SYSTEM Superconducting magnets of fusion machines at 45 K need to guard from external heatin leaks due to radiation and conduction from 300 K surfaces Intermediate thermal shields always have been appreciated to limit the thermal load at 45 K from ID: 1009905
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1. INSTALLATION AND COMMISSIONING OF 80 K LIQUID NITROGEN BOOSTER SYSTEMSuperconducting magnets of fusion machines at 4.5 K need to guard from external heat-in leaks due to radiation and conduction from 300 K surfaces. Intermediate thermal shields always have been appreciated to limit the thermal load at 4.5 K from ambient.In SST-1, 80 K thermal shields houses the superconducting magnets at 4.5 K, vacuum vessel at 323 K and cryostat at 300 K.For cooling the 80 K thermal shields, a single phase sub-cooled liquid nitrogen coolant has been preferred as it is very difficult to handle two-phase flow due the vapour blockage, flow instability, higher pressure drop and difficulty to carry out thermo-hydraulics study.The single phase liquid nitrogen is obtained using 80 K Liquid Nitrogen booster system. Booster system has 20 kW of heat removal capacity from 80 K thermal shields of SST-1 using single phase liquid nitrogen cooling at 7bar (a).Integrated site installation, commissioning and testing of 80 K booster system, wall cryostat and VJ transfer lines have been done successfully at IPR. Automatic operation along with process operation sequence starting from idle, filling liquid, cool down 1st phase, cool down 2nd phase, steady state, self-test and warm up tests were carried out successfully with their associated safety interlocks and system alarms. Booster system performance test was successfully demonstrated with system in-built 23 kW dummy load (heater) and applying 1.8 bar pressure drop across application. Steady state stability on process parameters observed for long hours of system operation.