The main focus of the project is to develop standard techniques for the measurement of critical current of high-temperature and low-temperature superconductors. Some applications for which these types of measurements are crucial include: magnetic-resonance imaging, research magnets, fault-current limiters, magnetic energy storage, motors, generators, transformers, transmission lines, synchronous condensers, high-quality-factor resonant cavities for particle accelerators, and superconducting bearings. One area in which superconductors have the potential for making a significant impact is in fusion energy. Fusion energy is a potential, virtually inexhaustible energy source for the future. It does not produce CO2 and is environmentally cleaner than fission energy. Superconductors are used to generate the ultra-high magnetic fields that confine the plasma in fusion energy research. Physical Measurement Laboratory (PML) staff measure the magnetic hysteresis loss and critical current of marginally stable, high-current Nb3Sn superconductors for fusion and other research magnets.
PML staff have completed the construction and testing of a
variable-temperature and variable-strain, or unified, apparatus for
measuring critical current. The apparatus combines world class capabilities in variable-temperature
and variable-strain measurements and is expected to be the
highest-current apparatus of its type in the world. The new apparatus
will help answer fundamental questions about the performance of strain
sensitive superconductors. Measurements taken on the new apparatus
facilitate the investigation of scaling models.
The top photograph shows the new high-current
apparatus constructed at NIST to measure the critical-current dependence
on strain, temperature and magnetic field. The worm-wheel that torques
the spring can be seen through the small, round window. The lower
photograph shows the CuBe spring with a helical sample
soldered to the spring. Three pairs of voltage taps cover the three
central turns of the spring. The current contacts are made at each end
of the spring.
Lead Organizational Unit:itl
Loren Goodrich and Najib Cheggour (University of Colorado)
Ted Stauffer (PML) and Jack Ekin (PML Guest Researcher)