Search

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. [ABSTRACT FROM AUTHOR]

An in-situ measurement of the magnetic field generated by the assembled superconducting magnet coils was held by using precision Hall sensors during the commissioning of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This was done in order to investigate the magnetic influence of Incoloy 908, which is the jacket material for the cable-in-conduit conductors (CICCs) of the Nb3 Sn coils. After the PF coils were discharged from 1 kA the vertical remanent field at the plasma center was more than 10 G, while the TF coils were not energized. The vertical magnetic field generated by the PF coils had a discrepancy of up to 50 G between measurement and the calculation assuming no magnetic influence of Incoloy 908. Thus, non-negligible ferromagnetism was identified and attributed to Incoloy 908. In contrast, most of the hysteresis observed in the magnetic measurements was eliminated when the Incoloy 908 of the TF windings was saturated by the TF coil charging. [ABSTRACT FROM AUTHOR]

To achieve the first plasma of the Korea superconducting tokamak advanced research (KSTAR), the KSTAR superconducting coils were tested in advance. As they should operate in excessively low temperature of 4.5 K and high magnetic field environment of 7.5 T, it is crucial to monitor the cryogenic and the structural behaviors of KSTAR device during the commissioning period including a cool-down. The temperatures of the KSTAR toroidal field (TF) coil and the poloidal field (PF) coils were measured during the entire operating period. The mechanical stresses on the TF and PF structures were continuously monitored to check if they go beyond the limiting value calculated through the simulation. The alignment of the KSTAR device was checked by using displacement sensors. The TF coils were successfully supplied with 15 kA DC current for 8 hours, and the maximum 5 kA/s current variation of the PF coils were tested. For the main experiment, the interlock test of the quench detection system for the KSTAR coils was carried out at reduced currents of 1 kA. From these results the quench protection circuit, and the current-flow of the KSTAR superconducting coils proved to be well performed for the first plasma operation. [ABSTRACT FROM AUTHOR]

The magnet system comprises sixteen toroidal field (TF) coils and fourteen poloidal field (PF) coils for KSTAR (Korea Superconducting Tokamak Advanced Research) Tokamak. All the TF coils and 10 PF coils (PF1~ 5 UL) are made of Nb3 Sn strands and 4 PF coils (PF6 ~ 7 UL) are made of NbTi strands. Before operating the superconducting coils, it is critical to verify the operation conditions such as thermo-hydraulic parameters and stability boundaries. In this regards, the TF model coil and CSMC (Central Solenoid Model Coil) have been tested and the operating conditions have been analyzed. Before cool down, parameters such as helium flow through conduits, electrical insulation and coil geometry have been measured at room temperature to confirm the manufacturing soundness. During cool down and current charging, thermo-hydraulic and mechanical parameters by using mechanical sensors have been measured. Also measured was the magnetic field strength in various positions of the coil conductor. Measured data have been analyzed and the results have been compared with the model analysis by simulation code. [ABSTRACT FROM AUTHOR]