Magnetic and mechanical analysis of Bi-2212 Rutherford cable in a cos-theta sub-scale dipole coil ^*

Abstract The U.S. Magnet Development Program (US-MDP) explores high-field accelerator magnets compatible with operational conditions beyond the limits of Nb 3 Sn technology. The ongoing R&amp;D High-Temperature Superconductors (HTS) suggests using Bi 2 Sr 2 CaCu 2 O <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mn>8</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:mtext> </mml:mtext> </mml:mrow> </mml:math> (Bi-2212) as superconducting element. Bi-2212 Rutherford cables maintain a high critical current ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>I</mml:mi> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">C</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) when exposed to a large external magnetic field. However, Bi-2212 exhibits an oversensitive stress–strain response when subject to large Lorentz forces. This paper reports on the magnetic and mechanical analysis of the Bi-2212 cosine-theta insert being developed at Fermilab for a hybrid magnet composed of two external layers of Nb 3 Sn and two internal layers of Bi-2212. We performed a FEM analysis of the insert to estimate the HTS stress state in the coil’s strands under magnetic and mechanical loads.