Design, fabrication and cryogenic testing of 0.6 MJ SMES coil

Abstract Our centre has taken up a project of development of superconducting magnetic energy storage (SMES) technology to have better power quality for its accelerator program. In the first phase, a prototype cryostable coil has been designed, fabricated and commissioned in a standard bath cryostat. The various parameters of the magnet coil have been determined in order to maximize stored energy taking into consideration the constraints like geometry, maximum current limit etc. Winding tension (Pre-stress) of 13.6 MPa is maintained to keep radial stress compressive in all possible scenarios (i.e. during cool-down, excitation, etc.). Mylar is used for turn to turn insulation while 1 mm thick glass epoxy based picket fences (G-10) are placed symmetrically azimuthally for layer to layer insulation as well as to ensure passage of liquid helium inside the winding. Cryostability of the conductor implies more copper to superconductor ratio and is desired as far as stability of the coil is concerned. Cryostability, however may degrade when helium vapor is trapped in between two layers. Therefore, quench behavior of the magnet along with protection system has also been studied and implemented. This paper describes issues related to design study, fabrication and also cryogenic test results of the coil.