Design of high field tool coil for magnetic pulse welding

The Accelerator and Pulse Power Division (APPD), BARC has developed strong Bitter coil with field shaper and 70 kJ, 25 kV electromagnetic manufacturing machine, for forming and welding applications. They conducted investigations into possibility of using Electromagnetic Pulsed Technology (EMPT) in joining austenitic –austenitic stainless steels, using samples fabricated to simulate tube and caps with coil developed at laboratory. The coil has been designed for industrial mass production that consists of four numbers of copper discs axially reinforced with non-magnetic steel studs. The polyamide films are used as coil and stud liner whereas Fibre Reinforced Plastic (FRP) is used as inter disc insulation. This paper discusses the design details of the 20kV, 250kA, 10 kHz Bitter coil, field shaper with replaceable inserts. This designed coil has been regularly used at rated value and generating the field of 35-40T in volume of Ø8.8mmX13mm. The steel tube to plug joints developed by this tool qualified helium leak better than 1.2x10^-9 mBar.litre.s^-1 and parent tube failed under pull out test but joint was intact.