surface. The length of a specimen to be measured shall be defined as follows: L1 = 2 ? L2 + L + 2 ? L3 ? 5 ? W(1) L2, L, L3 ? W(2) where L is the distance between the
41、voltage taps; L1 is the length of a specimen to be measured; L2 is the length of the soldered part of the current contact; L3 is the distance from a current contact to a voltage tap; W is the width or diameter of a specimen to be measured. For a specimen with a large current-carrying capacity, L2 sh
42、all be larger. L shall be larger for a measurement that needs high sensitivity and L3 shall be larger when current transfer voltage cannot be neglected. In the case of the wire specimen the angle between the specimen axis and the magnetic field shall be (90 9). This angle shall be determined with an
43、 accuracy of 2. In the case of tape specimens, there are two options in addition to the requirement that the angle between the longitudinal specimen axis and the magnetic field shall be (90 9). In one option, the magnetic field shall be perpendicular to the specimen surface, the angle deviation bein
44、g within 7. In the second option, the magnetic field shall be parallel to the specimen surface, the angle deviation being within 3. The voltage taps shall be placed in the central part along both the specimen length and the specimen width. All soldering shall be conducted as quickly as possible so a
45、s not to cause thermal damage to the specimen. Soft voltage leads shall be used and twisted before soldering. The distance between the voltage taps, L, shall be measured to an accuracy of 5 %. This voltage tap separation shall be greater than the specimen width. 7 Measurement procedure For testing,
46、the specimen and the holder shall be mounted in a test cryostat consisting of a liquid helium or nitrogen dewar, a magnet (when necessary) and a support structure. The specimen shall be immersed in cryogen for the data acquisition phase. The specimen may be cooled slowly in cryogen vapour, or insert
47、ed slowly into the cryogen bath, or, in the case of cooling to the 4,2 K range, first slowly immersed in liquid nitrogen and then liquid helium. The specimen shall be cooled from room temperature to liquid helium (or liquid nitrogen) temperature over a time period of at least 5 min. Page 8 EN 617883
48、:2001 Licensed Copy: sheffieldun sheffieldun, na, Thu Nov 09 04:34:45 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 68718-CEI 3:0200(E) 9 Between each measuring temperature and each magnetic-field angle, the specimen shall be cooled in zero field, from a temperature above the critical temperature down
49、to the measuring temperature, and then the field angle with respect to the conductor cross-section shall be fixed while the field is still zero. This procedural step can only be omitted if one of the following two conditions is met: only zero field measurements will be made with monotonically decreasing temperatures or the specimen has a demonstrated magnetic hysteresis of less than 2 % for the magnetic fields to b