Thermohydraulic Behaviors of KSTAR PF Superconducting Magnet System in Operation
Korea Superconducting Tokamak Advanced Research (KSTAR) is a superconducting tokamak which adopts and NbTi as superconductors and it has been operated since 2008. One of main issues is the performance of superconducting magnet system in the real operation. In view of this issue, the KSTAR magnet system shows the sufficient operational capability through the whole campaigns. For example, we have already achieved the maximum Toroidal Field (TF) current and the bipolar pulsed Poloidal Field (PF) operation up to ± 10 kA. It is very important to operate stably the full superconducting magnet system such as KSTAR and ITER. Each KSTAR magnet consists of Cable-In-Conduit Conductors (CICC) cooled by forced flow of the supercritical helium in cryogenic temperature. The temperature, pressure and mass flow rate of coolant are interacted organically inside of CICC and the behaviors are also complicated during operation. The pressure drop between inlet and outlet of coil, the temperature increasing in accordance with coil current variation, and so on are critical issues related with the flexibility and reliability of superconducting tokamak. Most of all, we agree that the analysis of thermohydraulic behavior is absolutely needed for more stable operation and higher plasma performance. So we are checking the related data and the tendency at every campaign and we are optimizing the operational procedure to fit the plasma scenario. In this paper, we introduce the significant thermohydraulic behaviors of KSTAR PF coils up to now.
Effect of electromagnetic force on the pressure drop and coupling loss of a cable-in-conduit conductor
In the central solenoid (CS) insert experiment performed with the International Thermonuclear Experimental Reactor CS model coil, significant changes in the pressure drop and coupling losses were observed during coil energization. This phenomenon was quantitatively analyzed from the viewpoint of the deformation of the cable shape in the CS insert conductor due to an electromagnetic force acting on the cable. A new calculation model was proposed to provide the relation between the electromagnetic force and hydraulic characteristics of the conductor. Calculation results indicated that there seemed to be a gap of 1.3 mm between the cable and jacket created by the electromagnetic force when the CS insert was operated at 40 kA and 10 T, which can cause the decrease of the pressure drop by 12% and also the decrease of the local void fraction of the cable from 36.3% to approximately 34%. The latter well explained the increase of coupling losses. A local void fraction of 34.5% is suggested from the calculation in order both to reduce the amount of deformation and to maintain the coupling losses at acceptable level for this type of large current-carrying conductor.
On a New Subclass of p-Valent Close-to-Convex Mappings Defined by Two-Sided Inequality
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