Indigenous development of superconducting magnet for accelerator programme at IUAC, Delhi

Superconducting magnet and cavity are the primary components for the present day powerful particle accelerator. IUAC was primarily engaged on development of bulk niobium quarter wave cavity for their superconducting heavy ion linear accelerator programme. In recent past superconducting magnet programme was initiated with the development of 7 Tesla SC solenoid magnet with bore diameter of 25 mm. and outer diameter of 75 mm. to insert in directly to wide neck (100 mm.) liquid helium dewar. At the same time a joint development of HTS magnet for ECR ion source with M/s Pantechnique, France was successful. In next phase we took a challenging project on development of warm bore 6 Tesla cryofree superconducting magnet with the support from Department of Science and Technology. This kind of cryofree magnet was successfully developed and demonstrated first time in India at IUAC in 2011. The characteristics of hybrid (Copper + HTS + Nb-Ti) current lead, thermal stabilization of magnet with GM cryocooler at different charging rates were studied in detail. These two successful projects motivated us on taking a project on development of ever-cooled superconducting quadrupole magnet with super ferric iron core at 4.2 K for Hybrid Recoil Mass Spectrometer. The geometry and construction was much more complex and challenging considering the cold mass of 1800 kg. and to be ever cooled by using cryocooler. Once it is cooled by liquid helium, the evaporated gas is reliquefied by a cryocooler of capacity of 1.5 W at 4.2 K. First stage refrigeration capacity of cryocooler is used for intermediate copper thermal shield and 2 pairs of HTS lead. This was tested recently and achieved field gradient is 15-20 Tesla/m. with current of 70 A. This magnet developed with the same philosophy of present day MRI is at 4.2 K for last 5 months without refilling. Present talk will be highlighting in details on design issues of these development along with the thermal performances of each type of magnet. (author)