Stability study of Bi-2212 conductor based on perturbation spectrum for hybrid superconducting magnet

Abstract

Summary A hybrid superconducting central solenoid employs Bi‐2212 high‐temperature superconductors and Nb3Sn low‐temperature superconductors under the design of the Institute of Plasma Physics, Chinese Academy Of Science for further upgrade to CFETR, namely, the China Fusion Engineering Testing Reactor. The conductor type of both parts is cable‐in‐conduit conductors. This paper mainly focuses on stability study of the inner high‐temperature superconductors part whose conductor works under a peak magnetic field of 16.79 T, and the maximum operating current of each turn is 50 kA. The simulation based on a 1‐D simplified model is performed using the code THEA (thermal hydraulic and electric analysis of superconducting cable). Firstly, a brief analysis of stability considering the AC loss during current ramp‐up is studied. Then, the stability margins in cases of different perturbations with varied lengths and durations are calculated, and a qualitative explanation of the result is proposed. Besides, the inlet pressure and pressure drop crucially influence the convection heat transfer between strands and helium; thus, the effect of these two factors on stability margin is discussed. All these results will provide important references for further optimization of this hybrid magnet. Copyright © 2017 John Wiley & Sons, Ltd.

Design Study of a 50-kA React-and-Wind Bi-2212 Cable for Fusion Magnet

“…With the above background, it is possible to start the design study of an R&W conductor for the central solenoid of CFETR Phase II, whose design objective is to generate a large magnetic flux in the plasma while keeping the magnet volume as small as possible. A cable that could achieve this goal should have the following characteristics [36]: operating current I op = 50 kA; operating temperature T op =4.5 K (temperature margin > 2 K) and peak magnetic field B max =17 T.; inner radius (R in ) is set at 1 m.…”

“…In Fig. 4, a round Bi-2212 CICC is also shown for comparison [36]. When the Central Solenoid is charged, the magnetic field in vertical direction and the current in circumferential direction result into radial outward force on the cable.…”

“…In the Bi-2212 round conductor (which used a low current wire, comparable to M-wire) for CFTER the stress can be estimated at about 45 MPa [36]. Therefore in flat cables the transverse stress would be about two times lower than in round conductors.…”