Precision signal conditioning and front-end electronics for temperature and field measurements in SST-1 TF magnets

As a part of refurbishment of Steady-state Super-conducting Tokamak-1 (SST-1) at Institute for Plasma Research, India, all sixteen Toroidal Field (TF) magnets of SST-1 have been individually tested in cold with nominal current in a dedicated experimental cryostat. The magnets were cooled down to 4.5 K using either super critical or two phase helium, after which they were charged upto 10 kA of transport current. Precise temperature and field measurements in the experimental configuration were mandatory. Temperatures were required to be measured accurately at several locations in the magnet and hydraulic circuits, where as the field measurements were carried out at few predefined locations on the magnet case. Highly accurate in-house modular signal conditioning electronics had been developed for accurate temperature and field measurements. This paper describes the scheme of the measurement diagnostics, precautions taken for enhanced reliability and long term offset stability in cryogenic environment, and the results of TF magnet tests.