SUPERCONDUCTOR WITH HIGH NIOBIUM ARCHITECTURE HAS UNEXPECTEDLY GOOD ELECTROMECHANICAL PROPERTIES.

The fabrication of the next generation of particle accelerators for high energy physics will require the development of new niobium-tin/copper superconductors able to carry extremely high current densities at high magnetic fields. One technique for accomplishing this is to push the density of superconductor in the composite wire to new limits. Such an experimental, high-niobium composite was fabricated recently by a private company. A concern in the high-energy-physics community was that the conductor would have very low tolerance to mechanical strain. To test the conductor, NIST scientists modified their axial electromechanical test apparatus and used a new 16.5 T, high field magnet. Surprisingly, the conductor had electromechanical tolerance similar to standard [Nb.sub.3]Sn composites. The irreversible strain, beyond which the conductor shows permanent degradation, had a relatively high value of 0.85 %. The peak critical current was measured at a strain of 0.34 %. This result clears the way for wire manufac turers to push the niobium density to even higher values, which would provide a significant extension of the magnetic field limit of present accelerator magnets.