Construction and Commissioning Results of the KSTAR Current Lead System

The KSTAR current lead system (CLS) was commissioned during the first campaign of the plasma experiments. The current lead system is divided into a toroidal field (TF) system and a poloidal field (PF) system. Two pairs of current leads for the TF system and 7 pairs for the PF system were installed. Instead of the copper leads, vapor-cooled type brass current leads (CLs) were mounted in order to minimize the cryogenic load. The CLs were installed after the verification of the components through helium leak tests, low current charging tests at room temperature, and high voltage tests. The stability of the CLS was inspected through LN2 cool down tests, helium leak tests, flow control tests, and temperature control tests using a ceramic heater after the installation all of their components. During the first campaign, it was cool down until liquid helium temperature after vacuum pumping and the helium flow rates of the CLs were controlled successfully at the optimum values. In case of the TF CLs were 0.20 g/s and 0.26 g/s at zero current and 15 kA respectively. On the other hands the PF CLs kept 0.2 g/s during PF coil operation at 4 kA and zero current. And a ceramic heater was reliably operated to prevent water condensation at the warm terminal of the CL.