In Tokamaks, high magnetic fields are produced using superconducting (SC) magnet systems. A superconducting magnets system comprises of low temperature superconductor (LTS) based electromagnets, their SC current feeders and current leads.

Normally LTS magnets system are cooled around -267 0C using expensive liquid helium for achieving superconductivity, a near zero loss state. They also require very thin window of temperature for smooth operation and are highly susceptible to quench (transition to normal state from super conducting state). In certain dynamic operational conditions, the SC current feeders system and their joints are even prone to accidents leading to shut down of these large devices for long durations.

In comparison to conventional LTS current feeders system, High Temperature Superconducting (HTS) based current feeders have potential benefits in terms of better temperature margin, less cryo operational cost and better cryo-stability for operating large scale SC magnets. The heat exchanger of the HTS current leads can be cooled using much cheaper liquid nitrogen at around -196 0C instead of expensive liquid helium. As a proof of concept, a prototype 3.3 kA rated HTS current lead with MgB2 (magnesium diboride, superconducting near -234 0C) wires as intermediate joints between bottom HTS module (ceramic based HTS tapes, superconducting near -183 0C) and NbTi (niobium-titanium alloy) shunt is recently tested.

The HTS current leads and its bottom MgB2 –Cu–NbTi shunt are tested in cold conditions up to 1.5 kA in a dedicated experimental test set-up having precise instrumentation and diagnostics. The test results of prototype current leads are being analysed for detailed understanding. As a next step, we have replaced MgB2 –NbTi shunt with a meter long complete MgB2 shunt between HTS current leads pair for overcoming the issues for operation of current leads up to the rated current of 3.3kA. These developments could provide cost effective solution for future large scale applications.

Development of Wall Helium Cooling System (FWHCS) At IPR

KN Vyas (Chairman Atomic Energy Commission and Secretary, Department of Atomic Energy) inaugurated the Experimental Helium Cooling Loop (EHCL) as well as the Neutronics Laboratories in the Institute of Plasma Research (IPR) main campus.

Helium is an attractive coolant for fusion power plant applications. An Experimental Helium Cooling Loop (EHCL) facility has been successfully installed and commissioned at IPR. It is a scaled down system of First Wall Helium Cooling System (FWHCS) of a fusion blanket module. The major components of this loop are: circulators, heater, recuperator, coolers, compressors and Test Section etc. Helium pressure and inventory in the loop is maintained by Pressure and Inventory System (PICS). This system will be integrated with the High Heat Flux Test Facility (HHFTF) to provide helium as a coolant during high heat flux testing.

Neutron & Ion Irradiation Facility is an accelerator-based 14-MeV D-T neutron source with a design yield of 5x1012 n/s. A Deuterium ion beam produced from a 2.45 GHz ECR source is accelerated by a 300 kV high voltage power supply and impinged on a Titanium Tritide (TiT) thin-film target. A neutron yield of 7 × 1011 n/s has been achieved in early testing.

The NIIF is equipped with various neutron diagnostics system i.e. foil activation, diamond detector, associated alpha particle detector, and He-3 detector to measure the neutron yield. It is also equipped with state of the art tritium handling & recovery system to recover tritium sputter/outgassing during bombardment of the deuterium beam on the tritium target.

The AERB has already accorded Commissioning Approval for the facility. The 14 MeV neutrons generated in NIIF will be used to study irradiation effects on various functional and structural materials used in fusion blankets. This facility will also be utilized for benchmark experiments in a variety of areas, like double differential cross-section, neutron spectroscopy, Fusion Evaluated Nuclear Data (FENDL), neutron imaging, medical isotope production, neutron diagnostic development, etc.