KSTAR thermal shield

The thermal shield intercepts thermal radiation from the components at room temperature to superconducting magnet at 4.5 K. The thermal shield of KSTAR is divided into three categories: vacuum vessel thermal shield, port thermal shield, and cryostat thermal shield. Tube-on-panel is the basic configuration of KSTAR thermal shield. The layout of the tubing has been designed to get the temperature distribution of 80 K. The shield is designed to be cooled down by flowing gaseous helium at 18 bar in the tube. After the installation, helium leak test was intensively performed to confirm leak tightness of cooling pipes of which length are about 703 and 2544 m for vacuum vessel thermal shield and cryostat thermal shield, respectively. On April 3, 2008, the cool down of the KSTAR started and during the operation the temperature was monitored by PT-100 temperature sensor. This paper describes the overalls of thermal shield work from design to installation, and reports the results of the KSTAR thermal shield during initial operation.