SST-1 Magnet System Refurbishment: An Update

Abstract

The Magnet System of the Steady State Superconducting Tokamak (SST-1) has been completely refurbished under the SST-1 Mission. Since Jan 2009, a wide spectrum of refurbishment has been undertaken which, includes developing reliable designs and processes leading to the fabrication of leak tight low DC resistances in SST-1 magnet winding packs, equipping each of the sixteen SST-1 Toroidal Field (TF) magnets with a supercritical helium cooled bubble type thermal shields and testing each of the prepared TF magnets under representative conditions in cold with nominal currents along with manifolds and isolators in near representative conditions. Each of the sixteen SST-1 TF magnets has been tested fully and successfully in a dedicated test stand in nineteen campaigns during June 10, 2010 and was concluded on Jan 24, 2011. These campaigns ensured that all the sixteen TF magnets could be charged to their nominal currents of 10000 A in either two-phase or supercritical cooling conditions with leak-tight inter-double pancake resistances being in the range of 150 pico ohms to 1200 pico ohms. The supercritical helium cooled thermal shields welded in the inner bore of the TF magnets have also performed as per the design specifications. Subsequently, the assemblies of the SST-1 TF magnets and the Poloidal Field (PF) magnets in SST-1 machine shell have begun. The SST-1 TF magnets are being assembled in pairs (known as octants) together with a SST-1 vacuum vessel module, sector of 80 K bubble type thermal shields and a pair of outer-inter-coil-structures. The octant assemblies have been completed. The nine superconducting Poloidal Field (PF) magnets will shortly be assembled being supported from the TF cases. The resistive central solenoid magnets, compensating coils and the newly designed in-vessel radial control coils will be subsequently assembled. The assembled magnets inside the cryostat are expected to be cooled down starting from Jan 2012 when a detailed engineering validation of the magnet system would be undertaken. The detailed SST-1 magnet system refurbishment including some of the first-of-its-kind test results are discussed in this paper