Design and fabrication of the KSTAR in-vessel cryo-pump

Abstract

In-vessel cryo-pump (IVCP) of the Korea Superconducting Tokamak Advanced Research (KSTAR) has been designed, fabricated, and installed in the vacuum vessel for effective particle control by pumping through a divertor gap. For the final engineering design of the IVCP supports to withstand all external forces, a structure analyses were performed for two cases. The first is the thermal stress due to cool-down from room temperature to operating temperature (cryo-panel: 4.4 K, thermal shield: 77 K), and the other is the electro-magnetic stress due to the induced eddy currents during plasma disruptions. When the plasma disrupts, the maximum stress and displacement on the supports were estimated to be 849 MPa and 5.36 mm, respectively. These results were taken into account in the support design. The IVCP system was fabricated in two half-sectors and a pre-assembling test was successfully completed in the factory. Final installation of the IVCP in the vacuum vessel was fulfilled in parallel with a pressurization test (thermal shield: 30 bar, cryo-panel: 10 bar), a helium leak test, and a thermal shock test using liquid nitrogen. As a result, the IVCP system was successfully installed in the vacuum vessel.