Key Features in the Operation of KSTAR

Abstract

The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb 3 Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb 3 Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350 • C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ ∼ 1.8, δ > 0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B T = 2 T with I p = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.Index Terms-Incoloy, in-vessel control coils (IVCC), Korea superconducting tokamak advanced research (KSTAR), superconducting.

Polarimetric spectra analysis for tokamak pitch angle measurements

“…One of the main research missions of KSTAR along the path to the commercialization of the fusion energy is to develop and exploit the steady-state and advanced operation scenarios. In these scenarios the information on the current density profiles is critical to assess the external current drive into the plasma and the bootstrap current formed near the edge pedestal during highconfinement modes of operation [5]. Therefore, current profile measurements for both the core and edge region of the plasma should be made.…”

Acceleration optimization of real-time equilibrium reconstruction for HL-2A tokamak discharge control

“…Its algorithm is computationally intensive such that it cannot be used directly for real-time discharge control. To compute discharge parameters in real time rapidly enough for tokamak feedback control, simpler algorithms implemented at most tokamak facilities [3][4][5][6][7][8][9][10][11] approximate the results of the full equilibrium reconstruction. For example, the P-EFIT has been used on EAST, which can complete a magnetic equilibrium reconstruction iteration in 300 μs with 65×65 grids.…”

Fast equilibrium reconstruction for tokamak discharge control based on GPU

“…In [4], a real-time version of EFIT is described through modifying some algorithms and it could provide a converged equilibrium result in about 30 ms with a 33 × 33 grid. The real-time-EFIT (RT-EFIT) [5] is another real-time version of EFIT which is currently used by DIII-D, KSTAR, NSTX, MAST and EAST [5][6][7][8][9]. The RT-EFIT code made many simplifications and the spatial resolution is relatively low compared with the off-line EFIT.…”