Presentation Information
[WB1-02-INV]The development and heat treatment of Rutherford cables using ultrafine strands
*Ian Pong1, Akihiro Kikuchi2, Najib Cheggour3, Andy Lin1, Jean-Francois Croteau1, Nandana Menon1 (1. Lawrence Berkeley National Laboratory (United States of America), 2. National Institute for Materials Science (Japan), 3. National High Magnetic Field Laboratory, Florida State University (United States of America))
Keywords:
Nb3Sn,ultrafine strands,Rutherford cables
The present state-of-the-art conductor for particle accelerator superconducting magnets is a single-stage “Rutherford” cable made of Nb-Ti or Nb3Sn wires, typically 0.7 to 1.1 mm diameter. A typical high-current Rutherford cable, about 20 mm wide and 2 mm thick, is very stiff and difficult to bend. NIMS, LBNL, and NHMFL have embarked on a project to explore another way to make Rutherford cables analogous to the suspension bridge cable: use ultra-fine filaments that can sustain high loads while remaining flexible. To reduce risk, to improve resource allocation, and have more assured progress, we adopted a phased approach, in which we started with lower cost Cu-alloy wires to gain experience, then moved onto Nb-Ti superconducting wires to guide cabling parameters, and finally Nb3Sn which are more challenging to fabricate as it requires heat treatment and its performance is strain sensitive. In this presentation, we will focus on three cable parameters: planetary twisting, packing factor, and facet size. We will show how these well-established parameters for conventional Rutherford cables will require very different considerations in the novel Rutherford cables made using ultrafine strands. We will also highlight the challenges associated with tension control during cable fabrication. Lastly, we will present some micrographs to discuss the heat treatment and phase development during the reactive diffusion of the superconducting A15 phase.