Speaker
Description
Measuring plant are made on the base of cryostat КГ-60/300-1 in internal cavity of which, in liquid helium medium, solenoid is located, and in its central part insert-holder with sample is located. Power supply of solenoid and tested sample, by current leads located in the upper cover of cryostat, are performed by power supplies of Danfysik - system 8800 company with the help of PC and control program developed in BINP. In order to test the plant for determination of current–voltage characteristics (CVC) in superconductors at helium temperatures, test measurements were carried out according to the method MVI 400-423/8-2018 developed by JSC VNIINM [2]. Measurements were made on composite wire samples based on the Nb-Ti alloy, 0,08 m long and 0,5 and 0,85 mm diameters cut from the wires of standard batches, with CVC being indicated by the manufacturers of these superconductors. He calculated value of the critical current specified by the manufacturer of the measured superconducting wires at the 7 T shall be 200 A and 372 A. The value we have obtained is 212 A and 382 A, which is less than 10% [4] and this corresponds to the limit of the permissible basic absolute error of the meter В7-99 which is ± (1, 5·10-3 + 4, 5·10-5 | U |) mV (U - measured voltage, mV). As can be seen, the operability of the measuring unit for determining the actual critical current values is confirmed, and obtaining a more accurate measurement result will allow modern precision digital measuring equipment, with the permissible basic absolute error of ± 0,0025%+ 0,02 nV.
