ASTM B714-82(1997)e1

Standard Test Method for D-C Critical Current of Composite Superconductors (Withdrawn 2001)

SCOPE
1.1 This test method covers the procedure for the determination of the d-c critical current of composite superconductors.  
1.2 This method is intended for use with superconductors having a critical current of less than 600 A under test conditions and at magnetic fields of less than 0.8 of the upper critical magnetic field.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 6.

General Information

• Status: Withdrawn
• Publication Date: 31-Dec-1996
• Withdrawal Date: 09-Mar-2001
• ICS: 29.050 - Superconductivity and conducting materials
• Technical Committee: B01 - Electrical Conductors

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn. Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: B 714 – 82 (Reapproved 1997)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
D-C Critical Current of Composite Superconductors
This standard is issued under the fixed designation B 714; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made throughout in March 1997.
1. Scope 5.2 Results obtained from this method can also be used for
detecting changes in the superconducting properties of a
1.1 This test method covers the procedure for the determi-
composite superconductor due to processing variables, han-
nation of the d-c critical current of composite superconductors.
dling, aging, or other application or environmental conditions.
1.2 This method is intended for use with superconductors
This method is useful for quality control, acceptance, or
having a critical current of less than 600 A under test conditions
research testing if the precautions below are observed.
and at magnetic fields of less than 0.8 of the upper critical
5.3 The critical current of composite superconductors de-
magnetic field.
pends on many variables. These variables need to be consid-
1.3 This standard does not purport to address all of the
ered in both the testing and the application of these materials
safety concerns, if any, associated with its use. It is the
(1).
responsibility of the user of this standard to establish appro-
5.3.1 Test conditions such as magnetic field, temperature
priate safety and health practices and determine the applica-
and relative orientation of specimen, current and magnetic field
bility of regulatory limitations prior to use. Specific hazard
are determined by the particular application.
statements are given in Section 6.
5.3.2 The test configuration may be determined by the
2. Referenced Documents particular conductor through the tolerances required by 8.1 and
8.4.
2.1 ASTM Standards:
5.3.3 The specific critical current criterion may be deter-
B 713 Terminology Relating to Superconductors
mined by the particular application.
3. Terminology
5.3.4 It may be appropriate to measure a number of test
specimens if there are irregularities in testing.
3.1 Refer to Terminology B 713 for general terminology for
5.4 A precaution is needed in the interpretation of results
the field of superconductivity.
when the reference line of the V-I curve (8.5, 8.5.1) has a finite
4. Summary of Test Method
slope. The current transfer correction is to be used to correct for
a true current transfer. Voltages may occur from other sources.
4.1 A direct current is applied to the superconductor speci-
5.4.1 A current transfer voltage will result from having a
men and the voltage generated along a section of the specimen
voltage tap near (near is determined by resistivity of the matrix
is measured. The current is increased from zero and the
and electrical field criterion) to a current contact, or having a
voltage-current characteristic is generated. The critical current
gradient in the magnetic field near the region between voltage
is defined as the current at which a specified electric field is
taps, or having a field-sample orientation change near the
exceeded in the specimen.
region between voltage taps (1, 2, 3).
5. Significance and Use
6. Hazards
5.1 The critical currends of composite superconductors are
used to establish design limits for applications of supercon- 6.1 Very large direct currents with very low voltages do not
necessarily provide a direct personal hazard, but accidental
ducting wires. The operating conditions of superconductors in
these applications determine much of their behavior and tests shorting of the leads with another conductor, such as tools or
transfer lines, can release significant amounts of energy and
made with this method may be used to provide part of the
information needed to determine the suitability of a specific cause arcs or burns. Care must be taken to isolate and protect
current leads from shorting. Also the stored energy in super-
superconductor.
conducting magnets commonly used for the background mag-
netic field can cause similar large current pulses or deposit
This test method is under the jurisdiction of ASTM Committee B-1 on
Electrical Conductors and is the direct responsibility of Subcommittee B01.08 on
Superconductors.
Current edition approved Dec. 31, 1982. Published February 1983. The boldface numbers in parentheses refer to the list of references at the end of
Annual Book of ASTM Standards, Vol 02.03. this test method.
B 714
large amounts of thermal energy in the cryogenic systems
causing rapid boil off or even explosive conditions.
6.2 The use of cryogenic liquids is essential to cool the
superconductors to allow transition into the superconducting
state. Direct contact with cold liquid transfer lines, storage
Dewars, or apparatus components can cause immediate freez-
ing, as can direct contact with a spilled cryogen. Normal safety
precautions for the handling of cryogenic liquids must be
observed.
7. Test Specimen
7.1 The test procedure is intended for specimens with a
critical current of less than 600 A under test conditions.
7.2 There shall be no joints or splices in the test specimen
unless otherwise specified.
7.3 The test specimen should, wherever possible, have the
NOTE 1—The reference line described in 8.6 is shown as the dashed line
in Fig. 1 (b).
same residual strain state as the final product.
FIG. 1 Schematic Representation of the Composite
Superconductor’s V-I Characteristic in Two Regions: (1) Intrinsic
8. Procedure
Characteristic Showing the Usual Resistive Transition as I
8.1 The (maximum) bending strain, induced during mount- Approaches I and (2) Current-Transfer Characteristic Exhibiting
c
a Linear Region at Low Current
ing of the specimen, shall not exceed 0.1 % for Nb Sn (and
other brittle materials) or 2 % for Nb-Ti (and other ductile
materials). The tensile strain, induced by the differential
of I requires that the voltage of the reference line at I must be
c c
thermal contraction of the specimen and holder, shall not
less than LE .
c
exceed 0.05 % for Nb Sn (and other brittle material) and 0.5 %
for Nb-Ti (and other ductile material) (4). 9. Report
8.1.1 Pre-reaction forming of brittle conductors to the test
9.1 Identification of test specimen should be made by the
configuration may be required.
manufacturer’s lot number. This number should ensure unique
8.1.2 Matching the thermal contraction of the specimen and
identification. Subsequent processing not identified by the lot
specimen holder may be required (5). Suitable materials for
number should be reported.
construction of the specimen holder are NEMA G-10 and G-11
9.2 The following test conditions shall be reported:
with the specimen in the plane of the fabric (6).
9.2.1 Test magnetic field,
8.2 Solder voltage taps to the specimen in accordance with
9.2.2 Test temperature,
the limits in 8.1, 8.3, and 10.7.2.
9.2.3 Length betw
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