Speaker
Description
In a REBCO no-insulation (NI) magnet coil, the turn-to-turn contact resistance (Rc) determines the coil’s quench self-protection ability, charging delay time and the energy loss during field ramp. Therefore it is critical to control Rc to suitable values. In our previous investigation, we measured Rc at 77 K and 4.2 K under various contact pressures and pressure cycles, and studied the effect of surface coating on Rc. Based on our experiment on short stamp samples, we found a reliable technique to control Rc by oxidizing the surface of the copper stabilizer of REBCO tapes.
In this paper, we developed a prototype reel-to-reel REBCO oxidation system to demonstrate the ability to control Rc of long lengths REBCO conductor. We will present the technical details of the process. The effect of various process parameters will be discussed. In addition, we developed a method of controlling contact resistivity of a REBCO coil by using co-wind stainless steel tapes. In this case, the control of contact resistance is done, also in reel-to-reel fashion, by treating the surface of stainless steel tape. The result of REBCO coil made by these Rc control methods will be presented. Since the understanding of the surface chemical/mechanical process in contact resistivity control is the key to obtain reliable controllable Rc, surface chemistry of both oxidized REBCO and the stainless steel tape is also studied.
Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and DMR-1839796, and the State of Florida.
