A Scalable APC Approach to Increase Layer and non-Cu Critial Current in High Field in Nb3Sn Conductors

Period of Performance: 06/08/2015 - 03/07/2016

$150K

Phase 1 SBIR

Recipient Firm

Hyper Tech Research, Inc.
539 Industrial Mile Rd Array
Columbus, OH 43228
Firm POC
Principal Investigator

Abstract

This proposal is submitted in response to the SBIR/STTR High Energy Physics Solicitation Topic 29a). Superconductor Technologies for Particle Accelerators, a) High-Field Superconducting Wire Technologies for Magnets. The need is for strands that operate at a minimum of 12 Tesla T) field, with preference for production scale > 3 km continuous lengths) wire technologies at 15 to 25 T. The strands are preferred to have higher engineering current densities, at least 400 amperes per square millimeter of strand cross-section at the target field of operation and 4.2 K temperature, and have reduced effective filament diameter, in particular to less than 30 micrometers at 1 mm wire diameter, with minimal concomitant reduction of the thermal conductivity of the stabilizer or strand critical density. Hyper Tech has fabricated Nb3Sn strands with our tube approach strand with 200-900 filaments at 0.7 mm OD in kilometer lengths. While the deff sizes and stabilities of these strands are excellent, and the conductor performance is very good at 2500 A/mm2 at 12 T, it would be very useful for HEP applications to push the non-Cu Jc in these strands with high filament counts way beyond the 3000 + A/mm2 -12T level potential for 50% plus improvement based on preliminary data). A promising approach for achieving this is to dramatically increase the layer Jc thereby increasing the overall non-Cu Jc in the strands. To do this, we have focused and found a new way on creating artificial pinning centers within Nb3Sn strands to increase flux pinning while maintaining high Sn content and high fractions of active high quality, current carrying A15) Nb3Sn area in the strand cross section, in order to raise the Jc overall in the 12-20T range. In this Phase I firstly we will focus on developing a strand with enhanced pinning, while not sacrificing Bc2 or area fraction. We will start by fabricating a subelement designed to generate artificial pining centers during the reaction phase so as to increase the layer Jc and non-Cu Jc of the strand. By creating artificial pinning center in the reacted A15 area we will increase the layer Jc of the strand. We will then make restacks of the subelements. Our goal is to achieve strands with increased layer Jcs, and non-Cu Jc in the strand well over 3000 A/mm2 at 4.2 K -12 T, and over 1800A/mm2 at 4.2K - 15T standard Tube type strands have similar layer Jc values to internal-Sin distribute barrier or RRPTM) strands, but lower fractions of fine grain). We will demonstrate and optimize billet lengths that exceed 3km piece lengths at 0.7 and 1.0 mm diameters with subelements of 45 micrometers or less in a proposed follow-on Phase II. The success of this SBIR will lead to a strand that can achieve non-Cu Jc at 12T-4K of over 3000A/mm2 while keeping the deff of range 30-35 m. The idea is to increase the layer Jc values by the use of artificial pinning centers. Using this approach, we can maximize the non-Cu Jc of these Tube type strand designs.